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Sustaining the Earth
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Sustaining the Earth TENTH EDITION
G. TYLER MILLER, JR. SCOTT E. SPOOLMAN
Australia • Brazil • Japan • Korea • Mexico • Singapore • Spain • United Kingdom • United States
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Sustaining the Earth, 10e G. Tyler Miller, Jr. and Scott E. Spoolman Life Sciences Publisher: Yolanda Cossio Development Editor: Christopher Delgado Assistant Editor: Alexis Glubka Editorial Assistant: Jing Hu
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Printed in the United States of America 1 2 3 4 5 6 7 14 13 12 11 10
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Brief Contents
Detailed Contents
vii
Preface for Instructors xi Learning Skills 1
SUSTAINING NATURAL RESOURCES 7
Food, Soil, and Pest Management 131
8
Water Resources and Water Pollution 155
9
Nonrenewable Energy Resources 187
10
HUMANS AND SUSTAINABILITY: AN OVERVIEW 1
Environmental Problems, Their Causes, and Sustainability 5
SCIENCE, ECOLOGICAL PRINCIPLES, AND SUSTAINABILITY
Energy Efficiency and Renewable Energy 205
SUSTAINING ENVIRONMENTAL QUALITY 11
Environmental Hazards and Human Health 226
12
Air Pollution, Climate Change, and Ozone Depletion 243
13
Urbanization and Solid and Hazardous Waste 275
2
Science, Matter, Energy, and Systems 21
SUSTAINING HUMAN SOCIETIES
3
Biodiversity and Evolution 49
14
4
Community Ecology, Population Ecology, and the Human Population 67
Economics, Politics, Worldviews, and Sustainability 302
Appendix
SUSTAINING BIODIVERSITY 5
Sustaining Biodiversity: The Species Approach 92
6
Sustaining Biodiversity: The Ecosystem Approach 110
Units of Measurement A1
Glossary G1 Index
I1
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About the Cover Photo
The cover photo shows a Pacific sea nettle found in the Pacific Ocean, mostly near the west coast of North America, running from California to Alaska. It is one of more than 1,500 known species of jellyfish, which are found in every ocean from the surface to the deep sea. Jellyfish existed before the dinosaurs, but they are not fish. They have no brain, head, heart, eyes, or bones and are basically a big bundle of nerves that can detect warmth, odors, and vibration. A jellyfish’s body is usually bell-shaped and filled with a jelly-like substance. It uses the tentacles that dangle from its body to sting or stun a prey animal and to draw food into its mouth. These tentacles also help a jellyfish to defend itself from predators such as other jellyfish, tuna, sharks, swordfish, and sea turtles. Most jellyfish feed on small fish, fish eggs, zooplankton, and other jellyfish. Jellyfish can be as small as a human thumbnail and as large as a tree. The largest species is the Arctic lion’s mane jellyfish, which can have a diameter of up to 2.5 meters (8 feet) and tentacles as long as 37 meters (120 feet)—a length equivalent to the height of a twelve-story building. It can weigh over 250 kilograms (550 pounds). Some jellyfish sting humans and their sting usually causes light burning pain for several days. However, a sting from any of the jellyfish species known as the Portuguese man-of-war, the Australian box jellyfish, and the tiny Irukandji jellyfish can kill a human within several minutes. Jellyfish are often found in large swarms, or blooms, of thousands or even millions of individuals. These blooms have been growing in recent years. Some marine scientists say that a sharp increase in a jellyfish population can indicate that its marine ecosystem has been stressed by human-related factors such as warmer seas caused by global climate change, overfishing of the fishes that eat jellyfish, and inputs of excess plant nutrients from agricultural and urban runoff. As the jellyfish grow in numbers, they eat more fish eggs and young fishes, which can further disrupt a marine ecosystem. It is possible that someday, many marine ecosystems will be dominated by huge populations of jellyfish.
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This is an electronic version of the print textbook. Due to electronic rights restrictions, some third party content may be suppressed. Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. The publisher reserves the right to remove content from this title at any time if subsequent rights restrictions require it. For valuable information on pricing, previous editions, changes to current editions, and alternate formats, please visit www.cengage.com/highered to search by ISBN#, author, title, or keyword for materials in your areas of interest.
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Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Detailed Contents
Learning Skills 1
HUMANS AND SUSTAINABILITY: AN OVERVIEW
1
What Happens to Energy in an Ecosystem? 37
2-7
What Happens to Matter in an Ecosystem? 40
3
Biodiversity and Evolution
3-1
Environmental Problems, Their Causes, and Sustainability 5 What Are Three Principles of Sustainability? 6
1-2
How Are Our Ecological Footprints Affecting the Earth? 10
1-3
Why Do We Have Environmental Problems? 15
1-4
What Is an Environmentally Sustainable Society? 18
SCIENCE, ECOLOGICAL PRINCIPLES, AND SUSTAINABILITY
Science, Matter, Energy, and Systems 21
SCIEN CE FOCU S Earth Is Just Right for Life
3-3 13
3-4
What Are Biomes and How Have Human Activities Affected Them? 56
3-5
What Are Aquatic Life Zones and How Have Human Activities Affected Them? 60
4
Community Ecology, Population Ecology, and the Human Population 67
4-1
What Roles Do Species Play in Ecosystems? 68
KEY QUESTIONS AND CONCEPTS 67
CA SE STU D Y Cockroaches: Nature’s
Ultimate Survivors 68
What Do Scientists Do? 22 What Is Matter and What Happens When It Undergoes Change? 25
How Do Speciation, Extinction, and Human Activities Affect Biodiversity? 54 SCIEN CE FOCU S Changing the Genetic Traits of Populations 56
CA SE STU D Y Why Are Amphibians Vanishing?
S C IE NC E FOC US Statistics and Probability 24
2-2
Where Do Species Come From? 51 to Thrive 54
KEY QUESTIONS AND CONCEPTS 21
2-1
What Is Biodiversity and Why Is It Important? 50 IN D IV ID U A LS MATTER Edward O. Wilson: A Champion of Biodiversity 51
3-2
1-1
C AS E S T UDY China’s New Affluent Consumers
49
KEY QUESTIONS AND CONCEPTS 49
KEY QUESTIONS AND CONCEPTS 5
2
2-6
CA SE STU D Y Why Should We Protect Sharks?
4-2
How Do Species Interact? 72 How Do Communities and Ecosystems Respond to Changing Environmental Conditions? 74
2-3
What Is Energy and What Happens When It Undergoes Change? 29
4-3
2-4
What Keeps Us and Other Organisms Alive? 31
4-4
What Limits the Growth of Populations?
4-5
What Factors Influence the Size of the Human Population? 79
S C IE NC E FOC US Have You Thanked the Insects Today? 32
2-5
69 71
76
CA SE STU D Y The U.S. Population Is
What Are the Major Components of an Ecosystem? 34
Growing Rapidly 80
S C IE NC E FOC US Many of the World’s Most
A Nation of Immigrants 82
Important Organisms Are Invisible to Us 36
CA SE STU D Y The American Baby Boom
CA SE STU D Y The United States:
84
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4-6
CA SE STU D Y The Blackfoot Challenge—Reconciliation
How Can We Slow Human Population Growth? 86
Ecology in Action 124
C AS E S T UDY Slowing Population Growth
6-5
How Can We Protect and Sustain Marine Biodiversity? 125
6-6
How Should We Protect and Sustain Freshwater Biodiversity? 127
in China: The One-Child Policy 88 C AS E S T UDY Slowing Population Growth in India
89
CA SE STU D Y Can the Great Lakes Survive
Repeated Invasions by Alien Species? 128
SUSTAINING BIODIVERSITY
5
6-7
Sustaining Biodiversity: The Species Approach 92 SUSTAINING NATURAL RESOURCES
KEY QUESTIONS AND CONCEPTS 92
5-1
What Should Be Our Priorities for Sustaining Terrestrial and Aquatic Biodiversity 128
What Are the Trends in Species Extinction? 93 C AS E S T UDY The Passenger Pigeon:
7
Food, Soil, and Pest Management 131
Gone Forever 93 S C IE NC E FOC US Estimating Extinction Rates
96
KEY QUESTIONS AND CONCEPTS 131
5-2
Why Should We Care about the Rising Rate of Species Extinction? 97
7-1
What is Food Security and Why Is It Difficult to Attain? 132
5-3
How Do Humans Accelerate Species Extinction? 98
7-2
How Is Food Produced? 133
C AS E S T UDY Snakes in the Everglades
CA SE STU D Y Industrialized Food Production
102
C AS E S T UDY Polar Bears and Climate Change
in the United States 135 103
C AS E S T UDY A Disturbing Message from
the Birds 104
5-4
How Can We Protect Wild Species from Extinction Resulting from Our Activities? 105
SCIEN CE FOCU S Soil Is the Base of Life on Land
7-3
What Environmental Problems Arise from Food Production? 138
7-4
How Can We Protect Crops from Pests More Sustainably? 143
S C IE NC E FOC US Examining the Record of the Endangered Species Act 107
IN D IV ID U A LS MATTER Rachel Carson
136
144
SCIEN CE FOCU S Pesticides Do Not Always Reduce Crop Losses 146
6
Sustaining Biodiversity: The Ecosystem Approach 110
7-5
CA SE STU D Y Organic Agriculture Is on the Rise
KEY QUESTIONS AND CONCEPTS 110
6-1
How Can We Improve Food Security and Produce Food More Sustainably? 148
What Are the Major Threats to Forest Ecosystems 111
8
Water Resources and Water Pollution 155
8-1
Will We Have Enough Useable Water? 156
C AS E S T UDY Many Cleared Forests in the
151
United States Have Grown Back 113
6-2
6-3
KEY QUESTIONS AND CONCEPTS 155
How Should We Manage and Sustain Forests? 115 INDIVIDUALS MAT T E R Wangari Maathai and the Green Belt Movement 117
CA SE STU D Y Freshwater Resources in
How Should We Manage and Sustain Parks and Nature Reserves? 118
SCIEN CE FOCU S Water Footprints and Virtual Water 159
C AS E S T UDY Stresses on U.S. Public Parks
CA SE STU D Y Water Conflicts in the Middle East:
the United States 157
118
S C IE NC E FOC US Reintroducing the Gray Wolf
A Preview of the Future? 160
8-2
How Can We Increase Water Supplies? 161
Conservation Leader 120
8-3
How Can We Use Water More Sustainably? 165
C AS E S T UDY Controversy over Wilderness
8-4
How Can We Reduce the Threat of Flooding? 169
to Yellowstone National Park 119
CA SE STU D Y The Aral Sea Disaster
C AS E S T UDY Costa Rica—A Global
Protection in the United States 121
6-4
What Is the Ecosystem Approach to Sustaining Terrestrial Biodiversity? 122 S C IE NC E FOC US A Biodiversity Hotspot
in East Africa 123
164
CA SE STU D Y Living Dangerously on Floodplains
in Bangladesh 170
8-5
What Are the Causes and Effects of Water Pollution? 171
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8-6
C AS E S T UDY Pollution in the Great Lakes
8-7
CA SE STU D Y Is Ethanol the Answer?
What Are the Major Water Pollution Problems in Streams and Lakes? 172 174
8-8
10-7 What Are the Advantages and Disadvantages of Using Hydrogen as an Energy Source? 220
What Are the Major Pollution Problems Affecting Groundwater and Other Drinking Water Sources? 175 C AS E S T UDY Is Bottled Water a Good Option?
218
10-6 What Are the Advantages and Disadvantages of Using Geothermal Energy? 219
177
10-8 How Can We Make a Transition to a More Sustainable Energy Future? 221
What Are the Major Water Pollution Problems Affecting Oceans? 178 C AS E S T UDY Chesapeake Bay—An Estuary
SUSTAINING ENVIRONMENTAL QUALITY
in Trouble 179
8-9
How Can We Best Deal with Water Pollution? 180 C AS E S T UDY U.S. Experience with Reducing
Point-Source Pollution 181
KEY QUESTIONS AND CONCEPTS 226
S C IE NC E FOC US Treating Sewage by Working
with Nature 183
9
11 Environmental Hazards and Human Health 226 11-1 What Major Health Hazards Do We Face? 227 11-2 What Types of Biological Hazards Do We Face? 227
Nonrenewable Energy Resources 187
CA SE STU D Y The Growing Global Threat
from Tuberculosis 228
KEY QUESTIONS AND CONCEPTS 187
SCIEN CE FOCU S Genetic Resistance to Antibiotics Is Increasing 229
9-1
What Is Net Energy and Why Is It Important? 188
CA SE STU D Y The Global HIV/AIDS Epidemic
9-2
What Are the Advantages and Disadvantages of Using Oil? 189 S C IE NC E FOC US Net Energy is The Only Energy
That Really Counts 190
230
CA SE STU D Y Malaria—The Spread of a Deadly
Parasite
230
11-3 What Types of Chemical Hazards Do We Face? 233 SCIEN CE FOCU S Mercury’s Toxic Effects
233
9-3
What Are the Advantages and Disadvantages of Using Natural Gas? 193
11-4 How Can We Evaluate Chemical Hazards? 234
9-4
What Are the Advantages and Disadvantages of Using Coal? 194
11-5 How Do We Perceive Risks and How Can We Avoid the Worst of Them? 237
C AS E S T UDY The Problem of Coal Ash
9-5
196
What Are the Advantages and Disadvantages of Using Nuclear Energy? 197 C AS E S T UDY Chernobyl: The World’s Worst
Nuclear Power Plant Accident 200 C AS E S T UDY High-Level Radioactive Wastes
in the United States 201
10 Energy Efficiency and Renewable Energy 205 KEY QUESTIONS AND CONCEPTS 205
10-1 Why Is Energy Efficiency an Important Energy Resource? 206 S C IE NC E FOC US Saving Energy and Money
with a Smarter Electrical Grid 207
10-2 What are the Advantages and Disadvantages of Using Solar Energy? 211 10-3 What Are the Advantages and Disadvantages of Using Hydropower? 214 10-4 What Are the Advantages and Disadvantages of Using Wind Power? 215 10-5 What Are the Advantages and Disadvantages of Using Biomass as an Energy Source? 217
CA SE STU D Y Death from Smoking
238
12 Air Pollution, Climate Change, and Ozone Depletion 243 KEY QUESTIONS AND CONCEPTS 243
12-1 What Is the Nature of the Atmosphere? 244 12-2 What Are the Major Outdoor Air Pollution Problems? 246 12-3 What Is Acid Deposition and Why Is It a Problem? 249 12-4 What Are the Major Indoor Pollution Problems? 251 CA SE STU D Y Radioactive Radon Gas
252
12-5 How Should We Deal with Air Pollution? 254 CA SE STU D Y Lead Can Be a Highly Toxic
Pollutant
254
CA SE STU D Y U.S. Air Pollution Laws Could
Be Improved 254
12-6 In The Future, How Might the Earth’s Temperature and Climate Change, and With What Effects? 258 SCIEN CE FOCU S How Valid Are IPCC
Conclusions?
260
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INDIVIDUALS MAT T E R Sounding the Alarm—James
Hansen
SUSTAINING HUMAN SOCIETIES
261
12-7 What Can We Do to Slow Projected Climate Change? 265
14 Economics, Politics, Worldviews, and Sustainability 302
S C IE NC E FOC US Is Capturing and Storing CO2
the Answer? 267
KEY QUESTIONS AND CONCEPTS 302
12-8 How Have We Depleted Ozone in the Stratosphere and What Can We Do about It? 269
14-1 How Are Economic Systems Related to the Biosphere? 303 14-2 How Can We Use Economic Tools to Deal with Environmental Problems? 305
INDIVIDUALS MAT T E R Sherwood Rowland and
Mario Molina—A Scientific Story of Expertise, Courage, and Persistence 270 S C IE NC E FOC US Skin Cancer
IN D IV ID U A LS MATTER Ray Anderson
14-3 How Can Reducing Poverty Help Us Deal with Environmental Problems? 308
272
CA SE STU D Y Muhammad Yunas and Microloans
13 Urbanization and Solid and Hazardous Waste 275
for the Poor 309
14-4 How Can We Make the Transition to More Environmentally Sustainable Economies? 310
KEY QUESTIONS AND CONCEPTS 275
14-5 What is Environmental Policy and How Is It Made? 312
13-1 What Are the Major Population Trends and Problems in Urban Areas? 276 C AS E S T UDY Urbanization in the United States C AS E S T UDY Mexico City
308
277
280
CA SE STU D Y Managing Public Lands in the
United States—Politics in Action 313 CA SE STU D Y U.S. Environmental Laws and
13-2 How Does Transportation Affect Urban Environmental Impacts? 281
Regulations Have Been under Attack 316 SCIEN CE FOCU S Logging in U.S. National Forests Is Controversial 317
13-3 How Can Cities Become More Sustainable and Livable? 283 C AS E S T UDY Curitiba Strives to Be an Ecocity
IN D IV ID U A LS MATTER Diane Wilson
284
13-4 What Are Solid Waste and Hazardous Waste, and Why Are They Problems? 285 C AS E S T UDY Solid Waste in the United States
285
13-5 How Should We Deal with Solid Waste? 287
318
IN D IV ID U A LS MATTER Butterfly in
a Redwood Tree 319
14-6 How Can We Improve Global Environmental Security? 320
C AS E S T UDY We Can Use Refillable Containers
14-7 What Are Some Major Environmental Worldviews? 322
and Other Items 288
14-8 How Can We Live More Sustainably? 323
C AS E S T UDY Recycling Plastics S C IE NC E FOC US Bioplastics
290
290
13-6 How Should We Deal with Hazardous Waste? 294
IN D IV ID U A LS MATTER Aldo Leopold’s Environmental Ethics 325
Appendix: Measurement Units A1
C AS E S T UDY Hazardous Waste Regulation
in the United States 296
13-7 How Can We Make the Transition to a More Sustainable Low-Waste Society? 297
Glossary Index
G1
I1
C AS E S T UDY Industrial Ecosystems:
Copying Nature 298
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P R E F A C E
For Instructors We wrote this book to help instructors achieve three important goals: first, to explain to their students the basics of earth science, including how life on the earth has survived for billions of years; second, to help students to use this scientific foundation in order to understand the multiple environmental problems that we face and to evaluate possible solutions to them; and third, to inspire their students to make a difference in how we treat the earth on which our lives and economies depend, and thus to make a difference in how we treat ourselves and our descendants. With these goals in mind, we view environmental problems and possible solutions to them through the lens of sustainability—the integrating theme of this book. We believe that most people can live comfortable and fulfilling lives, and that societies will be more prosperous and peaceful when sustainability becomes the chief measure by which personal choices and public policies are made. The news media tend to be full of bad news about the environment. But environmental science is a study that also includes a lot of good news and promise for a better future. We base this vision of a better world on realistic hopes. To emphasize this positive approach, we have added a new feature to this edition. We use Good News logos GOOD to mark areas in this text that present NEWS positive developments in humanity’s efforts to deal with environmental problems.
What’s New in This Edition? Our texts have been widely praised for keeping users upto-date in the rapidly changing field of environmental science. We continue to maintain this and other proven strengths, and in this edition, we have added new updated materials and features, including the following: ■
Many new Case Studies, Science Focus boxes, and Individuals Matter boxes that illustrate scientific principles through enlightening stories about environmental problems or solutions, scientific research, and individuals who made a difference in the world. There are now more than 80 of these boxes.
■
Three Big Ideas at the end of each chapter summarize the three most important ideas of each chapter.
■
A revised design improves the clarity and effic iency of text material.
■
Some 80 new or updated figures illustrate textual material more clearly and completely.
Concept-Centered Approach To help students focus on the main ideas, we built each major chapter section around a key question and one to three key concepts, which state the most important takeaway messages of each chapter section. At the front of each chapter, all key questions and concepts are listed and serve as a chapter outline, and each chapter section begins with its key question and concepts (see pp. 49, 131, and 275). Also, concept applications are highlighted and referenced throughout each chapter. In a new feature of this edition, we list three big ideas at the end of each chapter. This is one of the ways in which we reinforce the key concepts in order to enhance learning.
Sustainability Is the Integrating Theme of This Book Sustainability, a watchword of the 21st century for those concerned about the environment, is the overarching theme of this textbook. You can see the sustainability emphasis by looking at the Brief Contents (p. v). Three principles of sustainability play a major role in carrying out this book’s sustainability theme. These principles are introduced in Chapter 1, depicted in Figure 1-2 (p. 7 and on the back cover of the student edition), and used throughout the book, with each reference marked in the margin by . (See Chapter 7, pp. 134, 141, and 142.)
Five Subthemes Guide the Way toward Sustainability We use the following five major subthemes to integrate material throughout this book (see diagram on back cover). ■
Natural capital. Sustainability depends on the natural resources and natural services that support all life and human economies. Examples of diagrams that illustrate this subtheme are Figures 1-3, p. 8; 3-11, p. 62; and 6-2, p. 111.
■
Natural capital degradation. We describe how human activities can degrade natural capital. Examples of diagrams that illustrate this subtheme are Figures 6-5, p. 113 and 12-25, p. 271.
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■
Solutions. We pay a great deal of attention to the search for solutions to natural capital degradation and other environmental problems. We present proposed solutions in a balanced manner and challenge students to use critical thinking to evaluate them. Some figures and many chapter sections and subsections present possible solutions to various environmental problems. Examples are Figures 6-6, p. 116 and 8-8, p. 162.
■
Trade-Offs. The search for solutions involves tradeoffs, because any solution requires weighing advantages against disadvantages. More than 30 TradeOffs diagrams present the advantages and disadvantages of various environmental technologies and solutions to environmental problems. Examples are Figures 7-8, p. 141; 9-16, p. 200; and 10-13, p. 216.
■
Individuals Matter. In a number of chapters, Individuals Matter boxes describe what various scientists and concerned citizens have done to help us work toward sustainability (see pp. 51, 117, and 261). Also, a number of What Can You Do? diagrams suggest how readers can deal with the problems we face. Examples are Figures 8-16, p. 168 and 10-20, p. 224. Eight especially important things individuals can do—the sustainability eight—are summarized in Figure 14-17 (p. 326).
box provides a closer look at some specific scientific process that has focused on an environmental problem or solution (see pp. 56 and 229). Each Individuals Matter box tells a story of someone who has made a difference in some part of the world in the general quest for a higher level of sustainability (see pp. 117 and 318). As another way of illustrating the concepts and principles in this book, we have included more than 250 figures—89 of them new or improved in this edition. They are designed to present complex ideas in understandable ways relating to the real world (see Figures 1-1, p. 7; 1-10, p. 16; and 2-3, p. 27).
Critical Thinking The introduction on Learning Skills describes critical thinking skills for students (pp. 2–4). Specific critical thinking exercises are used throughout the book in several ways: ■
In all Science Focus boxes (see pp. 123 and 207)
■
In the captions of many of the book’s figures (see Figures 3-8, p. 60; 3-9, p. 61; and 4-9, p. 78)
■
As numerous How Would You Vote? exercises (see pp. 147 and 166)
■
As end-of-chapter questions (see pp. 109 and 225)
Science-Based Global Coverage Chapters 1–4 discuss how scientists work and introduce the scientific principles (see Brief Contents, p. v) necessary for a basic understanding of how natural systems work and for evaluating proposed solutions to environmental problems. Important environmental science topics are explored in depth in Science Focus boxes distributed among the chapters (see pp. 123, 159, and 207). Science is also integrated throughout the book in various Case Studies (see pp. 69, 103, and 120) and in figures (see Figures 2-6, p. 29; 3-2, p. 53; and 7-13, p. 149). This book also provides a global perspective on two levels. First, ecological principles reveal how all the world’s life is connected and sustained within the biosphere (Chapter 2), and these principles are applied throughout the book. Second, the book integrates information and stories from around the world into its presentation of environmental problems and their possible solutions (see pp. 164 and 170).
Case Studies and Illustrations Case Studies appear throughout the book (see pp. 120, 128, and 254), and are listed in the Detailed Contents, pp. vii–x, where case studies are highlighted in BOLD . More than 50 case studies provide in-depth coverage of specific environmental problems and their possible solutions. We include two other forms of case studies in Science Focus and Individuals Matter boxes. Each Science Focus
Three Levels of Flexibility There are hundreds of ways to organize the content of this course to fit the needs of different instructors with a wide variety of professional backgrounds as well as course lengths and goals. To meet these diverse needs, we have designed a highly flexible book that allows instructors to vary the order of chapters and sections within chapters without exposing students to terms and concepts that could confuse them. We recommend that instructors start with Chapter 1 because it defines basic terms and gives an overview of sustainability, population, pollution, resources, and economic development issues that are discussed throughout the book. This provides a springboard for instructors to use other chapters in almost any order. One often-used strategy is to follow Chapter 1 with Chapters 2–6, which introduce basic science and ecological concepts. Instructors can then use the remaining chapters in any order desired. Some instructors follow Chapter 1 with Chapter 14 on environmental economics, politics, and worldviews, before proceeding to the chapters on basic science and ecological concepts. There is also a second level of flexibilty. Instructors who want to emphasize a mastery of basic environmetal concepts and information can rely primarily on the detailed review questions at the end of each chapter and leave out any or all of the book’s numerous critical thinking questions in many figure captions and at the end of each chapter.
xii Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Major Changes in This Edition: A Closer Look Major changes to this edition include the following: ■
New Case Studies (see pp. 13 and 196), Science Focus boxes (see pp. 123 and 159), and Individuals Matter boxes (see pp. 261 and 318) tell stories of realworld applications of the concepts and principles in the book. Each of these special features, along with those that were carried from the previous edition, is focused on a specific environmental problem or solution, a case of real scientific research, or an individual who made a difference in some part of the world in helping us to work toward a higher level of sustainability.
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Dozens of Good News items, each identified by a GOOD NEWS to highlight the many positive achievements of various people, organizations, and countries in dealing with environmental problems.
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Three Big Ideas for each chapter. They are listed just before the review questions at the end of each chapter and reinforce three of the major take-away messages from each chapter.
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A revised design improves the clarity and efficiency of text material.
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More than 80 new or updated figures illustrate textual material more clearly and completely.
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Hundreds of updates based on information and data published in 2007–2010.
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Dozens of new or expanded topics including: ecological tipping points (p. 14); technological innovations that have allowed humans to expand their ecological footprints (p. 14); statistics and probability (p. 24); Edward O. Wilson (p. 51); polar bears and climate change (p. 103); biodiversity hotspots (p. 123); invasive species in the Great Lakes (p. 128); organic agriculture (p. 151); water footprints and virtual water (p. 159); the problem of coal ash storage (p. 196); building a smarter electrical grid (p. 207); toxic effects of mercury (p. 233); the risks of smoking (p. 238); examining the data and conclusions of the IPCC (p. 260); new evidence of climate change and its effects (p. 261); industrial ecosystems (p. 298); Muhammad Yunus and microloans to the poor (p. 309); efforts of college campuses to operate more sustainably (p. 319); and a vision for greater sustainability (p. 326).
Each chapter ends with a Review section containing a detailed set of review questions that include all the chapter’s key terms in bold type (p. 184), followed by a set of Critical Thinking questions (p. 185) to encourage students to think critically and apply what they have learned to their lives.
Supplements for Students A multitude of electronic supplements available to students take the learning experience beyond the textbook: ■
WebTutor Toolbox on WebCT or Blackboard provides qualified adopters of this textbook with access to a full array of study tools, including flashcards, practice quizzes, exercises, and Weblinks.
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Global Environment Watch, updated several times a day, is a focused portal into GREENR—the Global Reference on the Environment, Energy, and Natural Resources—an ideal, one-stop site for classroom discussion and research projects. This resource center keeps courses up-to-date with the most current news on the environment. Students can access information from trusted academic journals, news outlets, and magazines, as well as statistics, an interactive world map, videos, primary sources, case studies, podcasts, and much more.
The following materials for this textbook are available on the companion website at www.cengage.com/login ■
Chapter Summaries help guide student reading and study of each chapter.
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Flash Cards and the Glossary allow students to test their mastery of each chapter’s Key Terms.
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Chapter Tests provide multiple-choice practice quizzes.
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Information on a variety of Green Careers.
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Readings list major books and articles consulted in writing each chapter and include suggestions for articles, books, and websites that provide additional information.
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What Can You Do? offers students resources for how they can effect individual change on key environmental issues.
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Weblinks and Research Frontier Links offer an extensive list of websites with news and research related to each chapter.
In-Text Study Aids Each chapter begins with a list of Key Questions and Concepts showing how the chapter is organized and what students will be learning. When a new term is introduced and defined, it is printed in boldface type and all such terms are highlighted in review questions at the end of each chapter and summarized in the glossary at the end of the book.
Other student learning tools include: ■
Essential Study Skills for Science Students by Daniel D. Chiras. This book includes chapters on developing good study habits, sharpening memory, getting the most out of lectures, labs, and reading assignments, improving test-taking abilities, and becoming a critical thinker. Available for students upon instructor request.
xiii Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Lab Manual. New to this edition, this lab manual includes both hands-on and data analysis labs to help your students develop a range of skills. Create a custom version of this Lab Manual by adding labs you have written or ones from our collection with Cengage Custom Publishing. An Instructor’s Manual for the labs will be available to adopters. What Can You Do? This guide presents students with a variety of ways through which they can affect the environment, and shows them how to track the effect their actions have on their carbon footprint. Available for students upon instructor request.
Supplements for Instructors ■
PowerLecture. This DVD, available to adopters, allows you to create custom lectures in Microsoft® PowerPoint using lecture outlines, all of the figures and photos from the text, and bonus photos and animations. PowerPoint’s editing tools allow the use of slides from other lectures, modification or removal of figure labels and leaders, insertion of your own slides, saving slides as JPEG images, and preparation of lectures for use on the Web.
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Instructor’s Manual. Available to adopters, the Instructor’s Manual has been thoughtfully revised and updated to make creating your lectures even easier. Some of the features new to this edition include updated answers to the end-of-chapter questions, including suggested answers for the review questions and a revised video reference list with Web resources. Also available on PowerLecture.
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Test Bank. Available to adopters, the Test Bank contains thousands of questions and answers in a variety of formats, including multiple choice, true/false, fill-in-the-blank, critical thinking, and essay questions. Also available on PowerLecture.
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Transparencies. Featuring all the illustrations from the chapters, this set contains 250 printed transparencies of key figures and 250 electronic masters. These electronic masters will allow you to print, in color, only those additional figures you need.
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ABC Videos for Environmental Science. The 45 short and informative video clips cover current news stories on environmental issues from around the world. These clips are a great way to start a lecture or spark a discussion. Available on DVD with a workbook, on the PowerLecture DVD, and in CengageNOW with additional Internet activities.
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ExamView. This full-feature program helps you create and deliver customized tests (both print and online) in minutes, using its complete word processing capabilities. Also available on the PowerLecture DVD.
Other Textbook Options Instructors who want a book with a different length and emphasis can use one of our three other books that we have written for various types of environmental science courses: Living in the Environment, 17th edition (675 pages, Brooks/Cole, 2012) Environmental Science, 13th edition (452 pages, Brooks/Cole 2010), and Essentials of Ecology, 6th edition (276 pages, Brooks/Cole, 2012).
Help Us Improve This Book or Its Supplements Let us know how you think we can improve this book. If you find any errors, bias, or confusing explanations, please e-mail us about your concerns at:
[email protected] [email protected] We can correct most errors in subsequent printings of this edition, as well as in future editions.
Acknowledgments We wish to thank the many students and teachers who have responded so favorably to the nine previous editions of Sustaining the Earth, the 16 editions of Living in the Environment, the 13 editions of Environmental Science, and the five editions of Essentials of Ecology, and who have corrected errors and offered many helpful suggestions for improvement. We are also deeply indebted to the more than 295 reviewers, who pointed out errors and suggested many important improvements in the various editions of these three books. It takes a village to produce a textbook, and the members of the talented production team, listed on the copyright page, have made vital contributions. Our special thanks go to development editor Christopher Delgado, who patiently and expertly keeps us on track, production editors Hal Humphrey and Nicole Barone, copy editor Deborah Thompson, layout expert Judy Maenle, photo researcher Abigail Reip, artist Patrick Lane, media editor Alexandria Brady, assistant editor Alexis Glubka, editorial assistants Brandusa Radoias and Joshua Taylor, and Brooks/Cole’s hard-working sales staff. Finally, we are fortunate and delighted to be working with Yolanda Cossio, the Life Sciences Publisher at Brooks/Cole. We thank her for her inspiring leadership and for her many insights and questions that have helped us to improve this book. We also thank Ed Wells and the team who developed the Laboratory Manual to accompany this book, and the people who have translated it into eight languages for use throughout much of the world.
G. Tyler Miller, Jr. Scott E. Spoolman
xiv Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Cumulative Reviewers Barbara J. Abraham, Hampton College; Donald D. Adams, State University of New York at Plattsburgh; Larry G. Allen, California State University, Northridge; Susan Allen-Gil, Ithaca College; James R. Anderson, U.S. Geological Survey; Mark W. Anderson, University of Maine; Kenneth B. Armitage, University of Kansas; Samuel Arthur, Bowling Green State University; Gary J. Atchison, Iowa State University; Thomas W. H. Backman, Lewis-Clark State College; Marvin W. Baker, Jr., University of Oklahoma; Virgil R. Baker, Arizona State University; Stephen W. Banks, Louisiana State University in Shreveport; Ian G. Barbour, Carleton College; Albert J. Beck, California State University, Chico; Eugene C. Beckham, Northwood University; Diane B. Beechinor, Northeast Lakeview College; W. Behan, Northern Arizona University; David Belt, Johnson County Community College; Keith L. Bildstein, Winthrop College; Andrea Bixler, Clarke College; Jeff Bland, University of Puget Sound; Roger G. Bland, Central Michigan University; Grady Blount II, Texas A&M University, Corpus Christi; Lisa K. Bonneau, University of Missouri–Kansas City; Georg Borgstrom, Michigan State University; Arthur C. Borror, University of New Hampshire; John H. Bounds, Sam Houston State University; Leon F. Bouvier, Population Reference Bureau; Daniel J. Bovin, Université Laval; Jan Boyle, University of Great Falls; James A. Brenneman, University of Evansville; Michael F. Brewer, Resources for the Future, Inc.; Mark M. Brinson, East Carolina University; Dale Brown, University of Hartford; Patrick E. Brunelle, Contra Costa College; Terrence J. Burgess, Saddleback College North; David Byman, Pennsylvania State University, Worthington–Scranton; Michael L. Cain, Bowdoin College, Lynton K. Caldwell, Indiana University; Faith Thompson Campbell, Natural Resources Defense Council, Inc.; John S. Campbell, Northwest College; Ray Canterbery, Florida State University; Ted J. Case, University of San Diego; Ann Causey, Auburn University; Richard A. Cellarius, Evergreen State University; William U. Chandler, Worldwatch Institute; F. Christman, University of North Carolina, Chapel Hill; Lu Anne Clark, Lansing Community College; Preston Cloud, University of California, Santa Barbara; Bernard C. Cohen, University of Pittsburgh; Richard A. Cooley, University of California, Santa Cruz; Dennis J. Corrigan; George Cox, San Diego State University; John D. Cunningham, Keene State College; Herman E. Daly, University of Maryland; Raymond F. Dasmann, University of California, Santa Cruz; Kingsley Davis, Hoover Institution; Edward E. DeMartini, University of California, Santa Barbara; James Demastes, University of Northern Iowa; Charles E. DePoe, Northeast Louisiana University; Thomas R. Detwyler, University of Wisconsin; Bruce DeVantier, Southern Illinois University Carbondale; Peter H. Diage, University of California, Riverside; Stephanie Dockstader, Monroe Community College; Lon D. Drake, University
of Iowa; Michael Draney, University of Wisconsin– Green Bay; David DuBose, Shasta College; Dietrich Earnhart, University of Kansas; Robert East, Washington & Jefferson College; T. Edmonson, University of Washington; Thomas Eisner, Cornell University; Michael Esler, Southern Illinois University; David E. Fairbrothers, Rutgers University; Paul P. Feeny, Cornell University; Richard S. Feldman, Marist College; Vicki FellaPleier, La Salle University; Nancy Field, Bellevue Community College; Allan Fitzsimmons, University of Kentucky; Andrew J. Friedland, Dartmouth College; Kenneth O. Fulgham, Humboldt State University; Lowell L. Getz, University of Illinois at Urbana–Champaign; Frederick F. Gilbert, Washington State University; Jay Glassman, Los Angeles Valley College; Harold Goetz, North Dakota State University; Srikanth Gogineni, Axia College of University of Phoenix; Jeffery J. Gordon, Bowling Green State University; Eville Gorham, University of Minnesota; Michael Gough, Resources for the Future; Ernest M. Gould, Jr., Harvard University; Peter Green, Golden West College; Katharine B. Gregg, West Virginia Wesleyan College; Paul K. Grogger, University of Colorado at Colorado Springs; L. Guernsey, Indiana State University; Ralph Guzman, University of California, Santa Cruz; Raymond Hames, University of Nebraska, Lincoln; Robert Hamilton IV, Kent State University, Stark Campus; Raymond E. Hampton, Central Michigan University; Ted L. Hanes, California State University, Fullerton; William S. Hardenbergh, Southern Illinois University at Carbondale; John P. Harley, Eastern Kentucky University; Neil A. Harriman, University of Wisconsin, Oshkosh; Grant A. Harris, Washington State University; Harry S. Hass, San Jose City College; Arthur N. Haupt, Population Reference Bureau; Denis A. Hayes, environmental consultant; Stephen Heard, University of Iowa; Gene Heinze-Fry, Department of Utilities, Commonwealth of Massachusetts; Jane Heinze-Fry, environmental educator; John G. Hewston, Humboldt State University; David L. Hicks, Whitworth College; Kenneth M. Hinkel, University of Cincinnati; Eric Hirst, Oak Ridge National Laboratory; Doug Hix, University of Hartford; S. Holling, University of British Columbia; Sue Holt, Cabrillo College; Donald Holtgrieve, California State University, Hayward; Michelle Homan, Gannon University; Michael H. Horn, California State University, Fullerton; Mark A. Hornberger, Bloomsberg University; Marilyn Houck, Pennsylvania State University; Richard D. Houk, Winthrop College; Robert J. Huggett, College of William and Mary; Donald Huisingh, North Carolina State University; Catherine Hurlbut, Florida Community College at Jacksonville; Marlene K. Hutt, IBM; David R. Inglis, University of Massachusetts; Robert Janiskee, University of South Carolina; Hugo H. John, University of Connecticut; Brian A. Johnson, University of Pennsylvania, Bloomsburg; David I. Johnson, Michigan State University; Mark
xv Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Jonasson, Crafton Hills College; Zoghlul Kabir, Rutgers, New Brunswick; Agnes Kadar, Nassau Community College; Thomas L. Keefe, Eastern Kentucky University; David Kelley, University of St. Thomas; William E. Kelso, Louisiana State University; Nathan Keyfitz, Harvard University; David Kidd, University of New Mexico; Pamela S. Kimbrough; Jesse Klingebiel, Kent School; Edward J. Kormondy, University of Hawaii–Hilo/West Oahu College; John V. Krutilla, Resources for the Future, Inc.; Judith Kunofsky, Sierra Club; E. Kurtz; Theodore Kury, State University of New York at Buffalo; Troy A. Ladine, East Texas Baptist University; Steve Ladochy, University of Winnipeg; Anna J. Lang, Weber State University; Mark B. Lapping, Kansas State University; Michael L. Larsen, Campbell University; Linda Lee, University of Connecticut; Tom Leege, Idaho Department of Fish and Game; Maureen Leupold, Genesee Community College; William S. Lindsay, Monterey Peninsula College; E. S. Lindstrom, Pennsylvania State University; M. Lippiman, New York University Medical Center; Valerie A. Liston, University of Minnesota; Dennis Livingston, Rensselaer Polytechnic Institute; James P. Lodge, air pollution consultant; Raymond C. Loehr, University of Texas at Austin; Ruth Logan, Santa Monica City College; Robert D. Loring, DePauw University; Paul F. Love, Angelo State University; Thomas Lovering, University of California, Santa Barbara; Amory B. Lovins, Rocky Mountain Institute; Hunter Lovins, Rocky Mountain Institute; Gene A. Lucas, Drake University; Claudia Luke, University of California, Berkeley; David Lynn; Timothy F. Lyon, Ball State University; Stephen Malcolm, Western Michigan University; Melvin G. Marcus, Arizona State University; Gordon E. Matzke, Oregon State University; Parker Mauldin, Rockefeller Foundation; Marie McClune, The Agnes Irwin School (Rosemont, Pennsylvania); Theodore R. McDowell, California State University; Vincent E. McKelvey, U.S. Geological Survey; Robert T. McMaster, Smith College; John G. Merriam, Bowling Green State University; A. Steven Messenger, Northern Illinois University; John Meyers, Middlesex Community College; Raymond W. Miller, Utah State University; Arthur B. Millman, University of Massachusetts, Boston; Sheila Miracle, Southeast Kentucky Community & Technical College; Fred Montague, University of Utah; Rolf Monteen, California Polytechnic State University; Debbie Moore, Troy University Dothan Campus; Michael K. Moore, Mercer University; Ralph Morris, Brock University, St. Catherine’s, Ontario, Canada; Angela Morrow, Auburn University; William W. Murdoch, University of California, Santa Barbara; Norman Myers, environmental consultant; Brian C. Myres, Cypress College; A. Neale, Illinois State University; Duane Nellis, Kansas State University; Jan Newhouse, University of Hawaii, Manoa; Jim Norwine, Texas A&M University, Kingsville; John E. Oliver, Indiana State University; Mark Olsen, University of Notre Dame; Carol Page, copy editor; Eric Pallant, Allegheny College; Bill Paletski, Penn State University; Charles F. Park, Stanford University; Richard J.
Pedersen, U.S. Department of Agriculture, Forest Service; David Pelliam, Bureau of Land Management, U.S. Department of the Interior; Murray Paton Pendarvis, Southeastern Louisiana University; Dave Perault, Lynchburg College; Rodney Peterson, Colorado State University; Julie Phillips, De Anza College; John Pichtel, Ball State University; William S. Pierce, Case Western Reserve University; David Pimentel, Cornell University; Peter Pizor, Northwest Community College; Mark D. Plunkett, Bellevue Community College; Grace L. Powell, University of Akron; James H. Price, Oklahoma College; Marian E. Reeve, Merritt College; Carl H. Reidel, University of Vermont; Charles C. Reith, Tulane University; Roger Revelle, California State University, San Diego; L. Reynolds, University of Central Arkansas; Ronald R. Rhein, Kutztown University of Pennsylvania; Charles Rhyne, Jackson State University; Robert A. Richardson, University of Wisconsin; Benjamin F. Richason III, St. Cloud State University; Jennifer Rivers, Northeastern University; Ronald Robberecht, University of Idaho; William Van B. Robertson, School of Medicine, Stanford University; C. Lee Rockett, Bowling Green State University; Terry D. Roelofs, Humboldt State University; Daniel Ropek, Columbia George Community College; Christopher Rose, California Polytechnic State University; Richard G. Rose, West Valley College; Stephen T. Ross, University of Southern Mississippi; Robert E. Roth, Ohio State University; Dorna Sakurai, Santa Monica College; Arthur N. Samel, Bowling Green State University; Shamili Sandiford, College of DuPage; Floyd Sanford, Coe College; David Satterthwaite, I.E.E.D., London; Stephen W. Sawyer, University of Maryland; Arnold Schecter, State University of New York; Frank Schiavo, San Jose State University; William H. Schlesinger, Ecological Society of America; Stephen H. Schneider, National Center for Atmospheric Research; Clarence A. Schoenfeld, University of Wisconsin, Madison; Madeline Schreiber, Virginia Polytechnic Institute; Henry A. Schroeder, Dartmouth Medical School; Lauren A. Schroeder, Youngstown State University; Norman B. Schwartz, University of Delaware; George Sessions, Sierra College; David J. Severn, Clement Associates; Don Sheets, Gardner-Webb University; Paul Shepard, Pitzer College and Claremont Graduate School; Michael P. Shields, Southern Illinois University at Carbondale; Kenneth Shiovitz; F. Siewert, Ball State University; E. K. Silbergold, Environmental Defense Fund; Joseph L. Simon, University of South Florida; William E. Sloey, University of Wisconsin, Oshkosh; Robert L. Smith, West Virginia University; Val Smith, University of Kansas; Howard M. Smolkin, U.S. Environmental Protection Agency; Patricia M. Sparks, Glassboro State College; John E. Stanley, University of Virginia; Mel Stanley, California State Polytechnic University, Pomona; Richard Stevens, Monroe Community College; Norman R. Stewart, University of Wisconsin, Milwaukee; Frank E. Studnicka, University of Wisconsin, Platteville; Chris Tarp, Contra Costa College; Roger E. Thibault, Bowling Green State University; Wil-
xvi Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
liam L. Thomas, California State University, Hayward; Shari Turney, copy editor; John D. Usis, Youngstown State University; Tinco E. A. van Hylckama, Texas Tech University; Robert R. Van Kirk, Humboldt State University; Donald E. Van Meter, Ball State University; Rick Van Schoik, San Diego State University; Gary Varner, Texas A&M University; John D. Vitek, Oklahoma State University; Harry A. Wagner, Victoria College; Lee B. Waian, Saddleback College; Warren C. Walker, Stephen F. Austin State University; Thomas D. Warner, South Dakota State University; Kenneth E. F. Watt, University of California, Davis; Alvin M. Weinberg, Institute of Energy Analysis, Oak Ridge Associated Universities; Brian Weiss; Margery Weitkamp, James Monroe High School (Granada Hills, California); Anthony Weston, State University of New York at Stony Brook; Raymond White, San Francisco City College; Douglas Wickum,
University of Wisconsin, Stout; Charles G. Wilber, Colorado State University; Nancy Lee Wilkinson, San Francisco State University; John C. Williams, College of San Mateo; Ray Williams, Rio Hondo College; Roberta Williams, University of Nevada, Las Vegas; Samuel J. Williamson, New York University; Dwina Willis, FreedHardeman University; Ted L. Willrich, Oregon State University; James Winsor, Pennsylvania State University; Fred Witzig, University of Minnesota at Duluth; Martha Wolfe, Elizabethtown Community and Technical College; George M. Woodwell, Woods Hole Research Center; Todd Yetter, University of the Cumberlands; Robert Yoerg, Belmont Hills Hospital; Hideo Yonenaka, San Francisco State University; Brenda Young, Daemen College; Anita Závodská, Barry University; Malcolm J. Zwolinski, University of Arizona.
xvii Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
About the Authors G. Tyler Miller, Jr. G. Tyler Miller, Jr., has written 59 textbooks for introductory courses in environmental science, basic ecology, energy, and environmental chemistry. Since 1975, Miller’s books have been the most widely used textbooks for environmental science in the United States and throughout the world. They have been used by almost 3 million students and have been translated into eight languages. Miller has a professional background in chemistry, physics, and ecology. He has Ph.D. from the University of Virginia and has received two honorary doctoral degrees for his contributions to environmental education. He taught college for 20 years, developed one of the nation’s first environmental studies programs, and developed an innovative interdisciplinary undergraduate science program before deciding to write environmental science textbooks full time in 1975. Currently, he is the president of Earth Education and Research, devoted to improving environmental education.
He describes his hopes for the future as follows: If I had to pick a time to be alive, it would be the next 75 years. Why? First, there is overwhelming scientific evidence that we are in the process of seriously degrading our own life-support system. In other words, we are living unsustainably. Second, within your lifetime we have the opportunity to learn how to live more sustainably by working with the rest of nature, as described in this book. I am fortunate to have three smart, talented, and wonderful sons—Greg, David, and Bill. I am especially privileged to have Kathleen as my wife, best friend, and research associate. It is inspiring to have a brilliant, beautiful (inside and out), and strong woman who cares deeply about nature as a lifemate. She is my hero. I dedicate this book to her and to the earth.
Scott Spoolman Scott Spoolman is a writer and textbook editor with over 25 years of experience in educational publishing. He has worked with Tyler Miller since 2003 as a contributing editor on earlier editions of Living in the Environment, Environmental Science, and Sustaining the Earth. Spoolman holds a master’s degree in science journalism from the University of Minnesota. He has authored numerous articles in the fields of science, environmental engineering, politics, and business. He worked as an acquisitions editor on a series of college forestry textbooks. He has also worked as a consulting editor in the development of over 70 college and high school textbooks in fields of the natural and social sciences. In his free time, he enjoys exploring the forests and waters of his native Wisconsin along with his family— his wife, environmental educator Gail Martinelli, and his children, Will and Katie. Spoolman has the following to say about his collaboration with Tyler Miller.
I am honored to be working with Tyler Miller as a coauthor to continue the Miller tradition of thorough, clear, and engaging writing about the vast and complex field of environmental science. I share Tyler Miller’s passion for ensuring that these textbooks and their multimedia supplements will be valuable tools for students and instructors. To that end, we strive to introduce this interdisciplinary field in ways that will be informative and sobering, but also tantalizing and motivational. If the flip side of any problem is indeed an opportunity, then this truly is one of the most exciting times in history for students to start an environmental career. Environmental problems are numerous, serious, and daunting, but their possible solutions generate exciting new career opportunities. We place high priorities on inspiring students with these possibilities, challenging them to maintain a scientific focus, pointing them toward rewarding and fulfilling careers, and in doing so, working to help sustain life on the earth.
xix Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
My Environmental Journey G. Tyler Miller, Jr. My environmental journey began in 1966 when I heard a lecture on population and pollution problems by Dean Cowie, a biophysicist with the U.S. Geological Survey. It changed my life. I told him that if even half of what he said was valid, I would feel ethically obligated to spend the rest of my career teaching and writing to help students learn about the basics of environmental science. After spending six months studying the environmental literature, I concluded that he had greatly underestimated the seriousness of these problems. I developed an undergraduate environmental studies program and in 1971 published my first introductory environmental science book, an interdisciplinary study of the connections between energy laws (thermodynamics), chemistry, and ecology. In 1975, I published the first edition of Living in the Environment. Since then, I have completed multiple editions of this textbook, and of three others derived from it, along with other books. Beginning in 1985, I spent ten years in the deep woods living in an adapted school bus that I used as an environmental science laboratory and writing environmental science textbooks. I evaluated the use of passive solar energy design to heat the structure; buried earth tubes to bring in air cooled by the earth (geothermal cooling) at a cost of about $1 per summer; set up active and passive systems to provide hot water; installed an energy-efficient instant hot water heater powered by LPG; installed energy-efficient windows and appliances
and a composting (waterless) toilet; employed biological pest control; composted food wastes; used natural planting (no grass or lawnmowers); gardened organically; and experimented with a host of other potential solutions to major environmental problems that we face. I also used this time to learn and think about how nature works by studying the plants and animals around me. My experience from living in nature is reflected in much of the material in this book. It also helped me to develop the three simple principles of sustainability that serve as the integrating theme for this textbook and to apply these principles to living my life more sustainably. I came out of the woods in 1995 to learn about how to live more sustainably in an urban setting where most people live. Since then, I have lived in two urban villages, one in a small town and one within a large metropolitan area. Since 1970, my goal has been to use a car as little as possible. Since I work at home, I have a “low-pollute commute” from my bedroom to a chair and a laptop computer. I usually take one airplane trip a year to visit my sister and my publisher. As you will learn in this book, life involves a series of environmental trade-offs. Like most people, I still have a large environmental impact, but I continue to struggle to reduce it. I hope you will join me in striving to live more sustainably and sharing what you learn with others. It is not always easy, but it sure is fun.
CENGAGE LEARNING’S COMMITMENT TO SUSTAINABLE PRACTICES We the authors of this textbook and Cengage Learning, the publisher, are committed to making the publishing process as sustainable as possible. This involves four basic strategies: ■
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Using sustainably produced paper. The book publishing industry is committed to increasing the use of recycled fibers, and Cengage Learning is always looking for ways to increase this content. Cengage Learning works with paper suppliers to maximize the use of paper that contains only wood fibers that are certified as sustainably produced, from the growing and cutting of trees all the way through paper production. Reducing resources used per book. The publisher has an ongoing program to reduce the amount of wood pulp, virgin fibers, and other materials that go into
each sheet of paper used. New, specially designed printing presses also reduce the amount of scrap paper produced per book. ■
Recycling. Printers recycle the scrap paper that is produced as part of the printing process. Cengage Learning also recycles waste cardboard from shipping cartons, along with other materials used in the publishing process.
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Process improvements. In years past, publishing has involved using a great deal of paper and ink for writing and editing of manuscripts, copyediting, reviewing page proofs, and creating illustrations. Almost all of these materials are now saved through use of electronic files. Except for our review of page proofs, very little paper and ink were used in the preparation of this textbook.
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Learning Skills Students who can begin early in their lives to think of things as connected, even if they revise their views every year, have begun the life of learning. MARK VAN DOREN
Why Is It Important to Study Environmental Science? Welcome to environmental science—an interdisciplinary study of how the earth works, how we interact with the earth, and how we can deal with the environmental problems we face. Because environmental issues affect every part of your life, the concepts, information, and issues discussed in this book and the course you are taking will be useful to you now and throughout your life. Understandably, we are biased, but we strongly believe that environmental science is the single most important course in your education. What could be more important than learning how the earth works, how we affect its life-support system, and how we can reduce our environmental impact? We live in an incredibly challenging era. We are becoming increasingly aware that during this century, we need to make a new cultural transition in which we learn how to live more sustainably by sharply reducing our degradation of the earth’s life-support system. We hope this book will inspire you to become involved in this change in the way we view and treat the earth, which sustains us, our economies, and all other living things.
You Can Improve Your Study and Learning Skills Maximizing your ability to learn should be one of your most important lifetime educational goals. It involves continually trying to improve your study and learning skills. Here are some suggestions for doing so. Develop a passion for learning. As the famous physicist and philosopher Albert Einstein put it, “I have no special talent. I am only passionately curious.” Get organized. Becoming more efficient at studying gives you more time for other interests. Make daily to-do lists in writing. Put items in order of importance, focus on the most important tasks, and assign a time to work on these items. Because life is full of uncertainties, you might be lucky to accomplish half of the items on your daily list. Shift your schedule as needed to accomplish the most important items.
Set up a study routine in a distraction-free environment. Develop a written daily study schedule and stick to it. Study in a quiet, well-lighted space. Work while sitting at a desk or table—not lying down on a couch or bed. Take breaks every hour or so. During each break, take several deep breaths and move around; this will help you to stay more alert and focused. Avoid procrastination. Avoid putting work off until another time. Do not fall behind on your reading and other assignments. Set aside a particular time for studying each day and make it a part of your daily routine. Do not eat dessert first. Otherwise, you may never get to the main meal (studying). When you have accomplished your study goals, reward yourself with dessert (play or leisure). Make hills out of mountains. It is psychologically difficult to climb a mountain, which is what reading an entire book, reading a chapter in a book, writing a paper, or cramming to study for a test can feel like. Instead, break these large tasks (mountains) down into a series of small tasks (hills). Each day, read a few pages of a book or chapter, write a few paragraphs of a paper, and review what you have studied and learned. As American automobile designer and builder Henry Ford observed, “Nothing is particularly hard if you divide it into small jobs.” Look at the big picture first. Get an overview of an assigned reading in this book by looking at the Key Questions and Concepts box at the beginning of each chapter. It lists both the key questions explored in the chapter sections and their corresponding key concepts, which are the critical lessons to learn in the chapter. Use this list as a chapter road map. When you finish a chapter, you can also use the list to review. Ask and answer questions as you read. For example, “What is the main point of a particular subsection or paragraph?” Relate your own questions to the key questions and key concepts addressed in each major chapter section. In this way, you can flesh out a chapter outline to help you understand the chapter material. You may even want to write out such an outline. Focus on key terms. Use the glossary in your textbook to look up the meanings of terms you do not understand. This book shows all key terms in boldface type and lesser, but still important, terms in italicized type. The review questions
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at the end of each chapter also include the chapter’s key terms in bold type. Flash cards for testing your mastery of key terms for each chapter are available on the website for this book, or you can make your own by putting a term on one side of an index card or piece of paper and its meaning on the other side. Interact with what you read. We suggest that you mark key sentences and paragraphs with a highlighter or pen. Consider putting an asterisk in the margin next to material you think is important and double asterisks next to material you think is especially important. Write comments in the margins and somehow mark pages on which you highlighted passages, so that you can flip through a chapter or book and quickly review the key ideas. Review to reinforce learning. Before each class session, review the material you learned in the previous session and read the assigned material. Become a good note taker. Do not try to take down everything your instructor says. Instead, write down main points and key facts using your own shorthand system. Review, fill in, and organize your notes as soon as possible after each class. Write out answers to questions to focus and reinforce learning. Answer the critical thinking questions found in many figure captions and at the end of each chapter. These questions are designed to inspire you to think critically about key ideas and connect them to other ideas and your own life. Also answer the review questions found at the end of each chapter. The website for each chapter has an additional detailed list of review questions. Writing out your answers to the critical thinking and review questions can reinforce your learning. Save your answers for review and test preparation. Use the buddy system. Study with a friend or become a member of a study group to compare notes, review material, and prepare for tests. Explaining something to someone else is a great way to focus your thoughts and reinforce your learning. Attend any review sessions offered by instructors or teaching assistants. Learn your instructor’s test style. Does your instructor emphasize multiple-choice, fill-in-the-blank, true-orfalse, factual, or essay questions? How much of the test will come from the textbook and how much from lecture material? Adapt your learning and studying methods to your instructor’s style. Become a good test taker. Avoid cramming. Eat well and get plenty of sleep before a test. Arrive on time or early. Calm yourself and increase your oxygen intake by taking several deep breaths. (Do this also about every 10–15 minutes while taking the test.) Look over the test and answer the questions you know well first. Then work on the harder ones. Use the process of elimination to narrow down the choices for multiple-choice questions. For essay questions, organize your thoughts before you start writing. If you have no idea what a question means, make an educated guess. You might earn some
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partial credit and avoid getting a zero. Another strategy for getting some credit is to show your knowledge and reasoning by writing something like this: “If this question means so and so, then my answer is ________.” Develop an optimistic but realistic outlook. Try to be a “glass is half-full” rather than a “glass is half-empty” person. Pessimism, fear, anxiety, and excessive worrying (especially over things you cannot control) are destructive and lead to inaction. Try to keep your energizing feelings of realistic optimism slightly ahead of any immobilizing feelings of pessimism. Then you will always be moving forward. Take time to enjoy life. Every day, take time to laugh and enjoy nature, beauty, and friendship.
You Can Improve Your Critical Thinking Skills: Become Good at Detecting Baloney Critical thinking involves developing the skills to analyze information and ideas, judge their validity, and make decisions. Critical thinking helps you to distinguish between facts and opinions, evaluate evidence and arguments, take and defend informed positions on issues, integrate information and see relationships, and apply your knowledge to dealing with new and different problems, and to your own lifestyle choices. Here are some basic skills for learning how to think more critically. Question everything and everybody. Be skeptical, as any good scientist is. Do not believe everything you hear and read, including the content of this textbook, without evaluating the information you receive. Seek other sources and opinions. Identify and evaluate your personal biases and beliefs. Each of us has biases and beliefs taught to us by our parents, teachers, friends, role models, and our own experience. What are your basic beliefs, values, and biases? Where did they come from? What assumptions are they based on? How sure are you that your beliefs, values, and assumptions are right and why? According to the American psychologist and philosopher William James, “A great many people think they are thinking when they are merely rearranging their prejudices.” Be open-minded and flexible. Be open to considering different points of view. Suspend judgment until you gather more evidence, and be willing to change your mind. Recognize that there may be a number of useful and acceptable solutions to a problem, and that very few issues are black or white. There are trade-offs involved in dealing with any environmental issue, as you will learn in this book. One way to evaluate divergent views is to try to take the viewpoints of other people. How do they see the world? What are their basic assumptions and beliefs? Are their positions logically consistent with their assumptions and beliefs?
LEARNING SKILLS Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Be humble about what you know. Some people are so confident in what they know that they stop thinking and questioning. To paraphrase American writer Mark Twain, “It’s what we know is true, but just ain’t so, that hurts us.” Evaluate how the information related to an issue was obtained. Are the statements you heard or read based on firsthand knowledge and research or on hearsay? Are unnamed sources used? Is the information based on reproducible and widely accepted scientific studies or on preliminary scientific results that may be valid but need further testing? Is the information based on a few isolated stories or experiences, or on carefully controlled studies whose results were reviewed by experts in the field involved? Is it based on unsubstantiated and dubious scientific information or beliefs? Question the evidence and conclusions presented. What are the conclusions or claims? What evidence is presented to support them? Does the evidence support them? Is there a need to gather more evidence to test the conclusions? Are there other, more reasonable conclusions? Try to uncover differences in basic beliefs and assumptions. On the surface, most arguments or disagreements involve differences in opinions about the validity or meaning of certain facts or conclusions. Scratch a little deeper and you will find that most disagreements are usually based on different (and often hidden) basic assumptions concerning how we look at and interpret the world around us. Uncovering these basic differences can allow the parties involved to understand where each is coming from, and to agree to disagree about their basic assumptions, beliefs, or principles. Try to identify and assess any motives on the part of those presenting evidence and drawing conclusions. What is their expertise in this area? Do they have any unstated assumptions, beliefs, biases, or values? Do they have a personal agenda? Can they benefit financially or politically from acceptance of their evidence and conclusions? Would investigators with different basic assumptions or beliefs take the same data and come to different conclusions? Expect and tolerate uncertainty. Recognize that scientists cannot establish absolute proof or certainty about anything. However, the results of reliable science have a high degree of certainty. Do the arguments used involve logical fallacies or debating tricks? Here are six of many examples of such tricks. First, attack the presenter of an argument rather than the argument itself. Second, appeal to emotion rather than facts and logic. Third, claim that if one piece of evidence or one conclusion is false, then all other related pieces of evidence and conclusions are false. Fourth, say that a conclusion is false because it has not been scientifically proven. (Again, scientists never prove anything absolutely.) Fifth, inject irrelevant or misleading information to divert attention from important points. Sixth,
present only either/or alternatives when there may be a number of options. Do not believe everything you read on the Internet. The Internet is a wonderful and easily accessible source of information, including alternative explanations and opinions on almost any subject or issue—much of it not available in the mainstream media and scholarly articles. Web logs, or blogs, have become a major source of information, and are even more important than standard news media for some people. However, because the Internet is so open, anyone can post anything they want to some blogs and other websites with no editorial control or review by experts. As a result, evaluating information on the Internet is one of the best ways to put into practice the principles of critical thinking discussed here. Use and enjoy the Internet, but think critically and proceed with caution. Develop principles or rules for evaluating evidence. Develop a written list of principles (such as the list we are presenting here) to serve as guidelines for evaluating evidence and claims. Continually evaluate and modify this list on the basis of your experience. Become a seeker of wisdom, not a vessel of information. Many people believe that the main goal of education is to learn as much as you can by gathering more and more information. We believe that the primary goal is to learn how to sift through mountains of facts and ideas to find the few nuggets of wisdom that are the most useful for understanding the world and for making decisions. This book is full of facts and numbers, but they are useful only to the extent that they lead to an understanding of key ideas, scientific laws, theories, concepts, and connections. The major goals of the study of environmental science are to find out how nature works and sustains itself, and to use this information to help make human societies and economies more sustainable, more just, and more beneficial and enjoyable for all. As writer Sandra Carey observed, “Never mistake knowledge for wisdom. One helps you make a living; the other helps you make a life.” Or as American writer Walker Percy suggested, “Some individuals with a high intelligence but lacking wisdom can get all A’s and flunk life.” To help you practice critical thinking, we have supplied questions throughout this book—in the captions of many figures, and at the end of each chapter. There are no right or wrong answers to many of these questions. A good way to improve your critical thinking skills is to compare your answers with those of your classmates and to discuss how you arrived at your answers.
Know Your Own Learning Style People have different ways of learning, and it can be helpful to know your own learning style. Visual learners learn best by reading and viewing illustrations and diagrams. They can benefit from using flash cards (available WWW.CENGAGEBRAIN.COM
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on the website for this book) to memorize key terms and ideas. This is a highly visual book with many carefully selected photographs and diagrams designed to illustrate important ideas, concepts, and processes. Auditory learners learn best by listening and discussing. They might benefit from reading aloud while studying and using a tape recorder in lectures for study and review. Logical learners learn best by using concepts and logic to uncover and understand a subject rather than relying mostly on memory. Part of what determines your learning style is how your brain works. According to the split-brain hypothesis, the left hemisphere of the brain is good at logic, analysis, and evaluation, and the right half of the brain is good at visualizing, synthesizing, and creating. One of our goals is to provide material that stimulates both sides of your brain. When you are trying to solve a problem, try to rest, meditate, take a walk, exercise, or do something to shut down your controlling left-brain activity. This will allow the right side of your brain to work on the problem in a less controlled and more creative manner.
This Book Presents a Positive and Realistic Environmental Vision of the Future There are always trade-offs involved in making and implementing environmental decisions. Our challenge is to give a balanced presentation of different viewpoints, the
advantages and disadvantages of various technologies and proposed solutions to environmental problems, and the good and bad news about environmental problems, as well as to do this without injecting personal bias. When a student studies a subject as important as environmental science and ends up with no conclusions, opinions, or beliefs, it means that both the teacher and the student have failed. However, any conclusions one does reach must be found through a process of thinking critically to evaluate different ideas and to understand the trade-offs involved. Our goal is to present a positive vision of our environmental future based on realistic optimism.
Help Us Improve This Book Researching and writing a book that covers and connects ideas in a wide variety of disciplines is a challenging and exciting task. Almost every day, we learn about some new connection in nature. In a book this complex, there are bound to be some errors—some typographical mistakes that slip through and some statements that you might question, based on your knowledge and research. We invite you to contact us to point out any bias, to correct any errors you find, and to suggest ways to improve this book. Please e-mail your suggestions to Tyler Miller at mtg89@hotmail .com or Scott Spoolman at
[email protected]. Now start your journey into this fascinating and important study of how the earth works and how we can leave the planet in a condition at least as good as what we found. Have fun.
Study nature, love nature, stay close to nature. It will never fail you. FRANK LLOYD WRIGHT
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LEARNING SKILLS Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Environmental Problems, Their Causes, and Sustainability
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Key Questions and Concepts* What are three principles of sustainability?
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C O N C E P T 1 - 1 Nature has sustained itself for billions of years by relying on solar energy, biodiversity, and nutrient cycling—lessons from nature that we can apply to our lifestyles and economies.
What is an environmentally sustainable society?
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C O N C E P T 1 - 4 Living sustainably means living off the earth’s natural income without depleting or degrading the natural capital that supplies it.
How are our ecological footprints affecting the earth?
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C O N C E P T 1 - 2 As our ecological footprints grow, we are depleting and degrading more of the earth’s natural capital.
Why do we have environmental problems?
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C O N C E P T 1 - 3 Major causes of environmental problems are population growth, wasteful and unsustainable resource use, poverty, and the exclusion of environmental costs of resource use from the market prices of goods and services.
*This is a concept-centered book, with each major chapter section built around one or two key concepts derived from the natural or social sciences. Key questions and concepts are summarized at the beginning of each chapter. You can use this list as a preview and as a review of the key ideas in each chapter.
Alone in space, alone in its life-supporting systems, powered by inconceivable energies, mediating them to us through the most delicate adjustments, wayward, unlikely, unpredictable, but nourishing, enlivening, and enriching in the largest degree—is this not a precious home for all of us? Is it not worth our love? BARBARA WARD AND RENÉ DUBOS
Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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1-1
What Are Three Principles of Sustainability?
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C O NC EPT 1-1 Nature has sustained itself for billions of years by relying on solar energy, biodiversity, and nutrient cycling—lessons from nature that we can apply to our lifestyles and economies.
Environmental Science Is a Study of Connections in Nature The environment is everything around us, or as the famous physicist Albert Einstein put it, “The environment is everything that isn’t me.” It includes the living and the nonliving things (air, water, and energy) with which we interact in a complex web of relationships that connect us to one another and to the world we live in. Despite our many scientific and technological advances, we are utterly dependent on the environment for clean air and water, food, shelter, energy, and everything else we need to stay alive and healthy. As a result, we are part of, and not apart from, the rest of nature. This textbook is an introduction to environmental science, an interdisciplinary study of how humans interact with the living and nonliving parts of their environment. It integrates information and ideas from the natural sciences such as biology, chemistry, and geology; the social sciences such as geography, economics, and political science; and the humanities such as philosophy and ethics. The three goals of environmental science are to learn how nature works, to understand how we interact with the environment, and to find ways to deal with environmental problems and live more sustainably. A key component of environmental science is ecology, the biological science that studies how organisms, or living things, interact with one another and with their environment. Every organism is a member of a certain species, a group of organisms that have a unique set of characteristics distinguishing them from all other organisms and, for organisms that reproduce sexually, can mate and produce fertile offspring. A major focus of ecology is the study of ecosystems. An ecosystem is a set of organisms within a defined area or volume that interact with one another and with and their environment of nonliving matter and energy. For example, a forest ecosystem consists of plants (especially trees), animals, and tiny micro-organisms that decompose organic materials and recycle their chemicals, all interacting with one another, with solar energy, and with the chemicals in the ecosystem’s air, water, and soil. We should not confuse environmental science or ecology with environmentalism, a social movement dedicated to protecting the earth’s life-support systems for all forms of life. Environmentalism is practiced more in the political and ethical arenas than in the realm of science.
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CHAPTER 1
Nature’s Survival Strategies Follow Three Principles of Sustainability Nature has been dealing with significant changes in environmental conditions that affect the planet for at least 3.5 billion years. This is why many environmental experts say that when we face an environmental change that becomes a problem for us or other species, we should learn how nature has dealt with such changes and then mimic nature’s solutions. In our study of environmental science, the most important question we can ask is how did life on the earth sustain itself for billions of years in the face of changing environmental conditions such as long periods of warming or cooling of the earth’s surface? Considering the 3.5 billion years that life has existed on the earth, our species has been around for less than the blink of an eye (Figure 1-1). Given the fact that we are newcomers, it makes sense that we could learn a lot from the rest of nature. Our research leads us to believe that in the face of frequent, dramatic environmental changes there are three overarching themes to the long-term sustainability of life on this planet: solar energy, biodiversity, and chemical cycling, as summarized below and in Figure 1-2 (Concept 1-1). In order to survive, almost all life forms have relied on energy from the sun, benefited from a great variety of life forms around them, and taken part in the continuous recycling of matter. These powerful and simple ideas make up three principles of sustainability or lessons from nature that we use throughout the book to discuss ways to live more sustainably. •
Reliance on solar energy: The sun warms the planet and supports photosynthesis—a complex chemical process used by plants to provide nutrients, or chemicals that most organisms need to stay alive and reproduce. The sun also powers indirect forms of solar energy such as wind and flowing water, which would not exist without solar energy.
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Biodiversity (short for biological diversity): This refers to the astounding variety of different life forms, the natural systems in which they exist and interact (such as deserts, forests, and oceans), and the natural services that these organisms and living systems provide free of charge (such as renewal of the soil and air and water purification).
Environmental Problems, Their Causes, and Sustainability
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First simple cells appear (about 3.5 billion years ago)
First multicellular life appears (about 1 billion years ago) First major land plants appear (about 475 million years ago)
Dinosaurs disappear (about 65 million years ago)
Figure 1-1 Here, the span of Homo sapiens sapiens’ time on earth is compared with that of all life beginning about 3.5 billion years ago. If the length of this time line were 1 kilometer (0.6 miles), humanity’s time on earth would occupy roughly the last 3 onehundredths of a millimeter. That is less than the diameter of a hair on your head—compared with 1 kilometer of time.
Homo sapiens arrives (about 200,000 years ago)
Solar Energy
Chemical Cycling
Biodiversity
Figure 1-2 Three principles of sustainability: We derive these three interconnected principles of sustainability from learning how nature has sustained a huge variety of life on the earth for at least 3.5 billion years, despite drastic changes in environmental conditions (Concept 1-1).
CONCEPT 1-1 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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•
Chemical cycling: Also referred to as nutrient cycling, this circulation of chemicals from the environment through organisms and back to the environment is necessary for life. Natural processes keep this cycle going, and the earth receives no new supplies of these chemicals. Without chemical cycling, there would be no air, water, soil, or life.
Sustainability Has Certain Key Components Sustainability, the central integrating theme of this book, has several critical components that we use as subthemes. One such component is natural capital—the
natural resources and natural services that keep us and other forms of life alive and support human economies (Figure 1-3). Natural resources are materials and energy in nature that are essential or useful to humans. They are classified as renewable resources (such as air, water, soil, plants, and wind) or nonrenewable resources (such as copper, oil, and coal). Natural services are processes in nature, such as purification of air and water and renewal of topsoil, that support life and human economies. In economic terms, capital refers to money and other forms of wealth that can support a person, a population, or an economy. It can provide a sustainable income if we use it properly—that is, if we do not spend it too quickly. If we protect capital by careful investment and
Natural Capital Natural Capital = Natural Resources + Natural Services Solar energy
Air Renewable energy (sun, wind, water flows)
Air purification Climate control UV protection (ozone layer)
Life (biodiversity) Population control
Water Water purification
Pest control
Waste treatment
Nonrenewable minerals (iron, sand)
Figure 1-3 Natural capital: These key natural resources (darker shaded boxes) and natural services (lighter shaded boxes) support and sustain the earth’s life and human economies (Concept 1-1).
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Natural Oil
Soil Soil renewal gas
Land Food production Nutrient recycling
Nonrenewable energy (fossil fuels)
Coal se
am
Natural resources Natural services
CHAPTER 1
Environmental Problems, Their Causes, and Sustainability
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spending, it can last indefinitely. Similarly, natural capital can support the earth’s diversity of species as long as we use its natural resources and services in a sustainable fashion. One vital natural service is nutrient cycling (Figure 1-4). An important component of nutrient cycling is topsoil, the upper layer of any soil in which plants can grow. It is the vital natural resource that provides the nutrients that support the plants, animals, and microorganisms living on land. Without nutrient cycling in topsoil, life as we know it could not exist. Hence, we consider it to be the basis for one of the three principles of sustainability. A second major component of sustainability—and another subtheme of this text—is to recognize that many human activities can degrade natural capital by using normally renewable resources faster than nature can restore them, and by overloading natural systems with pollution and wastes. For example, in some parts of the world, we are clearing mature forests much faster than they can grow back and withdrawing water that has been stored underground for thousands of years faster than nature can replenish it. We are also loading some rivers, lakes, and oceans with chemical and animal wastes faster than these bodies of water can cleanse themselves. This leads us to a third component of sustainability: solutions. While environmental scientists search for solutions to problems such as the unsustainable degradation of forests and other forms of natural capital, their work is limited to finding the scientific solutions; the political solutions are left to political processes. For example, a scientific solution to the problem of depletion of forests might be to stop burning or cutting down biologically diverse, mature forests and to allow nature to replenish them. But to implement such solutions, governments would probably have to enact and enforce environmental laws and regulations. The search for solutions often involves conflicts. For example, when a scientist argues for protecting a natural forest to help preserve its important diversity of plants and animals, the timber company that had planned to harvest the trees in that forest might protest. Dealing with such conflicts often involves making trade-offs, or compromises—a fourth component of sustainability. For example, the timber company might be persuaded to plant a tree farm from which it could harvest trees, instead of clearing the trees in a diverse natural forest. In making a shift toward environmental sustainability, what each of us does every day is important. In other words, individuals matter. This is the fifth subtheme of this book. Some people are good at thinking of new scientific ideas and innovative solutions. Others are good at putting political pressure on government and business leaders to implement those solutions. In any case, a society’s shift toward sustainability ultimately depends on the actions of individuals, beginning with the daily choices we all make. Thus, sustainability begins at personal and local levels.
Organic matter in animals
Dead organic matter Organic matter in plants Decomposition
Inorganic matter in soil
Figure 1-4 Nutrient cycling: This important natural service recycles chemicals needed by organisms from the environment (mostly from soil and water) through those organisms and back to the environment.
Some Resources Are Renewable and Some Are Not From a human standpoint, a resource is anything obtained from the environment to meet our needs and wants. Some resources such as solar energy, fresh air, fertile topsoil, and edible wild plants are directly available for use. Other resources such as petroleum, iron, underground water, and cultivated crops become useful to us only with some effort and technological ingenuity. Resources vary in terms of how quickly we can use them up and how well nature can replenish them after we use them. Solar energy is called a perpetual resource because its supply is continuous and is expected to last at least 6 billion years, when the sun completes its life cycle. It takes nature anywhere from several days to several hundred years to replenish a renewable resource through natural processes, as long as we do not use up that resource faster than nature can renew it. Examples include forests, grasslands, fish populations, and fertile topsoil. The highest rate at which we can use a renewable resource indefinitely without reducing its available supply is called its sustainable yield. Nonrenewable resources exist in a fixed quantity, or stock, in the earth’s crust. On a time scale of millions to billions of years, geologic processes can renew such resources. But on the much shorter human time scale of hundreds to thousands of years, we can deplete these resources much faster than nature can form them. Such exhaustible stocks include energy resources (such as coal and oil), metallic mineral resources (such as copper and CONCEPT 1-1
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aluminum), and nonmetallic mineral resources (such as salt and sand). As we deplete such resources, human ingenuity can often find substitutes. For example, during this century a mix of renewable energy resources such as wind, the sun, flowing water, and the heat in the earth’s interior could reduce our dependence on nonrenewable fossil fuels such as oil and coal. But often there is no acceptable or affordable substitute. We can recycle or reuse some nonrenewable resources, such as copper and aluminum, to extend their supplies. Reuse involves using a resource over and over in the same form. For example, we can collect, wash, and refill glass bottles many times. Recycling involves collecting waste materials and processing them into new materials. We can crush and melt discarded aluminum to make new aluminum cans or other aluminum products, for example. Recycling nonrenewable metallic resources uses much less energy, water, and other resources, and produces much less pollution and environmental degradation than exploiting virgin metallic resources. Reusing such resources requires even less energy, water, and other resources and produces less pollution and environmental degradation than recycling does.
Countries Differ in Levels of Sustainability As the human population grows, more and more people seek to satisfy their needs and wants. Governmental and societal leaders are charged with making this
1-2
How Are Our Ecological Footprints Affecting the Earth?
▲
C O NC EPT 1-2 As our ecological footprints grow, we are depleting and degrading more of the earth’s natural capital.
We Are Living Unsustainably The bad news is that according to a massive and growing body of scientific evidence, we are living unsustainably by wasting, depleting, and degrading the earth’s natural capital at an accelerating rate. The entire process is known as environmental degradation, summarized in Figure 1-5. We also refer to this as natural capital degradation. In many parts of the world, potentially renewable forests are shrinking, deserts are expanding, soils are eroding, and agricultural lands are deteriorating. In addition, the lower atmosphere is warming, glaciers are
10
possible by maintaining and expanding their national economies, which can lead to growing environmental problems. Economic growth is an increase in a nation’s output of goods and services. It is usually measured by the percentage of change in a country’s gross domestic product (GDP), the annual market value of all goods and services produced by all businesses, foreign and domestic, operating within a country. Changes in a country’s economic growth per person are measured by per capita GDP, the GDP divided by the total population at midyear. While economic growth provides people with more goods and services, economic development has the goal of using economic growth to improve living standards. The United Nations (UN) classifies the world’s countries as economically more developed or less developed based primarily on their average income per person (per capita GDP). The more-developed countries—those that are industrialized and have high per capita GDPs—include the United States, Canada, Japan, Australia, New Zealand, and most European countries. According to UN and World Bank data, the moredeveloped countries, with only 20% of the world’s population, use about 88% of the world’s resources and produce about 75% of the world’s pollution and waste. All other nations, in which 80% of the world’s people live, are classified as less-developed countries, most of them in Africa, Asia, and Latin America. Some are middle-income, moderately developed countries such as China, India, Brazil, Turkey, Thailand, and Mexico. Others are low-income, least-developed countries such as Haiti, Nigeria, and Nicaragua.
CHAPTER 1
melting, sea levels are rising, and floods, droughts, and severe weather are more frequent in some areas. Some rivers are running dry, harvests of many species of fish are dropping sharply, and coral reefs are disappearing. Species are becoming extinct at least 100 times faster than they were in pre-human times, and extinction rates are expected to increase. In 2005, the UN released its Millennium Ecosystem Assessment. According to this 4-year study by 1,360 experts from 95 countries, human activities have degraded about 60% of the earth’s natural or ecosystem services (Figure 1-3), mostly in the past 50 years. In its summary statement, the report warned that “human
Environmental Problems, Their Causes, and Sustainability
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Figure 1-5 Natural capital degradation: This diagram shows examples of the degradation of normally renewable natural resources and services in parts of the world, mostly as a result of rising populations and resource use per person.
Natural Capital Degradation Degradation of Normally Renewable Natural Resources Climate change
Shrinking forests Decreased wildlife habitats
Air pollution
Soil erosion
Species extinction Water pollution
Aquifer depletion
activity is putting such a strain on the natural functions of Earth that the ability of the planet’s ecosystems to sustain future generations can no longer be taken for granted.” The good news, also included in the UN GOOD report, is that we have the knowledge and tools NEWS to conserve rather than degrade or destroy the planet’s natural capital, and there are a number of commonsense strategies for doing so.
✓
HOW WOULD YOU VOTE?** ■
Do you believe that the society you live in is on an unsustainable path? Cast your vote online at www.cengage .com/login.
Pollution Comes from a Number of Sources One of the most basic problems that environmental scientists have addressed is pollution—any presence within the environment of a chemical or other agent such as noise or heat at a level that is harmful to the health, survival, or activities of humans or other organisms. Polluting substances, or pollutants, can enter the environment naturally, such as from volcanic eruptions,
**To cast your vote, go to the website for this book and then to the appropriate chapter (in this case, Chapter 1). In most cases, you will be able to compare how you voted with others using this book.
Declining ocean fisheries
or through human activities, such as the burning of coal and gasoline and the dumping of chemicals into rivers and oceans. The pollutants we produce come from two types of sources. Point sources are single, identifiable sources. Examples are the smokestack of a coal-burning power or industrial plant and the drainpipe of a factory. Nonpoint sources are dispersed and often difficult to identify. Examples are pesticides blown from the land into the air and the runoff of fertilizers from the land into streams and lakes. It is much easier and less costly to identify and control pollution from point sources than from nonpoint sources. There are two main types of pollutants. Biodegradable pollutants are harmful materials that natural processes can break down over time. Examples are human sewage and newspapers. Nondegradable pollutants are harmful chemicals that natural processes cannot break down. Examples are toxic chemical elements such as lead, mercury, and arsenic. Pollutants can have three types of unwanted effects. First, they can disrupt or degrade life-support systems for humans and other species. Second, they can damage wildlife, human health, and property. Third, they can create nuisances such as noise and unpleasant smells, tastes, and sights. We have tried to deal with pollution in two very different ways. One method is pollution cleanup, or output pollution control, which involves cleaning up or diluting pollutants after we have produced them. The other method is pollution prevention, or input pollution control, which reduces or eliminates the production of CONCEPT 1-2
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11
pollutants. We need both pollution prevention (frontof-pipe) and pollution cleanup (end-of-pipe) solutions. But environmental scientists urge us to put more emphasis on prevention because it works better and in the long run is cheaper than cleanup, as we discuss further in later chapters.
The Tragedy of the Commons: Overexploiting Commonly Shared Renewable Resources There are three types of property or resource rights. One is private property, where individuals or companies own the rights to land, minerals, or other resources. A second is common property, where the rights to certain resources are held by large groups of individuals. For example, roughly one-third of the land in the United States is owned jointly by all U.S. citizens and held and managed for them by the government. The third category is open-access renewable resources, owned by no one and available for use by anyone at little or no charge. Examples include the atmosphere, underground water supplies, and fish in the ocean. Many common property and open access renewable resources have been degraded. In 1968, biologist Garrett Hardin (1915–2003) called such degradation the tragedy of the commons. It occurs because most users of an openaccess resource believe that their actions will have little impact on the resource. When the number of users is small, this logic works. Eventually, however, the cumulative effect of many people using a shared resource can degrade it and eventually exhaust or ruin it. There are two major ways to deal with this difficult problem. One is to use a shared renewable resource at a rate well below its estimated sustainable yield by using less of the resource, regulating access to the resource, or doing both. For example, governments can establish laws and regulations limiting the annual harvests of various types of ocean fish. Or they can regulate the amount of pollutants we add to the atmosphere or the oceans. The other way is to convert open-access renewable resources to private ownership. The reasoning is that if you own something, you are more likely to protect your investment. That sounds good, but this approach is not practical for global open-access resources such as the atmosphere and the ocean, which cannot be divided up and sold as private property.
Ecological Footprints: A Model of Unsustainable Use of Resources Many people in less-developed countries struggle to survive. Their individual use of resources and the resulting environmental impact is low and is devoted mostly to
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CHAPTER 1
meeting their basic needs. However, collectively, their impact is high. People in some extremely poor countries, for example, clear virtually all available trees to get enough wood to use for heating and cooking. In such cases, short-term survival is a more urgent priority than long-term sustainability. By contrast, many individuals in more affluent nations each consume large amounts of resources far beyond their basic needs. Supplying people with renewable resources results in wastes and pollution, and can have an enormous environmental impact. We can think of it as an ecological footprint—the amount of biologically productive land and water needed to provide the people in a particular country or area with an indefinite supply of renewable resources and to absorb and recycle the wastes and pollution produced by such resource use. The per capita ecological footprint is the average ecological footprint of an individual in a given country or area. If a country’s (or the world’s) total ecological footprint is larger than its biological capacity to replenish its renewable resources and absorb the resulting wastes and pollution, it is said to have an ecological deficit. In 2008, the World Wildlife Fund (WWF) and the Global Footprint Network estimated that humanity’s global ecological footprint exceeded the earth’s ecological capacity to support humans and other forms of life indefinitely by at least 30% (Figure 1-6, left). That figure was about 88% in high-income countries such as the United States. In other words, humanity is living unsustainably. According to the WWF, we need roughly the equivalent of at least 1.3 earths to provide an endless supply of renewable resources at the rate at which they are being used and to dispose of the resulting pollution and wastes indefinitely. By around 2035, if the number of people and the average rate of renewable resource use continue to grow as projected, we will need the equivalent of two planet earths (Figure 1-6, bottom right) to supply such resources indefinitely (Concept 1-2). The per capita ecological footprint is an estimate of how much of the earth’s renewable resources an individual consumes, on average. After the oil-rich United Arab Emirates, the United States has the world’s second largest per capita ecological footprint. In 2003 (based on the latest data available), the U.S. per capita ecological footprint was about 4.5 times the average global footprint per person, 6 times larger than China’s per capita footprint, and 12 times the average per capita footprint of the world’s low-income countries. According to William Rees and Mathis Wackernagel, the developers of the ecological footprint concept, by using current technology it would take the land area of about five more planet earths for the rest of the world to reach current U.S. levels of renewable resource consumption. Put another way, if everyone consumed as much as the average American does today, the earth could indefinitely support only about 1.3 billion people—not today’s 6.9 billion.
Environmental Problems, Their Causes, and Sustainability
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Total Ecological Footprint (million hectares) and Share of Global Biological Capacity (%) United States
2,810 (25%)
European Union
Japan
United States
2,160 (19%)
China India
Per Capita Ecological Footprint (hectares per person) 9.7
European Union
2,050 (18%)
4.7
China
780 (7%)
India
540 (5%)
1.6 0.8
Japan
4.8
2.5
Unsustainable living Number of Earths
2.0 1.5
Projected footprint 1.0
Ecological footprint
Sustainable living
0.5 0 1961
1970
1980
1990
2000
2010
2020
2030
2040
2050
Year Figure 1-6 Natural capital use and degradation: These graphs show the total and per capita ecological footprints of selected countries (top). In 2008, humanity’s total, or global, ecological footprint was at least 30% higher than the earth’s ecological capacity (bottom) and is projected to be twice the planet’s ecological capacity by around 2035. Question: If we are living beyond the earth’s renewable biological capacity, why do you think the human population and per capita resource consumption are still growing rapidly? (Data from Worldwide Fund for Nature, Global Footprint Network, Living Planet Report 2008. See www.footprintnetwork.org/en/index .php/GFN/page/world_footprint/)
In fact, some scientists worry that we are headed in this direction. As countries with large populations such as China (see the Case Study that follows) and India become more developed, it appears that their per capita resource use is growing toward the per capita levels of more-developed countries such as the United States. ■ CAS E S TUDY
China’s New Affluent Consumers More than a billion consumers in more-developed countries are putting immense pressure on the earth’s natural capital. In addition, more than a half billion new consumers are attaining middle-class, affluent lifestyles in 20 rapidly developing middle-income countries, including China, India, and Brazil. In China and India, the number of middle-class consumers is about 150 million—roughly equal to half of the U.S. population—and growing rapidly. The World Bank has projected that by 2030, the number of middle-class consumers living in today’s less-developed nations will reach 1.2 billion— about four times the current U.S. population. China has the world’s largest population and second-largest economy. It is the world’s leading consumer
of wheat, rice, meat, coal, fertilizer, steel, and cement, and it is the second-largest consumer of oil after the United States. China leads the world in consumption of goods such as televisions, cell phones, and refrigerators. It has built the world’s largest building, the fastest train, and the biggest dam. By 2015, China is projected to be the world’s largest producer and consumer of cars. Also, after 20 years of industrialization, China now contains two-thirds of the world’s most polluted cities. Some of its major rivers are choked with waste and pollution, and some areas of its coastline are basically devoid of fishes and other ocean life. A massive cloud of air pollution, largely generated in China, affects other Asian countries, the Pacific Ocean, and the West Coast of North America. Suppose that China’s economy continues to grow at a rapid rate and its population size reaches 1.5 billion by around 2020, as projected by some experts. Environmental policy expert Lester R. Brown estimates that if such projections are accurate, China will need twothirds of the world’s current grain harvest, twice the the amount of paper currently consumed in the world, and more than all of the oil currently produced in the world.
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13
habitat ranges; and long-term climate disruption caused in part by human-generated emissions of certain gases that cause the atmosphere to warm more rapidly than it would without such emissions. We examine each of these problems in later chapters. Tipping point
Cultural Changes Have Increased Our Ecological Footprints
Figure 1-7 In this example of a tipping point, you can control the ball as you push it up to the highest point on the slope. Beyond that point, you lose control. Ecological tipping points can threaten all or parts of the earth’s life-support system.
Natural Systems Have Tipping Points One problem that we face in dealing with environmental degradation is the time delay between the unsustainable use of renewable resources and the resulting harmful environmental effects. Time delays can allow an environmental problem to build slowly until it reaches a threshold level, or ecological tipping point, beyond which further change can cause an often irreversible shift in the behavior of a natural system (Figure 1-7). Three potential tipping points that we now face are the collapse of certain populations of fish due to overfishing; premature extinction of many species resulting from humans overhunting them or reducing their
Culture is the whole of a society’s knowledge, beliefs, technology, and practices. Human cultural changes have had profound effects on the earth. Evidence of organisms from the past and studies of ancient cultures suggest that the current form of our species, Homo sapiens sapiens, has walked the earth for about 200,000 years—less than an eye-blink in the earth’s 3.5 billion years of life (Figure 1-1). Until about 12,000 years ago, we were mostly hunter–gatherers who obtained food by hunting wild animals and scavenging their remains, and by gathering wild plants. Since then, three major cultural changes have occurred (Figure 1-8). First was the agricultural revolution, which began 10,000–12,000 years ago when humans learned how to grow and breed plants and animals for food, clothing, and other purposes. Second was the industrial–medical revolution, beginning about 275 years ago when people invented machines for the large-scale production of goods in factories. This involved learning how to get energy from fossil fuels (such as coal and oil), and how to grow large quantities of food in an efficient manner. It also included medical advances that have allowed a growing number of people to live longer and healthier lives. Finally, the information–globalization
Human population
Information-globalization revolution
Figure 1-8 Technological innovations have led to greater human control over the rest of nature and to an expanding human population.
14
Agricultural revolution
Industrial-medical revolution
275 yrs ago
12,500 yrs ago
50 yrs ago
Present
Time (not to scale)
CHAPTER 1
Environmental Problems, Their Causes, and Sustainability
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revolution began about 50 years ago, when we developed new technologies for gaining rapid access to much more information and resources on a global scale. Each of these three cultural changes gave us more energy and new technologies with which to use more of the planet’s resources in order to meet our basic needs and increasing wants. They also allowed expansion of the human population, mostly because of increased food supplies and longer life spans. In addition, they each resulted in greater resource use, pollution, and environmental degradation as they allowed
1-3
us to dominate the planet and expand our ecological footprints. Many environmental scientists and other analysts now call for a fourth major cultural change in the form of a sustainability revolution during this century. This cultural transformation would involve learning how to reduce our ecological footprints and to live more sustainably. One way to do this is to copy nature by using the three principles of sustainability (Figure 1-2) to guide our lifestyles and economies as we discuss throughout this textbook.
Why Do We Have Environmental Problems?
▲
CONC EPT 1-3 Major causes of environmental problems are population growth, wasteful and unsustainable resource use, poverty, and the exclusion of environmental costs of resource use from the market prices of goods and services.
Experts Have Identified Four Basic Causes of Environmental Problems According to a number of environmental and social scientists, the major causes of pollution, environmental degradation, and other environmental problems are population growth, wasteful and unsustainable resource use, poverty, and our failure to include in market prices the harmful environmental costs of producing and using goods and services (Figure 1-9) (Concept 1-3). We discuss in detail all of these causes in later chapters of this book. But let us begin with a brief overview of them.
The Human Population Is Growing Exponentially at a Rapid Rate Exponential growth occurs when a quantity such as the human population increases at a fixed percentage per unit of time, such as 2% per year. Exponential growth starts off slowly, but eventually it causes the
quantity to double again and again. After only a few doublings, it grows to enormous numbers because each doubling is twice the total of all earlier growth. Here is an example of the immense power of exponential growth: Fold a piece of paper in half to double its thickness. If you could continue doubling the thickness of the paper 50 times, it would be thick enough to reach almost to the sun—149 million kilometers (93 million miles) away! Because of exponential growth in the human population (Figure 1-10, p. 16), in 2010, there were about 6.9 billion people on the planet. Collectively, these people consume vast amounts of food, water, raw materials, and energy, producing huge amounts of pollution and wastes in the process. Each year, we add more than 80 million people to the earth’s population. Unless death rates rise sharply, there will probably be 9.3 billion of us by 2050. This projected addition of 2.4 billion more people within your lifetime is equivalent to adding about 8 times the current U.S. population and more than twice that of China, the world’s most populous nation.
Causes of Environmental Problems
Population growth
Unsustainable resource use
Poverty
Excluding environmental costs from market prices
Figure 1-9 Environmental and social scientists have identified four basic causes of the environmental problems we face (Concept 1-3). Question: For each of these causes, what are two environmental problems that result?
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15
Figure 1-10 Exponential growth: The J-shaped curve represents past exponential world population growth, with projections to 2100 showing possible population stabilization as the J-shaped curve of growth changes to an S-shaped curve. (This figure is not to scale.) (Data from the World Bank and United Nations, 2008; photo L. Yong/UNEP/Peter Arnold, Inc.)
13 12 11 10
8 7 6 5 4
Billions of people
9 ?
3
Industrial revolution
2
Black Death—the Plague
1 0
2–5 million years
8000
6000
Affluence Has Harmful and Beneficial Environmental Effects The lifestyles of many consumers in more-developed countries and in less-developed countries such as India and China (see Case Study, p. 13) are built upon growing affluence, or wealth that results in high levels of consumption and the unnecessary waste of resources. Such affluence is based mostly on the assumption— fueled by mass advertising—that buying more and more material goods will bring fulfillment and happiness. The harmful environmental effects of affluence are dramatic. The U.S. population is only about one-fourth that of India. But the average American consumes about 30 times as much as the average Indian and 100 times as much as the average person in the world’s poorest countries. As a result, the average environmental impact, or per capita ecological footprint in the United States is much larger than the average impact per person in less-developed countries (Figure 1-6, top). For example, according to some ecological footprint calculators, it takes about 27 tractor-trailer loads of
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CHAPTER 1
2000
2000 B. C.
2100
A. D.
Agricultural revolution
Hunting and gathering
The exponential rate of global population growth has declined some since 1963. Even so, in 2010, we added about 83 million more people to the earth—an average of about 227,000 people per day. This is roughly equivalent to adding a new U.S. city of Los Angeles, California, every 2 weeks, a new France every 9 months, and a new United States every 4 years. We could slow population growth with the GOOD goal of having it level off at around 8 billion by NEWS 2040. Some ways to do this include reducing poverty through economic development, promoting family planning, and elevating the status of women, as we discuss in Chapter 4.
4000 Time
Industrial revolution
resources per year to support one American, or 8.3 billion truckloads per year to support the entire U.S. population. Stretched end-to-end, each year, these trucks would reach beyond the sun. In its 2006 Living Planet Report, the World Wildlife Fund (WWF) estimated that the United States is responsible for almost half of the global ecological footprint. Some analysts say that many affluent consumers in the United States and other more-developed countries are afflicted with affluenza—an eventually unsustainable addiction to buying more and more stuff. They argue that this type of addiction fuels our currently unsustainable use of resources, even though numerous studies show that beyond a certain level, more consumption does not increase happiness. On the other hand, affluence can allow for better education, which can lead people to become more concerned about environmental quality. It also provides money for developing technologies to reduce pollution, environmental degradation, and resource waste. As a result, in the United States and most other afflu- GOOD ent countries, the air is clearer, drinking water is NEWS purer, and most rivers and lakes are cleaner than they were in the 1970s. In addition, the food supply is more abundant and safer, the incidence of life-threatening infectious diseases has been greatly reduced, and life spans are longer.
Poverty Has Harmful Environmental and Health Effects Poverty occurs when people are unable to fulfill their basic needs for adequate food, water, shelter, health, and education. According to a 2008 study by the World Bank, 1.4 billion people—one of every five people on the planet and almost five times the number of people
Environmental Problems, Their Causes, and Sustainability
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Lack of access to
Number of people (% of world's population)
Adequate sanitation facilities
2.6 billion (38%)
Enough fuel for heating and cooking
2 billion (29%)
Electricity
2 billion (29%)
Clean drinking water
1.1 billion (16%)
Adequate health care
1.1 billion (16%)
Adequate housing
1 billion (15%)
Enough food for good health
1 billion (15%)
Figure 1-11 These are some of the harmful effects of poverty. Questions: Which two of these effects do you think are the most harmful? Why? (Data from United Nations, World Bank, and World Health Organization)
living in the United States—live in extreme poverty and struggle to live on the equivalent of less than $1.25 a day. (All dollar figures used in this book are in U.S. dollars.) Poverty causes a number of harmful environmental and health effects (Figure 1-11). The daily lives of the world’s poorest people are focused on getting enough food, water, and fuel for cooking and heating to survive. Desperate for short-term survival, some of these individuals degrade potentially renewable forests, grasslands, and wildlife at an ever-increasing rate. They do not have the luxury of worrying about longterm environmental quality or sustainability. Even though the poor in less-developed countries have no choice but to use very few resources per person, their large population size leads to a high overall environmental impact. While poverty can increase some types of environmental degradation, pollution and environmental degradation have a severe impact on the poor and can worsen their poverty. Consequently, many of the world’s poor people die prematurely from various preventable health problems. One such problem is malnutrition caused by a lack of protein and other nutrients needed for good health. The resulting weakened condition can increase an individual’s chances of death from normally nonfatal ailments such as diarrhea and measles. A second health problem is limited access to adequate sanitation facilities and clean drinking water. More than 2.6 billion people—more than 8 times the population of the United States—have no decent bathroom facilities and are forced to use backyards, alleys, ditches, and streams. As a result, a large portion of these people—one of every seven in the world—get water for drinking, washing, and cooking from sources polluted
by human and animal feces. A third health problem is severe respiratory disease that people get from breathing the smoke of open fires or poorly vented stoves used for heating and cooking inside their homes. In 2008, the World Health Organization estimated that these factors, mostly related to poverty, cause premature death for at least 6 million young children each year. Some hopeful news is that in 2010, this number of annual deaths was down from 12.5 million in 1990. Even so, every day an average of at least 16,400 young children die prematurely from these causes.
Prices Do Not Include the Value of Natural Capital Another basic cause of environmental problems has to do with how goods and services are priced in the marketplace. Companies using resources to provide goods for consumers generally are not required to pay for the harmful environmental costs of supplying such goods. For example, timber companies pay the cost of clear-cutting forests but do not pay for the resulting environmental degradation and loss of wildlife habitat. The primary goal of these companies is to maximize profits for their owners or stockholders. As a result, the prices of goods and services do not include their harmful environmental costs. So consumers have no effective way to evaluate the harmful effects, on their own health and on the earth’s life-support systems, of producing and using these goods and services. Another problem arises when governments (taxpayers) give companies subsidies such as tax breaks and payments to assist them with using resources to run their businesses. Some environmentally harmful subsidies encourage the depletion and degradation of natural capital. We discuss this problem and some possible solutions in Chapter 14.
People Have Different Views about Environmental Problems and Their Solutions Another challenge we face is that people differ over the seriousness of the world’s environmental problems and what we should do to help solve them. This can delay our dealing with these problems, which can make them harder to solve. Differing opinions about environmental problems arise mostly out of differing environmental worldviews. Your environmental worldview is your set of assumptions and values that reflect how you think the world works and what you think your role in the world should be. Consciously or unconsciously, we base most of our actions on our worldviews. Environmental ethics, which are beliefs about what is right and wrong CONCEPT 1-3
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17
with how we treat the environment, are an important element in our worldviews. Here are some important ethical questions relating to the environment: •
Why should we care about the environment?
•
Are we the most important beings on the planet or are we just one of the earth’s millions of different life-forms?
•
Do we have an obligation to see that our activities do not cause other species to disappear?
•
Do we have an ethical obligation to pass the natural world on to future generations in a condition that is at least as good as what we inherited?
•
Should every person be entitled to equal protection from environmental hazards regardless of race, gender, age, national origin, income, social class, or any other factor? This is the central ethical and political issue for what is known as the environmental justice movement.
•
How should we promote sustainability?
People with widely differing environmental worldviews can take the same data, be logically consistent
1-4
What Is an Environmentally Sustainable Society?
▲
C O NC EPT 1-4 Living sustainably means living off the earth’s natural income without depleting or degrading the natural capital that supplies it.
Environmentally Sustainable Societies Protect Natural Capital and Live Off Its Income According to most environmental scientists, our ultimate goal should be to achieve an environmentally sustainable society—one that meets the current and future basic resource needs of its people in a just and equitable manner without compromising the ability of future generations to meet their basic needs. Imagine you win $1 million in a lottery. Suppose you invest this money (your capital) and earn 10% interest per year. If you live on just the interest, or the income made by your capital, you will have a sustainable annual income of $100,000 that you can spend each year indefinitely without depleting your capital. However, if you spend $200,000 per year, while still allowing interest to accumulate, your capital of $1 million will be gone early in the seventh year. Even if you spend just $110,000 per year and allow the interest to accumulate, you will be bankrupt early in the eighteenth year. The lesson here is an old one: Protect your capital and live on the income it provides. Deplete or waste your capital and your lifestyle will become unsustainable.
18
with it, and arrive at quite different conclusions because they start with different assumptions and moral, ethical, or religious beliefs. Environmental worldviews are discussed in detail in Chapter 14, but here is a brief introduction. The planetary management worldview holds that we are separate from and in charge of nature, that nature exists mainly to meet our needs and increasing wants, and that we can use our ingenuity and technology to manage the earth’s life-support systems, mostly for our benefit, indefinitely. The stewardship worldview holds that we can and should manage the earth for our benefit, but that we have an ethical responsibility to be caring and responsible managers, or stewards, of the earth. It says we should encourage only environmentally beneficial forms of economic growth. The environmental wisdom worldview holds that we are part of, and dependent on, nature and that nature exists for all species, not just for us. According to this view, our success depends on learning how life on earth sustains itself and integrating such environmental wisdom into the ways we think and act.
CHAPTER 1
The same lesson applies to our use of the earth’s natural capital—the global trust fund that nature has provided for us, for future generations, and for the earth’s other species. Living sustainably means living on natural income, the renewable resources such as plants, animals, and soil provided by the earth’s natural capital. It also means not depleting or degrading the earth’s natural capital, which supplies this income, and providing the human population with adequate and equitable access to the earth’s natural income for the foreseeable future (Concept 1-4).
Individuals Matter Here are two pieces of good news: First, research GOOD by social scientists suggests that it takes only NEWS 5–10% of the population of a community, a country, or the world to bring about major change. Second, such research also shows that significant beneficial changes can occur in a much shorter time than most people think. Anthropologist Margaret Mead summarized our potential for social change: “Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has.”
Environmental Problems, Their Causes, and Sustainability
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Scientific evidence indicates that we have perhaps 50 years and no more than 100 years to make a new cultural shift from unsustainable living to more sustainable living, if we start now. Many analysts argue that because such a shift will likely take several decades to be complete, we now face a critical fork in the road and must choose a path toward sustainability or continue on our current unsustainable course. One of the goals of this book is to provide a realistic vision of a more environmentally sustainable future. Instead of immobilizing you with fear, gloom, and doom, we hope to energize you by inspiring realistic hope as you play your role in deciding which path to follow. Based on the three principles of sustainability, we can derive three strategies for reducing our ecological footprints, helping to sustain the earth’s natural capital, and making a transition to more
sustainable lifestyles and economies. Those strategies are summarized in the three big ideas of this chapter: ■ We could rely more on renewable energy from the sun, including indirect forms of solar energy such as wind and flowing water, to meet most of our heating and electricity needs. ■ We can protect biodiversity by preventing the degradation of the earth’s species, ecosystems, and natural processes, and by restoring areas we have degraded. ■ We can help to sustain the earth’s natural chemical cycles by reducing our production of wastes and pollution, not overloading natural systems with harmful chemicals, and not removing natural chemicals faster than those chemical cycles can replace them.
What’s the use of a house if you don’t have a decent planet to put it on? HENRY DAVID THOREAU
REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 5. Define environment. Define and distinguish among environmental science, ecology, and environmentalism. Define and distinguish between an organism and a species. What is an ecosystem? What are three prin-ciples that nature has used to sustain itself for at least 3.5 billion years? 2. Define natural capital, natural resources, and natural services. Define nutrient cycling and explain why it is important. Describe how we can degrade natural capital and how finding solutions to environmental problems involves making trade-offs. Explain why individuals matter in dealing with the environmental problems we face. 3. What is a resource? Distinguish between a perpetual resource and a renewable resource and give an example of each. What is sustainable yield? Define and give two examples of a nonrenewable resource. Distinguish between recycling and reuse and give an example of each. Distinguish between economic growth and economic development. Define and distinguish between gross domestic product (GDP) and per capita GDP. Distinguish between more-developed countries and less-developed countries and give examples of a highincome, a middle-income, and a low-income country. 4. Define and give three examples of environmental degradation (natural capital degradation). Define pollution. Distinguish between point sources and nonpoint sources of pollution. Distinguish between biodegradable pollutants and nondegradable pollutants
and give an example of each. Distinguish between pollution cleanup and pollution prevention and give an example of each. What is the tragedy of the commons? 5. What is an ecological footprint? What is a per capita ecological footprint? Compare the total and per capita ecological footprints of the United States and China. Use the ecological footprint concept to explain how we are living unsustainably. Describe the environmental impacts of China’s new affluent consumers. What is an ecological tipping point? 6. Define culture. Describe three major cultural changes that have occurred since humans were hunter–gatherers. What would a sustainability revolution involve? 7. Identify four basic causes of the environmental problems that we face. What is exponential growth? Describe the past, current, and projected exponential growth of the world’s human population. What is affluence? How do Americans, Indians, and the average people in the poorest countries compare in terms of consumption? What are two types of environmental damage resulting from growing affluence? How can affluence help us to solve environmental problems? What is poverty and what are three of its harmful environmental and health effects? What are two of the effects of environmental degradation on poor people? 8. Explain how excluding from market prices the harmful environmental costs of producing and using goods and services plays into the environmental problems we face.
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19
What are subsidies and what effect can they have on natural capital? What is an environmental worldview? What are environmental ethics? Distinguish among the planetary management, stewardship, and environmental wisdom worldviews. 9. Describe an environmentally sustainable society. What is natural income and how is it related to natural capital?
10. What are three ways to work toward making a transition to more sustainable lifestyles and economies as summarized in this chapter’s three big ideas?
Note: Key terms are in bold type.
CRITICAL THINKING 1. Do you think you are living unsustainably? Explain. If so, what are the three most environmentally unsustainable components of your lifestyle? List two ways in which you could apply each of the three principles of sustainability (Figure 1-2) to making your lifestyle more environmentally sustainable.
5. What do you think when you read that at least 16,400 children age five and younger die each day (13 per minute) from preventable malnutrition and infectious diseases? Can you think of something that you and others could do to address this problem? What might that be?
2. For each of the following actions, state one or more of the three principles of sustainability (Figure 1-2) that are involved: (a) recycling aluminum cans; (b) using a rake instead of leaf blower; (c) walking or bicycling to class instead of driving; (d) taking your own reusable bags to the grocery store to carry your purchases home; and (e) volunteering to help restore a prairie.
6. Explain why you agree or disagree with each of the following statements: (a) humans are superior to other forms of life; (b) humans are in charge of the earth; (c) the value of other forms of life depends only on whether they are useful to humans; (d) all forms of life have an inherent right to exist; (e) all economic growth is good; (f) technology can solve our environmental problems; (g) I do not believe I have any obligation to future generations; and (h) I do not believe I have any obligation to other forms of life.
3. Explain why you agree or disagree with the following propositions: a. Stabilizing population is not desirable because, without more consumers, economic growth would stop. b. The world will never run out of resources because we can use technology to find substitutes and to help us reduce resource waste. 4. What do you think when you read that (a) the average American consumes 30 times more resources than the average citizen of India; and (b) human activities are projected to make the earth’s climate warmer? Are you skeptical, indifferent, sad, helpless, guilty, concerned, or outraged? Which of these feelings can help to perpetuate such problems, and which can help to solve them?
7. What are the basic beliefs within your environmental worldview? (You may wish to use the six questions listed on page 18 to help you answer this question. Record your answer, so that when you’ve finished this course, you can return to your answer to see if your worldview has changed.) Are the beliefs included in your environmental worldview consistent with your answers to question 6? Are your actions that affect the environment consistent with your environmental worldview? Explain.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 1 for many study aids and ideas for further
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CHAPTER 1
reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
Environmental Problems, Their Causes, and Sustainability
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2
Science, Matter, Energy, and Systems
Key Questions and Concepts What do scientists do?
2-1
2-4
C O N C E P T 2 - 1 Scientists collect data and develop theories, models, and laws about how nature works.
What keeps us and other organisms alive?
C O N C E P T 2 - 4 Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.
What is matter and what happens when it undergoes change?
2-2
What are the major components of an ecosystem?
2-5
C O N C E P T 2 - 2 A Matter consists of elements and compounds that are in turn made up of atoms, ions, or molecules. C O N C E P T 2 - 2 B Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed (the law of conservation of matter).
What is energy and what happens when it undergoes change?
2-3
Whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed (first law of thermodynamics). CONCEPT 2-3A
C O N C E P T 2 - 3 B Whenever energy is converted from one form to another in a physical or chemical change, we end up with lower-quality or less usable energy than we started with (second law of thermodynamics).
C O N C E P T 2 - 5 Ecosystems contain nonliving and living components, including organisms that produce the nutrients they need, organisms that get the nutrients they need by consuming other organisms, and organisms that recycle nutrients by decomposing the wastes and remains of other organisms.
2-6
What happens to energy in an ecosystem?
As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each succeeding feeding level decreases.
CONCEPT 2-6
2-7
What happens to matter in an ecosystem?
C O N C E P T 2 - 7 Matter, in the form of nutrients, cycles within and among ecosystems throughout the biosphere, and human activities are altering these chemical cycles.
Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house. HENRI POINCARÉ
Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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2-1
What Do Scientists Do?
▲
C O NC EPT 2-1 Scientists collect data and develop theories, models, and laws about how nature works.
Science Is a Search for Order in Nature
Identify a problem
Science is a human effort to discover how the physical world works by making observations and measurements, and carrying out experiments. It is based on the assumption that events in the physical world follow orderly cause-and-effect patterns that we can understand. You may have heard that scientists follow a specific set of steps called the scientific method to learn about how the physical world works. In fact, they use a variety of methods to study nature, although these methods tend to fall within a general process described in Figure 2-1. There is nothing mysterious about this process. You use it all the time in making decisions. Here is an example of how you might apply the scientific process in an everyday situation:
Find out what is known about the problem (literature search)
Ask a question to be investigated
Perform an experiment to answer the question and collect data
Scientific law Well-accepted pattern in data
Analyze data (check for patterns)
Observation: Nothing happens when I try to turn on my flashlight. Propose a hypothesis to explain data
Question: Why didn’t the light come on? Hypothesis: Maybe the batteries are dead. Test the hypothesis with an experiment: Put in new batteries and try to turn on the flashlight.
Use hypothesis to make testable projections
Result: Flashlight still does not work. New hypothesis: Maybe the bulb is burned out.
Perform an experiment to test projections
Experiment: Put in a new bulb. Result: Flashlight works. Conclusion: New hypothesis is verified.
Accept hypothesis
Here is a more formal outline of the steps scientists often take in trying to understand the natural world, although they do not always follow the steps in the order listed.
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•
Identify a problem.
•
Find out what is known about the problem.
•
Ask a question to investigate.
•
Collect data to answer the question. To collect data— information needed to answer questions—scientists make observations in the subject area they are studying. Scientific observations involve gathering information by using the human senses of sight, smell, hearing, and touch, and enhancing those senses by using tools such as rulers, microscopes, and satellites. Often scientists conduct experiments, or procedures carried out under controlled conditions, to gather information and test ideas.
CHAPTER 2
Revise hypothesis
Make testable projections
Test projections Scientific theory Well-tested and widely accepted hypothesis Figure 2-1 This diagram illustrates what scientists do. Scientists use this overall process for testing ideas about how the natural world works. However, they do not necessarily follow the order of steps shown here. For example, sometimes a scientist might start by coming up with a hypothesis to answer the initial question and then run experiments to test the hypothesis.
•
Propose a hypothesis to explain the data. Scientists suggest a scientific hypothesis—a possible explanation of what they observe, in nature or in the results of their experiments, that they can test.
Science, Matter, Energy, and Systems
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•
Make testable projections. Scientists make projections about what should happen if their hypothesis is valid and then run experiments to test the projections.
•
Test the projections with further experiments, models, or observations. Scientists often repeat their experiments, but another way to test predictions is to develop a model, an approximate representation or simulation of a system being studied. Data from experiments can be fed into such models and used to project outcomes. These projections can be compared with the actual measured outcomes from experiments.
•
Accept or reject the hypothesis. If their new data do not support their hypothesis, scientists come up with other testable explanations. This process of proposing and testing various hypotheses goes on until there is general agreement among the scientists in this field of study that a particular hypothesis is the best explanation of the data. A well-tested and widely accepted scientific hypothesis or a group of related hypotheses is called a scientific theory.
Four important features of the scientific process are curiosity, skepticism, reproducibility, and peer review. Good scientists are extremely curious about how nature works. But they tend to be highly skeptical of new data, hypotheses, and models until they can be tested and verified. Scientists also require that any evidence gathered must be reproducible. In other words, other scientists should be able to get the same results when they run the same experiments. Science is a community effort, and an important part of the scientific process is peer review. It involves scientists openly publishing details of the methods and models they used, the results of their experiments, and the reasoning behind their hypotheses for other scientists working in the same field (their peers) to evaluate. Scientific knowledge advances in this self-correcting way, with scientists continually questioning measurements and data, making new measurements, and sometimes coming up with new and better hypotheses. Skepticism and debate among peers in the scientific community is essential to the scientific process.
Scientific Theories and Laws Are the Most Important Results of Science When an overwhelming body of observations and measurements supports a scientific hypothesis, it becomes a scientific theory. We should never take a scientific theory lightly. It has been tested widely, is supported by extensive evidence, and is accepted by most scientists in a particular field or related fields of study. Nonscientists often use the word theory incorrectly when they actually mean scientific hypothesis, a tentative explanation that needs further evaluation.
Another important and reliable outcome of science is a scientific law, or law of nature—a well-tested and widely accepted description of what we find happening repeatedly in nature in the same way. An example is the law of gravity. After making many thousands of observations and measurements of objects falling from different heights, scientists developed the following scientific law: all objects fall to the earth’s surface at predictable speeds. A scientific law is no better than the accuracy of the observations or measurements upon which it is based. But if the data are accurate, a scientific law cannot be broken, unless and until we get contradictory new data. For a superb look at how science works and what scientists do, see the Annenberg Video series, The Habitable Planet: A Systems Approach to Environmental Science (see the website at www.learner.org/resources/ series209.html). Each of the 13 videos describes how scientists working on two different problems related to each subject are learning about how nature works.
Scientific Results Can Be Tentative, Reliable, or Unreliable A fundamental part of science is testing. Scientists insist on testing their hypotheses, models, methods, and results over and over again to establish the reliability of these scientific tools and the resulting conclusions. Sometimes, preliminary scientific results that capture news headlines are controversial because they have not been widely tested and accepted by peer review. They are not yet considered reliable, and can be thought of as tentative science or frontier science. Some of these results will be validated and classified as reliable and some will be discredited and classified as unreliable. At the frontier stage, it is normal for scientists to disagree about the meaning and accuracy of data and the validity of hypotheses and results. By contrast, reliable science consists of data, hypotheses, models, theories, and laws that are widely accepted by all or most of the scientists who are considered experts in the field under study, in what is referred to as a scientific consensus. The results of reliable science are based on the self-correcting process of testing, open peer review, reproducibility, and debate. New evidence and better hypotheses may discredit or alter accepted views. But until that happens, those views are considered to be the results of reliable science. Scientific hypotheses and results that are presented as reliable without having undergone the rigors of widespread peer review, or that have been discarded as a result of peer review, are considered to be unreliable science. Here are some critical thinking questions you can use to uncover unreliable science: •
Was the experiment well designed? Did it involve enough testing?
•
Have other scientists reproduced the results? CONCEPT 2-1
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23
•
Does the proposed hypothesis explain the data? Are there no other, more reasonable explanations of the data?
•
Are the investigators unbiased in their interpretations of the results? Were all the investigators’ funding sources unbiased?
•
Have the data and conclusions been subjected to peer review?
•
Are the conclusions of the research widely accepted by other experts in this field?
If the answer to each of these questions is “yes,” then you can classify the results as reliable science. Otherwise, the results may represent tentative science that needs further testing and evaluation, or you can classify them as unreliable science.
Science Has Some Limitations Environmental science and science in general have five important limitations. First, scientists cannot prove or disprove anything absolutely, because there is always some degree of uncertainty in scientific measurements, observations, and models. Instead, scientists try to establish that a particular scientific theory or law has a very high probability or degree of certainty (at least 90%) of being true and thus is classified as reliable science. Second, scientists are human and thus are not totally free of bias about their own results and hypotheses. However, the high standards of evidence required through peer review can usually uncover or greatly
reduce personal bias and expose occasional cheating by scientists who falsify their results. A third limitation—especially important to environmental science—is that many systems in the natural world involve a huge number of variables with complex interactions. This makes it difficult and too costly to run experiments in order to test each variable. To try to deal with this problem, scientists develop mathematical models that can take into account the interactions of many variables. Running such models on high-speed computers can sometimes overcome the limitations of testing each variable individually, saving both time and money. In addition, scientists can use computer models to simulate global experiments on phenomena like climate change that are impossible to do in a controlled physical experiment. A fourth limitation involves the use of statistical tools, which are necessary in many situations. For example, there is no way to measure accurately how many metric tons of soil are eroded annually worldwide. Instead, scientists use statistical sampling and other mathematical methods to estimate such numbers (Science Focus, below). However, such results should not be dismissed as “only estimates” because they can indicate important trends. Finally, the scientific process is limited to understanding the natural world. It cannot be applied to moral or ethical questions because such questions are about matters for which scientists cannot collect data from the natural world. For example, scientists can use the scientific process to understand the effects of removing trees from an ecosystem, but this process does
SCIE N C E FO C US Statistics and Probability
S
tatistics is a field of study involving the use of mathematical tools to collect, organize, and interpret numerical data. For example, suppose we make measurements of the weight of each individual in a population of 15 rabbits. We can use statistics to calculate the average weight of the population. To do this, we add up the combined weights of the 15 rabbits and divide the total by 15. Scientists also use the statistical concept of probability to evaluate their results. A probability is the chance that a given event will occur or that a given projection will be valid. For example, if you toss a nickel, what is the chance that it will come up heads? If your answer is 50%, you are correct. The probability of the nickel coming up heads is 1/2, which can also be expressed as 50%. Also, probability is often expressed as a number between 0 and 1 written as a decimal (such as 0.5). Now suppose you toss the coin ten times and it comes up heads six times. Does this
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CHAPTER 2
mean that the probability of it coming up heads is 0.6 or 60%? The answer is no because the sample size—the number of events studied—was too small to yield a statistically accurate result. If you increase your sample size to 1,000 by tossing the coin 1,000 times, you are almost certain to get heads 50% of the time and tails 50% of the time. In addition to having a large enough sample size, it is important when doing scientific research in a physical area to take samples from different points within the area in order to get a reasonable evaluation of the variable you are studying. For example, if you wanted to study the effects of a certain air pollutant on the needles of a pine tree species, you would need to locate different stands of the species that are exposed to the pollutant over a certain period of time. At each location, you would have to make measurements of the atmospheric levels of the pollutant at differ-
ent times and average the results. You would also need to take measurements of the damage (such as needle loss) from a large enough number of trees in each location over the same time period. Then you would average the results in each location and compare the results among all locations. If the average results were consistent in different locations, you could then say that there is a certain probability, say 60% (or 0.6), that this type of pine tree suffered a certain percentage loss of its needles when exposed to a specified average level of the pollutant over a given time. Critical Thinking Could there be other factors, such as natural needle loss, insects, plant diseases, and drought that might have caused some of the needle losses you observed? How would you go about determining the effects of these other factors?
Science, Matter, Energy, and Systems
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not tell them whether it is morally or ethically right or wrong to remove the trees. Despite these limitations, science is the most useful way that we have for learning about how nature works and projecting how it might behave in the future. With this important set of tools, we have made significant
2-2
progress, but we still know too little about how the earth works, its present state of environmental health, and the current and future environmental impacts of our activities. These knowledge gaps point to important research frontiers, many of which will provide career opportunities in the future.
What Is Matter and What Happens When It Undergoes Change?
▲
CONC EPT 2-2A
▲
CONC EPT 2-2B
Matter consists of elements and compounds that are in turn made up of atoms, ions, or molecules. Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed (the law of conservation of matter).
Matter Consists of Elements and Compounds To begin our study of environmental science, we look at matter—the stuff that makes up life and its environment. Matter is anything that has mass and takes up space. It can exist in three physical states—solid, liquid, and gas. Water, for example, exists as solid ice, liquid water, or water vapor depending mostly on its temperature. Matter also exists in two chemical forms—elements and compounds. An element is a fundamental type of matter that has a unique set of properties and cannot be broken down into simpler substances by chemical means. For example, gold is an element. It cannot be broken down chemically into any other substance. Some matter is composed of one element, such as gold. But most matter consists of compounds, combinations of two or more different elements held together in fixed proportions. For example, water is a compound made of the elements hydrogen and oxygen that can combine chemically with one another. To simplify things, chemists represent each element by a one- or two-letter symbol. Examples used in this book are hydrogen (H), carbon (C), oxygen (O), nitrogen (N), phosphorus (P), sulfur (S), chlorine (Cl), fluorine (F), bromine (Br), sodium (Na), calcium (Ca), lead (Pb), mercury (Hg), arsenic (As), and uranium (U). Just four elements—oxygen, carbon, hydrogen, and nitrogen—make up about 96% of your body weight and that of most other living things.
Atoms, Molecules, and Ions Are the Building Blocks of Matter The most basic building block of matter is an atom, the smallest unit of matter into which an element can be divided and still have its characteristic chemical proper-
ties (Concept 2-2A). The idea that all elements are made up of atoms is called the atomic theory and it is the most widely accepted scientific theory in chemistry. Atoms are incredibly small. In fact, more than 3 million hydrogen atoms could sit side by side on the period at the end of this sentence. If you could view them with a super-microscope, you would find that each different type of atom contains a certain number of three types of subatomic particles: neutrons (n) with no electrical charge, protons (p) with a positive electrical charge (+), and electrons (e) with a negative electrical charge (–). Each atom consists of an extremely small center called the nucleus—containing one or more protons and, in most cases, one or more neutrons—and one or more electrons in rapid motion somewhere around the nucleus (Figure 2-2, p. 26). Each atom (except for ions, explained below) has equal numbers of positively charged protons and negatively charged electrons. Because these electrical charges cancel one another, atoms as a whole have no net electrical charge. Each element has a unique atomic number equal to the number of protons in the nucleus of its atom. Carbon (C), with 6 protons in its nucleus (Figure 2-2), has an atomic number of 6, whereas uranium (U), a much larger atom, has 92 protons in its nucleus and an atomic number of 92. Because electrons have so little mass compared to protons and neutrons, most of an atom’s mass is concentrated in its nucleus. The mass of an atom is described by its mass number, the total number of neutrons and protons in its nucleus. For example, a carbon atom with 6 protons and 6 neutrons in its nucleus has a mass number of 12, and a uranium atom with 92 protons and 143 neutrons in its nucleus has a mass number of 235 (92 + 143 = 235). Each atom of a particular element has the same number of protons in its nucleus. But the nuclei of CONCEPTS 2-2A AND 2-2B
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25
Figure 2-2 This is a greatly simplified model of a carbon-12 atom. It consists of a nucleus containing six protons, each with a positive electrical charge, and six neutrons with no electrical charge. Six negatively charged electrons are found outside its nucleus. We cannot determine the exact locations of the electrons. Instead, we can estimate the probability that they will be found at various locations outside the nucleus—sometimes called an electron probability cloud. This is somewhat like saying that there are six airplanes flying around inside a cloud. We do not know their exact location, but the cloud represents an area in which we can probably find them.
6 protons
6 neutrons
6 electrons
atoms of a particular element can vary in the number of neutrons they contain, and therefore, in their mass numbers. Different forms of an element having the same atomic number but different mass numbers are called isotopes of that element. Scientists identify isotopes by attaching their mass numbers to the name or symbol of the element. For example, the three most common isotopes of carbon are carbon-12 (Figure 2-2, with six protons and six neutrons), carbon-13 (with six protons and seven neutrons), and carbon-14 (with six protons and eight neutrons). Carbon-12 makes up about 98.9% of all naturally occurring carbon. A second building block of matter is a molecule, a combination of two or more atoms of the same or different elements held together by forces called chemical bonds. Molecules are the basic units of some compounds, called molecular compounds (Concept 2-2A). Chemists use a chemical formula to show the number of each type of atom or ion in a compound. This shorthand contains the symbol for each element present and uses subscripts to represent the number of atoms or ions of each element in the compound’s basic structural unit. Examples of compounds and their formulas encountered in this book are water (H2O, read as “H-two-O”), oxygen gas (O2), ozone (O3), nitrogen gas (N2), nitrous oxide (N2O), nitric oxide (NO), hydrogen sulfide (H2S), carbon monoxide (CO), carbon dioxide (CO2), nitrogen dioxide (NO2), sulfur dioxide (SO2), sodium chloride (NaCl), ammonia (NH3), sulfuric acid (H2SO4), nitric acid (HNO3), methane (CH4), and glucose (C6H12O6). A third building block of matter is an ion—an atom or a group of atoms with one or more net positive or negative electrical charges. Like atoms, ions are made up of protons, neutrons, and electrons. A positive ion forms when an atom loses one or more of its negatively charged electrons, and a negative ion forms when an atom gains one or more negatively charged electrons. Chemists use a superscript after the symbol of an ion to indicate how many positive or negative electrical charges it has. (One positive or negative charge is designated by a plus sign or a minus sign, respectively.) Examples encountered in this book include positive hydrogen ions (H+), sodium ions (Na+), calcium ions (Ca2+), and ammonium ions (NH4+) and negative chloride ions (Cl–), nitrate ions (NO2–), sulfate ions (SO42–), and phosphate ions (PO43–). Ions are the building blocks of some compounds, called ionic compounds (Concept 2-2A). Ions are also important for measuring a substance’s acidity in a water solution, a chemical characteris-
26
CHAPTER 2
tic that helps determine how a substance dissolved in water will interact with and affect its environment. The acidity of a water solution is based on the comparative amounts of hydrogen ions (H+) and hydroxide ions (OH–) contained in a particular volume of the solution. Scientists use a numerical scale of pH values to compare the acidity and alkalinity in water solutions (Figure 2-3). The pH of a soil influences the uptake of natural chemicals in the soil by plants.
Organic Compounds Are the Chemicals of Life Plastics, as well as table sugar, vitamins, aspirin, penicillin, and most of the chemicals in your body are called organic compounds because their molecules contain at least two carbon atoms combined with atoms of one or more other elements. All other compounds are called inorganic compounds, except for methane (CH4), which has only one carbon atom but is considered an organic compound. The millions of known organic (carbon-based) compounds include the following: •
Hydrocarbons: compounds of carbon and hydrogen atoms. One example is methane (CH4), the main component of natural gas, and the simplest organic compound. Another is octane (C8H18), a major component of gasoline.
•
Chlorinated hydrocarbons: compounds of carbon, hydrogen, and chlorine atoms. An example is the insecticide DDT (C14H9Cl5).
•
Simple carbohydrates (simple sugars): certain types of compounds of carbon, hydrogen, and oxygen atoms. An example is glucose (C6H12O6), which most plants and animals break down in their cells to obtain energy.
Larger and more complex organic compounds, essential to life, are composed of macromolecules. Some of these molecules are called polymers, formed when a number of simple organic molecules (monomers) are linked together by chemical bonds—somewhat like rail cars linked in a freight train. The three major types of organic polymers are:
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0
10–1
1
2
10–2
Lemon juice, some acid rain
3
10–3
Vinegar, wine, beer, oranges
4
Figure 2-3 The pH scale, representing the concentration of hydrogen ions (H+) in one liter of solution, is shown on the right-hand side. On the left side are the approximate pH values for solutions of some common substances. A solution with a pH less than 7 is acidic, one with a pH of 7 is neutral, and one with a pH greater than 7 is basic. Pure water (not tap water or rainwater) is a neutral solution with an equal number of H+ and OH– ions and a pH of 7. A change of 1 on the pH scale means a tenfold increase or decrease in H+ concentration. (Modified from Cecie Starr, Biology: Today and Tomorrow, Pacific Grove, CA: Brooks/Cole, © 2005)
100
Hydrochloric acid (HCl) Gastric fluid (1.0–3.0)
10–4
Tomatoes Bananas Black coffee Bread Typical rainwater
10–5
5
6
10–6
Urine (5.0–7.0) Milk (6.6)
7
10–7
Pure water Blood (7.3–7.5) Egg white (8.0) Seawater (7.8–8.3) Baking soda Phosphate detergents Bleach, Tums Soapy solutions, Milk of magnesia
10–8
8
10–9
9
1
10–10
0
1 1 •
•
Complex carbohydrates such as cellulose and starch, used by plants to store energy and by the animals that eat the plants; they consist of two or more monomers of simple sugars such as glucose.
10–11
Household ammonia (10.5–11.9)
1 2
10–12
1 Hair remover 3 Oven cleaner 1 Sodium hydroxide (NaOH) 4
Proteins formed by monomers called amino acids that are linked together; important to living life forms for storing energy, maintaining immune systems, building body tissues, and creating hormones.
10–13 10–14
Lipids, which include fats and waxes, are not made of monomers but are a fourth type of macromolecule essential to some life forms for storing energy and building tissues.
Finally, these building blocks combine to form the fundamental unit of all living things—the cell: a minute compartment containing chemicals necessary for life and within which most of the processes of life take place. Living things may consist of a single cell (bacteria, for instance) or huge numbers of cells, as is the case for most plants and animals. The relationships among these genetic materials and cells are shown in Figure 2-4 (p. 28).
Matter Comes to Life through Genes, Chromosomes, and Cells
Some Forms of Matter Are More Useful Than Others
Within some DNA molecules are certain sequences of nucleotides called genes. Each of these coded units of genetic information concerns a specific trait, or characteristic, passed on from parents to offspring during reproduction in an animal or plant. Thousands of genes, in turn, make up a single chromosome, a special DNA molecule wrapped around a number of proteins. Genetic information coded in your chromosomal DNA is what makes you different from an oak leaf, an alligator, or a flea, and from your parents. In other words, it makes you human, but it also makes you unique.
Matter quality is a measure of how useful a form of matter is to humans as a resource, based on its availability and concentration—the amount of it that is contained in a given area or volume (Figure 2-5, p. 28). Highquality matter is highly concentrated, is typically found near the earth’s surface, and has great potential for use as a resource. Low-quality matter is not highly concentrated, is often located deep underground or dispersed in the oceans or the atmosphere, and usually has little potential for use as a resource. In summary, matter consists of elements and compounds that in turn are made up of atoms, ions, or
•
Nucleic acids (DNA and RNA) formed by monomers called nucleotides that are linked together.
CONCEPTS 2-2A AND 2-2B Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
27
Figure 2-4 This diagram shows the relationships among cells, nuclei, chromosomes, DNA, and genes.
High Quality
Low Quality
Solid
Gas
Salt
Solution of salt in water
Coal
Coal-fired power plant emissions
Gasoline
Automobile emissions
Aluminum can
Aluminum ore
A human body contains trillions of cells, each with an identical set of genes.
Each human cell (except for red blood cells) contains a nucleus.
Each cell nucleus has an identical set of chromosomes, which are found in pairs.
A specific pair of chromosomes contains one chromosome from each parent.
Each chromosome contains a long DNA molecule in the form of a coiled double helix.
Genes are segments of DNA on chromosomes that contain instructions to make proteins—the building blocks of life.
molecules (Concept 2-2). Some forms of matter are more useful as resources than others are because of their availability and concentrations.
Figure 2-5 These examples illustrate the differences in matter quality. High-quality matter (left column) is fairly easy to extract and is highly concentrated; low-quality matter (right column) is not highly concentrated and is more difficult to extract than high-quality matter.
Matter Can Undergo Change But Cannot Be Created or Destroyed
gaseous compound carbon dioxide (CO2). We represent this reaction with the following equation:
When a sample of matter undergoes a physical change, there is no change in its chemical composition, or the arrangement of its atoms or ions within its molecules. A piece of aluminum foil cut into small pieces is still aluminum foil. When solid water (ice) melts and when liquid water boils, the resulting liquid water and water vapor are still made up of H2O molecules. When a chemical change, or chemical reaction, takes place, there is a change in the chemical composition of the substances involved. Chemists use a chemical equation to show how atoms and ions are rearranged in a chemical reaction. For example, when coal is burned completely, the solid carbon (C) in the coal combines with oxygen gas (O2) from the atmosphere to form the
28
CHAPTER 2
Reactant(s) Carbon
Product(s)
+
Oxygen
C
+
O2
C
+
Carbon dioxide +
Energy
+
Energy
CO2
O O
C
O
+ Energy
O Black solid
Colorless gas
Colorless gas
We can change elements and compounds from one physical or chemical form to another, but we can never create or destroy any of the atoms involved in any physical or chemical change. All we can do is rearrange the
Science, Matter, Energy, and Systems
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atoms, ions, or molecules into different spatial patterns (physical changes) or chemical combinations (chemical changes). These observations, based on many thousands of measurements, describe a scientific law known as the law of conservation of matter: Whenever matter undergoes a physical or chemical change, no atoms are created or destroyed (Concept 2-2B).
2-3
This law means there is no “away” as in “to throw away.” Everything we think we have thrown away remains here with us in some form. We can reuse or recycle some materials and chemicals, but the law of conservation of matter means we will always face the problem of what to do with some quantity of the wastes and pollutants we produce.
What Is Energy and What Happens When It Undergoes Change?
▲
CONC EPT 2-3A
▲
CONC EPT 2-3B
Whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed (first law of thermodynamics). Whenever energy is converted from one form to another in a physical or chemical change, we end up with lower-quality or less usable energy than we started with (second law of thermodynamics).
Energy Comes in Many Forms and Some Are More Useful Than Others
of a wave as a result of changes in electrical and magnetic fields. There are many different forms of electromagnetic radiation (Figure 2-6), each having a different wavelength (the distance between successive peaks or troughs in the wave) and energy content. Forms of electromagnetic radiation with short wavelengths, such as gamma rays, X rays, and ultraviolet (UV) radiation, have more energy than do forms with longer wavelengths, such as visible light and infrared (IR) radiation. Visible light makes up most of the spectrum of electromagnetic radiation emitted by the sun. The other major type of energy is potential energy, which is stored and potentially available for use. Examples of this type of energy include a rock held in your hand, the water in a reservoir behind a dam, and the chemical energy stored in the carbon atoms of coal. We can change potential energy to kinetic energy. If you hold this book in your hand, it has potential energy. However, if you drop it on your foot, the book’s potential energy changes to kinetic energy. Potential energy stored in the molecules of foods you eat becomes kinetic
Energy is the capacity to do work or transfer heat. Work is done when something is moved. Work is performed when an object such as this book is moved over some distance. Heat is transferred when natural gas, for example, is burned to heat a house. There are two major types of energy: moving energy (called kinetic energy) and stored energy (called potential energy). Matter in motion has kinetic energy, which is energy associated with motion. Examples are flowing water, wind (a mass of moving air), and electricity (electrons flowing through a wire or other conducting material). Another form of kinetic energy is heat, the total kinetic energy of all moving atoms, ions, or molecules within a given substance. When two objects at different temperatures contact one another, heat flows from the warmer object to the cooler object. You learned this the first time you touched a hot stove. Another form of kinetic energy is called electromagnetic radiation, in which energy travels in the form
Visible light
Blue light
Gamma rays
Red light
UV radiation
X rays
Infrared radiation
Microwaves
TV, Radio waves
Shorter wavelengths and higher energy Wavelengths (not to scale)
Longer wavelengths and lower energy 0.001
0.01
0.1
Nanometers
1
10
0.1
10 Micrometers
100
0.1
1
10
Centimeters
1
10
100
Meters
Figure 2-6 The electromagnetic spectrum consists of a range of electromagnetic waves, which differ in wavelength (the distance between successive peaks or troughs) and energy content.
CONCEPTS 2-3A AND 2-3B Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
29
energy when your body uses it to move and do other forms of work. About 99% of the energy that heats the earth and our buildings, and supports plants (through a process called photosynthesis) that provide us and other animals with food comes from the sun at no cost to us. This is in keeping with the solar energy principle of sustainability (see back cover). This direct input of solar energy produces several other indirect forms of renewable solar energy. Examples are wind (moving air driven by heat from the sun), hydropower (falling and flowing water kept fluid by solar energy), and biomass (solar energy converted to chemical energy and stored in the chemical bonds of organic compounds in trees and other plants). Energy quality is a measure of the capacity of a type of energy to do useful work. High-quality energy has a great capacity to do useful work because it is concentrated. Examples are very high-temperature heat, concentrated sunlight, high-speed wind, and the energy released when we burn gasoline or coal. By contrast, low-quality energy is so dispersed that it has little capacity to do useful work. An example is heat dispersed in the moving molecules of a large amount of matter (such as the atmosphere or an ocean) so that its temperature is low.
Energy Changes Are Governed by Two Scientific Laws Thermodynamics is the study of energy transformations. After observing and measuring energy being changed from one form to another in millions of physical and chemical changes, scientists have summarized their results in the first law of thermodynamics, also known as the law of conservation of energy. According to this scientific law, whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed (Concept 2-3A).
This scientific law tells us that no matter how hard we try or how clever we are, we cannot get more energy out of a physical or chemical change than we put in. This is one of nature’s basic rules that has never been violated. Thousands of experiments have shown that whenever energy is converted from one form to another in a physical or chemical change, we end up with lower-quality or less useable energy than we started with (Concept 2-3B). This is a statement of the second law of thermodynamics. The resulting low-quality energy usually takes the form of heat that flows into the environment where it is dispersed by the random motion of air or water molecules and becomes even less useful as a resource. In other words, when energy is changed from one form to another, it always goes from a more useful to a less useful form. No one has ever found a violation of this fundamental scientific law. Consider three examples of the second law of thermodynamics in action. First, when you drive a car, an average of about 87% of the high-quality energy available in its gasoline fuel is degraded to low-quality heat that is released into the environment. That is, about 87% of the money we spend on gasoline is not used to transport us anywhere. Second, when electrical energy in the form of moving electrons flows through filament wires in an incandescent lightbulb, about 5% of it is converted into useful light, and 95% flows into the environment as lowquality heat. In other words, the incandescent lightbulb is really an energy-wasting heat bulb. By comparison, in a compact fluorescent bulb with the same brightness, about 20% of the energy input becomes useful light. Third, in living systems, solar energy is converted into chemical energy (food molecules) and then into mechanical energy (used for moving, thinking, and living). During each conversion, high-quality energy is degraded and flows into the environment as lowquality heat. Trace the flows and energy conversions in Figure 2-7 to see how this happens.
Waste heat
Mechanical energy (moving, thinking, living)
Chemical energy (food)
Chemical energy (photosynthesis)
Solar energy
Waste heat
Waste heat
Waste heat
Figure 2-7 This diagram demonstrates the second law of thermodynamics in action in living systems. Each time energy changes from one form to another, some of the initial input of high-quality energy is degraded, usually to low-quality heat that is dispersed into the environment.
30
CHAPTER 2
Science, Matter, Energy, and Systems
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The second law of thermodynamics also means we can never recycle or reuse high-quality energy to perform useful work. Once the concentrated energy in a serving of food,
2-4
a liter of gasoline, or a chunk of uranium is released, it is degraded to low-quality heat that is dispersed into the environment.
What Keeps Us and Other Organisms Alive?
▲
CONC EPT 2-4 Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.
Ecology Is the Study of Connections in Nature Ecology (from the Greek words oikos, “house” or “place to live,” and logos, “study of”) is the study of how living things interact with one another and with their nonliving environment. In effect, it is a study of connections in nature—the house for the earth’s life. To enhance their understanding of nature, scientists classify matter into levels of organization from atoms to cells to the biosphere. Ecologists focus on trying to understand the interactions among organisms, populations, communities, ecosystems, and the biosphere (Figure 2-8). An organism is any form of life. It is the most fundamental unit of ecology. Organisms may consist of a single cell (bacteria, for instance) or many cells. Look in the mirror. What you see is about 10 trillion cells divided into about 200 different types. Every organism is a member of a certain species: a set of organisms that resemble one another in appearance, behavior, chemistry, and genetic makeup. Organisms that reproduce sexually (combining cells from both parents to produce offspring) must be able to produce live, fertile offspring in order to be considered members of the same species. We do not know how many species exist on earth. Estimates range from 4 million to 100 million, with the best estimates ranging between 10 million and 14 million. So far, biologists have identified about 1.75 million species, most of them insects (Science Focus, p. 32).
Life Is Organized within Populations, Communities, and Ecosystems A population is a group of individuals of the same species that live in the same place at the same time. Examples include a school of one species of fish in a pond, the field mice living in a cornfield, and the people who live in a country. In most natural populations, individuals vary slightly in their genetic makeup, which is why they do not all look or act alike. This variation in a population is called genetic diversity. The place where a population or an individual organism normally lives is its habitat. It may be as large
O H
Biosphere
Parts of the earth's air, water, and soil where life is found
Ecosystem
A community of different species interacting with one another and with their nonliving environment of matter and energy
Community
Populations of different species living in a particular place, and potentially interacting with each other
Population
A group of individuals of the same species living in a particular place
Organism
An individual living being
Cell
The fundamental structural and functional unit of life
Molecule
Chemical combination of two or more atoms of the same or different elements
Atom
Smallest unit of a chemical element that exhibits its chemical properties
H Water
H
O
Hydrogen
Oxygen
Figure 2-8 Some levels of organization of matter in nature are shown here. Ecology focuses on the top five of these levels.
CONCEPT 2-4 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
31
SCIE N C E FO C US Have You Thanked the Insects Today?
A
lthough insects generally have a bad reputation, they are an important part of the earth’s natural capital. We classify many insect species as pests because they compete with us for food, spread human diseases such as malaria, bite or sting us, and invade our lawns, gardens, and houses. Some people fear insects and think the only good bug is a dead bug. They fail to recognize the vital roles insects play in helping to sustain life on earth. For example, pollination is a natural service that allows plants to reproduce sexually when pollen grains are transferred from one plant to a receptive part of another plant. A great many of the earth’s
plant species depend on insects to pollinate their flowers. Insects that eat other insects help control the populations of at least half the species of insects we call pests. Some insects also play a key role in loosening and renewing the soil that supports terrestrial plant life. Insects have been around for at least 400 million years—about 2,000 times longer than the latest version of our own human species. Some insects reproduce at an astounding rate and can rapidly develop new genetic traits, such as resistance to pesticides. They also have an exceptional ability to evolve into new species when faced with changing environ-
as an ocean or as small as the intestine of a termite. Each habitat contains certain resources, such as water, and environmental conditions, such as temperature and light, that favor the organisms living there. A community, or biological community, consists of all the populations of different species that live in a particular place. For example, a catfish species in a pond usually shares the pond with other fishes, and with plants, insects, ducks, and many other species. Many of these organisms interact with one another during feeding and other activities. An ecosystem is a community of different species interacting with one another and with their nonliv-
Atmosphere Biosphere (living organisms) Soil Rock Crust
Mantle
Geosphere (crust, mantle, core)
Mantle Figure 2-9 Natural capital: This diagram illustrates the general structure of the earth, showing that it consists of a land sphere, an air sphere, a water sphere, and a life sphere.
32
Core
Atmosphere (air)
Hydrosphere (water)
CHAPTER 2
mental conditions, and they are very resistant to extinction. This is fortunate because, according to ant specialist and biodiversity expert E. O. Wilson, if all insects disappeared, parts of the life support systems that keep us and other species alive would be greatly disrupted. The environmental lesson: although insects do not need newcomer species such as humans, we and most other land organisms need them. Critical Thinking Identify three insect species that benefit your life. How do they do so?
ing environment of soil, water, other forms of matter, and energy, mostly from the sun. Ecosystems can range greatly in size, and they can be natural or artificial (human created). Examples of artificial ecosystems are crop fields and reservoirs. The biosphere consists of the parts of the earth’s air, water, and soil where life is found. In effect, it is the global ecosystem in which all ecosystems and living organisms exist and can interact with one another. In the biosphere, everything is linked to everything else.
Earth’s Life-Support System Has Four Major Components The earth’s life-support system consists of four main spherical systems that interact with one another (Figure 2-9). The atmosphere is a thin spherical envelope of gases surrounding the earth’s surface. Its inner layer, the troposphere, extends only about 17 kilometers (11 miles) above sea level at the tropics and about 7 kilometers (4 miles) above the earth’s north and south poles. It contains air that we breathe, consisting mostly of nitrogen (78% of the total volume) and oxygen (21%). The remaining 1% of the air includes water vapor, carbon dioxide, and methane, all of which are called greenhouse gases, which absorb and release energy that warms the lower atmosphere. Without these gases, the earth would be too cold for the existence of life as we know it. The next layer, stretching 17–50 kilometers (11–31 miles) above the earth’s surface, is called the stratosphere. Its lower portion holds enough ozone (O3) gas to filter out about 95% of the sun’s harmful ultraviolet (UV) radiation. This global sunscreen allows life to exist on land and in the surface layers of bodies of water. The hydrosphere consists of all of the water on or near the earth’s surface. It is found as water vapor in the atmosphere, liquid water on the surface and under-
Science, Matter, Energy, and Systems
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ground, and ice—polar ice, icebergs, glaciers, and ice in frozen soil layers called permafrost. The geosphere consists of the earth’s intensely hot core, a thick mantle composed mostly of rock, and a thin outer crust. Most of the geosphere is located in the earth’s interior. Its upper portion contains nonrenewable fossil fuels, such as coal, oil, and natural gas, and minerals that we use, as well as renewable soil chemicals that organisms need in order to live, grow, and reproduce. As noted above, the biosphere consists of the parts of the atmosphere, hydrosphere, and geosphere where life is found. Biologists have classified the terrestrial (land) portion of the biosphere into biomes—large regions such as forests, deserts, and grasslands, with distinct climates and certain species (especially vegetation) adapted to them. Scientists divide the watery parts of the biosphere into aquatic life zones, each containing numerous ecosystems. There are freshwater life zones (such as lakes and streams) and ocean or marine life zones (such as coral reefs, coastal estuaries, and the deep ocean). The biosphere extends from about 9 kilometers (6 miles) above the earth’s surface down to the bottom of the ocean and includes the lower part of the atmosphere, most of the hydrosphere, and the uppermost part of the geosphere. If the earth were an apple, the biosphere would be no thicker than the apple’s skin. One important goal of environmental science is to understand the interactions that occur within this thin layer of air, water, soil, and organisms.
Three Factors Sustain the Earth’s Life Life on the earth depends on three interconnected factors (Concept 2-4): 1. The one-way flow of high-quality energy from the sun, through living things in their feeding interactions,
into the environment as low-quality energy (mostly heat dispersed into air or water at a low temperature), and eventually back into space as heat. No round-trips are allowed because high-quality energy cannot be recycled. The two laws of thermodynamics (Concepts 2-3A and 2-3B) govern this energy flow. 2. The cycling of nutrients through parts of the biosphere. Because the earth is closed to significant inputs of matter from space, its essentially fixed supply of nutrients—the elements and compounds that organisms need in order to live, grow, and reproduce—must be continually recycled to support life (see Figure 1-4, p. 9). Nutrient cycles in ecosystems and in the biosphere are round-trips, which can take from seconds to centuries to complete. The law of conservation of matter (Concept 2-2B) governs this nutrient cycling process. 3. Gravity, which allows the planet to hold onto its atmosphere and helps to enable the movement and cycling of chemicals through air, water, soil, and organisms.
Sun, Earth, Life, and Climate Only a very small amount of the sun’s tremendous output of energy reaches the earth—a tiny sphere in the vastness of space. This energy reaches the earth in the form of electromagnetic waves, composed mostly of visible light, ultraviolet (UV) radiation, and heat (infrared radiation) (Figure 2-6). Much of this energy is absorbed or reflected back into space by the earth’s atmosphere and surface (Figure 2-10). About half of the total solar radiation intercepted by the earth reaches the planet’s surface, and most of it is then reflected back up toward space as longer-
Solar radiation
Radiated by atmosphere as heat
Reflected by atmosphere UV radiation Lower Stratosphere (ozone layer)
Most UV absorbed by ozone
Visible light
Absorbed by the earth
Troposphere
Heat added to troposphere
Figure 2-10 High-quality energy flows from the sun to the earth. As it interacts with the earth’s air, water, soil, and life, it is degraded into lower-quality energy (heat), some of which flows back into space.
Heat radiated by the earth
Greenhouse effect
CONCEPT 2-4 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
33
wavelength infrared radiation. In the lower atmosphere, it encounters greenhouse gases such as water vapor, carbon dioxide, methane, nitrous oxide, and ozone. It causes these gaseous molecules to vibrate and release infrared radiation with even longer wavelengths. The
What Are the Major Components of an Ecosystem?
2-5
▲
C O NC EPT 2-5 Ecosystems contain nonliving and living components, including organisms that produce the nutrients they need, organisms that get the nutrients they need by consuming other organisms, and organisms that recycle nutrients by decomposing the wastes and remains of other organisms.
Ecosystems Have Living and Nonliving Components The biosphere and its ecosystems are made up of biotic, or living components and abiotic, or nonliving components. Examples of nonliving components are water, air, nutrients, rocks, heat, and solar energy. Living components include plants, animals, and microbes. Figure 2-11 is a greatly simplified diagram of some of the living and nonliving components of a terrestrial ecosystem. Oxygen (O2)
Precipitaton
Carbon dioxide (CO2)
Producer
Secondary consumer (fox) Primary consumer (rabbit)
Producers Water
Decomposers Soluble mineral nutrients
Figure 2-11 Key living and nonliving components of an ecosystem in a field interact in many ways in this small portion of the biosphere.
34
vibrating gaseous molecules then have higher kinetic energy, which helps to warm the lower atmosphere and the earth’s surface. Without this natural greenhouse effect, the earth would be too cold to support the forms of life we find here today.
CHAPTER 2
Each population in an ecosystem has a range of tolerance to variations in its physical and chemical environment (Figure 2-12). Individuals within a population may also have slightly different tolerance ranges for temperature or other factors because of small differences in genetic makeup, health, and age. For example, a trout population may do best within a narrow band of temperatures (optimum level or range), but a few individuals can survive above and below that band. Of course, if the water becomes much too hot or too cold, none of the trout can survive. A variety of abiotic factors can affect the number of organisms in a population. Sometimes one factor, known as a limiting factor, limits the growth, abundance, or distribution of a population of a species within an ecosystem because there is too little or too much of that factor in the ecoystem. This leads to the limiting factor principle: Too much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance. This principle describes one way in which populations are controlled in natural systems. On land, precipitation often is the limiting abiotic factor. Lack of water in a desert limits plant growth. Soil nutrients also can act as a limiting factor on land. Suppose a farmer plants corn in phosphorus-poor soil. Even if water, nitrogen, potassium, and other nutrients are at optimal levels, the corn will stop growing when it uses up the available phosphorus. Too much of an abiotic factor can also be limiting. For example, too much water or fertilizer can kill plants. Important limiting abiotic factors in aquatic life zones include temperature, sunlight, nutrient availability, and dissolved oxygen content—the amount of oxygen gas dissolved in a given volume of water at a particular temperature and pressure. Another such factor is salinity—the amounts of various inorganic minerals or salts dissolved in a given volume of water.
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Lower limit of tolerance Few organisms
Abundance of organisms
Few organisms
No organisms
Figure 2-12 Range of tolerance for a population of organisms, such as fishes, to an abiotic environmental factor—in this case, temperature. These restrictions keep particular species from taking over an ecosystem by keeping their population sizes in check.
Population size
No organisms
Higher limit of tolerance
Zone of Zone of intolerance physiological stress Low
Optimum range
Temperature
Producers and Consumers Are the Living Components of Ecosystems Ecologists assign every type of organism in an ecosystem to a feeding level, or trophic level, depending on its source of food or nutrients. We can broadly classify the living organisms that transfer energy and nutrients from one trophic level to another in an ecosystem as producers and consumers. Producers, sometimes called autotrophs (selffeeders), make the nutrients they need from compounds and energy obtained from their environment (Concept 2-5). On land, most producers are green plants. In aquatic ecosystems, algae and aquatic plants growing near shorelines are the major producers. In open water, the dominant producers are phytoplankton—mostly microscopic organisms that float or drift in the water. In a process called photosynthesis, plants typically capture about 1% of the solar energy that falls on their leaves and combine it with carbon dioxide and water to form organic molecules, including energy-rich carbohydrates (such as glucose, C6H12O6), which store the chemical energy they need. Although hundreds of chemical changes take place during photosynthesis, we can summarize the overall reaction as follows: carbon dioxide + water + solar energy
glucose + oxygen
All other organisms in an ecosystem are consumers, or heterotrophs (“other-feeders”), that cannot produce their own nutrients and must obtain them by feeding on other organisms (producers or other consumers) or their remains. In other words, all consumers (including humans) depend on producers for their nutrients.
Zone of Zone of physiological intolerance stress High
There are several types of consumers. Primary consumers, or herbivores (plant eaters), are animals such as caterpillars and giraffes that eat producers. Carnivores (meat eaters) are animals that feed on the flesh of other animals. Some carnivores such as spiders, lions, and most small fishes are secondary consumers that feed on the flesh of herbivores. Other carnivores such as tigers and killer whales are tertiary (or higher-level) consumers that feed on the flesh of other carnivores. Omnivores such as pigs, rats, and humans eat plants and other animals. Decomposers are consumers that, in the process of obtaining their own nutrients, release nutrients from the wastes or remains of plants and animals that then go back to the soil, water, and air for reuse as nutrients by producers (Concept 2-5). Most decomposers are bacteria and fungi. Other consumers, called detritus feeders, or detritivores, feed on the wastes or dead bodies of other organisms; these wastes are called detritus (dee-TRI-tus), which means debris. Examples are earthworms, some insects, and vultures. Hordes of detritus feeders and decomposers can transform a fallen tree trunk into wood particles and, finally, into simple inorganic molecules that plants can absorb as nutrients (Figure 2-13, p. 36). Thus, in natural ecosystems the wastes and dead bodies of organisms serve as resources for other organisms, as the nutrients that make life possible are continuously recycled, in keeping with one of the three principles of sustainability (see back cover). As a result, there is very little waste of nutrients in nature. Decomposers and detritus feeders, many of which are microscopic organisms (Science Focus, p. 36), are the key to nutrient cycling. Without them, the planet would be overwhelmed with plant litter, animal wastes, dead animal bodies, and garbage.
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Figure 2-13 Various detritivores and decomposers (mostly fungi and bacteria) can “feed on” or digest parts of a log and eventually convert its complex organic chemicals into simpler inorganic nutrients that can be taken up by producers.
Decomposers
Detritus feeders
Long-horned beetle holes
Bark beetle engraving
Carpenter ant galleries
Termite and carpenter ant work
Dry rot fungus
Wood reduced to powder
Time progression
Producers, consumers, and decomposers use the chemical energy stored in glucose and other organic compounds to fuel their life processes. In most cells, this energy is released by aerobic respiration, which uses oxygen to convert organic nutrient back into carbon dioxide and water. The net effect of the hundreds of steps in this complex process is represented by the following chemical reaction: glucose + oxygen
carbon dioxide + water + energy
Fungi
Powder broken down by decomposers into plant nutrients in soil
Although the detailed steps differ, the net chemical change for aerobic respiration is the opposite of that for photosynthesis. To summarize, ecosystems and the biosphere are sustained through a combination of one-way energy flow from the sun through these systems and the nutrient cycling that takes place within them (Concept 2-4)—in keeping with two of the principles of sustainability (Figure 2-14).
SCIE N C E FO C US Many of the World’s Most Important Organisms Are Invisible to Us
T
hey are everywhere. Billions can be found inside your body, on your body, in a handful of soil, and in a cup of ocean water. These mostly invisible rulers of the earth are microbes, or microorganisms, catchall terms for many thousands of species of bacteria, protozoa, fungi, and floating phytoplankton—most too small to be seen with the naked eye. Microbes do not get the respect they deserve. Most of us view them primarily as threats to our health in the form of infectious bacteria or “germs,” fungi that cause athlete’s foot and other skin diseases, and protozoa that cause diseases such as malaria. But these harmful microbes are in the minority. We are alive largely because of multitudes of microbes toiling away completely out of sight. Bacteria in our intestinal tracts help
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break down the food we eat, and microbes in our noses help prevent harmful bacteria from reaching our lungs. Bacteria and other microbes help to purify the water we drink by breaking down plant and animal wastes that may be in the water. Bacteria also help to produce foods such as bread, cheese, yogurt, soy sauce, beer, and wine. Bacteria and fungi in the soil decompose organic wastes into nutrients that can be taken up by the plants that humans and most other animals eat. Without these tiny creatures, we would go hungry and be up to our necks in waste matter. Microbes, particularly phytoplankton in the ocean, provide much of the planet’s oxygen, and help to regulate the earth’s temperature by removing some of the carbon dioxide produced when we burn coal, natural gas,
and gasoline. Scientists are working on using microbes to develop new medicines and fuels. Genetic engineers are inserting genetic material into existing microorganisms to convert them to microbes that can be used to clean up polluted water and soils. Some microorganisms help to control diseases that affect plants and to control populations of insect species that attack our food crops. Relying more on these microbes for pest control could reduce the use of potentially harmful chemical pesticides. In other words, microbes are a vital part of the earth’s natural capital. Critical Thinking What are three advantages that microbes have over humans for thriving in the world?
Science, Matter, Energy, and Systems
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Heat
Heat
Heat
Producers (plants)
Decomposers (bacteria, fungi)
Consumers (plant eaters, meat eaters)
Heat
2-6
Solar energy
Chemical nutrients (carbon dioxide, oxygen, nitrogen, minerals)
Figure 2-14 Natural capital: This diagram shows the main structural components of an ecosystem (energy, chemicals, and organisms). Nutrient cycling and the flow of energy—first from the sun, then through organisms, and finally into the environment as low-quality heat—link these components.
Heat
What Happens to Energy in an Ecosystem?
▲
As energy flows through ecosystems in food chains and webs, the amount of chemical energy available to organisms at each successive feeding level decreases.
CONC EPT 2-6
Energy Flows through Ecosystems in Food Chains and Food Webs All organisms, whether dead or alive, are potential sources of food for other organisms. A caterpillar eats a leaf, a robin eats the caterpillar, and a hawk eats the robin. Decomposers and detritus feeders consume the leaf, caterpillar, robin, and hawk after they die and return their nutrients to the soil for reuse by producers. Such a sequence of organisms, each of which serves as a source of food or energy for the next, is called a food chain. It determines how chemical energy and nutrients move along the same pathways from one organism to another through the trophic levels in an ecosystem—primarily through photosynthesis, feeding, and decomposition—as shown in Figure 2-15 (p. 38). Every use and transfer of energy by organisms involves a loss of some degraded high-quality energy to the environment as heat. In natural ecosystems, most consumers feed on more than one type of organism, and most organisms are eaten or decomposed by more than one type of consumer. Because of this, organisms in most ecosystems
form a complex network of interconnected food chains called a food web (Figure 2-16, p. 38). We can assign trophic levels in food webs just as we can in food chains. Food chains and webs show how producers, consumers, and decomposers are connected to one another as energy flows through trophic levels in an ecosystem.
Usable Energy Decreases with Each Link in a Food Chain or Web Each trophic level in a food chain or web contains a certain amount of biomass, the dry weight of all organic matter contained in its organisms. In a food chain or web, chemical energy stored in biomass is transferred from one trophic level to another. With each transfer, some usable chemical energy is degraded and lost to the environment as low-quality heat. In other words, as energy flows through ecosystems in food chains and webs, there is a decrease in the amount of high-quality chemical energy available to organisms at each succeeding feeding level (Concept 2-6).
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37
Figure 2-15 This diagram illustrates a food chain. The arrows show how the chemical energy in nutrients flows through various trophic levels in energy transfers; most of the energy is degraded to heat, in accordance with the second law of thermodynamics (Concept 2-3B). Question: Think about what you Solar Solar ate for breakenergy energy fast. At what level or levels on a food chain were you eating?
First Trophic Level
Second Trophic Level
Third Trophic Level
Fourth Trophic Level
Producers (plants)
Primary consumers (herbivores)
Secondary consumers (carnivores)
Tertiary consumers (top carnivores)
Heat
Heat
Heat
Heat
Heat
Heat
Heat
Decomposers and detritus feeders
Humans
Sperm whale
Blue whale
Elephant seal Crabeater seal
Killer whale
Leopard seal Emperor penguin
Adelie penguin
Squid Petrel
Fish
Figure 2-16 This diagram illustrates a greatly simplified food web in the southern hemisphere. The shaded middle area shows a simple food chain. Many more participants in the web, including an array of decomposer and detritus feeder organisms, are not shown here. Question: Can you imagine a food web of which you are a part? Try drawing a simple diagram of it.
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Carnivorous zo zoo zooplankton oplankton Herbivorous zooplankton
Krill
Phytoplankton
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Usable energy available at each trophic level (in kilocalories) Tertiary consumers (human)
10
Secondary consumers (perch)
100
Primary consumers (zooplankton)
Heat
Heat
Heat
Decomposers
Heat
Figure 2-17 This model of a generalized pyramid of energy flow shows the decrease in usable chemical energy available at each succeeding trophic level in a food chain or web. The model assumes that with each transfer from one trophic level to another, there is a 90% loss in usable energy to the environment in the form of lowquality heat. (Note that the examples of species listed in parentheses following each label on the left side of this diagram represent a food chain.) Question: Why is a vegetarian diet more energy efficient than a meat-based diet?
1,000 Heat 10,000
Producers (phytoplankton)
The percentage of usable chemical energy transferred as biomass from one trophic level to the next is called ecological efficiency. It varies, depending on what types of species and ecosystems are involved, but 10% is typical. The more trophic levels there are in a food chain or web, the greater is the cumulative loss of usable chemical energy as it flows through the trophic levels. The pyramid of energy flow in Figure 2-17 illustrates this energy loss for a simple food chain, assuming a 90% energy loss with each transfer. Energy flow pyramids explain why the earth can support more people if they eat at lower trophic levels by consuming grains, vegetables, and fruits directly, rather than passing such crops through another trophic level and eating grain eaters or herbivores such as cattle. The large loss in chemical energy between successive trophic levels also explains why food chains and webs rarely have more than four or five trophic levels. In most cases, too little chemical energy is left after four or five transfers to support organisms feeding at these high trophic levels.
Some Ecosystems Produce Plant Matter Faster Than Others Do The amount, or mass, of living organic material (biomass) that a particular ecosystem can support is determined by how much solar energy its producers can capture and store as chemical energy and by how rapidly they can do so. Gross primary productivity (GPP) is the rate at which an ecosystem’s producers (usually plants) convert solar energy into chemical energy in the form of the biomass found in their tissues. To stay alive, grow, and reproduce, producers must use some of the chemical energy stored in the biomass
they make for their own respiration. Net primary productivity (NPP) is the rate at which producers use photosynthesis to produce and store chemical energy minus the rate at which they use some of this stored chemical energy through aerobic respiration. NPP is a measure of how fast producers can make the chemical energy that is stored in their tissues and is potentially available to other organisms (consumers) in an ecosystem. Ecosystems and life zones differ in their NPP as illustrated in Figure 2-18 (p. 40). Despite its low NPP, the open ocean produces more of the earth’s biomass per year than any other ecosystem or life zone, simply because there is so much open ocean containing huge numbers of producers such as tiny phytoplankon. On land, tropical rain forests have a very high net primary productivity because of their large number and variety of producer trees and other plants. When such forests are cleared or burned to plant crops or graze cattle, there is a sharp drop in the net primary productivity and a loss of many of the diverse array of plant and animal species. As we have seen, producers are the source of all nutrients in an ecosystem that are available for the producers themselves and for the consumers and decomposers that feed on them. Only the biomass represented by NPP is available as nutrients for consumers, and they use only a portion of this amount. Thus, the planet’s NPP ultimately limits the number of consumers (including humans) that can survive on the earth. This is an important lesson from nature. Peter Vitousek, Stuart Rojstaczer, and other ecologists estimate that humans now use, waste, or destroy 10–55% of the earth’s total potential NPP. This is a remarkably high value, considering that the human population makes up less than 1% of the total biomass of all of the earth’s consumers that depend on producers for their nutrients. CONCEPT 2-6
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Terrestrial Ecosystems Swamps and marshes Tropical rain forest Temperate forest Northern coniferous forest (taiga) Savanna Agricultural land Woodland and shrubland Temperate grassland Tundra (arctic and alpine) Desert scrub Extreme desert Aquatic Ecosystems Estuaries Lakes and streams Continental shelf Open ocean 800
1,600
2,400 3,200 4,000 4,800 5,600 6,400 7,200 Average net primary productivity (kcal/m2/yr)
8,000
8,800
9,600
Figure 2-18 The estimated annual average net primary productivity in major life zones and ecosystems is expressed in this graph as kilocalories of energy produced per square meter per year (kcal/m2/yr). Question: What are nature’s three most productive and three least productive systems? (Data from R. H. Whittaker, Communities and Ecosystems, 2nd ed., New York: Macmillan, 1975)
2-7 ▲
40
What Happens to Matter in an Ecosystem?
C O NC EPT 2-7 Matter, in the form of nutrients, cycles within and among ecosystems throughout the biosphere, and human activities are altering these chemical cycles.
Nutrients Cycle in the Biosphere
The Water Cycle
The elements and compounds that make up nutrients move continually through air, water, soil, rock, and living organisms within ecosystems, as well as in the biosphere in cycles called biogeochemical cycles (literally, life-earth-chemical cycles), or nutrient cycles. This is in keeping with one of the three principles of sustainability (see back cover). These cycles, driven directly or indirectly by incoming solar energy and the earth’s gravity, include the hydrologic (water), carbon, nitrogen, phosphorus, and sulfur cycles. Nutrient cycles connect past, present, and future forms of life. Some of the carbon atoms in your skin may once have been part of an oak leaf, a dinosaur’s skin, or a layer of limestone rock. Your grandmother, your favorite rock star, or a hunter–gatherer who lived 25,000 years ago may have inhaled some of the nitrogen molecules you just inhaled.
The hydrologic cycle, or water cycle, collects, purifies, and distributes the earth’s fixed supply of water, as shown in Figure 2-19. The water cycle is a global cycle because there is a large reservoir of water in the atmosphere as well as in the hydrosphere, especially the oceans. Water is an amazing substance, which makes the water cycle critical to life on earth. The water cycle is powered by energy from the sun and involves three major processes—evaporation, precipitation, and transpiration. Incoming solar energy causes evaporation—the changing of liquid water into water vapor in the atmosphere—from the earth’s oceans, lakes, rivers, and soil. Gravity draws some of the water vapor from the atmosphere back to the earth’s surface as rain, snow, sleet, and dew—a process called precipitation. Over land, about 90% of the water that reaches the atmosphere evaporates from the surfaces
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Condensation
Condensation Ice and snow
Transpiration from plants Precipitation to land
Evaporation of surface water
Evaporation from ocean
Runoff Lakes and reservoirs
Precipitation to ocean Runoff
Infiltration and percolation into aquifer
Increased runoff on land covered with crops, buildings and pavement Increased runoff from cutting forests and filling wetlands
Runoff
Groundwater in aquifers
Overpumping of aquifers
Water pollution Runoff
Ocean
Natural process Natural reservoir Human impacts Natural pathway Pathway affected by human activities Figure 2-19 Natural capital: This is a simplified model of the water cycle, or hydrologic cycle, in which water circulates in various forms within the biosphere. Major harmful impacts of human activities are shown by the white arrows. Question: What are three ways in which your lifestyle directly or indirectly affects the hydrologic cycle?
of plants—a process called transpiration—and from the soil. Water returning to the earth’s surface as precipitation takes various paths. Most precipitation falling on terrestrial ecosystems becomes surface runoff. This water flows into streams and lakes, which eventually carry the water back to the oceans, from which it can evaporate to repeat the cycle. Some surface water seeps into the upper layer of soils and some evaporates from soil, lakes, and streams back into the atmosphere. Some precipitation is converted to ice that is stored in glaciers, usually for long periods of time. Some precipitation sinks through soil and permeable rock formations
to underground layers of rock, sand, and gravel called aquifers, where it is stored as groundwater. In addition, a small amount of the earth’s water ends up in the living components of ecosystems—plants that absorb some of this water through their roots, and consumers that drink it or get it by eating plants. Because water dissolves many nutrient compounds, it is a major medium for transporting nutrients within and between ecosystems. It also causes soil erosion by moving soil and rock fragments from one place to another. And water is the primary sculptor of the earth’s landscape as it flows over and wears down rock over millions of years. CONCEPT 2-7
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Throughout the hydrologic cycle, many natural processes purify water. Evaporation and subsequent precipitation act as a natural distillation process that removes impurities dissolved in water. Water flowing above ground through streams and lakes, and below ground in aquifers is naturally filtered and partially purified by chemical and biological processes. Thus, the hydrologic cycle can be viewed as a cycle of natural renewal of water quality. Only about 0.024% of the earth’s vast water supply is available to humans and other species as liquid freshwater in accessible groundwater deposits and in lakes, rivers, and streams. The rest is too salty for us to use, is stored as ice, or is too deep underground to extract.
Human Activities Have Major Effects on the Water Cycle
Second, we clear vegetation from land for agriculture, mining, road building, and other activities, and cover much of the land with buildings, concrete, and asphalt. This increases runoff, reduces the amount of water seeping into the ground that would normally recharge groundwater supplies, accelerates topsoil erosion, and increases the risk of flooding. Third, we increase flooding when we drain wetlands for farming and urban development. Left undisturbed, wetlands provide the natural service of flood control, acting like sponges to absorb and hold overflows of water from drenching rains or rapidly melting snow. We also cover much of the land with roads, parking lots, and buildings, eliminating the land’s ability to absorb water and dramatically increasing the risk of flooding.
The Carbon Cycle
We alter the water cycle in three major ways. First, we withdraw large quantities of freshwater from streams, lakes, and underground sources, sometimes at rates faster than nature can replace it.
Carbon is the basic building block of the carbohydrates, fats, proteins, DNA, and other organic compounds necessary for life. Various compounds of carbon circulate through the biosphere, the atmosphere, and parts of the hydrosphere, in the carbon cycle shown in Figure 2-20.
Carbon dioxide in atmosphere
Respiration Photosynthesis
Animals (consumers) Diffusion
Burning fossil fuels
Forest fires
Plants (producers)
Deforestation
Transportation
Respiration Carbon in plants (producers)
Figure 2-20 Natural capital: This simplified model illustrates the circulation of various chemical forms of carbon in the global carbon cycle, with major harmful impacts of human activities shown by the white arrows. Question: What are three ways in which you directly or indirectly affect the carbon cycle?
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Carbon in animals (consumers)
Carbon dioxide dissolved in ocean
Decomposition Carbon in fossil fuels
Marine food webs Producers, consumers, decomposers
Carbon in limestone or dolomite sediments
Compaction
Process Reservoir Pathway affected by humans Natural pathway
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The carbon cycle is based on carbon dioxide (CO2) gas, which makes up 0.038% of the volume of the earth’s atmosphere and is also dissolved in water. Carbon dioxide is a key component of the atmosphere’s thermostat. If the carbon cycle removes too much CO2 from the atmosphere, the atmosphere will get cooler, and if it generates too much CO2, the atmosphere will get warmer. Thus, even slight changes in this cycle caused by natural or human factors can affect the earth’s climate and ultimately help to determine the types of life that can exist in various places. Terrestrial producers remove CO2 from the atmosphere and aquatic producers remove it from the water. These producers then use photosynthesis to convert CO2 into complex carbohydrates such as glucose (C6H12O6). The cells in oxygen-consuming producers, consumers, and decomposers then carry out aerobic respiration. This process breaks down glucose and other complex organic compounds to produce CO2 in the atmosphere and water for reuse by producers. This linkage between photosynthesis in producers and aerobic respiration in producers, consumers, and decomposers circulates carbon in the biosphere. Oxygen and hydrogen—the other elements in carbohydrates—cycle almost in step with carbon. Some carbon atoms take a long time to recycle. Over millions of years, buried deposits of dead plant matter and bacteria are compressed between layers of sediment, where high pressure and heat convert them to carbon-containing fossil fuels. This carbon is not released to the atmosphere as CO2 for recycling until these fuels are extracted and burned, or until long-term geological processes expose these deposits to air. However, within the past three centuries, humans have mined coal and pumped oil and natural gas and burned these fuels at increasing rates. In only a few hundred years, we have extracted and burned huge quantities of fossil fuels that took millions of years to form. This is why, on a human time scale, fossil fuels are nonrenewable resources.
Human Activities Affect the Carbon Cycle Since 1800, and especially since 1950, we have been intervening in the earth’s carbon cycle by adding carbon dioxide to the atmosphere in two ways. First, in some areas we clear trees and other plants, which absorb CO2 through photosynthesis, faster than they can grow back. Second, we add large amounts of CO2 to the atmosphere by burning carbon-containing fossil fuels and wood. Computer models of the earth’s climate systems indicate that increased concentrations of atmospheric CO2 and other greenhouse gases such as methane (CH4) are very likely to enhance the planet’s natural greenhouse effect, which will add to atmospheric warming and thus to climate disruption during this century, as we discuss in Chapter 12.
The Nitrogen Cycle: Bacteria in Action Nitrogen is the atmosphere’s most abundant element, making up 78% of the volume of the atmosphere. Nitrogen is a crucial component of proteins and vitamins, but it cannot be absorbed and used directly as a nutrient by multicellular plants or animals. Fortunately, two natural processes convert, or fix, nitrogen gas (N2) into compounds that plants and animals can use as nutrients. One is electrical discharges, or lightning, that take place in the atmosphere. The other takes place in aquatic systems, soil, and the roots of some plants, where nitrogen-fixing bacteria complete this conversion as part of the nitrogen cycle, which is depicted in Figure 2-21 (p. 44). The nitrogen cycle consists of several major steps. In nitrogen fixation, specialized bacteria combine gaseous N2 with hydrogen to make ammonia (NH3), some of which is converted to ammonium ions (NH4+) that plants can use as a nutrient. Ammonia not taken up by plants may undergo nitrification. In this process, specialized soil bacteria convert most of the ammonia in soil, first to nitrite ions (NO2–), which are toxic to plants, and then to nitrate ions (NO3–), which are easily taken up by the roots of plants. Animals that eat plants eventually consume these nitrogen-containing compounds, as do detritus feeders and decomposers. Plants and animals return nitrogen-rich organic compounds to the environment as both wastes and castoff particles of tissues such as leaves, skin, or hair, and through their bodies when they die. In ammonification, vast armies of specialized decomposer bacteria convert this detritus into simpler nitrogen-containing inorganic compounds such as ammonia (NH3) and water-soluble salts containing ammonium ions (NH4+). In denitrification, specialized bacteria in waterlogged soil and in the bottom sediments of lakes, oceans, swamps, and bogs convert NH3 and NH4+ back into nitrate ions, and then into nitrogen gas (N2) and nitrous oxide gas (N2O). These gases are released to the atmosphere to begin the nitrogen cycle again.
Human Activities Affect the Nitrogen Cycle We intervene in the nitrogen cycle in five ways. First, we add large amounts of nitric oxide (NO) into the atmosphere when we burn any fuel. In the atmosphere, this gas can be converted to nitrogen dioxide gas (NO2) and nitric acid vapor (HNO3), which can return to the earth’s surface as damaging acid deposition, commonly called acid rain. These chemicals also are components of the smog that pollutes the air over many cities. Second, we add nitrous oxide (N2O) to the atmosphere through the action of anaerobic bacteria on commercial inorganic fertilizer and on organic animal CONCEPT 2-7
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Process Nitrogen in atmosphere
Reservoir
Denitrification by bacteria Nitrification by bacteria
Pathway affected by humans Natural pathway Nitrogen in animals (consumers)
Electrical storms Nitrogen oxides from burning fuel and using inorganic fertilizers
Volcanic activity Nitrogen in plants (producers) Decomposition
Nitrates from fertilizer runoff and decomposition
Uptake by plants
Nitrate in soil Nitrogen loss to deep ocean sediments
Nitrogen in ocean sediments
Bacteria Ammonia in soil
Figure 2-21 Natural capital: This is a simplified model of the circulation of various chemical forms of nitrogen in the nitrogen cycle in a terrestrial ecosystem, with major harmful human impacts shown by the white arrows. Question: What are three ways in which you directly or indirectly affect the nitrogen cycle?
manure applied to the soil. This greenhouse gas can warm the atmosphere and deplete stratospheric ozone, which keeps most of the sun’s harmful ultraviolet radiation from reaching the earth’s surface. Third, we release large quantities of nitrogen stored in soils and plants as gaseous compounds into the atmosphere through destruction of forests, grasslands, and wetlands. Fourth, we upset the nitrogen cycle in aquatic ecosystems by adding excess nitrates to bodies of water through agricultural runoff and through discharges from municipal sewage systems. And fifth, we remove nitrogen from topsoil when we harvest nitrogen-rich crops, irrigate crops (washing nitrates out of the soil), and burn or clear grasslands and forests before planting crops. According to the 2005 Millennium Ecosystem Assessment, since 1950, human activities have more than doubled the annual release of nitrogen from the land into the rest of the environment and the amount released is projected to double again by 2050. This excessive input of nitrogen into the air and water contributes to pollution and other problems to be discussed in later chapters.
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The Phosphorus Cycle and Human Interference with It Phosphorus is a key component of DNA and energy storage molecules in cells, and is a major component of vertebrate bones and teeth. Compounds of phosphorous circulate through water, the earth’s crust, and living organisms in the phosphorus cycle, depicted in Figure 2-22. In contrast to the cycles of water, carbon, and nitrogen, the phosphorus cycle does not include the atmosphere, and it is a slower cycle. As water runs over exposed phosphorus-containing rocks, it slowly erodes away inorganic compounds that contain phosphate ions (PO43–). The running water carries these dissolved phosphate ions into the soil where they can be absorbed by the roots of plants. Phosphate compounds are also transferred by food webs from producers to consumers to decomposers. Phosphate can be lost from the cycle for long periods of time when it is washed from the land into streams and rivers and carried to the ocean. There it can be deposited as marine sediment and remain trapped for
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Process Reservoir Pathway affected by humans Natural pathway Phosphates in sewage Phosphates in mining waste
Phosphates in fertilizer
Plate tectonics
Runoff
Runoff
Sea birds Runoff Erosion
Animals (consumers)
Phosphate dissolved in water
Phosphate in rock (fossil bones, guano)
Ocean food webs
Phosphate in shallow ocean sediments Phosphate in deep ocean sediments
Plants (producers)
Bacteria
Figure 2-22 Natural capital: This is a simplified model of the circulation of various chemical forms of phosphorus in the phosphorus cycle, with major harmful human impacts shown by the white arrows. Question: What are three ways in which you directly or indirectly affect the phosphorus cycle?
millions of years. Someday, geological processes may uplift and expose these seafloor deposits, from which phosphate can be eroded to start the cycle again. Because most soils contain little phosphate, the lack of it is often the limiting factor for plant growth on land unless phosphorus (as phosphate salts mined from the earth) is applied to the soil as a fertilizer. Lack of phosphorus also limits the growth of producer populations in many freshwater streams and lakes because phosphate salts are only slightly soluble in water and thus do not release many phosphate ions that producers need as nutrients. Human activities are affecting the phosphorous cycle in three ways. First, we remove large amounts of phosphate from the earth to make fertilizers, detergents, and other products. Second, we reduce phosphorus in tropical soils by clearing tropical forests. Third, soil that is eroded from fertilized crop fields carries large quantities of phosphates into aquatic systems where they can stimulate growth of huge populations of algae, which can upset chemical cycling and other aquatic system processes. Similarly, phosphates washed off of fertilized urban lawns and golf courses also can flow into aquatic systems.
Earth’s Rocks Are Recycled Very Slowly Rock is any material that makes up a large, natural, continuous part of the earth’s crust. Based on the way it forms, rock is placed in three broad classes. One is igneous rock, formed below or on the earth’s surface when molten rock material (magma) wells up from the earth’s upper mantle or deep crust, cools, and hardens into rock. Examples are granite (formed underground) and lava rock (formed above ground when molten lava cools and hardens). A second type is sedimentary rock, formed from sediment when existing rocks are weathered and eroded into small pieces and carried by wind and water to be deposited in lakes and rivers. As these deposited sediments become buried and compacted, the resulting pressure causes their particles to bond together to form sedimentary rocks such as sandstone and shale. The third type is metamorphic rock, produced when an existing rock is subjected to high temperatures (which may cause it to melt partially), high pressures, chemically active fluids, or a combination of these agents. Examples are anthracite (a form of coal), slate, and marble. CONCEPT 2-7
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Erosion Transportation
Weathering Deposition
Igneous rock Granite, pumice, basalt
Sedimentary rock Sandstone, limestone
Heat, pressure
Cooling Heat, pressure, stress
Magma (molten rock)
Melting
Metamorphic rock Slate, marble, gneiss, quartzite Figure 2-23 Natural capital: The rock cycle is the slowest of the earth’s cyclic processes. Rocks are recycled over millions of years by three processes: melting, erosion, and metamorphism, which produce igneous, sedimentary, and metamorphic rocks. Rock from any of these classes can be converted to rock of either of the other two classes, or it can be recycled within its own class. Question: What are three ways in which the rock cycle benefits your lifestyle?
Rocks are constantly exposed to various physical and chemical conditions that can change them over time. The interaction of processes that change rocks from one type to another is called the rock cycle (Figure 2-23). The rock cycle recycles the earth’s three types of rocks over millions of years and is the slowest of the earth’s cyclic processes. It concentrates the planet’s nonrenewable mineral resources on which we depend. Without the incredibly slow rock cycle, you would not exist.
Revisiting the Principles of Sustainability This chapter applied the principles of sustainability (see back cover) by which the biosphere and the ecosystems it contains have been sustained over the long term. First, the biosphere and almost all of its ecosystems use solar energy as their energy source and this energy flows through the biosphere. Second, they
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CHAPTER 2
recycle the chemical nutrients that their organisms need for survival, growth, and reproduction. These two principles arise from the structure and function of natural ecosystems, the law of conservation of matter (Concept 2-2B), and the two laws of thermodynamics (Concepts 2-3A and 2-3B). Nature’s adherence to these two principles is enhanced by biodiversity, a third principle of sustainability, which we explore in the next chapter. Here are this chapter’s three big ideas: ■ According to the law of conservation of matter, no atoms are created or destroyed whenever matter undergoes a physical or chemical change. ■ According to the laws of thermodynamics, whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed, and we always end up with lowerquality or less usable energy than we started with. ■ Life is sustained by the flow of energy from the sun through the biosphere, the cycling of nutrients within the biosphere, and gravity.
Science, Matter, Energy, and Systems
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The second law of thermodynamics holds, I think, the supreme position among laws of nature. . . . If your theory is found to be against the second law of thermodynamics, I can give you no hope. ARTHUR S. EDDINGTON
REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 21. What is science? Describe the steps involved in the scientific process. What is data? What is an experiment? What is a model? Distinguish among a scientific hypothesis, a scientific theory, and a scientific law (law of nature). Describe the overall scientific method. What is peer review and why is it important? Explain why scientific theories are not to be taken lightly and why people often use the term theory incorrectly. 2. Distinguish among tentative science (frontier science), reliable science, and unreliable science. What are five limitations of science and environmental science? Describe statistics and probability, and briefly describe how they are used in science. 3. What is matter? Distinguish between an element and a compound and give an example of each. Distinguish among an atom, an ion, and a molecule and give an example of each. What is the atomic theory? Distinguish among a proton (p), a neutron (n), and an electron (e). What is the nucleus of an atom? Define and distinguish between the atomic number and the mass number of an element. What is an isotope? What is a chemical formula? Define acidity and explain what pH values are and how they are used. Distinguish between organic compounds and inorganic compounds and give an example of each. Distinguish among complex carbohydrates, proteins, nucleic acids, and lipids. 4. Distinguish among genes, traits, and chromosomes. What is a cell? What is matter quality? Distinguish between high-quality matter and low-quality matter and give an example of each. Distinguish between a physical change and a chemical change (chemical reaction) and give an example of each. What is the law of conservation of matter and why is it important? 5. What is energy? Distinguish between kinetic energy and potential energy and give an example of each. What is heat? Define and give two examples of electromagnetic radiation. What is energy quality? Distinguish between high-quality energy and low-quality energy and give an example of each. State the law of conservation of energy (first law of thermodynamics) and explain its importance. What is the second law of thermodynamics and why is it important? Explain why the second law means that we can never recycle or reuse high-quality energy.
6. What is ecology? Define organism and species. Why are insects important? Distinguish among a population, a habitat, and a biological community, and give an example of each. What is genetic diversity? Define and describe the relationships among ecosystems, biomes, aquatic life zones, and the biosphere. Distinguish between the atmosphere, the troposphere, and the stratosphere. Define greenhouse gases and give two examples. Distinguish between the hydrosphere and the geosphere. List and describe three major factors that sustain life on earth. Define nutrients. Describe the natural greenhouse effect and explain its importance. 7. Distinguish between biotic and abiotic components of the biosphere, and give two examples of each. Define range of tolerance. Define limiting factor and state the limiting factor principle. What is a trophic level? Distinguish among producers (autotrophs), consumers (heterotrophs), decomposers, and detritus feeders (detritivores), and give an example of each in an ecosystem. Distinguish among primary consumers (herbivores), carnivores, secondary consumers, tertiary consumers, and omnivores, and give an example of each. Define photosynthesis and aerobic respiration. Explain the importance of microbes. 8. Define and distinguish between a food chain and a food web. Explain what happens to energy as it flows through the food chains and food webs of an ecosystem. What is biomass? What is ecological efficiency? What is the pyramid of energy flow? Discuss the difference between gross primary productivity (GPP) and net primary productivity (NPP), and explain the importance of each. 9. What happens to matter in an ecosystem? What is a biogeochemical cycle (nutrient cycle)? Describe the hydrologic (water) cycle, and distinguish among evaporation, transpiration, and precipitation. Describe the carbon, nitrogen, and phosphorus cycles, and describe how human activities are affecting each cycle. 10. Define rock and describe the rock cycle. Define and distinguish among igneous, sedimentary, and metamorphic rock.
Note: Key terms are in bold type.
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CRITICAL THINKING 1. Describe a way in which you have applied the scientific process described in this chapter (Figure 2-1) in your own life, and state the conclusion you drew from this process. Describe a new problem that you would like to solve using this process. 2. Respond to the following statements: a. Scientists have not absolutely proven that anyone has ever died from smoking cigarettes. b. The natural greenhouse theory—that certain gases (such as water vapor and carbon dioxide) warm the lower atmosphere—is not a reliable idea because it is just a scientific theory. 3. A tree grows and increases its mass. Explain why this phenomenon is not a violation of the law of conservation of matter. 4. Use the second law of thermodynamics to explain why we can use a barrel of oil only once as a fuel, or in other words, why we cannot recycle high-quality energy.
5. Explain why (a) the flow of energy through the biosphere depends on the cycling of nutrients, and (b) the cycling of nutrients depends on gravity. 6. Make a list of the foods you ate for lunch or dinner today. Trace each type of food back to a particular producer species. Describe the sequence of feeding levels that led to your feeding. 7. What would happen to an ecosystem if (a) all its decomposers and detritus feeders were eliminated, (b) all its producers were eliminated, or (c) all of its insects were eliminated? Could a balanced ecosystem exist with only producers and decomposers and no consumers such as humans and other animals? Explain. 8. Why do farmers not need to apply carbon to grow their crops but often need to add fertilizer containing nitrogen and phosphorus?
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 2 for many study aids and ideas for further
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CHAPTER 2
reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
Science, Matter, Energy, and Systems
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3
Biodiversity and Evolution
Key Questions and Concepts 3-1
What is biodiversity and why is it important?
3-4
What are biomes and how have human activities affected them?
C O N C E P T 3 - 1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining life on earth.
CONCEPT 3-4A
Where do species come from?
3-2
Differences in average annual precipitation and temperature lead to the formation of tropical, temperate, and cold deserts, grasslands, and forests, and largely determine their locations. In many areas, human activities are impairing ecological and economic services provided by the earth’s deserts, grasslands, forests, and mountains.
CONCEPT 3-4B
According to the scientific theory of evolution through natural selection, populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits. CONCEPT 3-2
How do speciation, extinction, and human activities affect biodiversity?
3-3
C O N C E P T 3 - 3 As environmental conditions change, the balance between the formation of new species and the extinction of existing species determines the earth’s biodiversity.
3-5 What are aquatic life zones and how have human activities affected them? C O N C E P T 3 - 5 A The key factors determining biodiversity in aquatic systems are temperature, dissolved oxygen content, availability of food, and availability of light and nutrients necessary for photosynthesis. C O N C E P T 3 - 5 B Human activities threaten aquatic biodiversity and disrupt ecological and economic services provided by saltwater and freshwater systems.
There is grandeur to this view of life . . . that, whilst this planet has gone cycling on . . . endless forms most beautiful and most wonderful have been, and are being, evolved. CHARLES DARWIN
Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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3-1
What Is Biodiversity and Why Is It Important?
▲
C O NC EPT 3-1 The biodiversity found in genes, species, ecosystems, and ecosystem processes is vital to sustaining life on earth.
Biodiversity Is a Crucial Part of the Earth’s Natural Capital Biological diversity, or biodiversity, is the variety of the earth’s species, or varying life-forms, the genes they contain, the ecosystems in which they live, and the ecosystem processes of energy flow and nutrient cycling that sustain all life (Figure 3-1). Biodiversity involves several of the levels of organization of matter shown in Figure 2-8. They include •
Genetic diversity: differences in genes as represented by DNA among the individuals in a particular species;
Functional Diversity The biological and chemical processes such as energy flow and matter recycling needed for the survival of species, communities, and ecosystems.
Heat
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Heat
Ecological diversity: the number and variety of ecosystems in the world or in a particular area, each of which is a storehouse of genetic and species diversity;
•
Functional diversity: the biological and chemical processes, such as energy flow, matter cycling, and food webs, necessary for the survival of species, communities, and ecosystems.
The earth’s biodiversity is a vital part of the natural capital that helps to keep us alive and supports our economies. Biodiversity also plays critical roles in preserving the quality of the air and water, maintaining the
Ecological Diversity The variety of terrestrial and aquatic ecosystems found in an area or on the earth.
Producers (plants)
Consumers (plant eaters, meat eaters)
Genetic Diversity The variety of genetic material within a species or a population.
CHAPTER 3
•
Heat
Decomposers (bacteria, fungi)
Figure 3-1 Natural capital: This diagram illustrates the major components of the earth’s biodiversity—one of the earth’s most important renewable resources and a key component of the planet’s natural capital. Question: What are three examples of how people, in their daily living, intentionally or unintentionally degrade each of these types of biodiversity?
Species diversity: the number or vareity of species found in the world or in a particular area;
Solar energy
Chemical nutrients (carbon dioxide, oxygen, nitrogen, minerals)
Heat
•
Heat
Species Diversity The number and abundance of species present in different communities.
Biodiversity and Evolution
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I ND I VI D UALS M ATTE R Edward O. Wilson: A Champion of Biodiversity
A
s a boy growing up in the southeastern United States, Edward O. Wilson became interested in insects at the age of nine. He has stated, “Every kid has a bug period. I never grew out of mine.” Before entering college, Wilson had decided he would specialize in the study of ants. After he grew fascinated with that tiny organism, and throughout his long career, he steadily widened his focus to include the entire biosphere. He now spends much of his time studying, writing, and speaking about all of life—the earth’s biodiversity. During his long career of researching, writing, and teaching, Wilson has taken on many challenges. He and other researchers working together discovered how ants communicate using chemicals called pheromones. He also studied the complex social behavior of ants and has compiled much of his work into the epic volume, The Ants, published in 1990. His ant research has been applied to
the study and understanding of other social organisms. Wilson is sometimes credited with coining the term “biodiversity.” He was not actually the inventor of the term but was the first to use it in a scientific paper. In addition, he fleshed out the meaning of the term and essentially christened a new field of science. Another of his landmark works is The Diversity of Life, published in 1992, in which he put together the principles and practical issues of biodiversity more completely than anyone had to that point. Since then he has become deeply involved in writing and lecturing about the need for global conservation efforts. Wilson has won more than 100 awards, including the U.S. National Medal of Science, as well as similar national awards from many countries. He has written 25 books, two of which won the Pulitzer Prize for General Nonfiction. About the study of biodiversity, he writes:
fertility of topsoil, decomposing and recycling waste, and controlling populations of pests. We owe much of what we know about biodiversity to a fairly small number of researchers, one of whom is Edward O. Wilson (see Individuals Matter, above). There is considerable scientific evidence that we are destroying and degrading some of the earth’s biodiversity at an increasing rate as the ecological footprints (see Figure 1-6, p. 13) of more and more people spread across the planet’s surface. In 2005, the Millennium Ecosystem Assessment estimated that 12% of birds, 25% of mammals, and at least 32% of amphibians will be threat-
3-2
“Until we get serious about exploring biological diversity . . . science and humanity at large will be flying blind inside the biosphere. How can we fully understand the ecology of a pond or forest patch without knowledge of the thousands of species . . . the principal channels of materials and energy flow? How can we anticipate and control the spread of new crop diseases and human diseases if we do not know . . . the identity of the insects and other [species] that carry them? And, finally, . . . how can we save Earth’s life forms from extinction if we don’t even know what most of them are?” Learn more at the website of the Edward O. Wilson Biodiversity Foundation (www.eowilson.org).
ened with extinction in this century. The assessment also indicated that because of human activities, current extinction rates are 100 to 10,000 times higher than the natural rate of extinction that existed throughout most of earth’s history. We explore the causes and potential solutions for this problem in later chapters. Biodiversity is a renewable resource as long we live off the biological income it provides (essentially the renewable resources) instead of degrading and depleting the natural capital that supplies this income. Understanding, protecting, and sustaining biodiversity is a major theme of ecology and of this book.
Where Do Species Come From?
▲
CONC EPT 3-2 According to the scientific theory of evolution through natural selection, populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits.
Biological Evolution by Natural Selection Explains How Life Changes over Time How did we end up with today’s amazing array of millions of species on the earth? The scientific answer involves biological evolution (or simply evolution):
the process whereby earth’s life changes over time through changes in the genetic characteristics of populations (Concept 3-2). According to the theory of evolution, the process takes place because in a given population, individuals with a specific advantage over other individuals are more likely to survive, reproduce, and have offspring with similar CONCEPT 3-2
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51
survival skills. The advantage is due to a characteristic, or trait, possessed by these individuals but not by others in the population. These survival traits become more prevalent in future populations of a species through a process called natural selection, which occurs when some individuals in the population have genetically based traits that enhance their ability to survive and produce offspring with the same traits. A huge body of evidence has supported this idea. As a result, biological evolution through natural selection has become an important scientific theory. Much of this evidence comes from fossils: mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items found in rocks. Fossils provide physical evidence of ancient organisms and reveal what their internal structures looked like. Scientists also drill cores from glacial ice at the earth’s poles and on mountaintops to examine the kinds of life found at different layers. This scientific theory generally explains how life has changed over the past 3.5 billion years and why life is so diverse today. However, there are still many unanswered questions, and scientific debate over the details of evolution by natural selection continues. Such ongoing questioning and discussion is an important way in which science advances our knowledge of life on the earth.
Evolution by Natural Selection Works through Mutations and Adaptations The process of biological evolution by natural selection involves changes in a population’s genetic makeup through successive generations. Note that populations— not individuals—evolve by becoming genetically different. The first step in this process is the development of genetic variability, or variety in the genetic makeup of individuals in a population. This occurs through mutations: random changes in the structure or number of DNA molecules in a cell that offspring can inherit. Most mutations result from random changes that occur in coded genetic instructions and are passed along in reproduction. Some mutations also occur from exposure to external agents such as radioactivity, X rays, and natural and human-made chemicals (called mutagens). Mutations can occur in any cell, but only those taking place in genes of reproductive cells are passed on to offspring. Sometimes, such a mutation can result in a new genetic trait, called a heritable trait, which can pass from one generation to the next. In this way, populations develop differences among individuals, including genetic variability. The next step in biological evolution is natural selection, in which environmental conditions favor some individuals over others. The favored individuals pos-
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sess heritable traits that give them some advantage over other individuals in a given population. Such a trait is called an adaptation, or adaptive trait—any heritable trait that improves the ability of an individual organism to survive and to reproduce at a higher rate than other individuals in a population are able to do under prevailing environmental conditions (Concept 3-2). For natural selection to occur, the heritable trait must also lead to differential reproduction, which enables individuals with the trait to produce more surviving offspring than other members of the population produce. For example, in the face of snow and cold, a few gray wolves in a population that have thicker fur might live longer and thus produce more offspring than do those with thinner fur. As those longer-lived wolves mate, genes for thicker fur spread throughout the population, and individuals with those genes increase in number and pass this helpful trait on to more offspring. Thus, the scientific concept of natural selection explains how populations adapt to changes in environmental conditions. Genetic resistance is the ability of one or more organisms in a population to tolerate a chemical designed to kill it. For example, the organism might have a gene that allows it to break the chemical down into other harmless chemicals. Another important example of natural selection at work is the evolution of genetic resistance to widely used antibacterial drugs, or antibiotics. Doctors use these drugs to help control disease-causing bacteria, but they have become a force of natural selection. When such a drug is used, the few bacteria that are genetically resistant to it (because of some trait they possess) survive and rapidly produce more offspring than the bacteria that were killed by the drug could have produced. Thus, the antibiotic eventually loses its effectiveness as genetically resistant bacteria rapidly reproduce and those that are susceptible to the drug die off (Figure 3-2). One way to summarize the process of biological evolution by natural selection is: Genes mutate, individuals are selected, and populations evolve such that they are better adapted to survive and reproduce under existing environmental conditions (Concept 3-2).
Adaptation through Natural Selection Has Limits In the not-too-distant future, will adaptations to new environmental conditions through natural selection allow our skin to become more resistant to the harmful effects of ultraviolet radiation, our lungs to cope with air pollutants, and our livers to better detoxify pollutants? According to scientists in the field of evolutionary biology, the answer is no because of two limitations on adaptation through natural selection. First, a change in environmental conditions can lead to such an adaptation only for genetic traits already present in a popula-
Biodiversity and Evolution
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(a)
(b)
(c)
(d)
A group of bacteria, including genetically resistant ones, are exposed to an antibiotic
Most of the normal bacteria die
The genetically resistant bacteria start multiplying
Eventually the resistant strain replaces all or most of the strain affected by the antibiotic
Normal bacterium
Resistant bacterium
Figure 3-2 Evolution by natural selection. (a) A population of bacteria is exposed to an antibiotic, which (b) kills all individuals except those possessing a trait that makes them resistant to the drug. (c) The resistant bacteria multiply and eventually (d) replace all or most of the nonresistant bacteria.
tion’s gene pool or for traits resulting from mutations, which occur randomly. Second, even if a beneficial heritable trait is present in a population, the population’s ability to adapt may be limited by its reproductive capacity. Populations of genetically diverse species that reproduce quickly—such as weeds, mosquitoes, rats, cockroaches, and bacteria— often adapt to a change in environmental conditions in a short time (days to years). By contrast, species that cannot produce large numbers of offspring rapidly— such as elephants, tigers, sharks, and humans—take a much longer time (typically thousands or even millions of years) to adapt through natural selection.
Three Common Myths about Evolution through Natural Selection According to evolution experts, there are three common misconceptions about biological evolution through natural selection. One is that “survival of the fittest” means “survival of the strongest.” To biologists, fitness is a measure of reproductive success, not strength. Thus, the fittest individuals are those that leave the most descendants. Another misconception is that organisms develop certain traits because they need them. A giraffe has a very long neck not because it needs it to feed on vegetation high in trees. Rather, some ancestor had a gene for long necks that gave it an advantage over other members of its population in getting food, and that giraffe produced more offspring with long necks. A third misconception is that evolution by natural selection involves some grand plan of nature in which species become more perfectly adapted. From a scientific standpoint, no plan or goal for genetic perfection has been identified in the evolutionary process.
Geological Processes, Catastrophes, and Climate Change Affect Natural Selection The earth’s surface has changed dramatically over its long history. Scientists have discovered that huge flows of molten rock within the earth’s interior break its surface into a series of gigantic solid plates, called tectonic plates. For hundreds of millions of years, these plates have drifted slowly on the planet’s mantle. This fact that tectonic plates drift has had two important effects on the evolution and distribution of life on the earth. First, the locations of continents and oceanic basins have greatly influenced the earth’s climate—the average weather conditions of any area of the earth or of the entire planet over a period of at least 30 years—and thus helped to determine where plants and animals can live. Second, the movement of continents has allowed species to migrate, adapt to new environments, and form new species through natural selection. When continents join together, populations can disperse to new areas and adapt to new environmental conditions. When continents separate, some populations must evolve under isolated conditions or become extinct. Adjoining tectonic plates that are moving slowly past one another sometimes shift quickly. Such sudden movements of tectonic plates can cause earthquakes, which can create fissures in the earth’s crust that can separate and isolate populations of species. Over long periods of time, this can lead to the formation of new species as each isolated population changes genetically in response to new environmental conditions. Volcanic eruptions also occur along the boundaries of tectonic plates, and they can affect biological evolution by destroying habitats and reducing or wiping out populations of species. Throughout its long history, the earth’s climate has changed drastically. Sometimes it has cooled and covered
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SCIE N C E FO C US Earth Is Just Right for Life to Thrive
L
ife on the earth, as we know it, can thrive only within a certain temperature range related to properties of the liquid water that dominates the earth’s surface. Most life on the earth requires average temperatures between the freezing and boiling points of water. The earth’s orbit is the right distance from the sun to provide these conditions. If the earth were much closer to the sun, it would be too hot—like Venus—for water vapor to condense and form rain. If it were much farther away, the earth’s surface would be so cold—like Mars—that water would exist only as ice. The earth also spins fast enough to keep the sun from overheating any part of it. If it did not, water-dependent life could not exist. The size of the earth is also just right for life. It has enough gravitational mass to keep the atmosphere—made up of light gaseous
molecules required for life (such as N2, O2, CO2, and H2O)—from flying off into space. Although life on earth has been enormously adaptive, it has benefitted from a favorable temperature range. During the 3.5 billion years since life arose, the average surface temperature of the earth has remained within the narrow range of 10–20°C (50–68°F), even with a 30–40% increase in the sun’s energy output. One reason for this is the evolution of organisms that modify atmospheric levels of the temperatureregulating gas carbon dioxide as a part of the carbon cycle (see Figure 2-20, p. 42). For several hundred million years, oxygen has made up about 21% of the volume of earth’s atmosphere. If this oxygen content dropped to about 15%, it would be lethal for most forms of life. If it increased to about 25%, oxygen in the atmosphere would prob-
much of the earth with glacial ice. At other times it has warmed, melted that ice, and raised sea levels significantly. These long-term climate changes have a major effect on evolution by determining where different types of plants and animals can survive and thrive, and by changing the locations of different types of ecosystems such as deserts, grasslands, and forests. Some species became extinct because the climate changed too rapidly for them to adapt and survive. Another force affecting natural selection has been catastrophic events such as collisions between the earth
3-3
Critical Thinking Suppose the oxygen content of the atmosphere dropped below 15%. What types of organisms might eventually arise on the earth?
and large asteroids. There have probably been many of these collisions during the 3.5 billion years of life on earth. Such impacts have caused widespread destruction of ecosystems, wiped out large numbers of species, and created opportunities for the evolution of new species in newly evolved habitats. On a long-term basis, the three principles of sustainability (see back cover), especially the biodiversity principle (Figure 3-1), have enabled life on earth to adapt to drastic changes in environmental conditions (Science Focus, above).
How Do Speciation, Extinction, and Human Activities Affect Biodiversity?
▲
C O NC EPT 3-3 As environmental conditions change, the balance between formation of new species and extinction of existing species determines the earth’s biodiversity.
How Do New Species Evolve? Under certain circumstances, natural selection can lead to an entirely new species. In this process, called speciation, one species splits into two or more different species. For sexually reproducing organisms, a new species is formed when one population of a species has
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ably ignite into a giant fireball. The current oxygen content of the atmosphere is largely the result of producer and consumer organisms (especially phytoplankton and certain types of bacteria) interacting in the carbon cycle. Also, because of the development of photosynthesizing bacteria that have been adding oxygen to the atmosphere for more than 2 billion years, a sunscreen of ozone (O3) molecules in the stratosphere protects us and many other forms of life from an overdose of ultraviolet radiation. In short, this remarkable planet we live on is uniquely suited for life as we know it.
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evolved to the point where its members no longer can breed and produce fertile offspring with members of another population that did not change or that evolved in a different way. The most common way in which speciation occurs, especially among sexually reproducing species, takes place in two phases: first, geographic isolation and then
Biodiversity and Evolution
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Arctic Fox
Northern population
Early fox population
Adapted to cold through heavier fur, short ears, short legs, and short nose. White fur matches snow for camouflage.
Figure 3-3 Geographic isolation can lead to reproductive isolation, divergence of gene pools, and speciation.
Different environmental conditions lead to different selective pressures and evolution into two different species.
Spreads northward and southward and separates
Gray Fox Southern population
reproductive isolation. Geographic isolation occurs when different groups of the same population of a species become physically isolated from one another for a long period of time. For example, part of a population may migrate in search of food and then begin living as a separate population in another area with different environmental conditions. Populations can also be separated by a physical barrier (such as a mountain range, stream, or road), a volcanic eruption, tectonic plate movements, or winds or flowing water that carry a few individuals to a distant area. In reproductive isolation, mutation and change by natural selection operate independently in the gene pools of geographically isolated populations. If this process continues long enough, members of the geographically and reproductively isolated populations of sexually reproducing species may become so different in genetic makeup that they cannot produce live, fertile offspring if they are rejoined. Then, one species has become two, and speciation has occurred (Figure 3-3). For some rapidly reproducing organisms, this type of speciation may occur within hundreds of years. For most species, it takes from tens of thousands to millions of years—making it difficult to observe and document the appearance of a new species. Humans are playing an increasing role in the process of speciation. We have learned to shuffle genes from one species to another through artificial selection and, more recently, through genetic engineering (Science Focus, p. 56).
Extinction Is Forever Another process affecting the number and types of species on the earth is extinction, in which an entire species ceases to exist. Species that are found in only one area are called endemic species and are especially vulnerable to extinction. They exist on islands and in other
Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat.
unique areas, especially in tropical rain forests where most species have highly specialized roles. One example of such a species was the brilliantly colored golden toad, once found only in a small area of lush rain forests in Costa Rica’s mountainous region. Despite living in the country’s well-protected Monteverde Cloud Forest Reserve, by 1989 the golden toad had apparently become extinct. Much of the moisture that supported its rain forest habitat came in the form of moisture-laden clouds blowing in from the Caribbean Sea. But warmer air from global atmospheric warming caused these clouds to rise, depriving the forests of moisture. The habitat for the golden toad and many other species dried out. Because warmer air reduced the moisture in its forest habitat, the golden toad appears to be one of the first victims of climate change caused by atmospheric warming. All species eventually become extinct. Throughout most of earth’s history, species have disappeared at a low rate, called the background extinction rate. Based on the fossil record and analysis of ice cores drilled from glaciers, biologists estimate that the average annual background extinction rate has been one to five species per year for every 1 million species on the earth. In contrast, mass extinction is a significant rise in extinction rates above the background level. In such a catastrophic, widespread, and often global event, large groups of species (25–95% of all species) are wiped out worldwide in a few million years or less. Fossil and geological evidence indicate that the earth’s species have experienced at least three and probably five mass extinctions (20–60 million years apart) during the past 500 million years. A mass extinction provides an opportunity for the evolution of new species that can fill unoccupied ecological roles or newly created ones. As environmental conditions change, the balance between formation of new species (speciation) and extinction of existing species determines the earth’s biodiversity (Concept 3-3).
CONCEPT 3-3 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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SCIE N C E FO C US Changing the Genetic Traits of Populations
W
e have used artificial selection to change the genetic characteristics of populations with similar genes. In this process, we select one or more desirable genetic traits in the population of a plant or animal such as a type of wheat, fruit, or dog. Then we use selective breeding to generate populations of the species containing large numbers of individuals with the desired traits. Note that artificial selection involves crossbreeding between genetic varieties of the same species or between species that are genetically close to one another, and thus it is not a form of speciation. Most of the grains, fruits, and vegetables we eat are produced by artificial selection. Artificial selection has given us food crops with higher yields, cows that give more milk, trees that grow faster, and many different types of dogs and cats. But traditional crossbreeding is a slow process. Now scientists are using genetic engineering to speed up our ability to manipulate genes. Genetic engi-
neering is the alteration of an organism’s genetic material, through adding, deleting, or changing segments of its DNA to produce desirable traits or to eliminate undesirable ones. It enables scientists to transfer genes between different species that would not interbreed in nature. Scientists have used genetic engineering to develop modified crop plants, new drugs, pest-resistant plants, and animals that grow rapidly. They have also created genetically engineered bacteria to extract minerals such as copper from underground ores and to clean up spills of oil and other toxic pollutants. Genetic engineering offers some promise for improving our lives, but it raises some serious ethical and privacy issues. For example, it raises questions of ethics and morality over whether and how this technology will be applied to human beings, who will benefit, and who might suffer from it. The environmental impacts of this developing technology are also largely unknown.
The existence of millions of species today means that speciation, on average, has kept ahead of extinction. However, there is evidence that the rate of extinction is
3-4
Critical Thinking What might be some beneficial and harmful effects on the evolutionary process if genetic engineering is widely applied to plants and animals?
now higher than at any time during the past 65 million years and that much of this loss of biodiversity is due to human activities. We examine this further in Chapter 5.
What Are Biomes and How Have Human Activities Affected Them?
▲
C O NC EPT 3-4A
▲
C O NC EPT 3-4B In many areas, human activities are impairing ecological and economic services provided by the earth’s deserts, grasslands, forests, and mountains.
Differences in average annual precipitation and temperature lead to the formation of tropical, temperate, and cold deserts, grasslands, and forests, and largely determine their locations.
Climate Helps to Determine the Nature of Biomes Recall that a region’s climate is its average weather conditions over a period of at least 30 years. Differences in climate explain why one area of the earth’s land surface is a desert, another a grassland, and another a forest, and why there are different types of deserts, grasslands, and forests. Scientists have classified the terrestrial (land) areas of the world into several major biomes—large regions,
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Most new technologies have had unintended harmful consequences. For example, pesticides have helped to protect crops from insect pests and disease. But their overuse has accelerated the evolution of pesticide-resistant species and has wiped out many natural predator insects that had helped to keep pest populations under control. For these and other reasons, a backlash has developed against the increasing use of genetically modified food plants and animals. Some protesters argue against using this new technology, mostly for ethical reasons. Others advocate slowing down the technological rush and taking a closer look at the short- and long-term costs and benefits of using genetic engineering.
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each characterized by certain types of climate and dominant plant life. Figure 3-4 shows roughly how the biomes are distributed around the planet. Differences in climate are mostly due to differences in average annual precipitation and average temperature. Varying combinations of these two factors lead to the formation of tropical (hot), temperate (moderate), and polar (cold) deserts, grasslands, and forests (Concept 3-4A), as shown in Figure 3-5 (p. 58). Maps such as the one in Figure 3-4 show biomes with sharp boundaries, each covered with one general
Biodiversity and Evolution
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Tropic of Cancer
Equator
High mountains Polar ice Arctic tundra (cold grassland) Temperate grassland
Tropic of Capricorn
Tropical grassland (savanna) Chaparral Coniferous forest Temperate deciduous forest Temperate rain forest Tropical rain forest Tropical dry forest Desert Figure 3-4 Natural capital: The earth’s major biomes—each characterized by a certain combination of climate and dominant vegetation—result primarily from differences in climate. Each biome contains many ecosystems whose communities have adapted to differences in climate, soil, and other environmental factors. People have removed or altered much of the natural vegetation in some areas for farming, livestock grazing, lumber and fuelwood, mining, and construction of towns and cities. Question: If you take away human influences such as farming and urban development, what kind of biome do you live in?
type of vegetation. In reality, biomes are not uniform. They consist of a mosaic of patches, each with somewhat different biological communities but with similarities typical of the biome. These patches occur mostly because the resources that plants and animals need are not uniformly distributed and because human activities remove and alter the natural vegetation in many areas.
Biomes Are Grouped According to Their Characteristics We can divide each of the major biomes into subgroups determined by many factors including average precipitation and temperature, latitude (distance from the equator), altitude (elevation above sea level), and the locations and sizes of the nearest bodies of water. We will briefly consider some of these major types. A desert is an area where evaporation exceeds precipitation. Annual precipitation is low and often scat-
tered unevenly throughout the year. During the day, the baking sun warms the ground in the desert. But at night, most of the heat stored in the ground radiates quickly into the atmosphere. Desert soils have little vegetation and moisture to help store the heat, and the skies above deserts are usually clear. A combination of low rainfall and different average temperatures creates deserts that can be called tropical (closer to the equator), temperate (between the equator and the poles), or cold (closer to the poles). Desert ecosystems are fragile. Their soils take decades to hundreds of years to recover from disturbances such as off-road vehicle traffic because of slow plant growth, low species diversity, slow nutrient cycling (because of low bacterial activity in the soils), and lack of water. Grasslands occur mostly in the interiors of continents in areas too moist for deserts and too dry for forests. Grasslands have evolved to endure a combination of seasonal drought, grazing by large herbivores, and occasional fires—all of which keep large numbers of shrubs and trees from growing. CONCEPTS 3-4A AND 3-4B
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Cold
Arctic tundra
Cold desert Evergreen coniferous forest
Temperate desert Temperate deciduous forest
Temperate grassland
Chaparral
Hot Wet
Tropical desert Tropical rain forest
Dry Tropical grassland (savanna)
Figure 3-5 Natural capital: This diagram demonstrates that average precipitation and average temperature, acting together as limiting factors over a long time, help to determine the type of desert, grassland, or forest in a particular area, and thus the types of plants, animals, and decomposers found in that area (assuming it has not been disturbed by human activities).
As with deserts, the three main types of grassland— tropical, temperate, and cold (arctic tundra)—result from combinations of low average precipitation and various average temperatures. Many of the world’s natural temperate grasslands have disappeared because people have converted them to farms and ranches to take advantage of the fertile soils for growing crops and grazing cattle. Forest systems are lands dominated by trees. The three main classes of forest land—tropical, temperate, and cold—result from combinations of the precipitation level and various average temperatures. There are many examples of major forest types, and we briefly describe just a few here. Tropical rain forests are found near the equator where hot, moisture-laden air dumps its moisture almost daily. These lush forests have year-round, uniformly warm temperatures, high humidity, and heavy annual rainfall. This climate is ideal for a wide variety of plants and animals. Temperate deciduous forests grow in areas with moderate average temperatures that change significantly with the season. These areas have long, warm summers; cold,
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but not too severe, winters; and abundant precipitation, often spread fairly evenly throughout the year. Evergreen coniferous forests are also called boreal forests and taigas (“TIE-guhs”). These cold forests are found in the northernmost regions of North America, Asia, and Europe and above certain altitudes in the high Sierra and Rocky Mountain ranges of the United States. In this climate, winters are long and extremely cold and summers are short, with cool to warm temperatures. Coastal coniferous forests or temperate rain forests are found in scattered coastal temperate areas with ample rainfall or moisture from dense ocean fogs. Dense stands of large trees such as Sitka spruce, Douglas fir, and redwoods once dominated undisturbed areas of these biomes along the western coast of North America, from Canada to northern California in the United States. Finally, mountains are sharply elevated areas of land; mountain ranges cover about one-fourth of the earth’s land surface. Mountains play important ecological roles. They contain the majority of the world’s forests, which are habitats for much of the planet’s terrestrial biodiversity. They also help to regulate the earth’s
Biodiversity and Evolution
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Natural Capital Degradation Major Human Impacts on Terrestrial Ecosystems Deserts
Large desert cities Destruction of soil and underground habitat by off-road vehicles Soil salinization from irrigation
Grasslands
Conversion to cropland
Release of CO2 to atmosphere from burning grassland
Overgrazing by livestock
Depletion of groundwater Land disturbance and pollution from mineral extraction
Oil production and off-road vehicles in arctic tundra
Forests
Clearing for agriculture, livestock grazing, timber, and urban development
Mountains
Figure 3-6 This diagram summarizes the major human impacts on the world’s deserts, grasslands, forests, and mountains (Concept 3-4B). Question: For each of these biomes, which two of the impacts listed do you think are the most harmful?
Agriculture Timber and mineral extraction Hydroelectric dams and reservoirs
Conversion of diverse forests to tree plantations
Damage from off-road vehicles
Increasing tourism Air pollution blowing in from urban areas and power plants Soil damage from off-road vehicles
Pollution of forest streams
Water supplies threatened by glacial melting
Figure 3-6 This diagram summarizes the major human impacts on the world’s deserts, grasslands, forests, and mountains (Concept 3-4B). Question: For each of these biomes, which two of the impacts listed do you think are the most harmful?
climate. Mountaintops covered with ice and snow affect climate by reflecting solar radiation back into space, thus helping to cool the planet. In addition, by storing water as ice and snow and releasing it seasonally, mountains play a critical role in the hydrologic cycle.
Humans Have Disturbed Most of the Earth’s Land In many areas, human activities are impairing some of the ecological and economic services provided by the world’s deserts, grasslands, forests, and mountains (Concept 3-4B). According to the 2005 Millennium Ecosystem Assessment, about 62% of the world’s major terrestrial
ecosystems are being degraded or used unsustainably, as the human ecological footprint gets bigger and spreads across the globe (see Figure 1-6, p. 13). This environmental destruction and degradation is increasing in many parts of the world. Figure 3-6 summarizes some of the human impacts on the world’s deserts, grasslands, forests, and mountains. How long can we keep straining these terrestrial forms of natural capital without threatening our economies and the long-term survival of our own and many other species? No one knows. But there are increasing signs that we need to come to grips with this vital issue. This will require protecting the world’s remaining wild areas from development. In addition, we need to restore many of the land areas that we have degraded, as we discuss in Chapter 7.
CONCEPTS 3-4A AND 3-4B Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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3-5
What Are Aquatic Life Zones and How Have Human Activities Affected Them?
▲
C O NC EPT 3-5A
▲
C O NC EPT 3-5B
The key factors determining biodiversity in aquatic systems are temperature, dissolved oxygen content, availability of food, and availability of light and nutrients necessary for photosynthesis. Human activities threaten aquatic biodiversity and disrupt ecological and economic services provided by saltwater and freshwater systems.
Water Covers Most of the Earth and Sustains Biodiversity
Oceans Provide Important Ecological and Economic Resources
When viewed from a certain point in outer space, the earth appears to be almost completely covered with water (Figure 3-7). Saltwater covers about 71% of the earth’s surface, and freshwater occupies roughly another 2.2%. Yet, in proportion to the entire planet, it all amounts to a thin and precious film of water. The aquatic equivalents of biomes are called aquatic life zones—saltwater and freshwater portions of the biosphere that can support life. The distribution of many aquatic organisms is determined largely by the water’s salinity—the amounts of various salts such as sodium chloride (NaCl) dissolved in a given volume of water. As a result, aquatic life zones are classified into two major types: saltwater or marine life zones (oceans and their accompanying bays, estuaries, coastal wetlands, shorelines, coral reefs, and mangrove forests) and freshwater life zones (lakes, rivers, streams, and inland wetlands). Most forms of aquatic life are found in the surface, middle, and bottom layers of saltwater and freshwater systems. In most aquatic systems, the key factors determining the types and numbers of organisms found in these layers are water temperature, dissolved oxygen content, availability of food, and availability of light and nutrients required for photosynthesis, such as carbon (as dissolved CO2 gas), nitrogen (as NO3–), and phosphorus (mostly as PO43–) (Concept 3-5A).
The world’s oceans provide enormously valuable ecological and economic services (Figure 3-8). Yet we know more about the surface of the moon than about the oceans. According to scientists, studying poorly understood marine and freshwater aquatic systems could greatly increase the yield of ecological and economic benefits provided by these systems. Marine aquatic systems are huge reservoirs of biodiversity, found in three major life zones: the coastal zone, the open sea, and the ocean bottom (Figure 3-9). The coastal zone—waters that extend from the hightide mark on land to the edge of the continental shelf— makes up less than 10% of the world’s ocean area but
Natural Capital Marine Ecosystems Ec ol og i c al Ser vi c es
Ec onom ic Se rv ic e s
Climate moderation
Food
CO2 absorption
Animal and pet feed
Nutrient cycling
Pharmaceuticals
Waste treatment Reduced storm impact (mangroves, barrier islands, coastal wetlands)
Coastal habitats for humans
Habitats and nursery areas
Employment
Genetic resources and biodiversity Ocean hemisphere
Land–ocean hemisphere
Figure 3-7 The ocean planet: The salty oceans cover 71% of the earth’s surface and contain 97% of the earth’s water. Almost all of the earth’s water is in the interconnected oceans, which cover 90% of one hemisphere of the planet (left), and about half of the other hemisphere (right). Freshwater systems cover less than 2.2% of the earth’s surface.
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Harbors and transportation routes
Scientific information
Recreation
Oil and natural gas Minerals Building materials
Figure 3-8 Marine systems provide a number of important ecological and economic services. Questions: Which two ecological services and which two economic services do you think are the most important? Why?
Biodiversity and Evolution
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Depth in meters 0
Open Sea Sea level
50 Estuarine Zone
Euphotic Zone 100 Continental shelf
Photosynthesis
Coastal Zone
200 500
Bathyal Zone
1,000
Twilight
High tide Low tide
1,500
2,000
Abyssal Zone
3,000
4,000
Darkness
Water temperature drops rapidly between the euphotic zone and the abyssal zone in an area called the thermocline.
5,000
10,000
0
5
10
15
20
25
30
Water temperature (°C) Figure 3-9 Major life zones and vertical zones (not drawn to scale) in an ocean. Actual depths of zones may vary. Available light determines the euphotic, bathyal and abyssal zones. Temperature zones also vary with depth, shown here by the black curve. Question: What is the main effect of differences in light availability?
contains 90% of all marine species and is the site of most large commercial marine fisheries. Most coastal-zone aquatic systems have a high net primary productivity (NPP) per unit of area (see Figure 2-18, p. 40). This is the result of the zone’s ample supplies of sunlight and plant nutrients that flow from land and are distributed by wind and ocean currents. One such system, an estuary, is a partially enclosed body of water where a river meets the sea, and seawater mixes with freshwater as well as nutrients and pollutants from streams, rivers, and runoff from the land. A system associated with estuaries is a coastal wetland: a coastal land area covered with water all or part of the year. Such wetlands include salt marshes in temperate zones and mangrove forest swamps in tropical zones. Coral reefs form in the shallow coastal zones of warm tropical and subtropical oceans. They are among the world’s oldest, most diverse and productive ecosystems, hosting about one-fourth of all marine species.
These coastal aquatic systems provide important ecological and economic services. They filter toxic pollutants, excess plant nutrients, and sediments, while absorbing other pollutants. They provide food, habitats, and nursery sites for a variety of aquatic and terrestrial species. They also reduce storm damage and coastal erosion by absorbing waves and storing excess water produced by storms and tsunamis. The sharp increase in water depth at the edge of the continental shelf separates the coastal zone from the vast volume of the ocean called the open sea. Primarily on the basis of sunlight penetration, this deep blue sea is divided into three vertical zones—the euphotic, bathyal, and abyssal zones (Figure 3-9). Average NPP per unit of area is quite low in the open sea (see Figure 2-18, p. 40). However, because it covers so much of the earth’s surface, it makes the largest contribution to the earth’s overall NPP. Also, NPP is much higher in some open sea areas where winds, CONCEPTS 3-5A AND 3-5B
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61
ocean currents, and other factors cause water to rise from the depths to the surface. These upwellings bring nutrients from the ocean bottom to the surface for use by producers.
Human Activities Are Disrupting and Degrading Marine Systems Human activities are disrupting and degrading some ecological and economic services provided by marine aquatic systems, especially coastal wetlands, shorelines, mangrove forests, and coral reefs (Concept 3-5A).
Natural Capital Degradation Major Human Impacts on Marine Ecosystems and Coral Reefs Marine Ecosystems
Coral Reefs
Major threats to marine systems from human activities include coastal development, which destroys and pollutes coastal habitats, overfishing, runoff of nonpoint source pollution from the land, and habitat destruction from trawler fishing boats that drag weighted nets across the ocean bottom. Figure 3-10 shows some of the effects of such human impacts on marine systems (left) and coral reefs (right).
Why Are Freshwater Ecosystems Important? Freshwater life zones include standing (lentic) bodies of freshwater, such as lakes, ponds, and inland wetlands, and flowing (lotic) systems, such as streams and rivers. These systems provide a number of important ecological and economic services (Figure 3-11). Lakes are large natural bodies of standing freshwater formed when precipitation, runoff, and groundwater seepage fill depressions in the earth’s surface. Deep lakes normally consist of four distinct zones that are defined by their depth and distance from shore (Figure 3-12).
Natural Capital Freshwater Systems Ecological Services
Economic Services
Climate moderation
Food
Nutrient cycling Drinking water Waste treatment Half of coastal wetlands lost to agriculture and urban development
Ocean warming
Irrigation water Flood control
Rising ocean acidity Over one-fifth of mangrove forests lost to agriculture, development, and shrimp farms since 1980 Beaches eroding because of coastal development and rising sea levels Ocean bottom habitats degraded by dredging and trawler fishing At least 20% of coral reefs severely damaged and 25–33% more threatened
Soil erosion
Bleaching
Habitats for many species
Transportation corridors
Genetic resources and biodiversity
Recreation
Scientific information
Employment
Rising sea levels Increased UV exposure Damage from anchors
Figure 3-10 This diagram shows the major threats to marine ecosystems (left) and particularly coral reefs (right) resulting from human activities (Concept 3-5A). Questions: Which two of the threats to marine ecosystems do you think are the most serious? Why? Which two of the threats to coral reefs do you think are the most serious? Why?
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Hydroelectricity
Algae growth from fertilizer runoff
Damage from fishing and diving
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Groundwater recharge
Figure 3-11 Freshwater systems provide many important ecological and economic services. Questions: Which two ecological services and which two economic services do you think are the most important? Why?
Biodiversity and Evolution
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Figure 3-12 Distinct zones of life in a fairly deep temperate zone lake. Question: How do a deep lake’s zones compare to depth zones in the ocean? Painted turtle
Blue-winged teal
Green frog Muskrat
Pond snail
Littoral zone
Plankton
Limn
etic z
Prof
one
unda
Diving beetle
Ben
thic
l zon
e
Northern pike
zon
e
Yellow perch
Ecologists classify lakes according to their nutrient content and primary productivity. Lakes that have a small supply of plant nutrients are called oligotrophic (poorly nourished) lakes. Often, this type of lake is deep and has steep banks and very clear water. Because of their low levels of nutrients, these lakes have a low NPP. Over time, sediment and nutrients wash into most oligotrophic lakes, and plants grow and decompose to form bottom sediments. A lake with a large supply of nutrients is called a eutrophic (well-nourished) lake. Such lakes typically are shallow and have murky brown or green water. Because of their high levels of nutrients, these lakes have a high NPP. Human inputs of nutrients from the atmosphere and from nearby urban and agricultural areas can result in excessive nutrients in a lake, which is then described as hypereutrophic. Many lakes fall somewhere between the two extremes and are called mesotrophic lakes. Precipitation that does not sink into the ground or evaporate becomes surface water. It becomes runoff when it moves down a slope and across the land, and flows into a stream—a moving body of surface water. A watershed, or drainage basin, is the land area that delivers runoff, sediment, and dissolved substances to a stream. Small streams join to form rivers, and rivers flow downhill to the oceans (Figure 3-13, p. 64). In many areas, streams begin in mountainous or hilly areas that collect and release water falling to the earth’s surface as rain or as snow that melts during warm seasons. The downward flow of surface water and groundwater from mountain highlands to the sea typi-
Bloodworms
cally takes place in three aquatic life zones characterized by different environmental conditions: the source zone, the transition zone, and the floodplain zone (Figure 3-13). Rivers and streams can differ somewhat from this generalized model. Streams receive many of their nutrients from adjacent terrestrial ecosystems. Such nutrient inputs come from falling leaves, animal feces, insects, and other forms of biomass washed into streams during heavy rainstorms or by melting snow. Thus, the levels and types of nutrients in a stream depend on what is happening in the stream’s watershed. Inland wetlands are lands covered with freshwater all or part of the time (excluding lakes, reservoirs, and streams) and located away from coastal areas. They include marshes (dominated by grasses and reeds with few trees), swamps (dominated by trees and shrubs), and prairie potholes (depressions carved out by ancient glaciers). Other examples are floodplains, which receive excess water during heavy rains and floods, and the wet arctic tundra in summer. Some wetlands are covered with water year-round. Others, called seasonal wetlands, remain under water or are soggy for only a short time each year. Wetland plants are highly productive because of an abundance of nutrients. Many of these wetlands are important habitats for game fishes, muskrats, otters, beavers, migratory waterfowl, and many other bird species. Inland wetlands provide a number of other free ecological and economic services. They filter and degrade toxic wastes and pollutants, reduce flooding and erosion CONCEPTS 3-5A AND 3-5B
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63
Lake
Glacier
Headwaters
Rain and snow Rapids Waterfall Tributary Flood plain Oxbow lake Salt marsh Delta Deposited sediment Ocean
Source Zone
Transition Zone
Water Sediment Floodplain Zone
Figure 3-13 There are three zones in the downhill flow of water: the source zone, which contains mountain streams (headwaters); the transition zone, which contains wider, lower-elevation streams; and the floodplain zone, which contains rivers that empty into larger rivers or into the ocean.
by absorbing storm water and releasing it slowly, help replenish stream flows during dry periods, help recharge groundwater aquifers, and help maintain biodiversity by providing habitats for a variety of species.
Human Activities Are Disrupting and Degrading Freshwater Systems Human activities are disrupting and degrading many of the ecological and economic services provided by freshwater rivers, lakes, and wetlands (Concept 3-5B) in four major ways. First, dams and canals fragment about 40% of the world’s 237 largest rivers. They alter and destroy terrestrial and aquatic wildlife habitats along these rivers and in their coastal deltas and estuaries by reducing water flow and increasing damage from coastal storms. Second, flood control levees and dikes built along rivers disconnect the rivers from their floodplains, destroy aquatic habitats, and alter or reduce the functions of nearby wetlands. A third major human impact on freshwater systems comes from cities and farms, which add pollutants and excess plant nutrients to nearby streams, rivers, and lakes. And fourth, many inland wetlands have been drained or filled to grow crops or have been covered with concrete, asphalt, and buildings.
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CHAPTER 3
When we look further into human impacts on aquatic systems in Chapter 6, we also explore possible solutions to environmental problems that result from these impacts, as well as ways to help sustain aquatic biodiversity.
How the Principles of Sustainability Apply to Biodiversity and Evolution In this chapter, we studied the importance of biodiversity: the numbers and varieties of species found in different parts of the world and the wide variety of ecosystems. We also studied the process whereby all species came to be, according to the scientific theory of biological evolution through natural selection. Taken together, these two great assets, biodiversity and evolution, represent irreplaceable natural capital. Each depends upon the other and upon whether humans can respect and preserve this natural capital. Ecosystems and the variety of species they contain are functioning examples of the three principles of sustainability in action (see back cover). They depend on solar energy and provide functional biodiversity in the form of energy flow and the chemical cycling of nutrients. In addition, ecosystems sustain biodiversity in all its forms. In the next chapter, we delve further into this natural regulation of populations.
Biodiversity and Evolution
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Here are this chapter’s three big ideas. ■ Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits (evolution through natural selection). ■ Human activities are decreasing the earth’s vital biodiversity by causing the premature extinction of species and by disrupting habitats needed for the development of new species.
■ Differences in climate, based mostly on long-term differences in average temperature and precipitation, largely determine the types and locations of the earth’s terrestrial and aquatic ecosystems, and human activities are degrading and disrupting many of the ecological and economic services provided by these ecosystems.
All we have yet discovered is but a trifle in comparison with what lies hid in the great treasury of nature. ANTOINE VAN LEEUWENHOCK
REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 49. Define biodiversity (biological diversity). What are its four major components? What is the importance of biodiversity? Summarize the contributions of Edward O. Wilson to the study of biodivervsity. 2. What is biological evolution? Define natural selection. What is a fossil and why are fossils important in understanding biological evolution? What is a mutation and what role do mutations play in evolution by natural selection? Define adaptation (adaptive trait), and give two examples of adaptive traits. What is differential reproduction? Describe the evolution of genetic resistance in disease-causing bacteria. 3. What are two limits to evolution through natural selection? Summarize three myths about evolution through natural selection. 4. Define climate. Describe how geologic processes and climate change can affect natural selection. Describe conditions on the earth that favor the development of life as we know it. 5. What is speciation? Distinguish between geographic isolation and reproductive isolation and explain how they can lead to the formation of a new species. Distinguish between artificial selection and genetic engineering and give an example of each. What are some possible social, ethical, and environmental problems with the widespread use of genetic engineering? 6. What is extinction? What is an endemic species and why is it vulnerable to extinction? What is a background extinction rate? Define mass extinction.
7. What is a biome? Define the three major biome types— desert, grassland, and forest—and describe conditions under which each type forms. Define mountain and explain why mountains are important to the biosphere. For each of the major biome types, give two examples of how human activities are affecting their ecosystems. 8. What percentage of the earth’s surface is covered with water? What is an aquatic life zone? Distinguish between a saltwater (marine) life zone and a freshwater life zone. Distinguish between the coastal zone and the open sea. Define and distinguish between an estuary and a coastal wetland and explain why they have high net primary productivities. 9. What major ecological and economic services do freshwater systems provide? What is a lake? What four zones are found in most lakes? Distinguish between oligotrophic, eutrophic, hypereutrophic, and mesotrophic lakes. Define surface water, runoff, stream, and watershed (drainage basin). Describe the three zones that a stream passes through as it flows from mountains to the sea. Give three examples of inland wetlands and explain the ecological importance of such wetlands. 10. What are four examples of how human activities are disrupting and degrading marine ecosystems? What are four ways in which human activities are disrupting and degrading freshwater systems?
Note: Key terms are in bold type.
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CRITICAL THINKING 1. Describe what could happen to the biosphere if any of the four components of biodiversity were somehow eliminated. 2. What role does each of the following processes play in helping to implement the three principles of sustainability (see back cover): (a) natural selection, (b) speciation, and (c) extinction? 3. An important example of natural selection at work is the evolution of genetic resistance in disease-causing bacteria. What does this tell you about the increasing use of (a) antibiotics by people, (b) antibiotics in beef cattle and other livestock raised for meat production, and (c) antibacterial soaps and detergents by most consumers? 4. Geologic processes can separate and isolate populations of species and affect their evolution. What are two examples of human activities that could do the same thing?
5. How would you respond to someone who says that because extinction is a natural process, we should not worry about the loss of biodiversity when species become extinct as a result of our activities? 6. Which biomes are best suited for (a) raising crops and (b) grazing livestock? Use the three principles of sustainability to come up with three guidelines for growing food and grazing livestock in these biomes on a more sustainable basis. 7. Suppose you have a friend who owns property that includes a freshwater wetland, and the friend tells you he or she is planning to fill the wetland to make more room for a lawn and garden. What would you say to this friend?
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 3 for many study aids and ideas for further
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CHAPTER 3
reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
Biodiversity and Evolution
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Community Ecology, Population Ecology, and the Human Population
4
Key Questions and Concepts 4-1 What roles do species play in an ecosystem? CONCEPT 4-1A
4-5 What factors influence the size of the human population?
Each species plays a specific ecological
role called its niche. Any given species may play one or more of five key roles—native, nonnative, indicator, keystone, or foundation—in a particular ecosystem.
CONCEPT 4-1B
The average number of children born to women in a population (total fertility rate) is the key factor that determines population size.
CONCEPT 4-5B
How do species interact?
4-2
C O N C E P T 4 - 5 C The numbers of males and females in young, middle, and older age groups determine how fast a population grows or declines.
Five types of species interactions— competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem. CONCEPT 4-2
How can we slow human population growth?
4-6
4-3 How do communities and ecosystems respond to changing environmental conditions? C O N C E P T 4 - 3 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.
4-4
Population size increases because of births and immigration, and decreases through deaths and emigration.
CONCEPT 4-5A
C O N C E P T 4 - 6 We can slow human population growth by reducing poverty, elevating the status of women, and encouraging family planning.
What limits the growth of populations?
No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.
CONCEPT 4-4
In looking at nature, never forget that every single organic being around us may be said to be striving to increase its numbers. CHARLES DARWIN, 1859
Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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What Roles Do Species Play in an Ecosystem?
4-1 ▲ ▲
Each species plays a specific ecological role called its niche. Any given species may play one or more of five key roles—native, nonnative, indicator, keystone, or foundation—in a particular ecosystem. C O NC EPT 4-1A C O NC EPT 4-1B
Each Species Plays a Role in Its Ecosystem An important principle of ecology is that each species has a specific role to play in the ecosystems where it is found (Concept 4-1A). This distinct role that a species plays in its ecosystem is its ecological niche, or simply niche (often pronounced “nitch”). It is a species’ way of life in a community and includes everything that affects its survival and reproduction, such as how much water and sunlight it needs, how much space it requires, what it feeds on, what feeds on it, and the temperatures it can tolerate. A species’ niche should not be confused with its habitat, which is the place where it lives. Scientists use the niches of species to classify them broadly as generalists or specialists. Generalist species have broad niches. They can live in many different places, eat a variety of foods, and often tolerate a wide range of environmental conditions. Flies, cockroaches (see the Case Study that follows), mice, rats, white-tailed deer, raccoons, and humans are generalist species. In contrast, specialist species occupy narrow niches. They may be able to live in only one type of habitat, eat just one or only a few types of food, or tolerate a narrow range of climatic and other environmental conditions. For example, some shorebirds occupy specialized niches, feeding on crustaceans, insects, and
other organisms found on sandy beaches and their adjoining coastal wetlands (Figure 4-1). Because of their narrow niches, specialists are more prone to extinction when environmental conditions change. For example, China’s giant panda is highly endangered because of a combination of habitat loss, low birth rate, and its specialized diet consisting mostly of bamboo. Is it better to be a generalist or a specialist? It depends. When environmental conditions are fairly constant, as in a tropical rain forest, specialists have an advantage because they have fewer competitors. But under rapidly changing environmental conditions, the generalist usually is better off than the specialist. ■ C AS E S T UDY
Cockroaches: Nature’s Ultimate Survivors Cockroaches, the bugs many people love to hate, have been around for 350 million years, outliving the dinosaurs. One of evolution’s great success stories, they have thrived because they are generalists. The earth’s 3,500 cockroach species can eat almost anything, including algae, dead insects, fingernail clippings, salts deposited by sweat in tennis shoes, glue, paper, and soap. They can also live and breed almost
Brown pelican dives for fish, which it locates from the air Black skimmer seizes small fish at water surface
Herring gull is a tireless scavenger Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds
Flamingo feeds on minute organisms in mud
Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation
Louisiana heron wades into water to seize small fish
Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans
Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak
Knot (sandpiper) picks up worms and small crustaceans left by receding tide
Ruddy turnstone searches under shells and pebbles for small invertebrates
Piping plover feeds on insects and tiny crustaceans on sandy beaches
Figure 4-1 This diagram illustrates the specialized feeding niches of various bird species in a coastal wetland. This specialization reduces competition and allows sharing of limited resources.
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CHAPTER 4
Community Ecology, Population Ecology, and the Human Population
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anywhere except in polar regions. Some cockroach species can go for a month without food, survive for a month on a drop of water, and withstand massive doses of radiation. One species can survive being frozen for 48 hours. Cockroaches usually can evade their predators— and a human foot in hot pursuit—because most species have antennae that can detect minute movements of air. They also have vibration sensors in their knee joints, and they can respond faster than you can blink your eye. Some even have wings. They have compound eyes that allow them to see in almost all directions at once. Each eye has about 2,000 lenses, compared to just one in each of your eyes. They also have high reproductive rates. In only a year, a single Asian cockroach and its offspring can add about 10 million new cockroaches to the world. Their high reproductive rate also helps them to quickly develop genetic resistance to almost any poison we throw at them. Most cockroaches sample food before it enters their mouths and learn to shun foul-tasting poisons. They also clean up after themselves by eating their own dead and, if food is scarce enough, their living. About 25 species of cockroach live in homes and can carry viruses and bacteria that cause diseases. They can also cause people to have allergic reactions ranging from watery eyes to severe wheezing. On the other hand, cockroaches play a role in nature’s food webs. They make a tasty meal for birds and lizards.
Niches Can Be Occupied by Native and Nonnative Species Niches can be classified further in terms of specific roles that certain species play within ecosystems. Ecologists describe native, nonnative, indicator, keystone, and foundation species. Any given species may play one or more of these five roles in a particular ecosystem (Concept 4-1B). Native species are those species that normally live and thrive in a particular ecosystem. Other species that migrate into, or are deliberately or accidentally introduced into, an ecosystem are called nonnative species, also referred to as invasive, alien, and exotic species. Some people tend to think of nonnative species as threatening. In fact, most introduced and domesticated plant species such as food crops and flowers, and animals such as chickens, cattle, and fish from around the world are beneficial to us. However, some nonnative species can compete with and reduce a community’s native species, causing unintended and unexpected consequences. In 1957, for example, Brazil imported wild African honeybees to help increase honey production. Instead, the highly aggressive bees displaced domestic honeybees, reduced the honey supply, and killed thousands of domesticated animals and an estimated 1,000 people in the western hemisphere, many of whom were allergic to bee stings.
Indicator Species Serve as Biological Smoke Alarms Species that provide early warnings of damage to a community or an ecosystem are called indicator species. Birds are excellent biological indicators because they are found almost everywhere and are affected quickly by environmental changes such as the loss or fragmentation of their habitats and the introduction of chemical pesticides. The populations of many bird species are declining. Butterflies are also good indicator species because their association with various plant species makes them vulnerable to habitat loss and fragmentation. Some amphibians are also classified as indicator species (see the Case Study that follows). Using a living organism to monitor environmental quality is not new. Coal mining is a dangerous occupation, partly because of the underground presence of poisonous and explosive gases, many of which have no detectable odor. In the 1800s and early 1900s, coal miners took caged canaries into mines to act as earlywarning sentinels. These birds sing loudly and often. If they quit singing for a long period and appeared to be distressed, miners took this as an indicator of the presence of dangerous gases and got out of the mine. ■ C AS E S T UDY
Why Are Amphibians Vanishing? Amphibians (frogs, toads, and salamanders) live part of their lives in water and part on land. Populations of some amphibians, also believed to be indicator species, are declining throughout the world. Amphibians were the first vertebrates (animals with backbones) to walk on land. Historically, they have also been better at adapting to environmental changes through evolution than many other species have been. But many amphibian species are having difficulty adapting to some of the rapid environmental changes that have taken place in the air and water and on the land during the past few decades—changes resulting mostly from human activities. Frogs, for example, are especially vulnerable to environmental disruption at various points in their life cycle, shown in Figure 4-2 (p. 70). The eggs of frogs have no protective shells to block ultraviolet (UV) radiation or pollution. As tadpoles, frogs live in water and eat plants. As adults, they live mostly on land and eat insects that can expose them to pesticides. Frogs take in water and air through their thin, permeable skins, which can readily absorb pollutants from water, air, or soil. During their life cycle, frogs and many other amphibian species also seek sunlight, which warms them and helps them to grow and develop but also exposes them to harmful UV radiation. Since 1980, populations of hundreds of the world’s almost 6,000 amphibian species have been vanishing or CONCEPTS 4-1A AND 4-1B
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69
Figure 4-2 Life cycle of a frog: Populations of various frog species can decline because of the effects of harmful environmental factors at different points in their life cycle. Such factors include habitat loss, drought, pollution, increased ultraviolet radiation, parasitism, disease, overhunting by humans, and nonnative predators and competitors.
Adult frog (3 years)
Young frog
Tadpole develops into frog
Sperm
Sexual reproduction
Eggs
Tadpole
Fertilized egg development
Egg hatches Organ formation
declining in almost every part of the world, even in protected wildlife reserves and parks. According to a 2008 assessment by the International Union for Conservation of Nature and Natural Resources (IUCN), about 32% of all known amphibian species (and more than 80% of those in the Caribbean) are threatened with extinction. Populations of another 43% of the species are declining. No single cause has been identified to explain these amphibian declines. However, scientists have identified a number of factors that can affect frogs and other amphibians at various points in their life cycles:
70
•
Habitat loss and fragmentation, especially from the draining and filling of freshwater wetlands, deforestation, farming, and urban development.
•
Prolonged drought, which can dry up breeding pools so that few tadpoles survive.
•
Increases in UV radiation resulting from reductions in stratospheric ozone during the past few decades, due to chemicals released to the atmosphere by certain human activities.
•
Parasites such as flatworms, which feed on the amphibian eggs laid in water, apparently have caused an increase in the number of amphibians born with missing or extra limbs.
•
Viral and fungal diseases, especially the chytrid fungus that attacks the skin of frogs, apparently reducing their ability to take in water and leading to death from dehydration.
•
Pollution, especially exposure to pesticides in ponds and in the bodies of insects consumed by frogs, which can make them more vulnerable to bacterial, viral, and fungal diseases and to some parasites.
CHAPTER 4
•
Climate change; a 2005 study found an apparent correlation between climate change caused by atmospheric warming and the extinction of about twothirds of the 110 known species of harlequin frogs in tropical forests in Central and South America.
•
Overhunting, especially in Asia and France, where frog legs are a delicacy.
•
Natural immigration of, or deliberate introduction of, nonnative predators and competitors (such as certain fish species).
A combination of such factors, which vary from place to place, probably is responsible for the decline or disappearance of most amphibian species. Why should we care if some amphibian species become extinct? Scientists give three reasons. First, amphibians are sensitive biological indicators of changes in environmental conditions such as habitat loss and degradation, air and water pollution, exposure to UV radiation, and climate change. Their possible extinction suggests that environmental health is deteriorating in parts of the world. Second, adult amphibians play important ecological roles in biological communities. For example, amphibians eat more insects (including mosquitoes) than do birds. In some habitats, the extinction of certain amphibian species could lead to the extinction of other species, such as reptiles, birds, aquatic insects, fish, mammals, and other amphibians that feed on them or their larvae. Third, amphibians represent a genetic storehouse of pharmaceutical products waiting to be discovered. For example, compounds in secretions from amphibian skin have been isolated and used as painkillers and antibiotics, and as treatment for burns and heart disease.
Community Ecology, Population Ecology, and the Human Population
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Many scientists believe that the rapidly increasing chances for global extinction of a variety of amphibian species is a warning about the harmful effects of an array of environmental threats to biodiversity, mostly resulting from human activities.
do this and more. They sometimes play this foundation role, but also play an active role in maintaining the ecosystem and keeping it functioning.
■ C AS E S T UDY
Why Should We Protect Sharks? Keystone and Foundation Species Play Critical Roles in Their Ecosystems A keystone is the wedge-shaped stone placed at the top of a stone archway. Remove this stone and the arch collapses. Ecologists hypothesize that, in some communities and ecosystems, certain species play a similar role. Keystone species are species whose roles have a large effect on the types and abundance of other species in an ecosystem. Keystone species often exist in relatively limited numbers in their ecosystems, but the effects that they have there can be much larger than their numbers would suggest. In addition, because of their often smaller numbers, some keystone species are more vulnerable to extinction than other species are. Keystone species can play several critical roles in helping to sustain ecosystems. One such role is the pollination of flowering plant species by butterflies, bees, hummingbirds, bats, and other species. In addition, top predator keystone species feed on and help to regulate the populations of other species. Examples are the alligator, wolf, leopard, lion, and some shark species. (See the Case Study that follows.) The loss of a keystone species can lead to population crashes and extinctions of other species in a community that depends on them for certain ecological services. This is why it so important for scientists to identify and protect keystone species. Another important type of species in some ecosystems is a foundation species, which plays a major role in shaping communities by creating and enhancing their habitats in ways that benefit other species. For example, elephants push over, break, or uproot trees, creating forest openings in the grasslands and woodlands of Africa. This promotes the growth of grasses and other forage plants that benefit smaller grazing species such as antelope. It also accelerates nutrient cycling rates. Beavers are another good example of a foundation species. Acting as “ecological engineers,” they build dams in streams to create ponds and wetlands that they and other species use. Some bat and bird foundation species help to regenerate deforested areas and spread fruit plants by depositing plant seeds in their droppings. Keystone and foundation species play similar roles. In general, the major difference between the two types of species is that foundation species help to create habitats and ecosystems. They often do this by almost literally providing the foundation for the ecosystem (as beavers do, for example). However, keystone species can
More than 400 known species of sharks inhabit the world’s oceans. They vary widely in size and behavior, from the goldfish-sized dwarf dog shark to the whale shark, which can grow to a length of 18 meters (60 feet) and weigh as much as two full-grown African elephants. Some shark species, feeding at or near the tops of food webs, remove injured and sick animals from the ocean, and thus play an important ecological role. Without the services provided by these keystone species, the oceans would be teeming with dead and dying fish. In addition to their important ecological roles, sharks could help save human lives; if we can learn why they almost never get cancer, we could use this information to fight cancer in our own species. Scientists are also studying the shark’s highly effective immune system, which allows wounds to heal without becoming infected. Many people, influenced by movies, popular novels, and widespread media coverage of shark attacks, think of sharks as people-eating monsters. In reality, the three largest species—the whale shark, basking shark, and megamouth shark—are gentle giants. These planteating sharks swim through the water with their mouths open, filtering out and swallowing huge quantities of tiny floating organisms called phytoplankton. Media coverage of shark attacks greatly exaggerates the danger from sharks. Every year, members of a few species such as the great white, bull, tiger, oceanic white tip, and hammerhead sharks injure 60–75 people worldwide. Between 1998 and 2007, there were an average of six deaths per year from such attacks. Because some of these sharks feed on sea lions and other marine mammals, they sometimes mistake swimmers and surfers for their usual prey. However, for every shark that injures or kills a person every year, people kill about 1.2 million sharks, or 100 million a year worldwide, according to Australia’s Shark Research Institute. Many sharks are caught for their valuable fins and then thrown back alive into the water, fins removed, to bleed to death or drown because they can no longer swim. The fins are widely used in Asia as a soup ingredient and as a pharmaceutical cureall. Sharks are also killed for their livers, meat, hides, and jaws, and because we fear them. Some sharks die when they are trapped in nets or lines deployed to catch swordfish, tuna, shrimp, and other species. According to a 2009 study by the International Union for Conservation of Nature (IUCN), 32% of the world’s open-ocean shark species are threatened with extinction. One of the most endangered species is the scalloped hammerhead shark. In addition, sharks are CONCEPTS 4-1A AND 4-1B
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especially vulnerable to population declines because they grow slowly, mature late, and have only a few offspring per generation. Today, they are among the earth’s most vulnerable and least protected animals. Because of the increased demand for shark fins and meat, nine of the world’s shark species are considered critically endangered or endangered, and 81 species are threatened with extinction. In response to a public outcry over depletion of some species, the United States and several other countries have banned the hunting of sharks for their fins. But such bans apply only in territorial waters and are difficult to enforce. Scientists call for a ban on shark finning in international waters and
4-2
HOW WOULD YOU VOTE?
✓ ■
Do we have an ethical obligation to keep from driving various shark species to extinction and to treat them humanely? Cast your vote online at www.cengage.com/login.
How Do Species Interact?
▲
C O NC EPT 4-2 Five types of species interactions—competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem.
Species Interact in Five Major Ways Ecologists identify five basic types of interactions between species as they share limited resources such as food, shelter, and space: interspecific competition, predation, parasitism, mutualism, and commensalism. Members of these species may be harmed, helped, or unaffected by such interactions. In addition, these interactions have significant effects on the resource use and population sizes of the species in an ecosystem (Concept 4-2). The most common interaction between species is interspecific competition, which occurs when members of two or more species interact to gain access to the same limited resources such as food, light, or space. While fighting for resources does occur, most competition involves the ability of one species to become more efficient than another species in acquiring food or other resources. Humans compete with many other species for space, food, and other resources. As our ecological footprints grow and spread (see Figure 1-6, p. 13) and we convert more of the earth’s land, aquatic resources, and net primary productivity to our uses, we are taking over the habitats of many other species and depriving them of resources they need in order to survive. Over a time scale long enough for natural selection to occur, populations of some species develop adaptations that allow them to reduce or avoid competition with other species for the same resources. One way this happens is through resource partitioning, which occurs when species competing for similar scarce resources evolve specialized traits that allow them to use shared resources at different times, in different ways, or in different places (Figure 4-3).
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for the establishment of a network of fully protected marine reserves to protect sharks and other species from overfishing in coastal waters. Sharks have been around for more than 400 million years. Sustaining this portion of the earth’s biodiversity begins with the knowledge that sharks may not need us, but that we and other species need them.
CHAPTER 4
Another example of resource partitioning involves birds called honeycreepers that live in the U.S. state of Hawaii. Long ago these birds started from a single ancestral species. But through evolution by natural selection there are now numerous honeycreeper species. Each has a different type of specialized beak for feeding on certain food sources such as specific types of insects, nectar from particular types of flowers, and certain types of seeds and fruit.
Most Consumer Species Feed on Live Organisms of Other Species In predation, a member of one species (the predator) feeds directly on all or part of a living organism of another plant or animal species (the prey) as part of a food web. Together, the two different species, such as a brown bear (the predator, or hunter) and a salmon (the prey, or hunted), form a predator–prey relationship. Such relationships are also shown in Figures 2-15 and 2-16 (p. 38). Sometimes predator–prey relationships can surprise us. During the summer months, the grizzly bears of the Greater Yellowstone ecosystem in the western United States eat huge amounts of army cutworm moths, which huddle in masses high on remote mountain slopes. One grizzly bear can dig out and lap up as many as 40,000 of the moths in a day. Consisting of 50–70% fat, the moths offer a nutrient that the bear can store in its fatty tissues and draw on during its winter hibernation. At the individual level, members of the predator species benefit and members of the prey species are
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Blackburnian Warbler
Black-throated Green Warbler
Cape May Warbler
Bay-breasted Warbler
Yellow-rumped Warbler
Figure 4-3 Resource partitioning is a strategy used by five species of insect-eating warblers in the spruce forests of the U.S. state of Maine. Each species minimizes competition with the others for food by spending at least half its feeding time in a distinct portion (lighter shaded areas) of the spruce trees, and by consuming somewhat different insect species. (After R. H. MacArthur, “Population Ecology of Some Warblers in Northeastern Coniferous Forests,” Ecology 36 (1958): 533–536.)
harmed. At the population level, predation plays a role in evolution by natural selection (see Chapter 3, p. 51). Animal predators, for example, tend to kill the sick, weak, and aged members of a population because they are the easiest to catch. This leaves behind individuals with better defenses against predation. Such individuals tend to survive longer and leave more offspring with adaptations that can help them avoid predation. Some people tend to view certain animal predators with contempt. When a hawk tries to capture and feed on a rabbit, some root for the rabbit. Yet the hawk, like all predators, is merely trying to get enough food for itself and its young. In doing so, it plays an important ecological role in controlling rabbit populations.
quitoes, mistletoe plants, and sea lampreys, which use their sucker-like mouths to attach themselves to fish and feed on their blood. Some parasites move from one host to another, as fleas and ticks do; others, such as tapeworms, spend their adult lives with a single host. Some parasites have little contact with their hosts. For example, North American cowbirds take over the nests of other birds by laying their eggs in them and then letting the host birds raise their young. From the host’s point of view, parasites are harmful. But from the population perspective, parasites can promote biodiversity by contributing to species richness, and in some cases, they help to keep the populations of their hosts in check.
Some Species Feed Off Other Species by Living On or In Them
In Some Interactions, Both Species Benefit
Parasitism occurs when one species (the parasite) feeds on another organism (the host), usually by living on or in the host. In this relationship, the parasite benefits and the host is often harmed but not immediately killed. We can view parasitism as a special form of predation. But unlike the typical predator, a parasite usually is much smaller than its host (prey) and rarely kills the host. Also, because most parasites remain closely associated with their hosts as they draw nourishment from them, they may gradually weaken the hosts over time. Some parasites, such as tapeworms and some disease-causing microorganisms (pathogens), live inside their hosts. Other parasites attach themselves to the outsides of their hosts. Examples of the latter include mos-
In mutualism, two species behave in ways that benefit both by providing each with food, shelter, or some other resource. For example, honeybees, caterpillars, butterflies, and other insects feed on a male flower’s nectar, picking up pollen in the process, and then pollinate female flowers when they feed on them. Figure 4-4 (p. 74) shows two examples of mutualistic relationships that combine nutrition and protection. One involves birds that ride on the backs of large animals like African buffalo, elephants, and rhinoceroses (Figure 4-4a). The birds remove and eat parasites and pests (such as ticks and flies) from the animal’s body and often make noises warning the larger animals when predators approach.
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(a) Oxpeckers and black rhinoceros
A second example involves clownfish species, which live within sea anemones, whose tentacles sting and paralyze most fish that touch them (Figure 4-4b). The clownfish are not harmed by the tentacles, gain protection from predators, and feed on the detritus left from the anemones’ meals. The sea anemones benefit because the clownfish protect them from some of their predators. In another example of mutualism, vast armies of bacteria in the digestive systems of animals help to break down (digest) their hosts’ food. In turn, the bacteria receive a sheltered habitat and food from their host. Hundreds of millions of bacteria in your gut secrete enzymes that help digest the food you eat. It is tempting to think of mutualism as an example of cooperation between species. In reality, each species benefits by unintentionally exploiting the other as a result of traits they obtained through natural selection.
4-3
(b) Clownfish and sea anemone
In Some Interactions, One Species Benefits and the Other Is Not Harmed Commensalism is an interaction that benefits one species but has little, if any, effect on the other. For example, in tropical forests certain kinds of silverfish insects move along with columns of army ants to share the food obtained by the ants in their raids. The army ants receive no apparent harm or benefit from the silverfish. Another example involves plants called epiphytes (such as certain types of orchids and bromeliads), which attach themselves to the trunks or branches of large trees in tropical and subtropical forests. These air plants benefit by having a solid base on which to grow. They also live in an elevated spot that gives them better access to sunlight, water from the humid air and rain, and nutrients falling from the tree’s upper leaves and limbs. Their presence apparently does not harm the tree.
How Do Communities and Ecosystems Respond to Changing Environmental Conditions?
▲
C O NC EPT 4-3 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.
Communities and Ecosystems Change over Time: Ecological Succession The types and numbers of species in biological communities and ecosystems change in response to changing environmental conditions such as a fires, volcanic eruptions, climate change, and the clearing of forests to plant crops. The normally gradual change in species composition in a given area is called ecological succession (Concept 4-3).
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Fred Bavendam/Peter Arnold, Inc.
Joe McDonald/Tom Stack & Associates
Figure 4-4 Examples of mutualism. (a) Oxpeckers (or tickbirds) feed on parasitic ticks that infest large, thickskinned animals such as the endangered black rhinoceros. (b) A clownfish gains protection and food by living among deadly stinging sea anemones and helps protect the anemones from some of their predators.
CHAPTER 4
Ecologists recognize two main types of ecological succession, depending on the conditions present at the beginning of the process. Primary ecological succession involves the gradual establishment of biotic communities in lifeless areas where there is no soil in a terrestrial ecosystem or no bottom sediment in an aquatic ecosystem. Examples include bare rock exposed by a retreating glacier (Figure 4-5), newly cooled lava, an abandoned highway or parking lot, and a newly created shallow pond or reservoir. Primary succession
Community Ecology, Population Ecology, and the Human Population
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Exposed rocks
Lichens and mosses
Small herbs and shrubs
Heath mat
Jack pine, black spruce, and aspen
Balsam fir, paper birch, and white spruce forest community
Time
Figure 4-5 Primary ecological succession: Over almost a thousand years, plant communities developed, starting on bare rock exposed by a retreating glacier on Isle Royal, Michigan (USA) in northern Lake Superior. The details of this process vary from one site to another. Question: What are two ways in which lichens, mosses, and plants might get started growing on bare rock?
usually takes hundreds to thousands of years because of the need to build up fertile soil or aquatic sediments to provide the nutrients needed to establish a plant community. Primary succession can also take place in a newly created small pond, starting with an influx of sediments and nutrients in runoff from the surrounding land. This sediment can support seeds or spores of plants carried to the pond by winds, birds, or other animals. Over time this process can transform the pond first into a marsh and eventually into dry land. The other, more common type of ecological succession is called secondary ecological succession, in which a series of communities or ecosystems with different species develop in places containing soil or bottom sediment. It begins in an area where an ecosystem has been disturbed, removed, or destroyed, but some soil or bottom sediment remains. Candidates for secondary succession include abandoned farmland (Figure 4-6, p. 76), burned or cut forests, heavily polluted streams, and land that has been flooded. Because some soil or sediment is present, new vegetation can begin to germinate, usually within a few weeks. It begins with seeds
already in the soil and seeds imported by wind or in the droppings of birds and other animals. Descriptions of ecological succession usually focus on changes in vegetation. But these changes, in turn, affect food and shelter for animals, and the numbers and types of animals and decomposers in the area also change. Thus, primary succession (Figure 4-5) and secondary succession (Figure 4-6) tend to increase biodiversity and interactions among species.
Succession Does Not Follow a Predictable Path According to the traditional view, succession proceeds in an orderly sequence along an expected path until a certain stable type of climax community occupies an area. Such a community is dominated by a few long-lived plant species and is in balance with its environment. This equilibrium model of succession is what ecologists once meant when they talked about the balance of nature. Over the last several decades, many ecologists have changed their views about balance and equilibrium in CONCEPT 4-3
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Figure 4-6 Natural ecological restoration of disturbed land: This diagram shows the undisturbed secondary ecological succession of plant communities on an abandoned farm field in the U.S. state of North Carolina. It took 150–200 years after the farmland was abandoned for the area to become covered with a mature oak and hickory forest. A new disturbance such as deforestation or fire would create conditions favoring pioneer species such as annual weeds. In the absence of new disturbances, secondary succession would recur over time, but not necessarily in the same sequence shown here. Questions: Do you think the annual weeds (left) would continue to thrive in the mature forest (right)? Why or why not?
Mature oak and hickory forest
Annual weeds
Perennial weeds and grasses
Shrubs and small pine seedlings
Young pine forest with developing understory of oak and hickory trees
Time
nature. Under the balance-of-nature view, a large terrestrial community or ecosystem undergoing succession eventually became covered with an expected type of climax vegetation such as a mature forest. There is a general tendency for succession to lead to more complex, diverse, and presumably stable ecosystems. But a close look at almost any terrestrial community or ecosystem reveals that it consists of an ever-changing mosaic of patches of vegetation at different stages of succession.
4-4
What Limits the Growth of Populations?
▲
No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.
C O NC EPT 4-4
Populations Can Grow, Shrink, or Remain Stable Four variables—births, deaths, immigration, and emigration—govern changes in population size. A population increases by birth and immigration (arrival of individuals from outside the population) and decreases by
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The current view is that we cannot predict a given course of succession or view it as inevitable progress toward an ideally adapted climax plant community or ecosystem. Rather, succession reflects the ongoing struggle by different species for enough light, water, nutrients, food, and space. Most ecologists now recognize that mature, late-successional ecosystems are not in a state of permanent equilibrium. Rather, they are in a state of continual disturbance and change.
CHAPTER 4
death and emigration (departure of individuals from the population): Population change = (Births + Immigration) – (Deaths + Emigration)
Species vary in their biotic potential or capacity for population growth under ideal conditions. Generally, populations of large species such as elephants and
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Environmental resistance
Population size
Carrying capacity Population stabilizes
Exponential growth
Time (t) Figure 4-7 No population can grow forever (Concept 4-4). Exponential growth (left-most portion of the curve) occurs when resources are not limited and a population can grow to the point where such growth is converted to logistic growth, in which the growth rate decreases as the population becomes larger and faces environmental resistance (central part of curve). Over time, the population size stabilizes at or near the carrying capacity (K) of its environment, which results in a sigmoid (S-shaped) population growth curve. Depending on resource availability, the size of a population often fluctuates around its carrying capacity, although a population may temporarily exceed its carrying capacity and then suffer a sharp decline or crash in its numbers. Question: What is an example of environmental resistance that humans have not been able to overcome?
2.0
Number of sheep (millions)
blue whales have a low biotic potential while those of small species such as bacteria and insects have a high biotic potential. The intrinsic rate of increase (r) is the rate at which the population of a species would grow if it had unlimited resources. Individuals in populations with a high intrinsic rate of growth typically reproduce early in life, have short generation times (the time between successive generations), can reproduce many times, and have many offspring each time they reproduce. Some species have an astounding biotic potential. With no controls on its population growth, a bacterium that reproduced itself every 20 minutes would form a layer 0.3 meter (1 foot) deep over the entire earth’s surface in only 36 hours! Fortunately, this is not a realistic scenario. No population can grow indefinitely because of limitations on resources and competition with other species for those resources (Concept 4-4). In the real world, a rapidly growing population reaches some size limit imposed by one or more limiting factors, such as light, water, space, or nutrients, or by exposure to too many competitors, predators, or infectious diseases. There are always limits to population growth in nature. This is one of nature’s three principles of sustainability (see back cover and Concept 1-1, p. 6). Environmental resistance is the combination of all factors that act to limit the growth of a population. Together, biotic potential and environmental resistance determine carrying capacity: the maximum population of a given species that a particular habitat can sustain indefinitely. The growth rate of a population decreases as its size nears the carrying capacity of its environment because resources such as food, water, and space begin to dwindle. A population with few, if any, limitations on its resource supplies can grow exponentially at a fixed rate such as 1% or 2% per year. This type of growth, called exponential growth, starts slowly but then accelerates as the population increases, because the base size of the population is increasing. Plotting the number of individuals against time yields a J-shaped growth curve (Figure 4-7, left-most portion of curve). Logistic growth involves rapid exponential population growth followed by a steady decrease in population growth until the population size levels off (Figure 4-7, center of curve). This slowdown occurs as the population encounters environmental resistance from declining resources and other environmental factors, and approaches the carrying capacity of its environment (right end of curve). After leveling off, a population with this type of growth typically fluctuates slightly above and below the carrying capacity. Plotting the number of individuals against time yields a sigmoid, or S-shaped, logistic growth curve (the right side of the curve in Figure 4-7). Figure 4-8 depicts such a curve for sheep on the island of Tasmania, south of Australia, in the early 19th and early 20th centuries.
Population overshoots carrying capacity
Carrying capacity
1.5 Population recovers and stabilizes 1.0
Exponential growth
Population runs out of resources and crashes
.5
1800
1825
1850
1875
1900
1925
Year Figure 4-8 Logistic growth of a sheep population on the island of Tasmania between 1800 and 1925. After sheep were introduced in 1800, their population grew exponentially, thanks to an ample food supply. By 1855, they had overshot the land’s carrying capacity. Their numbers then stabilized and fluctuated around a carrying capacity of about 1.6 million sheep.
When a Population Exceeds Its Carrying Capacity It Can Crash Some species do not make a smooth transition from exponential growth to logistic growth. Such populations use up their resource supplies and temporarily overshoot,
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Others say that sooner or later we will reach the limits that nature always imposes on populations. Population overshoots carrying capacity
Number of reindeer
2,000
HOW WOULD YOU VOTE?
1,500
Population crashes
1,000
500
Species Have Different Reproductive Patterns
Carrying capacity
0 1910
1920
1930
1940
1950
Year Figure 4-9 This graph tracks the exponential growth, overshoot, and population crash of reindeer introduced to the small Bering Sea island of St. Paul. When 26 reindeer (24 of them female) were introduced in 1910, lichens, mosses, and other food sources were plentiful. By 1935, the herd size had soared to 2,000, overshooting the island’s carrying capacity. This led to a population crash, when the herd size plummeted to only 8 reindeer by 1950. Question: Why do you think this population grew fast and crashed, unlike the sheep in Figure 4-8?
or exceed, the carrying capacity of their environment. This occurs because of a reproductive time lag: the period needed for the birth rate to fall and the death rate to rise in response to resource overconsumption. In such cases, the population suffers a dieback, or population crash, unless the excess individuals can switch to new resources or move to an area with more resources. Such a crash occurred when reindeer were introduced onto a small island in the Bering Sea (Figure 4-9). Sometimes when a population exceeds the carrying capacity of an area, it causes damage that reduces the area’s carrying capacity. For example, overgrazing by cattle on dry western lands in the United States has reduced grass cover in some areas. This has allowed sagebrush—which cattle cannot eat—to move in, thrive, and replace grasses, reducing the land’s carrying capacity for cattle. Humans are not exempt from population overshoot and dieback. Ireland experienced a population crash after a fungus destroyed the potato crop in 1845. About 1 million people died, and 3 million people migrated to other countries. So far, technological, social, and other cultural changes have extended the earth’s carrying capacity for the human species. We have increased food production and used large amounts of energy and matter resources to occupy normally uninhabitable areas. Some say we can keep expanding our ecological footprint indefinitely, primarily because of our technological ingenuity.
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✓ ■
Can we continue to expand the earth’s carrying capacity for humans? Cast your vote online at www.cengage.com/ login.
CHAPTER 4
Species use different reproductive patterns to help ensure their long-term survival. Some species have many, usually small, offspring and give them little or no parental care or protection. These species overcome typically massive losses of offspring by producing so many offspring that a few will likely survive to reproduce many more offspring themselves, and begin this reproductive pattern again. Examples include algae, bacteria, and most insects. Such species tend to be opportunists. They reproduce and disperse rapidly when conditions are favorable or when a disturbance opens up a new habitat or niche for invasion. Environmental changes caused by disturbances such as fires, clear-cutting, and volcanic eruptions allow opportunist species to gain a foothold. However, once established, their populations may crash because of unfavorable changes in environmental conditions or invasions by more competitive species. This helps to explain why most opportunist species go through irregular and unstable boom-and-bust cycles in their population sizes. At the other extreme are competitor species, which tend to reproduce later in life and have a small number of offspring with fairly long life spans. Typically, the offspring of mammals with this reproductive strategy develop inside their mothers (where they are safe), and are born fairly large. After birth, they mature slowly and are cared for and protected by one or both parents. In some cases, they live in herds or groups until they reach reproductive age and begin the cycle again. Such species tend to do well in competitive conditions when their population size is near the carrying capacity of their environment. Their populations typically follow a logistic growth curve (Figure 4-8). Most large mammals (such as elephants, whales, and humans), birds of prey, and large and long-lived plants (such as the saguaro cactus and most tropical rain forest trees) are competitor species. Ocean fish (such as orange roughy and swordfish), which are now being depleted by overfishing, also fit into this category. Many competitor species—especially those with long times between generations and low reproductive rates like elephants, rhinoceroses, and sharks—are prone to extinction. Most organisms have reproductive patterns between the two extremes.
Community Ecology, Population Ecology, and the Human Population
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4-5
What Factors Influence the Size of the Human Population?
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CONC EPT 4-5A
▲
CONC EPT 4-5B The average number of children born to women in a population (total fertility rate) is the key factor that determines population size.
▲
CONC EPT 4-5C
Population size increases because of births and immigration and decreases through deaths and emigration.
The numbers of males and females in young, middle, and older age groups determine how fast a population grows or declines.
Human Population Growth Continues, but It Is Unevenly Distributed For most of history, the human population grew slowly, but for the past 200 years, it has grown rapidly (Figure 1-10, p. 16). Three major factors account for this population increase. First, humans developed the ability to expand into diverse new habitats and different climate zones. Second, the emergence of early and modern agriculture allowed more people to be fed. Third, the development of sanitation systems, antibiotics, and vaccines helped to control infectious disease agents, and death rates, which then dropped sharply below birth rates. About 10,000 years ago when agriculture began, there were about 5 million humans on the planet; now there are 6.9 billion of us. It took from the time we arrived about 200,000 years ago until about 1927 to add the first 2 billion people to the planet; less than 50 years to add the next 2 billion (by 1974); and just 25 years to add the next 2 billion (by 1999)—an illustration of the awesome power of exponential growth. The rate of population growth has slowed, but the world’s population is still growing exponentially at a rate of 1.22% a year. This meant that 83 million people were added to the world’s population during 2010—an average of more than 227,000 more people each day, or 2.6 more people every time your heart beats. Geographically, this growth is unevenly distributed. About 1% of the 83 million new arrivals on the planet in 2010 were added to the world’s more-developed countries, which are growing at 0.17% a year. The other 99% were added to the world’s middle- and low-income, lessdeveloped countries, which are growing 9 times faster at 1.4% a year. And at least 95% of the 2.7 billion people likely to be added to the world’s population between 2010 and 2050 will end up in the least-developed countries, most of which are the least equipped to deal with the pressures of such rapid growth. How many of us are likely to be here in 2050? Answer: 7.8–10.8 billion people, depending mostly on projections about the average number of babies women are likely to have. The medium projection is 9.6 billion people.
During this century, the human population may level off as it moves from a J-shaped curve of exponential growth to an S-shaped curve of logistic growth because of various factors that can limit human population growth (Figure 4-7). The question is can the world provide an adequate standard of living for the medium projection of 9.6 billion people in 2050 without causing widespread environmental damage?
The Human Population Can Grow, Decline, or Remain Fairly Stable Human populations grow or decline in particular countries, cities, or other areas through the interplay of three factors: births (fertility), deaths (mortality), and migration. We can calculate the population change of any area by subtracting the number of people leaving a population (through death and emigration) from the number entering it (through birth and immigration) during a specified period of time (usually one year) (Concept 4-5A). Population = (Births + Immigration) – (Deaths + Emigration) change
When births plus immigration exceed deaths plus emigration, a population increases; when the reverse is true, a population declines. Instead of using the total numbers of births and deaths per year, demographers, or population experts, use the birth rate, or crude birth rate (the number of live births per 1,000 people in a population in a given year), and the death rate, or crude death rate (the number of deaths per 1,000 people in a population in a given year). What five countries had the largest numbers of people in 2010? Number 1 is China with 1.3 billion people, or one of every five people in the world (Figure 4-10, p. 80). Number 2 is India, with 1.2 billion people, or one of every six in the world. Together China and India have 37% of the world’s population. The United States, with 310 million people in 2010—has the world’s third largest population, but only 4.5% of the world’s people.
CONCEPTS 4-5A, 4-5B, AND 4-5C Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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woman in more-developed countries and from 6.2 to 2.7 in less-developed countries. Although the latter decline is impressive, the TFR in less-developed countries remains far above the replacement level of 2.1, not low enough to stabilize the world’s population in the near future.
2010 China
1.3 billion
India United States Indonesia Brazil
1.2 billion 310 million 235 million 193 million
2050 India
1.7 billion
China United States
1.4 billion 439 million
Pakistan
335 million
Indonesia
309 million
Figure 4-10 This chart shows the populations of the world’s five most populous countries in 2010 and 2050 (projected). In 2010, more than one of every three persons on the earth lived in China (with 19% of the world’s population) or India (with 17%). (Data from United Nations Population Division, The 2008 Revision)
Figure 4-10 also shows projections for the top five most populous countries in 2050, with India projected to be in first place.
Women Are Having Fewer Babies but Not Few Enough to Stabilize the World’s Population Another measurement used in population studies is the fertility rate, the number of children born to a woman during her lifetime. Two types of fertility rates affect a country’s population size and growth rate. The first type, called the replacement-level fertility rate, is the average number of children that couples in a population must bear to replace themselves. It is slightly higher than two children per couple (2.1 in moredeveloped countries and as high as 2.5 in some lessdeveloped countries), mostly because some children die before reaching their reproductive years. Does reaching replacement-level fertility bring an immediate halt to population growth? No, because so many future parents are alive. If each of today’s couples had an average of 2.1 children, they would not be contributing to population growth. But if all of today’s girl children grow up to have 2.1 children as well, the world’s population would continue to grow for 50 years or more (assuming death rates do not rise) because there are so many young girls under age 15 who will be moving into their reproductive years. The second type of fertility rate, the total fertility rate (TFR), is the average number of children born to women in a population during their reproductive years. This factor plays a key role in determining population size (Concept 4-5B). Between 1955 and 2010, the average global TFR dropped from 2.8 to 1.7 children per
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CHAPTER 4
■ C AS E S T UDY
The U.S. Population Is Growing Rapidly The population of the United States grew from 76 million in 1900 to 310 million in 2010, despite oscillations in the country’s TFR and birth rates (Figure 4-11). It took the country 139 years to add its first 100 million people, 52 years to add another 100 million by 1967, and only 39 years to add the third 100 million by 2006. During the period of high birth rates between 1946 and 1964, known as the baby boom, 79 million people were added to the U.S. population. At the peak of the baby boom in 1957, the average TFR was 3.7 children per woman. In 2010, as in most years since 1972, it has been at or below 2.1 children per woman. The drop in the TFR has slowed the rate of population growth in the United States. But the country’s population is still growing faster than those of all other more-developed countries and is not close to leveling off. According to the U.S. Census Bureau, about 2.7 million people (one person every 12 seconds) were added to the U.S. population in 2010. Two-thirds of those additions were through births, and a third of them were immigrants. In addition to the fourfold increase in population growth since 1900, some amazing changes in lifestyles took place in the United States during the 20th century (Figure 4-12) that led to dramatic increases in per capita resource use and a much larger U.S. ecological footprint (see Figure 1-6, top, p. 13).
Several Factors Affect Birth Rates and Fertility Rates Many factors affect a country’s average birth rate and TFR. One is the importance of children as a part of the labor force, especially in less-developed countries. Another economic factor is the cost of raising and educating children. Birth and fertility rates tend to be lower in more-developed countries, where raising children is much more costly because they do not enter the labor force until they are in their late teens or twenties. (In the United States, for example, it costs more than $220,000 to raise a middle-class child from birth to age 18.) The availability of, or lack of, private and public pension systems can influence the decision of some couples on
Community Ecology, Population Ecology, and the Human Population
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4.0 Births per woman
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Year Figure 4-11 The top graph shows the total fertility rates for the United States between 1917 and 2010, and the bottom graph shows the country’s birth rate between 1917 and 2010. Question: The U.S. fertility rate has declined and remained at or below replacement levels since 1972. So why is the population of the United States still increasing? (Data from Population Reference Bureau and U.S. Census Bureau)
47 years
Life expectancy Married women working outside the home
77 years 8% 81%
15%
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how many children to have, especially the poor in lessdeveloped countries. Pensions reduce a couple’s need to have many children to help support them in old age. There are more infant deaths in poorer countries, so having several children might insure survival of at least a few—somewhat like having an insurance policy. Urbanization plays a role. People living in urban areas usually have better access to family planning services and tend to have fewer children than do those living in rural areas (especially in less-developed countries) where children are often needed to help raise crops and carry daily water and fuelwood supplies. Another important factor is the educational and employment opportunities available for women. Total fertility rates tend to be low when women have access to education and paid employment outside the home. In lessdeveloped countries, a woman with no education typically has two more children than does a woman with
1900 Hourly manufacturing job wage
Homicides per 100,000 people
2000
$3 $15
1.2 5.8
Figure 4-12 These are some major changes that took place in the United States between 1900 and 2000. Question: Which two of these changes do you think were the most important? (Data from U.S. Census Bureau and Department of Commerce)
CONCEPTS 4-5A, 4-5B, AND 4-5C Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
81
a high school education. In nearly all societies, bettereducated women tend to marry later and have fewer children. Average age at marriage (or, more precisely, the average age at which a woman has her first child) also plays a role. Women normally have fewer children when their average age at marriage is 25 or older. Birth rates and TFRs are also affected by the availability of legal abortions. Each year, about 190 million women become pregnant. The United Nations and the Alan Guttmacher Institute estimate that at least 40 million of these women get abortions—about 20 million of them legal and the other 20 million illegal (and often unsafe). Also, the availability of reliable birth control methods allows women to control the number and spacing of the children they have. Religious beliefs, traditions, and cultural norms also play a role. In some countries, these factors favor large families as many people there strongly oppose abortion and some forms of birth control.
low infant mortality rates, women tend to have fewer children because fewer children die at an early age. Infant mortality rates, both in more-developed and less-developed countries, have declined dramatically since 1965. But despite this sharp drop each year, more than 4 million infants (most of them in less-developed countries) die of preventable causes during their first year of life—an average of nearly 11,000 infant deaths per day. This is equivalent to 55 jet airliners, each loaded with 200 infants younger than age 1, crashing every day with no survivors! The U.S. infant mortality rate declined from 165 in 1900 to 6.4 in 2010. This sharp decline was a major factor in the marked increase in U.S. average life expectancy during this period. Still, some 53 countries, including Japan, South Korea, Israel, and most of Europe, had lower infant mortality rates than the United States had in 2010. Three factors helped to keep the U.S. infant mortality rate high: inadequate health care for poor women during pregnancy and for their babies after birth, drug addiction among pregnant women, and a high birth rate among teenagers.
Several Factors Affect Death Rates The rapid growth of the world’s population over the past 100 years is not primarily the result of a rise in the birth rate. Instead, it has been caused largely by a decline in death rates, especially in less-developed countries. More people in these countries started living longer, and fewer infants died because of increased food supplies and distribution and better nutrition. Medical advances such as immunizations and antibiotics, improved sanitation, and safer water supplies (which curtailed the spread of many infectious diseases) also helped. Two useful indicators of the overall health of people in a country or region are life expectancy (the average number of years a newborn infant can be expected to live) and the infant mortality rate (the number of babies out of every 1,000 born who die before their first birthday). Between 1955 and 2010, the global life GOOD expectancy increased from 48 years to 69 years NEWS (77 years in more-developed countries and 67 years in less-developed countries) and is projected to reach 74 by 2050. Between 1900 and 2009, life expectancy in the United States increased from 47 to 78 years and, by 2050, is projected to reach 83 years. In the world’s poorest countries, however, life expectancy is 57 years or less and may fall further in some countries because of more deaths from AIDS and internal strife. Infant mortality is viewed as one of the best measures of a society’s quality of life because it reflects a country’s general level of nutrition and health care. A high infant mortality rate usually indicates insufficient food (undernutrition), poor nutrition (malnutrition), and a high incidence of infectious disease (usually from drinking contaminated water and having weakened disease resistance due to undernutrition and malnutrition). Infant mortality also affects the TFR. In areas with
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Migration Affects an Area’s Population Size The third factor in population change is migration: the movement of people into (immigration) and out of (emigration) specific geographic areas. Most people migrating from one area or country to another seek jobs and economic improvement. But religious persecution, ethnic conflicts, political oppression, wars, and certain types of environmental degradation such as soil erosion and water and food shortages drive some to migrate. According to a UN study and to another study by environmental scientist Norman Myers, in 2008, there were at least 40 million environmental refugees—people who had to leave their homes because of water or food shortages, drought, flooding, or other environmental crises—and an estimated million more are added to this number every year. ■ C AS E S T UDY
The United States: A Nation of Immigrants Since 1820, the United States has admitted almost twice as many immigrants and refugees as all other countries combined. The number of legal immigrants (including refugees) has varied during different periods because of changes in immigration laws and rates of economic growth (Figure 4-13). Currently, legal and illegal immigration account for about 36% of the country’s annual population growth. Between 1820 and 1960, most legal immigrants to the United States came from Europe. Since 1960, most
Community Ecology, Population Ecology, and the Human Population
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Number of legal immigrants (thousands)
2,000 1,800 1,600
1907
1,400
1914 New laws restrict immigration
1,200 1,000 800
Great Depression
600 400
Figure 4-13 This graph shows legal immigration to the United States, 1820–2006 (the last year for which data are available). The large increase in immigration since 1989 resulted mostly from the Immigration Reform and Control Act of 1986, which granted legal status to certain illegal immigrants who could show they had been living in the country prior to January 1, 1982. (Data from U.S. Immigration and Naturalization Service and the Pew Hispanic Center)
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200 0 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 2010 Year
have come from Latin America (53%) and Asia (25%), followed by Europe (14%). In 2009, Hispanics (2 out of 3 from Mexico) made up 15% of the U.S. population, and by 2050, are projected to make up 30% of the population. There is controversy over whether to reduce legal immigration to the United States. Some legislators recommend accepting new entrants only if they can support themselves, arguing that providing legal immigrants with public services makes the United States a magnet for the world’s poor. Proponents of reducing legal immigration argue that it would allow the United States to stabilize its population sooner and help to reduce the country’s enormous environmental impact from its large ecological footprint (see Figure 1-6, p. 13). Polls show that almost 60% of the American public strongly supports reducing legal immigration. There is also intense political controversy over what to do about illegal immigration. In 2009, there were an estimated 11 million illegal immigrants in the United States. Those opposed to reducing current levels of legal immigration argue that it would diminish the historical role of the United States as a place of opportunity for the world’s poor and oppressed. They also argue that it would take away from the cultural diversity that has been a hallmark of American culture since the country’s beginnings. In addition, according to several studies, including a 2006 study by the Pew Hispanic Center, most immigrants and their descendants pay taxes. They also start new businesses, create jobs, add cultural vitality, and help the United States to succeed in the global economy. In addition, many immigrants take menial and lowpaying jobs that most other Americans shun. In fact, if the baby-boom generation is to receive social security benefits at the levels that retirees have come to expect, the U.S. workforce will have to grow, and immigrants will help to solve that problem.
Population Age Structure Can Affect Growth or Decline As mentioned earlier, even if the global replacementlevel fertility rate of 2.1 children per woman were magically achieved tomorrow, the world’s population would keep growing for at least another 50 years (assuming no large increase in the death rate). This continued growth results mostly from a population’s age structure: the numbers or percentages of males and females in young, middle, and older age groups in that population (Concept 4-5C). Population experts construct a population age-structure diagram by plotting a given population’s percentages of males and females in each of three age categories: prereproductive (ages 0–14), consisting of individuals normally too young to have children; reproductive (ages 15–44), consisting of those normally able to have children; and postreproductive (ages 45 and older), with individuals normally too old to have children. Figure 4-14 (p. 84) presents generalized age-structure diagrams for countries with rapid, slow, zero, and negative population growth rates. A country with a large percentage of its people younger than age 15 (represented by a wide base in Figure 4-14, far left) will experience rapid population growth unless death rates rise sharply. The number of births will rise for several decades even if women have an average of only one or two children, due to the large number of girls entering their prime reproductive years. In 2010, about 27% of the world’s population—30% in less-developed countries and 16% in more-developed countries—was under age 15. Over the next 14 years, these 1.8 billion young people—amounting to about 1 of every 4 persons on the planet—are poised to move into their prime reproductive years. However, the fastest growing age group is seniors— people who are 65 and older, according to a 2009 report from the U.S. Census Bureau. The global population of seniors is projected to triple by 2050, when one of every six people will be a senior. This graying of the world’s population is due largely to declining birth rates and medical advances that have extended our lifespans.
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83
Male
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Expanding Rapidly Guatemala Nigeria Saudi Arabia
Female
Male
Female
Expanding Slowly United States Australia China
Prereproductive ages 0–14
Male
Stable Japan Italy Greece
Female
Reproductive ages 15–44
Declining Germany Bulgaria Russia
Postreproductive ages 45–85+
Figure 4-14 This chart represents the generalized population age-structure diagrams for countries with rapid (1.5–3%), slow (0.3–1.4%), zero (0–0.2%), and negative (declining) population growth rates. A population with a large proportion of its people in the prereproductive age group (far left) has a significant potential for rapid population growth (Concept 4-5C). Question: Which of these diagrams best represents the country where you live? (Data from Population Reference Bureau)
■ CAS E STUDY
In addition to dominating the population’s demand for goods and services, the baby-boom generation plays an increasingly important role in deciding who gets elected to public office and what laws are passed. Baby boomers created the youth market in their teens and twenties and are now creating the late-middle-age and senior markets. In the economic downturn of the past decade, many of these people have lost their jobs and much of their savings. How this large portion of the American population deals with the downturn as they advance into later life will provide major challenges for them and for younger generations of U.S. workers.
The American Baby Boom Changes in the distribution of a country’s age groups have long-lasting economic and social impacts. For example, consider the American baby boom, which added 79 million people to the U.S. population. For decades, members of the baby-boom generation have strongly influenced the U.S. economy because they make up about 36% of all adult Americans. Over time, this group looks like a bulge moving up through the country’s age structure, as shown in Figure 4-15.
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Figure 4-15 These charts track the baby-boom generation in the United States, showing the U.S. population by age and sex for 1955, 1985, 2015 (projected), and 2035 (projected). (Data from U.S. Census Bureau)
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Community Ecology, Population Ecology, and the Human Population
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24
In 1960, one in 11 Americans were older than 65. After 2011, when the first baby boomers begin turning 65, the number of Americans older than age 65 will grow sharply through 2030 when they will be one of every five people in the country. This process has been called the graying of America. According to the U.S. Census Bureau, after 2020, much higher immigration levels will be needed to supply enough workers as baby boomers retire. According to a recent study by the UN Population Division, if the United States wants to maintain its current ratio of workers to retirees, it will need to absorb an average of 10.8 million immigrants each year—more than 10 times the current immigration level—through 2050. At that point, the U.S. population could total 1.1 billion people, and 73% of them would be immigrants or their descendants. Housing this influx of almost 11 million immigrants per year would require building the equivalent of another New York City every 10 months.
Populations Made Up Mostly of Older People Can Decline Rapidly As the age structure of the world’s population changes and the percentage of people age 60 or older increases, more countries will begin experiencing population declines. If population decline is gradual, its harmful effects usually can be managed. However, rapid population decline can lead to severe economic and social problems. A country that experiences a fairly rapid “baby bust” or a “birth dearth,” when its TFR falls below 1.5 children per couple for a prolonged period, sees a sharp rise in the proportion of older people. This puts severe strains on government budgets because these individuals consume an increasingly larger share of medical care, pension funds, and other costly public services, which are funded by a decreasing number of working taxpayers. Such countries can also face labor shortages unless they rely more heavily on automation or massive immigration of foreign workers. Figure 4-16 lists some of the problems associated with rapid population decline. Countries faced with a rapidly declining population include Japan, Russia, Germany, Bulgaria, Hungary, Ukraine, Serbia, Greece, Portugal, and Italy.
Populations Can Decline Due to a Rising Death Rate: The AIDS Tragedy Many countries are feeling the effects of the global epidemic of acquired immune deficiency syndrome (AIDS) caused by the human immunodeficiency virus (HIV). A large number of deaths from AIDS can disrupt a country’s social and economic structure by remov-
Some Problems with Rapid Population Decline Can threaten economic growth
Labor shortages
Less government revenues with fewer workers
Less entrepreneurship and new business formation
Less likelihood for new technology development
Increasing public deficits to fund higher pension and health-care costs
Pensions may be cut and retirement age increased
Figure 4-16 Rapid population decline can cause several problems. Question: Which three of these problems do you think are the most serious?
ing significant numbers of young adults from its population. According to the World Health Organization, between 1981 and 2009, AIDS killed more than 27 million people and it takes about 2 million more lives each year (including 22,000 in the United States, 39,000 in China, 140,000 in Zimbabwe, and 350,000 in South Africa). Unlike hunger and malnutrition, which kill mostly infants and children, AIDS kills many young adults and leaves many children orphaned. This change in the young-adult age structure of a country has a number of harmful effects. One is a sharp drop in average life expectancy, especially in several African countries where 15–26% of the adult population is infected with HIV. Another effect of the AIDS pandemic is the loss of productive young adult workers and trained personnel such as scientists, farmers, engineers, and teachers, as well as government, business, and health-care workers. The essential services they could provide are therefore lacking, and thus there are fewer workers available to support the very young and the elderly. Population and health experts call for the international community to create and fund a massive program to help countries ravaged by AIDS. The program would reduce the spread of HIV by providing financial assistance for improving education and health care. It would also provide funding for volunteer teachers, as well as health-care and social workers to try to compensate for the missing young-adult generation.
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4-6
How Can We Slow Human Population Growth?
▲
C O NC EPT 4-6 We can slow human population growth by reducing poverty, elevating the status of women, and encouraging family planning.
Is the Earth Overpopulated? An Important Controversy The projected increase of the human population from 6.9 to 9.6 billion or more between 2010 and 2050 reminds us of the important question: Can the world provide an adequate standard of living for a projected 2.7 billion more people by 2050 without causing widespread environmental damage? There is disagreement about the answer to this question. According to some analysts, the planet already has too many people collectively degrading the earth’s natural capital. They point out that we are not providing the basic necessities for about one of every five people— a total of about 1.6 billion. They ask, how will we be able to do so for the projected 2.7 billion more people by 2050? Others point out that technological advances have allowed humans to overcome the environmental resistance that all populations face and to increase the earth’s carrying capacity for humans. They see no reason for this to end and believe that the planet can support billions more people. As a result, they see no need for controlling the world’s population growth. Some opponents of population regulation see it as a violation of their religious or moral beliefs. Others see it as an intrusion into their privacy and personal freedom to have as many children as they want. Proponents of slowing and eventually stopping population growth warn of two serious consequences if we do not sharply lower birth rates. First, death rates may increase because of declining health and environmental conditions in some areas, as is already happening in parts of Africa. Second, resource use and environmental degradation may intensify as more consumers increase their already large ecological footprint in developed countries and in rapidly developing countries, such as China and India. This debate over interactions among population growth, economic growth, politics, and moral beliefs is one of the most important and controversial issues in environmental science.
As Countries Develop, Their Populations Tend to Grow More Slowly Demographers, examining the birth and death rates of western European countries that became industrialized during the 19th century, developed a hypothesis of
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population change known as the demographic transition: As countries become industrialized and economically developed, first their death rates decline and then their birth rates decline. According to the hypothesis based on such data, this transition takes place in four distinct stages (Figure 4-17). First is the preindustrial stage, when there is little population growth because harsh living conditions lead to both a high birth rate (to compensate for high infant mortality) and a high death rate. Next is the transitional stage, when industrialization begins, food production rises, and health care improves. Death rates drop and birth rates remain high, so the population grows rapidly (typically 2.5–3% a year). During the third phase, called the industrial stage, the birth rate drops and eventually approaches the death rate as industrialization, medical advances, and modernization become widespread. Population growth continues, but at a slower and perhaps fluctuating rate, depending on economic conditions. Most of the world’s more-developed countries and a few less-developed countries are now in this third stage. The fertility rates in many less-developed countries have dropped sharply, but they are still above replacementlevel fertility. Thus, the populations in these countries are still increasing and will continue doing so for several decades. The last phase is the postindustrial stage, when the birth rate declines further, equaling the death rate and reaching zero population growth. If the birth rate falls below the death rate, population size decreases slowly. Forty countries containing about 14% of the world’s population have entered this stage and several of the world’s more-developed countries are expected to enter this phase by 2050. In most less-developed countries today, death rates have fallen much more than birth rates. These countries are still in the transitional stage, halfway up the economic ladder, with high population growth rates. Some analysts believe that most of the world’s lessdeveloped countries will make a demographic transition over the next few decades, mostly because modern technology can raise per capita incomes by bringing economic development and family planning to such countries. But other analysts fear that rapid population growth, extreme poverty, and increasing environmental degradation in some low-income, less-developed countries—especially in Africa—could leave these countries stuck in stage 2 of the demographic transition. Other factors that could hinder the demographic transition in some less-developed countries are short-
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Birth rate and death rate (number per 1,000 per year)
80
Stage 1 Preindustrial
Stage 2 Transitional
Stage 3 Industrial
Population grows very slowly because of a high birth rate (to compensate for high infant mortality) and a high death rate
Population grows rapidly because birth rates are high and death rates drop because of improved food production and health
Population growth slows as both birth and death rates drop because of improved food production, health, and education
Stage 4 Postindustrial Population growth levels off and then declines as birth rates equal and then fall below death rates
70
Figure 4-17 The demographic transition, which a country can experience as it becomes industrialized and more economically developed, can take place in four stages. Question: At what stage is the country where you live?
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ages of scientists, engineers, and skilled workers, insufficient financial capital, large foreign debt to moredeveloped countries, and a drop in economic assistance from more-developed countries since 1985. This could leave large numbers of people trapped in poverty.
Empowering Women Helps to Slow Population Growth A number of studies show that women tend to have fewer children if they are educated, have the ability to control their own fertility, earn an income of their own, and live in societies that do not suppress their rights. Although women make up roughly half of the world’s population, in most societies they have fewer rights and educational and economic opportunities than men have. Women do almost all of the world’s domestic work and child care for little or no pay and provide more unpaid health care (within their families) than do all of the world’s organized health-care services combined. They also do 60–80% of the work associated with growing food, gathering and hauling wood and animal dung for use as fuel, and hauling water in rural areas of Africa, Latin America, and Asia. As one Brazilian woman observed, “For poor women, the only holiday is when you are asleep.” Globally, women account for two-thirds of all hours worked but receive only 10% of the world’s income, and they own less than 2% of the world’s land. Women also make up 70% of the world’s poor and 64% of all 800 million illiterate adults. Because sons are more valued than daughters in many societies, girls are often kept at home to work instead of being sent to school. Globally, the number of
school-age girls who do not attend elementary school is more than 900 million—almost three times the entire U.S. population. Teaching women to read has a major impact on fertility rates and population growth. Poor women who cannot read often have an average of five to seven children, compared to two or fewer children in societies where almost all women can read. According to Thorya Obaid, executive director of the UN Population Fund, “Many women in the developing world are trapped in poverty by illiteracy, poor health, and unwanted high fertility. All of these contribute to environmental degradation and tighten the grip of poverty.” An increasing number of women in less-developed countries are taking charge of their lives and reproductive behavior. As it expands, such bottom-up change by individual women will play an important role in stabilizing populations, reducing poverty and environmental degradation, and allowing more access to basic human rights.
Planning for Babies Works Family planning provides educational and clinical services that help couples choose how many children to have and when to have them. Such programs vary from culture to culture, but most provide information on birth spacing, birth control, and health care for pregnant women and infants. Family planning has been a major factor in reducing the number of births throughout most of the world, mostly because of increased knowledge and availability of contraceptives. It has also reduced the number of abortions performed each year and has decreased the numbers of mothers and fetuses dying during pregnancy. CONCEPT 4-6
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Studies by the UN Population Division and other population agencies indicate that family planning is responsible for a drop of at least 55% in total fertility rates (TFRs) in less-developed countries, from 6.0 in 1960 to 2.7 in 2010. Between 1971 and 2009, for example, Thailand used family planning to cut its annual population growth rate from 3.2% to 0.6%, and reduced its TFR from 6.4 to 1.8 children per family. According to the UN, had there not been the sharp drop in TFRs since the 1970s, with all else equal, the world’s population today would be about 8.5 billion instead of 6.9 billion. Despite such successes, two problems remain. First, according to the UN Population Fund, 42% of all pregnancies in less-developed countries are unplanned and 26% end with abortion. Second, an estimated 201 million couples in less-developed countries want to limit their number of children and determine their spacing, but they lack access to family planning services. According to a recent study by the UN Population Fund and the Alan Guttmacher Institute, meeting women’s current unmet needs for family planning and contraception could each year prevent 52 million unwanted pregnancies, 22 million induced abortions, 1.4 million infant deaths, and 142,000 pregnancy-related deaths. Some analysts call for expanding family planning programs to include teenagers and sexually active unmarried women, who are excluded from many existing programs. Another suggestion is to develop programs that educate men about the importance of having fewer children and taking more responsibility for raising them. Proponents also call for greatly increased research on developing more effective and more acceptable birth control methods for men.
■ C AS E S T UDY
Slowing Population Growth in China: The One-Child Policy China has made impressive efforts to feed its people, bring its population growth under control, and encourage economic growth. Between 1972 and 2010, the country cut its crude birth rate in half and trimmed its TFR from 5.7 to 1.5 children per woman (Figure 4-18), compared to 2.1 in the United States. If current trends continue, China’s population is expected to peak by about 2025 at almost 1.5 billion and then to begin a slow decline to about 1.4 billion by 2050. Although China has moved 350 million people (an amount greater than the entire U.S. population) from extreme poverty to the middle class, nearly half of its people are struggling to live on the equivalent of less than $2 (U.S.) a day. In the 1960s, Chinese government officials concluded that the only alternative to mass starvation was strict population control, and they established the most extensive, intrusive, and strict family planning and population control program in the world. It strongly encourages people to limit their families to one child each. Married couples who pledge to have no more than one child receive more food, larger pensions, better housing, free health care, and other advantages. Couples who break their pledge lose such benefits. The government also provides married couples with free sterilization, contraceptives, and abortion. However, reports of forced abortions and other coercive actions have brought condemnation from the United States and other national governments.
India
17%
Percentage of world population
1.1 billion 1.3 billion
Population
1.4 billion
Population (2050) (estimated)
1.6 billion 47%
Illiteracy (% of adults)
17% 36%
Population under age 15 (%) Population growth rate (%) Total fertility rate
20% 1.6% 0.6% 2.9 children per women (down from 5.3 in 1970) 1.6 children per women (down from 5.7 in 1972)
Infant mortality rate
58 27 62 years
Life expectancy
Figure 4-18 Global connection: This graph shows basic demographic data for India and China. (Data from United Nations and Population Reference Bureau)
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China
20%
Percentage living below $2 per day GDP PPP per capita
73 years 80 47 $3,120 $5,890
Community Ecology, Population Ecology, and the Human Population
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In China, there is a strong preference for male children, because unlike sons, daughters are likely to marry and leave their parents. Some pregnant Chinese women use ultrasound to determine the gender of their fetus, and they get an abortion if the child is female. The result is a rapidly growing gender imbalance in China’s population, with a projected 30–40 million surplus of men expected by 2020. With fewer children, the average age of China’s population is increasing rapidly. By 2020, nearly one of every three Chinese will be over 60 years old, compared to one of ten in 2008. This graying of the Chinese population could lead to a declining work force and fewer children and grandchildren to care for the growing number of elderly people. These concerns and other factors may slow economic growth and lead to some relaxation of China’s one-child population control policy. China also faces serious resource and environmental problems that could limit its economic growth. It has 20% of the world’s population, but only 7% of the world’s freshwater and cropland, 4% of its forests, and 2% of its oil. China’s deputy minister of the environment summarized the country’s environmental problems: “Our raw materials are scarce, we don’t have enough land, and our population is constantly growing. Half of the water in our seven largest rivers is completely useless. One-third of the urban population is breathing polluted air.” China’s recent rapid industrialization has resulted in one of the fastest growing economies in the world. More middle-class Chinese will consume more resources per person, increasing China’s ecological footprint (see Figure 1-6, p. 13) within its own borders and in other parts of the world that provide it with resources. This will put a strain on the earth’s natural capital unless China steers a course toward more sustainable economic development. ■ CAS E S TUDY
Slowing Population Growth in India The world’s first national family planning program began in India in 1952, when its population was nearly 400 million. In 2010, after 58 years of population control efforts, India had 1.2 billion people—the world’s second largest population. In 1952, India added 5 million people to its population. In 2010, it added 18 million—more than any other country. Also, 32% of India’s population is under age 15 compared to 18% in China, which sets it up for further rapid population growth. (Figure 4-18 compares demographic data for India and China.) The United Nations projects that by 2015, India will be the world’s most populous country, and by 2050, it will have a population of 1.74 billion. India has the world’s fourth largest economy and a thriving and rapidly growing middle class of more than
50 million people. But the country faces a number of serious poverty, malnutrition, and environmental problems that could worsen as its population continues to grow rapidly. About one of every four of India’s urban population live in slums, and prosperity and progress have not touched many of the nearly 650,000 villages where more than two-thirds of India’s population lives. Nearly half of the country’s labor force is unemployed or underemployed, and about three-fourths of its people struggle to live on the equivalent of less than $2.25 a day. While China also has serious environmental problems, its poverty rate is only about half that of India. For decades, the Indian government has provided family planning services throughout the country and has strongly promoted a smaller average family size; even so, Indian women have an average of 2.6 children. Two factors help account for larger families in India. First, most poor couples believe they need several children to work and care for them in old age. Second, as in China, the strong cultural preference in India for male children means that some couples keep having children until they produce one or more boys. The result: even though 9 of every 10 Indian couples have access to at least one modern birth control method, only 48% actually use one (compared to 86% in China). Like China, India also faces critical resource and environmental problems. With 17% of the world’s people, India has just 2.3% of the world’s land resources and 2% of its forests. About half the country’s cropland is degraded as a result of soil erosion and overgrazing. In addition, more than two-thirds of its water is seriously polluted, sanitation services often are inadequate, and many of its major cities suffer from serious air pollution. India is undergoing rapid economic growth, which is expected to accelerate. As members of its growing middle class increase their resource use per person, India’s ecological footprint will expand and increase the pressure on the country’s and the earth’s natural capital. On the other hand, economic growth may help India to slow its population growth by accelerating its demographic transition.
It Is Possible to Reduce Population Growth Once every 10 years, the United Nations holds its Conference on Population and Development. The conference has established a population plan with major goals endorsed by 180 governments to do the following by 2015: •
Provide universal access to family planning services and reproductive health care.
•
Improve health care for infants, children, and pregnant women.
•
Develop and implement national population policies.
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•
Improve the status of women and expand educational and job opportunities for young women.
•
Increase the involvement of men in child-rearing responsibilities and family planning.
•
Sharply reduce poverty.
•
Sharply reduce unsustainable patterns of production and consumption.
The experiences of countries such as Japan, Thailand, South Korea, Taiwan, Iran, and China show that a country can achieve or come close to replacement-level fertility within a decade or two. Such experiences also suggest that the best ways to slow and stabilize population growth are through investing in family planning, reducing poverty, and elevating the social and economic status of women (Concept 4-6).
of species in different terrestrial and aquatic ecosystems provides alternative paths for energy flow and nutrient cycling, and better opportunities for natural selection as environmental conditions change. When we disrupt these paths, we can decrease the various components of the biodiversity of ecosystems. In this chapter, we looked more closely at the biodiversity sustainability principle, at how it promotes sustainability, and at the fact that there are always limits to population growth in nature. We also applied the concepts of biodiversity and population dynamics to the growth of the human population and its environmental impacts. We continue this exploration throughout the rest of this book. Here are this chapter’s three big ideas: ■ Each species plays a specific ecological role in the ecosystem where it is found (ecological niche).
The Principles of Sustainability Govern Populations
■ Certain interactions among species, along with other natural limits to population growth in nature, affect the resource use and population sizes of all species, including humans.
Populations of most plants and animals depend directly or indirectly on solar energy and each population plays a role in the cycling of nutrients in the ecosystems where it lives. In addition, the biodiversity found in the variety
■ We can slow human population growth by reducing poverty through economic development, elevating the status of women, and encouraging family planning.
We cannot command nature except by obeying her. SIR FRANCIS BACON
REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 67. What is an ecological niche? Distinguish between a niche and a habitat. Distinguish between specialist species and generalist species, and give an example of each. State three facts about cockroaches that demonstrate that they are generalist species. Distinguish among native, nonnative, indicator, keystone, and foundation species, and give an example of each. Explain why birds are excellent indicator species. Summarize the story of vanishing amphibians and their importance as indicator species. Explain why it might be a good idea to protect shark species. 2. Define interspecific competition, predation, parasitism, mutalism, and commensalism, and give an example of each. Describe and give an example of resource partitioning and explain how it can increase species diversity. Explain how each of these species interactions can affect the population sizes of species in ecosystems. Distinguish between a predator and a prey, and give an example of each. What is a predator–prey relationship?
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3. What is ecological succession? Distinguish between primary ecological succession and secondary ecological succession and give an example of each. Explain why succession does not follow a predictable path. Explain how living systems achieve some degree of stability or sustainability by undergoing constant change in response to changing environmental conditions. 4. Distinguish among the biotic potential, intrinsic rate of increase, environmental resistance, carrying capacity, exponential growth, and logistic growth of a population, and use these concepts to explain why there are always limits to population growth in nature. Define population crash and explain how it can occur. Explain why humans are not exempt from nature’s population controls. 5. Distinguish between opportunist and competitor species and give an example of each. Describe how each type of species increases its chances of species survival.
Community Ecology, Population Ecology, and the Human Population
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6. List three factors that account for the rapid increase in the world’s human population during the last 200 years. Explain how this growth is distributed geographically. How many people are likely to be living on earth in 2050? List three factors that affect the population change of any area and write an equation showing how they are related. Distinguish between crude birth rate and crude death rate. What five countries had the largest population numbers in 2010? 7. What is a fertility rate? Distinguish between replacement-level fertility rate and total fertility rate (TFR). Explain why reaching the replacement level fertility rate will not stop global population growth for at least 50 years (assuming that death rates do not rise). Describe population growth in the United States and explain why it is so high compared to most other developed countries. 8. List eight factors that can affect the birth rate and fertility rate of a country. Distinguish between infant mortality rate and life expectancy, and explain how they affect the population size of a country. Why does the United States have a higher infant mortality rate than a number
of other countries? What is migration? Describe immigration into the United States and the issues it raises. 9. What is the age structure of a population? Why is the number of people younger than 15 years of age an important statistic? In 2010, what percentage of the world population was younger than 15? Explain how age structure affects population growth and economic growth. What are some problems related to rapid population decline due to an aging population? 10. What is the demographic transition and what are its four stages? What factors could hinder some developing countries from making this transition? What is family planning? Describe the roles of family planning, reducing poverty, and elevating the status of women in slowing population growth. Describe and compare China’s and India’s efforts to control their population growth. Describe the relationships between human population growth and environmental sustainability.
Note: Key terms are in bold type.
CRITICAL THINKING 1. Suppose an invasive species of plants invades a forested area near where you live and crowds out most of the native vegetation on the floor of the woodland. Do you view this as a problem? Why or why not? 2. Use the second law of thermodynamics (p. 30) to help explain why predators are generally less abundant than their prey. 3. Explain why most species with a high capacity for population growth tend to have a small size (such as bacteria and flies), while those with a low capacity for population growth tend to be large (such as humans, elephants, and whales). 4. How would you determine whether a particular species found in a given area is a keystone species?
5. Identify a major local, national, or global environmental problem, and describe the role of population growth in this problem. 6. Should everyone have the right to have as many children as they want? Explain. Is your belief on this issue consistent with your environmental worldview? 7. Some people believe that our most important goal should be to sharply reduce the rate of population growth in lessdeveloped countries where 97% of the world’s population growth is expected to take place. Others argue that the most serious environmental problems stem from high levels of resource consumption per person in moredeveloped countries, which use 88% of the world’s resources and have much larger ecological footprints per person than do less-developed countries. What is your view on this issue? Explain.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 4 for many study aids and ideas for further
reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
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5
Sustaining Biodiversity: The Species Approach
Key Questions and Concepts 5-1
What are the trends in species extinction?
How do humans accelerate species extinction?
5-3
C O N C E P T 5 - 1 The current rate of species extinction is at least 100 times the rate that existed before modern humans arrived on earth, and is expected to increase to 1,000–10,000 times that background rate during this century.
C O N C E P T 5 - 3 The greatest threats to any species are (in order) loss or degradation of habitat, harmful invasive species, human population growth, pollution, climate change, and overexploitation.
5-2
Why should we care about the rising rate of species extinction?
5-4
C O N C E P T 5 - 2 We should avoid speeding up the extinction of wild species because of the ecological and economic services they provide, and because many people believe that these species have a right to exist regardless of their usefulness to us.
C O N C E P T 5 - 4 We can reduce the rising rate of species extinction and help to protect overall biodiversity by establishing and enforcing national environmental laws and international treaties, creating a variety of protected wildlife sanctuaries, and taking precautionary measures to prevent such harm.
How can we protect wild species from extinction resulting from our activities?
The last word in ignorance is the person who says of an animal or plant: “What good is it?” . . . If the land mechanism as a whole is good, then every part of it is good, whether we understand it or not. Harmony with land is like harmony with a friend; you cannot cherish his right hand and chop off his left. ALDO LEOPOLD
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Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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5-1
What Are the Trends in Species Extinction?
▲
CONC EPT 5-1 The current rate of species extinction is at least 100 times the rate that existed before modern humans arrived on earth, and is expected to increase to 1,000–10,000 times that background rate during this century.
Extinctions Are Natural but Sometimes They Increase Sharply
The Passenger Pigeon: Gone Forever
Recall that scientists have estimated a continuous, low rate of extinction of species during most of the history of life on earth, known as background extinction. Before humans came on the scene, this background extinction rate was roughly one extinct species per million species per year. This amounted to an extinction rate of about 0.0001% per year. The balance between formation of new species and extinction of existing species determines the earth’s biodiversity. Overall, the earth’s biodiversity has increased. But scientific evidence indicates that the earth has experienced five mass extinctions (see Chapter 3, p. 55) when 50–95% of the world’s species appear to have become extinct. After each mass extinction, biodiversity eventually returned to equal or higher levels, but each recovery required millions of years. Biologists distinguish among three levels of species extinction. Local extinction occurs when a species is no longer found in an area it once inhabited but is still found elsewhere in the world. Most local extinctions involve losses of one or more populations of species. Ecological extinction occurs when so few members of a species are left that it can no longer play its ecological roles in the biological communities where it is found. When a species can no longer be found anywhere on the earth, it has suffered biological extinction. Biological extinction is forever and represents an irreversible loss of natural capital (Figure 5-1 and the Case Study that follows).
In 1813, bird expert John James Audubon saw a single, huge flock of passenger pigeons that took three days to fly over him and was so dense that it darkened the skies. By 1900, North America’s passenger pigeon (Figure 5-1, left), once the most numerous bird species on earth, had disappeared from the wild because of a combination of uncontrolled commercial hunting and habitat loss as forests were cleared to make room for farms and cities. These birds were good to eat, their feathers made good pillows, and their bones were widely used for fertilizer. They were easy to kill because they flew in gigantic flocks and nested in long, narrow, densely packed colonies. Beginning in 1858, passenger pigeon hunting became a big business. Hunters used shotguns, traps, artillery, and even dynamite. People burned grass or sulfur below the birds’ roosts to suffocate them. Shooting galleries used live birds as targets. In 1878, one professional pigeon trapper made $60,000 by killing 3 million birds at their nesting grounds near Petoskey, Michigan. By the early 1880s, only a few thousand birds remained. At that point, recovery of the species was doomed because each female laid only one egg per nest each year. On March 24, 1900, a young boy in the U.S. state of Ohio shot the last known wild passenger pigeon. The last passenger pigeon on earth, a hen named Martha after Martha Washington, died in the Cincinnati Zoo in 1914. Her stuffed body is now on view at the National Museum of Natural History in Washington, DC.
Passenger pigeon
Great auk
Dodo
■ C AS E S T UDY
Golden toad
Figure 5-1 Lost natural capital: These are some of the bird species that have become prematurely extinct largely because of human activities, mostly habitat destruction and overhunting.
Aepyornis (Madagascar)
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Some Human Activities Are Causing Extinctions Extinction is a natural process. But a growing body of scientific evidence indicates that it has accelerated as human populations have spread over most of the globe, consuming huge quantities of resources and creating large and growing ecological footprints (see Figure 1-6, p. 13). According to biodiversity expert Edward O. Wilson, “The natural world is everywhere disappearing before our eyes—cut to pieces, mowed down, plowed under, gobbled up, replaced by human artifacts.” According to the 2005 Millennium Ecosystem Assessment and other studies, humans have taken over and disturbed at least half of, and more likely, about 80% of, the earth’s land surface. Most of these disturbances involve filling in wetlands or converting grasslands and forests to crop fields and urban areas. Human activities have also polluted and disturbed almost half of the surface waters that cover about 71% of the earth’s surface. According to the International Union for the Conservation of Nature (IUCN), the world’s largest and oldest global environmental network, this has greatly increased the rate at which species are disappearing or are being threatened with extinction.
Extinction Rates Are Rising Rapidly Although extinction is a natural biological process, it has accelerated as human populations have spread over the globe, consuming large quantities of resources. As a result, human activities are destroying the earth’s biodiversity at an unprecedented and accelerating rate. Biologists have used certain methods (Science Focus, p. 96) to estimate that the current annual rate of species extinction is at least 100 times the background extinction rate that existed before modern humans appeared about 200,000 years ago. This amounts to an extinction rate of 0.01% a year. Conservation biologists project that the extinction rate caused by habitat loss, overhunting, and other human activities will increase by a factor of 1,000–10,000 during this century (Concept 5-1), amounting to an annual extinction rate of 0.1% to 1% per year. So why is this a big deal? A 1% per year species extinction rate might not seem like much. But according to biodiversity researchers Edward O. Wilson and Stuart Pimm, at a 1% extinction rate, at least one-fourth and as many as half of the world’s current animal and plant species could vanish by the end of this century. In the words of biodiversity expert Norman Myers, “Within just a few human generations, we shall—in the absence of greatly expanded conservation efforts— impoverish the biosphere to an extent that will persist for at least 200,000 human generations or twenty times longer than the period since humans emerged as a species.” If such estimates are only half correct, we can see
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why many biologists warn that such a massive loss of biodiversity within the span of a single human lifetime is one of the most important and long-lasting environmental problem that humanity faces. In fact, most extinction experts consider a projected extinction rate of 1% a year to be on the low side, for several reasons. First, both the rate of species loss and the extent of biodiversity losses are likely to increase sharply during the next 50–100 years because of the projected growth of the human population and its growing use of resources. Second, current and projected extinction rates are much higher than the global average in parts of the world that are already highly endangered centers of biodiversity. Biodiversity researchers urge us to focus our efforts on slowing the much higher rates of extinction in such biodiversity hotspots; they see this emergency action as the best and quickest way to protect much of the earth’s biodiversity from being lost during this century. (We discuss this further in Chapter 6.) Third, we are eliminating, degrading, fragmenting, and simplifying many biologically diverse environments—such as tropical forests, tropical coral reefs, wetlands, and estuaries—that serve as potential colonization sites for the emergence of new species. Thus, in addition to increasing the rate of extinction, we may be limiting the long-term recovery of biodiversity by reducing the rate of speciation for some species. In other words, we are also creating a speciation crisis. In addition, Philip Levin, Donald Levin, and other biologists argue that, while our activities are likely to reduce the speciation rates for some species, they might help to increase the speciation rates for other rapidly reproducing opportunist species such as weeds and rodents, as well as cockroaches and other insects. This could further accelerate the extinction of other species that are likely to be crowded out of their habitats by these expanding generalist species.
Endangered and Threatened Species Are Ecological Smoke Alarms Biologists classify species that are heading toward biological extinction as either endangered or threatened. An endangered species has so few individual survivors that the species could soon become extinct. A threatened species (also known as a vulnerable species) still has enough remaining individuals to survive in the short term, but because of declining numbers, it is likely to become endangered in the near future. The IUCN—also known as the World Conservation Union—is a coalition of the world’s leading conservation groups. Since the 1960s, it has published annual Red Lists, which have become the world standard for listing the world’s threatened species. The list includes many thousands of plants and animals that are in danger of extinction. You can examine the Red Lists database online at www.iucnredlist.org. Figure 5-2 shows
Sustaining Biodiversity: The Species Approach
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Grizzly bear
Kirkland’s warbler
Knowlton cactus
Florida manatee
African elephant
Utah prairie dog
Swallowtail butterfly
Humpback chub
Golden lion tamarin
Siberian tiger
Giant panda
Black-footed ferret
Whooping crane
Northern spotted owl
Mountain gorilla
Florida panther
California condor
Hawksbill sea turtle
Blue whale
Black rhinoceros
Figure 5-2 Endangered natural capital: Some species that are endangered or threatened with extinction largely because of human activities are shown here. Almost 30,000 of the world’s species and 1,300 of those in the United States are officially listed as being in danger of becoming extinct. Most biologists believe the actual number of species at risk is much larger.
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a few of the species officially listed as endangered and protected under the U.S. Endangered Species Act. Some species have characteristics that increase their chances of becoming extinct (Figure 5-3). As biodiversity expert Edward O. Wilson puts it, “The first animal species to go are the big, the slow, the tasty, and those with valuable parts such as tusks and skins.”
Char ac t er i s t i c
Exa m p l e s
Low reproductive rate (K-strategist)
Blue whale, giant panda, rhinoceros
Specialized niche
Blue whale, giant panda, Everglades kite
Narrow distribution
Elephant seal, desert pupfish
Feeds at high trophic level
Fixed migratory patterns
Blue whale, whooping crane, sea turtle
Rare
African violet, some orchids
Commercially valuable
Figure 5-3 Some species have characteristics that can put them in greater danger of becoming extinct. Question: Which of these characteristics might possibly have contributed to the extinction of the passenger pigeon?
Bengal tiger, bald eagle, grizzly bear
Large territories
Snow leopard, tiger, elephant, rhinoceros, rare plants and birds
California condor, grizzly bear, Florida panther
SCIE N C E FO C US Estimating Extinction Rates
A
n extinction rate is expressed as a percentage or number of species that go extinct within a certain time such as a year. Scientists who try to catalog extinctions, estimate past extinction rates, and project future rates face three problems. First, because the natural extinction of a species typically takes a very long time, it is not easy to document. Second, we have identified only about 1.9 million of the world’s estimated 8 million to 100 million species. Third, scientists know little about the nature and ecological roles of most of the species that have been identified. One approach to estimating future extinction rates is to study records documenting
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the rates at which mammals and birds (the easiest to observe) have become extinct since humans began dominating the planet about 10,000 years ago. We can compare this information with fossil records of extinctions that occurred before that time. Another approach is to observe how reductions in habitat size affect extinction rates. The species–area relationship suggests that, on average, a 90% loss of habitat in a given area causes the extinction of about 50% of the species living in that area. Scientists also use mathematical models to estimate the risk of a particular species becoming endangered or extinct within a certain period of time. These models include
factors such as trends in population size, changes in habitat availability, interactions with other species, and genetic factors. Researchers know that their estimates of extinction rates are based on inadequate data and sampling, and on incomplete models. Thus, they are continually striving to get better data and to improve the models they use to estimate extinction rates. Critical Thinking Does the fact that the data, models, and estimates are imperfect give us a reason for doing nothing to prevent extinctions that are caused by human activities? Explain.
Sustaining Biodiversity: The Species Approach
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5-2
Why Should We Care about the Rising Rate of Species Extinction?
▲
CONC EPT 5-2 We should avoid speeding up the extinction of wild species because of the ecological and economic services they provide, and because many people believe that these species have a right to exist regardless of their usefulness to us.
Species Are a Vital Part of the Earth’s Natural Capital If all species eventually become extinct, why should we worry about the rate of extinction? Does it matter if polar bears, orangutans, or some unknown plant or insect in a tropical forest becomes extinct primarily because of human activities? Speciation results in new species eventually evolving to take the places of those species lost through mass extinctions. So why should we care if we speed up the extinction rate over the next 50–100 years? According to several analysts, there are at least three major reasons why we should work to prevent our activities from causing the extinction of other species. First, biodiversity researchers say we should act now to keep from hastening the extinction of species if only because of their instrumental value—their usefulness to us in the form of many of the ecological and eco-
Rauvolfia Rauvolfia sepentina, Southeast Asia Anxiety, high blood pressure
Pacific yew Taxus brevifolia, Pacific Northwest Ovarian cancer
Foxglove Digitalis purpurea, Europe Digitalis for heart failure
nomic services that make up the earth’s natural capital (see Figure 1-3, p. 8). For example, we depend on some insects for pollination of food crops and on some birds for natural pest control. In addition, some plant species provide economic value in the form of food crops, fuelwood and lumber, paper, and medicine (Figure 5-4). According to a 2005 United Nations University report, 62% of all cancer drugs were derived from tropical forest plants. Species diversity also provides economic benefits through ecotourism, which generates more than $1 million per minute in tourist expenditures. Conservation biologist Michael Soulé estimates that a male lion living to age 7 generates about $515,000 in tourist dollars in Kenya, but only about $1,000 if killed for its skin. Similarly, over a lifetime of 60 years, a Kenyan elephant is worth about $1 million in ecotourism revenue—many times more than its tusks are worth when they are sold illegally for their ivory.
Rosy periwinkle Cathranthus roseus, Madagascar Hodgkin's disease, lymphocytic leukemia
Cinchona Cinchona ledogeriana, South America Quinine for malaria treatment
Neem tree Azadirachta indica, India Treatment of many diseases, insecticide, spermicide
Figure 5-4 Natural capital: These plant species are examples of nature’s pharmacy. Parts of these plants (many of them found in tropical forests) are used to treat a variety of human ailments and diseases. Nine of the ten leading prescription drugs originally came from wild organisms. About 2,100 of the 3,000 plants identified by the National Cancer Institute as sources of cancer-fighting chemicals come from tropical forests. Despite their economic and health potential, fewer than 1% of the estimated 125,000 flowering plant species in tropical forests (and a mere 1,100 of the world’s 260,000 known plant species) have been examined for their medicinal properties. Once the active ingredients in the plants have been identified, they can usually be produced synthetically. Many of these tropical plant species are likely to become extinct before we can study them. Question: Which of these species, if any, might have helped you or people you know to deal with health problems?
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Another instrumental value is the genetic information that allows species to adapt to changing environmental conditions and to form new species. Genetic engineers use this information to produce new types of crops and foods. Carelessly eliminating many of the species making up the world’s vast genetic library is like burning books that we have never read. An equally important reason for trying to prevent human activities from hastening the extinction of species is that analysis of past mass extinctions indicates it will take 5 million to 10 million years—25 to 50 times longer than the amount of time that our species has been around—for natural speciation to rebuild the biodiversity that is likely to be lost during this century. As a result, any grandchildren you might have and hundreds of future generations are unlikely to be able to depend on the life-sustaining biodiversity that we now enjoy.
Are We Ethically Obligated to Prevent Speeding Up Extinction? Many people believe that each wild species has intrinsic or existence value based on its inherent right to exist and play its ecological roles, regardless of its usefulness to us (Concept 5-2). According to this view, we have an ethical responsibility to protect species from
5-3
How Do Humans Accelerate Species Extinction?
▲
C O NC EPT 5-3 The greatest threats to any species are (in order) loss or degradation of habitat, harmful invasive species, human population growth, pollution, climate change, and overexploitation.
Loss of Habitat Is the Single Greatest Threat to Species: Remember HIPPCO Figure 5-5 shows the underlying and direct causes of the endangerment and extinction of wild species. Biodiversity researchers summarize the most important direct causes of extinction resulting from human activities by using the acronym HIPPCO: Habitat destruction, degradation, and fragmentation; Invasive (nonnative) species; Population growth and increasing use of resources; Pollution; Climate change; and Overexploitation (Concept 5-3). According to biodiversity researchers, the greatest threat to wild species is habitat loss (Figure 5-6, p. 100), degradation, and fragmentation. A stunning example of this is the loss of habitat for polar bears (Case Study, p. 103), whose habitat is literally melting away beneath their feet.
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becoming extinct as a result of human activities and to prevent the degradation of the world’s ecosystems and their overall biodiversity. This ethical viewpoint raises a number of challenging questions. For example, since we cannot save all species, should we protect more animal species than plant species and, if so, which ones should we protect? Many people support protecting well-known and appealing species such as elephants, whales, tigers, and orangutans. But they sometimes forget about plants that serve as the base of the food supply for all species. Other people distinguish among various types of species. For example, they might think little about getting rid of species that they fear or hate, such as mosquitoes, cockroaches, disease-causing bacteria, snakes, and bats. Explore More: Go to www.cengage.com/ login to learn more about the important ecological roles that bats play and why we need to avoid causing their extinction. Some biologists caution us not to focus primarily on protecting relatively large organisms—the plants and animals we can see and are familiar with. They remind us that the true foundation of the earth’s ecosystems and ecological processes are invisible bacteria and the algae, fungi, and other microorganisms that decompose the bodies of larger organisms and recycle the nutrients needed by all life forms.
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Deforestation in tropical areas is the greatest eliminator of species, followed by the destruction and degradation of coral reefs and wetlands, the plowing of grasslands, and the pollution of streams, lakes, and oceans. Globally, temperate biomes have been affected more by habitat loss and degradation than have tropical biomes because of widespread economic development in temperate countries since 1800. Such development is now shifting to many tropical biomes. Island species—many of them endemic species found nowhere else on earth—are especially vulnerable to extinction when their habitats are destroyed, degraded, or fragmented. Any habitat surrounded by a different one can be viewed as a habitat island for most of the species that live there. Most national parks and other nature reserves are habitat islands, many of them encircled by potentially damaging logging, mining, energy extraction, and industrial activities. Freshwater lakes are also habitat islands that are especially vulnerable to the introduction of nonnative species and pollution.
Sustaining Biodiversity: The Species Approach
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Natural Capital Degradation Causes of Depletion and Extinction of Wild Species Underlying Causes •
Population growth
•
Rising resource use
•
Undervaluing natural capital
•
Poverty
Direct Causes •
Habitat loss
•
Pollution
•
Commercial hunting and poaching
•
Habitat degradation and fragmentation
•
Climate change
•
Sale of exotic pets and decorative plants
•
Introduction of nonnative species
•
Overfishing
•
Predator and pest control
Figure 5-5 Certain human activities have become underlying and direct causes of the depletion and extinction of wild species (Concept 5-3). The biggest cause is habitat loss, degradation, and fragmentation. This is followed by the deliberate or accidental introduction of harmful invasive (nonnative) species into ecosystems. Question: What are two direct causes that are specifically related to each of the underlying causes?
Habitat fragmentation occurs when a large, intact area of habitat such as a forest or natural grassland is divided, typically by roads, logging operations, crop fields, and urban development, into habitat islands. This process can decrease tree cover in forests and block animal migration routes. It can divide populations of a species into smaller, increasingly isolated groups that are more vulnerable to predators, competitor species, disease, and catastrophic events such as storms and fires. It also creates barriers that limit the abilities of some species to disperse and colonize new areas, to locate adequate food supplies, and to find mates.
Some Deliberately Introduced Species Can Disrupt Ecosystems After habitat loss and degradation, the biggest cause of animal and plant extinctions is the deliberate or accidental introduction of harmful invasive species into ecosystems (Concept 5-3). Most species introductions have been benefi- GOOD cial to us. According to a study by ecologist David NEWS Pimentel, introduced species such as corn, wheat, rice, and other food crops, as well as cattle, poultry, and other livestock provide more than 98% of the U.S. food supply. Similarly, nonnative tree species are grown in about 85% of the world’s tree plantations. Some deliberately introduced species have also helped to control pests. The problem is that, in their new habitats, some introduced species face no natural predators, competi-
tors, parasites, or pathogens that would help to control their numbers in their original habitats. Such nonnative species (Figure 5-7, p. 101) can thus crowd out populations of many native species, trigger ecological disruptions, cause human health problems, and lead to economic losses. According to the U.S. Fish and Wildlife Service, about 40% of the species listed as endangered in the United States and 95% of those in the U.S. state of Hawaii are on the list because of threats from invasive species. A prominent example is the European wild boar, introduced in the southeastern United States by hunters. Biologists estimate that there are now about 4 million European wild boars in Florida, Texas, and 22 other states. They eat almost anything, compete for food with endangered animals, use their noses to root up farm fields, and cause traffic accidents when they wander onto roads. Game and wildlife officials have failed to control their numbers through hunting and trapping, and some say there is no way to stop them.
Some Accidentally Introduced Species Can Disrupt Ecosystems Many unwanted nonnative invaders arrive from other continents as stowaways on aircraft, in the ballast water of tankers and cargo ships, and as hitchhikers on imported products such as wooden packing crates. Cars and trucks can also spread the seeds of nonnative CONCEPT 5-3
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Indian Tiger
Black Rhino
Range 100 years ago
Range in 1700
Range today
Range today
African Elephant
Asian or Indian Elephant
Former range Probable range 1600
Range today
Range today Figure 5-6 Natural capital degradation: These maps reveal the reductions in the habitat areas, or ranges, of four wildlife species. What will happen to these and millions of other species during the next few decades when, as is projected by scientists, the human population grows by billions and per capita resource consumption rises sharply? Question: Would you support expanding these ranges even though this would reduce the land available for human habitation and farming? Explain. (Data from International Union for the Conservation of Nature and World Wildlife Fund)
plant species embedded in their tire treads. Many tourists return home with living plants that can multiply and become invasive. Some of these plants might also contain insects that can escape, multiply rapidly, and threaten crops. An example is the extremely aggressive Argentina fire ant (Figure 5-8, p. 102), accidentally introduced into the United States in the 1930s, probably in a ship’s cargo arriving from South America. Without natural predators, fire ants have spread rapidly over much of the southern United States. When they invade an
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area, they can wipe out as much as 90% of native ant populations. Mounds containing fire ant colonies cover many fields and yards. When a mound is disturbed, tens of thousands of ants can swarm out and attack an intruder with painful, burning stings. They have killed deer fawns, birds, livestock, pets, and at least 80 people who were allergic to their venom. Another example of an accidentally introduced harmful invasive species involves several species of snakes, imported as part of the international pet trade, that have invaded Florida’s Everglades (USA).
Sustaining Biodiversity: The Species Approach
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Deliberately Introduced Species
Purple loosestrife
European starling
African honeybee (“Killer bee”)
Nutria
Salt cedar (Tamarisk)
Marine toad (Giant toad)
Water hyacinth
Japanese beetle
Hydrilla
European wild boar (Feral pig)
Accidentally Introduced Species
Sea lamprey (attached to lake trout)
Argentina fire ant
Brown tree snake
Eurasian ruffe
Common pigeon (Rock dove)
Formosan termite
Zebra mussel
Asian long-horned beetle
Asian tiger mosquito
Gypsy moth larvae
Figure 5-7 These are some of the more than 7,100 harmful invasive (nonnative) species that, after being deliberately or accidentally introduced into the United States, have caused ecological and economic harm.
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Prevention Is the Best Way to Reduce Threats from Invasive Species Once a harmful nonnative species becomes established in an ecosystem, its removal is almost impossible— somewhat like trying to put smoke back into a chimney. Clearly, the best way to limit the harmful impacts of nonnative species is to prevent them from being introduced and becoming established. Scientists suggest several ways to do this. One is to identify the major characteristics that allow species to become successful invaders and the types of ecosystems that are vulnerable to invaders (Figure 5-9). Then greatly increased ground surveys and satellite observations could be used to detect and monitor species invasions. We could also:
Figure 5-8 The Argentina fire ant, introduced accidentally into Mobile, Alabama, in 1932 from South America (lighter shaded area), has spread over much of the southern United States (darker shaded area). This invader is also found in Puerto Rico, New Mexico, and California. Question: How might this accidental introduction of fire ants have been prevented? (Data from S. D. Porter, Agricultural Research Service, U.S. Department of Agriculture)
■ CAS E STUDY
Snakes in the Everglades Burmese and African pythons and several species of boa constrictors have accidentally ended up in the subtropical wetlands of the U.S. state of Florida’s Everglades. About a million of these snakes, imported from Africa and Asia, have been sold as pets. After learning that these reptiles did not make good pets, some owners dumped them into the Everglades. Some of these snake species can live 25–30 years, reach 6 meters (20 feet) in length, weigh more than 90 kilograms (200 pounds), and be as big around as a telephone pole. They are hard to find and kill, and they reproduce rapidly. They seize their prey with their sharp teeth, wrap themselves around the prey, and squeeze it to death before feeding on it. They have huge appetites, devouring a variety of birds, raccoons, pet cats and dogs, and full-grown deer. Pythons have been known to eat American alligators—a keystone species in the Everglades ecosystem and the only predator in the Everglades capable of killing these snakes. According to wildlife officials, tens of thousands of these snakes now live in the Everglades and their numbers are increasing rapidly. It is feared that they will spread to other swampy wetlands in the southern half of the United States by the end of this century.
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•
Step up inspection of imported goods and goods carried by travelers that are likely to contain invader species.
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Identify major harmful invader species and pass international laws banning their transfer from one country to another, as is now done for endangered species.
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Require cargo ships, before entering ports, to discharge their ballast water and replace it with saltwater at sea, or require ships to sterilize ballast water or pump nitrogen into the water to displace dissolved oxygen and kill most invader organisms.
•
Increase research to find and introduce natural predators, parasites, bacteria, and viruses to control populations of established invaders.
Finally, each of us can take measures in our own lives to address this problem. Figure 5-10 shows GOOD some of the things you can do to help prevent or NEWS slow the spread of harmful invasive species.
Characteristics of Successful Invader Species
Characteristics of Ecosystems Vulnerable to Invader Species
High reproductive rate, short generation time
Climate similar to habitat of invader
Pioneer species
Absence of predators on invading species
Long lived
Early successional systems
High dispersal rate Generalists
Low diversity of native species Absence of fire
High genetic variability Disturbed by human activities
Figure 5-9 Some general characteristics of successful invader species and ecosystems vulnerable to invading species are shown here. Question: Which, if any, of the characteristics on the righthand side could humans influence?
Sustaining Biodiversity: The Species Approach
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What Can You Do? DDT in fish-eating birds (ospreys) 25 ppm
Controlling Invasive Species ■
Do not capture or buy wild plants and animals.
■
Do not remove wild plants from their natural areas.
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Do not release wild pets back into nature.
■
Do not dump the contents of an aquarium into waterways, wetlands, or storm drains.
■
When camping, use wood found near your campsite instead of bringing firewood from somewhere else.
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Do not dump unused bait into waterways.
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After dogs visit woods or the water, brush them before taking them home.
■
After each use, clean your mountain bike, canoe, boat, motor, and trailer, all fishing tackle, hiking boots, and other gear before heading for home.
Figure 5-10 Individuals matter: Here is a list of some ways to prevent or slow the spread of harmful invasive species. Questions: Which two of these actions do you think are the most important? Why? Which of these actions do you plan to take?
Population Growth, Overconsumption, Pollution, and Climate Change Can Cause Species Extinctions Past and projected human population growth and excessive and wasteful consumption of resources have greatly expanded the human ecological footprint, which has crowded many species out of their habitats and taken the resources they need to survive. Acting together, these two factors have caused the extinction of many species (Concept 5-3). Pollution also threatens some species with extinction, as has been shown by the unintended effects of certain pesticides. According to the U.S. Fish and Wildlife Service, pesticides annually kill about one-fifth of the honeybee colonies that pollinate almost a third of U.S. food crops. They also kill more than 67 million birds and 6–14 million fish every year, and they threaten about one-fifth of the country’s endangered and threatened species. During the 1950s and 1960s, populations of fisheating birds such as ospreys, brown pelicans, and bald eagles plummeted. A chemical derived from the pesticide DDT, when biologically magnified in food webs (Figure 5-11), made the birds’ eggshells so fragile they could not reproduce successfully. Also hard hit were such predatory birds as the prairie falcon, sparrow hawk, and peregrine falcon, which help to control populations of rabbits, ground squirrels, and other crop eaters. Since the U.S. ban on DDT in 1972, most of GOOD NEWS these bird species have made a comeback.
DDT in large fish (needlefish) 2 ppm DDT in small fish (minnows) 0.5 ppm
DDT in zooplankton 0.04 ppm DDT in water 0.000003 ppm, or 3 ppt
Figure 5-11 Bioaccumulation and biomagnification: DDT is a fat-soluble chemical that can accumulate in the fatty tissues of animals. In a food web, the accumulated DDT is biologically magnified in the bodies of animals at each higher trophic level. (Dots in this figure represent DDT.) The concentration of DDT in the fatty tissues of organisms was biomagnified about 10 million times in this food chain in an estuary near Long Island Sound in the U.S. state of New York. If each phytoplankton organism takes up and retains one unit of DDT, a small fish eating thousands of zooplankton (which feed on the phytoplankton) will store thousands of units of DDT in its fatty tissue. Each large fish that eats ten of the smaller fish will ingest and store tens of thousands of units, and each bird (or human) that eats several large fish will ingest hundreds of thousands of units. Question: How does this story demonstrate the value of pollution prevention?
According to a 2004 study by Conservation International, projected climate change could help drive a quarter to half of all land animals and plants to extinction by the end of this century. Scientific studies indicate that polar bears (see the Case Study that follows) and 10 of the world’s 17 penguin species are already threatened because of higher temperatures and melting sea ice in their polar habitats. ■ C AS E S T UDY
Polar Bears and Climate Change The world’s 20,000–25,000 polar bears are found in 19 populations scattered across the frozen arctic regions of Canada, Denmark, Norway, Russia, and the U.S. state of Alaska. Throughout the winter, polar bears hunt for seals on floating sea ice that expands southward each winter and shrinks back as the temperature rises during summer. By eating the seals, the bears build up their body fat. In the summer and fall, they live off this fat until hunting resumes when the ice expands again during winter. Measurements reveal that the earth’s atmosphere is getting warmer and that this warming is occurring twice as fast in the Arctic as in the rest of the world. Hence, CONCEPT 5-3
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the average annual area of floating sea ice in the Arctic is decreasing, and this ice is breaking up earlier each year, shortening the polar bears’ hunting season. These changes mean that polar bears have less time to feed and store fat. As a result, they must fast longer, which weakens them. As females become weaker, their ability to reproduce and keep their young cubs alive declines. Polar bears are strong swimmers, but ice shrinkage has forced them to swim longer distances to find enough food and to spend more time during winter hunting on land, where it is nearly impossible for them to find enough prey. As the bears grow hungrier, they are more likely to go to human settlements looking for food, which gives people the mistaken impression that their population is growing. In 2008, the U.S. Fish and Wildlife Service placed the Alaskan polar bear on its list of threatened species. According to a 2006 study by the IUCN, the world’s total polar bear population is likely to decline 30–35% by 2050. At the end of this century, polar bears might be found only in zoos.
Illegal Killing, Capturing, and Selling of Wild Species Threatens Biodiversity Some protected species are illegally killed for their valuable parts or are sold live to collectors. Such poaching endangers many larger animals and some rare plants. To poachers, animals such as mountain gorillas, giant pandas, chimpanzees, and Komodo dragon lizards are each worth thousands of dollars. Wildlife smuggling is another high-profit, low-risk, rapidly growing business, attractive to organized crime, because few of the smugglers are caught or punished. At least two-thirds of all live animals smuggled around the world die in transit. To poachers, a highly endangered, live mountain gorilla is worth $150,000; a pelt of a critically endangered giant panda (less than 1,600 left in the wild in China) $100,000; a live chimpanzee $50,000; and a live Komodo dragon lizard from Indonesia $30,000. A poached rhinoceros horn can be worth as much as $55,500 per kilogram ($25,000 per pound). Rhinoceros are killed for no other reason than to harvest their horns, which are used to make dagger handles in the Middle East and as a fever reducer and alleged aphrodisiac in China and other parts of Asia. Every year, about 25,000 African elephants are killed illegally for their valuable ivory tusks despite an international ban since 1989 on the sale of poached ivory. Across the globe, the legal and illegal trade in wild species for use as pets is also a huge and very profitable business. Many owners of wild pets do not know that, for every live animal captured and sold in the pet market, many others are killed or die in transit. More than 60 bird species, mostly parrots, are endangered or
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threatened because of this wild-bird trade. (See the Case Study that follows.) Other wild species whose populations are depleted because of the pet trade include many amphibians, various reptiles, some mammals, and tropical fishes. Divers catch tropical fish by using plastic squeeze bottles of poisonous cyanide to stun them. For each fish caught alive, many more die. In addition, some exotic plants, especially orchids and cacti, are endangered because they are gathered (often illegally) and sold to collectors to decorate houses, offices, and landscapes. In Thailand, a biologist named Pilai Poonswad decided to do something about poachers who were taking Great Indian hornbills—large, beautiful, and rare birds—from a rain forest. She visited the poachers in their villages and showed them why the birds are worth more alive than dead. Largely because of her efforts, some former poachers now earn money by taking ecotourists into the forest to see these magnificent birds. Because of their financial interest in preserving the hornbills, they now help protect the birds from poachers. Individuals matter. ■ C AS E S T UDY
A Disturbing Message from the Birds Approximately 70% of the world’s nearly 10,000 known bird species are declining in numbers, and much of this decline is clearly related to human activities, summarized by HIPPCO. First, roughly one of every eight bird species is threatened by habitat loss, degradation, and fragmentation, according to the IUCN. About three-fourths of the threatened bird species live in forests, many of which are being fragmented or cleared at a rapid rate on all continents, but especially in the tropical areas of Asia and Latin America (Figure 5-12). Birds that live in grasslands are facing the same threat. In addition, the populations of 40% of the world’s aquatic birds are in decline because of the global loss of wetlands. The intentional or accidental introduction of nonnative species such as bird-eating rats is the second greatest danger to bird species, affecting nearly a third of the world’s threatened birds. Countless birds are exposed to oil spills, pesticides, and herbicides that destroy their habitats. And many birds, especially waterfowl, are threatened by lead poisoning when they eat lead shotgun pellets that fall into wetlands and lead sinkers left by anglers. Industrialized fishing fleets also pose a threat to many diving birds that drown after becoming hooked on baited lines or trapped in huge nets that are set out by fishing boats. As a result, at least 23 species of seabirds, including albatrosses, face extinction. The greatest new threat to birds is climate change. A 2006 review of more than 200 scientific articles done for the WWF found that climate change is causing
Sustaining Biodiversity: The Species Approach
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Figure 5-12 This map shows the distribution of bird species in North America and Latin America. Question: Why do you think more bird species are found in Latin America than in North America? (Data from the Nature Conservancy, Conservation International, World Wildlife Fund, and Environment Canada)
Number of bird species 609
400
200
1
5-4
declines of some bird populations in every part of the globe. These declines are expected to increase sharply during this century. Finally, overexploitation is a major threat to bird populations. Fifty-two of the world’s 388 parrot species are threatened, partly because so many parrots are captured (often illegally) for the pet trade. They are taken from tropical areas and sold, usually to buyers in Europe and the United States. Biodiversity scientists view this decline of bird species with alarm. One reason is that birds are excellent environmental indicators because they live in every climate and biome, and respond quickly to environmental changes in their habitats. Their decline reflects the degraded environmental conditions all over the world.
How Can We Protect Wild Species from Extinction Resulting from Our Activities?
▲
CONC EPT 5-4 We can reduce the rising rate of species extinction and help to protect overall biodiversity by establishing and enforcing national environmental laws and international treaties, creating a variety of protected wildlife sanctuaries, and taking precautionary measures to prevent such harm.
International Treaties and National Laws Can Help to Protect Species Several international treaties and conventions help to protect endangered or threatened wild species (Concept 5-4). One of the most far reaching is the 1975 Convention on International Trade in Endangered Species (CITES). This treaty, signed by 175 countries, bans the hunting, capturing, and selling of threatened or endangered species. It also restricts the international trade of roughly 5,000 species of animals and 28,000 species of plants that are at risk of becoming threatened. CITES has helped to reduce the international trade of many threatened animals, including elephants, croc-
odiles, cheetahs, and chimpanzees. But the effects of this treaty are limited because enforcement varies from country to country, and convicted violators often pay only small fines. Also, member countries can exempt themselves from protecting any listed species, and much of the highly profitable illegal trade in wildlife and wildlife products goes on in countries that have not signed the treaty. The Convention on Biological Diversity (CBD), ratified by 191 countries, legally commits participating governments to reducing the global rate of biodiversity loss. However, because some key countries (including, as of 2010, the United States) have not ratified it, implementation has been slow. Also, the law contains no severe penalties or other enforcement mechanisms.
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The U.S. Endangered Species Act National laws can also be used to protect species. Probably the most far-reaching of such laws is the U.S. Endangered Species Act of 1973 (ESA; amended in 1982, 1985, and 1988). Canada and a number of other countries have similar laws. Under the ESA, the National Marine Fisheries Service (NMFS) is responsible for identifying and listing endangered and threatened ocean species, while the U.S. Fish and Wildlife Service (USFWS) is responsible for identifying and listing all other endangered and threatened species. Any decision by either agency to add a species to, or remove one from, the list must be based on biological factors alone, without consideration of economic or political factors. However, economic factors can be used in deciding whether and how to protect endangered habitat, and in developing recovery plans for listed species. The ESA also forbids federal agencies (except the Defense Department) from carrying out, funding, or authorizing projects that would jeopardize an endangered or threatened species, or destroy or modify its critical habitat. For offenses committed on private lands, fines as high as $100,000 and 1 year in prison can be imposed to ensure that the habitats of endangered species are protected. Although this provision has rarely been used, it is controversial because at least 90% of the listed species live totally or partially on private land. The ESA also makes it illegal for Americans to sell or buy any product made from an endangered or threatened species, or to hunt, kill, collect, or injure such species in the United States. Between 1973 and 2010, the number of U.S. species on the official endangered and threatened species lists increased from 92 to about 1,370. According to a study by the Nature Conservancy, one-third of the country’s species are at risk of extinction, and 15% of all species are at high risk—far more than the number listed. For each listed species, the USFWS or the NMFS is supposed to prepare a recovery plan that includes designation and protection of critical habitat. Examples GOOD of successful recovery plans include those for the NEWS American alligator, the gray wolf, the peregrine falcon, the bald eagle, and the brown pelican. The ESA also requires that all commercial shipments of wildlife and wildlife products enter or leave the country through one of nine designated ports. The 120 fulltime USFWS inspectors can inspect only a small fraction of the more than 200 million wild animals brought legally into the United States annually. Each year, tens of millions of wild animals are also brought in illegally, but few illegal shipments of endangered or threatened animals or plants are confiscated. Since 1982, the ESA has been amended to give private landowners economic incentives to help save endangered species living on their lands. The goal is to strike a compromise between the interests of private landowners and those of endangered and threatened
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species. The ESA has also been used to protect endangered and threatened marine reptiles (turtles) and mammals (especially whales, seals, and sea lions). Some believe that the ESA should be weakened or repealed, and others believe it should be strengthened and modified to focus on protecting ecosystems. Opponents of the act contend that it puts the rights and welfare of endangered plants and animals above those of people. They also argue that it has not been effective in protecting endangered species and has caused severe economic losses by hindering development on private lands. Since 1995, there have been numerous efforts to weaken the ESA and to reduce its already meager annual budget, which is less than what a beer company typically spends on two 30-second TV commercials during the annual U.S. football championship game, the Super Bowl. Other critics would go further and do away with this act. Most conservation biologists and wildlife scientists agree that the ESA needs to be simplified and streamlined. But they contend that it has not been a failure (Science Focus, at right).
We Can Establish Wildlife Refuges and Other Protected Areas In 1903, President Theodore Roosevelt established the first U.S. federal wildlife refuge at Pelican Island, Florida. It took more than a century but this protec- GOOD tion worked. In 2009, the brown pelican was NEWS removed from the U.S. Endangered Species list. Since then, the National Wildlife Refuge System has grown to include 548 refuges. Every year, more than 40 million Americans visit these refuges to hunt, fish, hike, and watch birds and other wildlife. More than three-fourths of the refuges serve as wetland sanctuaries that are vital for protecting migratory waterfowl. One-fifth of U.S. endangered and threatened species have habitats in the refuge system, and some refuges have been set aside for specific endangered species (Concept 5-4). Such areas have helped Florida’s key deer, the brown pelican, and the trumpeter swan to recover. Biodiversity scientists are urging the government to set aside more refuges for endangered plants. They also call on the U.S. Congress as well as on state legislatures to allow abandoned military lands that contain significant wildlife habitat to become national or state wildlife refuges.
Gene Banks, Botanical Gardens, and Wildlife Farms Can Help to Protect Species Gene or seed banks preserve genetic information and endangered plant species by storing their seeds in refrigerated, low-humidity environments. More than 100
Sustaining Biodiversity: The Species Approach
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S C I E NC E FO C U S Examining the Record of the Endangered Species Act
C
ritics of the ESA call it an expensive failure because only 37 species have been removed from the endangered list. Most biologists insist that it has not been a failure, for four reasons. First, species are listed only when they face serious danger of extinction. Arguing that the act is a failure is similar to arguing that a hospital emergency room that takes only the most desperate cases, should be shut down because it has not saved enough patients. Second, it takes decades for most species to become endangered or threatened. Not surprisingly, it also takes decades to bring a species in critical condition back to the point where it can be removed from the critical list. Expecting the ESA—which has been in existence only since 1973—to quickly repair the biological depletion that has taken place over many decades is unrealistic. Third, according to federal data, the conditions of more than half of the listed species
are stable or improving, and 99% of the protected species are still surviving. A hospital emergency room taking only the most desperate cases and then stabilizing or improving the conditions of more than half of those patients while keeping 99% of them alive would be considered an astounding success. Fourth, the 2010 budget for protecting endangered species amounted to an average expenditure of about 9¢ per U.S. citizen. To its supporters, it is amazing that the ESA, on such a small budget, has managed to stabilize or improve the conditions of more than half of the listed species. ESA supporters would agree that the act can be improved and that federal regulators have sometimes been too heavy handed in enforcing it. But instead of gutting or doing away with the ESA, some biologists call for it to be strengthened and modified. A study by the U.S. National Academy of Sciences rec-
seed banks around the world collectively hold about 3 million samples. A new underground vault on a remote island in the Arctic will eventually contain 100 million of the world’s seeds. It is not vulnerable to power losses, fires, storms, or war, as most other such banks are. The world’s 1,600 botanical gardens and arboreta contain living plants that represent almost one-third of the world’s known plant species. But they contain only about 3% of the world’s rare and threatened plant species and have too little space and funding to preserve most of those species. We can take pressure off some endangered or threatened species by raising individuals of these species on farms for commercial sale. In Florida, for example, alligators are raised on farms for their meat and hides. Butterfly farms established to raise and protect endangered species flourish in Papua, New Guinea, where many butterfly species are threatened by development activities.
Zoos and Aquariums Can Protect Some Species Zoos, aquariums, game parks, and animal research centers are being used to preserve some individuals of critically endangered animal species, with the long-term goal of reintroducing the species into protected wild habitats. Two techniques for preserving endangered terrestrial species are egg pulling and captive breeding. Egg pulling involves collecting wild eggs laid by critically endangered bird species and then hatching them in zoos or research centers. In captive breeding, some or all of the
ommended three major changes to make the ESA more scientifically sound and effective: 1. Greatly increase the meager funding for implementing the act. 2. Develop recovery plans more quickly. 3. When a species is first listed, establish a core of its habitat as critical, which would be a temporary emergency measure that could support the species for 25–50 years. Most biologists and wildlife conservationists believe that the United States needs a new law that emphasizes protecting and sustaining biological diversity and ecosystem functions rather than focusing mostly on saving individual species. (We discuss this idea further in Chapter 6.) Critical Thinking Should the U.S. Endangered Species Act be modified to protect and sustain the nation’s overall biodiversity more effectively? Explain.
wild individuals of a critically endangered species are collected for breeding in captivity, with the aim of reintroducing the offspring into the wild. Shortages of space and funding limit efforts to maintain breeding populations of endangered animal species in zoos and research centers. The captive population of an endangered species must number 100–500 individuals in order for it to avoid extinction through accident, disease, or loss of genetic diversity through inbreeding. Research indicates that 10,000 or more individuals are needed for an endangered species to maintain its capacity for biological evolution. Public aquariums that exhibit unusual and attractive species of fish and some marine animals such as seals and dolphins help to educate the public about the need to protect such species. But mostly because of limited funds, public aquariums have not served as effective gene banks for endangered marine species, especially marine mammals that need large volumes of water. Thus, zoos, aquariums, and botanical gardens are not biologically or economically feasible solutions for the growing problem of species extinction. Figure 5-13 (p. 108) lists some things you can do to help deal GOOD NEWS with this problem.
We Can Use the Principles of Sustainability to Protect Species The disappearance of the passenger pigeon in a short time was a blatant example of the effects of harmful human activities (Case Study, p. 93). Now, there is
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factors that will hasten the extinction of species, we will help to preserve the earth’s biodiversity and its vital role in the processes of energy flow and the cycling of matter within ecosystems, so critical to our own existence on this planet. Protecting biodiversity is no longer simply a matter of passing and enforcing endangered species laws and setting aside parks and preserves. It will also require slowing climate change that will affect many species and their habitats, and it will require reducing the size and impact of our ecological footprints (Figure 1-6, p. 13). Here are this chapter’s three big ideas:
What Can You Do? Protecting Species ■
Do not buy furs, ivory products, or other items made from endangered or threatened animal species.
■
Do not buy wood or paper products produced by cutting old-growth forests in the tropics.
■
Do not buy birds, snakes, turtles, tropical fish, and other animals that are taken from the wild.
■
Do not buy orchids, cacti, or other plants that are taken from the wild.
■
Spread the word. Talk to your friends and relatives about this problem and what they can do about it.
■ The rate of extinction of wild species has grown dramatically as humans have destroyed and degraded their habitats, introduced harmful invasive species, expanded the human population, generated pollution and climate change, and overexploited wildlife resources.
Figure 5-13 Individuals matter: You can help prevent the extinction of species. Questions: Which two of these choices do you believe are the most important? Why?
overwhelming evidence that humans might cause the extinction of as many as half of the world’s wild species within your lifetime. Ignorance of ecological principles accounts for some of the failure to deal with this problem. But to many, the most serious problem is our lack of political and ethical will to act on what we know. Being aware of the three principles of sustainability (see back cover) will help us to take the necessary actions. By acting to prevent the
■ We should avoid causing the extinction of wild species because of the ecological and economic services they provide and because their existence should not depend primarily on their usefulness to us. ■ We can work to avoid causing the extinction of species and to protect overall biodiversity by using laws and treaties, protecting wildlife sanctuaries, and shrinking our own ecological footprints.
The great challenge of the twenty-first century is to raise people everywhere to a decent standard of living while preserving as much of the rest of life as possible. EDWARD O. WILSON
REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 92. Distinguish among local, ecological, and biological extinction. What factors led to the premature extinction of the passenger pigeon in the United States? 2. About how many species are going extinct every year, according to scientists’ estimates? Give three reasons why many extinction experts consider these estimates to be conservative. Describe how scientists estimate extinction rates. 3. Distinguish between endangered species and threatened species. List five characteristics that make some species especially vulnerable to extinction.
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4. What are two reasons for trying to prevent our hastening of extinction of wild species? What is the instrumental value of a species? List four types of instrumental values provided by wild species. What is the intrinsic value of a species? Why do some biologists caution us not to focus primarily on protecting the relatively large organisms with which we are most familiar? 5. What is HIPPCO? In order, what are the six largest causes of extinction of species resulting from human activities? Why are island species especially vulnerable to extinction? What is habitat fragmentation and how does it relate to islands? List two reasons why we should be alarmed by the decline of bird species.
Sustaining Biodiversity: The Species Approach
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6. Give two examples of the harmful effects of nonnative species that have been introduced (a) deliberately and (b) accidentally. List five ways to limit the harmful impacts of nonnative species. 7. Describe the roles of population growth, overconsumption, pollution, and climate change in the premature extinction of wild species. Explain how pesticides such as DDT can be biomagnified in food chains and webs. Explain how climate change is threatening polar bears. 8. Describe (a) the poaching of wild species and (b) wildlife smuggling, and give three examples of species that are threatened by each of these illegal activities. How does the global pet trade fit into the problems described in this chapter? Give five examples of species threatened by the pet trade. Why are some animals worth more alive in the
wild than captured or killed? Describe the HIPPCO threats to bird species around the world. 9. Describe two international treaties that are used to help protect species. Describe the U.S. Endangered Species Act, how successful it has been, and the controversy over this act. Describe the roles of wildlife refuges, gene banks, botanical gardens, wildlife farms, zoos, and aquariums in protecting some species. 10. Describe how we can follow the three principles of sustainability in helping to protect wild species from premature extinction.
Note: Key terms are in bold type.
CRITICAL THINKING 1. List three ways in which you could apply Concept 5-3 (p. 98) to making your lifestyle more environmentally sustainable. 2. What are three aspects of your lifestyle that directly or indirectly contribute to the hastening of extinction of some bird species (Case Study, p. 104)? What are three things that you think should be done to reduce the extinction of birds? 3. Do you accept the ethical position that each species has the inherent right to survive without human interference, regardless of whether it serves any useful purpose for humans? Explain. Would you extend this right to the Anopheles mosquito, which transmits malaria, and to infectious bacteria? Explain. 4. Wildlife ecologist and environmental philosopher Aldo Leopold wrote, “To keep every cog and wheel is the first precaution of intelligent tinkering.” Explain how this statement relates to the material in this chapter.
c. I have the right to use wildlife habitat to meet my own needs. d. When you have seen one redwood tree, elephant, or any other form of wildlife, you have seen them all, so lock up a few of each species in a zoo or wildlife park and do not worry about protecting the rest. e. Wildlife should be protected. 6. Environmental groups in a heavily forested state want to restrict logging in some areas to save the habitat of an endangered squirrel. Timber company officials argue that the well-being of one type of squirrel is not as important as the well-being of the many families who would be affected if the restriction causes the company to lay off hundreds of workers. If you had the power to decide this issue, what would you do and why? Can you come up with a compromise? 7. List two questions that you would like to have answered as a result of reading this chapter.
5. Which of the following statements best describes your feelings toward wildlife? a. As long as it stays in its space, wildlife is okay. b. As long as I do not need its space, wildlife is okay.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 5 for many study aids and ideas for further
reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
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6
Sustaining Biodiversity: The Ecosystem Approach
Key Questions and Concepts What are the major threats to forest ecosystems?
threatened areas (biodiversity hotspots), restoring damaged ecosystems, and sharing as much of the earth’s land as possible with other species.
6-1
Unsustainable cutting and burning of forests, especially in tropical areas, is a potentially catastrophic problem because of the vital ecological services at risk and the growing contribution to projected climate change.
CONCEPT 6-1
How can we protect and sustain marine biodiversity?
6-5
We can help to sustain marine biodiversity by using laws and economic incentives to protect species, setting aside marine reserves to protect ecosystems, and using community-based integrated coastal management.
CONCEPT 6-5
How should we manage and sustain forests?
6-2
We can sustain forests by emphasizing the economic value of their ecological services, removing government subsidies that hasten their destruction, protecting old-growth forests, harvesting trees no faster than they are replenished, and planting trees.
CONCEPT 6-2
6-6 How should we protect and sustain freshwater biodiversity? C O N C E P T 6 - 6 We can help to sustain freshwater biodiversity by protecting the watersheds of lakes and streams, preserving wetlands, and restoring degraded freshwater systems.
How should we manage and sustain parks and nature reserves?
6-3
Sustaining biodiversity will require more effective protection of existing parks and nature reserves, as well as the protection of much more of the earth’s remaining undisturbed land area.
CONCEPT 6-3
What should be our priorities for sustaining terrestrial and aquatic biodiversity?
6-7
We can help to sustain the world’s biodiversity by mapping it, protecting biodiversity hotspots, creating large terrestrial and aquatic reserves, and carrying out ecological restoration of degraded terrestrial and aquatic ecosystems.
CONCEPT 6-7
6-4 What is the ecosystem approach to sustaining terrestrial biodiversity? C O N C E P T 6 - 4 We can help to sustain terrestrial biodiversity by identifying and protecting severely
There is no solution, I assure you, to save Earth’s biodiversity other than preservation of natural environments in reserves large enough to maintain wild populations sustainably. EDWARD O. WILSON
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Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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What Are the Major Threats to Forest Ecosystems?
6-1 ▲
Unsustainable cutting and burning of forests, especially in tropical areas, is a potentially catastrophic problem because of the vital ecological services at risk and the growing contribution to projected climate change.
CONC EPT 6-1
Forests Vary in Their Age, Makeup, and Origins Natural and planted forests occupy about 30% of the earth’s land surface (excluding Greenland and Antarctica). Tropical forests account for more than half of the world’s forest area, and boreal, or northern coniferous, forests account for about one-quarter of total forest area. Forest managers and ecologists classify natural forests into two major types based on their age and structure. The first type is old-growth forest, or uncut or regenerated forest that has not been seriously disturbed by human activities or natural disasters for 200 years or more. Old-growth forests are reservoirs of biodiversity because they provide ecological niches for a multitude of wildlife species. The second type is second-growth forest—a stand of trees resulting from secondary ecological succession (see Figure 4-6, p. 76). These forests develop after the trees in an area have been removed by human activities, such as clear-cutting for timber or for conversion to cropland, or by natural forces such as fire, hurricanes, or volcanic eruptions. A tree plantation, also called a tree farm or commercial forest, (Figure 6-1) is a managed forest containing only one or two species of trees that are all of the same age. They are usually harvested by clearcutting as soon as they become commercially valuable.
Weak trees removed
25 yrs
The land is then replanted and clear-cut again in a regular cycle. When managed carefully, such plantations can produce wood at a fast rate and thus could supply most of the wood used for industrial purposes such as papermaking. This would help to protect the world’s remaining old-growth and secondary forests. According to 2007 estimates by the UN Food and Agriculture Organization (FAO), about 36% of the world’s forests are old-growth forests, 60% are secondgrowth forests, and 4% are tree plantations (6% in the United States).
Forests Provide Important Economic and Ecological Services Forests provide highly valuable ecological and economic services (Figure 6-2). For example, through photosynthesis, forests remove CO2 from the atmosphere and store it in organic compounds (biomass). By performing this ecological service as a part of the global carbon
Natural Capital Forests Ec ol og i c al Ser vi c es
Ec onom ic Se rv ic e s
Support energy flow and chemical cycling
Fuelwood
Reduce soil erosion
Lumber
Absorb and release water
Pulp to make paper
Purify water and air
Mining
Influence local and regional climate
Livestock grazing
Store atmospheric carbon
Recreation
Provide numerous wildlife habitats
Jobs
Clear cut
30 yrs 15 yrs
Years of growth
Seedlings planted
5 yrs
10 yrs
Figure 6-1 Trees are grown in commercial forests using a 25- to 30-year rotation cycle of cutting and regrowth. In tropical countries, where trees can grow more rapidly year-round, the rotation cycle can be 6–10 years. Most tree plantations are grown on land that was cleared of old-growth or second-growth forests. Question: What are two ways in which this process can degrade an ecosystem?
Figure 6-2 Forests provide many important ecological and economic services. Questions: Which two ecological services and which two economic services do you think are the most important? Why?
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cycle (see Figure 2-20, p. 42), forests help to stabilize average atmospheric temperatures and slow projected climate change. Scientists have attempted to estimate the economic value of the ecological services provided by the world’s forests and other ecosystems. For example, in 1997, a team of ecologists, economists, and geographers, led by ecological economist Robert Costanza of the University of Vermont, estimated the monetary worth of the earth’s ecological services and the biological income from them to be close to the economic value of all of the goods and services produced annually throughout the world. They also calculated that the world’s forests provide us with ecological services worth at least $4.7 trillion per year—hundreds of times more then their economic value. The work of these researchers alerts us to three important facts: the earth’s ecosystem services are essential for all humans and their economies; their economic value is huge; and they are an ongoing source of ecological income as long as we use them sustainably.
Almost Half of the World’s Forests Have Been Cut Down
Unsustainable Logging Is a Major Threat to Forest Ecosystems Along with highly valuable ecological services, forests provide us with raw materials, especially wood, and harvesting wood is a major industry. The first step in harvesting trees is to build roads for access and timber removal. Even carefully designed logging roads have a number of harmful effects (Figure 6-3)—namely, increased erosion and sediment runoff into waterways, habitat fragmentation, and loss of biodiversity. Logging roads also expose forests to invasion by nonnative pests, diseases, and wildlife species. They also open once-inaccessible forests to miners, ranchers, farmers, hunters, and off-road vehicles. Once loggers reach a forest area, they use a variety of methods to harvest the trees (Figure 6-4). With selective cutting, intermediate-aged or mature trees in a forest are cut singly or in small groups (Figure 6-4a). However, loggers often remove all the trees from an area in what is called a clear-cut (Figure 6-4b). Clear-cutting is
New highway
the most efficient way for a logging operation to harvest trees, but it can do considerable harm to an ecosystem. For example, clear-cutting destroys and fragments wildlife habitat, thus reducing biodiversity (Concept 6-1). It also increases soil erosion and interferes with nutrient cycling. A variation of clear-cutting that allows a more GOOD sustainable timber yield without widespread NEWS destruction is strip cutting (Figure 6-4c). It involves clearcutting a strip of trees along the contour of the land within a corridor narrow enough to allow natural forest regeneration within a few years. After regeneration, loggers cut another strip next to the first, and so on. Biodiversity experts are alarmed at the growing practice of illegal, uncontrolled, and unsustainable logging taking place in 70 countries, especially in Africa and Southeast Asia. It has ravaged 37 of the 41 national parks in the African country of Kenya and now makes up 73–80% of all logging in Indonesia.
Deforestation is the temporary or permanent removal of large expanses of forest for agriculture, settlements, or other uses. Surveys by the World Resources Institute (WRI) indicate that over the past 8,000 years, human activities have reduced the earth’s original forest cover by about 46%, with most of this loss occurring since 1950. Surveys done by the FAO and the WRI indicate that the global rate of forest cover loss between 1990 and 2005 was between 0.2% and 0.5% per year, and that at least another 0.1–0.3% of the world’s forests were degraded every year, mostly to grow crops and graze cattle. If these estimates are correct, the world’s forests are being cleared or degraded at a rate of 0.3–0.8% per year, with much higher rates in some areas. These losses are concentrated in less-developed countries, especially those in the tropical areas of Latin America, Indonesia, and Africa. However, scientists are also concerned about the increased clearing of the northern boreal forests of Alaska, Canada, Scandinavia,
Cleared plots for grazing
Highway
Cleared plots for agriculture Old growth
Figure 6-3 Natural capital degradation: Building roads into previously inaccessible forests is the first step to harvesting timber, but it also paves the way to fragmentation, destruction, and degradation of forest ecosystems.
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CHAPTER 6
Sustaining Biodiversity: The Ecosystem Approach
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(a) Selective cutting
Natural Capital Degradation Deforestation Decreased soil fertility from erosion Runoff of eroded soil into aquatic systems Premature extinction of species with specialized niches Clear stream
Loss of habitat for native species and migratory species such as birds and butterflies Regional climate change from extensive clearing Release of CO2 into atmosphere
(b) Clear-cutting
Acceleration of flooding
Figure 6-5 Deforestation has some harmful environmental effects that can reduce biodiversity and degrade the ecological services provided by forests (Figure 6-2, left). Question: What are three products you have used recently that might have come from oldgrowth forests?
Muddy stream
(c) Strip cutting
Uncut
Cut 1 year ago Dirt road Cut 3–10 years ago Uncut
Clear stream
Figure 6-4 This diagram illustrates the three major tree harvesting methods. Question: If you were cutting trees in a forest you owned, which method would you choose and why?
and Russia, which together make up about one-fourth of the world’s forested area. According to the WRI, if current deforestation rates continue, about 40% of the world’s remaining intact forests will have been logged or converted to other uses within two decades. Clearing large areas of forests, especially old-growth forests, has important short-term economic benefits (Figure 6-2, right), but it also has a number of harmful environmental effects (Figure 6-5).
In some countries, there is encouraging news GOOD about forest use. In 2007, the FAO reported that NEWS the net total forest cover in several countries, including the United States (see the Case Study that follows), changed very little or even increased between 2000 and 2007. Some of the increases resulted from natural reforestation by secondary ecological succession on cleared forest areas and abandoned croplands. Other increases in forest cover were due to the spread of commercial tree plantations. ■ C AS E S T UDY
Many Cleared Forests in the United States Have Grown Back Forests cover about 30% of the U.S. land area, providing habitats for more than 80% of the country’s wildlife species and protecting the watersheds that supply about two-thirds of the nation’s surface water. Old-growth forests once covered more than half of the nation’s land area. But between 1620, when European settlements were expanding, and 1920, the old-growth forests of the eastern United States were decimated. Today, forests in the United States (including tree plantations) cover more area than they did in 1920. The primary reason is that many of the old-growth forests that were completely or partially cleared between 1620 and 1920 have grown back naturally through secondary ecological succession. There are now fairly diverse GOOD second-growth (and in some cases third-growth) NEWS forests in every region of the United States except much of the West. CONCEPT 6-1
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Every year, more wood is grown in the United States than is cut and the total area planted with trees increases. Protected forests make up about 40% of the country’s total forest area, mostly in the National Forest System, which consists of 155 national forests managed by the U.S. Forest Service (USFS). On the other hand, since the mid-1960s, an increasing area of the nation’s remaining old-growth and fairly diverse second-growth forests has been cut down and replaced with biologically simplified tree plantations. According to biodiversity researchers, this reduces overall forest biodiversity and disrupts ecosystem processes such as energy flow and chemical cycling—in violation of all three principles of sustainability. Many biodiversity researchers favor establishing tree plantations only on land that has already been degraded. HOW WOULD YOU VOTE?
✓ ■
Should there be a global effort to sharply reduce the cutting of old-growth forests? Cast your vote online at www.cengage .com/login.
Tropical Forests Are Disappearing Rapidly Tropical forests cover about 6% of the earth’s land area—roughly the area of the continental United States. Climatic and biological data suggest that mature tropical forests once covered at least twice as much area as they do today. Most of this loss of tropical forest has taken place since 1950. Satellite scans and ground-level surveys indicate that large areas of tropical rain forests and tropical dry forests are being cut rapidly in parts of Africa, Southeast Asia, and South America, especially Brazil. Studies indicate that at least half of the world’s known species of terrestrial plants, animals, and insects live in tropical forests. Because of their specialized niches, these species are highly vulnerable to extinction when their forest habitats are destroyed or degraded. Tropical deforestation is the main reason that more than 8,000 known tree species—10% of the world’s total— are threatened with extinction. Brazil has more than 30% of the world’s remaining tropical rain forest in its vast Amazon basin, which is larger than the area of India. According to Brazil’s government and forest experts, the percentage of its Amazon basin that was deforested or degraded increased from 1% in 1970 to about 20% by 2008. About onefifth of the old-growth Amazon rain forest has been lost since 1970—an area about equal to that of the U.S. state of California. In 2009, researcher Joe Wright of the Smithsonian Tropical Research Institute reported that in some cleared areas, forests are growing back as farmers abandon their land and move to cities in hopes of improv-
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ing their lives. However, one of Wright’s colleagues at the Smithsonian, biologist William Laurence, points out that these second-growth tropical forests do not have the biological diversity of uninterrupted expanses of old-growth tropical forests.
The Causes of Tropical Deforestation Are Varied and Complex Tropical deforestation results from a number of underlying and direct causes (Figure 6-6). Underlying causes such as pressures from population growth and poverty push subsistence farmers and the landless poor into tropical forests, where they try to grow enough food to survive. Government subsidies, or payments to help companies stay in business, can enhance the direct causes of deforestation by, for example, reducing the costs of timber harvesting, cattle grazing, and plantation farming. The degradation of a tropical forest usually begins when a road is cut deep into the forest interior for logging and settlement (Figure 6-3). Loggers then use selective cutting (Figure 6-4a) to remove the largest and best trees. When these big trees fall, many other trees fall with them because of their shallow roots and the network of vines connecting the trees in the forest’s canopy. This method causes considerable ecological damage in tropical forests, but much less than that from burning or clear-cutting forests. Burning is widely used to clear forest areas for agriculture, settlement, and other purposes. Healthy rain forests do not burn naturally. But roads, settlements, and farming, grazing, and logging operations fragment them. The resulting patches of forest dry out and readily ignite. According to a 2005 study by forest scientists, widespread fires in the Amazon basin are changing weather patterns by raising temperatures and reducing rainfall. The resulting droughts dry out the forests and make them more likely to burn. This process is converting large deforested areas of tropical forests to tropical grassland, or savanna. Models project that if current burning and deforestation rates continue, 20–30% of the Amazon basin will be turned into savanna in the next 50 years, and most of it could become savanna by 2080. Foreign corporations operating under government concession contracts do much of the logging in tropical countries. Once a country’s forests are gone, the companies move on to another country, leaving ecological devastation behind. For example, the Philippines and Nigeria have lost most of their once-abundant tropical hardwood forests. Several other tropical countries are following this path. After the best timber has been removed, timber companies or the local government often sell the land to ranchers who burn the remaining timber to clear the land for cattle grazing. Within a few years, their cattle typically overgraze the land and the ranchers move their operations to another forest area. Then they sell the degraded land to farmers who plow it up for large
Sustaining Biodiversity: The Ecosystem Approach
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Natural Capital Degradation Major Causes of the Destruction and Degradation of Tropical Forests Underlying Causes
Direct Causes
•
Not valuing ecological services
•
Roads
•
Cattle ranching
•
Crop and timber exports
•
Fires
•
Logging
• Government policies
•
Settler farming
•
Tree plantations
• Poverty
•
Cash crops
• Population growth Cattle ranching
Tree plantations
Figure 6-6 This diagram illustrates the major underlying and direct causes of the destruction and degradation of tropical forests. Question: If we could eliminate the underlying causes, which if any of the direct causes might automatically be eliminated?
Logging
Cash crops Settler farming
Fires Roads
plantations of crops such as soybeans, or to settlers who have migrated to tropical forests hoping to grow enough food on a small plot of land to survive. In tropical rain forests, plant nutrients are stored mostly in the quickly decomposed vegetation instead of
6-2
in the soil. Thus, after a few years of crop growing and erosion from rain, the nutrient-poor soil is completely depleted of nutrients. The farmers and settlers then move on to newly cleared land to repeat this environmentally destructive process.
How Should We Manage and Sustain Forests?
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We can sustain forests by emphasizing the economic value of their ecological services, removing government subsidies that hasten their destruction, protecting old-growth forests, harvesting trees no faster than they are replenished, and planting trees.
CONC EPT 6-2
We Can Manage Forests More Sustainably Biodiversity researchers and a growing number of foresters have called for more sustainable forest management. Figure 6-7 (p. 116) lists ways to achieve GOOD NEWS this goal (Concept 6-2).
Generally, conservation biologists argue, it is important to include estimated economic values of ecological services in all forest-use decisions. If we did this, most of the world’s old-growth and second-growth forests would not be cut because the monetary value of their ecological services far outweighs the monetary value of their short-term economic services. The ecological CONCEPT 6-2
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Solutions More Sustainable Forestry Identify and protect forest areas high in biodiversity Rely more on selective cutting and strip cutting Stop clear-cutting on steep slopes Stop logging in old-growth forests Sharply reduce road building in uncut forest areas Leave most standing dead trees and fallen timber for wildlife habitat and nutrient cycling Put tree plantations only on deforested and degraded land Certify timber grown by sustainable methods Include ecological services of forests in estimates of their economic value
ing, overuse of junk mail, inadequate paper recycling, and failure to reuse wooden shipping containers. Another cause of deforestation is the cutting of trees for fuelwood, especially in less-developed countries. One way to deal with this is to establish small plantations of fast-growing fuelwood trees and shrubs around farms and in community woodlots. Another is to provide villagers with cheap, efficient wood stoves or solar ovens, to reduce the need to cut trees for fuel. One reason for cutting trees is to provide pulp for making paper, but paper can be made out of fiber that does not come from trees. China uses rice straw and other agricultural residues to make much of its paper. Most of the small amount of tree-free paper produced in the United States is made from the fibers of a rapidly growing woody annual plant called kenaf (“kuh-NAHF”). Kenaf and other non-tree fibers such as hemp yield more paper pulp per hectare than tree farms do, and they require fewer pesticides and herbicides. It is estimated that within two to three decades, we could essentially eliminate the need to use trees to make paper.
Figure 6-7 There are a number of ways to grow and harvest trees more sustainably (Concept 6-2). Questions: Which three of these methods do you think are the most important? Why?
services of old-growth and most second-growth forests could be sustained indefinitely by selectively harvesting trees no faster than they are replenished and by using these forests primarily for recreation and as centers of biodiversity. Biologists also argue for protecting enough forest so that the rate of forest loss and degradation by human and natural factors in a particular area is balanced by the rate of forest renewal. This is especially important in forest areas that are centers of biodiversity, threatened by economic development. One increasingly popular practice that can help people to use forest products more sustainably is certification of sustainably grown timber and of sustainably produced forest products. In order to be certified, a timber company must use selective cutting and other environmentally friendly harvesting methods for a certain period of time. The goal is to keep from harming forest ecosystems and biodiversity while still making a profit on raising and harvesting timber. The same standards are applied to companies that make wood products, which are then certified when the standards have been met. Consumers can look for the stamp of certification when shopping for such products. Another very important way to reduce the pressure on forest ecosystems is to improve the efficiency of wood use. According to the Worldwatch Institute and some forestry analysts, up to 60% of the wood consumed in the United States is wasted unnecessarily. This results from inefficient use of construction materials, excess packag-
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Governments and Individuals Can Act to Reduce Tropical Deforestation Analysts have suggested various ways to protect tropical forests and use them more sustainably (Concept 6-2). One way is to help new settlers in tropical forests learn how to practice small-scale sustainable agriculture and forestry. Another is to harvest some of the renewable resources such as fruits and nuts in rain forests on a sustainable basis. In addition, strip-cutting (Figure 6-4c) could be used to harvest tropical trees for lumber. At the international level, debt-for-nature swaps can make it financially attractive for countries to protect their tropical forests. In such swaps, participating countries act as custodians of protected forest reserves in return for providing foreign aid or debt relief. In a similar strategy called conservation concessions, governments or private conservation organizations pay nations for agreeing to preserve their natural resources. Some groups are highly creative in using this GOOD solution. For example, conservation organizations NEWS working in a state park in Brazil’s endangered Atlantic Forest provided technical assistance to dairy farmers. In return, the farmers agreed to reforest and maintain part of this land in a conservation easement, which now serves as a buffer zone for the park. With this deal, the farmers were able to triple their milk yields and double their incomes. Loggers can use gentler methods for harvesting trees. For example, cutting canopy vines (lianas) before felling a tree and using the least obstructed paths to remove the logs can sharply reduce damage to neighboring trees.
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I ND I VI D UALS M ATTE R Wangari Maathai and the Green Belt Movement
I
n the mid-1970s, Wangari Maathai took a hard look at environmental conditions in her native African country of Kenya. Tree-lined streams she had known as a child had dried up. Farms and plantations had displaced vast areas of forest and were draining the watersheds and degrading the soil. Clean drinking water, firewood, and nutritious foods were all in short supply. Something inside her told Maathai that she had to do something about this environmental degradation. Starting with a small tree nursery in her backyard in 1977, she founded the Green Belt Movement, which continues today. The main goal of this highly regarded women’s self-help group is to organize poor women in rural Kenya to plant and protect millions of trees in order to combat deforestation and provide fuelwood. Since 1977, the 50,000 members of this grassroots group have established 6,000 village nurseries
and planted and protected more than 40 million trees. The women are paid a small amount for each seedling they plant that survives. This gives them an income to help them break out of the cycle of poverty. The trees provide fruits, building materials, and fodder for livestock. They also provide more fuelwood, so that women and children do not have to walk so far to find fuel for cooking and heating. The trees also improve the environment by reducing soil erosion and providing shade and beauty. The success of the Green GOOD NEWS Belt Movement has sparked the creation of similar programs in more than 30 other African countries. Wangari Maathai was the first Kenyan woman to earn a PhD and to head an academic department at the University of Nairobi. For her work in protecting the environment and in promoting democracy and
human rights, she has received many honors, including the Goldman Environmental Prize, the UN Africa Prize for Leadership, and induction into the International Women’s Hall of Fame. After years of being harassed, beaten, and jailed for opposing government policies, she was elected to Kenya’s parliament as a member of the Green Party in 2002. In 2004, Maathai became the first African woman and the first environmentalist to be awarded the Nobel Peace Prize for her lifelong efforts. Within an hour of learning that she had won the prize, Maathai planted a tree, telling onlookers it was “the best way to celebrate.” In her speech accepting the award she urged everyone in the world to plant a tree as a symbol of commitment and hope. Maathai tells her story in her book, The Green Belt Movement: Sharing the Approach and the Experience, published by Lantern Books in 2003.
to plant 7 billion trees worldwide. The goal of the campaign is to plant trees that are well-adapted to each local setting, be it a farm, a degraded natural forest, or an urban environment. By mid-2009, thousands of people in 166 countries had planted more than 7.4 billion trees. Finally, each of us as consumers can reduce the demand for products that encourage illegal and unsustainable logging in tropical forests. For building projects, we can use recycled waste lumber. We can also use substitutes Forests for wood such as recycled plastic building materials and sustainably grown bamboo, R es t or at i on which can grow up to 0.9 meters (3 feet) in Encourage regrowth a single day. These and other ways to prothrough secondary tect tropical forests are summarized in (Figsuccession ure 6-8).
Governments and individuals can mount efforts to reforest and rehabilitate degraded tropical forests and watersheds (see Individuals Matter, above) and clamp down on illegal logging. In 2007, the UN Environment Programme (UNEP) announced a Billion Tree Campaign
Solutions Sustaining Tropical P r eventi o n Protect the most diverse and endangered areas Educate settlers about sustainable agriculture and forestry Subsidize only sustainable forest use Protect forests through debt-for-nature swaps and conservation concessions
Rehabilitate degraded areas
Certify sustainably grown timber Reduce poverty Slow population growth
Concentrate farming and ranching in already-cleared areas
Figure 6-8 These are some effective ways to protect tropical forests and use them more sustainably (Concept 6-2). Questions: Which three of these solutions do you think are the most important? Why?
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6-3
How Should We Manage and Sustain Parks and Nature Reserves?
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Sustaining biodiversity will require more effective protection of existing parks and nature reserves, as well as the protection of much more of the earth’s remaining undisturbed land area.
C O NC EPT 6-3
National Parks Face Many Environmental Threats Today, more than 1,100 major national parks are located in more than 120 countries. Parks in lessdeveloped countries have the greatest biodiversity of all parks globally, but only about 1% of these parklands are protected. In many countries, local people enter the parks illegally in search of wood, cropland, game animals, and other natural products that they need for their daily survival. Loggers and miners operate illegally in many of these parks, as do wildlife poachers who kill animals to obtain and sell items such as rhinoceros horns, elephant tusks, and furs. Park services in most of the lessdeveloped countries have too little money and too few personnel to fight these invasions, either by force or through education. Another problem is that most national parks are too small to sustain many large animal species. And many parks suffer from invasions by nonnative species that compete with and reduce the populations of native species, and disrupt these ecosystems. ■ CAS E STUDY
Stresses on U.S. Public Parks The U.S. national park system, established in 1912, includes 58 major national parks, sometimes called the country’s crown jewels, along with 333 monuments and historic sites. States, counties, and cities also operate public parks. Popularity is one of the biggest problems for many parks. Between 1960 and 2008, the number of visitors to U.S. national parks more than tripled, reaching 273 million yearly. Most state parks are located near urban areas and receive about twice as many visitors per year as do the national parks. During the summer, visitors entering the most popular parks often face long backups and experience noise, congestion, and eroded trails. In some parks and other public lands, noisy and polluting dirt bikes, dune buggies, jet skis, snowmobiles, and off-road vehicles degrade the aesthetic experience for many visitors, destroy or damage fragile vegetation, and disturb wildlife. There is controversy over whether these machines should be allowed in national parks and proposed wilderness areas within the parks.
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A number of parks also suffer damage from the migration or deliberate introduction of nonnative species. European wild boars, imported for hunting into the U.S. state of North Carolina in 1912, threaten vegetation in parts of the Great Smoky Mountains National Park. Nonnative mountain goats in Washington State’s Olympic National Park trample and destroy the root systems of native vegetation and accelerate soil erosion. At the same time, native species—some of them threatened or endangered—are killed in, or illegally removed from, almost half of U.S. national parks. Predators such as wolves all but vanished from various parks mostly because of excessive hunting and poisoning by ranchers and federal officials. In some parks, populations of the species that wolves once controlled have exploded, destroying vegetation and crowding out other species. To help correct this situation, the U.S. Fish and Wildlife Service established a controversial program to reintroduce the gray wolf into the Yellowstone National Park area (Science Focus, at right). Many U.S. national parks have become threatened islands of biodiversity surrounded by a sea of commercial development. Nearby human activities that threaten wildlife and recreational values in many national parks include mining, logging, livestock grazing, the use of coal-fired power plants, water diversion, and urban development. Polluted air, drifting hundreds of kilometers from cities, kills ancient trees in California’s Sequoia National Park and often degrades the awesome views at Arizona’s Grand Canyon National Park. According to the National Park Service, air pollution, mostly from coalfired power plants and dense vehicle traffic, degrades scenic views in U.S. national parks more than 90% of the time. Figure 6-9 lists ten suggestions made by various analysts for sustaining and expanding the national park system in the United States.
Nature Reserves Occupy Only a Small Part of the Earth’s Land Most ecologists and conservation biologists believe the best way to preserve biodiversity is to create a worldwide network of protected areas. Currently, only 12% of the earth’s land area is protected either strictly or partially in nature reserves, parks, wildlife refuges, wilderness, and other areas. This 12% figure is misleading because no more than 5% of the earth’s land is strictly
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S C I E NC E FO C U S Reintroducing the Gray Wolf to Yellowstone National Park
A
round 1800, at least 350,000 gray wolves roamed over about three-quarters of America’s lower 48 states, especially in the West. They survived mostly by preying on abundant bison, elk, caribou, and deer. But between 1850 and 1900, most of them were shot, trapped, or poisoned by ranchers, hunters, and government employees. When Congress passed the U.S. Endangered Species Act (see Chapter 5, p. 106) in 1973, only a few hundred gray wolves remained outside of Alaska, primarily in Minnesota and Michigan. In 1974, the gray wolf was listed as an endangered species in the lower 48 states. Ecologists recognize the important role that this keystone predator species once played in parts of the West and the Great Plains. The wolves culled herds of bison, elk, moose, and mule deer, and kept down coyote populations. By leaving some of their kills partially uneaten, they provided meat for scavengers such as ravens, bald eagles, ermines, grizzly bears, and foxes. When wolves declined, herds of elk, moose, and mule deer expanded and devastated vegetation such as willow and aspen trees often found growing near streams and
rivers. This led to increased soil erosion and threatened habitats of other wildlife species and the food supplies of beaver, which eat willow and aspen. This in turn affected species that depend on wetlands created by the beavers. In 1987, the U.S. Fish and Wildlife Service (USFWS) proposed reintroducing gray wolves into the Yellowstone National Park ecosystem. The proposal brought angry protests, some from area ranchers who feared the wolves would leave the park and attack their cattle and sheep. Other objections came from hunters who feared the wolves would kill too many big-game animals, and from mining and logging companies that feared the government would halt their operations on wolf-populated federal lands. In 1995 and 1996, federal wildlife officials caught gray wolves in Canada and relocated 31 of them to Yellowstone National Park. Scientists estimate that the long-term carrying capacity of the park is 110 to 150 gray wolves. By the end of 2009, the park had 116 gray wolves. With wolves around, elk are gathering less near streams and rivers, which has allowed the regrowth of aspen, cottonwoods, and
Solutions National Parks Integrate plans for managing parks and nearby federal lands Add new parkland near threatened parks Buy private land inside parks Locate visitor parking outside parks and provide shuttle buses for people touring heavily used parks Increase federal funds for park maintenance and repairs Raise entry fees for visitors and use resulting funds for park management and maintenance Seek private donations for park maintenance and repairs Limit the number of visitors in crowded park areas Increase the number of park rangers and their pay Encourage volunteers to give visitor lectures and tours
Figure 6-9 These are ten suggestions for sustaining and expanding the national park system in the United States. Questions: Which two of these proposals do you think are the most important? Why? (Data from Wilderness Society and National Parks and Conservation Association)
willow trees there. This in turn helped to stabilize stream banks, which lowered the water temperature and made better habitat for trout. Beavers seeking willow and aspen have returned. In addition, leftovers of elk killed by wolves are an important food source for grizzly bears and other scavengers such as bald eagles and ravens. The wolves have also cut in half the population of coyotes—the top predators in the absence of wolves. This has reduced coyote attacks on cattle from surrounding ranches and has increased populations of smaller animals such as ground squirrels, mice, and gophers that are hunted by coyotes, eagles, and hawks. Overall, this experiment in ecosystem restoration has helped to re-establish and sustain some of the biodiversity that the Yellowstone ecosystem once had. Critical Thinking How has the improved health of the Yellowstone ecosystem helped nearby ranchers and other opponents of the wolf reintroduction program?
protected from potentially harmful human activities. In other words, we have reserved 95% of the earth’s land for human use. Conservation biologists call for full protection of at least 20% of the earth’s land area in a global system of biodiversity reserves that would include multiple examples of all the earth’s biomes (Concept 6-3). But powerful economic and political interests oppose this idea. Protecting more of the earth’s land from unsustainable use will require action and funding by national governments and private groups, bottom-up political pressure by concerned individuals, and cooperative ventures involving governments, businesses, and private conservation organizations. Private groups play an important role in establishing wildlife refuges and other reserves to protect biological diversity. For example, since its founding GOOD by a group of professional ecologists in 1951, The NEWS Nature Conservancy—with more than 1 million members worldwide—has created the world’s largest system of privately held nature reserves and wildlife sanctuaries in 30 countries. In the United States, private, nonprofit land trust groups have protected large areas of land. Members pool their financial resources and accept tax-deductible CONCEPT 6-3
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donations to buy and protect farmlands, woodlands, wetlands, and urban green spaces. Some governments are also making progress. By 2007, the Brazilian government had officially protected 23% of the Amazon—an area the size of France—from development. But many of these areas are protected only on paper and are not always secure from illegal resource removal and degradation. Most developers and resource extractors oppose protecting even the current 12% of the earth’s remaining undisturbed ecosystems. They contend that these areas might contain valuable resources that would add to current economic growth. Ecologists and conservation biologists disagree. They view protected areas as islands of biodiversity and natural capital that help to sustain all life and economies and serve as centers of future evolution. (See Norman Myer’s Guest Essay on this topic at CengageNOW.) HOW WOULD YOU VOTE?
✓ ■
Should at least 20% of the earth’s land area be strictly protected from economic development? Cast your vote online at www.cengage.com/login.
Whenever possible, conservation biologists call for using the buffer zone concept to design and manage nature reserves (Figure 6-10). This means strictly protecting an
inner core of a reserve, usually by establishing two buffer zones in which local people can extract resources sustainably without harming the inner core. Instead of shutting people out of the protected areas and likely creating enemies, this approach enlists local people as partners in protecting a reserve from unsustainable uses such as illegal logging and poaching. By 2009, the GOOD NEWS United Nations had used this strategy to create a global network of 553 biosphere reserves in 107 countries. ■ C AS E S T UDY
Costa Rica—A Global Conservation Leader Tropical forests once completely covered Central America’s Costa Rica, which is smaller in area than the U.S. state of West Virginia and about one-tenth the size of France. Between 1963 and 1983, politically powerful ranching families cleared much of the country’s forests to graze cattle. Despite such widespread forest loss, tiny Costa Rica is a superpower of biodiversity, with an estimated 500,000 plant and animal species. A single park in Costa Rica is home to more bird species than are found in all of North America. In the mid-1970s, Costa Rica established a system of nature reserves and national parks that, by 2008,
Biosphere Reserve
Core area Research station Visitor education center Buffer zone 1 Human settlements
Buffer zone 2
Figure 6-10 Solutions: A model biosphere reserve is shown here. Each reserve contains a protected inner core surrounded by two buffer zones that local and indigenous people can use for sustainable logging, growing limited crops, grazing cattle, hunting, fishing, and eco-tourism. Questions: Do you think some of these reserves should be free of all human activity, including eco-tourism? Why or why not?
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Sustaining Biodiversity: The Ecosystem Approach
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Nicaragua
Caribbean Sea
Costa Rica
Panama
Pacific Ocean
Wilderness protection is not without controversy (see the Case Study that follows). Some critics oppose protecting large areas for their scenic and recreational value for a relatively small number of people. They believe this keeps some areas of the planet from being economically useful to people living today. But to most biologists, the most important reasons for protecting wilderness and other areas from exploitation and degradation involve long-term needs—to preserve biodiversity as a vital part of the earth’s natural capital and to protect wilderness areas as centers for evolution in response to mostly unpredictable changes in environmental conditions. In other words, protecting wilderness areas is equivalent to investing in a biodiversity insurance policy.
National parkland
■ C AS E S T UDY
Buffer zone
Controversy over Wilderness Protection in the United States
Figure 6-11 Solutions: Costa Rica has consolidated its parks and reserves into eight zoned megareserves designed to sustain about 80% of the country’s rich biodiversity. Green areas are protected natural parklands and yellow areas are nearby buffer zones, which can be used for sustainable forms of forestry, agriculture, hydropower, hunting, and other human activities.
included about a quarter of its land—6% of it reserved for indigenous peoples. Costa Rica now devotes a larger proportion of its land to biodiversity conservation than does any other country. The country’s parks and reserves are consolidated into eight zoned megareserves (Figure 6-11). Each reserve contains a protected inner core surrounded by two buffer zones that local and indigenous people can use for sustainable logging, crop farming, cattle grazing, hunting, fishing, and ecotourism. Costa Rica’s biodiversity conservation strategy has paid off. Today, the country’s largest source of income is its $1-billion-a-year tourism industry, almost two-thirds of which involves ecotourism. To reduce deforestation, the government has eliminated subsidies for converting forest to rangeland. It also pays landowners to maintain or restore tree cover. The strategy has worked: Costa Rica has gone from having one of the world’s highest deforestation rates to having one of the lowest.
Protecting Wilderness Is an Important Way to Preserve Biodiversity One way to protect undeveloped lands from human exploitation is to set them aside as wilderness—land officially designated as an area where natural communities have not been seriously disturbed by humans and where human activities are limited by law.
Conservationists in the United States have been trying to save wild areas from development since 1900. Overall, they have fought a losing battle. Not until 1964 did Congress pass the Wilderness Act. It allowed the government to protect undeveloped tracts of public land from development as part of the National Wilderness Preservation System. The area of protected wilderness in the GOOD United States increased tenfold between 1970 NEWS and 2010. Even so, only about 4.7% of U.S. land is protected as wilderness—almost three-fourths of it in Alaska. Only about 2% of the land area of the lower 48 states is protected, most of it in the West. However, in 2009 the U.S. government granted wilderness protection to more than 800,000 hectares (2 million acres) of public land in 9 of the lower 48 states. It was the largest expansion of wilderness lands in 15 years. The new law also increased the total length of wild and scenic rivers (treated as wilderness areas) by 50%—the largest such increase ever. One problem is that only 4 of the 413 wilderness areas in the lower 48 states are large enough to sustain all of the species they contain. Some species, such as wolves, need large areas in which to roam as packs, to find prey, and to mate and rear young. Also, the system includes only 81 of the country’s 233 distinct ecosystems. Scattered blocks of public lands with a total area roughly equal to that of the U.S. state of Montana could qualify for designation as wilderness. About 60% of such land is in the national forests. But for decades the politically powerful oil, gas, mining, and timber industries have sought entry to these areas—owned jointly by all citizens of the United States—in hopes of locating and removing valuable resources. Under the law, as soon as such an area is accessed in this way, it automatically becomes disqualified for wilderness protection.
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6-4
What Is the Ecosystem Approach to Sustaining Terrestrial Biodiversity?
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C O NC EPT 6-4 We can help to sustain terrestrial biodiversity by identifying and protecting severely threatened areas (biodiversity hotspots), restoring damaged ecosystems, and sharing as much of the earth’s land as possible with other species.
We Can Use a Four-Point Strategy to Protect Ecosystems Most biologists and wildlife conservationists believe that we must focus more on protecting and sustaining ecosystems, and the biodiversity contained within them, than on saving individual species. Their goals certainly include preventing the hastening of extinction of species by human activities, but they argue the best way to do that is to protect threatened habitats and ecosystem services. This ecosystems approach would generally employ the following four-point plan: 1. Map the world’s terrestrial ecosystems and inventory the species contained in each of them. 2. Locate and protect the most endangered ecosystems and species.
Figure 6-12 shows 34 terrestrial biodiversity hotspots. In these areas, a total of 86% of the habitat has been destroyed. Although these hotspots cover only a little more than 2% of the earth’s land surface, they contain an estimated 50% of the world’s flowering plant species and 42% of all terrestrial vertebrates (mammals, birds, reptiles, and amphibians). They are also home for a large majority of the world’s endangered or critically endangered species (Science Focus, at right). Says environmental scientist Norman Myers, “I can think of no other biodiversity initiative that could achieve so much at a comparatively small cost, as the hotspots strategy.” Identifying and protecting hotspots is very important. But conservation biologists warn that it will not be enough in the long run if we do not work to sustain much more of the world’s entire fabric of biodiversity.
3. Seek to restore as many degraded ecosystems as possible. 4. Make development biodiversity-friendly by providing significant financial incentives (such as tax breaks and write-offs) and technical help to private landowners who agree to help protect endangered ecosystems. Some scientists have argued that we need new laws to embody these principles. In the United States, for example, there is support for amending the Endangered Species Act, or possibly even replacing it, in order to implement an ecosystems or biodiversity protection act.
Protecting Global Biodiversity Hotspots Is an Urgent Priority The earth’s species are not evenly distributed. In fact, 17 megadiversity countries, most of them with large areas of tropical forest, contain more than two-thirds of all species. The leading megadiversity countries, in order, are Indonesia, Colombia, Mexico, Brazil, and Ecuador. To protect as much of the earth’s remaining biodiversity as possible, some biodiversity scientists urge the adoption of an emergency action strategy to identify and quickly protect biodiversity hotspots—areas especially rich in plant species that are found nowhere else and are in great danger of extinction (Concept 6-4). These areas suffer serious ecological disruption, mostly because of rapid human population growth and the resulting pressure on natural resources.
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We Can Rehabilitate and Restore Ecosystems That We Have Damaged Almost every natural place on the earth has been affected or degraded to some degree by human activities. We can at least partially reverse much of this harm through ecological restoration: the process of repairing damage caused by humans to the biodiversity and dynamics of natural ecosystems. Examples include replanting forests, restoring grasslands, restoring wetlands and stream banks, reintroducing native species, removing invasive species, and freeing river flows by removing dams. Evidence indicates that in order to sustain biodiversity, we must make a global effort to rehabilitate and restore ecosystems we have damaged (Concept 6-4). An important strategy is to mimic nature and natural processes and let nature do most of the work, usually through secondary ecological succession. By studying how natural ecosystems recover, scientists are learning how to speed up repair operations using a variety of approaches, including the following four measures: •
Restoration: returning a particular degraded habitat or ecosystem to a condition as similar as possible to its natural state.
•
Rehabilitation: turning a degraded ecosystem into a functional or useful ecosystem without trying to restore it to its original condition. Examples include
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Figure 6-12 Endangered natural capital: This map shows 34 biodiversity hotspots identified by ecologists as important and endangered centers of terrestrial biodiversity that contain a large number of species found nowhere else. Identifying and saving these critical habitats requires a vital emergency response (Concept 6-4). According to the IUCN, the average proportion of biodiversity hotspot areas truly protected with funding and enforcement is only 5%. Questions: Are any of these hotspots located near where you live? Is there a smaller, localized hotspot in the area where you live? (Data from Center for Applied Biodiversity Science at Conservation International)
removing pollutants and replanting to reduce soil erosion in abandoned mining sites and landfills, and in clear-cut forests. •
Replacement: replacing a degraded ecosystem with another type of ecosystem. For example, a degraded
forest could be replaced by a productive pasture or tree plantation. •
Creating artificial ecosystems: for example, creating artificial wetlands to help reduce flooding or to treat sewage.
S C I E NC E FO C U S A Biodiversity Hotspot in East Africa
T
he forests covering the flanks of the Eastern Arc Mountains of the African nation of Tanzania contain the highest concentration of endangered animals on earth. Plants and animals that exist nowhere else (species endemic to this area) live in these mountainside forests in considerable numbers. They include 96 species of vertebrates—10 mammal, 19 bird, 29 reptile, and 38 amphibian—43 species of butterflies, and at least 800 endemic species of plants, including most species of African violets. An international network of scientists, who had extensively surveyed these mountain forests, reported these findings in 2007. They also reported newly discovered species in
these forests, including a tree-dwelling monkey called the Kipunji and some surprisingly large reptiles and amphibians. This area is a major biodiversity hotspot because humans now threaten to do what the ice ages could not do—kill off its forests. Farmers and loggers have cleared 70% of the ancient forests. This loss of habitat, along with hunting, has killed off many species, including elephants and buffalo, and now 71 of the 96 endemic species are threatened, 8 of them critically, with biological extinction. These species are now forced to survive within 13 patches of forest that total an area about the size of the U. S. state of Rhode Island. Most of these forests are contained
within 150 Tanzanian government reserves. New settlements are not allowed, but people still forage in these reserves for fuelwood and building materials, severely degrading some of the forests. Fire is also a threat, because the shrinking, degraded patches of forest are drying out, and scientists warn that this situation is likely to get worse as atmospheric warming increases and climate change takes hold. Critical Thinking Do you think other countries should help Tanzania to protect its biodiversity hotspots and to expand protection? Explain.
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Researchers have suggested a science-based, fourstep strategy for carrying out most forms of ecological restoration and rehabilitation. 1. Identify the causes of the degradation (such as pollution, farming, overgrazing, mining, or invasive species). 2. Stop the abuse by eliminating or sharply reducing these factors. This would include removing toxic soil pollutants, improving depleted soil by adding nutrients and new topsoil, preventing fires, and controlling or eliminating disruptive nonnative species. 3. If necessary, reintroduce key species to help restore natural ecological processes, as was done with wolves in the Yellowstone ecosystem (Science Focus, p. 119). 4. Protect the area from further degradation and allow secondary ecological succession to occur. Some analysts worry that ecological restoration could encourage continuing environmental destruction and degradation by suggesting that any ecological harm we do can be undone. Restoration ecologists disagree with that suggestion. They point out that so far, we have been able to protect only about 5% of the earth’s land from the effects of human activities; thus, ecological restoration is badly needed for many of the world’s ecosystems. They argue that even if a restored ecosystem differs from the original system, the result is better than no restoration at all, and that more experience with ecological restoration will improve its effectiveness. HOW WOULD YOU VOTE?
✓ ■
Should we mount a massive effort to restore the ecosystems we have degraded, even though this will be quite costly? Cast your vote online at www.cengage.com/login.
We Can Share Areas We Dominate with Other Species Ecologist Michael L. Rosenzweig strongly supports proposals to help sustain the earth’s biodiversity through species protection strategies such as the U.S. Endangered Species Act (see Chapter 5, p. 106) and through preserving wilderness and other wildlife preserves. However, Rosenzweig contends that in the long run, these approaches will fail for two reasons. First, fully protected reserves currently are devoted to saving only about 5% of the world’s terrestrial area, excluding polar regions and some other uninhabitable areas. To Rosenzweig, the real challenge is to help sustain wild species in the human-dominated portion of nature that makes up 95% of the planet’s inhabitable terrestrial area. Second, setting aside funds and refuges, and passing laws to protect endangered and threatened species are essentially desperate attempts to save species that are in
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deep trouble. These emergency efforts can help a few species, but it is equally important to learn how to keep more species away from the brink of extinction. This is a prevention approach. Rosenzweig suggests that we develop a new form of conservation biology, called reconciliation ecology. This science focuses on inventing, establishing, and maintaining new habitats to conserve species diversity in places where people live, work, or play. In other words, we need to learn how to share with other species some of the spaces we dominate (Concept 6-4). Implementing reconciliation ecology will involve the growing practice of community-based conservation, in which conservation biologists work with people to help them protect biodiversity in their local communities. With this approach, scientists, citizens, and sometimes national and international conservation organizations seek ways to preserve local biodiversity while allowing people who live in or near protected areas to make sustainable use of some of the resources there (see the Case Study that follows). Some scientists have dealt with this challenge GOOD by getting people to realize that protecting local NEWS wildlife and ecosystems can provide economic resources for their communities by encouraging sustainable forms of ecotourism. In the Central American country of Belize, for example, conservation biologist Robert Horwich has helped to establish a local sanctuary for the black howler monkey. He convinced local farmers to set aside strips of forest to serve as habitats and corridors through which these monkeys can travel. The reserve, run by a local women’s cooperative, has attracted ecotourists and biologists. The community has built a black howler museum and local residents receive income by housing and guiding ecotourists and visiting biological researchers. There are many other examples of individuals and groups working together on projects to restore grasslands, wetlands, streams, and other degraded areas. Figure 6-13 lists some ways in which you can help to sustain the earth’s terrestrial biodiversity. ■ C AS E S T UDY
The Blackfoot Challenge— Reconciliation Ecology in Action The Blackfoot River watershed is home to hundreds of species of plants and animals, as well as people living in seven communities and 2,500 rural households. A book and movie, both entitled A River Runs Through It, tell of how residents of the valley cherish their lifestyles. In the 1970s, many of these people recognized that their beloved valley was threatened by poor mining, logging, and grazing practices, water and air pollution, and unsustainable commercial and residential development. They also understood that their way of life depended on wildlife and wild ecosystems located on private and public lands. They began meeting infor-
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What Can You Do? Sustaining Terrestrial Biodiversity ■
Adopt a forest
■
Plant trees and take care of them
■
Recycle paper and buy recycled paper products
■
Buy sustainably produced wood and wood products
■
Choose wood substitutes such as bamboo furniture and recycled plastic outdoor furniture, decking, and fencing
■
Help to restore a nearby degraded forest or grassland
■
Landscape your yard with a diversity of plants that are native to your area
Figure 6-13 Individuals matter: These are some ways in which you can help to sustain terrestrial biodiversity. Questions: Which two of these actions do you think are the most important? Why? Which of these things do you already do?
6-5
mally over kitchen tables to discuss how to maintain their way of life while sustaining the other species living in the valley. Out of these meetings came action. Teams of residents organized weed-pulling parties, built nesting structures for waterfowl, and developed more sustainable grazing systems. Landowners agreed to create perpetual conservation easements, setting land aside for only conservation and sustainable uses such as hunting and fishing. In 1993, these efforts were organized under a charter called the Blackfoot Challenge. The results were dramatic. Blackfoot Challenge members have restored and enhanced large areas of wetlands, streams, and native grasslands. They have preserved large areas of private land. The pioneers in this project might not have known it, but they were initiating what has become a classic example of reconciliation ecology. They worked together, respected each other’s views, accepted compromises, and found ways to share their land with the plants and animals that make the valley such a beautiful place to live.
How Can We Protect and Sustain Marine Biodiversity?
▲
We can help to sustain marine biodiversity by using laws and economic incentives to protect species, setting aside marine reserves to protect ecosystems, and using community-based integrated coastal management.
CONC EPT 6-5
We Have Much to Learn about Aquatic Biodiversity Although we live on a watery planet, we have explored only about 5% of the earth’s interconnected oceans and know relatively little about their biodiversity. However, scientists have observed three general patterns of marine biodiversity. First, the greatest marine biodiversity occurs in coral reefs, estuaries, and on the deep-ocean floor. Second, biodiversity is higher near coasts than in the open sea because of the greater variety of producers and habitats in coastal areas. Third, biodiversity is generally higher in the bottom region of the ocean than in the surface region because of the greater variety of habitats and food sources on the ocean bottom. The world’s marine systems provide important ecological and economic services (see Figure 3-8, p. 60). A very conservative estimate of the value of their ecological services is $21 trillion a year—about twice that of the world’s terrestrial ecosystems, including croplands. As with terrestrial biodiversity, the greatest threats to the biodiversity of the world’s marine ecosystems can
be remembered with the aid of the acronym HIPPCO, with H standing for habitat loss and degradation (see Figure 3-10, p. 62). Some 90% of fish living in the ocean spawn in coral reefs, coastal wetlands and marshes, coastal sea-grass beds, mangrove forests, or rivers. All of these ecosystems are under intense pressure from human activities. Scientists reported in 2006 that these coastal habitats are disappearing at rates 2–10 times higher than the rate of tropical forest loss. Many sea-bottom habitats are being destroyed by dredging operations and trawler fishing boats. Like giant submerged bulldozers, trawlers drag huge nets weighted down with heavy chains and steel plates over ocean bottoms, churning up sediments that smother some sea life, to harvest a few species of bottom fish and shellfish. Every year, thousands of trawlers scrape and disturb an area of ocean floor many times larger than the total global area of forests that are clear-cut annually. Coral reefs serve as habitat for many hundreds of marine species. They are threatened by shore development, pollution, and a growing acidity in ocean waters resulting from greatly increased levels of carbon dioxide emitted by human activities. Scientists of the Global CONCEPT 6-5
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Coral Reef Monitoring Network reported in 2008 that nearly one-fifth of the world’s reefs had been destroyed. Scientists have projected that increasing ocean temperatures and acidity could kill off most of the world’s remaining coral reefs by 2100. Another problem is the deliberate or accidental introduction of hundreds of harmful invasive species into coastal waters and wetlands. These bioinvaders can displace or cause the extinction of native species and disrupt ecosystem functions. Human population growth continually adds to the already intense pressure on the world’s coastal zones, primarily by destroying more aquatic habitat and increasing pollution. In addition, climate change threatens aquatic biodiversity by causing sea levels to rise, which will drown productive ecosystems such as mangrove swamps and other coastal ecosystems. Overfishing has become a major threat to biodiversity. According to a 2003 study led by Boris Worm, 90% or more of the large, predatory, open-ocean fishes such as tuna, swordfish, and marlin have disappeared since 1950. As such species are overfished, the fishing industry is shifting to smaller marine species such as herring, sardines, and squid. One researcher referred to this as “stealing the ocean’s food supply,” because these smaller species make up much of the diet of larger predator fish, seabirds, and toothed whales. According to the 2009 IUCN Red List of Threatened Species, 37% of the world’s marine species that were evaluated and 71% of the world’s freshwater fish species that were evaluated face extinction within the next 6 to 7 decades. Indeed, marine and freshwater fishes are threatened with extinction by human activities more than any other group of species.
There Are Ways to Protect and Sustain Marine Biodiversity Protecting marine biodiversity is difficult for several reasons. First, the human ecological footprint is expanding so rapidly that it is difficult to monitor its impacts on aquatic systems. Second, much of the damage to the oceans and other bodies of water is not visible to most people. Third, many people incorrectly view the seas as an inexhaustible resource that can absorb an almost infinite amount of waste and pollution. Fourth, most of the world’s ocean area lies outside the legal jurisdiction of any country. Thus, much of it is an open-access resource, subject to overexploitation. Nevertheless, there are several ways to protect and sustain marine biodiversity, one of which is the regulatory approach (Concept 6-5). National and international laws and treaties to help protect marine species include the U.S. Marine Mammal Protection Act of 1972, the U.S. Endangered Species Act of 1973, the U.S. Whale Conservation and Protection Act of 1976, and the 1995 International Convention on Biological Diversity.
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The U.S. Endangered Species Act (see Chapter 5, p. 106) and several international agreements have been used to identify and protect endangered and threatened marine species, including whales, seals, sea lions, and sea turtles. The problem is that with some international agreements, it is hard to get all nations to comply, which can weaken the effectiveness of such agreements. In 2004, for example, some 1,134 scientists signed a statement urging the United Nations to declare a moratorium on bottom trawling on the high seas by 2006 and to eliminate it globally by 2010. Fishing nations led by Iceland, Russia, China, and South Korea blocked such a ban. But in 2007, those countries (except for Iceland) and 18 others agreed to voluntary restrictions on bottom trawling in the South Pacific. Although GOOD monitoring and enforcement will be difficult, this NEWS agreement partially protects about one-quarter of the world’s ocean bottom from destructive trawling. Other ways to protect endangered and threatened aquatic species involve using economic incentives. For example, according to a 2004 World Wildlife Fund study, sea turtles are worth more to local communities alive than dead. The report estimates that sea turtle tourism brings in almost three times more money than the sale of turtle products such as meat, leather, and eggs brings in. Educating citizens about this issue has inspired some coastal communities to protect the turtles. Some countries are attempting to protect marine biodiversity and sustain fisheries by establishing marine sanctuaries. Since 1986, the IUCN has helped to establish a global system of marine protected areas (MPAs)— areas of ocean partially protected from human activities. There are more than 4,000 MPAs worldwide. Despite their name, most MPAs are only partially protected and dredging, trawler fishing, and other harmful activities are still allowed there. Marine reserves, on the other hand, are fully protected. These areas are declared off-limits to destructive human activities in order to enable their ecosystems to recover and flourish. Scientific studies show GOOD that within fully protected marine reserves, fish NEWS populations double, fish size grows by almost a third, fish reproduction triples, and species diversity increases by almost one-fourth. Furthermore, these improvements happen within 2–4 years after strict protection begins, and they last for decades. Use of these reserves is growing. One strategy emerging in some coastal communities is integrated coastal management—a community-based effort in which fishers, business owners, developers, scientists, citizens, and politicians identify shared problems and goals in their use of marine resources. The idea is to develop workable, cost-effective, and adaptable solutions that help to preserve biodiversity and environmental quality, while also meeting economic and social goals. This requires all participants to seek reasonable short-term trade-offs that can lead to long-term ecological and economic benefits. For example, fishers might
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Figure 6-14 There are a number of ways to manage fisheries more sustainably and protect marine biodiversity. Questions: Which four of these solutions do you think are the most important? Why?
Solutions Managing Fisheries Fishery Regulations Set low catch limits Improve monitoring and enforcement Economic Approaches Reduce or eliminate fishing subsidies Certify sustainable fisheries Protect Areas Establish no-fishing areas Establish more marine protected areas Consumer Information Label sustainably harvested fish Publicize overfished and threatened species
6-6
Bycatch Use nets that allow escape of smaller fish Use net escape devices for seabirds and sea turtles Aquaculture Restrict coastal locations of fish farms Improve pollution control Nonnative Invasions Kill or filter organisms from ship ballast water Dump ballast water at sea and replace with deep-sea water
have to give up harvesting marine species in certain areas until stocks recover enough to restore biodiversity in those areas. This might help provide fishers with a more sustainable future for their businesses. Figure 6-14 summarizes actions that individuals, organizations, and governments can take to manage global fisheries more sustainably and to protect marine biodiversity and ecosystem services.
How Should We Protect and Sustain Freshwater Biodiversity?
▲
CONC EPT 6-6 We can help to sustain freshwater biodiversity by protecting the watersheds of lakes and streams, preserving wetlands, and restoring degraded freshwater systems.
Freshwater Ecosystems Are under Major Threats The ecological and economic services provided by freshwater lakes, rivers, and fisheries (see Figure 3-11, p. 62) are severely threatened by human activities. Again, habitat disruption is the leading major threat. The 2005 Millennium Ecosystem Assessment reported that the amount of water held behind dams is currently three to six times the amount that flows in natural rivers. Also, we have greatly increased the amount of water we withdraw each year from rivers and lakes (mostly for agriculture). Dams and excessive water withdrawal destroy aquatic habitats and water flows and disrupt freshwater biodiversity. In addition, vast portions of the world’s freshwater wetlands have been destroyed—at least half of all wetlands in the
United States and much higher proportions in many of the other more-developed countries. As a result of these and other human activities, aquatic species have been crowded out of at least half of their habitat areas, worldwide, and 51% of freshwater fish species are threatened with extinction—more than other major types of species. Invasive species (see the Case Study that follows), pollution, and climate change threaten the ecosystems of lakes, rivers, and wetlands, and freshwater fish stocks are overharvested. Increasing human population pressures and projected climate change will only make these threats worse. Sustaining and restoring the biodiversity and ecological services provided by freshwater lakes and rivers is a complex and challenging task, as shown by the following Case Study.
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■ CAS E STUDY
Can the Great Lakes Survive Repeated Invasions by Alien Species? Invasions by nonnative species are a major threat to the biodiversity and ecological functioning of lakes, as illustrated by what has happened to the five Great Lakes, which straddle the U.S.-Canadian border. Collectively, the Great Lakes are the world’s largest body of fresh water. Since the 1920s, they have been invaded by at least 162 nonnative species and the number keeps rising. Many of the alien invaders arrive on the hulls or in bilge-water discharges of oceangoing ships entering the Great Lakes through the St. Lawrence Seaway. One of the biggest threats, the sea lamprey, attaches itself to almost any kind of fish and kills the victim by sucking out its blood (see Figure 5-7, p. 101). Over the years, it has depleted populations of many important sport fish species such as lake trout. Attempts to control the lamprey population have cost the U. S. and Canadian governments about $15 million a year. In 1986, larvae of the zebra mussel (see Figure 5-7, p. 101) arrived in ballast water discharged from a European ship near Detroit, Michigan (USA). This thumbnail-sized mollusk reproduces rapidly and has no known natural enemies in the Great Lakes. It has displaced other mussel species and thus depleted the food supply for some other Great Lakes aquatic species. The mussels have also disrupted city water supplies and other human systems to the cost of about $1 billion a year for the United States and Canada. The Asian carp is the most recent threat to the Great Lakes system. In the 1970s, catfish farmers in the southern United States imported two species of Asian carp to help clean their ponds. They escaped and invaded the Mississippi River system, and by 2010 had
6-7
▲
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made their way to within a few miles of Lake Michigan. They can grow as long as 1.2 meters (4 feet) and weigh up to 50 kilograms (110 pounds), and could be capable of devouring the food supply of most native fish species in the lakes. These fish have no natural predators in their new environment. In 2009, Joel Brammeler, president of the Alliance for the Great Lakes warned that “If Asian carp get into Lake Michigan, there is no stopping them.”
We Can Protect Freshwater Ecosystems by Protecting Watersheds Sustaining freshwater aquatic ecosystems begins with understanding that land and water are always connected in some way. For example, lakes and streams receive many of their nutrients from the ecosystems of bordering land. Such nutrient inputs come from falling leaves, animal feces, and pollutants generated by people, all of which are washed into bodies of water by rainstorms and melting snow. Therefore, to protect a stream or lake from excessive inputs of nutrients and pollutants, we must protect its watershed (Concept 6-6). As with marine systems, we can protect freshwater ecosystems through laws, economic incentives, and restoration efforts. For example, restoring and sustaining the ecological and economic services of rivers will probably require taking down some dams and restoring river flows. Inland wetlands are vital and productive parts of many watersheds. Because so many of the world’s wetlands have been degraded or destroyed, it is crucial that all remaining wetlands be preserved. Ecological restoration of degraded wetlands is a promising strategy that could be employed much more than it is (Concept 6-6).
What Should Be Our Priorities for Sustaining Terrestrial and Aquatic Biodiversity?
We can help to sustain the world’s biodiversity by mapping it, protecting biodiversity hotspots, creating large terrestrial and aquatic reserves, and carrying out ecological restoration of degraded terrestrial and aquatic ecosystems.
C O NC EPT 6-7
Using an Ecosystem Approach to Sustaining Biodiversity
•
Complete the mapping of the world’s terrestrial and aquatic biodiversity, identifying and locating as many species as possible in order to make conservation efforts more precise and cost-effective.
Edward O. Wilson, one of the world’s foremost experts on biodiversity, has proposed the following priorities for protecting as many as possible of the world’s remaining undisturbed ecosystems and species (Concept 6-7):
•
Identify and preserve the world’s terrestrial and aquatic biodiversity hotspots (Figure 6-12).
•
Keep intact the world’s remaining old-growth forests and cease all logging of such forests.
CHAPTER 6
Sustaining Biodiversity: The Ecosystem Approach
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•
Create large and fully protected marine reserves to allow damaged marine ecosystems and fish stocks to recover.
•
Protect and restore the world’s lakes and river systems by protecting their watersheds and by removing some dams.
•
Initiate ecological restoration projects worldwide in systems such as coral reefs and inland and coastal wetlands to help preserve the biodiversity and important natural services in those systems.
•
Make such conservation efforts beneficial to people who live in or near protected lands and waters, so that they can become partners in the protection and sustainable use of ecosystems without suffering any harm from these efforts.
According to Wilson, such a conservation strategy would cost about $30 billion per year—an GOOD amount that could be provided by a tax of one NEWS penny per cup on all the coffee consumed in the world each year. This strategy for protecting the earth’s vital biodiversity will not be implemented without bottom-up political pressure on elected officials from individual citizens and groups. It will also require cooperation among scientists, engineers, and key people in government and
the private sector. And it will be important for individuals to “vote with their wallets” by trying to buy only products and services that do not have harmful impacts on terrestrial or aquatic biodiversity. Preserving biodiversity involves applying the three principles of sustainability (see back cover). First, it means respecting biodiversity by trying to sustain it. If we are successful, we will also allow nature to restore and preserve the flows of energy from the sun through food webs and the cycling of nutrients in ecosystems, both of which are vital for the survival of our species and most others. Here are this chapter’s three big ideas: ■ The economic values of the important ecological services provided by the world’s ecosystems are far greater than the value of raw materials obtained from those systems. ■ Terrestrial and aquatic ecosystems are being severely degraded by human activities that lead to habitat disruption and loss of biodiversity. ■ We can help to sustain the world’s biodiversity by mapping it, protecting biodiversity hotspots, creating large terrestrial and aquatic reserves, and carrying out ecological restoration of degraded terrestrial and aquatic ecosystems.
We abuse land because we regard it as a commodity belonging to us. When we see land as a community to which we belong, we may begin to use it with love and respect. ALDO LEOPOLD
REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 110. Distinguish among an old-growth forest, a second-growth forest, and a tree plantation. What major ecological and economic benefits do forests provide? Summarize the conclusions of scientists and economists who have attempted to put a price tag on the major ecological services provided by forests and other ecosystems. 2. What harm is caused by building roads into previously inaccessible forests? Distinguish among selective cutting, clear-cutting, and strip cutting as methods for harvesting trees. Define deforestation. What is the estimated rate of deforestation worldwide? In what parts of the world is deforestation of the greatest concern? What are the major causes of tropical deforestation? 3. List four ways in which we can use the forests more sustainably. List three ways in which governments and individuals can reduce tropical deforestation. Describe Wangari Maathai’s Green Belt Movement.
4. What major environmental threats affect national parks? How could national parks in the United States be used more sustainably? Describe the beneficial effects of reintroducing the gray wolf into Yellowstone National Park in the United States. What percentage of the world’s land has been set aside and protected as nature reserves, and that percentage do conservation biologists believe should be protected? Describe the buffer zone concept. 5. Why is Costa Rica a global conservation leader? What is wilderness and why is it important? Describe the controversy over protecting wilderness in the United States. 6. Summarize the four-point plan generally followed in using the ecosystem approach to sustaining biodiversity. What is a biodiversity hotspot and why is it important to protect such areas? Summarize the story of threats to a biodiversity hotspot in Tanzania.
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7. Define ecological restoration and give four examples of it. Describe four ways in which scientists have learned to speed up ecological succession. Define and give three examples of reconciliation ecology. Why is the Blackfoot Challenge a classic example of reconciliation ecology? 8. What are three general patterns of marine biodiversity? Describe three major threats to marine biodiversity. Why is it difficult to protect marine biodiversity? Describe three ways in which we can protect marine biodiversity.
9. Describe three ways in which freshwater ecosystems are threatened. How is biodiversity threatened in the Great Lakes? In order to protect a freshwater system, what else must be protected? Why? 10. List seven priorities proposed by one biodiversity expert for protecting the world’s remaining ecosystems and species. How does implementing these priorities involve applying the three principles of sustainability? Note: Key terms are in bold type.
CRITICAL THINKING 1. List three ways you could apply Concept 6-6 to helping to sustain freshwater ecosystems and biodiversity. 2. Do you think that growing oil palm trees in plantations to obtain biodiesel fuel that will help cut dependence on oil and reduce vehicle CO2 emissions is important enough to justify burning and clearing some rain forests? Why or why not? Can you think of alternatives to cutting trees that would provide biofuels? What are they? 3. Should more-developed countries provide most of the money to help preserve remaining tropical forests in lessdeveloped countries? Explain. 4. Do you support the program that reintroduced populations of the gray wolf in the Yellowstone ecosystem in the United States (Science Focus, p. 119)? Explain. Another keystone species in the Yellowstone ecosystem is the grizzly bear. Suppose that the grizzly bears had died out or had been removed from the park. Would you support
a program to reintroduce this species into this ecosystem? Explain. 5. If you live near a body of water, think of three ways in which human activities on land affect that water through pollution, removal of the water, or some other effect. Do you depend on these activities in your daily living? (For example, does some of your food come from farms bordering an aquatic system?) If so, what are some changes you could make in your lifestyle to lessen your effect on this aquatic system? 6. Congratulations! You are in charge of the world. List the three most important features of your policies for using and managing (a) forests, (b) nature reserves such as parks and wildlife refuges, (c) marine ecosystems, and (d) freshwater ecosystems. 7. List two questions that you would like to have answered as a result of reading this chapter.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 6 for many study aids and ideas for further
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reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
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7
Food, Soil, and Pest Management
Key Questions and Concepts 7-1
What is food security and why is it difficult to attain?
7-4
How can we protect crops from pests more sustainably?
C O N C E P T 7 - 1 The greatest obstacles to providing enough food for the world’s human population are poverty, corruption, war, bad weather, and the harmful environmental effects of industrialized food production.
C O N C E P T 7 - 4 We can sharply cut pesticide use without decreasing crop yields by using a mix of cultivation techniques, biological pest controls, and small amounts of selected chemical pesticides as a last resort (integrated pest management).
How is food produced?
7-2
C O N C E P T 7 - 2 We have used high-input industrialized agriculture and lower-input traditional methods to greatly increase food supplies.
What environmental problems arise from food production?
7-3
Future food production may be limited by soil erosion and degradation, desertification, pollution of air and water, climate change, and loss of biodiversity. CONCEPT 7-3
How can we improve food security and produce food more sustainably?
7-5
C O N C E P T 7 - 5 A We can improve food security by creating programs to reduce poverty and chronic malnutrition, relying more on locally grown food, and cutting food waste. C O N C E P T 7 - 5 B More sustainable food production will require using resources more efficiently, sharply decreasing the harmful environmental effects of industrialized food production, and eliminating government subsidies that promote such harmful impacts.
There are two spiritual dangers in not owning a farm. One is the danger of supposing that breakfast comes from the grocery, and the other that heat comes from the furnace. ALDO LEOPOLD
Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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7-1
What Is Food Security and Why Is It Difficult to Attain?
▲
C O NC EPT 7-1 The greatest obstacles to providing enough food for the world’s human population are poverty, corruption, war, bad weather, and the harmful environmental effects of industrialized food production.
Many People Have Health Problems from Not Getting Enough to Eat Food security is the condition under which all or most of the people in a country have daily access to enough nutritious food to live active and healthy lives. Today, we produce more than enough food to meet the GOOD basic nutritional needs of every person on the NEWS earth. But even with this food surplus, one of every six people in less-developed countries is not getting enough to eat because of unequal access to available food. These people face food insecurity—living with chronic hunger and poor nutrition, which threatens one’s ability to lead a healthy and productive life. Most agricultural experts agree that the root cause of food insecurity is poverty, which prevents poor people from growing or buying enough food (Concept 7-1). For example, since 1990, India has been capable of producing enough grain for all of its people. But more than 200 million Indians—about one-fifth of the country’s population—are hungry because they cannot afford to buy or grow enough food. Other obstacles to food security are war and other sorts of conflict, corruption, and bad weather such as flooding rains, prolonged drought, or heat waves. These problems interfere with food distribution and transportation systems and can result in people going hungry while stored foods spoil. Food security can also be hindered at regional and global levels, for both poor and affluent people, by the harmful environmental and health effects of industrialized agriculture (Concept 7-1). In this chapter, we explore these problems and several possible solutions.
Many People Suffer from Chronic Hunger and Malnutrition To maintain good health and resist disease, individuals need fairly large amounts of macronutrients—carbohydrates, proteins, and fats—and smaller amounts of micronutrients—vitamins (such as A, B, C, and E) and minerals (such as iron, iodine, and calcium). People who cannot grow or buy enough food to meet their basic energy needs suffer from chronic undernutrition, or hunger. Most of the world’s chronically undernourished children live in low-income, lessdeveloped countries.
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Many of the world’s poor can afford only to live on a low-protein, high-carbohydrate, vegetarian diet consisting mainly of grains such as wheat, rice, or corn. They often suffer from chronic malnutrition—deficiencies of protein and other key nutrients. This weakens them, makes them more vulnerable to disease, and hinders the normal physical and mental development of children. The UN Food and Agriculture Organization (FAO) estimated that rising food prices and a sharp drop in international food aid increased the worlds’ number of hungry and malnourished people from 825 million in the mid-1990s to more than 1 billion by 2009. This number is nearly equal to the population of China and is more than three times the entire U.S. population. In less-developed countries, one of every six people (including about one of every three children younger than age 5) is chronically undernourished or malnourished. The FAO estimates that each year, nearly 6 million children under age five die prematurely from these conditions and from increased susceptibility to normally nonfatal infectious diseases (such as measles and diarrhea) because of their weakened condition. This means that each day, an average of 16,400 children younger than age five die from these mostly poverty-related causes.
Many People Do Not Get Enough Vitamins and Minerals According to the World Health Organization (WHO), one of every three people worldwide suffers from a deficiency of one or more vitamins and minerals, usually vitamin A, iron, and iodine. Most of these people live in less-developed countries. Some 250,000–500,000 children younger than age 6 go blind each year from a lack of vitamin A, and within a year, more than half of them die. Having too little iron (Fe)—a component of the hemoglobin that transports oxygen in the blood—causes anemia. It results in fatigue, makes infections more likely, and increases a woman’s chances of dying from hemorrhage in childbirth. According to the WHO, one of every five people in the world—mostly women and children in less-developed countries—suffers from iron deficiency. Elemental iodine (I) is essential for proper functioning of the thyroid gland, which produces hormones that control the body’s metabolism rate. Chronic lack
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of iodine can cause stunted growth, mental retardation, and goiter—a swollen thyroid gland that can lead to deafness. Almost one-third of the world’s people do not get enough iodine in their food and water. According to the United Nations, some 600 million people (about twice the current U.S. population) suffer from goiter. In addition, 26 million children suffer irreversible brain damage each year from lack of iodine. According to the FAO and the WHO, eliminating this serious health problem would cost the equivalent of only 2–3 cents per year for every person in the world.
Many People Have Health Problems from Eating Too Much Overnutrition occurs when food energy intake exceeds energy use and causes excess body fat. Too many calories, too little exercise, or both can cause overnutrition.
7-2
People who are underfed and underweight, as well as those who are overfed and overweight, face similar health problems: lower life expectancy, greater susceptibility to disease and illness, and lower productivity and life quality. We live in a world where about 1 billion people face health problems because they do not get enough to eat and another 1.1 billion have health problems from eating too much. In 2008, the U.S. Centers for Disease Control and Prevention (CDC) found that about two of every three American adults are overweight, including one of every three who are obese. A 2008 CDC study found that 59% of American children could be classified as overweight, obese, or extremely obese. Americans spend roughly $58 billion each year trying to lose weight, according to the research firm MarketData Enterprises. That is more than twice the $24 billion per year that the United Nations estimates is needed to eliminate undernutrition and malnutrition in the world.
How Is Food Produced?
▲
CONC EPT 7-2 We have used high-input industrialized agriculture and lower-input traditional methods to greatly increase food supplies.
Food Production Has Increased Dramatically Today, three systems supply most of our food. Croplands produce mostly grains and provide about 77% of the world’s food using 11% of its land area. Rangelands, pastures, and feedlots produce meat and meat products and supply about 16% of the world’s food using about 29% of the world’s land area. Fisheries and aquaculture (fish farming) supply about 7% of the world’s food. These three systems depend on a small number of plant and animal species. Of the estimated 50,000 plant species that people can eat, only 14 of them supply an estimated 90% of the world’s food calories. Just three grain crops—rice, wheat, and corn—provide about 48% of the calories that people consume directly. Two-thirds of the world’s people survive primarily on these three grains. Further, only a few species of mammals and fish provide most of the world’s meat and seafood. Such food specialization puts us in a vulnerable position, should the small number of crop strains, livestock breeds, and fish and shellfish species we depend on fail as a result of factors such as disease, environmental degradation, and climate change. This violates the biodiversity principle of sustainability, which calls for depending on a variety of food sources as an ecological insurance policy for dealing with changes in environmental conditions.
Despite such vulnerability, since 1960, there has been a staggering increase in global food production from all three of the major food production systems (Concept 7-2). This has occurred because of increased use of technological advances such as tractors and other farm machinery and high-tech fishing equipment. Other technological developments include irrigation, the manufacturing of inorganic chemical fertilizers and pesticides, the development of high-yield grain varieties, and industrialized production of large numbers of livestock and fish.
Industrialized Crop Production Relies on High-Input Monocultures We can roughly divide agriculture used to grow food crops into two types: industrialized agriculture and subsistence agriculture. Industrialized agriculture, or high-input agriculture, uses heavy equipment and large amounts of financial capital, fossil fuels, water, commercial inorganic fertilizers, and pesticides to produce single crops, or monocultures. Industrialized agriculture is practiced on one-fourth of all cropland, mostly in more-developed countries (Figure 7-1, p. 134), and now produces about 80% of the world’s food. Plantation agriculture is a form of industrialized agriculture used primarily in tropical less-developed
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Industrialized agriculture
Plantation agriculture
Intensive traditional agriculture
Shifting cultivation
Nomadic herding
No agriculture
Figure 7-1 Natural capital: This map shows the locations of the world’s principal types of food production. Excluding Antarctica and Greenland, agricultural systems cover almost one-third of the earth’s land surface.
countries. It involves growing cash crops such as bananas, soybeans, sugarcane, coffee, palm oil, and vegetables on large monoculture plantations, mostly for export to more-developed countries. A newer form of industrialized agriculture uses large arrays of greenhouses to raise crops indoors. In sunny areas, greenhouses can be used to grow crops year round. One particular form of greenhouse farming uses hydroponics, in which plants are grown by exposing their roots to a nutrient-rich water solution instead of soil.
Traditional Agriculture Often Relies on Low-Input Polycultures Some 2.7 billion people (39% of the world’s people) in less-developed countries practice traditional agriculture. It provides about one-fifth of the world’s food crops on about three-fourths of its cultivated land. There are two main types of traditional agriculture. Traditional subsistence agriculture uses mostly the labor of humans and draft animals to produce enough crops for a farm family’s survival, with little left over to
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sell or store as a reserve for hard times. In traditional intensive agriculture, farmers increase their inputs of human and draft-animal labor, animal manure for fertilizer, and water to produce enough food to feed their families and to sell some for income. Some traditional farmers focus on cultivating a single crop, but many grow several crops on the same plot simultaneously, a practice known as polyculture. Such crop diversity—an example of implementing the biodiversity principle of sustainability—reduces the chance of losing most or all of the year’s food supply to pests, bad weather, and other misfortunes. One type of polyculture, known as slash-and-burn agriculture, involves burning and clearing small plots in tropical forests, growing a variety of crops for a few years until the soil is depleted of nutrients, and then shifting to other plots to begin the process again. Early users of this method learned that each abandoned patch normally had to be left fallow (unplanted) for 10–30 years before the soil became fertile enough to grow crops again. In parts of South America and Africa, some traditional farmers using slash-and-burn methods grow as
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many as 20 different crops together on small cleared plots in tropical forests. The crops mature at different times, provide food throughout the year, and keep the soil covered to reduce erosion from wind and water. This lessens the need for fertilizer and water, because root systems at different depths in the soil capture nutrients and moisture efficiently, and ashes from the burning provide soil nutrients. Insecticides and herbicides are rarely needed because multiple habitats are created for natural predators of crop-eating insects, and weeds have trouble competing with the multitude and density of crop plants. Research shows that, on average, such low- GOOD input polyculture produces higher yields than NEWS does high-input monoculture. For example, ecologists Peter Reich and David Tilman found that carefully controlled polyculture plots with 16 different species of plants consistently out-produced plots with 9, 4, or only 1 type of plant species. Therefore, some analysts argue for greatly increased use of polyculture to produce food more sustainably. For one thing, they argue that it helps farmers to maintain fertile topsoil, on which all types of conventional crop production depend (Science Focus, p. 136).
yields by using large inputs of water, fertilizers, and pesticides. Third, increase the number of crops grown per year on a plot of land through multiple cropping. Between 1950 and 1970, this high-input approach dramatically increased crop yields in most of the world’s more-developed countries, especially the United States (see the Case Study that follows), in what was called the first green revolution. A second green revolution has been taking place since 1967. Fast-growing dwarf varieties of rice and wheat, specially bred for tropical and subtropical climates, have been introduced into middle-income, less-developed countries such as India, China, and Brazil. Producing more food on less land has helped to protect some biodiversity by preserving large areas of forests, grasslands, wetlands, and easily eroded mountain terrain that might otherwise be used for farming. Largely because of the two green revolutions, GOOD world grain production tripled between 1961 NEWS and 2009 (Figure 7-2, left). Per capita food production increased by 31% between 1961 and 1985, but since then it has declined slightly (Figure 7-2, right). ■ C AS E S T UDY
Industrialized Food Production in the United States
A Closer Look at Industrialized Crop Production Farmers have two ways to produce more food: farming more land or getting higher yields from existing cropland. Since 1950, about 88% of the increase in global food production has come from using high-input industrialized agriculture to increase crop yields in a process called the green revolution. A green revolution involves three steps. First, develop and plant monocultures of selectively bred or genetically engineered high-yield varieties of key crops such as rice, wheat, and corn. Second, produce high
In the United States, industrialized farming has evolved into agribusiness, as a small number of giant multinational corporations increasingly control the growing, processing, distribution, and sale of food in U.S. and global markets. In total annual sales, agriculture is bigger than the country’s automotive, steel, and housing industries combined. The entire agricultural system (from farm to grocery store and restaurant) employs more people than any other industry. Yet this amounts to only 3 of every 1,000 of the world’s farm workers. Farms in the
Per capita grain production (kilograms per person)
Grain production (millions of metric tons)
400 2,000 1,500 1,000 500 0 1960
1970
1980
1990
2000
Year Total World Grain Production
2010
350 300 250 200 150 1960
1970
1980
1990 2000 Year World Grain Production per Capita
2010
Figure 7-2 Global outlook: These graphs show that worldwide grain production of wheat, corn, and rice (left), and per capita grain production (right) grew sharply between1961 and 2009. The world’s three largest grainproducing countries—China, India, and the United States, in that order—produce almost half of the world’s grains. Question: Why do you think grain production per capita has grown less consistently than total grain production? (Data from U.S. Department of Agriculture, Worldwatch Institute, UN Food and Agriculture Organization, and Earth Policy Institute)
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SCIE N C E FO C US Soil Is the Base of Life on Land
S
oil is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and billions of living organisms, most of them microscopic decomposers. Soil formation begins when bedrock is slowly broken down into fragments and particles by physical, chemical, and biological processes, called weathering. Figure 7-A shows a profile of different-aged soils. Soil, on which all terrestrial life depends, is a key component of the earth’s natural capital. It supplies most of the nutrients needed for plant growth and purifies and stores water, while organisms living in the soil help to control the earth’s climate by removing carbon dioxide from the atmosphere and storing it as organic carbon compounds. Most soils that have developed over a long period of time, called mature soils, contain horizontal layers, or horizons, (Figure 7-A), each with a distinct texture and composition that vary with different types of soils. Think of them as the top three floors in the geological building of life underneath your feet.
Moss and lichen
Rock fragments
Organic debris
The roots of most plants and the majority of a soil’s organic matter are concentrated in the soil’s two upper layers, the O horizon of leaf litter and the A horizon of topsoil. In most mature soils, these two layers teem with bacteria, fungi, earthworms, and small insects, all interacting in complex ways. Bacteria and other decomposer microorganisms, found by the billions in every handful of topsoil, break down some of the soil’s complex organic compounds into a porous mixture of the partially decomposed bodies of dead plants and animals, called humus, and inorganic materials such as clay, silt, and sand. Soil moisture carrying these dissolved nutrients is drawn up by the roots of plants and transported through stems and into leaves as part of the earth’s chemical cycling processes. The B horizon (subsoil) and the C horizon (parent material) contain most of a soil’s inorganic matter, mostly broken-down rock consisting of varying mixtures of sand, silt, clay, and gravel. Much of it is transported by water from the A horizon (Figure 7-A). The C hori-
Oak tree Grasses and small shrubs
zon lies on a base of parent material, which is often bedrock. The spaces, or pores, between the solid organic and inorganic particles in the upper and lower soil layers contain varying amounts of air (mostly nitrogen and oxygen gas) and water. Plant roots use the oxygen for cellular respiration. As long as the O and A horizons are anchored by vegetation, the soil layers as a whole act as a sponge, storing water and nutrients, and releasing them in a nourishing trickle. Although topsoil is a renewable resource, it is renewed very slowly, which means it can be depleted. Just 1 centimeter (0.4 inch) of topsoil can take hundreds of years to form, but it can be washed or blown away in a matter of weeks or months when we plow grassland or clear a forest and leave its topsoil unprotected. Critical Thinking How does soil contribute to each of the four components of biodiversity described in Figure 3-1, p. 50?
Fern Millipede
Honey fungus
Earthworm Wood sorrel O horizon Leaf litter A horizon Topsoil
Mole Bacteria B horizon Subsoil
Fungus C horizon Parent material
Bedrock Immature so il
Mite Young soil
Mature soil
Nematode
Root system Red earth mite
Beetle larva
United States use industrialized agriculture to produce about 17% of the world’s grain. Since 1950, U.S. industrialized agriculture has GOOD more than doubled the yields of key crops such NEWS as wheat, corn, and soybeans without cultivating more land. Such yield increases have kept large areas of U.S.
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Figure 7-A This diagram shows a generalized soil profile and illustrates how soil is formed. Horizons, or layers, vary in number, composition, and thickness, depending on the type of soil. Questions: What role do you think the tree in this figure plays in soil formation? How might the soil formation process change if the tree were removed?
forests, grasslands, and wetlands from being converted to farmland. People in less-developed countries typically spend up to 40% of their income on food. The world’s 1.4 billion poorest people typically spend about 70% of their income on food. By contrast, because of the efficiency
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of U.S. agriculture, Americans spend an average of less than 10% of their household income on food, down from 18% in 1966. However, because of a number of hidden costs related to their food consumption, most American consumers are not aware that their total food costs are much higher than the market prices they pay. Such hidden costs include taxes to pay for farm subsidies— mostly to producers of corn, wheat, soybeans, and rice—and the costs of pollution and environmental degradation caused by industrialized agriculture, as we discuss later in this chapter.
Crossbreeding and Genetic Engineering Can Produce New Varieties of Crops and Livestock For centuries, farmers and scientists have used crossbreeding through artificial selection to develop genetically improved varieties of crops and livestock animals. Such selective breeding in this first gene revolution has yielded amazing results. Ancient ears of corn were about the size of your little finger, and wild tomatoes were once the size of grapes. Traditional crossbreeding is a slow process, typically taking 15 years or more to produce a commercially valuable new crop variety, and it can combine traits only from species that are genetically similar. Typically, resulting varieties remain useful for only 5–10 years before pests and diseases reduce their effectiveness. But important advances are still being made with this method. Today, scientists are creating a second gene revolution by using genetic engineering to develop genetically improved strains of crops and livestock animals. It involves altering an organism’s genetic material through adding, deleting, or changing segments of its DNA to produce desirable traits or to eliminate undesirable ones. It enables scientists to transfer genes between different species that would not normally interbreed in nature. The resulting organisms are called genetically modified organisms (GMOs). Compared to traditional crossbreeding, genetic engineering takes about half as long to develop a new crop variety, usually costs less, and allows for the insertion of genes from almost any other organism into crop cells. Ready or not, much of the world is entering the age of genetic engineering. Bioengineers plan to develop new GM varieties of crops that are resistant to heat, cold, herbicides, insect pests, parasites, viral diseases, drought, and salty or acidic soil. They also hope to develop crop plants that can grow faster and survive with little or no irrigation and with less fertilizer and pesticides. For example, bioengineers have altered citrus trees, which normally take 6 years to produce fruit, to yield fruit in only 1 year. They hope to go further and use advanced tissue culture techniques to mass-produce only orange juice sacs, which would eliminate the need for citrus orchards.
Many scientists believe that such innovations hold great promise for helping to improve global food security. Others warn that genetic engineering is not free of drawbacks, which we examine later in this chapter.
Meat Production Has Grown Steadily Between 1961 and 2010, world meat production— mostly beef, pork, and poultry—increased nearly fivefold and average meat consumption per person more than doubled. Each year, some 56 billion animals— 8 times the human population—are raised and slaughtered for food. Global meat production is likely to more than double again by 2050 as more middle-income people begin consuming more meat and animal products in rapidly developing countries such as China and India. About half of the world’s meat comes from livestock grazing on grass in unfenced rangelands and enclosed pastures. The other half is produced through an industrialized factory farm system. It involves raising large numbers of animals such as veal calves, pigs, chickens, and turkeys—bred to gain weight quickly, mostly in crowded feedlots and concentrated animal feeding operations (CAFOs). They are fed grain, fish meal, or fish oil, which are usually supplemented with growth hormones and antibiotics. Industrialized meat production may face certain limits in the future. For example, if we include land used to grow the grain fed to livestock, the FAO estimates that 30% of the earth’s ice-free land is already directly or indirectly involved in livestock production. Land is a finite resource.
Fish and Shellfish Production Have Increased Dramatically The world’s third major food-producing system consists of fisheries and aquaculture. A fishery is a concentration of particular aquatic species suitable for commercial harvesting in a given ocean area or inland body of water. Industrial fishing fleets harvest most of the world’s marine catch of wild fish. In 2010, according to the FAO, half of all the fish eaten in the world were produced through aquaculture—the practice of raising freshwater and marine fish species in freshwater ponds or underwater cages in coastal or open ocean waters. Figure 7-3 (p. 138) shows the effects of the global efforts to boost seafood production through fishing and aquaculture. Since 1950, the world fish catch (marine and freshwater harvests, excluding aquaculture) has increased almost sevenfold. Aquacultural production in the same period increased over 40-fold. Aquaculture is the world’s fastest-growing type of food production. Globally, aquaculture is devoted mostly to raising species that feed on algae or other plants— mainly carp in China and India, catfish in the United CONCEPT 7-2
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Industrialized Crop Production Requires Huge Inputs of Energy
Production (millions of metric tons)
140 120 100 80
Wild catch
60 40 20
Aquaculture
0 1950
1960
1970
1980 1990 Year Total World Fish Catch
2000
2010
Figure 7-3 World seafood production, including both wild catch and aquaculture, increased sharply between 1950 and 2006. Question: What are two trends that you can see in these data? (Data from UN Food and Agriculture Organization, U.S. Census Bureau, and Worldwatch Institute)
States, tilapia in several countries, and shellfish in several coastal countries. But the farming of meat-eating species such as shrimp and salmon is growing rapidly, especially in more-developed countries.
The industrialization of food production has been made possible by the availability of energy, mostly from oil and natural gas. It is used to run farm machinery, irrigate crops, produce pesticides and fertilizers, and transport farm products. Fossil fuels are also used to process food and transport it long distances within and between countries. Putting food on the table consumes about 19% of all commercial energy used in the United States each year (Figure 7-4). The input of energy needed to produce a unit of food has fallen considerably, so that most food crops in the United States provide more food energy than the energy used to grow them. However, when we consider the energy used to grow, store, process, package, transport, refrigerate, and cook all plant and animal foods, it takes about 10 units of nonrenewable fossil fuel energy to put 1 unit of food energy on the table. This huge expenditure of energy to produce food contributes to several environmental problems resulting from industrialized food production.
4%
2%
6%
Crops
Livestock
Food processing
5%
Food distribution and preparation
Food production Figure 7-4 Industrialized agriculture uses about 19% of all the commercial energy used in the United States, and food travels an average 2,400 kilometers (1,300 miles) from farm to plate. The resulting pollution degrades the air and water and contributes to projected climate change. (Data from David Pimentel and Worldwatch Institute)
7-3
What Environmental Problems Arise from Food Production?
▲
C O NC EPT 7-3 Future food production may be limited by soil erosion and degradation, desertification, pollution of air and water, climate change, and loss of biodiversity.
Producing Food Has Major Environmental Impacts According to many analysts, agriculture has greater harmful environmental impacts than any other human activity and these environmental effects may limit future food production.
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Crop yields in some areas may decline because of environmental factors such as erosion and degradation of topsoil, depletion and pollution of underground and surface water supplies used for irrigation, emission of greenhouse gases that contribute to projected climate change, and loss of croplands to urbanization (Concept 7-3). Figure 7-5 summarizes the harmful effects of
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Natural Capital Degradation Food Production
Biodiversity Loss Loss and degradation of grasslands, forests, and wetlands in cultivated areas Fish kills from pesticide runoff Killing wild predators to protect livestock
Soil
Water
Air Pollution
Erosion
Water waste
Loss of fertility
Aquifer depletion
Emissions of greenhouse gas CO2 from fossil fuel use
Salinization
Increased runoff, sediment pollution, and flooding from cleared land
Emissions of greenhouse gas N2O from use of inorganic fertilizers
Pollution from pesticides and fertilizers
Emissions of greenhouse gas methane (CH4) by cattle (mostly belching)
Waterlogging Desertification Increased acidity
Loss of genetic diversity of wild crop strains replaced by monoculture strains
Algal blooms and fish kills in lakes and rivers caused by runoff of fertilizers and agricultural wastes
Other air pollutants from fossil fuel use and pesticide sprays
Human Health Nitrates in drinking water (blue baby) Pesticide residues in drinking water, food, and air Contamination of drinking and swimming water from livestock wastes Bacterial contamination of meat
Figure 7-5 Food production has a number of harmful environmental effects (Concept 7-3). According to a 2008 study by the FAO, more than 20% of the world’s cropland (65% in Africa) has been degraded to some degree by soil erosion, salt buildup, and chemical pollution. This threatens the food supply for about a quarter of the world’s population. Question: Which item in each of these categories do you believe is the most harmful?
modern agriculture on air, fertile soil, water, and biodiversity. We now explore such effects in greater depth, starting with the problems of erosion and degradation of soils.
Topsoil Erosion Is a Serious Problem in Parts of the World Soil erosion is the movement of soil components, especially surface litter and topsoil (Figure 7-A, p. 136), from one place to another by the actions of wind and water. Some erosion of topsoil is natural, and some is caused by human activities. In undisturbed, vegetated ecosystems, the roots of plants help to anchor the topsoil so that it is not lost faster than it forms. Undisturbed topsoil can also store water and nutrients and release them in order to nourish plants. Flowing water is the largest cause of erosion. Wind also loosens and blows topsoil particles away, especially in areas with a dry climate and relatively flat, exposed land. We lose natural capital in the form of fertile topsoil when we destroy soil-holding grasses through activities such as plowing, deforestation, overgrazing of livestock, and off-road vehicle use.
Erosion of topsoil has two major harmful effects. One is loss of soil fertility through depletion of plant nutrients in topsoil. The other is water pollution in nearby surface waters, where eroded topsoil ends up as sediment. This can kill fish and shellfish, and clog irrigation ditches, boat channels, reservoirs, and lakes. A joint survey by the UN Environment Programme (UNEP) and the World Resources Institute estimated that topsoil is eroding faster than it forms on about 38% of the world’s cropland (Figure 7-6, p. 140). Some analysts contend that topsoil erosion estimates are overstated because they do not account for the abilities of some local farmers to restore degraded land. They also point out that eroded topsoil does not always move very far and is sometimes deposited on the same slope, valley, or plain from which it came. Consequently, in some places, the loss in crop yields in one area can be offset by increased yields elsewhere.
Drought and Flooding Can Degrade Cropland Desertification occurs when the productive potential of topsoil falls by 10% or more because of a combination CONCEPT 7-3
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Figure 7-6 Natural capital degradation: Topsoil erosion is a serious problem in some parts of the world. In 2008, the Chinese government estimated that one-third of China’s land suffers from serious topsoil erosion. Question: Can you see any geographical pattern associated with this problem? (Data from UN Environment Programme and the World Resources Institute)
Serious concern Some concern Stable or nonvegetative
of prolonged drought and human activities that reduce or degrade the topsoil. Only in extreme cases does desertification lead to what we call desert. Over thousands of years, the earth’s deserts have expanded and contracted, mostly because of natural climate change. However, human use of the land, especially for agricultural purposes, has accelerated desertification in some parts of the world. In 2007, the FAO estimated that some 70% of world’s drylands used for agriculture are degraded and threatened by desertification. Most of these lands are in Africa and Asia. On the other hand, excessive irrigation, or watering of soil, has serious consequences as well. Currently, about 45% of the world’s food is produced on the onefifth of the world’s cropland that is irrigated. But irrigation has a downside. Most irrigation water is a dilute solution of various salts such as sodium chloride (NaCl) that are picked up as the water flows over
Salinization
Transpiration Evaporation
1. Irrigation water contains small amounts of dissolved salts. 2. Evaporation and transpiration leave salts behind.
or through soil and rocks. Irrigation water that has not been absorbed into the topsoil evaporates, leaving behind a thin crust of dissolved mineral salts in the topsoil. Repeated applications of irrigation water in dry climates lead to the gradual accumulation of salts in the upper soil layers—a soil degradation process called salinization (Figure 7-7). It stunts crop growth, lowers crop yields, and can eventually kill plants and ruin the land. The United Nations estimates that severe salinization has reduced yields on at least one-tenth of the world’s irrigated cropland, and the problem is getting worse. The most severe salinization occurs in China, India, Egypt, Pakistan, and Iraq. Salinization affects almost one-fourth of irrigated cropland in the United States, especially in western states. Another problem with irrigation is waterlogging (Figure 7-7), in which water accumulates underground and gradually raises the water table, especially when farmers apply large amounts of irrigation water in an effort to leach salts deeper into the soil. Waterlogging deprives plants of the oxygen they need to survive. Without adequate drainage, waterlogging lowers the productivity of crop plants and kills them after prolonged exposure. At least one-tenth of the world’s irrigated land suffers from waterlogging, and the problem is getting worse.
3. Salt builds up in soil. Waterlogging 1. Precipitation and irrigation water percolate downward. 2. Water table rises.
Waterlogging
Less permeable clay layer
Figure 7-7 Natural capital degradation: Salinization and waterlogging of soil on irrigated land without adequate drainage can decrease crop yields.
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Food Production Systems Have Caused Major Losses of Biodiversity Biodiversity is threatened when forests are cleared and grasslands are plowed up and replaced with croplands (Concept 7-3). One of the fastest-growing threats to the world’s biodiversity is the clearing or planting of large areas of tropical forest in Brazil’s Amazon basin.
Food, Soil, and Pest Management
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A related problem is the increasing loss of agrobiodiversity—the world’s genetic variety of animal and plant species used to provide food. Scientists estimate that since 1900, we have lost three-fourths of the genetic diversity of agricultural crops. For example, India once planted 30,000 varieties of rice. Now more than 75% of its rice production comes from only ten varieties and soon, almost all of its production may come from just one or two varieties. In the United States, about 97% of the food plant varieties available to farmers in the 1940s no longer exist, except perhaps in small amounts in seed banks and in the backyards of a few gardeners. In other words, we are rapidly shrinking the world’s genetic “library,” which is critical for increasing food yields. This failure to preserve agrobiodiversity as an ecological insurance policy is a serious violation of the biodiversity principle of sustainability.
Genetic Engineering Could Solve Some Problems but Create Others Despite its promise, controversy has arisen over the use of genetically modified (GM) food and other products of genetic engineering. Its producers and investors see GM food as a potentially sustainable way to solve world hunger problems and improve human health. But some critics consider it potentially dangerous “Frankenfood.” Figure 7-8 summarizes the projected advantages and disadvantages of this developing technology. Critics recognize the potential benefits of GM crops, but they warn that we know too little about the longterm potential harm to human health and ecosystems from the widespread use of such crops. They point out that if GM organisms that are released into the environment cause some unintended harmful genetic and ecological effects, as some scientists expect, those organisms cannot be recalled. For example, genes in plant pollen from genetically engineered crops can spread among nonengineered species. The new strains can then form hybrids with wild crop varieties, which could reduce the natural genetic biodiversity of wild strains. This could in turn reduce the gene pool needed to crossbreed new crop varieties and to develop new genetically engineered varieties. Most scientists and economists who have evaluated the genetic engineering of crops believe that its potential benefits will eventually outweigh its risks. However, critics, including the Ecological Society of America, call for more controlled field experiments, long-term testing to better understand the ecological and health risks, and stricter regulation of this rapidly growing technology. Indeed, a 2008 International Assessment of Agricultural Knowledge by 400 scientists with input from more than 50 countries raised serious doubts about the ability of GM crops to increase food security compared to other more effective and sustainable alternative solutions (which we discuss later in this chapter).
Trade-Offs Genetically Modified Crops and Foods A d vant ag es
D i s a d v a nt a g e s
Need less fertilizer
Unpredictable genetic and ecological effects
Need less water More resistant to insects, disease, frost, and drought Grow faster May need less pesticides or tolerate higher levels of herbicides May reduce energy needs
Harmful toxins and new allergens in food No increase in yields More pesticideresistant insects and herbicide-resistant weeds Could disrupt seed market Lower genetic diversity
Figure 7-8 Genetically modified crops and foods have advantages and disadvantages. Questions: Which two advantages and which two disadvantages do you think are the most important? Why?
There Are Limits to Expansion of the Green Revolutions Several factors have limited the success of the green revolutions to date and may limit them in the future (Concept 7-3). Without huge inputs of inorganic fertilizer, pesticides, and water, most green revolution and genetically engineered crop varieties produce yields that are no higher (and are sometimes lower) than those from traditional strains. In addition, these high-inputs cost too much for most subsistence farmers in lessdeveloped countries. Scientists point out that continuing to increase these inputs eventually produces no additional increase in crop yields. Can we expand the green revolutions by irrigating more cropland? Between 1950 and 2006, the world’s area of irrigated cropland tripled, with most of the growth occurring from 1950 to 1978. However, since 1978, the amount of irrigated land per person has been declining, and it is projected to fall much more between 2010 and 2050. One reason for this is population growth, which is projected to add 2.3 billion more people between 2010 and 2050. Other factors are depletion of underground water supplies (aquifers), wasteful use of irrigation water, soil salinization, and the fact that
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most of the world’s farmers do not have enough money to irrigate their crops. Can we increase the food supply by cultivating more land? Clearing tropical forests and irrigating arid land could more than double the area of the world’s cropland. But much of this land has poor soil fertility, steep slopes, or both. Cultivating such land usually is expensive and it is unlikely to be sustainable. Furthermore, these potential increases in cropland would not offset the projected loss of almost one-third of today’s cultivated cropland due to erosion, overgrazing and other forms of soil degradation, and urbanization (Concept 7-3). Such cropland expansion would also seriously reduce wildlife habitats and biodiversity. In addition, during this century, fertile croplands in coastal areas are likely to be flooded by rising sea levels resulting from projected climate change. Food production could also drop sharply in some areas because of increased drought and longer and more intense heat waves, also resulting from projected climate change. Crop yields could be increased with the use of conventional or genetically engineered crops that are more tolerant of drought and cold. But so far, such crops have not been developed and time is running out as the speed of climate change is projected to increase in the next few decades.
Industrialized Meat Production Has Harmful Environmental Consequences Proponents of industrialized meat production point out that it has increased meat supplies and helped to keep food prices affordable for many people. But environmental scientists point out that such systems use large amounts of energy and water and produce huge amounts of animal wastes that sometimes pollute surface water and groundwater while saturating the air with their odors. Figure 7-9 summarizes the advantages and disadvantages of industrialized meat production. Industrial livestock production is one of the world’s biggest consumers of water. Producing just 0.2 kilograms (8 ounces) of grain-fed beef requires 25,000 liters (6,600 gallons) of water. This does not include the large amount of water used in slaughtering cattle and processing their meat. Fossil fuel energy (mostly from oil) is also an essential ingredient in industrialized meat production (Figure 7-4). Using this energy pollutes the air and water and emits greenhouse gases that contribute to projected climate change. Livestock production generates about 18% of the world’s greenhouse gases—more than the transportation sector generates, according to the FAO. Because of their unique digestive systems, beef and dairy cows also release methane—the second most powerful greenhouse gas after carbon dioxide. This accounts for 16% of the global annual emissions of methane.
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Trade-Offs Animal Feedlots A d vant ag es
D i s a d v a nt a g e s
Increased meat production
Large inputs of grain, fish meal, water, and fossil fuels
Higher profits Less land use Reduced overgrazing Reduced soil erosion Protection of biodiversity
Greenhouse gas (CO2 and CH4) emissions Concentration of animal wastes that can pollute water Use of antibiotics can increase genetic resistance to microbes in humans
Figure 7-9 Animal feedlots and confined animal feeding operations have advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
According to the U.S. Department of Agriculture (USDA), animal waste produced by the American meat industry amounts to about 130 times the amount of waste produced by the country’s human population. Globally, only about half of all manure is returned to the land as nutrient-rich fertilizer—a violation of the nutrient cycling principle of sustainability. Much of the other half of this waste ends up polluting the air, water, and soil, and producing foul odors. Experts expect industrialized meat production to expand rapidly. This will increase pressure on the world’s grain supply. Producing more meat will also increase pressure on the world’s fish supply, because about 37% of the marine fish catch is converted to fish meal and fish oil, which are used to feed livestock and carnivorous fish raised by aquaculture.
Aquaculture Can Harm Aquatic Ecosystems Figure 7-10 lists the major advantages and disadvantages of aquaculture, which in 2010 accounted for roughly half of global seafood production. Some analysts warn that the harmful environmental effects of aquaculture could limit its future production potential (Concept 7-3). One problem is that fish raised on fish meal or fish oil can be contaminated with long-lived toxins such as PCBs found in ocean bottom sediments. In 2003, samples from
Food, Soil, and Pest Management
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Trade-Offs
Figure 7-10 Aquaculture has advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Aquaculture Adva nta ge s
Disad vant ag es
High efficiency
Large inputs of land, feed, and water
High yield
Large waste output
Reduces overharvesting of fisheries
Loss of mangrove forests and estuaries
Low fuel use
Some species fed with grain, fish meal, or fish oil
High profits
Dense populations vulnerable to disease
7-4
various U.S. grocery stores revealed that farmed salmon had 7 times more PCBs than wild salmon had and 4 times more than feedlot beef had. In Section 7-5 of this chapter, we consider some possible solutions to the serious environmental problems that result from food production and some ways to produce food more sustainably. But first, let us consider a special set of environmental problems and solutions related to protecting food supply systems from pests.
How Can We Protect Crops from Pests More Sustainably?
▲
CONC EPT 7-4 We can sharply cut pesticide use without decreasing crop yields by using a mix of cultivation techniques, biological pest controls, and small amounts of selected chemical pesticides as a last resort (integrated pest management).
Nature Controls the Populations of Most Pests
We Use Pesticides to Help Control Pest Populations
A pest is any species that interferes with human welfare by competing with us for food, invading lawns and gardens, destroying building materials, spreading disease, invading ecosystems, or simply being a nuisance. Worldwide, only about 100 species of plants (“weeds”), animals (mostly insects), fungi, and microbes cause most of the damage to the crops we grow. In natural ecosystems and on farms using polyculture, natural enemies (predators, parasites, and disease organisms) control the populations of most potential pest species. For example, the world’s 30,000 known species of spiders kill far more insects every year than humans do by using chemicals. When we clear forests and grasslands, plant monoculture crops, and douse fields with chemicals that kill pests, we upset many of these natural population checks and balances. Then we must devise and pay for ways to protect our monoculture crops, tree plantations, lawns, and golf courses from insects and other pests that nature once largely controlled at no charge.
We have developed a variety of pesticides—chemicals used to kill or control populations of organisms that we consider undesirable. Common types of pesticides include insecticides (insect killers), herbicides (weed killers), fungicides (fungus killers), and rodenticides (rat and mouse killers). We did not invent the use of chemicals to repel or kill other species. For nearly 225 million years, plants have been producing chemicals called biopesticides to ward off, deceive, or poison the insects and herbivores that feed on them. This battle produces a neverending, ever-changing coevolutionary process: insects and herbivores overcome various plant defenses through natural selection, then new plant defenses are favored by natural selection, and the process is repeated in this ongoing cycle. Since 1950, synthetic (human-made) pesticide use has increased more than 50-fold, and most of today’s pesticides are 10–100 times more toxic than those used in the 1950s. About three-fourths of these chemicals are
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I N D I V ID U ALS MAT T E R Rachel Carson
R
achel Carson began her professional career as a biologist for the Bureau of U.S. Fisheries (now called the U.S. Fish and Wildlife Service). In that capacity, she carried out research in oceanography and marine biology, and wrote articles and books about the oceans and topics related to the environment. In 1958, the commonly used pesticide DDT was sprayed to control mosquitoes near the home and private bird sanctuary of one of Carson’s friends. After the spraying, her friend witnessed the agonizing deaths of several birds. She begged Carson to find someone to investigate the effects of pesticides on birds and other wildlife. Carson decided to look into the issue herself and found very little independent research on the environmental effects of pesticides. As a well-trained scientist, she surveyed the scientific literature, became convinced that pesticides could harm wildlife and humans, and gathered information about the harmful effects of the widespread use of pesticides.
In 1962, she published her findings in popular form in Silent Spring, a book whose title warned of the potential silencing of “robins, catbirds, doves, jays, wrens, and scores of other bird voices” because of their exposure to pesticides. Many scientists, politicians, and policy makers read Silent Spring, and the public embraced it. Chemical manufacturers understandably saw the book as a serious threat to their booming pesticide business, and they mounted a campaign to discredit Carson. A parade of critical reviewers and industry scientists claimed that her book was full of inaccuracies, made selective use of research findings, and failed to give a balanced account of the benefits of pesticides. Some critics even claimed that, as a woman, Carson was incapable of understanding such a highly scientific and technical subject. Others charged that she was just a hysterical woman and radical nature lover who was trying to scare the public in an effort to sell books.
During these intense attacks, Carson was a single mother and the sole caretaker of an aged parent. She was also suffering from terminal breast cancer. Yet she strongly defended her research and countered her critics. She died in 1964—about 18 months after the publication of Silent Spring—without knowing that many historians would consider her work to be an important contribution to the modern environmental movement then emerging in the United States. It has been correctly noted that Carson made some errors in Silent Spring. But critics concede that the threat to birds and ecosystems—one of Carson’s main messages—was real and that most of her errors can be attributed to the primitive state of research on the topics she covered in her day. Further, her critics cannot dispute the fact that her wakeup call got the public and the scientific community focused on the potential threats from the uncontrolled use of pesticides. This eventually led to the banning of many pesticides in the United States and other countries.
used in more-developed countries, but their use in lessModern Synthetic Pesticides developed countries is soaring. Have Several Advantages Some pesticides, called broad-spectrum agents, are toxic to many pest and non-pest species. Others, called Conventional chemical pesticides have advantages and selective, or narrow-spectrum, agents, are effective against a disadvantages (Figure 7-11). Proponents contend that narrowly defined group of organisms. their benefits outweigh their harmful effects. They point Pesticides vary in their persistence, the length of time to the following benefits: they remain deadly in the environment. About one• They save human lives. Since 1945, DDT and other fourth of pesticide use in the United States is devoted insecticides probably have prevented the premato trying to rid houses, gardens, lawns, parks, playture deaths of at least 7 million people (some say ing fields, swimming pools, and golf courses of pests. as many as 500 million) from insect-transmitted According to the U.S. Environmental Protection Agency diseases such as malaria (carried by the Anopheles (EPA), the average lawn in the United States is doused with 10 times more synthetic pesticides per unit of land area than are put on U.S. cropland. In 1962, biologist Rachel Carson warned against relying too heavily on synthetic organic chemicals to kill insects and Conventional Chemical Pesticides other species we deem pests (Individuals Matter, above). A dv a ntages Dis advantages
Trade-Offs
Save lives
Figure 7-11 Conventional chemical pesticides have advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
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Promote genetic resistance
Increase food supplies
Kill natural pest enemies
Profitable
Pollute the environment
Work fast
Can harm wildlife and people
Safe if used properly
Are expensive for farmers
Food, Soil, and Pest Management
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apply by aerial spraying or ground spraying do not reach the target pests and end up in the air, surface water, groundwater, bottom sediments, food, and on nontarget organisms, including humans and wildlife.
mosquito), bubonic plague (carried by rat fleas), and typhus (carried by body lice and fleas). •
They increase food supplies by reducing food losses from pests. According to the FAO, 55% of the world’s potential human food supply is lost to pests. However, the question of whether pesticides actually reduce crop losses is open to debate (Science Focus, p. 146).
•
They increase profits for farmers. Officials of pesticide companies estimate that every dollar spent on pesticides leads to an increase in U.S. crop yields worth approximately $4.
•
They work fast. Pesticides control most pests quickly, have a long shelf life, and are easily shipped and applied.
•
When used properly, the health risks of some pesticides are very low, relative to their benefits, according to pesticide industry scientists (although other scientists have debated this point).
•
Newer pest control methods are safer and more effective than many older ones. Greater use is being made of biopesticides, which are safer to use and less damaging to the environment than are many older pesticides. Genetic engineering is also being used to develop pest-resistant crop strains and genetically altered crops that produce natural pesticides.
•
Some pesticides harm wildlife. According to the USDA and the U.S. Fish and Wildlife Service, every year, pesticides applied to cropland wipe out about 20% of U.S. honeybee colonies and damage another 15%. Pesticides also kill more than 67 million birds and 6–14 million fish every year. According to a 2004 study by the Center for Biological Diversity, pesticides also menace one of every three endangered and threatened species in the United States.
•
Some pesticides threaten human health. The WHO and UNEP estimate conservatively that, each year, pesticides seriously poison at least 3 million agricultural workers in less-developed countries and at least 300,000 workers in the United States. They also cause 20,000–40,000 deaths per year, worldwide. Each year, more than 250,000 people in the United States become ill because of household pesticide use. Such pesticides are a major source of accidental poisonings and deaths of young children. Also, according to studies by the National Academy of Sciences, exposure to legally allowed pesticide residues in food causes 4,000–20,000 cases of cancer per year in the United States. Some scientists are concerned about possible genetic mutations, birth defects, nervous system and behavioral disorders, and effects on the immune and endocrine systems from long-term exposure to low levels of various pesticides.
Modern Synthetic Pesticides Have Several Disadvantages Opponents of widespread pesticide use believe that the harmful effects of these chemicals (Figure 7-11, right) outweigh their benefits (Figure 7-11, left). They cite several serious problems with the use of conventional pesticides: •
•
•
•
They accelerate the development of genetic resistance to pesticides in pest organisms. Insects breed rapidly and within 5–10 years (much sooner in tropical areas) they can develop immunity to widely used pesticides through natural selection, and then come back stronger than before. Since 1945, about 1,000 species of insects and rodents (mostly rats) and 550 types of weeds and plant diseases have developed genetic resistance to one or more pesticides. They can put farmers on a financial treadmill. Because of genetic resistance, farmers can find themselves having to pay more and more for a pest control program that can become less and less effective. Some insecticides kill natural predators and parasites that help control the pest populations. About 100 of the 300 most destructive insect pests in the United States were minor pests until widespread use of insecticides wiped out many of their natural predators. Pesticides do not stay put and can pollute the environment. According to the USDA, about 98–99.9% of the insecticides and more than 95% of the herbicides we
Finally, pesticides do not consistently reduce crop losses due to pests, and this may become even more uncertain as pests evolve pesticide resistance. The pesticide industry disputes these claims, arguing that the exposures are not high enough to cause serious environmental or health problems. Figure 7-12 lists some ways in which you can reduce your exposure to pesticides.
What Can You Do? Reducing Exposure to Pesticides ■
Grow some of your food using organic methods
■
Buy certified organically produced food
■
Wash and scrub all fresh fruits, vegetables, and wild foods you pick
■
Eat less meat, no meat, or certified organically produced meat
■
Trim the fat from meat
Figure 7-12 Individuals matter: You can reduce your exposure to pesticides. Because food prices do not include the harmful health and environmental effects of industrialized agriculture, some of these options will cost you more money. Questions: Which three of these steps do you think are the most important ones to take? Why?
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SCIE N C E FO C US Pesticides Do Not Always Reduce Crop Losses
A
t least one scientist has concluded that pesticide use has not reduced U.S. crop losses to pests, mostly because of genetic resistance and reduction of natural predators. When David Pimentel, an expert in insect ecology, evaluated data from more than 300 agricultural scientists and economists, he reached three major conclusions: • First, although the use of synthetic pesticides has increased 33-fold since 1942, 37% of the U.S. food supply is lost to pests today compared to 31% in the 1940s. Since 1942, losses attributed to insects almost doubled from 7% to 13%,
despite a tenfold increase in the use of synthetic insecticides. • Second, estimated environmental, health, and social costs of pesticide use in the United States, according to the International Food Policy Research Institute, are $100–200 billion per year, or $5–10 in damages for every dollar spent on pesticides. • Third, alternative pest management practices could cut the use of chemical pesticides on 40 major U.S. crops by as much as 50% without reducing crop yields.
Laws and Treaties Can Help to Protect Us from the Harmful Effects of Pesticides There is controversy over how well U.S. citizens are protected from the harmful effects of pesticides. Between 1972 and 2009, the Environmental Protection Agency (EPA) banned or severely restricted the use of 64 active pesticide ingredients, including DDT and most other chlorinated hydrocarbon insecticides. However, according to studies by the National Academy of Sciences, federal laws regulating pesticide use in the United States are inadequate and poorly enforced. One such study found that as much as 98% of the potential risk of developing cancer from pesticide residues on food grown in the United States would be eliminated if EPA standards were as strict for pre-1972 pesticides as they are for later ones. Although laws within countries protect citizens to some extent, banned or unregistered pesticides may be manufactured in one country and exported to other countries. For example, U.S. pesticide companies make and export to other countries pesticides that have been banned or severely restricted—or never even evaluated—in the United States. Other industrial countries also export banned or unapproved pesticides. But what goes around can come around. In what environmental scientists call a circle of poison, or the boomerang effect, residues of some banned or unapproved chemicals exported to other countries can return to the exporting countries on imported food. The wind can also carry persistent pesticides from one country to another. Environmental and health scientists have urged the U.S. Congress—without success—to ban such exports. Supporters of the exports argue that such sales increase economic growth and provide jobs, and that banned
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The pesticide industry disputes these findings. Nevertheless, numerous studies and experience show that pesticide use can be reduced sharply without reducing yields. Sweden has cut pesticide use in half with almost no decrease in crop yields. After a two-thirds cut in pesticide use on rice in Indonesia, yields increased by 15%. Critical Thinking If pesticides have not reduced crop losses, why do you think farmers keep using them?
pesticides are exported only with the consent of the importing countries. They also contend that if the United States did not export pesticides, other countries would. In 1998, more than 50 countries developed an international treaty that requires exporting countries to have informed consent from importing countries before exporting any of 22 pesticides and 5 industrial chemicals. In 2000, more than 100 countries developed an international agreement to ban or phase out the use of 12 especially hazardous persistent organic pollutants (POPs)—9 of them persistent hydrocarbon pesticides such as DDT and other chemically similar pesticides. The United States has not signed this agreement.
There Are Alternatives to Conventional Pesticides Many scientists believe we should greatly increase the use of biological, ecological, and other alternative methods for controlling pests and diseases that affect crops and human health (Concept 7-4). Here are some of these alternatives: •
Fool the pest. Use a variety of cultivation practices to fake out pests. Examples include rotating the types of crops planted in a field each year and adjusting planting times so that major insect pests either starve or are eaten by their natural predators.
•
Provide homes for pest enemies. Farmers can increase the use of polyculture, which uses plant diversity to reduce losses to pests by providing habitats for the pests’ predators.
•
Implant genetic resistance. Use genetic engineering to speed up the development of pest- and diseaseresistant crop strains. But controversy persists over whether the projected advantages of using GM plants outweigh their projected disadvantages.
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•
Bring in natural enemies. Use biological controls by importing natural predators, parasites, and diseasecausing bacteria and viruses to help regulate pest populations. This approach is nontoxic to other species, minimizes genetic resistance, and is usually less costly than applying pesticides. However, some biological control agents are difficult to mass produce and are often slower acting and more difficult to apply than conventional pesticides are. Sometimes the agents can multiply and become pests themselves.
•
Use insect perfumes. Trace amounts of sex attractants (called pheromones) can lure pests into traps or attract their natural predators into crop fields. Each of these chemicals attracts only one species. They have little chance of causing genetic resistance and are not harmful to nontarget species. However, they are costly and time-consuming to produce.
•
Bring in the hormones. Hormones are chemicals produced by animals to control their developmental processes at different stages of life. Scientists have learned how to identify and use hormones that disrupt an insect’s normal life cycle, thereby preventing it from reaching maturity and reproducing. Insect hormones have some of the same advantages and disadvantages of sex attractants. Also, they take weeks to kill an insect, are often ineffective with large infestations of insects, and sometimes break down before they can act.
•
Use tried-and-true methods to control weeds. Many farmers control weeds by methods such as crop rotation, mechanized cultivators that kill weeds, and the use of cover crops and mulches.
Integrated Pest Management Is a Component of More Sustainable Agriculture Many pest control experts and farmers believe the best way to control crop pests is a carefully designed integrated pest management (IPM) program. In this more sustainable approach, each crop and its pests are evaluated as parts of an ecological system. Then farmers develop a carefully designed control program that uses a combination of cultivation, biological, and chemical tools and techniques applied in a specific and coordinated process (Concept 7-4). The overall aim of IPM is to reduce crop damage to an economically tolerable level. Each year, crops are rotated, or moved from field to field to disrupt pest infestations, and fields are monitored carefully. When an economically damaging level of pests is reached, farmers first use biological methods (natural predators, parasites, and disease organisms) and cultivation controls. They also use large machines to vacuum up harmful bugs. They apply small amounts of insecticides—mostly based on those naturally produced by plants—when
insect or weed populations reach a threshold where the potential cost of pest damage to crops outweighs the cost of applying the pesticide. Broad-spectrum, long-lived pesticides are not used, and different chemicals are used alternately to slow the development of genetic resistance and to avoid killing predators of pest species. In 1986, the Indonesian government banned 57 of the 66 pesticides used on rice and phased out pesticide subsidies over a 2-year period. It also launched a nationwide education program to help farmers switch to IPM. The results were dramatic: Between 1987 and GOOD 1992, pesticide use dropped by 65%, rice produc- NEWS tion rose by 15%, and more than 250,000 farmers were trained in IPM techniques. Sweden and Denmark have used IPM to cut their pesticide use by more than half. Cuba, which uses organic farming to grow its crops, makes extensive use of IPM. In Brazil, IPM has reduced pesticide use on soybeans by as much as 90%. According to a 2003 study by the U.S. National Academy of Sciences, these and other experiences show that a well-designed IPM program can reduce pesticide use and pest control costs by 50–65%, without reducing crop yields and food quality. IPM can also slow the development of genetic resistance, because pests are attacked less often and with lower doses of pesticides. IPM is an important form of pollution prevention that reduces risks to wildlife and human health, and applies the biodiversity principle of sustainability. Despite its promise, IPM—like any other form of pest control—has some disadvantages. It requires expert knowledge about each pest situation and takes more time than does using conventional pesticides. Methods developed for a crop in one area might not apply to areas with even slightly different growing conditions. Initial costs may be higher, although longterm costs typically are lower than those associated with conventional pesticides. Widespread use of IPM is hindered in the United States and a number of other countries by government subsidies for using conventional chemical pesticides, by opposition from pesticide manufacturers, and by a shortage of IPM experts. A growing number of scientists are urging the USDA to use a three-point strategy to promote IPM in the United States. First, add a 2% sales tax on pesticides and use the revenue to fund IPM research and education. Second, set up a federally supported IPM demonstration project on at least one farm in every U.S. county. Third, train USDA field personnel and county farm agents in IPM so they can help farmers use this alternative. Because these measures would reduce its profits, the pesticide industry has vigorously and successfully opposed them. HOW WOULD YOU VOTE?
✓ ■
Should governments heavily subsidize a switch to integrated pest management? Cast your vote online at www.cengage .com/login.
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Several UN agencies and the World Bank have joined together to establish an IPM facility. Its goal is to GOOD promote the use of IPM by disseminating infor- NEWS
7-5
How Can We Improve Food Security and Produce Food More Sustainably?
▲
C O NC EPT 7-5A
▲
C O NC EPT 7-5B
We can improve food security by creating programs to reduce poverty and chronic malnutrition, relying more on locally grown food, and cutting food waste. More sustainable food production will require using resources more efficiently, sharply decreasing the harmful environmental effects of industrialized food production, and eliminating government subsidies that promote such harmful impacts.
Government Subsidies Can Help or Hinder Food Security Governments use two main approaches to influence food production. First, they can control prices by putting a legally mandated upper limit on food prices in order to keep them artificially low. This makes consumers happy but makes it harder for farmers to make a living. Second, they can provide subsidies by giving farmers price supports, tax breaks, and other financial assistance to keep them in business and to encourage them to increase food production. Governments typically use a combination of these two strategies to increase or decrease food production in order to increase food security. However, some analysts argue for phasing out farming and fishing subsidies to help lessen the negative environmental and health effects of these activities. Others argue that any such phase-out should be coupled with increased aid for poor people, who would suffer the most from any increase in food prices. Government programs that reduce poverty by helping the poor to help themselves can improve food security (Concept 7-5A). Some such programs promote family planning, education and jobs (especially for women), and small loans to poor people to help them start businesses or buy land to grow their own food. Some analysts urge governments to establish special programs focused on saving children from poverty. One way to promote such programs is for moredeveloped nations and international lending institutions such as the World Bank to provide technical advice and funding to help poor countries to meet their own food security needs. This would require the governments of those countries to spend more of their funds on helping the rural poor to help themselves. On more local and individual levels, we can all increase food security by decreasing food waste. We
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mation and establishing networks among researchers, farmers, and agricultural extension agents involved in IPM.
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can also support local economies by buying as much locally produced food as possible. This would also help to reduce the environmental impact of shipping food domestically and internationally from producers to consumers (Concept 7-5A).
Farmers Know How to Reduce Soil Erosion Soil conservation involves using a variety of methods to reduce topsoil erosion and restore soil fertility, mostly by keeping the land covered with vegetation. Farmers have used a number of methods to reduce topsoil erosion (Concept 7-5B). For example, terracing is a way to grow food on steep slopes without depleting topsoil. It is done by converting steeply sloped land into a series of broad, nearly level terraces that run across the land’s contours (Figure 7-13a). This retains water for crops at each level and reduces topsoil erosion by controlling runoff. Contour farming involves plowing and planting crops in rows across the slope of the land rather than up and down (Figure 7-13b). Each row acts as a small dam to slow water runoff and to help hold topsoil. Strip cropping (Figure 7-13b) involves planting alternating strips of a row crop (such as corn or cotton) and another crop that completely covers the soil (such as a grass). The cover crop traps topsoil that erodes from the row crop and catches and reduces water runoff. Another way to reduce erosion is to leave crop residues on the land after the crops are harvested. Farmers can also plant cover crops such as alfalfa, clover, or rye immediately after harvest to help protect and hold the topsoil. Alley cropping or agroforestry (Figure 7-13c) is yet another way to slow erosion. One or more crops are planted together in strips or alleys between trees and
Food, Soil, and Pest Management
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(a) Terracing
(b) Contour planting and strip cropping
(c) Alley cropping
(d) Windbreaks
Figure 7-13 Soil conservation methods include (a) terracing, (b) contour planting and strip cropping, (c) alley cropping, and (d) windbreaks (Concept 7-5B).
shrubs that provide shade. This reduces water loss by evaporation and helps retain and slowly release soil moisture—an insurance policy during prolonged drought. The trees also can provide fruit, fuelwood, and trimmings that can be used as mulch for the crops (green manure) and as feed for livestock. Some farmers establish windbreaks, or shelterbelts, of trees around crop fields to reduce wind erosion (Figure 7-13d). They also retain soil moisture, supply wood for fuel, increase crop productivity by 5–10%, and provide habitats for birds, pest-eating and pollinating insects, and other animals. Eliminating or minimizing the plowing and GOOD tilling of topsoil and leaving crop residues on the NEWS ground greatly reduce topsoil erosion. Many farmers in the United States and several other countries practice conservation-tillage farming by using special tillers and planting machines that disturb the topsoil as little as possible while planting crops and leaving behind crop residues that will benefit the topsoil as they decompose. In 2008, farmers used conservation tillage on about 41% of U.S. cropland, helped by the use of herbicides. The USDA estimates that using conservation tillage on 80% of U.S. cropland would reduce topsoil erosion by at least half. Conservation tillage has great potential to
reduce soil erosion and raise crop yields in dry regions in Africa and the Middle East. However, it is not a cureall. It requires costly machinery, works better in some areas than in others, and is more useful for some crops than for others.
We Can Restore Soil Fertility The best way to maintain soil fertility is through topsoil conservation. The next best option is to restore some of the plant nutrients that have been washed, blown, or leached out of topsoil, or removed by repeated crop harvesting. To do this, farmers can use organic fertilizer from plant and animal materials or manufactured inorganic fertilizer produced from various minerals. There are several types of organic fertilizers. One is animal manure: the dung and urine of cattle, horses, poultry, and other farm animals. It improves topsoil structure, adds organic nitrogen and stimulates the growth of beneficial soil bacteria and fungi. Another type, called green manure, consists of freshly cut or growing green vegetation that is plowed into the topsoil to increase the organic matter and humus available to the next crop. A third type is compost, produced when CONCEPTS 7-5A AND 7-5B
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microorganisms in topsoil break down organic matter such as leaves, crop residues, food wastes, paper, and wood in the presence of oxygen. Crops such as corn and cotton can deplete nutrients in the topsoil (especially nitrogen) if they are planted on the same land several years in a row. Crop rotation provides one way to reduce these losses. Farmers plant areas or strips with nutrient-depleting crops one year. The next year, they plant the same areas with legumes, whose root nodules add nitrogen to the soil. This not only helps to restore topsoil nutrients but also reduces erosion by keeping the topsoil covered with vegetation. Many farmers (especially in more-developed countries) rely on manufactured inorganic fertilizers. The active ingredients typically are inorganic compounds that contain nitrogen, phosphorus, and potassium. Other plant nutrients may be present in low or trace amounts. Manufactured inorganic fertilizer use has grown more than ninefold since 1950, and it now accounts for about onefourth of the world’s crop yield. While these fertilizers can replace depleted inorganic nutrients, they do not replace organic matter. To completely restore nutrients to topsoil, both inorganic and organic fertilizers should be used. Furthermore, manufactured fertilizers are water soluble and generally last only about a year, whereas organic fertilizers will not wash out of the soil and will provide nutrients over a longer period of time. We know how to prevent and deal with soil salinization, as summarized in Figure 7-14. Desertification, however, is not an easy problem to solve. We cannot control the timing and locations of prolonged droughts caused by natural factors. But we can reduce population growth, overgrazing, deforestation, and destructive
Solutions Soil Salinization P r even ti o n
forms of planting, irrigation, and mining that have left much land vulnerable to topsoil erosion. We can also work to decrease the human contribution to projected climate change, which is expected to increase severe and prolonged droughts in larger areas of the world during this century. And we can restore land suffering from desertification by planting trees and grasses, establishing windbreaks, and growing trees and crops together (Figure 7-13).
We Can Produce and Consume Meat More Sustainably Raising cattle on rangelands and pastures is less environmentally destructive than raising animals in feedlots, as long as the grasslands are not overgrazed. Grassfed cattle require little or no grain, thus eliminating the harmful environmental effects of using fertilizers and pesticides to grow soybeans and corn, and the energy costs of shipping these grains to feedlots. A more sustainable form of meat production and consumption would involve changes in consumer preferences. This would include a shift from eating less grain-efficient forms of animal protein, such as beef and pork, to eating more grain-efficient forms, such as poultry and herbivorous farmed fish (Figure 7-15). Such a shift is under way.
We Can Practice More Sustainable Aquaculture Figure 7-16 lists some ways to make aquaculture more sustainable and to reduce its harmful environmental effects. The United States is planning to develop openocean aquaculture. In addition, scientists in Florida are eliminating damage to coastal areas by raising shrimp far inland in zero-discharge freshwater ponds. Measures such as these would help to lessen the environmental impact of aquaculture.
Cleanup Flush soil (expensive and wastes water)
Beef cattle
7
Reduce irrigation Pigs
4
Stop growing crops for 2–5 years Chicken Switch to salttolerant crops
Install underground drainage systems (expensive)
Figure 7-14 There are several ways to prevent and clean up soil salinization (Concept 7-5B). Questions: Which two of these solutions do you think are the best? Why?
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Fish (catfish or carp)
2.2
2
Figure 7-15 The efficiency of converting grain into animal protein varies with different types of meat. This bar graph shows the kilograms of grain that each type of animal requires to add one kilogram of body weight. Question: If you eat meat, what changes could you make to your diet that would reduce your environmental impact? (Data from U.S. Department of Agriculture)
Food, Soil, and Pest Management
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Solutions
Solutions
More Sustainable Aquaculture
More Sustainable Agriculture
Protect mangrove forests and estuaries
M or e
L e ss
Improve management of wastes
High-yield polyculture
Soil erosion
Reduce escape of aquaculture species into the wild Raise some species in deeply submerged cages Set up self-sustaining aquaculture systems that combine aquatic plants, fish, and shellfish Certify and label sustainable forms of aquaculture
Soil salinization Organic fertilizers Biological pest control Integrated pest management Efficient irrigation
Figure 7-16 We can make aquaculture more sustainable and reduce its harmful effects. Questions: Which two of these solutions do you think are the best? Why?
Perennial crops Crop rotation Water-efficient crops
However, as with agriculture, making aquaculture more sustainable will require some fundamental changes, one of which is to emphasize raising species that are lower on the food chain—those that feed on plants rather than on other fish. In a more sustainable system, rather than demanding growing quantities of carnivorous fishes, seafood consumers would enjoy a mix of carnivorous, omnivorous, and herbivorous fishes, mollusks, and even seaweeds—a perfect example of following the biodiversity principle of sustainability (see back cover).
We Can Shift to More Sustainable Food Production Sustainability experts agree that shifting to more sustainable food production will have to include phasing in more low-input agricultural systems over the next few decades. One component of this is increased use of organic agriculture, in which crops are grown without the use of synthetic pesticides, manufactured inorganic nitrate and phosphate fertilizers, or genetically engineered seeds, and animals are grown without the use of antibiotics or synthetic growth hormones (see the Case Study that follows). Compared to high-input farming, low-input agriculture produces similar yields with less energy input per unit of yield and lower carbon dioxide emissions. It improves topsoil fertility and reduces topsoil erosion, can often be more profitable for farmers, and can help poor families feed themselves. Figure 7-17 lists the major components of more sustainable food production. Most proponents of more sustainable food production are not opposed to high-yield agriculture. Instead, they see it as vital for protecting the earth’s biodiversity by reducing the need to cultivate new and often marginal land. They call for using environmentally sus-
Soil conservation Subsidies for sustainable farming
Water pollution Aquifer depletion Overgrazing Overfishing Loss of biodiversity and agrobiodiversity Fossil fuel use Greenhouse gas emissions Subsidies for unsustainable farming
Figure 7-17 More-sustainable, low-input agriculture and other forms of more sustainable food production, based mostly on mimicking and working with nature, have a number of major components (Concept 7-5B). Questions: Which two solutions do you think are the best? Why?
tainable forms of both high-yield polyculture and highyield monoculture, with increasing emphasis on using organic methods for producing food. ■ C AS E S T UDY
Organic Agriculture Is On the Rise An important component of more-sustainable food production is organic agriculture. Figure 7-18 (p. 152) compares organic agriculture with conventional, or industrialized, agriculture. Between 2002 and 2008, the global market for certified organically produced food doubled and led to $52 billion in sales in 2009. However, certified organic farming is practiced on less than 1% of the world’s cropland and only 0.6% of U.S. cropland, and organic food accounted for only 3.5% of U.S. food sales in 2008. In Australia and New Zealand, almost one-third of the land under cultivation is used to raise organic crops and beef. In many European countries, 6–18% of the cropland is devoted to organic farming. Cubans have grown most of their food organically for more than four decades. Research conducted for more than 20 years indicates that organic farming has a number of environmental advantages over industrialized farming. On the
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Industr ia l ize d A gr i cu l tu r e Uses synthetic inorganic fertilizers and sewage sludge to supply plant nutrients Makes use of synthetic chemical pesticides Uses conventional and genetically modified seeds
O r g ani c A g r i c ul t ur e Emphasizes prevention of soil erosion and the use of organic fertilizers such as animal manure and compost, but no sewage sludge to help replace lost plant nutrients Employs crop rotation and biological pest control Uses no genetically modified seeds
Depends on nonrenewable fossil fuels (mostly oil and natural gas) Produces significant air and water pollution and greenhouse gases Is globally export-oriented Uses antibiotics and growth hormones to produce meat and meat products
Reduces fossil fuel use and increases use of renewable energy such as solar and wind power for generating electricity Produces less air and water pollution and greenhouse gases Is regionally and locally oriented Uses no antibiotics or growth hormones to produce meat and meat products
Figure 7-18 There are major differences between conventional industrialized agriculture and organic agriculture. In the United States, a label of 100 percent organic means that a product is raised only by organic methods and contains all organic ingredients. Products labeled organic must contain at least 95% organic ingredients. In addition, products labeled made with organic ingredients must contain at least 70% organic ingredients but cannot display the U.S. Department of Agriculture Organic seal on their packages.
other hand, studies have shown that yields for organic crops can be lower than for conventionally raised crops. But farmers make up for this by not having to use or pay for expensive pesticides, herbicides, and synthetic fertilizers and by usually getting higher prices for their crops. Thus, the net economic return per unit of land for organic crop production is often equal to or higher than that from conventional crop production. Another drawback is that most organically grown food costs 10–100% more than conventionally produced food (depending on specific items), primarily because organic farming is more labor intensive. However, several analysts argue that if food prices included the estimated costs of the harmful environmental and health impacts of industrialized food production, then organic food would be cheaper than food produced by industrialized agriculture.
We Can Help Farmers to Make the Transition to Sustainable Food Production Analysts suggest five major strategies to help producers and consumers make the transition to moresustainable food production. First, greatly increase research on more-sustainable forms of food production, including organic farming, and on improving human
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nutrition. Second, establish education and training programs in more-sustainable food production for students, producers, and government agricultural officials. Third, set up an international fund to give producers in poor countries access to forms of more-sustainable food production. Fourth, replace government subsidies for environmentally harmful forms of fishing and farming with subsidies that encourage more-sustainable food production. Fifth, mount a massive program to educate consumers about the true costs of the food they buy. Phasing in more-sustainable food production involves applying the three principles of sustainability (see back cover). In agriculture, this means relying more on solar energy and less on oil; sustaining nutrient cycling through soil conservation and by returning crop residues and animal wastes to the soil; and helping to sustain natural and agricultural biodiversity by relying on a greater variety of crop and animal strains. The goal is to feed the world’s people while sustaining and restoring the earth’s natural capital and living off the natural income it provides. This will not be easy, but it can be done. Figure 7-19 lists ways in which you can promote more-sustainable food production. Here are this chapter’s three big ideas: ■ About 1 billion people have health problems because they do not get enough to eat and 1.1 billion people face health problems from eating too much.
Food, Soil, and Pest Management
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■ Modern industrialized agriculture has a greater harmful impact on the environment than any other human activity. ■ More-sustainable forms of food production will greatly reduce the harmful environmental impacts of current systems while increasing food security.
Figure 7-19 Individuals matter: There are a number of ways in which you can promote more-sustainable food production (Concept 7-5B). Questions: Which three of these actions do you think are the most important? Why?
What Can You Do? More Sustainable Food Production ■
Eat less meat, no meat, or organically certified meat
■
Use organic farming to grow some of your food
■
Buy certified organic food
■
Eat locally grown food
■
Cut food waste and compost what you can
■
Choose sustainably produced herbivorous fish
While there are alternatives to oil, there are no alternatives to food. MICHAEL POLLAN
REVIEW 1. Review the Key Questions and Concepts for the chapter on p. 131. Define food security and food insecurity. What is the root cause of food insecurity? Distinguish between chronic undernutrition (hunger) and chronic malnutrition and describe their harmful effects. Describe the effects of diets deficient in vitamin A, iron, and iodine. What is overnutrition and what are its harmful effects? 2. What three systems supply most of the world’s food? Distinguish among industrialized (high-input) agriculture, plantation agriculture, traditional subsistence agriculture, traditional intensive agriculture, polyculture, and slash-and-burn agriculture. Define soil and describe its formation and the major layers in mature soils. What is a green revolution? 3. Distinguish between artificial selection and genetic engineering. What are genetically modified organisms (GMOs)? Describe some of the current efforts involving genetic engineering. 4. Describe industrialized meat production. Define and distinguish between fisheries and aquaculture. Describe the use of energy in industrialized agriculture. 5. What are the major harmful environmental impacts of food production? What is soil erosion and what are its two major harmful environmental effects? What is desertification and what are its harmful environmental effects? Distinguish between salinization and waterlogging of soil and describe their harmful environmental effects. Explain how food production systems reduce biodiversity. 6. Describe the advantages and disadvantages of genetically engineered foods. What factors can limit green revolu-
tions? Describe the advantages and disadvantages of industrialized meat production. Describe the advantages and disadvantages of aquaculture. 7. What is a pest? Define pesticide and the four major types of pesticides. Summarize Rachel Carson’s work in the area of pesticides. Give two examples of commonly used pesticides. Describe trends in pesticide use since 1950. Describe the advantages and disadvantages of modern pesticides. What are five alternatives to conventional pesticides? Define integrated pest management (IPM) and discuss its advantages. 8. Describe two ways in which governments influence food production. What is soil conservation? Describe five ways to reduce soil erosion. Distinguish among the uses of organic fertilizer, manufactured inorganic fertilizer, animal manure, green manure, and compost as ways to help restore soil fertility. Describe ways to prevent and clean up soil salinization. 9. What are two components of a more-sustainable meat production and consumption system? How can we make aquaculture more sustainable? Define organic agriculture and describe its advantages over conventional agriculture as well as its disadvantages. 10. What are four ways to help producers in making food production more sustainable? What can individuals do to promote more-sustainable food production? How does making the transition to more-sustainable food production involve the three principles of sustainability? What are this chapter’s three big ideas?
Note: Key terms are in bold type.
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CRITICAL THINKING 1. What are the three most important actions you would take to reduce chronic hunger and malnutrition (a) in the country where you live and (b) in the world? 2. Explain why you support or oppose greatly increased use of (a) genetically modified food and (b) polyculture. 3. Suppose you live near a coastal area and a company wants to use a fairly large area of coastal marshland for an aquaculture operation. If you were an elected local official, would you support or oppose such a project? Explain. What safeguards or regulations would you impose on the operation? 4. Explain how widespread use of a pesticide can (a) increase the damage done by a particular pest and (b) create new pest organisms.
5. According to physicist Albert Einstein, “Nothing will benefit human health and increase chances of survival of life on Earth as much as the evolution to a vegetarian diet.” Do you agree? Why or why not? Are you willing to eat less meat or no meat? Explain. 6. Congratulations! You are in charge of the world. List the three most important features of your (a) agricultural policy, (b) policy to reduce soil erosion, (c) policy for moresustainable harvesting and farming of fish and shellfish, and (d) global pest management strategy. 7. List two questions that you would like to have answered as a result of reading this chapter.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 7 for many study aids and ideas for further
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reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
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8
Water Resources and Water Pollution
Key Questions and Concepts Will we have enough usable water?
8-1
We are using available freshwater unsustainably by wasting it, polluting it, and charging too little for this irreplaceable natural resource.
CONCEPT 8-1A
C O N C E P T 8 - 1 B One of every six people does not have sufficient access to clean water and this situation will almost certainly get worse.
8-6 What are the major water pollution problems in streams and lakes? C O N C E P T 8 - 6 Addition of pollutants and excessive nutrients to streams and lakes can disrupt these ecosystems, and prevention of such pollution is more effective and less costly than cleaning it up.
What are the major pollution problems affecting groundwater and other drinking water sources?
8-7
How can we increase water supplies?
8-2
Pumping groundwater, building dams, transferring water, and desalination can all increase water supplies, but these strategies all create environmental problems.
CONCEPT 8-2
How can we use water more sustainably?
8-3
We can use water more sustainably by cutting water waste, raising water prices, slowing population growth, and protecting aquifers, forests, and other ecosystems that store and release water.
Chemicals used in agriculture, industry, transportation, and homes can spill and leak into groundwater and make it undrinkable; while we can purify polluted water, protecting it through pollution prevention is the least expensive and most effective strategy.
CONCEPT 8-7
CONCEPT 8-3
8-8 What are the major water pollution problems affecting oceans?
How can we reduce the threat of flooding?
8-4
C O N C E P T 8 - 4 We can lessen the threat of flooding by protecting more wetlands and natural vegetation in watersheds, and by not building in areas subject to frequent flooding.
What are the causes and effects of water pollution?
8-5
Water pollution, primarily caused by agricultural activities, industrial facilities, and mining, and worsened by population growth and resource use, causes illness and death in humans and other species, and disrupts ecosystems.
CONCEPT 8-5
C O N C E P T 8 - 8 The great majority of ocean pollution originates on land and includes oil and other toxic chemicals and solid waste, which threaten fish and wildlife, and disrupt marine ecosystems; the key to protecting oceans is to reduce the flow of pollutants into coastal waters.
8-9 How can we best deal with water pollution? C O N C E P T 8 - 9 Reducing water pollution requires that we prevent it, work with nature to treat sewage, cut resource use and waste, reduce poverty, and slow population growth.
Our liquid planet glows like a soft blue sapphire in the hard-edged darkness of space. There is nothing else like it in the solar system. It is because of water. JOHN TODD
Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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8-1
Will We Have Enough Usable Water?
▲
C O NC EPT 8-1A We are using available freshwater unsustainably by wasting it, polluting it, and charging too little for this irreplaceable natural resource.
▲
C O NC EPT 8-1B One of every six people does not have sufficient access to clean water and this situation will almost certainly get worse.
Freshwater Is An Irreplaceable Resource That We Are Managing Poorly We live on a water planet with a precious layer of water—most of it saltwater—covering about 71% of the earth’s surface. Look in the mirror. What you see is about 60% water, most of it inside your cells. You could survive for several weeks without food, but for only a few days without water. In addition, it takes huge amounts of water to supply us with food and with most of the other things that we use to meet our daily needs and wants. Water also plays a key role in sculpting the earth’s surface, moderating the earth’s climates, and removing and diluting pollutants and wastes that we produce. Despite its importance, water is one of our most poorly managed resources. We waste it and pollute it. We also charge too little for making it available. This encourages still greater waste and pollution of this resource, for which we have no substitute (Concept 8-1A). Only a tiny fraction of the planet’s enormous water supply—about 0.024%—is readily available to us as liquid freshwater in accessible groundwater deposits and in lakes, rivers, and streams. The rest is in the salty oceans (about 97% of the earth’s volume of liquid water), in frozen polar ice caps and glaciers, or in inaccessible locations deep underground. Fortunately, the world’s freshwater supply is continually collected, purified, recycled, and distributed in the earth’s hydrologic cycle (see Figure 2-19, p. 41). This irreplaceable water recycling and purification system works well, unless we overload it with pollutants or withdraw water from underground and surface water supplies faster than it is replenished. We also interfere with this cycle when we destroy wetlands and cut down forests, which store and slowly release water, and when we add to atmospheric warming that leads to projected climate change, which alters the cycle’s rate and distribution patterns. In some parts of the world, we are doing all of these things. On a global basis we have plenty of freshwater, but differences in average annual precipitation and economic resources divide the world’s continents, countries, and people into water haves and have-nots. For example, Canada, with only 0.5% of the world’s population, has 20% of the world’s liquid freshwater, while China, with 19% of the population, has only 7% of the world’s freshwater supply.
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Groundwater and Surface Water Are Critical Resources Some precipitation infiltrates, or seeps into, the ground and percolates downward through spaces in soil, gravel, and rock until an impenetrable layer of bedrock stops it (Figure 8-1). The water in these spaces is called groundwater—one of our most important sources of freshwater. The spaces in soil and rock close to the earth’s surface hold little moisture. However, below a certain depth, in the zone of saturation, these spaces are completely filled with water. The top of this groundwater zone is the water table. It falls in dry weather, or when we remove groundwater faster than nature can replenish it, and it rises in wet weather. Deeper down are geological layers called aquifers, underground caverns and porous layers of sand, gravel, or rock through which groundwater flows. Mostly because of gravity, groundwater normally moves from points of high elevation and pressure to points of lower elevation and pressure. Some caverns have rivers of groundwater flowing through them. But the porous layers of sand, gravel, or rock in most aquifers are like large, elongated sponges through which groundwater seeps— typically moving only a meter or so (about 3 feet) per year and rarely more than 0.3 meter (1 foot) per day. Watertight layers of rock or clay below such aquifers keep the water from escaping deeper into the earth. Most aquifers are replenished naturally by precipitation that percolates downward through soil and rock, a process called natural recharge. Others are recharged from the side by lateral recharge from nearby lakes, rivers, and streams. Most aquifers recharge extremely slowly. Nonrenewable aquifers get very little, if any, recharge. They are found deep underground and were formed tens of thousands of years ago. Withdrawing water from these aquifers amounts to mining a nonrenewable resource. Another of our most important resources is surface water, the freshwater from precipitation and melted snow that flows across the earth’s land surface and into lakes, wetlands, streams, rivers, estuaries, and ultimately the oceans. Precipitation that does not infiltrate the ground or return to the atmosphere by evaporation is called surface runoff. The land from which surface water drains into a particular river, lake, wetland, or other body of water is called its watershed, or drainage basin.
Water Resources and Water Pollution
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Unconfined Aquifer Recharge Area Evaporation and transpiration
Precipitation
Confined Recharge Area
Evaporation
Runoff
Flowing artesian well
Infiltration
Well requiring a pump
Stream
Water table
Lake Infiltration Unconfined aquifer
Less permeable material such as clay
Confined aquifer
Confining impermeable rock layer Figure 8-1 Natural capital: This diagram shows a groundwater system. An unconfined aquifer is an aquifer with a permeable water table. A confined aquifer is bounded above and below by less permeable beds of rock where the water is confined under pressure. Some aquifers are replenished by precipitation; others are not.
We Use Much of the World’s Reliable Runoff According to hydrologists (scientists who study the nature, distribution, and movement of water on the earth), two-thirds of the annual surface runoff into rivers and streams is lost in seasonal floods and is not available for human use. The remaining one-third is reliable surface runoff, which we can generally count on as a source of freshwater from year to year. During the last century, the human population tripled, global water withdrawals increased sevenfold, and per capita withdrawals quadrupled. As a result, we now withdraw about 34% of the world’s reliable runoff, on average. Withdrawal rates already severely strain the reliable runoff in some areas (see the Case Study that follows). For example, in the arid American Southwest, up to 70% of the reliable runoff is withdrawn for human purposes. Some water experts project that because of a combination of population growth, increased water use per person, and failure to cut water waste, we may be withdrawing up to 90% of the reliable runoff by 2025. Worldwide, we use 70% of the water we withdraw each year from rivers, lakes, and aquifers to irrigate
cropland and raise livestock. Industry uses another 20% annually, and cities and residences use the remaining 10%. Affluent lifestyles require large amounts of water (Science Focus, p. 159), much of it wasted. ■ C AS E S T UDY
Freshwater Resources in the United States The United States has more than enough renewable freshwater. But it is unevenly distributed and much of it is contaminated by agricultural and industrial practices. The eastern states usually have ample precipitation, whereas many western and southwestern states have little (Figure 8-2, top, p. 158). In the eastern United States, most water is used for power plant cooling and manufacturing. In many parts of this region, the most serious water problems are flooding and occasional water shortages as a result of pollution. In the arid and semiarid areas of the western half of the country (Figure 8-2, bottom), irrigation counts for as much as 85% of water use. The major water problem is a shortage of runoff caused by low CONCEPTS 8-1A AND 8-1B
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Average annual precipitation (centimeters) Less than 41 41–81
81–122 More than 122
Washington Montana
Oregon Idaho
Wyoming
North Dakota South Dakota Nebraska
Nevada Utah
Colorado
California
Kansas Oklahoma
Arizona
New Mexico
Texas
Highly likely conflict potential Substantial conflict potential Moderate conflict potential Unmet rural water needs
Acute shortage
Figure 8-3 This map shows water hotspots in 17 western states that, by 2025, could face intense conflicts over scarce water needed for urban growth, irrigation, recreation, and wildlife. Some analysts suggest that this is a map of places not to live in the foreseeable future. Question: Which of these areas include metropolitan regions (see Figure 8-2, bottom)? (Data from U.S. Department of the Interior)
Shortage Adequate supply Metropolitan regions with population greater than 1 million Figure 8-2 The top map shows the average annual precipitation and major rivers in the continental United States. The bottom map shows water-deficit regions in the continental United States and their proximity to metropolitan areas having populations greater than 1 million (darkest-shaded areas). Question: Why do you think some areas with moderate precipitation still suffer from water shortages? (Data from U.S. Water Resources Council and U.S. Geological Survey)
precipitation (Figure 8-2, top), high evaporation, and recurring prolonged dry periods. According to the U.S. Geological Survey (USGS), about one-third of the freshwater withdrawn in the United States comes from groundwater sources, and the other two-thirds come from rivers, lakes, and reservoirs. Water tables in many water-short areas, especially in the arid and semiarid western half of the lower 48 states, are dropping quickly as farmers and rapidly growing urban areas deplete many aquifers faster than they can be recharged. In 2007, the USGS projected that areas in at least 36 states are likely to face water shortages by 2013. Figure 8-3 shows some of the worst of these water hotspots. In these areas, competition for scarce water to support growing urban areas, irrigation, recreation, and wildlife could trigger intense political and legal conflicts between
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states and between rural and urban areas within states during the next 20 years. According to a 2009 study by the USCG, between 1975 and 2005, the amount of water used in the GOOD United States has remained fairly stable despite NEWS a 30% rise in population and a significant increase in average resource use per person. The main reasons for this are increased use of more efficient irrigation systems and reduced use of inefficient cooling systems in many electric power plants. This is an encouraging trend but the United States still wastes large amounts of water.
Water Shortages Will Grow Several major factors contribute to water scarcity, including a dry climate and drought: a prolonged period in which precipitation is at least 70% lower and evaporation is higher than normal. Also, in some places where water is scarce, there are too many people drawing on the reliable supply of water, and often there are not enough funds available for drilling deep wells or building dams, storage reservoirs, and water distribution systems. Between 1979 and 2004, the area of the earth experiencing severe or extreme drought tripled. Currently, about 30% of the earth’s land area—a total area roughly equal to the size of Asia—experiences severe drought.
Water Resources and Water Pollution
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S C I E NC E FO C U S Water Footprints and Virtual Water
E
ach of us has a water footprint, which is a rough measure of the volume of water that we use directly and indirectly to keep us alive and to support our lifestyles. According to the American Waterworks Association, each day the average American directly uses about 260 liters (69 gallons) of water—enough water to fill about 1.7 typical bathtubs of water (each containing about 150 liters or 40 gallons of water). In the United States, this water is used mostly for flushing toilets (27%), washing clothes (22%), taking showers (17%), and running faucets (16%), or is wasted by water leaks (14%). We use much larger amounts of water indirectly, because water is used to provide us with food and other consumer products. Producing and delivering a typical hamburger, for example, takes about 2,400 liters (630 gallons) of water—most of which is used to grow the grain that is fed to cattle. This water would fill about 16 bathtubs. Similarly, according to the Coca Cola Company, it takes about 500 liters (132 gallons)—roughly 3 bathtubsful of water—to make a 2-liter (0.5-gallon) bottle of soda, if you include the water used to grow and harvest ingredients such as sugar cane. Water that is not directly consumed but is used to produce food and other products is called virtual water, and it makes up a large part of our water footprints, especially in more-developed nations. Figure 8-A shows one way to measure the amounts of virtual water used for producing and delivering products. These values can vary depending on how much of the supply chain is included, but they give us a rough estimate of the size of our water footprints.
1 tub = 151 liters (40 gallons)
Global warming is expected to increase this browning of the earth in various parts of the world. In 2007, climate researcher David Rind and his colleagues at the NASA Goddard Institute for Space Studies projected that by 2059, as much as 45% of the earth’s land surface could experience a “once in a century” extreme drought. Figure 8-4 (p. 160) shows the current degree of stress faced by the world’s major river systems, based on a comparison of the amount of surface freshwater available with the amount used per person. More than 30 countries—most of them in the Middle East and Africa—now face water scarcity. By 2050, some 60 countries, many of them in Asia, are likely to be suffering from water stress. In 2006, the Chinese government reported that two-thirds of Chinese cities faced water
= 1 tub
Figure 8-A Producing and delivering a single one of each of the products shown here requires the equivalent of at least one and usually many bathtubsful full of water, called virtual water. The average amount of water used to raise a single steer during its typical 3-year life by an industrial beef producer would fill more than 20,000 bathtubs. This includes water used to provide food and drinking water for the steer and to clean up its wastes. (Data from UNESCO-IHE Institute for Water Education, UN Food and Agriculture Organization, World Water Council, and Coca Cola Company) [Photos from Shutterstock; Credits (top to bottom): Kirsty Pargeter, Aleksandra Nadeina, Alexander Kallina, Kelpfish, Wolfgang Amri, Skip Odonnell, Eky Chan, Rafal Olechowski]
= 4 tubs
= 16 tubs
= 17 tubs
= 72 tubs
= 2,600 tubs
= 16,600 tubs
shortages. Rapid urbanization and economic growth are expected to make this situation worse. In 2009, the United Nations reported that about 1 billion people—one of every seven in the world—lacked regular access to enough clean water for drinking, cooking, and washing. The report also noted that by 2025, at least 3 billion of the world’s projected 7.9 billion people are likely to lack access to clean water (Concept 8-1B). One likely result of such shortages is intense conflicts within and between countries—especially in the watershort Middle East (see the Case Study that follows) and Asia—over dwindling shared water resources. This helps to explain why many analysts view the likelihood of increasing water shortages in many parts of the world as one of the world’s most serious problems. CONCEPTS 8-1A AND 8-1B
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Asia
Europe North America
Africa
South America
Australia
Stress High
None
Figure 8-4 Natural capital degradation: The world’s major river basins differ in their degree of water-scarcity stress, based on a comparison of the amount of water available with the amount used by humans. Questions: If you live in a water-stressed area, what signs of stress have you noticed? In what ways, if any, has it affected your life? (Data from World Commission on Water Use in the 21st Century)
■ CAS E STUDY
Water Conflicts in the Middle East: A Preview of the Future?
IA
EN
M
AR
Eu
is
SYRIA
r Tig
Jordan
LEBANON WEST BANK GAZA
ph
ra
te
IRAN
s
IRAQ JORDAN
Pe rs ia
KUWAIT
ISRAEL
n G
il
e
f
BAHRAIN QATAR
A S E
N
ul
EGYPT
D R E
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MEDITERRANEAN SEA
le
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TURKEY
Ni
Many countries in the Middle East face water shortages and rising tensions over water sources they must share. Most water in this dry region comes from three river basins: the Nile, the Jordan, and the Tigris–Euphrates (Figure 8-5). Africa’s Nile River flows through seven countries, each of which draws on it for irrigation and drinking, water and flushes mostly untreated sewage and other effluents into it. Three countries—Ethiopia, Sudan, and Egypt—use most of the water that flows in the Nile. Egypt, which gets more than 97% of its freshwater from the river, is last in line. To meet the water and food needs of their rapidly growing populations, Ethiopia and Sudan plan to divert more water from the Nile. Such upstream diversions would reduce the amount of water available to Egypt, which cannot exist without irrigation water from the river. Egypt faces conflicts with Sudan and Ethiopia over water, which could be lessened if these countries cut their rapid population growth or reduce their waste of irrigation water. Other options are to import more grain to reduce the need for irrigation water, work out watersharing agreements, or suffer the harsh human and economic consequences of hydrological poverty.
The Jordan River basin is by far the most watershort region, and there is fierce competition for its water among Jordan, Syria, Palestine (Gaza and the West Bank), and Israel. Syria, which is projected to nearly double its population between 2008 and 2050, plans
SAUDI ARABIA
UNITED ARAB EMIRATES
OMAN
SUDAN
YEMEN
DJIBOUTI ETHIOPIA
SOMALIA
Figure 8-5 Many countries in the Middle East, which has one of the world’s highest population growth rates, face water shortages and conflicts over access to water because they share water from only three major river basins.
Water Resources and Water Pollution
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to build dams and withdraw more water from the Jordan River, decreasing the downstream water supply for Jordan and Israel. If Syria goes through with its plans, Israel warns that it may destroy the largest dam. In contrast, Israel has cooperated with Jordan and Palestine over their shared water resources. Turkey, located at the headwaters of the Tigris and Euphrates Rivers, controls water flowing downstream through Syria and Iraq and into the Persian Gulf. Turkey is building 24 dams along the upper Tigris and Euphrates to generate electricity and irrigate a large area of land.
8-2
If completed, these dams will reduce the flow of water downstream to Syria and Iraq by as much as 35% in normal years and by much more in dry years. Syria also plans to build a large dam along the Euphrates to divert water arriving from Turkey. This will leave little water for Iraq and could lead to a water war between Iraq and Syria. Resolving these water distribution problems will require negotiating agreements to share water supplies, slowing population growth, cutting water waste, raising water prices to encourage irrigation efficiency, and increasing grain imports to reduce water needs.
How Can We Increase Water Supplies?
▲
Pumping groundwater, building dams, transferring water, and desalination can all increase water supplies, but these strategies all create environmental problems.
CONC EPT 8-2
Groundwater Is Being Withdrawn Faster Than It Is Replenished in Some Areas
Water tables are falling in many areas of the world because the rate of pumping water from nearly all of the world’s aquifers (mostly to irrigate crops) is greater than the rate of natural recharge from rainfall and snowmelt (Concept 8-2). The world’s three largest grain Most aquifers are renewable resources unless the producers—China, India, and the United States—as well groundwater they contain becomes contaminated or is as Mexico, Saudi Arabia, Iran, Yemen, Israel, and Pakiremoved faster than it is replenished by rainfall, as is stan are overpumping many of their aquifers. occurring in many parts of the world. Aquifers provide In the United States, groundwater is being withdrinking water for nearly half of the world’s people. drawn from aquifers, on average, four times faster than In the United States, aquifers supply almost all of the it is replenished, according to the USGS. Figure 8-7 drinking water in rural areas, one-fifth of that in urban (p. 162) shows the areas of greatest aquifer depletion. areas, and 37% of the country’s irrigation water. RelyOne of the most serious overdrafts of groundwater is ing more on groundwater has advantages and disadvanin the lower half of the Ogallala, the world’s largest tages (Figure 8-6). known aquifer, which lies under eight Midwestern states from southern South Dakota to Texas (most of the large darker-shaded area near the center of the map). Overpumping aquifers has several harmful effects. It not only limits future Withdrawing Groundwater food production, but in some cases it also allows the sand and rock in aquifers to A dv a nta g e s D isad v antag e s collapse. This causes the land above the Useful for drinking and Aquifer depletion from aquifer to subside or sink, a phenomenon irrigation overpumping known as land subsidence.
Trade-Offs
Exists almost everywhere
Sinking of land (subsidence) from overpumping
Renewable if not overpumped or contaminated
Pollution of aquifers lasts decades or centuries
Cheaper to extract than most surface waters
Deeper wells are nonrenewable
Figure 8-6 Withdrawing groundwater from aquifers has advantages and disadvantages. Questions: Which two advantages and which two disadvantages do you think are the most important? Why?
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Groundwater Overdrafts: High Moderate Minor or none Figure 8-7 Natural capital degradation: This map shows areas of greatest aquifer depletion from groundwater overdraft in the continental United States. Aquifer depletion is also high in Hawaii and Puerto Rico (not shown on map). Questions: Do you depend on any of these aquifers for your drinking water? If so, what is the level of severity of overdraft where you live? (Data from U.S. Water Resources Council and U.S. Geological Survey)
Groundwater overdrafts near coastal areas can pull saltwater into freshwater aquifers. The resulting contaminated groundwater is undrinkable and unusable for irrigation. This problem is especially serious in heavily populated coastal areas of the U.S. states of Florida, California, South Carolina, Georgia, New Jersey, and Texas, as well as in coastal areas of Turkey, the Philippines, and Thailand. If sea levels rise due to climate change as projected, this problem will grow worse. Figure 8-8 lists ways to prevent or slow the problem of aquifer depletion by using this largely renewable resource more sustainably.
Solutions Groundwater Depletion P re v e nt ion
Cont r ol
Waste less water
Raise price of water to discourage waste
Subsidize water conservation
Tax water pumped from wells near surface waters
Limit number of wells
Set and enforce minimum stream flow levels
Do not grow water-intensive crops in dry areas
Divert surface water in wet years to recharge aquifers
With global water shortages looming, scientists are evaluating deep aquifers as future water sources. Preliminary results suggest that some of these aquifers hold enough water to support billions of people for centuries. And the quality of water in these aquifers may be much higher than the quality of the water in most rivers and lakes. There are three major concerns about tapping these ancient deposits of water. First, they are nonrenewable and cannot be replenished on a human timescale. Second, little is known about the geological and ecological impacts or of the costs of pumping water from deep aquifers. Third, some deep aquifers flow beneath more than one country and with no international treaties to govern rights to them, water wars could break out.
Large Dams and Reservoirs Have Advantages and Disadvantages The main purposes of a dam-and-reservoir system are to capture and store runoff, and release it as needed in order to control floods, generate electricity, and supply water for irrigation and for towns and cities. Reservoirs also provide recreational activities such as swimming, fishing, and boating. Large dams and reservoirs have both benefits and drawbacks (Figure 8-9). More than 45,000 large dams in the world (22,000 of them in China) have increased the annual reliable runoff available for human use by nearly one-third. As a result, reservoirs now hold 3 to 6 times more water than the total amount flowing in all of the world’s natural rivers. These dams and reservoirs have helped us to reduce flooding and grow crops in arid areas, and hydroelectric dams produce 20% of the world’s electricity. On the down side, this engineering approach to river management has displaced 40–80 million people from their homes, flooded an area of mostly productive land roughly equivalent to the area of the U.S. state of California, and impaired some of the important ecological services that rivers provide (Figure 8-10). A 2007 study by the World Wildlife Fund (WWF) estimated that about one out of five of the world’s freshwater fish and plant species are either extinct or endangered, primarily because dams and water withdrawals have sharply decreased the flow of many rivers. The study also found that, because of dams, excessive water withdrawals and, in some areas, prolonged severe drought, only 21 of the planet’s 177 longest rivers run freely from their sources to the sea. Projected climate change will worsen this situation in areas that become hotter and receive less precipitation. HOW WOULD YOU VOTE?
Figure 8-8 There are a number of ways to prevent or slow groundwater depletion by using water more sustainably. Questions: Which two of these solutions do you think are the best ones? Why?
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✓ ■
Do the advantages of large dams outweigh their disadvantages? Cast your vote online at www.cengage.com/login.
Water Resources and Water Pollution
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Provides irrigation water above and below dam
Flooded land destroys forests or cropland and displaces people
Large losses of water through evaporation Provides water for drinking Deprives downstream cropland and estuaries of nutrient-rich silt
Reservoir useful for recreation and fishing
Risk of failure and devastating downstream flooding
Can produce cheap electricity (hydropower)
Reduces downstream flooding of cities and farms
Disrpupts migration and spawning of some fish Powerlines
Reservoir Dam Powerhouse
Intake
Turbine
Figure 8-9 Trade-offs: Large dams and reservoirs have advantages (left) and disadvantages (right) (Concept 8-2). The world’s 45,000 large dams (15 meters (49 feet) or higher) capture and store about 14% of the world’s surface runoff, provide water for almost half of all irrigated cropland, and supply more than half the electricity used in 65 countries. The United States has more than 70,000 large and small dams, capable of capturing and storing half of the country’s entire river flow. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Natural Capital Ecological Services of Rivers Deliver nutrients to sea to help sustain coastal fisheries Deposit silt that maintains deltas Purify water Renew and renourish wetlands Provide habitats for wildlife
Figure 8-10 The important ecological services provided by rivers are shown here. Currently, the services are given little or no monetary value when the costs and benefits of dam-and-reservoir projects are assessed. Questions: Which two of these services do you believe are the most important? Why? Which two of these services do you think are most likely to decline? Why?
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Water Transfer Systems Can Be Wasteful and Environmentally Harmful Tunnels, aqueducts, and underground pipes can transfer stream runoff collected by dams and reservoirs from water-rich areas to water-poor areas, but they also create environmental problems (see the Case Study that follows). One of the world’s largest water transfer projects is the combination of the California Water Project and the Central Arizona Project (Figure 8-11). It uses a maze of giant dams, pumps, and lined canals, or aqueducts, to transport water from water-rich northern California to water-poor, heavily populated cities and agricultural regions of southern California and Arizona. Without such water transfers, these areas would be mostly desert. For decades, northern and southern Californians have feuded over how the state’s water should be allocated under this project. Southern Californians want more water from the north to grow more crops and to support Los Angeles, San Diego, and other growing urban areas. Agriculture consumes three-fourths of the water withdrawn in California, much of it used inefficiently for growing water-thirsty crops such as rice and alfalfa in desert-like conditions. Northern Californians counter that sending more water south degrades the Sacramento River, threatens fisheries, and reduces the flushing action that helps clean San Francisco Bay of pollutants. They also argue that much of the water sent south is wasted. They point
CALIFORNIA NEVADA Shasta Lake Oroville Dam and Reservoir
Sacramento River
Feather River
North Bay Aqueduct
Lake Tahoe
Sacramento
SIERRA MOUNTAIN RANGE
San Francisco in qu Joa San
Hoover Dam and Reservoir (Lake Mead)
Fresno
lley Va
South Bay Aqueduct San Luis Dam and Reservoir
UTAH
California Aqueduct
Colorado River Aqueduct
Santa Barbara
Colorado River
Los Angeles Aqueduct
Los Angeles San Diego
Salton Sea
ARIZONA Central Arizona Project Phoenix
Tucson
MEXICO Figure 8-11 The California Water Project and the Central Arizona Project transfer huge volumes of water from one watershed to another. Arrows show the general direction of water flow. Questions: What effects might these systems have on different areas on this map? How might it affect areas from which the water is taken?
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to studies showing that making irrigation just 10% more efficient would provide all the water necessary for domestic and industrial uses in southern California. According to a 2002 study, projected climate change will make matters worse, sharply reducing the availability of water in California and other water-short states. Some analysts project that during this century, many people living in arid southern California cities, as well as farmers in this area, may have to move elsewhere because of water shortages. ■ C AS E S T UDY
The Aral Sea Disaster The shrinking of the Aral Sea in the former Soviet Union is the result of a large-scale water transfer project in an area with the driest climate in central Asia. Since 1960, enormous amounts of irrigation water have been diverted from the two rivers that supply water to the sea to create one of the world’s largest irrigated areas, mostly for raising cotton and rice. The irrigation canal, the world’s longest, stretches more than 1,300 kilometers (800 miles). This large-scale water diversion project, coupled with drought and high evaporation rates due to the area’s hot and dry climate, has caused a regional ecological and economic disaster. Since 1961, the sea’s salinity has risen sevenfold and the average level of its water has dropped by an amount roughly equal to the height of a six-story building. The Southern Aral Sea has lost 90% of its volume of water and has split into two major parts, separated by land. Water withdrawal for agriculture has reduced the two rivers feeding the sea to mere trickles. About 85% of the area’s wetlands have been eliminated and about half the local bird and mammal species have disappeared. A huge area of the former Southern Aral Sea’s bottom is now a human-made desert covered with glistening white salt. The sea’s greatly increased salt concentration—3 times saltier than ocean water— has caused the presumed local extinction of 26 of the area’s 32 native fish species. This has devastated the area’s fishing industry, which once provided work for more than 60,000 people. Fishing villages and boats once located on the sea’s coastline now sit abandoned in a salt desert. Winds pick up the sand and salty dust and blow it onto fields as far as 500 kilometers (310 miles) away. As the salt spreads, it pollutes water and kills wildlife, crops, and other vegetation. Aral Sea dust settling on glaciers in the Himalayas is causing them to melt at a faster than normal rate. Shrinkage of the Aral Sea has also altered the area’s climate. The once-huge sea acted as a thermal buffer that moderated the heat of summer and the extreme cold of winter. Now there is less rain, summers are hotter and drier, winters are colder, and the growing season is shorter. The combination of such climate change and severe salinization has reduced crop yields by 20–50% on almost one-third of the area’s cropland.
Water Resources and Water Pollution
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To raise yields, farmers have used more herbicides, insecticides, and fertilizers, which have percolated downward and accumulated to dangerous levels in the groundwater—the source of most of the region’s drinking water. Many of the 45 million people living in the Aral Sea’s watershed have experienced increasing health problems—including anemia, respiratory illnesses, liver and kidney disease, eye problems, and various cancers—from a combination of toxic dust, salt, and contaminated water. Since 1999, the United Nations and the World Bank have spent about $600 million to purify drinking GOOD water and upgrade irrigation and drainage sys- NEWS tems in the area. This has improved irrigation efficiency and helped flush salts from croplands. The five countries surrounding the sea and its two feeder rivers have worked to improve irrigation efficiency and to partially replace water-thirsty crops with other crops that require less irrigation water. Since 2005, the level of the northern sea has risen by 4 meters (13 feet) and its surface area has increased by 13%. However, the much larger southern sea is still shrinking. By late 2009, its eastern lobe was essentially gone, and the European Space Agency projects that the rest of the Southern Aral Sea could dry up completely by 2020.
Removing Salt from Seawater Is Costly, Kills Marine Organisms, and Produces Briny Wastewater Desalination involves removing dissolved salts from ocean water or from brackish (slightly salty) water in aquifers or lakes. It is another way to increase supplies
8-3
of freshwater, but it also comes with environmental costs (Concept 8-2). One method for desalinating water is distillation— heating saltwater until it evaporates (leaving behind salts in solid form) and condenses as freshwater. Another method is reverse osmosis (or microfiltration), which uses high pressure to force saltwater through a membrane filter with pores small enough to remove the salt. Today, about 13,000 desalination plants (250 if them in the United States) operate in more than 125 countries, especially in the arid nations of the Middle East, North Africa, the Caribbean, and the Mediterranean. They meet less than 0.3% of the world’s demand and 0.4% of the U.S. demand for freshwater. There are three major problems with the widespread use of desalination. First is the high cost, because it takes a lot of increasingly expensive energy to remove salt from seawater. Second, pumping large volumes of seawater through pipes and using chemicals to sterilize the water and keep down algae growth kills many marine organisms. Third, desalination produces huge quantities of salty wastewater that must go somewhere. Dumping it into nearby coastal ocean waters increases the salinity of the ocean water, which threatens food resources and aquatic life in the vicinity. Disposing of it on land could contaminate groundwater and surface water. Currently, significant desalination is practical only for water-short, wealthy countries and cities that can afford its high cost. But scientists and engineers are working to develop better and more affordable desalination technologies. Much of their research involves use of solar energy—an energy source that could help to cut costs and pollution resulting from desalination.
How Can We Use Water More Sustainably?
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We can use water more sustainably by cutting water waste, raising water prices, slowing population growth, and protecting aquifers, forests, and other ecosystems that store and release water.
CONC EPT 8-3
Reducing Water Waste Has Many Benefits
2. In the United States—the world’s largest user of water—about half of the water drawn from surface and groundwater supplies is unnecessarily wasted.
Cutting the waste of water is almost always quicker and cheaper than trying to provide new supplies of water, unless governments subsidize water supply systems, which makes water prices artificially low. Here are three estimates related to the issue of water waste provided by Mohamed El-Ashry of the World Resources Institute:
3. It is economically and technically feasible to reduce water waste to 15%, thereby meeting most of the world’s water needs for the foreseeable future.
1. About two-thirds of the water used throughout the world is unnecessarily wasted through evaporation, leaks, and other losses.
According to water resource experts, the first major cause of water waste is its low cost to users. Such underpricing is mostly the result of government subsidies that provide irrigation water, electricity, and diesel fuel used by farmers to pump water from rivers and aquifers at below-market prices. CONCEPT 8-3
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Because these subsidies keep water prices artificially low, users have little or no financial incentive to invest in water-saving technologies. According to water resource expert Sandra Postel, “By heavily subsidizing water, governments give out the false message that it is abundant and can . . . be wasted—even as rivers are drying up, aquifers are being depleted, fisheries are collapsing, and species are going extinct.” However, farmers, industries, and others benefiting from government water subsidies argue that the subsidies promote the settlement and farming of arid, unproductive land, stimulate local economies, and help keep the prices of food, manufactured goods, and electricity low. Higher water prices encourage water conservation but make it difficult for low-income farmers and city dwellers to buy enough water to meet their needs. When South Africa raised water prices, it dealt with this problem by establishing lifeline rates, which give each household a set amount of free or low-priced water to meet basic needs. When users exceed this amount, they pay higher prices as their water use increases—a userpays approach. The second major cause of water waste is a lack of government subsidies for improving the efficiency of water use. A basic rule of economics is that you get more of what you reward. Withdrawing environmentally harm-
ful subsidies that encourage water waste and providing subsidies for more efficient water use would sharply reduce water waste. HOW WOULD YOU VOTE?
We Can Cut Water Waste in Irrigation About 60% of the irrigation water applied throughout the world does not reach the targeted crops. Most irrigation systems obtain water from a groundwater well or a surface water source. The water then flows by gravity through unlined ditches in crop fields so the crops can absorb it (Figure 8-12, left). This flood irrigation method delivers far more water than is needed for crop growth and typically loses 40% of the water through evaporation, seepage, and runoff. More efficient and environmentally sound irrigation technologies can greatly reduce water demands and water waste on farms by delivering water more GOOD precisely to crops. For example, the center-pivot, NEWS low-pressure sprinkler (LEPA, Figure 8-12, right), which
Drip irrigation (efficiency 90–95%) Gravity flow (efficiency 60% and 80% with surge valves) Water usually comes from an aqueduct system or a nearby river.
✓ ■
Should water prices be raised sharply to help reduce water waste? Cast your vote online at www.cengage.com/login.
Above- or below-ground pipes or tubes deliver water to individual plant roots.
Center pivot (efficiency 80% with low-pressure sprinkler and 90–95% with LEPA sprinkler) Water usually pumped from underground and sprayed from mobile boom with sprinklers.
Figure 8-12 Three major irrigation systems are pictured here. Because of high initial costs, center-pivot irrigation and drip irrigation are not widely used. The development of new, low-cost drip-irrigation systems may change this situation.
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Water Resources and Water Pollution
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uses pumps to spray water on a crop, allows about 80% of the water to reach crops. Low-energy, precision application sprinklers, another form of center-pivot irrigation, put 90–95% of the water where crops need it. Drip, or trickle irrigation, also called microirrigation (Figure 8-12, center), is the most efficient way to deliver small amounts of water precisely to crops. It consists of a network of perforated plastic tubing installed at or below the ground level. Small pinholes in the tubing deliver drops of water at a slow and steady rate, close to the roots of individual plants. These systems drastically reduce water waste because 90–95% of the water input reaches the crops. By using less water, they also reduce the amount of harmful salt that irrigation water leaves in the soil. Drip irrigation is used on just over 1% of the world’s irrigated crop fields and about 4% of those in the United States. This percentage rises to 13% in the U.S. state of California, 66% in Israel, and 90% in Cyprus. Suppose that water were priced closer to the value of the ecological services it provides and that government subsidies that encourage water waste were reduced or eliminated. Then drip irrigation would probably be used to irrigate most of the world’s crops. Drip irrigation systems are costly, but the cost of a new type of drip irrigation system developed by the nonprofit International Development Enterprises (IDE) is one-tenth as much per hectare as that of conventional drip systems. Increased use of this inexpensive system designed for poor farmers will raise crop yields in water-short areas and help lift poor families out of poverty. Many of the world’s poor farmers use small-scale and low-cost traditional irrigation technologies. For example, farmers in countries such as Bangladesh, where water tables are high, use inexpensive, humanpowered treadle pumps to bring groundwater up to the earth’s surface and into irrigation ditches. Other farmers in some less-developed countries use buckets, small tanks with holes, or simple plastic tubing systems for drip irrigation. Rainwater harvesting is another simple and inexpensive way to provide water for drinking and growing crops throughout most of the world. Figure 8-13 lists other ways to reduce water waste in crop irrigation. Since 1950, Israel has used many GOOD of these techniques to slash irrigation water waste NEWS by 84% while irrigating 44% more land. Israel now treats and reuses 30% of its municipal sewage water for crop production and plans to treat and reuse 80% of this source by 2025. The government also gradually eliminated most water subsidies to raise Israel’s price of irrigation water, which is now one of the highest in the world. According to the United Nations, reducing the current global withdrawal of water for irrigation by just 10% would save enough water to grow crops and meet the estimated additional water demands of the earth’s cities and industries through 2025.
Solutions Reducing Irrigation Water Waste Line canals bringing water to irrigation ditches Irrigate at night to reduce evaporation Monitor soil moisture to add water only when necessary Grow several crops on each plot of land (polyculture)
Figure 8-13 There are a number of ways to reduce water waste in irrigation. Questions: Which two of these solutions do you think are the best ones? Why?
Encourage organic farming Avoid growing water-thirsty crops in dry areas Irrigate with treated waste water Import water-intensive crops and meat
We Can Cut Water Waste in Industry and Homes We could redesign many industrial processes to use much less water. Figure 8-14 lists ways to use water more efficiently in industries, homes, and businesses (Concept 8-3).
Solutions Reducing Water Waste at Work and at Home Redesign manufacturing processes to use less water Recycle water in industry Landscape yards with plants that require little water Use drip irrigation Fix water leaks Use water meters Raise water prices Use waterless composting toilets Require water conservation in water-short cities Use water-saving toilets, showerheads, and front-loading clothes washers Collect and reuse household water to irrigate lawns and nonedible plants Purify and reuse water for houses, apartments, and office buildings
Figure 8-14 There are a number of ways to reduce water waste in industries, homes, and businesses (Concept 8-3). Questions: Which three of these solutions do you think are the best ones? Why?
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Many homeowners and businesses in water-short areas are copying nature by replacing green GOOD lawns with a diversity of native plants that need NEWS little water. Such water-thrifty landscaping reduces water use by 30–85% and sharply reduces the need for labor, fertilizer, and fuel. It also helps preserve biodiversity and reduces polluted runoff, air pollution, and yard wastes. The fact that the cost of water has been too low is a major cause of excessive water use and waste in homes and industries, according to experts. About one-fifth of all U.S. public water systems do not have water meters and charge a single low rate for almost unlimited use of high-quality water. When the U.S. city of Boulder, Colorado, introduced water meters, water use per person dropped by 40%. Another problem is that we use large amounts of freshwater that is clean enough to drink to flush away wastes. According to the FAO, if current trends continue, within 40 years, we will need the world’s entire reliable flow of river water just to dilute and transport the wastes we produce. We could save much of this water if we used systems that mimic the way nature deals with wastes by recycling them. For example, we could apply the chemical cycling principle of sustainability and return the nutrient-rich sludge produced by conventional waste treatment plants to the soil as a fertilizer, instead of wasting freshwater to transport it. To make this feasible, we would have to ban the discharge of toxic industrial chemicals into sewage treatment plants. Another way to recycle our wastes is to rely more on waterless composting toilets. These devices convert human fecal matter to a small amount of dry, odorless, soil-like humus material that can be removed from a composting chamber every year or so and returned to the soil as fertilizer. Flushing toilets with water (most of it clean enough to drink) is the single largest use of domestic water. Low-flow showerheads can also save large amounts of water by cutting the flow of shower water in half. Xeros Ltd., a British company, recently developed a washing machine that uses as little as a cup of water for each washing cycle, thereby reducing the amount of water typically used to wash clothes by 98%.
We Need to Use Water More Sustainably More sustainable use of water is based on the commonsense principle stated in an old Inca proverb: “The frog does not drink up the pond in which it lives.” Figure 8-15 lists ways that scientists have suggested for using water more sustainably (Concept 8-3). Each of us can reduce our water footprints by using less water and cutting water waste (Figure 8-16). GOOD As with other problems, the solution starts with NEWS thinking globally and acting locally.
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Solutions Sustainable Water Use Waste less water and subsidize water conservation Do not deplete aquifers Preserve water quality Protect forests, wetlands, mountain glaciers, watersheds, and other natural systems that store and release water Get agreements among regions and countries sharing surface water resources Raise water prices Slow population growth
Figure 8-15 A variety of methods can help us use the earth’s water resources more sustainably (Concept 8-3). Questions: Which two of these solutions do you think are the most important? Why?
What Can You Do? Water Use and Waste ■
Use water-saving toilets, showerheads, and faucet aerators
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Shower instead of taking baths, and take short showers
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Repair water leaks
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Turn off sink faucets while brushing teeth, shaving, or washing
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Wash only full loads of clothes or use the lowest possible water-level setting for smaller loads
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Use recycled (gray) water for watering lawns and houseplants and for washing cars
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Wash a car from a bucket of soapy water, and use the hose for rinsing only
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If you use a commercial car wash, try to find one that recycles its water
■
Replace your lawn with native plants that need little if any watering
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Water lawns and yards only in the early morning or evening
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Use drip irrigation and mulch for gardens and flowerbeds
Figure 8-16 Individuals matter: You can reduce your use and waste of water. See www.h2ouse.org for a number of tips, provided by the Environmental Protection Agency and the California Urban Water Conservation Council, that you can use anywhere for saving water. Questions: Which of these steps have you taken? Which of them would you like to take?
Water Resources and Water Pollution
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8-4
How Can We Reduce the Threat of Flooding?
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CONC EPT 8-4 We can lessen the threat of flooding by protecting more wetlands and natural vegetation in watersheds, and by not building in areas subject to frequent flooding.
Some Areas Get Too Much Water from Flooding Some areas have too little water, but others sometimes have too much because of natural flooding by streams, caused mostly by heavy rain or rapidly melting snow. A flood happens when water in a stream overflows its normal channel and spills into an adjacent area, called a floodplain. These areas, which usually include highly productive wetlands, help to provide natural flood and erosion control, maintain high water quality, and recharge groundwater. People settle on floodplains to take advantage of their many assets, including fertile soil, ample water for irrigation, availability of nearby rivers for transportation and recreation, and flat land suitable for crops, buildings, highways, and railroads. Floods actually provide several benefits. They have created some of the world’s most productive farmland by depositing nutrient-rich silt on floodplains. They also recharge groundwater and help to refill wetlands, thereby supporting biodiversity and aquatic ecological services.
But floods also kill thousands of people each year and cost tens of billions of dollars in property damage. Floods are usually considered natural disasters, but since the 1960s, human activities have contributed to a sharp rise in flood deaths and damages. One such activity is the removal of water-absorbing vegetation, especially on hillsides (Figure 8-17). Another is the replacement of that vegetation with farm fields, pastures, pavement, or buildings that cannot absorb nearly as much rainwater or snow melt as undeveloped landscapes can. Another detrimental human activity is the draining of wetlands, which absorb floodwaters and reduce the severity of flooding. All of these activities are on the rise in many areas of the world. Living on floodplains also increases the threat of damage from flooding. In more-developed countries, people deliberately settle on floodplains and then expect dams, levees, and other devices to protect them from floodwaters. When heavier-than-normal rains occur, these devices can be overwhelmed. In many less-developed countries, the poor have little choice but to try to survive in flood-prone areas (see the Case Study that follows).
Tree plantation
Diverse ecological habitat
Roads destabilize hillsides
Evapotranspiration Trees reduce soil erosion from heavy rain and wind
Evapotranspiration decreases Overgrazing accelerates soil erosion by water and wind Winds remove fragile topsoil
Agricultural land
Agricultural land is flooded and silted up Gullies and landslides Heavy rain erodes topsoil
Tree roots stabilize soil Vegetation releases water slowly and reduces flooding Forested Hillside
Silt from erosion fills rivers and reservoirs
Rapid runoff causes flooding
After Deforestation
Figure 8-17 Natural capital degradation: These diagrams show a hillside before and after deforestation. Once a hillside has been deforested for timber, fuelwood, livestock grazing, or unsustainable farming, water from precipitation rushes down the denuded slopes, erodes precious topsoil, and can increase flooding and pollution in local streams. Such deforestation can also increase landslides and mudflows. A 3,000-year-old Chinese proverb says, “To protect your rivers, protect your mountains.” Question: How might a drought in this area make these effects even worse?
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■ CAS E STUDY
Living Dangerously on Floodplains in Bangladesh Bangladesh is one of the world’s most densely populated countries, with more than 162 million people packed into an area roughly the size of the U.S. state of Wisconsin (which has a population of less than 6 million). This very flat country, only a little above sea level, is one of the world’s poorest countries. The people of Bangladesh depend on moderate annual flooding during the summer monsoon season to grow rice and help maintain soil fertility in its large river delta basin. The annual floods deposit eroded Himalayan soil on the country’s crop fields. In the past, great floods occurred about every 50 years. But between 1987 and 2007, there were five severe floods, which covered a third of the country with water. Bangladesh’s flooding problems begin in the Himalayan watershed, where rapid population growth, deforestation, overgrazing, and unsustainable farming on steep and easily erodible slopes have increased flows of water during monsoon season. Monsoon rains now run more quickly off the denuded Himalayan foothills, carrying vital topsoil with them (Figure 8-17). This increased runoff of soil, combined with heavierthan-normal monsoon rains, has led to more severe flooding along Himalayan rivers as well as downstream in Bangladesh’s delta areas. In 1998, a disastrous flood covered two-thirds of Bangladesh’s land for 2 months, drowned at least 2,000 people, and left 30 million homeless. It also destroyed more than one-fourth of the country’s crops, which caused thousands of people to die of starvation. In 2002, another flood left 5 million people homeless and flooded many rice fields. Another major flood occurred in 2004.
Living on Bangladesh’s coastal floodplain at sea level means coping with storm surges, cyclones (powerful storms similar to hurricanes), and tsunamis. As many as 1 million people drowned as a result of a tropical cyclone in 1970. Another cyclone in 2003 killed more than a million people and left tens of millions homeless. Many of the coastal mangrove forests in Bangladesh and elsewhere have been cleared for fuelwood, farming, and aquaculture ponds created for raising shrimp. The result was more severe flooding, because these coastal wetlands had sheltered Bangladesh’s low-lying coastal areas from storm surges, cyclones, and tsunamis. Damages and deaths from cyclones in areas of Bangladesh still protected by mangrove forests have been much lower than in areas where the forests have been cleared. A projected rise in sea level and an increase in storm intensity during this century, mostly because of projected climate change, will likely be a major threat in coming years to millions of Bangladeshis.
We Can Reduce Flood Risks Figure 8-18 lists some ways to reduce the risk of GOOD NEWS flooding (Concept 8-4). In contrast, engineering schemes, such as the straightening and deepening of streams (channelization) can reduce upstream flooding but also can eliminate aquatic habitats, reduce groundwater discharge, and result in a faster flow. This can increase downstream flooding and sediment deposition. Levees or floodwalls along the sides of streams contain and speed up stream flow, but they also increase the water’s capacity for doing damage downstream. In addition, they do not protect against unusually high and powerful floodwaters. A dam can reduce the threat
Solutions Reducing Flood Damage P r event i on
C ont rol
Preserve forests on watersheds
Straighten and deepen streams (channelization)
Preserve and restore wetlands in floodplains
Tax development on floodplains
Figure 8-18 These are some methods for reducing the harmful effects of flooding (Concept 8-4). Questions: Which two of these solutions do you think are the best ones? Why?
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Use floodplains primarily for recharging aquifers, sustainable agriculture and forestry
Build levees or floodwalls along streams
Build dams
Water Resources and Water Pollution
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of flooding by storing water in a reservoir and releasing it gradually, but dams also have a number of disadvantages (Figure 8-9). An important way to reduce flooding is to preserve existing wetlands and restore degraded wetlands to take advantage of the natural flood control they provide in
8-5
floodplains. On a personal level, we can use the precautionary principle and think carefully about where we choose to live. Many poor people live in flood-prone areas because they have nowhere else to go. Most people, however, can choose not to live in areas especially subject to flooding.
What Are the Causes and Effects of Water Pollution?
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Water pollution, primarily caused by agricultural activities, industrial facilities, and mining, and worsened by population growth and resource use, causes illness and death in humans and other species, and disrupts ecosystems.
CONC EPT 8-5
Sources and Causes of Water Pollution Water pollution is any change in water quality that can harm living organisms or make the water unfit for human uses such as irrigation and recreation. It usually involves contamination by one or more chemicals or by excessive heat (thermal pollution). Water pollution comes from two major types of sources. The first is point sources, which discharge pollutants into bodies of surface water at specific locations by means such as drain pipes, ditches, and sewer lines. Examples include factories, sewage treatment plants (which remove some, but not all, pollutants), underground mines, ruptured oil wells, and oil tankers. Because point sources are located at specific places, they are fairly easy to identify, monitor, and regulate, except in cases where the discharge volume is huge, as in the case of the blowout of the BP oil well in the Gulf of Mexico in 2010. Most of the world’s more-developed countries have laws that help control point-source discharges. In most of the less-developed countries, there is little control of such discharges. The second major type of pollution source is nonpoint sources—broad, and diffuse areas, rather than points, from which pollutants enter bodies of surface water or air. Examples include runoff of chemicals and sediments from cropland, livestock feedlots, logged forests, urban streets, parking lots, lawns, and golf courses. Identifying and controlling discharges from such diffuse sources is difficult and expensive. Agricultural activities are by far the leading cause of water pollution. Sediment eroded from agricultural lands is the most common pollutant. Other major agricultural pollutants include fertilizers and pesticides, bacteria from livestock and food-processing wastes, and excess salts from soils of irrigated cropland. Industrial facilities, which emit a variety of harmful inorganic and organic chemicals, are a second major source of water
pollution. Mining is the third biggest source of water pollution. Surface mining disturbs the land, creating major erosion of soils and runoff of toxic chemicals. A growing problem of great concern is that of coal ash, an indestructible waste created by the burning of coal in power plants. Some power utilities store the ash on land in slurry ponds that can leak and pollute nearby bodies of water. Other utilities dump the toxic ash and associated wastewater into lakes and rivers. Another form of water pollution is caused by the widespread use of plastics that make up millions of products, all of which eventually end up in the environment. Polymers, the complex chemical compounds that make up plastics, break down very slowly and, in the process, pollute waterways and the oceans where they have been improperly discarded.
Major Water Pollutants Have Harmful Effects Table 8-1 (p. 172) lists the major types of water pollutants along with examples of each and their harmful effects and sources (Concept 8-5). Polluted water hastens the spread of infectious disease organisms (pathogens) among people who have to drink contaminated water and people who lack clean water for effective sanitation. Scientists have identified more than 500 types of disease-causing bacteria, viruses, and parasites that can be transferred into water from the wastes of humans and animals. The World Health Organization (WHO) has estimated that every year, more than 1.6 million people die from largely preventable waterborne infectious diseases that they get by drinking contaminated water or by not having enough clean water for adequate hygiene. This adds up to an average of nearly 4,400 deaths a day, 90% of them in children younger than age 5. Diarrhea alone, caused mostly by exposure to polluted water, on average kills a young child every 18 seconds. CONCEPT 8-5
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Table 8-1 Major Water Pollutants and Their Sources Type/Effects
Examples
Major Sources
Infectious agents (pathogens) Cause diseases
Bacteria, viruses, protozoa, parasites
Human and animal wastes
Oxygen-demanding wastes Deplete dissolved oxygen needed by aquatic species
Biodegradable animal wastes and plant debris
Sewage, animal feedlots, food-processing facilities, paper mills
Plant nutrients Cause excessive growth of algae and other species
Nitrates (NO3–) and phosphates (PO43–)
Sewage, animal wastes, inorganic fertilizers
Organic chemicals Add toxins to aquatic systems
Oil, gasoline, plastics, pesticides, fertilizers, cleaning solvents
Industry, farms, households, mining sites, runoff from streets and parking lots
Inorganic chemicals Add toxins to aquatic systems
Acids, bases, salts, metal compounds
Industry, households, mining sites, runoff from streets and parking lots
Sediments Disrupt photosynthesis, food webs, other processes
Soil, silt
Land erosion from farms and construction and mining sites
Heavy metals Cause cancer, disrupt immune and endocrine systems
Lead, mercury, arsenic
Unlined landfills, household chemicals, mining refuse, industrial discharges
Thermal Make some species vulnerable to disease
Heat
Electric power and industrial plants
8-6
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What Are the Major Water Pollution Problems in Streams and Lakes?
C O NC EPT 8-6 Addition of pollutants and excessive nutrients to streams and lakes can disrupt these ecosystems, and prevention of such pollution is more effective and less costly than cleaning it up.
Streams Can Cleanse Themselves, if We Do Not Overload Them
Stream Pollution in MoreDeveloped Countries
Flowing rivers and streams can recover rapidly from moderate levels of degradable, oxygen-demanding wastes through a combination of dilution and bacterial biodegradation of such wastes. But this natural recovery process does not work when streams become overloaded with such pollutants or when drought, damming, or water diversion reduce their flows (Concept 8-6). Also, while this process can remove biodegradable wastes, it does not eliminate slowly degradable and nondegradable pollutants. In a flowing stream, the breakdown of biodegradable wastes by bacteria depletes dissolved oxygen and creates an oxygen sag curve (Figure 8-19). This reduces or eliminates populations of organisms with high oxygen requirements until the stream is cleansed of oxygen-demanding wastes. We can plot similar oxygen sag curves when heated water from industrial and power plants is discharged into streams, because heating water decreases their levels of dissolved oxygen.
Laws enacted in the 1970s to control water pollution have greatly increased the number and quality of GOOD wastewater treatment plants in the United States NEWS and in most other more-developed countries. Such laws also require industries to reduce or eliminate their point-source discharges of harmful chemicals into surface waters. This has enabled the United States to hold the line against increased pollution by disease-causing agents and oxygen-demanding wastes in most of its streams. This is an impressive accomplishment given the country’s increased economic activity, resource consumption, and population growth since passage of these laws. One success story is the cleanup of the U.S. state of Ohio’s Cuyahoga River. It was so polluted that it caught fire several times and, in 1969, was photographed while burning as it flowed through the city of Cleveland. The highly publicized image of this combustible river prompted elected officials to enact laws that limited the
CHAPTER 8
Water Resources and Water Pollution
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Point source
s
Types of organisms Dissolved oxygen (ppm)
nism n water orga Normal clea h, bass, rc pe , ut ro (T efly) mayfly, ston
Pollutions tolerant fishe (carp, gar)
Fish absent, fungi, sludge worms, bacteria (anaerobic)
Pollutions tolerant fishe r) ga p, ar (c
nisms n water orga Normal clea rch, bass, (Trout, pe efly) mayfly, ston 8 ppm
8 ppm
ne
Clean Zo
al Biochemic oxygen demand
ne
Clean Zo
sition Decompo Zone
ne
Septic Zo
Recovery Zone
Figure 8-19 Natural capital: A stream can dilute and decay degradable, oxygen-demanding wastes, and it can also dilute heated water. This figure shows the oxygen sag curve (black line) and the curve of oxygen demand (white line). Depending on flow rates and the amount of biodegradable pollutants, streams recover from oxygendemanding wastes and from the injection of heated water if they are given enough time and are not overloaded (Concept 8-6). Question: What would be the effect of putting another discharge pipe emitting biodegradable waste to the right of the one in this picture?
discharge of industrial wastes into the river and into local sewage systems, and provided funds to upgrade sewage treatment facilities. Today, the river is cleaner, no longer flammable, and is widely used by boaters and anglers. This accomplishment illustrates the power of bottom-up pressure by citizens, who prodded elected officials to change a severely polluted river into an economically and ecologically valuable public resource. Fish kills and drinking water contamination still occur occasionally in some of the rivers and lakes of more-developed countries. Some of these problems are caused by the accidental or deliberate release of toxic inorganic and organic chemicals by industries and mining operations. Another cause is malfunctioning sewage treatment plants. A third cause is nonpoint runoff of pesticides and excess plant nutrients from cropland and animal feedlots.
Stream Pollution in Less-Developed Countries In most less-developed countries, stream pollution from discharges of untreated sewage and industrial wastes is a serious and growing problem. According to the World Commission on Water in the 21st Century, half of the world’s 500 major rivers are heavily polluted, and most of these polluted waterways run through less-developed countries. A majority of these countries cannot afford to
build waste treatment plants and do not have, or do not enforce, laws for controlling water pollution. According to the Global Water Policy Project, most cities in less-developed countries discharge 80–90% of their untreated sewage directly into rivers, streams, and lakes whose waters are then used for drinking, bathing, and washing clothes. Industrial wastes and sewage pollute more than two-thirds of India’s water resources and 54 of the 78 rivers and streams monitored in China. According to a 2007 report by Chinese officials, more than half of China’s 1.3 billion people live without any form of sewage treatment and 300 million Chinese do not have access to clean drinking water. In Latin America and Africa, most streams passing through urban or industrial areas suffer from severe pollution. Garbage dumped into rivers is also a problem in some less-developed nations.
Low Flow Makes Lakes and Reservoirs Vulnerable to Water Pollution Lakes and reservoirs are generally less effective at diluting pollutants than streams are, for two reasons. First, lakes and reservoirs often contain stratified layers that undergo little vertical mixing. Second, they have little or no flow. The flushing and changing of water in lakes CONCEPT 8-6
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and large artificial reservoirs can take from 1 to 100 years, compared with several days to several weeks for streams. As a result, lakes and reservoirs are more vulnerable than streams are to contamination by runoff or discharge of plant nutrients, oil, pesticides, and nondegradable toxic substances, such as lead, mercury, and selenium. These contaminants can kill bottom-dwelling organisms and fish, as well as birds that feed on contaminated aquatic organisms. Many toxic chemicals and acids also enter lakes and reservoirs from the atmosphere. Lakes and reservoirs are subject to eutrophication—the natural nutrient enrichment of a shallow lake, estuary, or slow-moving stream, mostly from runoff of plant nutrients such as nitrates and phosphates from surrounding land. Over time, some lakes become more eutrophic than others, depending on the inputs and the nature of their surrounding drainage basins. Near urban or agricultural areas, human activities can greatly accelerate the input of plant nutrients to a lake—a process called cultural eutrophication. Such inputs involve mostly nitrate- and phosphate-containing effluents from various sources, including farmland, feedlots, urban streets and parking lots, chemically fertilized suburban yards, mining sites, and municipal sewage treatment plants. Some nitrogen also reaches lakes by deposition from the atmosphere. During hot weather or drought, this nutrient overload produces dense growths, or “blooms,” of organisms such as algae and cyanobacteria, and thick growths of water hyacinth, duckweed, and other aquatic plants. These dense colonies of plant life can reduce lake productivity and fish growth by decreasing the input of solar energy needed for photosynthesis by the phytoplankton that support fish populations. When the algae die, they are decomposed by swelling populations of aerobic bacteria, which deplete dissolved oxygen in the surface layer of water near the shore as well as in the bottom layer of a lake. This can kill fish and other aerobic aquatic animals. If excess nutrients continue to flow into the lake, anaerobic bacteria take over and produce gaseous by-products such as smelly, highly toxic hydrogen sulfide and flammable methane. According to the U.S. Environmental Protection Agency (EPA), about one-third of the 100,000 medium to large lakes and 85% of the large lakes near major U.S. population centers have some degree of cultural eutrophication. The International Water Association estimates that more than half of the lakes in China suffer from cultural eutrophication. There are several ways to prevent or reduce cultural eutrophication. We can use advanced (but expen- GOOD sive) waste treatment to remove nitrates and NEWS phosphates from wastewater before it enters a lake, ban or limit the use of phosphates in household detergents and other cleaning agents, and employ soil conservation and land-use control to reduce nutrient runoff.
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There are several ways to clean up lakes suffering from cultural eutrophication. They include mechanically removing excess weeds, controlling undesirable plant growth with herbicides and algicides, and pumping air into lakes and reservoirs to prevent oxygen depletion, all of which are expensive and energy-intensive methods. As usual, pollution prevention is more effective and quite often cheaper in the long run than cleanup. A lake can usually recover from cultural eutrophication, if excessive inputs of plant nutrients into the lake are stopped (see the Case Study that follows).
■ C AS E S T UDY
Pollution in the Great Lakes The five interconnected Great Lakes of North America contain about 95% of the fresh surface water in the United States and one-fifth of the world’s fresh surface water. At least 38 million people in the United States and Canada obtain their drinking water from these lakes. Despite their enormous size, these lakes are vulnerable to pollution from point and nonpoint sources. One reason is that each year, less than 1% of the water entering these lakes flows out of them—east into the St. Lawrence River and then to the Atlantic Ocean—meaning that pollutants can take as long as 100 years to be flushed out to sea. By the 1960s, many areas of the Great Lakes were suffering from severe cultural eutrophication, huge fish kills, and contamination from bacteria and a variety of toxic industrial wastes. The impact on Lake Erie was particularly intense because it is the shallowest of the Great Lakes and has the highest concentrations of people and industrial activity along its shores. In 1972, the United States and Canada agreed to spend more than $20 billion on a Great Lakes pollution control program. This program has decreased GOOD algal blooms, increased dissolved oxygen levels, NEWS boosted sport and commercial fishing catches in Lake Erie, and allowed most swimming beaches to reopen— making this one of the nations’ greatest environmental success stories. These improvements occurred mainly because of new or upgraded sewage treatment plants, better treatment of industrial wastes, and bans on the use of detergents, household cleaners, and water conditioners that contain phosphates. Despite this important progress, many problems remain. In 2006, Canadian scientists reported that cities around the lakes were releasing the equivalent of more than 100 Olympic-size swimming pools full of raw sewage into the lakes every day. This is because dozens of municipal sewage systems combine storm water with wastewater and allow emergency overflows into the lakes. According to the scientists, these systems overflow far too easily and too often. Nonpoint runoff of pesticides and fertilizers from new lawns in suburban developments, fueled by population growth and urban sprawl, now surpasses indus-
Water Resources and Water Pollution
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trial pollution as the greatest threat to the lakes. Bottom sediments in 26 toxic hot spots remain heavily pollutedfrom various sources. And biological pollution in the form of growing populations of zebra mussels and more than 180 other invasive species threaten native aquatic species and cause at least $200 million a year in damages (see Chapter 6 Case Study, p. 128). Air quality over the Great Lakes has generally improved, but about half of the toxic compounds entering the lakes still come from atmospheric deposition of pesticides, mercury from coal-burning plants, and other toxic chemicals from as far away as Mexico and Russia. In a survey done by Wisconsin biologists, one of every four fish taken from the Great Lakes was unsafe
8-7
for human consumption. Despite ongoing pollution problems, EPA funding for cleanup of the Great Lakes dropped 80% between 1992 and 2009, but in 2010, Congress increased funding for this long-term project. Some environmental and health scientists call for taking a prevention approach and banning the use of toxic chlorine compounds such as bleach used in the pulp and paper industry, which is prominent around the Great Lakes. They would also ban new waste incinerators, which can release toxic chemicals into the atmosphere, and they would stop the discharge into the lakes of 70 toxic chemicals that threaten human health and wildlife. So far, officials in the industries involved have successfully opposed such bans.
What Are the Major Pollution Problems Affecting Groundwater and Other Drinking Water Sources?
▲
Chemicals used in agriculture, industry, transportation, and homes can spill and leak into groundwater and make it undrinkable; while we can purify polluted water, protecting it through pollution prevention is the least expensive and most effective strategy.
CONC EPT 8-7
Groundwater Pollution Is a Serious Hidden Threat in Some Areas Groundwater supplies the drinking water for about half of the U.S. population and 95% of Americans who live in rural areas. According to many scientists, groundwater pollution is a serious threat to human health. Common pollutants such as fertilizers, pesticides, gasoline, and organic solvents can seep into groundwater from numerous sources (Figure 8-20, p. 176). People who dump or spill gasoline, oil, paint thinners, and other organic solvents onto the ground also contaminate groundwater (Concept 8-7). On a global scale, we do not know much about groundwater pollution because few countries go to the great expense of locating, tracking, and testing aquifers. But the results of scientific studies in scattered parts of the world are alarming. Groundwater provides about 70% of China’s drinking water. In 2006, the Chinese government reported that aquifers in about nine of every ten Chinese cities were polluted or overexploited, and could take hundreds of years to recover. In the United States, an EPA survey of 26,000 industrial waste ponds and lagoons found that one-third of them had no liners to prevent toxic liquid wastes from seeping into aquifers. One-third of these sites are within 1.6 kilometers (1 mile) of a drinking water well. In addition, almost two-thirds of America’s liquid hazardous wastes are injected into the ground in disposal wells,
some of which leak water into aquifers used as sources of drinking water. By 2008, the EPA had completed the cleanup of about 357,000 of the more than 479,000 underground tanks in the United States that were leaking gasoline, diesel fuel, home heating oil, or toxic solvents into groundwater. During this century, scientists expect many of the millions of such tanks that have been installed around the world to become corroded and leaky, possibly contaminating groundwater and becoming a major global health problem. Determining the extent of a leak from a single underground tank can be extremely costly and often impossible. Groundwater used as a source of drinking water can also be contaminated with nitrate ions (NO3–), especially in agricultural areas where nitrates in fertilizer can leach into groundwater. Nitrite ions (NO2–) in the stomach, colon, and bladder can convert some of the nitrate ions in drinking water to organic compounds that have been shown in tests to cause cancer in more than 40 animal species. The conversion of nitrates in tap water to nitrites in infants under 6 months old can cause a potentially fatal condition known as “blue baby syndrome,” in which blood lacks the ability to carry sufficient oxygen to body cells. Another problem is toxic arsenic, which contaminates drinking water when a well is drilled into aquifers where soils and rock are naturally rich in arsenic, or when human activities such as mining and ore processing release arsenic into drinking water supplies. CONCEPT 8-7
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175
Figure 8-20 Natural capital degradation: These are the principal sources of groundwater contamination in the United States (Concept 8-7). Another source in coastal areas is saltwater intrusion from excessive groundwater withdrawal. (Figure is not drawn to scale.) Question: What are three sources shown in this picture that might be affecting groundwater in your area?
Polluted air
Hazardous waste injection well
Pesticides and fertilizers Deicing road salt
Coal strip mine runoff
Buried gasoline and solvent tanks Cesspool, septic tank
Gasoline station
Pumping well
Water pumping well
Waste lagoon
Sewer
Landfill
Leakage from faulty casing
Accidental spills
Discharge
r
r
ate
shw
Fre
ifer
u
r aq
ate
w esh
ife aqu
Freshwater aquifer Groundwater flow
Fr
According to a 2007 study by the WHO, more than 140 million people in 70 countries are drinking water with arsenic concentrations of 5–100 times the accepted safe level of 10 parts per billion (ppb). The WHO estimates that long-term exposure to such arsenic is likely to cause hundreds of thousands cancer deaths. One study reported that suspending tiny particles of rust in arsenic-contaminated water, and then drawing them out with hand-held magnets, removed GOOD enough arsenic from the water to make it safe to NEWS drink. Stay tuned while scientists evaluate this process.
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groundwater slow down chemical reactions that decompose wastes. Thus, it can take decades to thousands of years for contaminated groundwater to cleanse itself of slowly degradable wastes (such as DDT). On a human time scale, nondegradable wastes (such as toxic lead, arsenic, and fluoride) are there permanently. Although there are ways to clean up contaminated groundwater (Figure 8-21, right) such methods are very expensive. Thus, preventing groundwater contamination (Figure 8-21, left) is the only effective way to deal with this serious water pollution problem (Concept 8-7).
Pollution Prevention Is the Only Effective Way to Protect Groundwater
There Are Many Ways to Purify Drinking Water
When groundwater becomes contaminated, it cannot cleanse itself of degradable wastes as quickly as flowing surface water can. Groundwater flows so slowly—usually less than 0.3 meter (1 foot) per day—that contaminants are not diluted and dispersed effectively. In addition, groundwater usually has much lower concentrations of dissolved oxygen (which helps decompose many contaminants) and smaller populations of decomposing bacteria. Also, the usually cold temperatures of
Most of the more-developed countries have laws establishing drinking water standards. But most of the lessdeveloped countries do not have such laws or, if they do have them, they do not enforce them. This has caused a great number of people to turn to bottled water, thinking that it is safer than other sources (see the Case Study that follows). However, there are simple ways as well as complex ways to purify drinking water obtained from surface and groundwater sources.
CHAPTER 8
Water Resources and Water Pollution
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Figure 8-21 There are ways to prevent and ways to clean up contamination of groundwater but prevention is by far the most effective approach (Concept 8-7). Questions: Which two of these preventive solutions do you think are the best ones? Why?
Solutions Groundwater Pollution P r eventi o n
Cl eanup
Find substitutes for toxic chemicals
Pump to surface, clean, and return to aquifer (very expensive)
Keep toxic chemicals out of the environment Install monitoring wells near landfills and underground tanks Require leak detectors on underground tanks
Inject microorganisms to clean up contamination (less expensive but still costly)
Ban hazardous waste disposal in landfills and injection wells Store harmful liquids in aboveground tanks with leak detection and collection systems
Pump nanoparticles of inorganic compounds to remove pollutants (still being developed)
In more-developed countries, wherever people depend on surface water, it is usually stored in a reservoir for several days. This improves clarity and taste by increasing dissolved oxygen content and allowing suspended matter to settle. Typically, the water is then pumped to a purification plant and treated to meet government drinking water standards. In areas with very pure groundwater or surface water sources, little treatment is necessary. Some cities, including New York City, have found that protecting watersheds that supply their drinking water is a lot cheaper than building water purification plants. We can also use simpler measures to purify GOOD drinking water. In tropical countries that lack NEWS centralized water treatment systems, the WHO urges people to purify drinking water by exposing a clear plastic bottle filled with contaminated water to intense sunlight. The sun’s heat and UV rays can kill infectious microbes in as little as 3 hours. Painting one side of the bottle black can improve heat absorption in this simple solar disinfection method. Where this measure has been used, incidence of dangerous childhood diarrhea has decreased by 30–40%. ■ CAS E S T UDY
Is Bottled Water a Good Option? Despite some problems, experts say the United States has some of the world’s cleanest drinking water. Municipal water systems in the United States are required to test their water regularly for a number of pollutants and to make the results available to citizens. Yet about half of all Americans worry about getting sick from tap water contaminants, and many drink high-priced bot-
tled water or install expensive water purification systems. Other countries, too, are relying more and more on bottled water. However, studies by the Natural Resources Defense Council reveal that in the United States, a bottle of water costs between 240 and 10,000 times as much as the same volume of tap water. Other studies indicate that about one-fourth of the bottled water sold is ordinary tap water in a bottle, and that bacteria or fungi contaminate about 40% of bottled water. Use of bottled water also causes environmental problems, according to a 2007 study by the Worldwatch Institute and a 2008 study by water experts Peter Gleick and Heather Cooley. Every year, the number of plastic water bottles thrown away, if lined up end-toend, would circle the earth’s equator eight times. Also, toxic gases and liquids and greenhouse gases are emitted during the manufacture of plastic water bottles and the delivery of bottled water (sometimes over great distances) to suppliers. In addition, withdrawing water for bottling is helping to deplete some aquifers. Health officials suggest that before drinking expensive bottled water or buying costly home water purifiers, consumers should have their water tested by local health departments or private labs (but not by companies trying to sell water purification equipment). Independent experts contend that unless tests show otherwise, buying bottled water or in-home water treatment systems is not worth the expense. HOW WOULD YOU VOTE?
✓ ■
Should pollution standards for bottled water be as strict as those for water from public systems? Cast your vote online at www.cengage.com/login.
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8-8
What Are the Major Water Pollution Problems Affecting Oceans?
▲
C O NC EPT 8-8 The great majority of ocean pollution originates on land and includes oil and other toxic chemicals and solid waste, which threaten fish and wildlife, and disrupt marine ecosystems; the key to protecting oceans is to reduce the flow of pollutants into coastal waters.
Ocean Pollution Is a Growing and Poorly Understood Problem Coastal areas—especially wetlands, estuaries, coral reefs, and mangrove swamps—bear the brunt of our enormous inputs of pollutants and wastes into the oceans (Figure 8-22). This is not surprising because about 40% of the world’s population (53% in the United States) lives on or near coasts (see the Case Study that follows). Industry Nitrogen oxides from autos and smokestacks, toxic chemicals, and heavy metals in effluents flow into bays and estuaries.
Cities Toxic metals and oil from streets and parking lots pollute waters; sewage adds nitrogen and phosphorus.
According to a 2006 State of the Marine Environment study by the UN Environment Programme (UNEP), an estimated 80% of marine pollution originates on land (Concept 8-8), and this percentage could rise significantly by 2050 if coastal populations double as projected. The report says that 80–90% of the municipal sewage from most coastal areas of less-developed countries, and in some such areas of more-developed countries, is dumped into oceans untreated.
Urban sprawl Bacteria and viruses from sewers and septic tanks contaminate shellfish beds and close beaches; runoff of fertilizer from lawns adds nitrogen and phosphorus.
Construction sites Sediments are washed into waterways, choking fish and plants, clouding waters, and blocking sunlight. Farms Runoff of pesticides, manure, and fertilizers adds toxins and excess nitrogen and phosphorus.
Closed shellfish beds Closed beach
Red tides Excess nitrogen causes explosive growth of toxic microscopic algae, poisoning fish and marine mammals.
Oxygen-depleted zone
Toxic sediments Chemicals and toxic metals contaminate shellfish beds, kill spawning fish, and accumulate in the tissues of bottom feeders. Figure 8-22 Natural Oxygen-depleted zone capital degradation: Sedimentation and algae Residential areas, factories, overgrowth reduce sunlight, and farms all contribute to kill beneficial sea grasses, use the pollution of coastal waters. up oxygen, and degrade habitat. According to the UN Environment Programme, coastal water pollution costs the world more than $30,000 a minute, primarily for health problems and premature deaths. Questions: What do you think are the three worst pollution problems shown here? For each one, how does it affect two or more of the ecological and economic services listed in Figure 3-8 (p. 60)?
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CHAPTER 8
Healthy zone Clear, oxygen-rich waters promote growth of plankton and sea grasses, and support fish.
Water Resources and Water Pollution
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Drainage basin
PENNSYLVANIA
MARYLAND Baltimore P
o pt
Ch
Ra
p paha n
Richmond
no ck
DELAWARE
No oxygen
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Yo rk
Low concentrations of oxygen
R.
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VIRGINIA
n
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Washington
k an
oke
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xent R.
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WEST VIRGINIA
NEW JERSEY
t ic
at
ac
m
Since 1960, the Chesapeake Bay (Figure 8-23)—America’s largest estuary—has been in serious trouble from water pollution, mostly because of human activities. Between 1940 and 2007, the number of people living in the Chesapeake Bay area grew from 3.7 million to 16.6 million. The estuary receives wastes from point and nonpoint sources scattered throughout a huge drainage basin that includes nine large rivers and 141 smaller streams and creeks in parts of six states (Figure 8-23). The bay has become a huge pollution sink because only 1% of the waste entering it is flushed into the Atlantic Ocean. It is also so shallow that people can wade through much of it. Phosphate and nitrate levels have risen sharply in many parts of the bay, causing algal blooms and oxygen depletion. Commercial harvests of its once-abundant oysters, crabs, and several important fish species have fallen sharply since 1960 because of a combination of pollution, disease, and overfishing. Point sources, primarily sewage treatment plants and industrial plants (often in violation of their discharge permits), account for 60% by weight of the phosphates entering the bay. Nonpoint sources, mostly runoff of fertilizer and animal wastes from urban, suburban, and agricultural land, and deposition from the atmosphere, account for 60% by weight of the nitrates. In 1983, the United States implemented the Chesapeake Bay Program. In this ambitious attempt at integrated coastal management, citizens’ groups, communities, state legislatures, and the federal government are working together to reduce pollution inputs into the bay. Strategies include establishing land-use regulations in the bay’s six watershed states to reduce agricultural and urban runoff, banning phosphate detergents, upgrading sewage treatment plants, and better monitoring of industrial discharges. In addition, wetlands
ATLANTIC OCEAN
Harrisburg Su sq ue ha nn a R.
■ CAS E S T UDY
Chesapeake Bay— an Estuary in Trouble
Cooperstown
NEW YORK
Pot o
Studies of some U.S. coastal waters have found vast colonies of viruses thriving in raw sewage and in effluents from sewage treatment plants (which do not remove viruses) and from leaking septic tanks. According to one study, one-fourth of the people swimming in such waters at coastal beaches in the United States develop ear infections, sore throats, eye irritations, respiratory disease, or gastrointestinal disease. Runoffs of sewage and agricultural wastes into coastal waters introduce large quantities of nitrate and phosphate plant nutrients, which can cause explosive growths of harmful algae. These harmful algal blooms are called red, brown, or green toxic tides. They can release waterborne and airborne toxins that poison seafood, damage fisheries, kill some fish-eating birds, and reduce tourism.
R.
Chesapeake Bay
Norfolk
Figure 8-23 Chesapeake Bay, the largest estuary in the United States, is severely degraded as a result of water pollution from point and nonpoint sources in six states and from the atmospheric deposition of air pollutants.
are being restored and large areas of the bay are being replanted with sea grasses to help filter out nutrients and other pollutants. In the past, the area’s once-huge oyster population helped to filter excess nutrients, and some scientists have proposed restoring the oysters to help clean up the water. The hard work on improving the water quality of the Chesapeake Bay has paid off. Between 1985 and 2000, phosphorus levels declined 27%, nitrogen levels dropped 16%, and grasses growing on the bay’s floor have made a comeback. This is a significant achievement given the increasing population in the watershed and the fact that nearly 40% of the nitrogen inputs come from the atmosphere. However, there is still a long way to go, and a sharp drop in state and federal funding has slowed progress. Despite some setbacks, the Chesapeake Bay Program shows what can be done when diverse groups work together to achieve goals that benefit both wildlife and people.
Ocean Pollution from Oil Crude petroleum (oil as it comes out of the ground) and refined petroleum (fuel oil, gasoline, and other processed petroleum products) reach the ocean from a number of sources and become highly disruptive pollutants. Tanker accidents and blowouts at offshore drilling rigs (when oil escapes under high pressure from a borehole in the ocean floor) get most of the publicity because of their high visibility. The 2010 blowout in the Gulf of Mexico was the worst environmental catastrophe in U.S. history. But over time, studies have shown, CONCEPT 8-8
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179
the largest source of ocean pollution from oil is urban and industrial runoff from land, much of it from leaks in pipelines and oil-handling facilities (Concept 8-8). At least 37%—and perhaps even 50%—of the oil reaching the oceans is waste oil, dumped, spilled, or leaked onto the land or into sewers by cities and industries, as well as by people improperly disposing of their used motor oil. Volatile organic hydrocarbons in oil kill many aquatic organisms immediately upon contact, especially if these animals are in their vulnerable larval forms. Other chemicals in oil form tarlike globs that float on the surface and coat the feathers of seabirds (especially diving birds) and the fur of marine mammals. This oil coating destroys their natural heat insulation and buoyancy, causing many of them to drown or die from loss of body heat. Heavy oil components that sink to the ocean floor or wash into estuaries can smother bottom-dwelling organisms such as crabs, oysters, mussels, and clams, or make them unfit for human consumption. Some oil spills have killed coral reefs. Research shows that populations of many forms of marine life recover from exposure to large amounts of crude oil in warm waters with fairly rapid currents within about 3 years. But in cold and calm waters, full recovery can take decades. In addition, recovery from exposure to refined oil, especially in estuaries and salt marshes, can take 10–20 years or longer. Oil slicks that wash onto beaches can have a serious economic impact on coastal communities. If they are not too large, oil spills can be partially cleaned up by mechanical means including floating booms, skimmer boats, and absorbent devices such as large pillows filled with feathers or hair. Bacteria can be used to speed up the decomposition of remaining oil, as can chemicals and fire. However, scientists estimate that current cleanup methods can recover no more than 15% of the oil from a major spill. Thus, preventing oil pollution is the most
8-9
Coastal Water Pollution Pr e v e ntion
C le a n u p
Reduce input of toxic pollutants
Improve oil-spill cleanup capabilities
Separate sewage and storm water lines Ban dumping of wastes and sewage by ships in coastal waters
Use nanoparticles on sewage and oil spills to dissolve the oil or sewage (still under development)
Ban dumping of hazardous material Strictly regulate coastal development, oil drilling, and oil shipping Require double hulls for oil tankers
Require secondary treatment of coastal sewage
Use wetlands, solar-aquatic, or other methods to treat sewage
Figure 8-24 There are methods for preventing pollution of coastal waters and methods for cleaning it up (Concept 8-8). Questions: Which two of these solutions do you think are the most important? Why?
effective and, in the long run, the least costly approach (Concept 8-8). Figure 8-24 lists ways to prevent and reduce GOOD NEWS pollution of coastal waters. The key to protecting the oceans is to reduce the flow of pollution from land and air and from streams emptying into these waters (Concept 8-8). Thus, ocean pollution control must be linked with land-use and air pollution control policies.
How Can We Best Deal with Water Pollution?
▲
C O NC EPT 8-9 Reducing water pollution requires that we prevent it, work with nature to treat sewage, cut resource use and waste, reduce poverty, and slow population growth.
Reducing Surface Water Pollution from Nonpoint Sources There are a number of ways to reduce nonpoint GOOD sources of water pollution, most of which come NEWS from agricultural practices. Farmers can reduce soil erosion by using several soil conservation methods.
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Solutions
CHAPTER 8
They can also reduce the amount of fertilizer that runs off into surface waters by using slow-release fertilizer, using no fertilizer on steeply sloped land, and planting buffer zones of vegetation between cultivated fields and nearby surface waters. Organic farming techniques also offer ways to help prevent water pollution. For example, organic farmers
Water Resources and Water Pollution
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use manure for fertilizer, in which nitrogen is contained within organic matter that clings to the soil. In contrast, industrialized agriculture applies granulated fertilizer to cropland, which can more easily wash into streams. By applying pesticides only when needed and relying more on integrated pest management, farmers can also reduce pesticide runoff. HOW WOULD YOU VOTE?
✓ ■
Should we greatly increase efforts to reduce water pollution from nonpoint sources even though this could be quite costly? Cast your vote online at www.cengage.com/login.
Laws Can Help to Reduce Water Pollution from Point Sources The Federal Water Pollution Control Act of 1972 (renamed the Clean Water Act when it was amended in 1977) and the 1987 Water Quality Act form the basis of U.S. efforts to control pollution of the country’s surface waters (see the Case Study that follows). The Clean Water Act sets standards for allowed levels of 100 key water pollutants and requires polluters to get permits that limit how much of these various pollutants they can discharge into aquatic systems. The EPA has been experimenting with a discharge trading policy, which uses market forces to reduce water pollution in the United States. Under this program, a permit holder can pollute at higher levels than allowed in its permit if it buys credits from permit holders who are polluting below their allowed levels. Environmental scientists warn that the effectiveness of such a system depends on how low the cap on total pollution levels in any given area is set and on how regularly the cap is lowered. They also warn that discharge trading could allow water pollutants to build up to dangerous levels in areas where credits are bought. They call for careful scrutiny of the cap levels and for the gradual lowering of the caps to encourage prevention of water pollution and development of better pollution control technology. Neither adequate scrutiny of the cap levels nor gradual lowering of caps is a part of the current EPA discharge trading system. ■ CAS E S T UDY
U.S. Experience with Reducing Point-Source Pollution According to the EPA, the Clean Water Act of 1972 led to numerous improvements in U.S. water quality. These are some of the encouraging developments that GOOD took place between 1992 and 2002 (the latest fig- NEWS ures available): •
The percentage of Americans served by community water systems that met federal health standards increased from 79% to 94%.
•
The percentage of U.S. stream lengths found to be fishable and swimmable increased from 36% to 60% of those tested.
•
The proportion of the U.S. population served by sewage treatment plants increased from 32% to 74%.
•
Annual wetland losses decreased by 80%.
These are impressive achievements given the increases in the U.S. population and its per capita consumption of water and other resources since 1972. But there is more work to be done. In 2006, the EPA found that 45% of the country’s lakes and 40% of the streams surveyed were still too polluted for swimming or fishing, and that runoff of animal wastes from hog, poultry, and cattle feedlots and meat processing facilities were polluting seven of every ten U.S. rivers. In 2010, a New York Times study found that thousands of the country’s largest water polluters (about 45% of them) were relying on a U.S. Supreme Court decision that created uncertainty over which waterways are to be regulated for pollution. As a result, these companies are violating the act and are not being prosecuted by the EPA, and water pollution levels are rising in some areas. About 117 million Americans get their drinking water from sources that are being polluted in this way. Toxic coal ash from the burning of coal in power plants is another problem that is difficult to deal with legally, as there are no U.S. federal regulations that specifically govern the disposal of coal ash. Some state regulators have used the Clean Water Act to combat such pollution, but the law was not designed to deal with this problem. According to a 2009 study of EPA records, 93% of the 313 coal-burning power plants that had violated the Clean Water Act between 2004 and 2009 had also avoided fines or other penalties. Some environmental scientists call for strengthening the Clean Water Act. Suggested improvements include shifting the focus of the law to water pollution prevention instead of focusing mostly on end-ofpipe removal of specific pollutants; greatly increased monitoring for violations of the law and much larger mandatory fines for violators; and regulating irrigation water quality (for which there is no federal regulation). Another suggestion is to expand the rights of citizens to bring lawsuits to ensure that water pollution laws are enforced. Still another suggestion is to rewrite the Clean Water Act to clarify that it covers all waterways (as Congress originally intended). This would eliminate confusion about which waterways are covered and stop major polluters from using this confusion to keep polluting in many areas. Many people oppose these proposals, contending that the Clean Water Act’s regulations are already too restrictive and costly. Some state and local officials argue that in many communities, it is unnecessary and too expensive to test all the water for pollutants as required by federal law. CONCEPT 8-9
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HOW WOULD YOU VOTE?
✓ ■
Should the U.S. Clean Water Act be strengthened? Cast your vote online at www.cengage.com/login.
Sewage Treatment Reduces Water Pollution In rural and suburban areas with suitable soils, sewage from each house usually is discharged into a septic tank with a large drainage field (Figure 8-25). About one-fourth of all homes in the United States are served by septic tanks. In urban areas in the United States and other moredeveloped countries, most waterborne wastes from homes, businesses, and storm runoff flow through a network of sewer pipes to wastewater or sewage treatment plants. Raw sewage reaching a treatment plant typically undergoes one or two levels of wastewater treatment. The first is primary sewage treatment—a physical process that uses screens and a grit tank to remove large floating objects and to allow solids such as sand and rock to settle out. Then the waste stream flows into a primary settling tank where suspended solids settle out as sludge (Figure 8-26, left). The second level is secondary sewage treatment—a biological process in which aerobic bacteria remove as much as 90% of dissolved and biodegradable, oxygen-demanding organic wastes (Figure 8-26, right). Before discharge, water from sewage treatment plants usually undergoes bleaching to remove water coloration and disinfection to kill disease-carrying bacteria and some (but not all) viruses. The usual method for accomplishing this is chlorination. One potential problem is that chlorine can react with organic materials in water to form small amounts of chlorinated hydrocarbons. Some of these chemicals cause cancers in test animals,
can increase the risk of miscarriages, and can damage the human nervous, immune, and endocrine systems. Use of other disinfectants, such as ozone and ultraviolet light, is increasing, but they cost more and their effects do not last as long as those of chlorination. Federal law in the United States requires primary and secondary treatment for all municipal sewage treatment plants, but exemptions from secondary treatment are possible when the cost of installing such treatment poses an excessive financial burden on towns and cities. According to the EPA, some 500 U.S. cities have also failed to meet federal standards for sewage treatment plants, and 34 East Coast cities simply screen out large floating objects from their sewage before discharging it into the coastal waters of the Atlantic Ocean.
We Can Improve Conventional Sewage Treatment Environmental scientist Peter Montague calls for redesigning the conventional sewage treatment system shown in Figure 8-26. The idea is to prevent toxic and hazardous chemicals from reaching sewage treatment plants and thus from getting into sludge and water discharged from such plants. Montague suggests several ways to do this. One is to require industries and businesses to remove toxic and hazardous wastes from water sent to municipal sewage treatment plants. Another is to encourage industries to reduce or eliminate their use and waste of toxic chemicals.
✓ ■
HOW WOULD YOU VOTE?
Should we ban the discharge of toxic chemicals into pipes leading to sewage treatment plants? Cast your vote online at www.cengage.com/login.
Manhole cover (for cleanout) Septic tank Gas Distribution box Scum Wastewater Sludge Drain field (gravel or crushed stone) Vent pipe Perforated pipe Figure 8-25 Solutions: Septic tank systems are often used for disposal of domestic sewage and wastewater in rural and suburban areas.
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Water Resources and Water Pollution
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Primary
Bar screen
Grit chamber
Secondary
Settling tank
Aeration tank
Settling tank
Chlorine disinfection tank
To river, lake, or ocean Raw sewage from sewers
Sludge
(kills bacteria)
Activated sludge
Air pump
Sludge digester
Figure 8-26 Solutions: Primary and secondary sewage treatment systems help to reduce water pollution. Question: What do you think should be done with the sludge produced by sewage treatment plants?
Another suggestion is to require or encourage more owners of homes, apartment buildings, and office buildings to eliminate sewage outputs by switching to waterless, odorless composting toilet systems that are installed, maintained, and managed by professionals. Such systems would be cheaper to install and maintain than current sewage systems are, because they do not require vast systems of underground pipes connected to centralized sewage treatment plants. They also save a great deal of water. Many communities are using unconventional, but highly effective, wetland-based sewage treatment systems (Science Focus, below), which work with nature (Concept 8-9).
Sludge drying bed
Disposed of in landfill or ocean or applied to cropland, pasture, or rangeland
There Are Sustainable Ways to Reduce and Prevent Water Pollution It is encouraging that since 1970, most of the GOOD world’s more-developed countries have enacted NEWS laws and regulations that have significantly reduced point-source water pollution. These improvements were largely the result of bottom-up political pressure on elected officials by individuals and groups. To environmental and health scientists, the next step is to increase efforts to reduce and prevent water pollution in both more- and less-developed countries. They would begin by asking the question: How can we avoid producing water pollutants in the first place? (Concept 8-9).
S C I E NC E FO C U S Treating Sewage by Working with Nature
B
iologist John Todd has developed an ecological approach to treating sewage, which he calls living machines. This purification process begins when sewage flows into a passive solar greenhouse or outdoor site containing rows of large open tanks populated by an increasingly complex series of organisms. In the first set of tanks, algae and microorganisms decompose organic wastes, with sunlight speeding up the process. Water hyacinths, cattails, bulrushes, and other aquatic plants growing in the tanks take up the resulting nutrients. After flowing though several of these natural purification tanks, the water passes
through an artificial marsh made of sand, gravel, and bulrushes, which filters out algae and remaining organic waste. Some of the plants also absorb, or sequester, toxic metals such as lead and mercury, and secrete natural antibiotic compounds that kill pathogens. Next, the water flows into aquarium tanks, where snails and zooplankton consume microorganisms and are in turn consumed by crayfish, tilapia, and other fish that can be eaten or sold as bait. After 10 days, the clear water flows into a second artificial marsh for final filtering and cleansing. The water can be made pure enough to drink by treat-
ing it with ultraviolet light or by passing the water through an ozone generator, usually immersed out of sight in an attractive pond or wetland habitat. Operating costs are about the same as those of a conventional sewage treatment plant. Critical Thinking Can you think of any disadvantages of using such a nature-based system instead of a conventional sewage treatment plant? Do you think any such disadvantages outweigh the advantages? Why or why not?
CONCEPT 8-9 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
183
Solutions
What Can You Do?
Water Pollution
Reducing Water Pollution
Prevent groundwater contamination Reduce nonpoint runoff Reuse treated wastewater for drinking and irrigation Find substitutes for toxic pollutants Work with nature to treat sewage Practice the three R's of resource use (reduce, reuse, recycle) Reduce air pollution Reduce poverty Slow population growth
Figure 8-27 There are a number of ways to prevent and reduce water pollution (Concept 8-9). Questions: Which two of these solutions do you think are the best ones? Why?
■
Fertilize garden and yard plants with manure or compost instead of commercial inorganic fertilizer
■
Minimize your use of pesticides, especially near bodies of water
■
Prevent yard wastes from entering storm drains
■
Do not use water fresheners in toilets
■
Do not flush unwanted medicines down the toilet
■
Do not pour pesticides, paints, solvents, oil, antifreeze, or other products containing harmful chemicals down the drain or onto the ground
Figure 8-28 Individuals matter: You can help to reduce water pollution. Questions: Which three of these actions do you think are the most important? Why?
Figure 8-27 lists ways to achieve this goal over GOOD NEWS the next several decades. This shift to pollution prevention will not take place unless citizens put political pressure on elected officials and also take actions to reduce their own daily contributions to water pollution. Figure 8-28 lists some actions you can take to help reduce water pollution. The three principles of sustainability (see back cover) can guide us in using water more sustainably during this century. We can use solar energy to help purify the water we use. Recycling more water will help us to reduce water waste and pollution, and we can use natural nutrient cycles to treat our waste in wetland-based sewage treatment systems (Science Focus, p. 183). Preserving biodiversity by avoiding the disruption of aquatic systems and their
bordering terrestrial systems is a key factor in maintaining water supplies and water quality. Here are this chapter’s three big ideas: ■ We can use water more sustainably by cutting water waste, raising water prices, and protecting aquifers, forests, and other ecosystems that store and release water. ■ The key to protecting wetlands, lakes, streams, rivers, and oceans is to reduce the flow of pollutants from land and air, and from streams emptying into ocean waters. ■ Reducing water pollution requires that we prevent it, work with nature in treating sewage, cut resource use and waste, reduce poverty, and slow population growth.
There is a water crisis today. But the crisis is not about having too little water to meet our needs. It is a crisis of mismanaging water so badly that billions of people—and the environment—suffer badly. WORLD WATER VISION REPORT
REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 155. What percentage of the earth’s freshwater is available to us? Define groundwater and explain how it is replenished. Define zone of saturation, water table, and aquifer. Distinguish among surface water, surface runoff, and reliable surface runoff. What percentage of
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the world’s reliable runoff are we using and what percentage are we likely to be using by 2025? What is a watershed (drainage basin)? 2. What is drought and what are its causes and harmful effects? How many people in the world lack regular access to safe drinking water and how many do not have
Water Resources and Water Pollution
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access to basic sanitation? Define virtual water and give an example. What is a water footprint? Describe water conflicts in the Middle East and discuss some possible solutions. 3. What are the advantages and disadvantages of withdrawing groundwater? Describe ways to prevent or slow groundwater depletion. What are the advantages and disadvantages of using large dams and reservoirs? What are five ecological services that rivers provide? Describe the California Water Project and the controversy over this water transfer project. Summarize the Aral Sea disaster. Define desalination and distinguish between desalinating water using distillation and reverse osmosis. What are the limitations of desalination and how might we overcome them? 4. What percentage of the world’s water is unnecessarily wasted and what are two causes of such waste? Describe four irrigation methods and describe five ways to reduce water waste in irrigation. List eight ways to reduce water waste in industry and homes. List six ways to use water more sustainably. Describe six ways in which you can reduce your use and waste of water. 5. What is a floodplain and why do people choose to live on floodplains? What are the benefits and drawbacks of floods? Describe human activities that increase the risk of flooding. Describe the increased risk of flooding that Bangladesh faces. How can we reduce flooding risks? 6. What is water pollution? Distinguish between point sources and nonpoint sources of water pollution and give an example of each. What are the three major causes of water pollution? List eight major types of water pollutants and give an example of each. 7. Describe how streams can cleanse themselves and how these cleansing processes can be overwhelmed. What
is an oxygen sag curve, and what causes it? Describe the state of stream pollution in more-developed and lessdeveloped countries. Give two reasons why lakes cannot cleanse themselves as readily as streams. Distinguish between eutrophication and cultural eutrophication. List three ways to prevent or reduce cultural eutrophication. Describe pollution in the Great Lakes and the progress that has been made in reducing this pollution. 8. Explain why groundwater cannot cleanse itself very well. What are the major sources of groundwater contamination in the United States? Describe the threat from arsenic in groundwater. List six ways to prevent and three ways to clean up groundwater contamination. Describe the environmental problems caused by the widespread use of bottled water. Is bottled water always good drinking water? Explain. 9. How are coastal ocean waters polluted? What causes toxic algal blooms and what are their harmful effects? Describe the pollution problems in Chesapeake Bay. How serious is oil pollution of the oceans, what are its effects, and what can be done to reduce such pollution? List ways to reduce water pollution from (a) nonpoint sources and (b) point sources. Describe the U.S. experience with reducing pointsource water pollution. 10. What is a septic tank and how does it work? Describe how primary sewage treatment and secondary sewage treatment are used to help purify water. Describe John Todd’s living machine and how it treats sewage. List six ways to prevent or reduce water pollution. List five ways in which you can reduce your contribution to water pollution.
Note: Key terms are in bold type.
CRITICAL THINKING 1. List three ways in which you could apply Concepts 8-3 and 8-9 to making your lifestyle more environmentally sustainable. 2. Explain why you are for or against (a) raising the price of water while providing lifeline rates for the poor and lower middle class, and (b) providing government subsidies to farmers for improving irrigation efficiency. 3. Calculate how many liters (and gallons) of water are wasted in 1 month by a toilet that leaks 2 drops of water per second (1 liter of water equals about 3,500 drops and 1 liter equals 0.265 gallons). 4. Assume that you are an official charged with drawing up plans for controlling pollution, and briefly describe one idea for controlling pollution from each of the following
sources: (a) a pipe draining pollutants from a factory into a stream, (b) a parking lot at a shopping mall bordered by a stream, (c) a farmer’s field on a slope next to a stream. 5. What role does population growth play in (a) groundwater pollution problems and (b) coastal water pollution problems? 6. When you flush your toilet, where does the wastewater go? Trace the actual flow of this water in your community from your toilet through sewer pipes to a wastewater treatment plant and from there to the environment. Try to visit a local sewage treatment plant to see what it does with your wastewater. Compare the processes it uses with those shown in Figure 8-26. What happens to the sludge produced by this plant? What improvements, if any, would you suggest for this plant? WWW.CENGAGEBRAIN.COM
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185
7. In your community, a. what are the principal nonpoint sources of contamination of surface water and groundwater? b. what is the source of drinking water? c. how is drinking water treated? d. how many times during each of the past 5 years have levels of tested contaminants violated federal standards? Were violations reported to the public? e. what problems related to drinking water, if any, have arisen? What action, if any, has your local government taken to solve such problems?
f. is groundwater contamination a problem? If so, what has been done about it? g. is there a vulnerable aquifer that needs protection to ensure the quality of groundwater? Is your local government aware of this? What action (if any) has it taken? 8. List two questions that you would like to have answered as a result of reading this chapter.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 8 for many study aids and ideas for further
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reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
Water Resources and Water Pollution
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9
Nonrenewable Energy Resources
Key Questions and Concepts 9-1
What is net energy and why is it important?
9-4 What are the advantages and disadvantages of using coal?
Net energy is the amount of highquality energy available from an energy resource minus the amount of energy needed to make it available.
C O N C E P T 9 - 4 A Conventional coal is plentiful and produces a high net energy yield at a low cost, but it has a very high environmental impact.
What are the advantages and disadvantages of using oil?
C O N C E P T 9 - 4 B Synthetic fuels produced from coal have lower net energy yields and higher environmental impacts than conventional coal.
CONCEPT 9-1
9-2
Conventional oil is currently abundant, has a high net energy yield, and is relatively inexpensive, but using it causes air and water pollution, and releases greenhouse gases into the atmosphere.
CONCEPT 9-2A
Heavy oils from tar sand and oil shale exist in potentially large supplies but have low net energy yields and higher environmental impacts than conventional oil has. CONCEPT 9-2B
What are the advantages and disadvantages of using nuclear energy?
9-5
Nuclear power has a low environmental impact and a low accident risk, but high costs, public fear of accidents, long-lived radioactive wastes, and the potential for spreading nuclear weapons technology have limited its use.
CONCEPT 9-5
What are the advantages and disadvantages of using natural gas?
9-3
Conventional natural gas is more plentiful than oil, has a high net energy yield and a fairly low cost, and has the lowest environmental impact of all fossil fuels.
CONCEPT 9-3
Typical citizens of advanced industrialized nations each consume as much energy in 6 months as typical citizens in less developed countries consume during their entire life. MAURICE STRONG
Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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187
What Is Net Energy and Why Is It Important?
9-1
▲
Net energy is the amount of high-quality energy available from an energy resource minus the amount of energy needed to make it available.
C O NC EPT 9-1
Fossil Fuels Supply Most of Our Commercial Energy Almost all of the energy that we use for heating our buildings and for other purposes comes at no cost from the sun—one of the three principles of sustainability (see back cover). Without this essentially inexhaustible solar energy, the earth’s average temperature would be –240°C (–400°F), and life as we know it would not exist. This direct input of solar energy produces several indirect forms of renewable solar energy: wind, hydropower (falling and flowing water), and biomass (solar energy converted to chemical energy and stored in vegetation), all of which we explore in Chapter 10.
Commercial energy, or energy that is sold in the marketplace, is what we use to supplement the sun’s energy. Currently, most commercial energy comes from extracting and burning nonrenewable energy resources obtained from the earth’s crust, primarily carbon-containing fossil fuels—oil, natural gas, and coal (Figure 9-1). About 85% of the commercial energy consumed in the world comes from nonrenewable energy resources— 79% from fossil fuels (oil, natural gas, and coal) and 6% from nuclear power (Figure 9-2, left). The remaining 15% of the commercial energy we use comes from renewable energy resources—biomass, hydropower, geothermal, wind, and solar energy. Nonrenewable fossil fuels are widely used because they are abundant, transportable, and cheap compared
Oil and natural gas Oil storage
Coal Contour strip mining
Oil drilling platform
Geothermal energy Hot water storage
Oil well
Geothermal power plant
Pipeline
Gas well Mined coal Area strip mining
Pump
Impe
Oil
s rock
Natur
Pipeline
Unde r coal mground ine
rviou
Wate r
Drilling tower
al gas
Wate r Coal seam
Wate r and b is heated r as dry ought up wet s steam or team Hot r ock Magm
a
Water penetrates down through the rock
Figure 9-1 Natural capital: Important nonrenewable energy resources that we can remove from the earth’s crust are coal, oil, natural gas, and some forms of geothermal energy. We can also extract nonrenewable uranium ore from the earth’s crust and process it to increase its concentration of uranium-235, which can serve as a fuel in nuclear reactors to produce electricity. Question: Can you think of a time during a typical day when you are not directly or indirectly using one of these resources?
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Nonrenewable Energy Resources
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Nuclear power 6% Geothermal, solar, wind 1%
Nuclear power 8% Geothermal, solar, wind 1%
Hydropower 3%
7
EWABLE REN %
Biomass 11%
Coal 24%
Hydropower, 3%
Natural gas 23%
ABLE 15% NEW RE
Natural gas 21%
Coal 22%
Biomass 3%
EW AB LE
EW AB LE
85%
World
Oil 40%
EN NR NO
EN NR NO
Oil 34%
93%
United States
Figure 9-2 Commercial energy use, by source, for the world (left) and the United States (right) Question: Why do you think the world as a whole relies more on renewable energy than the United States does? (Data from U.S. Department of Energy, British Petroleum, Worldwatch Institute, and International Energy Agency)
to most other alternatives. World energy consumption has increased every year since 1982. Most of the increase has occurred in rapidly developing countries such as China, India, South Korea, and Brazil.
9-2
According to scientists, we should evaluate all energy resources on the basis of their supplies, their environmental impacts, and how much useful energy they actually provide (Science Focus, p. 190).
What Are the Advantages and Disadvantages of Using Oil?
▲
CONC EPT 9-2A Conventional oil is currently abundant, has a high net energy yield, and is relatively inexpensive, but using it causes air and water pollution and releases greenhouse gases into the atmosphere.
▲
CONC EPT 9-2B Heavy oils from tar sand and oil shale exist in potentially large supplies but have low net energy yields and higher environmental impacts than conventional oil has.
We Depend Heavily on Oil Petroleum, or crude oil (oil as it comes out of the ground), is a black, gooey liquid consisting of hundreds of different combustible hydrocarbons along with small amounts of sulfur, oxygen, and nitrogen impurities. It is also known as conventional oil and as light crude oil. Deposits of conventional oil and natural gas often are trapped together under a dome deep within the earth’s crust on land or under the seafloor. The crude oil is dispersed in pores and cracks in underground rock formations, somewhat like water saturating a sponge.
To extract the oil, developers drill a well vertically or horizontally into the deposit beneath the ground or sea bottom. Pressure within the deposit forces the oil up to the surface, or oil is drawn by gravity out of the rock pores and flows into the bottom of the well where it is pumped to the surface. After years of pumping, usually a decade or so, the pressure in a well drops and its rate of conventional crude oil production starts to decline. This point in time is referred to as peak production for the well. After it is extracted, conventional crude oil is transported to a CONCEPTS 9-2A AND 9-2B
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189
SCIE N C E FO C US Net Energy is the Only Energy That Really Counts
I
t takes energy to get energy. For example, before oil becomes useful to us, it must be found, pumped up from beneath the ground or ocean floor, transferred to a refinery and converted to useful fuels, transported to users, and burned in furnaces and cars. Each of these steps uses highquality energy. The second law of thermodynamics tells us that some of the high-quality energy used in each step is automatically wasted and degraded to lower-quality energy (see Chapter 2, p. 30). The usable amount of high-quality energy available from a given quantity of an energy resource is its net energy. It is the total amount of energy available from an energy resource minus the energy needed to find, extract, process, and get that energy to consumers (Concept 9-1). It is calculated by estimating the total energy available from the resource over its lifetime and then subtracting the amount of energy used, automatically wasted because of the second law of thermodynamics, and unnecessarily wasted in finding, processing, concentrating, and transporting the useful energy to users. For example, suppose that it takes 8 units of energy to produce 10 units of energy from a particular energy resource. Then the net useful energy yield is only 2 units of energy. We can express net energy as the ratio of energy produced to the energy used to produce it. In this example, the net energy ratio would be 10/8, or approximately 1.25. The higher the ratio, the greater the net energy. When the ratio is less than 1, there is a net energy loss. Figure 9-A shows estimated net energy ratios for various types of space heating, high-temperature heat for industrial processes, and transportation.
Space Heating Passive solar
5.8
Natural gas
4.9
Oil
4.5
Active solar
1.9
Coal gasification
1.5
Electric heating 0.4 (coal-fired plant) Electric heating 0.4 (natural-gas-fired plant) Electric heating 0.3 (nuclear plant)
High-Temperature Industrial Heat Surface-mined coal
28.2
Undergroundmined coal
25.8
Natural gas
4.9
Oil
4.7
Coal gasification
1.5
CHAPTER 9
Critical Thinking Should governments require that all energy resources be evaluated in terms of their net energy? Why do you think this is not being done?
Direct solar 0.9 (concentrated)
Transportation Natural gas
4.9
Gasoline (refined crude oil)
4.1
Biofuel (ethanol)
1.9
Coal liquefaction
1.4
Oil shale
1.2
refinery by pipeline, truck, or ship (oil tanker). There it is heated to separate it into components with different boiling points (Figure 9-3) in a complex process called refining. This process, like all other steps in the cycle of oil production and use, decreases the net energy yield of oil.
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Currently, oil has a high net energy ratio because much of it comes from large, accessible, and easy-to-extract land deposits such as those in the Middle East. As these sources become depleted, the net energy ratio of oil will decline and its price is expected to rise sharply. Electricity produced at a nuclear power plant has a low net energy ratio because large amounts of energy are needed throughout the nuclear fuel cycle, which includes extracting and processing uranium ore, converting it into nuclear fuel, building and operating nuclear power plants, dismantling the highly radioactive plants after their 15–60 years of useful life, and storing the resulting highly radioactive wastes safely for 10,000–240,000 years. Each of these steps uses energy and costs money. Some analysts estimate that ultimately, the nuclear fuel cycle will lead to a net energy loss because we will have to put more energy into it than we will ever get out of it.
Figure 9-A Science: This diagram shows net energy ratios for various energy systems over their estimated lifetimes: the higher the net energy ratio, the greater the net energy available (Concept 9-1). Question: What other factors besides net energy ratios should we consider in evaluating energy resources? (Data from U.S. Department of Energy and Colorado Energy Research Institute, Net Energy Analysis, 1976; and Howard T. Odum and Elisabeth C. Odum, Energy Basis for Man and Nature, 3rd ed., New York: McGraw-Hill, 1981)
Some of the products of crude oil distillation, called petrochemicals, are used as raw materials in cleaning fluids, pesticides, plastics, synthetic fibers, paints, medicines, and many other products. Producing a desktop computer, for example, typically requires about ten times its weight in fossil fuels, mostly oil.
Nonrenewable Energy Resources
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Lowest Boiling Point Gases
Gasoline
Aviation fuel
Heating oil
Diesel oil
Naphtha
Heated crude oil
Furnace
Grease and wax
Asphalt
Highest Boiling Point Figure 9-3 Science: Crude oil is refined in a giant distillation column that can be as tall as a nine-story building. Its components are removed at various levels, depending on their boiling points. The most volatile components with the lowest boiling points are removed at the top of the column.
Some analysts say that there is a lot of oil still to be found. But they are talking mostly about small, dispersed, deposits of light and heavy crude oil and deposits of unconventional oil-like materials that are difficult and expensive to extract. These resources are much more expensive to develop than conventional crude oil has been, and they have much lower net energy yields. Using them also results in a much higher environmental impact, as we learned clearly in 2010 with the devastating blowout of the BP oil well located in deep water off the U.S. Gulf Coast. Based on data from the U.S. Department of Energy (DOE) and the U.S. Geological Survey (USGS), if global oil consumption trends continue, then Saudi Arabia could supply the world’s entire oil needs for only about 7 years. The remaining estimated proven reserves under Alaska’s North Slope—the largest ever found in North America—would meet current world demand for only 6 months or U.S. demand alone for less than 3 years. In addition, the estimated unproven reserves in Alaska’s Arctic National Wildlife Refuge (ANWR) would meet the current world demand for only 1–5 months and U.S. demand for 7–24 months (Figure 9-4). The United States produces about 9% of the world’s crude oil but uses 23% of the world’s oil production. The basic problem is that the United States has only about 1.5% of the world’s proven crude oil reserves, much of it located in environmentally sensitive areas. Since 1984, crude oil use in the United States has exceeded new domestic discoveries, and U.S. production carries a high cost—about $7.50–$10 per barrel, compared to $1–$2 per barrel in Saudi Arabia. This helps 14 13
Because the oil industry is the world’s largest business, control of oil reserves is the single greatest source of global economic and political power. Proven oil reserves are identified deposits from which conventional oil can be extracted profitably at current prices with current technology. The 13 countries that make up the Organization of Petroleum Exporting Countries (OPEC) have about two-thirds of the world’s proven crude oil reserves and thus are likely to control most of the world’s oil supplies for many decades. Today, OPEC’s members are Algeria, Angola, Ecuador, Indonesia, Iran, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, the United Arab Emirates, and Venezuela. Saudi Arabia has the largest portion of the world’s conventional proven crude oil reserves (20%). It is followed by Canada (15%), whose huge supply of tar sands (discussed below) was recently classified as a conventional source of oil. In order, other countries with large proven reserves are Iran, Iraq, Kuwait, the United Arab Emirates, Venezuela, and Russia.
12 11 Barrels of oil per year (billions)
Most of the World’s Remaining Oil Is Not Easily Available
10
Projected U.S. oil consumption
9 8 7 6 5 4 3 2
Arctic refuge oil output over 50 years
1 0 2000
2010
2020
2030
2040
2050
Year Figure 9-4 The amount of crude oil that might be found in the Arctic National Wildlife Refuge, if developed and extracted over 50 years, is only a tiny fraction of projected U.S. oil consumption. In 2008, the DOE projected that developing this oil would take 10–20 years and would lower gasoline prices at the pump by 6 cents per gallon at most. (Data from U.S. Department of Energy, U.S. Geological Survey, and Natural Resources Defense Council)
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to explain why in 2009, the United States imported almost 60% of its crude oil (up from 24% in 1970). This importation results in a massive annual transfer of wealth from the United States to oil-producing countries. The U.S. Department of Energy estimates that if current trends continue, the United States will import 70% of its oil by 2025. According to a 2005 report by the Institute for the Analysis of Global Security, almost one-fourth of the world’s crude oil is controlled by states that sponsor or condone terrorism. The report points out that buying oil from such countries helps to fund terrorism. According to a 2006 poll of 100 U.S. foreign policy experts in Foreign Policy magazine, the highest priority in fighting terrorism must be to sharply reduce America’s dependence on foreign oil. The U.S. Energy Information Agency as well as a number of independent geologists estimate that if the United States opens up virtually all of its public lands and coastal regions to oil exploration, it will find an amount of crude oil that would probably meet no more than about 1% of the country’s current annual need and this need is projected to increase. In addition, this oil would be developed only at very high production costs, low net energy yields, and high environmental impacts. In other words, according to these energy analysts, the United States cannot even come close to meeting its huge and growing demand for crude oil and gasoline by increasing domestic supplies.
Using Conventional Oil Has Advantages and Disadvantages Figure 9-5 lists the advantages and disadvantages of using conventional crude oil as an energy resource (Concept 9-2A). A critical and growing problem is that burning oil or any carbon-containing fossil fuel releases the green-
Trade-Offs Conventional Oil Figure 9-5 Using crude oil as an energy resource has advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
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Adva nta ge s
Disad vant ag es
Ample supply for several decades
Water pollution from oil spills and leaks
High net energy yield but decreasing
Environmental costs not included in market price
Low land disruption
Releases CO2 and other air pollutants when burned
Efficient distribution system
Vulnerable to international supply interruptions
CHAPTER 9
house gas CO2 into the atmosphere. According to most of the world’s top climate scientists, this will warm the atmosphere and contribute to projected climate disruption during this century. Currently, burning oil, mostly as gasoline and diesel fuel for transportation, accounts for 43% of global CO2 emissions. HOW WOULD YOU VOTE?
✓ ■
Do the advantages of relying on conventional crude oil as the world’s major energy resource outweigh its disadvantages? Cast your vote online at www.cengage.com/login.
Will Heavy Oils from Oil Sand and Oil Shale Save Us? Tar sand, or oil sand, is a mixture of clay, sand, water, and a combustible organic material called bitumen— a thick, sticky, tar-like heavy oil with a high sulfur content. Northeastern Alberta in Canada has three-fourths of the world’s tar sand resources in sandy soil under a huge area of remote boreal forest. Other deposits are in Venezuela, Colombia, Nigeria, Russia, and the U.S. state of Utah. The amount of heavy oil potentially available in Canada’s tar sands is roughly equal to seven times the total conventional oil reserves of Saudi Arabia. If we include known unconventional heavy oil reserves that can be extracted from tar sands and converted into synthetic crude oil, Canada has the world’s second largest oil reserves (15% of the total) after Saudi Arabia with 20%. The major problem with developing this resource is that it has severe impacts on land, air, water, wildlife, and climate. Much of Canada’s tar sand is being stripmined, which involves clear-cutting the overlying boreal forest, draining wetlands, and diverting some rivers and streams. Next, the overburden of sandy soil, rocks, peat, and clay is stripped away to expose the tar sand deposits. Then five-story-high electric power shovels dig up the tar sand and load it into three-story-high trucks, which carry it to an upgrading plant. There the oil sand is mixed with hot water and steam to extract the bitumen, which is heated by natural gas in huge cookers and converted into a low-sulfur, synthetic, heavy crude oil suitable for refining. This process uses large amounts of water and creates lake-size tailing ponds of polluted and essentially indestructible toxic wastewater. The project also fills the mining region’s air with dust, steam, smoke, gas fumes, and a tarry stench. It releases 3 to 5 times more greenhouse gases per barrel of the heavy synthetic crude oil than is released in the extraction and production of conventional crude oil. Finally, the tar sands project uses a great deal of energy and therefore has a low net energy yield. In short, producing heavy oil from tar sands is one of the world’s least efficient, dirtiest, and most environmentally harmful ways to produce energy. Oily rocks are another potential supply of heavy oil. Such rocks, called oil shales, contain a solid combustible
Nonrenewable Energy Resources
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mixture of hydrocarbons called kerogen. It is extracted from crushed oil shales after they are heated in a large container—a process that yields a distillate called shale oil. Before the thick shale oil can be sent by pipeline to a refinery, it must be heated to increase its flow rate and processed to remove sulfur, nitrogen, and other impurities. Estimated potential global supplies of shale oil are about 240 times larger than estimated global supplies of conventional crude oil. But most of these oil shale deposits are locked up in rock and ore of such low grade that it takes considerable energy and money to mine and convert the kerogen to shale oil. Thus, its net energy yield is low, even lower than that of heavy oil produced from tar sands. It also takes a lot of water to produce shale oil—about 5 barrels of water for each barrel of shale oil. Digging up and processing shale oil also releases 27–52% more CO2 into the atmosphere per unit of energy produced. Figure 9-6 lists the advantages and disadvantages of using heavy oil from tar sand and oil shale as energy resources.
9-3
Trade-Offs Heavy Oils from Oil Shale and Tar Sand A d vant ag es
D i s a d v a nt a g e s
Large potential supplies
Low net energy yield
Easily transported within and between countries Efficient distribution system in place
Releases CO2 and other air pollutants when produced and burned
Severe land disruption and high water use
Figure 9-6 Using heavy oil from tar sand and oil shale as energy resources has advantages and disadvantages. (Concept 9-2). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
What Are the Advantages and Disadvantages of Using Natural Gas?
▲
Conventional natural gas is more plentiful than oil, has a high net energy yield and a fairly low cost, and has the lowest environmental impact of all fossil fuels.
CONC EPT 9-3
Natural Gas Is a Useful and Clean-Burning Fossil Fuel Natural gas is a mixture of gases, 50–90% of which is methane (CH4). It also contains smaller amounts of heavier gaseous hydrocarbons such as propane (C3H8) and butane (C4H10), and small amounts of highly toxic hydrogen sulfide (H2S). It is a versatile fuel that can be burned to heat space and water and to propel vehicles. Conventional natural gas lies above most reservoirs of crude oil. But that found in deep-sea and remote land areas where natural gas pipelines have not been built is usually burned off because it costs too much to collect it and build networks of pipelines to distribute it to users. This is a significant waste of this resource. When a natural gas field is tapped, propane and butane gases are liquefied under high pressure and removed as liquefied petroleum gas (LPG). LPG is stored in pressurized tanks for use mostly in rural areas not served by natural gas pipelines. The rest of the gas (mostly methane) is purified and pumped into pressurized pipelines for distribution across land areas.
So that it can be transported across oceans, natural gas is converted to liquefied natural gas (LNG) at a high pressure and at the very low temperature of about –162ºC (–260ºF). This highly flammable liquid is then put aboard refrigerated tanker ships. After arriving at its destination, it is heated and converted back to the gaseous state at regasification plants before it is distributed by pipeline. As with any fossil fuel, burning natural gas releases the greenhouse gas carbon dioxide (CO2) into the atmosphere. However, it releases much less CO2 per unit of energy produced than do the production and use of coal, conventional oil, or oil from tar sand and oil shale. Unconventional natural gas is also found in underground sources. One is coal bed methane gas found in coal beds near the earth’s surface across parts of the United States and Canada. Another unconventional source of natural gas is methane hydrate: methane trapped in icy, cage-like structures of water molecules. They are buried under some areas of arctic tundra permafrost in places such as Alaska and Siberia and deep beneath the ocean bottom. So far, it costs too much to get natural gas from CONCEPT 9-3
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Figure 9-7 Using conventional natural gas as an energy resource has advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using conventional natural gas outweigh its disadvantages? Explain.
Trade-Offs Conventional Natural Gas A d vant ag es
D i s ad v a nt a g e s
Ample supplies
Low net energy yield for LNG
High net energy yield
Releases CO2 and other air pollutants when burned
Emits less CO2 and other pollutants than other fossil fuels
Difficult and costly to transport from one country to another
methane hydrates, and the release of methane (a potent greenhouse gas) to the atmosphere during removal and processing will amplify atmospheric warming. Japan imports large amounts of LNG from Russia, and the United States plans to become the world’s largest importer of LNG by 2025. Some analysts warn that this could make the United States too dependent on countries that have not been consistently stable and friendly, such as Russia and Iran, for supplies of LNG. In addition, LNG has a low net energy yield, as more than a third of its energy content is used to liquefy it, process it, deliver it to users by ship, and convert it back to natural gas. Russia—the Saudi Arabia of natural gas—has about 27% of the world’s proven natural gas reserves, fol-
9-4
What Are the Advantages and Disadvantages of Using Coal?
▲
C O NC EPT 9-4A Conventional coal is plentiful and produces a high net energy yield at a low cost, but it has a very high environmental impact.
▲
C O NC EPT 9-4B
Synthetic fuels produced from coal have lower net energy yields and higher environmental impacts than conventional coal.
Coal Is a Plentiful but Dirty Fuel Coal is a solid fossil fuel that was formed from the remains of land plants that were buried 300–400 million years ago and then subjected to intense heat and pressure over those millions of years (Figure 9-8). Coal is burned in power plants (Figure 9-9) to generate about 42% of the world’s electricity, 49% of the electricity used in the United States, and 70% of that in China. It is also burned in industrial plants to make iron, steel, and other products. In order, the three largest coal-burning countries are China, the United States, and India. Coal is the world’s most abundant fossil fuel. According to the USGS, identified and unidentified global sup-
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lowed by Iran (15%) and Qatar (14%). The United States has only 3% of the world’s proven natural gas reserves. The long-term global outlook for conventional natural gas supplies is better than that for crude oil. At current consumption rates, known reserves of conventional natural gas should last the world 62–125 years and the United States 82–118 years. Figure 9-7 lists the advantages and disadvantages of using conventional natural gas as an energy resource. (Concept 9-3). Because of its advantages over oil, coal, and nuclear energy, some analysts see natural gas as the best fuel to help us make the transition to an energy economy that is less dependent on dirty fossil fuels.
CHAPTER 9
plies of coal could last for 214–1,125 years, depending on how rapidly they are used. The United States holds 28% of the world’s proven coal reserves, followed by Russia (with 18%), China (14%), Australia (9%), and India (7%). The USGS estimates that identified U.S. coal reserves should last about 250 years at the current consumption rate. But a 2007 study by the U.S. National Academy of Sciences puts that estimate at about 100 years. The major problem with coal is that it is by far the dirtiest of all fossil fuels to burn. The processes of mining it and making it available severely degrade land and pollute water and air. When coal is burned without expensive pollution control devices, it creates significant air pollution and releases large amounts of CO2
Nonrenewable Energy Resources
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Increasing heat and carbon content
Increasing moisture content Lignite (brown coal)
Peat (not a coal)
Bituminous (soft coal)
Anthracite (hard coal)
Heat
Heat
Heat
Pressure
Pressure
Pressure
Partially decayed plant matter in swamps and bogs; low heat content
Low heat content; low sulfur content; limited supplies in most areas
Extensively used as a fuel because of its high heat content and large supplies; normally has a high sulfur content
Highly desirable fuel because of its high heat content and low sulfur content; supplies are limited in most areas
Figure 9-8 Over millions of years, several different types of coal have formed. Peat is a soil material made of moist, partially decomposed organic matter and is not classified as a coal, although it is used as a fuel. The different major types of coal vary in the amounts of heat, carbon dioxide, and sulfur dioxide released per unit of mass when they are burned.
Waste heat
Coal bunker
Cooling tower transfers waste heat to atmosphere
Turbine
Generator Cooling loop
Stack Pulverizing mill
Condenser
Filter
Boiler
Toxic ash disposal
Figure 9-9 Science: This power plant burns pulverized coal to boil water and produce steam that spins a turbine to produce electricity. The steam is cooled, condensed, and returned to the boiler for reuse. Waste heat can be transferred to the atmosphere or to a nearby source of water. The largest coal-burning power plant in the United States, located in Indiana, burns three 100-car trainloads of coal per day. Question: Does the electricity that you use come from a coal-burning power plant?
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Coal-fired electricity
286%
Synthetic oil and gas produced from coal
150% 100%
Coal
■ C AS E S T UDY
The Problem of Coal Ash
92%
Tar sand
86%
Oil
58%
Natural gas Nuclear power fuel cycle
17% 10%
Geothermal
Figure 9-10 CO2 emissions, expressed as percentages of emissions released by burning coal directly, vary with different energy resources. These emissions can enhance the earth’s natural greenhouse effect (Figure 2-10, p. 33) and lead to warming of the atmosphere (Concept 9-2). Question: Which produces more CO2 emissions per kilogram, burning coal to heat a house or heating with electricity generated by coal? (Data from U.S. Department of Energy)
(Figure 9-10) and black carbon particulates (soot), as well as trace amounts of toxic mercury and radioactive materials. The burning of coal accounts for at least onefourth of the world’s annual CO2 emissions. The use of coal also produces dangerous wastes (see the Case Study that follows). Figure 9-11 lists the advantages and disadvantages of using coal as an energy resource. In short, coal is
Trade-Offs Coal Adva nta ge s
Disad vant ag es
Ample supplies in many countries
Severe land disturbance and water pollution Fine particle and toxic mercury emissions threaten human health
High net energy yield
Low cost when environmental costs are not included
Emits large amounts of CO2 and other air pollutants when produced and burned
Figure 9-11 Using coal as an energy resource has advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using coal as an energy resource outweigh its disadvantages? Explain.
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cheap and plentiful and is distributed over much of the planet. But the mining and burning of coal have severe impacts on the earth’s air, water, land, and climate, as well as on human health (Concept 9-4A).
A growing problem with the use of coal is that burning it and removing pollutants from the resulting emissions produces an ash that contains highly toxic and indestructible chemicals such as arsenic, cadmium, chromium, lead, mercury, and radioactive radium. Every year, the amount of hazardous ash produced by coal-fired power plants in the United States would fill a train with enough rail cars to stretch three-and-onehalf times the distance between New York City and Los Angeles, California. Some of the non-toxic ash from coal-burning plants is sold and recycled into cement and concrete, used as a base for paving roads, and used in fertilizers. However, in the United States, more than half of the ash, much of it toxic, is either buried (sometimes in active or abandoned mines where it can contaminate groundwater) or made into a wet slurry that is stored in holding ponds. From the ponds, these indestructible toxic wastes can slowly leach into groundwater or break through their earthen dams and severely pollute nearby rivers, groundwater, and towns. Wet storage of this waste is cheap and the U.S. government does not inspect or regulate the more than 500 wet coal ash storage ponds located near power plants in 32 states. The hazards of unregulated wet slurry storage of coal ash became clear on December 22, 2008, when a rupture occurred in a wall of a coal ash storage pond not too far from Knoxville, Tennessee. The resulting spill flooded an area larger than the combined areas of 300 football fields with toxic sludge that destroyed or damaged 40 homes and other buildings. It also tainted waterways and soil with arsenic and other toxic chemicals. In 2007, the EPA determined that toxic metals and other harmful chemicals in coal ash have contaminated groundwater used by 63 communities in 26 U.S states. In 2009, the EPA also estimated that there are 44 coal ash ponds in several states that are extremely hazardous. Another 2009 study by the Environmental Integrity Project put the number of such ponds at 100. Environmental scientists argue that coal ash should be regulated for its potential to be a highly toxic material. For nearly three decades, coal and electric utility companies have successfully opposed such regulations. HOW WOULD YOU VOTE?
✓ ■
Should we phase out using coal to produce electricity during the next few decades? Cast your vote online at www.cengage.com/login.
Nonrenewable Energy Resources
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We Can Convert Coal into Gaseous and Liquid Fuels We can convert solid coal into synthetic natural gas (SNG) by a process called coal gasification, which removes sulfur and most other impurities from coal. We can also convert it into liquid fuels such as methanol and synthetic gasoline through a process called coal liquefaction. These fuels, called synfuels, are often referred to as cleaner versions of coal. But compared to burning coal directly, the production of synfuels requires mining 50% more coal. Producing and burning synfuels also requires the use of large amounts of water and other resources, and it could add 50% more CO2 to the atmosphere (Figure 9-10). As a result, synfuels have a lower net energy yield and cost more to produce per unit of energy than producing coal costs. Figure 9-12 lists the advantages and disadvantages of using liquid and gaseous synfuels produced from coal (Concept 9-4B).
9-5
Trade-Offs Synthetic Fuels A d vant ag es
D i s a d v a nt a g e s
Large potential supply in many countries
Low to moderate net energy yield Requires mining 50% more coal with increased land disturbance, water pollution and water use
Vehicle fuel Lower air pollution than coal
Higher CO2 emissions than coal
Figure 9-12 The use of synthetic natural gas (SNG) and liquid synfuels produced from coal as energy resources has advantages and disadvantages (Concept 9-4B). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
What Are the Advantages and Disadvantages of Using Nuclear Energy?
▲
Nuclear power has a low environmental impact and a low accident risk, but high costs, public fear of accidents, long-lived radioactive wastes, and the potential for spreading nuclear weapons technology have limited its use.
CONC EPT 9-5
How Does a Nuclear Fission Reactor Work? The source of energy for nuclear power is nuclear fission, a nuclear change in which the nuclei of certain isotopes with large mass numbers (such as uranium-235) are split apart into lighter nuclei when struck by neutrons. Each fission releases two or three more neutrons plus energy. These multiple fissions within a critical mass of nuclear fuel form a chain reaction, which releases an enormous amount of energy (Figure 9-13) that we can use to produce electricity at a nuclear power plant. Nuclear fission produces radioactive fission fragments containing isotopes that spontaneously shoot out fast-moving particles (alpha and beta particles), gamma rays (a form of high-energy electromagnetic radiation), or both. These unstable isotopes are called radioactive isotopes, or radioisotopes. Exposure to alpha, beta, and gamma radiation and the high-speed neutrons emitted in a nuclear fission chain reaction and by the resulting radioactive wastes can harm human cells in two ways. First, harmful mutations of DNA molecules in genes and chromosomes can cause genetic defects in one or more generations of
Uranium-235
Fission fragment
Energy n
n Neutron
n
Energy n
Uranium-235
Fission fragment
n
Energy n
Energy
Figure 9-13 Fission of a uranium-235 nucleus by a neutron (n) releases more neutrons that cause multiple fissions in a nuclear chain reaction.
CONCEPT 9-5 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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offspring. Second, tissue damage such as burns, miscarriages, eye cataracts, and cancers (bone, thyroid, breast, skin, and lung) can occur during the victim’s lifetime. To evaluate the advantages and disadvantages of nuclear power, we must know how a nuclear power plant and its accompanying nuclear fuel cycle work. A nuclear power plant is a highly complex and costly system designed to perform a relatively simple task: to boil water and produce steam that spins a turbine and generates electricity. Light-water reactors (LWRs) like the one diagrammed in Figure 9-14 produce 85% of the world’s nuclear-generated electricity (100% in the United States). Operators of such plants move control rods in and out of the reactor core to absorb neutrons, thereby regulating the rate of fission and amount of power produced. A coolant, usually water, circulates through the reactor’s core to remove heat and keep fuel rods and other materials from melting and releasing massive amounts of radioac-
tivity into the atmosphere and water. An LWR includes an emergency core cooling system as a backup to help prevent such meltdowns. A containment shell with thick, steel-reinforced concrete walls surrounds the reactor core. It is designed to keep radioactive materials from escaping into the environment, in case there is an internal explosion or a melting of the reactor’s core. It also helps protect the core from some external threats such as tornadoes and plane crashes. The overlapping and multiple safety features of a modern nuclear reactor greatly reduce the chance of a serious nuclear accident. But these safety features make nuclear power plants very expensive to build and maintain. A nuclear power plant is only one part of the nuclear fuel cycle (Figure 9-15), which also includes the mining of uranium, processing and enriching the uranium to make fuel, using it in a reactor, and safely
Small amounts of radioactive gases Uranium fuel input (reactor core)
Control rods Containment shell
Waste heat
Heat exchanger Steam
Turbine
Generator
Hot coolant
Pump
Pump Coolant
Pump
Pump
Moderator
Shielding
Pressure vessel
Cool water input
Waste heat
Coolant passage Water
Periodic removal and storage of radioactive wastes and spent fuel assemblies
Hot water output
Useful electrical energy about 25%
Periodic removal and storage of radioactive liquid wastes
Condenser
Water source (river, lake, ocean)
Figure 9-14 Science: This water-cooled nuclear power plant, with a pressurized water reactor, pumps water under high pressure into its core where nuclear fission takes place. Some nuclear plants withdraw the water they use from a nearby source such as a river and return the heated water to that source, as shown here. Other nuclear plants transfer the waste heat from the intensely hot water to the atmosphere by using one or more gigantic cooling towers. Question: How does this plant differ from the coal-burning plant in Figure 9-9?
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Nonrenewable Energy Resources
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Decommissioning of reactor
Fuel assemblies
Enrichment of UF6
Reactor Fuel fabrication (conversion of enriched UF6 to UO2 and fabrication of fuel assemblies)
Conversion of U3O8 to UF6
Temporary storage of spent fuel assemblies underwater or in dry casks
Uranium-235 as UF6 Plutonium-239 as PuO2 Spent fuel reprocessing
Low-level radiation with long half-life
Geologic disposal of moderateand high-level radioactive wastes
Mining uranium ore (U3O8)
Open fuel cycle today Recycling of nuclear fuel
Figure 9-15 Science: Using nuclear power to produce electricity involves a complex set of technologies and processes that make up the nuclear fuel cycle. As long as a reactor is operating safely, the power plant itself has a fairly low environmental impact and a very low risk of an accident. But costs are high, radioactive wastes must be stored safely for thousands of years, several points in the cycle are vulnerable to terrorist attack, and the technology can also be used to produce materials for use in nuclear weapons. Question: Do you think the market price of nucleargenerated electricity should include all the costs of the nuclear fuel cycle? Explain.
storing the resulting highly radioactive wastes, in the form of depleted, or spent, fuel rods, for thousands of years until their radioactivity falls to safe levels. The cycle also includes dismantling the extremely radioactive reactors at the end of their useful lives and safely storing their radioactive components for thousands of years. In evaluating the safety, economic feasibility, net energy yield, and overall environmental impact of nuclear power, energy experts and economists caution us to look at the entire nuclear fuel cycle, not just the operation of the power plant itself.
What Happened to Nuclear Power? In the 1950s, researchers predicted that by the year 2000, at least 1,800 nuclear power plants would supply 21% of the world’s commercial energy (25% in the United States) and most of the world’s electricity. After almost 60 years of development, enormous government subsidies, and a huge investment, these goals have not been met. In 2010, 436 commercial
nuclear reactors in 31 countries produced only 6% of the world’s commercial energy and 14% of its electricity. Nuclear power is now among the slowest-growing forms of commercial energy. In 2009, 104 licensed commercial nuclear power reactors in 31 states generated about 8% of the country’s overall energy and 19% of its electricity. This percentage is expected to decline over the next several decades as existing reactors wear out and are retired faster than new ones are built. The U.S. government has provided huge subsidies, tax breaks, and loan guarantees to the nuclear power industry. It also provides accident insurance guarantees, because insurance companies have refused to fully insure any nuclear reactor. Without these taxpayersubsidized payments, this industry would not exist in the United States or anywhere else. Another obstacle has been public concerns about the safety of nuclear reactors. Because of the multiple built-in safety features, the risk of exposure to GOOD radioactivity from nuclear power plants in the NEWS CONCEPT 9-5
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Trade-Offs Conventional Nuclear Fuel Cycle Adva nta ge s
Disad vant ag es
Low environmental impact (without accidents)
Very low net energy yield and high overall cost
Emits 1/6 as much CO2 as coal
Produces long-lived, harmful radioactive wastes
Low risk of accidents in modern plants
Promotes spread of nuclear weapons
Figure 9-16 Using the nuclear power fuel cycle (Figure 9-15) to produce electricity has advantages and disadvantages (Concept 9-5). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
United States and most other more-developed countries is extremely low. However, explosions and partial or complete meltdowns are possible, as we learned in 1986 from the serious accident at the Chernobyl nuclear plant in Ukraine (see the Case Study that follows). Figure 9-16 lists the major advantages and disadvantages of producing electricity by using the nuclear power fuel cycle (Concept 9-5). Following the next Case Study, we look more closely at some of the challenges involved in using nuclear power. ■ CAS E STUDY
Chernobyl: The World’s Worst Nuclear Power Plant Accident Chernobyl in Ukraine is known around the globe as the site of the world’s most serious nuclear power plant accident. On April 26, 1986, two simultaneous explosions in one of the four operating reactors in this nuclear power plant blew the massive roof off the reactor building. The reactor partially melted down and its graphite components caught fire and burned for 10 days. The initial explosion and the prolonged fires released a radioactive cloud that spread over much of Belarus, Russia, Ukraine, and Europe, and it eventually encircled the planet. According to UN studies, the Chernobyl disaster was caused by a poor reactor design and by human error, and it had serious consequences. By 2005, some 56 people had died prematurely from exposure to radiation released by the accident. The number of long-term premature deaths from the accident, primarily from exposure to radiation, range from 9,000 by World Health Organization estimates, to 212,000 as estimated by the Russian Academy of Medical Sciences. Because of poor record keeping and inadequate medical tracking, we will never know the actual death toll.
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After the accident, some 350,000 people had to abandon their homes because of contamination by radioactive fallout. In addition to fear about long-term health effects such as cancers, many of these victims continue to suffer from stress and depression. In parts of Ukraine, people still cannot drink the water or eat locally produced food. There are also higher incidences of thyroid cancer, leukemia, and immune system abnormalities in children exposed to Chernobyl’s radioactive fallout. Chernobyl taught us a hard lesson: A major nuclear accident anywhere has effects that reverberate throughout much of the world. One more major nuclear power accident anywhere in the world could have a devastating impact on the future of nuclear power.
Storing Spent Radioactive Fuel Rods Presents Risks After about 3 or 4 years, the high-grade uranium fuel in a nuclear reactor is spent and must be replaced. On a regular basis, reactors are shut down for refueling. This involves replacing about a third of the reactor’s fuel rods that contain the spent fuel. After the intensely hot and highly radioactive spent fuel rod assemblies are removed from a reactor, they are stored outside of the reactor building in water-filled pools, and after several years of cooling, in dry casks. These materials must be stored safely for many thousands of years, but the pools and casks are not nearly as well protected as the reactor core. Thus, they are much more vulnerable to acts of terrorism and other mishaps. Several governments have had the long-term goal of transporting spent fuel rods and other long-lived radioactive wastes to an underground facility for long-term storage. A 2005 study by the U.S. National Academy of Sciences warned that storage pools and dry casks at 68 nuclear power plants in 31 U.S. states are especially vulnerable to sabotage or terrorist attack. A 2002 study by the Institute for Resource and Security Studies and the Federation of American Scientists found that in the United States, about 161 million people—53% of the population—live within 121 kilometers (75 miles) of an aboveground spent-fuel storage site. For some time, critics have been calling for the immediate construction of much more secure structures to protect spent-fuel storage pools and dry casks, but so far, very little has been done to improve the safety and security of these sites. Currently, 60 countries—one of every three in the world—have nuclear weapons or the knowledge and ability to build them. The United States and 14 other countries have been selling nuclear reactors and uranium enrichment technology in the international marketplace for decades. Much of this information and equipment can be used to produce weapons-grade material. Some see this as the single most important reason for not expanding the use of nuclear power, especially when there are cheaper, quicker, and safer ways to produce electricity.
Nonrenewable Energy Resources
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Dealing with Radioactive Wastes Produced by Nuclear Power Is a Difficult Problem
large amounts of U.S. nuclear waste sit in pools and dry casks, mostly near reactors at scattered sites around the country, and these volumes of waste continue to grow.
Each part of the nuclear power fuel cycle produces radioactive wastes. High-level radioactive wastes consist mainly of spent fuel rods and assemblies from commercial nuclear power plants, the waste materials from dismantled plants, and assorted wastes from the production of nuclear weapons. They must be stored safely for 10,000 to 240,000 years, depending on the radioactive isotopes present. Most scientists and engineers agree in principle that deep burial in an underground repository is the safest and cheapest way to store this and other high-level radioactive waste. However, after almost 60 years of research and evaluation, no country has built and tested such a repository (see the Case Study that follows).
What Should We Do with Worn-out Nuclear Power Plants?
HOW WOULD YOU VOTE?
✓ ■
Should highly radioactive spent fuel be stored in casks at high-security sites at or near nuclear power plants instead of being shipped to a single site for burial? Cast your vote online at www.cengage.com/login.
■ CAS E S TUDY
High-Level Radioactive Wastes in the United States In 1987, the DOE announced plans to build a repository for underground storage of high-level radioactive wastes from commercial nuclear reactors. The proposed site was on federal land in the Yucca Mountain desert region, about 160 kilometers (100 miles) northwest of Las Vegas, Nevada. By 2008, the U.S. government had spent more than $10.4 billion on evaluation and preliminary development of the site with less that one-fifth of that cost paid by the nuclear industry and the rest paid by taxpayers. In 2008, the total cost of the repository was projected to be $96 billion, which would have added even more to the high cost of the nuclear power fuel cycle. Critics charged that the selection of the earthquakeprone Yucca Mountain site was based more on political convenience than on scientific suitability. Some scientists argued that the site should never be allowed to open, mostly because rock fractures and tiny cracks are likely to allow water to flow through the site. They warned that the buildup of hydrogen gas produced from the breakdown of this water by the intense heat of the stored waste materials would likely cause a major explosion. In 2009, President Barack Obama agreed with such criticisms and requested that the U.S. Congress cut off funding for the Yucca Mountain project while other, shorter-term alternatives are evaluated. Meanwhile,
When a nuclear power plant comes to the end of its useful life, mostly because of corrosion and radiation damage to its metal parts, it must be decommissioned, or retired—the last step in the nuclear power fuel cycle (Figure 9-15). Scientists have proposed three ways to do this. One strategy is to dismantle the plant after it is decommissioned and store its radioactive parts in a secure repository, which so far no country has built and tested. A second approach is to install a physical barrier around the plant and set up full-time security for 30–100 years, until the plant can be dismantled after its radioactivity has reached safer but still quite dangerous levels. A third option is to enclose the entire plant in a concrete and steel-reinforced tomb that must last and be monitored for several thousand years. Regardless of the method chosen, the high costs of retiring nuclear plants adds to the total costs of the nuclear power fuel cycle and reduces its already low net energy yield. Experience indicates that dismantling a plant and storing the resulting radioactive wastes costs 2–10 times more than building the plant in the first place. Some 285 of today’s 436 commercial nuclear reactors will reach the end of their useful lives by 2025, unless governments renew their operating licenses for another 20 years (as has happened for half of the 104 reactors operating in the United States). In 2010, only 47 new reactors were under construction, not even close to the number needed just to replace the reactors that will have to be decommissioned.
Can Nuclear Power Lessen Dependence on Imported Oil and Help Reduce Projected Climate Change? Some proponents of nuclear power in the United States claim it will help reduce the U.S. dependence on imported crude oil. Other analysts argue that it will not do so because oil-burning power plants provide only about 2% of the country’s electricity and similarly small shares in most other countries. Nuclear power advocates also contend that increased use of nuclear power will greatly reduce CO2 emissions and, in turn, reduce the projected threat of climate change. Scientists point out that while they are operating, nuclear plants do not emit CO2, but that large amounts are emitted during plant construction. Every CONCEPT 9-5
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other step in the nuclear power fuel cycle (Figure 9-15), especially in the manufacturing of many tons of construction cement, involves CO2 emissions. In 2007, the Oxford Research Group, an independent organization dedicated to promoting global security, said that in order for nuclear power to play an effective role in slowing projected atmospheric warming, the nuclear industry would have to build a new reactor somewhere in the world every week for the next 70 years. The current rate of reactor construction is nowhere near this estimate. In addition, a new repository like the now-abandoned Yucca Mountain site in the United States would have to be built every few years, at great cost, to store the amount of nuclear waste that would result from building such a large number of nuclear reactors.
Are New-Generation Nuclear Reactors the Answer? Partly to address economic and safety concerns, the U.S. nuclear industry has persuaded Congress to provide more large government subsidies and taxpayerguaranteed loans to help it build hundreds of smaller, new-generation plants using standardized designs. The industry claims these plants will be safer and can be built quickly (in 3–6 years). However, according to Nucleonics Week, an important nuclear industry publication, “Experts are flatly unconvinced that safety has been achieved—or even substantially increased—by the new designs.” In addition, these new designs do not eliminate the expense and hazards of long-term radioactive waste storage, threats of terrorist attack, power plant decommissioning, and the spread of knowledge and materials for the production of nuclear weapons.
Will Nuclear Fusion Save Us? Nuclear fusion is a nuclear change in which the nuclei of two isotopes of light elements such as hydrogen are forced together at extremely high temperatures until they fuse to form a heavier nucleus, releasing energy in the process. Some scientists hope that controlled nuclear fusion will provide an almost limitless source of intense heat and electricity. Research has focused on the D–T nuclear fusion reaction, in which two isotopes of hydrogen, deuterium (D) and tritium (T), fuse at about 100 million degrees (Figure 9-17). With nuclear fusion, there would be no risk of meltdown or release of large amounts of radioactive materials from a terrorist attack, and little risk of the additional spread of nuclear weapons, because bomb-grade materials are not required for fusion energy. Fusion power might also be used to destroy toxic wastes and to supply electricity for desalinating water. However, after more than 50 years of research and a $25 billion investment of mostly government funds, controlled nuclear fusion
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Reaction conditions
Fuel Proton
Neutron
Products Helium-4 nucleus
+ +
+ Hydrogen-2 (deuterium nucleus) 100 million °C
Energy
+ Hydrogen-3 (tritium nucleus)
Neutron
Nuclear fusion occurs when two isotopes of light elements, such as hydrogen, are forced together at extremely high temperatures until they fuse to form a heavier nucleus and release a tremendous amount of energy. Figure 9-17 The deuterium–tritium (D–T) nuclear fusion reaction takes place at extremely high temperatures.
is still in the laboratory stage. None of the approaches tested so far has produced more energy than they use. In 2006, the United States, China, Russia, Japan, South Korea, and the European Union agreed to spend at least $12.8 billion in a joint effort to build a large-scale experimental nuclear fusion reactor by 2040 in order to see if it can produce a net energy yield. If everything goes well, the experimental reactor is supposed to produce enough electricity to run the air conditioners in a small city for a few minutes. This helps to explain why many energy experts do not expect nuclear fusion to be a significant energy source any time in the near future. Indeed, some skeptics joke that “nuclear fusion is the power of the future and always will be.”
Experts Disagree about the Future of Nuclear Power Proponents of nuclear power argue that governments should continue funding research, development, and pilot-plant testing of potentially safer and cheaper fission reactors, along with nuclear fusion. They say we need to keep these potentially useful nuclear options available for use in the future, in case other energy options fail to keep up with electricity demands while reducing CO2 emissions to acceptable levels. Others analysts call for phasing out all or most government subsidies, tax breaks, and insurance and loan guarantees for nuclear power. They see nuclear power as a complex, expensive, and inflexible way to produce electricity. They argue that it carries unacceptable risks, because it is too vulnerable to sabotage and threatens global security by spreading knowledge and materials that can be used to build nuclear weapons. According to many investors and World Bank economic analysts, nuclear power cannot compete in today’s increasingly open, decentralized, and unregulated energy market, unless it is shielded from compe-
Nonrenewable Energy Resources
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tition by government subsidies (as is the case in every country that has nuclear power plants). Both the U.S. Congressional Budget Office and the private investment firm Standard and Poors have concluded that investing in loans to build nuclear power plants represents an unacceptable risk. Opponents of nuclear power say it makes better sense to invest government funds in spurring the more rapid development of energy efficiency and renewable energy resources that are much safer and can be developed more quickly. We explore these options in Chapter 10. HOW WOULD YOU VOTE?
✓ ■
Should nuclear power be phased out in the country where you live over the next 20–30 years? Cast your vote online at www.cengage.com/login.
Nonrenewable Energy Use Violates the Principles of Sustainability Using nonrenewable fossil fuels and nuclear power results in serious long-term problems, primarily because in doing so, we violate the three principles of
sustainability (see back cover). We depend not on solar energy but on technologies that disrupt the earth’s chemical cycles by emitting large quantities of pollutants and greenhouse gases. Using these technologies also degrades large land areas, results in severe air and water pollution, and promotes atmospheric warming leading to climate disruption, which will in turn destroy and degrade biodiversity. In the next chapter, we will look at the advantages and disadvantages of reducing energy waste and relying more on renewable energy resources as ways to apply the three principles of sustainability. Here are this chapter’s three big ideas:
■ A key factor to consider in evaluating the usefulness of any energy resource is its net energy yield. ■ Conventional oil, natural gas, and coal are plentiful and have moderate to high net energy yields, but use of any of these fossil fuels produces a high environmental impact. ■ Nuclear power has a low environmental impact and a low accident risk, but high costs, public fear of accidents, long-lived radioactive wastes, and the potential for spreading nuclear weapons technology have limited its use.
Civilization as we know it will not survive unless we can find a way to live without fossil fuels. DAVID GOLDSTEIB
REVIEW 1. Review the Key Questions and Concepts for the chapter on p. 187. Define commercial energy. What major energy resources do the world and the United States rely on? What is net energy and why is it important in evaluating energy resources? Define net energy ratio and explain why it is high for oil and low for nuclear power? 2. What is crude oil (petroleum) and how is it extracted from the earth and refined? Define peak production. What is a petrochemical and why are such chemicals important? Who controls most of the world’s oil supply? What percentage of the world’s proven oil reserves does the United States have? How much of the world’s annual oil production does the United States use and what percentage of the oil it uses is imported? About how much of the world and U.S. demand would be met by the oil in Alaska’s Arctic National Wildlife Refuge? What are the major advantages and disadvantages of using conventional oil as an energy resource? 3. What is tar sand, or oil sand, and how is it extracted and converted to heavy oil? What is shale oil and how is it
produced? What are the major advantages and disadvantages of using heavy oils produced from tar sand and oil shales as energy resources? 4. Define natural gas, liquefied petroleum gas (LPG), and liquefied natural gas (LNG). What are the major advantages and disadvantages of using conventional natural gas as an energy resource? 5. What is coal and how is it formed? Describe two estimates for how long the U.S. coal reserves could last. Describe the growing problem of coal ash. What are the major advantages and disadvantages of using coal as an energy resource? 6. What is synthetic natural gas (SNG) and how can it be produced from coal? What are coal gasification and coal liquefaction? How do synfuels compare with coal in terms of the resources required and carbon dioxide emitted? What are the major advantages and disadvantages of using liquid and gaseous synfuels produced from coal?
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7. Define nuclear fission. What is a chain reaction? Define radioisotope (radioactive isotopes), and explain how exposure to the products of nuclear fission can harm human cells. 8. How does a nuclear fission reactor work and what are its major safety features? Describe the nuclear fuel cycle. What factors greatly slowed the development of nuclear power? Describe the nuclear power plant accident at the Chernobyl plant in Ukraine. What are the major advantages and disadvantages of relying on nuclear power as a way to produce electricity? Summarize the risks of generating electricity by using nuclear power plants.
9. Describe the controversy over disposal of highly radioactive wastes in the United States. What are our options for safely retiring worn out nuclear power plants? Discuss the question of whether nuclear power can reduce dependence on imported oil and also help slow projected climate change. What is nuclear fusion and what is its potential as an energy resource? Summarize the disagreements over whether we should rely more on nuclear power. 10. Does use of nonrenewable energy resources conform to the three principles of sustainability? Explain.
Note: Key terms are in bold type.
CRITICAL THINKING 1. If the commercial energy currently sold represents a tiny fraction of the total energy used by humans (with the larger part being direct and indirect solar energy), do you think the commercial energy sector of the business world could survive if all fossil fuels suddenly ran out tomorrow? If you were an energy company executive, what strategy would you use to deal with such a disruption of your business? 2. Explain why you are for or against continuing to increase oil imports in the United States or in the country where you live. If you favor reducing dependence on oil imports, what do you think are the three best ways to do this? 3. Some people in China point out that the United States and European nations fueled their economic growth in the industrial revolution by burning coal, with little effort to control the resulting air pollution, and then trying to clean up its effects later when they became more affluent. China says it is being asked to clean up before it becomes affluent enough to do this without greatly slowing its economic growth. How would you deal with this contradiction? Since China’s air pollution has implications for the entire world, what role, if any, should the more-developed
nations play in helping China to reduce its dependence on coal and to burn coal more cleanly and efficiently? 4. Explain why you agree or disagree with the following proposals made by various energy analysts as ways to solve U.S. energy problems: a. Find and develop more domestic supplies of oil. b. Place a heavy federal tax on gasoline and imported oil to help reduce the waste of oil resources. c. Increase dependence on coal. d. Increase dependence on nuclear power. e. Phase out all nuclear power plants by 2025. 5. Would you favor having high-level nuclear waste from nuclear power plants transported by truck or train through the area where you live to a centralized underground storage site? Explain. What are the options? 6. Congratulations! You are in charge of the world. List the three most important features of your policy to develop nonrenewable energy resources during the next 50 years. 7. List two questions that you would like to have answered as a result of reading this chapter.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 9 for many study aids and ideas for further
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reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
Nonrenewable Energy Resources
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Energy Efficiency and Renewable Energy
10
Key Questions and Concepts 10-1 Why is energy efficiency an important energy source?
gain in atmospheric greenhouse gases, and creating biomass plantations can degrade soil and biodiversity.
Energy efficiency improvements could save the world at least a third of the energy it uses; they could save the United States up to 43% of the energy it uses.
CONCEPT 10-1
What are the advantages and disadvantages of using solar energy? 10-2
C O N C E P T 1 0 - 5 B We can use liquid biofuels derived from biomass in place of gasoline and diesel fuels, but creating biofuel plantations can degrade soil and biodiversity, and increase food prices and greenhouse gas emissions.
What are the advantages and disadvantages of using geothermal energy?
10-6
We can use passive and active solar heating systems to heat water and indoor spaces, and we can use direct sunlight to produce high-temperature heat and electricity, but such systems can be costly and they do require backups.
CONCEPT 10-2
10-3 What are the advantages and disadvantages of using hydropower? We can use water flowing over dams as well as the energy of tidal flows and ocean waves to generate electricity, but environmental concerns and limited availability of suitable sites may restrict our use of these energy resources.
CONCEPT 10-3
What are the advantages and disadvantages using wind power?
10-4
C O N C E P T 1 0 - 4 When the environmental costs of energy resources are included in market prices, wind energy is the least expensive and least polluting way to produce electricity, although it requires more power lines and a backup energy source.
C O N C E P T 1 0 - 6 Geothermal energy has great potential for supplying many areas with heat and electricity, and it has a generally low environmental impact, but the sites where we can use it economically are limited.
10-7 What are the advantages and disadvantages of using hydrogen as an energy source? Hydrogen fuel holds great promise for powering cars and generating electricity, but in order for it to be environmentally beneficial, we would have to produce it without the use of fossil fuels.
CONCEPT 10-7
10-8 How can we make the transition to a more sustainable energy future? C O N C E P T 1 0 - 8 We can make the transition to a more sustainable energy future by greatly improving energy efficiency, using a mix of renewable energy resources, and including the environmental costs of all energy resources in their market prices.
10-5 What are the advantages and disadvantages of using biomass as an energy source? Solid biomass is a renewable resource, but burning it faster than it is replenished produces a net
CONCEPT 10-5A
Just as the 19th century belonged to coal and the 20th century to oil, the 21st century will belong to the sun, the wind, and energy from within the earth. LESTER R. BROWN
Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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10-1 Why Is Energy Efficiency
an Important Energy Resource? ▲
C O NC EPT 10-1 Energy efficiency improvements could save the world at least a third of the energy it uses; they could save the United States up to 43% of the energy it uses.
We Waste Huge Amounts of Energy We can think of energy conservation, the energy we save by cutting energy waste, as a largely untapped, abundant, clean, and cheap source of energy. The best way to cut energy waste is to improve energy efficiency: the measure of how much work we can get from each unit of energy we use. Each unit of energy saved eliminates the need to produce that energy, and it saves us money. For example, according to the U.S. Department of Energy, roughly 84% of all commercial energy used in the United States is wasted (Figure 10-1). About 41% of this energy is unavoidably lost because of the degradation of energy quality imposed by the second law of thermodynamics (see Chapter 2, p. 30). The other 43% is wasted unnecessarily, mostly due to the inefficiency of many devices and processes that we use. Energy efficiency in the United States has improved during recent decades, but unnecessary energy waste Energy Inputs
System
still costs the United States a great deal of money. Energy analyst Amory Lovins estimates that in the United States “we could save at least half the oil and gas and three-fourths of the electricity we use at a cost of only about an eighth of what we’re now paying for these forms of energy.” Thus, reducing energy has economic as well as environmental advantages (Figure 10-2). To most energy analysts, reducing energy waste is the quickest, cleanest, and usually cheapest way to provide more energy, reduce pollution and environmental degradation, slow climate change, and increase economic and national security. For example, here are just four widely used devices that waste large amounts of energy: •
The incandescent lightbulb uses only 5–10% of the electricity it draws to produce light, while the other 90–95% is wasted as heat.
Solutions
Outputs 9% 7%
Reducing Energy Waste Prolongs fossil fuel supplies
41% 85%
U.S. economy
Reduces oil imports and improves energy security
Very high net energy yield
43%
Low cost
8% 4% 3%
Reduces pollution and environmental degradation
Useful energy Petrochemicals Unavoidable energy waste Unnecessary energy t Figure 10-1 This diagram shows how commercial energy flows through the U.S. economy. Only 16% of all commercial energy used in the United States ends up performing useful tasks; the rest of the energy is unavoidably wasted because of the second law of thermodynamics (41%) or is wasted unnecessarily (43%). Question: What are two examples of unnecessary energy waste? (Data from U.S. Department of Energy) Nonrenewable fossil fuels Nonrenewable nuclear Hydropower, geothermal, wind, solar Biomass
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Buys time to phase in renewable energy
Creates local jobs
Figure 10-2 Reducing unnecessary energy waste and thereby improving energy efficiency saves us money and reduces our ecological footprint. Questions: Which two of these advantages do you think are the most important? Why?
Energy Efficiency and Renewable Energy
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•
The internal combustion engine, used in most motor vehicles, wastes about 80% of the energy in its fuel.
•
A nuclear power plant used to produce electricity wastes about 75% of the energy in its nuclear fuel, and probably closer to 92% when we consider the energy used to deal with its radioactive wastes and to retire and close up, the highly radioactive plant.
•
A coal-fired power plant wastes about 66% of the energy that is released by burning coal to produce electricity, and probably 75–80% if we include the energy used to mine and transport the coal and to transport and store the toxic coal ash.
Some energy efficiency experts consider these technologies to be energy-wasting dinosaurs, and they call for us to use our scientific and engineering brainpower to replace them with more energy-efficient and less environmentally harmful alternatives over the next few decades.
We Can Save Energy and Money in Industry and Utilities Industry accounts for about 30% of the world’s energy consumption and 33% of U.S. consumption, mostly for production of metals, chemicals, petrochemicals, cement, and paper. There are many ways for industries to cut energy waste. Some companies save energy and money by GOOD using cogeneration, or combined heat and NEWS power (CHP) systems. In such a system, two useful forms of energy (such as steam and electricity) are produced from the same fuel source. The energy efficiency of these systems is 75–90% (compared to 30–40% for coal-fired boilers and nuclear power plants), and they
emit one-third as much climate-changing carbon dioxide (CO2) per unit of energy produced as do conventional coal-fired boilers. Another way to save energy and money in industry is to replace energy-wasting electric motors, which use onefourth of the electricity produced in the United States and 65% of the electricity used in U.S. industry. Most of these motors are inefficient because they run only at full speed with their output throttled to match the task—somewhat like keeping one foot on the gas pedal of your car and the other on the brake pedal to control its speed. Replacing them with variable speed motors, which run at the minimum rate needed for each job, saves energy and reduces the environmental impact of electric motor use. Recycling materials such as steel and other metals is a third way for industry to save energy and money. For example, producing steel from recycled scrap iron uses 75% less energy than producing steel from virgin iron ore and emits 40% less CO2. Switching three-fourths of the world’s steel production to such furnaces would cut energy use in the global steel industry by almost 40% and would sharply reduce its CO2 emissions. A fourth way for industry to save energy is to switch from low-efficiency incandescent lighting to higher-efficiency fluorescent lighting. A compact fluorescent bulb uses onefourth as much electricity as an incandescent bulb and can last ten times as long, saving at least $30 in replacement costs during its lifetime. Even better, light-emitting diodes (LEDs) use about one-seventh of the electricity required by an incandescent bulb and can last about 100 times longer. There is also a great deal of energy waste in the generation and transmission of electricity to industries and communities. The Science Focus below summarizes one important way in which we could cut some of this waste.
S C I E NC E FO C U S Saving Energy and Money with a Smarter Electrical Grid
G
rid systems of high-voltage transmission lines carry electricity from power plants, wind turbines, and other electricity producers to users. Many energy experts place top priority on converting and expanding the outdated U.S. electrical grid system into what they call a smart grid. This energy-efficient, digitally controlled, ultra-high-voltage grid with superefficient transmission lines would be responsive to local and regional changes in demand and supply. A smarter electrical grid would involve a two-way flow of energy and information between producers and users of electricity. Such a system would use smart meters to monitor the amount of electricity used
and the patterns of use for each customer. It would then use this information to deliver electricity as efficiently as possible. Smart meters would also show consumers how much energy they are using by the minute and for each appliance. This information would help them to reduce their power consumption and power bills. Smart appliances such as clothes washers and dryers could be programmed to perform their tasks during off-peak hours when electricity is cheaper. A smart grid could allow individuals to run their air conditioners remotely so that they could leave them off when they are not at home and turn them on before they return. With such a system, customers who use solar
cells, wind turbines, or other devices to generate some of their own electricity could cut their bills by selling their excess electricity to utility companies. According to the U.S. Department of Energy (DOE), building such a grid would cost the United States from $200 billion to $800 billion, but would pay for itself in a few years by saving the U.S. economy more than $100 billion a year. Critical Thinking Would you support a substantial government (taxpayer) investment of funds to build a smart grid? Explain.
CONCEPT 10-1 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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We Can Save Energy and Money in Transportation
of higher medical bills and health insurance premiums. Consumers pay for these hidden costs, but not at the gas pump.
30 Cars 25 20
Trucks
15 10 1975
1980
1985
1990
More Energy-Efficient Vehicles Are on the Way There is growing interest in developing superef- GOOD ficient, ultralight, and ultrastrong cars that could NEWS get up to130 kilometers per liter (kpl) (300 miles per gallon, or mpg) One of these vehicles is the energyefficient, gasoline–electric hybrid car (Figure 10-4, left). It has a small, traditional gasoline-powered engine and a battery-powered electric motor used to provide the energy needed for acceleration and hill climbing. Current models of these cars get up to 21 kpl (50 mpg). The next step in the evolution of more energy-efficient motor vehicles will probably be the plug-in hybrid electric vehicle—a hybrid with a second and more powerful battery that can be plugged into a conventional electrical outlet and recharged (Figure 10-4, right). By running primarily on electricity, plug-in hybrids could easily get the equivalent of at least 43 kpl (100 mpg) for ordinary driving and up to 430 kpl (1,000 mpg), if used only for trips of less than 32 kilometers (40 miles) before recharging. A Chinese company is now selling the world’s first plug-in hybrid, called the Build Your Dreams (BYD) car. American manufacturers plan to have a variety of plug-in hybrids available by 2012. Another option is an energy-efficient diesel car, which accounts for 45% of new passenger car sales in Europe. Newer diesel engines have very low emissions, are quiet, and are about 30% more fuel efficient than comparable internal combustion engines. Running these vehicles on a fuel called biodiesel, discussed later in this
Miles per gallon (mpg) (converted to U.S. test equivalents)
Average fuel economy (miles per gallon)
There is a lot of room for reducing energy waste in transportation, which accounts for about 28% of the energy consumption and two-thirds of the oil consumption in the United States. One problem has been that U.S. government fuel efficiency standards for motor vehicles have been generally low for many years. Since 1985, despite government-mandated corporate average fuel economy (CAFE) standards, the average fuel efficiency for new vehicles has generally declined while standards and efficiencies in other countries rose (Figure 10-3). In 2010, partly because of low CAFE standards, more than half of all U.S. consumers owned SUVs, pickup trucks, minivans, and other large, inefficient vehicles. One reason for this is that the inflation-adjusted price of gasoline is still fairly low—costing less per liter than bottled water—compared to much higher costs in Japan and most European nations. Another reason is that most U.S. consumers do not realize that gasoline costs them much more than the price they pay at the pump. According to a 2005 study by the International Center for Technology Assessment, the hidden costs of gasoline for U.S. consumers were about $3.18 per liter ($12 per gallon). Adding this to an $.80 per liter ($3 per gallon) pump price of gasoline for U.S. consumers would yield a true cost of about $4 per liter ($15 per gallon). These hidden costs include government subsidies (payments intended to help businesses survive) and tax breaks for oil companies, car manufacturers, and road builders and the costs of pollution control and cleanup, military protection of oil supplies in the Middle East, and time wasted in traffic jams. Also hidden are the costs of illness from air and water pollution in the form
1995 Year
2000
2005
2010
50 45
Europe
40
Japan China
35
Canada
30 25 20 2002
United States 2004
2006
2008
Year
Figure 10-3 This diagram shows changes in the average fuel economy of new vehicles sold in the United States, 1975–2008 (left) and the fuel economy standards in other countries, 2002–2008 (right). (U.S. Environmental Protection Agency, National Highway Traffic Safety Administration, and International Council on Clean Transportation)
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Energy Efficiency and Renewable Energy
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Conventional hybrid
Fuel tank
Plug-in hybrid
Fuel tank
Battery
Battery
Internal combustion engine
Internal combustion engine Transmission
Electric motor
Transmission
Electric motor
Figure 10-4 Solutions: A hybrid gasoline–electric engine (left) has a small internal combustion engine and a battery. A plug-in hybrid vehicle (right) has a smaller internal combustion engine with a second and more powerful battery that can be plugged into a standard 110-volt outlet and recharged. This allows it to run farther on electricity alone.
chapter, would reduce their air pollution emissions and increase energy efficiency. Eventually, electric vehicles may be using fuel cells, which are at least twice as efficient as internal combustion engines. Fuel cells have no moving parts, require little maintenance, and use hydrogen gas as fuel to produce electricity. This would essentially eliminate emissions of CO2 and other air pollutants if the hydrogen was produced from noncarbon or low-carbon renewable sources of electricity such as wind turbines and solar cells. But such cars are unlikely to be widely available until 2020 or later and will probably be very expensive because they have a negative net energy yield. The fuel efficiency for all types of cars could nearly double if car bodies were made of ultralight and ultrastrong composite materials such as fiberglass and the carbon-fiber composites used in bicycle helmets and in some racing cars.
We Can Design Buildings That Save Energy and Money The buildings in which we live and work also GOOD consume and waste huge amounts of energy. NEWS According to a 2007 UN study, better architecture and energy savings in buildings could reduce the energy used globally by 30–40%. For example, the 24-story Georgia Power Company building in the U.S. city of Atlanta, Georgia, uses 60% less energy than conventional office buildings of the same size. The largest surface of this building faces south to capture as much solar energy as possible. Each floor extends out over the one below it. This blocks out the higher summer sun on each floor to reduce air conditioning costs but allows the lower winter sun to help
light and heat each floor during the day. In the building’s offices, energy-efficient compact fluorescent lights focus on work areas instead of illuminating entire rooms. Green architecture, based on energy-efficient and money-saving designs, makes use of natural lighting, solar energy, recycling of wastewater, and energyefficient appliances and lighting. Some green buildings have living roofs, or green roofs, covered with soil and vegetation, which helps to keep the buildings warmer in winter and cooler in summer. Another important element of energy-efficient design is superinsulation. A house can be so heavily insulated and airtight that heat from direct sunlight, appliances, and human bodies can warm it with little or no need for a backup heating system. Such houses typically cost more to build than conventional houses of the same size, but the cost is paid back within years by energy savings. Superinsulated houses in Sweden use 90% less energy for heating and cooling than typical American homes of the same size use.
We Can Save Money and Energy in Existing Buildings There are many ways to save energy and money GOOD in existing buildings. Surveys of energy use in NEWS older houses typically result in some or all of the following recommendations: •
Insulate the building and plug leaks. About one-third of the heated air in typical U.S. homes and other buildings escapes through holes, cracks, and closed, single-pane windows. During hot weather, these windows and cracks let heat in, increasing the use of air conditioning. Adding insulation to walls and attics, plugging air leaks, and sealing heating and cooling CONCEPT 10-1
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ducts are three of the quickest, cheapest, and best ways to save money and energy in any building. •
•
Use energy-efficient windows. Replacing single-pane windows with energy-efficient double-pane windows or highly efficient superwindows that have the insulating effect of a window with three or more panes can cut heat losses from a house by two-thirds, lessen cooling costs in the summer, and reduce heating-system CO2 emissions. Heat houses more efficiently. In order, the best ways to improve efficiency in space heating are to use: superinsulation; a geothermal heat pump that transfers heat stored in the earth to a home; passive solar heating; a high-efficiency, conventional heat pump (in warm climates only); small, cogenerating microturbines fueled by natural gas; and a highefficiency (92–98%) natural gas furnace. The most wasteful and expensive way to heat a space is to use electric resistance heating with electricity from a conventional power plant.
•
Heat water more efficiently. One approach is to use a roof-mounted solar hot water heater. Another option is a tankless instant water heater fired by natural gas or LPG. It heats water instantly as it flows through a small burner chamber, providing hot water only when it is needed, and uses less energy than traditional water heaters.
•
Use energy-efficient appliances and lighting. According to the U.S. Environmental Protection Agency (EPA), if all U.S. households used the most efficient frost-free refrigerator now available, 18 large power plants could close. Microwave ovens use 25–50% less electricity than electric stoves do for cooking and 20% less than convection ovens use. Clothes dryers with moisture sensors cut energy use by 15%. The best compact fluorescent lightbulbs are four times more efficient and last up to ten times longer than incandescent bulbs.
Figure 10-5 summarizes ways in which you can save energy in the place where you live.
Attic • Hang reflective foil near roof to reflect heat.
Outside Plant deciduous trees to block summer sun and let in winter sunlight.
• Use house fan. • Be sure attic insulation is at least 30 centimeters (12 inches). Bathroom • Install water-saving toilets, faucets, and shower heads. • Repair water leaks promptly. Kitchen • Use microwave rather than stove or oven as much as possible. • Run only full loads in dishwasher and use low- or no-heat drying. • Clean refrigerator coils regularly.
Basement or utility room • Use front-loading clothes washer. If possible run only full loads with warm or cold water. • If possible, hang clothes on racks for drying. Figure 10-5 Individuals matter: You can save energy where you live. Question: Which of these things do you do?
210
• Run only full loads in clothes dryer and use lower heat setting.
Other rooms • Use compact fluorescent lightbulbs or LEDs and avoid using incandescent bulbs. • Turn off lights, computers, TV, and other electronic devices when they are not in use. • Use high efficiency windows; use insulating window covers and close them at night and on sunny, hot days. • Set thermostat as low as you can in winter and as high as you can in summer. • Weather-strip and caulk doors, windows, light fixtures, and wall sockets. • Keep heating and cooling vents free of obstructions.
• Set water heater at 140°F if dishwasher is used and 120°F or lower if no dishwasher is used. • Use water heater thermal blanket. • Insulate exposed hot water pipes.
• Keep fireplace damper closed when not in use. • Use fans instead of, or along with, air conditioning.
• Regularly clean or replace furnace filters.
CHAPTER 10
Energy Efficiency and Renewable Energy
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Why Are We Still Wasting So Much Energy and Money?
We Can Use Renewable Energy to Provide Heat and Electricity
With such an impressive array of benefits, why is there so little emphasis on improving energy efficiency? One reason is that fossil fuels and nuclear power are artificially cheap because of the government subsidies and tax breaks they receive and because their market prices do not include their harmful environmental and health costs. As a result, people are more likely to waste energy and less likely to invest in improving energy efficiency. Another reason is that there are few tax breaks, rebates, and other economic incentives for consumers and businesses for investing in energy-efficiency improvements. Also, the U.S. federal government has done a poor job of encouraging fuel efficiency in motor vehicles (Figure 10-3) and educating the public about the advantages of cutting energy waste. Another problem is that people have perceived energy efficiency as something that requires a change in lifestyle, when in fact it can simply mean living with less waste and saving money.
One of nature’s three principles of sustainability (see back cover) is to rely mostly on solar energy. We can get renewable solar energy directly from the sun or indirectly from wind and moving water, as well as from burning wood and other forms of biomass, none of which would exist without direct solar energy. Another form of renewable energy is geothermal energy from the earth’s interior. Studies show that with increased and consistent government back- GOOD ing, renewable energy could provide 20% of the NEWS world’s electricity by 2025 and 50% by 2050. If renewable energy is so great, why does it provide only 15% of the world’s energy and 7% of the energy used in the United States? One reason is that since 1950, government tax breaks, subsidies, and research and development funding for renewable energy resources have been much lower than those for fossil fuels and nuclear power, although subsidies and tax breaks for renewables have increased in recent years. Another reason is that the prices we pay for nonrenewable fossil fuels and nuclear power do not include their harmful environmental and health costs. Energy analysts say that if these economic handicaps—inequitable subsidies and inaccurate pricing—were eliminated, many forms of renewable energy would be cheaper than fossil fuels and nuclear energy, and would quickly take over the marketplace.
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Should the country where you live greatly increase its emphasis on improving energy efficiency to cut energy waste and save money? Cast your vote online at www.cengage .com/login.
10-2 What Are the Advantages and
Disadvantages of Using Solar Energy? ▲
CONC EPT 10-2 We can use passive and active solar heating systems to heat water and indoor spaces, and we can use direct sunlight to produce high-temperature heat and electricity, but such systems can be costly and they do require backups.
We Can Heat Buildings and Water with Solar Energy We can heat buildings and water with passive and active solar heating systems (Concept 10-2) (Figure 10-6, p. 212). A passive solar heating system absorbs and stores heat from the sun directly within a structure without the need for pumps or fans to distribute the heat (Figure 10-6, left). Energy-efficient windows or attached greenhouses face the sun to collect solar energy directly. Walls and floors of concrete, adobe, brick, stone, or salttreated timber, and metal or plastic water tanks can store much of the collected solar energy as heat and
release it slowly throughout the day and night. A small backup heating system such as a vented natural gas or propane heater may be used, but is not necessary in many climates. An active solar heating system (Figure 10-6, right) absorbs energy from the sun by pumping a heatabsorbing fluid (such as water or an antifreeze solution) through special collectors, usually mounted on a roof or on special racks to face the sun. Some of the collected heat can be used directly. The rest can be stored in a large insulated container filled with gravel, water, clay, or a heat-absorbing chemical, for release as needed. Figure 10-7 (p. 212) lists the major advantages and disadvantages of using passive or active solar heating CONCEPT 10-2
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211
Summer sun
White or light-colored roofs reduce overheating
Vent allows hot air to escape in summer
White or light-colored roofs reduce overheating
Solar collector
Heat to house (radiators or forced air duct)
Heavy insulation
Winter sun
Pump Heavy insulation
Superwindow
Superwindow
Superwindow Hot water tank
Heat exchanger
Stone floor and wall for heat storage
ACTIVE
PASSIVE Figure 10-6 Solutions: We can heat homes with passive or active solar systems.
systems for heating indoor spaces. They can be used to heat new homes in areas with adequate sunlight. But solar energy cannot be used to heat existing homes that are not oriented to receive sunlight or that are blocked from sunlight by other buildings or trees. We can also use active solar collectors to provide hot water. Inexpensive rooftop solar water heaters are widely used in China, Germany, Japan, Greece, Austria, and Turkey. In Israel and Spain, all new buildings are required by law to have rooftop systems for heating water and indoor spaces.
Trade-Offs Passive or Active Solar Heating Adva nta ge s
Disad vant ag es
Net energy is moderate (active) to high (passive)
Need access to sun 60% of time during daylight
Very low emissions of CO2 and other air pollutants
Sun can be blocked by trees and other structures
Very low land disturbance
High installation and maintenance costs for active systems
Moderate cost (passive)
Need backup system for cloudy days
Figure 10-7 Heating a house with a passive or active solar energy system has advantages and disadvantages (Concept 10-2). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
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We Can Concentrate Sunlight to Produce High-Temperature Heat and Electricity Solar thermal systems use different methods to collect and concentrate solar energy in order to boil water and produce steam for generating electricity. These systems are used mostly in desert areas with ample sunlight. Figure 10-8 summarizes some advantages and disadvantages of concentrating solar energy to produce hightemperature heat or electricity (Concept 10-2). One method uses a central receiver system, such as that shown in the top drawing in Figure 10-8. In very large systems, the central receiver is called a power tower. Huge arrays of computer-controlled mirrors called heliostats track the sun and focus sunlight on this central heat collection tower. In another type of system, sunlight is collected and focused on oil-filled pipes running through the middle of a large area of curved solar collectors (bottom drawing, Figure 10-8). This concentrated sunlight can generate temperatures high enough to produce steam for running turbines and generating electricity. A 2009 study by environmental and industry GOOD groups estimated that solar thermal power plants NEWS could meet up to 25% of the world’s projected electricity needs by 2050. German scientists estimate that coupling an array of solar thermal power plants in North Africa with a new smart grid (Science Focus, p. 207) could meet all of Europe’s electricity needs. People use concentrated solar energy on a smaller scale, as well. In some sunny rural areas, inexpensive solar cookers focus and concentrate sunlight for cooking food and sterilizing water. A solar cooker can be built inexpensively and can replace wood fires, thereby helping to reduce deforestation from fuelwood harvesting.
Energy Efficiency and Renewable Energy
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Trade-Offs Solar Energy for High-Temperature Heat and Electricity Adva nta ge s
Disad vant ag es
Moderate environmental impact
Low net energy and high costs
No direct emissions of CO2 and other air pollutants
Lower costs with natural gas turbine backup
Needs backup or storage system on cloudy days
High water use for cooling
They also save the time and labor needed to collect firewood and they reduce indoor air pollution and premature deaths from smoky indoor fires.
We Can Use Sunlight to Produce Electricity We can convert solar energy directly into electrical energy using photovoltaic (PV) cells, commonly called solar cells (Figure 10-9). Most solar cells are thin wafers of purified silicon. A typical solar cell has a thickness ranging from less than that of a human hair to that
Figure 10-8 Using solar energy to generate high-temperature heat and electricity has advantages and disadvantages (Concept 10-2). Questions: Which single advantage and which single disadvantage do you think are the most important? Why? Do you think that the advantages of using these technologies outweigh their disadvantages? Explain.
of a sheet of paper. When sunlight strikes these transparent cells, they emit electrons, and many cells wired together in a panel produce electrical power. These cells can be connected to batteries to store the electrical energy until it is needed, or they can be connected to existing electrical grid systems. Homeowners and businesses in many countries get paid for any excess electricity that they produce and feed back into the grid system. Solar cells have no moving parts, are safe and quiet, require little maintenance, produce no pollution or greenhouse gases during operation, and last as long as or longer than a conventional fossil fuel or nuclear power plant. The semiconductor material used in solar cells can be made into paper-thin rigid or flexible sheets that can be incorporated into traditional-looking roofing materials (Figure 10-9, right) and attached to walls, windows, and clothing. Easily expandable banks of solar cells can be used in developing countries to provide electricity for many of the 1.6 billion people who live in rural villages. With financing from the World Bank, India is installing solarcell systems in 38,000 villages that are located long distances from power grids. One of the largest solar-cell
Solar-cell roof Martin Bond/Peter Arnold, Inc.
Single solar cell
– Boronenriched silicon
+
Junction Phosphorusenriched silicon
Roof options Panels of solar cells
Solar shingles
Figure 10-9 Solutions: Photovoltaic (PV) or solar cells can provide electricity for a house or other building using solar-cell roof shingles, as shown in this house in Richmond Surrey, England. Solar-cell roof systems that look like a metal roof are also available. In addition, new thin-film solar cells can be applied to windows and outside walls.
CONCEPT 10-2 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Figure 10-10 Using solar cells to produce electricity has advantages and disadvantages (Concept 10-2). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Trade-Offs Solar Cells
systems went on line in 2007 in Portugal. On a sunny day, it generates enough electricity to power 8,000 homes. In 2009, the three largest producers of solar-cell electricity were Japan, China, and Germany. Figure 10-10 lists the advantages and disadvantages of solar cells (Concept 10-2). Until recently the main problem with using solar cells to produce electricity has been their high cost. Despite this drawback, production of solar cells has soared in recent years and they have become the world’s fastest-growing way to produce electricity. This is because of their advantages (Figure 10-10, left) and because of increased government subsidies and tax breaks for solar developers. Production is likely to keep growing because new, thin-film solar cells are rapidly becoming cheap enough to compete with fossil fuels and to make more expensive conventional solar-cell panels obsolete. Energy analysts say that with increased research and development, plus much greater and more consistent government tax breaks and other subsidies, solar cells could provide 16% of the world’s electricity by 2040. In 2007, Jim Lyons, chief engineer for General Electric, projected that solar cells will be the world’s number-one
A d vant ag es
D i s a d v a nt a g e s
Moderate net energy yield
Need access to sun
Little or no direct emissions of CO2 and other air pollutants
Need electricity storage system or backup
High costs for older systems but decreasing rapidly
Easy to install, move around, and expand as needed
Solar-cell power plants could disrupt desert ecosystems
Competitive cost for newer cells
source of electricity by the end of this century. If that happens, it will represent a huge global application of the solar energy principle of sustainability (see back cover). HOW WOULD YOU VOTE?
✓ ■
Should the country where you live greatly increase its dependence on solar cells for producing electricity? Cast your vote online at www.cengage.com/login.
10-3 What Are the Advantages and
Disadvantages of Using Hydropower? ▲
C O NC EPT 10-3 We can use water flowing over dams as well as the energy of tidal flows and ocean waves to generate electricity, but environmental concerns and limited availability of suitable sites may restrict our use of these energy resources.
We Can Produce Electricity from Flowing and Falling Water Hydropower is an indirect form of solar energy that uses the kinetic energy of flowing and falling water to produce electricity. The most common approach to harnessing hydropower is to build a high dam across a large river to create a reservoir. Some of the water stored in the reservoir is then allowed to flow through huge pipes at controlled rates and this water spins turbines that generate electricity. Hydropower is the world’s leading renewable energy source used to produce electricity. In 2007, hydropower
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supplied about 20% of the world’s electricity, including 99% of Norway’s, 75% of New Zealand’s, 59% of Canada’s, and 21% of China’s electricity. According to the United Nations, only about 13% of the world’s potential for hydropower has been developed. But some analysts expect that use of large-scale hydropower plants will fall slowly over the next several decades as many existing reservoirs fill with silt and become useless faster than new systems are built. Also, there is growing concern over emissions of methane, a potent greenhouse gas, from the decomposition of submerged vegetation in reservoirs, especially in warm climates.
Energy Efficiency and Renewable Energy
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Trade-Offs Large-Scale Hydropower Adva nta ge s
Disad vant ag es
Moderate to high net energy
Large land disturbance and displacement of people
Large untapped potential Low-cost electricity Low emissions of CO2 and other air pollutants in temperate areas
High CH4 emissions from rapid biomass decay in shallow tropical reservoirs Disrupts downstream aquatic ecosystems
Figure 10-11 Using large dams and reservoirs to produce electricity has advantages and disadvantages (Concept 10-3). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Figure 10-11 lists the advantages and disadvantages of using large-scale hydropower plants to produce electricity (Concept 10-3).
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The use of microhydropower generators may become an increasingly important way to produce electricity. These small floating turbines can be placed in any stream or river without altering its course to provide electricity at a very low cost with very low environmental impact. We can also produce electricity from flowing water by tapping into the energy from ocean tides and waves. In some coastal bays and estuaries, water levels can rise or fall by 6 meters (20 feet) or more between daily high and low tides. Dams have been built across the mouths of some bays and estuaries to capture the energy in these flows for hydropower. Underwater turbines can also tap the tidal flows. In addition, scientists and engineers have been trying for decades to produce electricity by tapping wave energy along seacoasts where wave action is almost continuous. Use of these systems is limited because there are few suitable sites for them. Also, their costs are high and the equipment is vulnerable to corrosion from saltwater and storm damage. However, the technologies are steadily improving.
10-4 What Are the Advantages and
Disadvantages of Using Wind Power? ▲
CONC EPT 10-4 When the environmental costs of energy resources are included in market prices, wind energy is the least expensive and least polluting way to produce electricity, although it requires more power lines and a backup energy source.
Using Wind to Produce Electricity Is an Important Step toward Sustainability The difference in solar heating between the earth’s equator and its poles, together with the earth’s rotation, creates flows of air called wind. We can capture this indirect form of solar energy with wind turbines that convert it into electrical energy (Figure 10-12, p. 216). Today’s wind turbines can be as tall as 22 stories, and they have very long blades, which allow them to tap into the stronger and more reliable winds found at higher altitudes. In recent years, wind power has been the GOOD world’s second-fastest-growing source of energy, NEWS after solar cells. In 2009, a Harvard University study led by Xi Lu estimated that wind power has the potential to produce 40 times the world’s current use of electric-
ity, assuming we would use a series of large wind farms located in sparsely populated areas of China, the United States, Canada, and a few other countries. Analysts expect to see increasing use of offshore wind farms because wind speeds over water are often stronger and steadier than those over land. Turbines could be anchored on floating platforms far enough from shore to be out of sight for coastal residents while taking advantage of offshore winds. Siting them offshore would also avoid complaints about noise that have been voiced by some people living near land-based wind farms. Wind is abundant and widely distributed, and wind power is mostly carbon-free and pollution-free. A wind farm can be built within 9 to 12 months and expanded as needed. The DOE and the Worldwatch Society also estimate that, when we include the harmful environmental and health costs of various energy resources in CONCEPT 10-4
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Gearbox Electrical generator
Power cable
Wind turbine
Wind farm
Wind farm (offshore)
Figure 10-12 Solutions: A single wind turbine (left) can produce electricity. Increasingly, they are interconnected in arrays of tens to hundreds of turbines. These wind farms or wind parks can be located on land (middle) or offshore (right). The land beneath these turbines can still be used to grow crops or to raise cattle. Questions: Would you object to having a wind farm located near where you live? Why or why not?
comparative cost estimates, wind energy is the cheapest way to produce electricity (Concept 10-4). Like any energy source, wind power has some drawbacks. Areas with the greatest wind power potential are often sparsely populated and located far from cities. Thus, to take advantage of the potential for electricity from wind energy, countries such as the United States will have to invest in upgrading and expanding their outdated electrical grid systems (see Science Focus, p. 207). The resulting increase in the number of transmission towers and lines will cause controversy in some areas. One way to deal with this problem could be to run many of the new lines along highway corridors to avoid legal conflicts and further land disruption. Wind power proponents argue that continuing to rely primarily on the use of polluting and climate-changing coal and oil is a far worse alternative that will also require more power lines. Another problem is that winds can die down and thus require a backup source of power, such as natural gas, for generating electricity. However, a large number of wind farms in different areas connected to an updated and smarter electrical grid could usually take up the slack when winds die down in any one area. Scientists are also working on ways to store wind energy. Some people in populated areas and in coastal areas oppose wind farms as being unsightly and noisy. But in windy parts of the U.S. Midwest and in Canada, many farmers and ranchers welcome them and some have become wind developers themselves. For each wind turbine located on a farmer’s land, the landowner typically receives $3,000 to $10,000 a year in royalties. In addition, that farmer can still use the land for growing crops or grazing cattle. Figure 10-13 lists the major advantages and disadvantages of using wind to produce electricity. Accord-
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ing to energy analysts, wind power has more benefits and fewer serious drawbacks than any other energy resource, except for energy efficiency. HOW WOULD YOU VOTE?
✓ ■
Should the country where you live greatly increase its dependence on wind power? Cast your vote online at www.cengage.com/login.
Trade-Offs Wind Power A d vant ag es
D i s a d v a nt a g e s
Moderate to high net energy yield
Needs backup or storage system when winds die down
Widely available Low electricity cost Little or no direct emissions of CO2 and other air pollutants Easy to build and expand
Will require more power lines Visual pollution and low-level noise bothers some people Can kill birds if not properly designed and located
Figure 10-13 Using wind to produce electricity has advantages and disadvantages (Concept 10-4). With sufficient and consistent government incentives, wind power could supply more than 10% of the world’s electricity and 20% of the electricity used in the United States by 2030. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Energy Efficiency and Renewable Energy
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10-5 What Are the Advantages and Disadvantages
of Using Biomass as an Energy Source? ▲
CONC EPT 10-5A
▲
CONC EPT 10-5B
Solid biomass is a renewable resource, but burning it faster than it is replenished produces a net gain in atmospheric greenhouse gases, and creating biomass plantations can degrade soil and biodiversity. We can use liquid biofuels derived from biomass in place of gasoline and diesel fuels, but creating biofuel plantations can degrade soil and biodiversity, and increase food prices and greenhouse gas emissions.
We Can Produce Energy by Burning Solid Biomass Biomass consists of plant materials (such as wood and agricultural waste) and animal wastes that we can burn directly as a solid fuel or convert into gaseous or liquid biofuels. Biomass is an indirect form of solar energy because it consists of combustible organic (carboncontaining) compounds produced by photosynthesis. Solid biomass is burned mostly for heating and cooking, but also for industrial processes and for generating electricity. Wood, charcoal made from wood, animal manure, and other forms of biomass used for heating and cooking supply 10% of the world’s energy, 35% of the energy used in less-developed countries, and 95% of the energy used in the poorest countries. Wood is a renewable fuel only if it is harvested no faster than it is replenished. The problem is, about 2.7 billion people in 77 less-developed countries face a fuelwood crisis and are often forced to meet their fuel needs by harvesting wood faster than it can be replenished.
Trade-Offs Solid Biomass Adva nta ge s
Disad vant ag es
Widely available in some areas
Moderate to high environmental impact
Moderate costs
Increases CO2 emissions if harvested and burned unsustainably
No net CO2 increase if harvested, burned, and replanted sustainably
Clear cutting can cause soil erosion, water pollution, and loss of wildlife habitat
Plantations can help restore degraded lands
Often burned in inefficient and polluting open fires and stoves
One way to deal with this problem is to produce solid biomass fuel by planting fast-growing trees (such as cottonwoods and poplars), shrubs, perennial grasses (such as switchgrass), and water hyacinths in biomass plantations. But repeated cycles of growing and harvesting these plantations can deplete the soil of key nutrients. Clearing forests and grasslands for such plantations also destroys or degrades biodiversity. In agricultural areas, crop residues (such as sugarcane residues, rice husks, cotton stalks, and coconut shells) and animal manure can be collected and burned or converted into biofuels. Some ecologists argue that it makes more sense to use animal manure as a fertilizer and to use crop residues to feed livestock as well as to hold the soil in place and to fertilize the soil. Figure 10-14 lists the general advantages and disadvantages of burning solid biomass as a fuel (Concept 10-5A). One problem is that burning biomass produces CO2. However, if the rate of use of biomass does not exceed the rate at which it is replenished by new plant growth, which takes up CO2, there is no net increase in CO2 emissions. HOW WOULD YOU VOTE?
✓ ■
Should we greatly increase our dependence on burning solid biomass to provide heat and produce electricity? Cast your vote online at www.cengage.com/login.
We Can Convert Plants and Plant Wastes to Liquid Biofuels Liquid biofuels such as biodiesel (produced from vegetable oils) and ethanol (ethyl alcohol produced from plants and plant wastes; see the Case Study that follows) are
Figure 10-14 Using solid biomass as a fuel has advantages and disadvantages (Concept 10-5A). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
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being used in place of petroleum-based diesel fuel and gasoline. The biggest producers of liquid biofuels, in order, are Brazil (mostly ethanol from sugarcane residues), the United States (mostly ethanol from corn), the European Union (mostly biodiesel from vegetable oils), and China (mostly ethanol from non-grain plant sources). Biofuels have three major advantages over gasoline and diesel fuel produced from oil. First, while oil resources are concentrated in a small number of countries, biofuel crops can be grown almost anywhere, and thus they help countries to reduce their dependence on imported oil. Second, if these crops are not used faster than they are replenished by new plant growth, there is no net increase in CO2 emissions, unless existing grasslands or forests are cleared to plant biofuel crops. Third, biofuels are available now, are easy to store and transport, can be distributed through existing fuel networks for use in motor vehicles. However, in a 2007 UN report on bioenergy, and in another study by R. Zahn and his colleagues, scientists warned that large-scale biofuel-crop farming could decrease biodiversity by increasing the clearing of natural forests and grasslands; increase soil degradation, erosion, and nutrient leaching; push small farmers off their land; and raise food prices if farmers can make more money by growing corn and other crops to make fuel for cars rather than to feed livestock and people (Concept 10-5B).
■ CAS E STUDY
Is Ethanol the Answer? Ethanol can be made from plants such as sugarcane, corn, and switchgrass, and from agricultural, forestry, and municipal wastes. This process involves converting plant starches into simple sugars, which are processed to produce ethanol. Brazil, the “Saudi Arabia of sugarcane,” is the world’s second largest ethanol producer after the United States. About 45% of Brazil’s motor vehicles run on ethanol or ethanol–gasoline mixtures produced from bagasse, a residue of the sugarcane that is grown on only 1% of the country’s arable land. Within a decade, Brazil could expand its sugarcane production, eliminate all oil imports, and greatly increase ethanol exports. To do this, Brazil plans to clear and replace larger areas of its rapidly disappearing Cerrado, a wooded savanna region and one of the world’s biodiversity hot spots, with sugarcane plantations. This would increase the harmful environmental costs of using this resource. In the United States, most ethanol is made from heavily subsidized corn crops. But studies indicate that using fossil-fuel-dependent industrialized agriculture to grow corn and then using more fossil fuel to convert the corn to ethanol provides a net energy yield of only about 1.1–1.5 units of energy per unit of fossil fuel input—a very low net energy yield.
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Also, according to a 2007 study by environmental economist Stephen Polansky, processing all of the corn grown in the United States into ethanol each year with high government subsidies, would meet only about 30 days worth of the country’s current demand for gasoline, at a high cost to taxpayers. A 2008 study by Tim Searchinger at Princeton University and other researchers estimated that clearing and planting grasslands and forests to grow corn for producing ethanol would increase CO2 emissions by 93% compared to burning conventional gasoline over a 30-year period. But a 2007 EPA study estimated that using corn ethanol would reduce greenhouse gas emissions by about 22% compared to burning gasoline. More research is needed to resolve this issue. Driven by U.S. ethanol production, the prices of corn-based foods—including bread, tortilla flour, poultry, beef, pork, and dairy products—are tied to the price of oil and have risen sharply. This in turn has increased the number of hungry and malnourished people who can no longer afford to buy enough food. In 2008, Lester R. Brown estimated that making enough ethanol to fill a 95-liter (25-gallon) tank of an SUV would require an amount of corn grain that would be enough to feed the average person for a year. Also, a sharp increase in corn production in the U.S. Midwest, spurred by federal subsidies for ethanol production, contributes to the annual dead zone that occurs in the Gulf of Mexico. This zone of depleted oxygen is created by large inputs of nutrients carried to the Gulf by the Mississippi River from farmlands in the river’s watershed where the corn is grown. An alternative to corn ethanol is cellulosic ethanol. It is made through a process in which cellulose from plant materials such as leaves, stalks, husks, and wood chips is isolated, and then enzymes are used to convert the cellulose to sugars that can be processed to produce ethanol. By using widely available and inedible cellulose material to produce ethanol, producers could dodge the food vs. biofuels dilemma. A plant that could be used for cellulosic ethanol production is switchgrass, a tall perennial grass GOOD native to North American prairies that grows NEWS faster than corn without the use of fertilizer, is disease resistant and drought tolerant, and can be grown on land unfit for crops. According to a 2008 article by U.S. Department of Agriculture scientist Ken Vogel and his colleagues, using switchgrass to produce ethanol yields about 5.4 times more energy than it takes to grow it—a yield much greater than the 1.1–1.5 net energy yield for corn. However, researchers have also found that large areas of land would be needed to produce enough cellulosic ethanol to make a significant dent in gasoline consumption, and that clearing and planting large areas of land with switchgrass would likely increase greenhouse gas emissions. Thus, scientists differ on how much of a net reduction in greenhouse gas emissions would result from extensive cellulosic ethanol production.
Energy Efficiency and Renewable Energy
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Trade-Offs
Figure 10-15 Using ethanol as a vehicle fuel has advantages and disadvantages compared to using gasoline (Concept 10-5B). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Ethanol Fuel Adva nta ge s
Disad vant ag es
Some reduction in CO2 emissions (sugarcane bagasse)
Low net energy yield (corn) and higher cost
High net energy yield (bagasse and switchgrass)
Higher CO2 emissions (corn)
Corn ethanol competes with food crops and may raise food prices
Potentially renewable
Figure 10-15 lists the advantages and disadvantages of using ethanol as a vehicle fuel compared to gasoline (Concept 10-5B). HOW WOULD YOU VOTE?
✓ ■
Do the advantages of using liquid ethanol as a fuel outweigh its disadvantages? Cast your vote online at www.cengage .com/login.
10-6 What Are the Advantages and
Disadvantages of Using Geothermal Energy? ▲
Geothermal energy has great potential for supplying many areas with heat and electricity, and it has a generally low environmental impact, but the sites where we can use it economically are limited.
CONC EPT 10-6
We Can Get Energy by Tapping the Earth’s Internal Heat Geothermal energy is heat stored in soil, underground rocks, and fluids in the earth’s mantle. We can tap into this stored energy to heat and cool buildings and to produce electricity. Scientists estimate that using just GOOD 1% of the heat stored in the uppermost 5 kilo- NEWS meters (8 miles) of the earth’s crust would provide 250 times more energy than that stored in all the earth’s crude oil and natural gas reserves. We can tap geothermal energy with the use of a geothermal heat pump system. It can heat and cool a house by exploiting the temperature difference between the earth’s surface and its underground. In winter, the system extracts heat from the ground, and in summer, it works in reverse, pumping heat from a home’s interior into the ground. According to the EPA, a well-designed geothermal heat pump system is the most energy-efficient, reliable, environmentally clean, and cost-effective way to heat or cool a space, second only to superinsulation. It produces no air pollutants and emits no CO2.
We can also tap into deeper, more concentrated hydrothermal reservoirs of geothermal energy. This is done by drilling wells into the reservoirs to extract their dry steam, wet steam, or hot water, which are used to heat homes and buildings, to grow vegetables in greenhouses, and to spin turbines to produce electricity. The United States is the world’s largest producer of geothermal electricity from hydrothermal reservoirs. It meets the electricity needs of about 6 million Americans and supplies almost 6% of California’s electricity. Iceland gets almost all of its electricity from hydroelectric and geothermal energy power plants. In the Philippines, geothermal plants provide electricity for 19 million people. China has a large potential for geothermal power, which could help to reduce its dependence on coal-fired power plants. Another source of geothermal energy is hot, dry rock found 5 or more kilometers (3 or more miles) underground almost everywhere. Water can be injected through wells drilled into this rock, heated by the rock, pumped to the surface for use in generating electricity, and then injected back into the earth. The high costs of this technology could come down with more research. CONCEPT 10-6
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
219
Figure 10-16 Using geothermal energy for space heating and for producing electricity or high-temperature heat for industrial processes has advantages and disadvantages (Concept 10-6). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Figure 10-16 lists the advantages and disadvantages of using geothermal energy (Concept 10-6). HOW WOULD YOU VOTE?
✓ ■
Should the country where you live greatly increase its dependence on geothermal energy to provide heat and to produce electricity? Cast your vote online at www.cengage .com/login.
Trade-Offs Geothermal Energy A d vant ag es
D i s a d v a nt a g e s
Moderate net energy and high efficiency at accessible sites
High cost and low efficiency except at concentrated and accessible sites
Lower CO2 emissions than fossil fuels
Scarcity of suitable sites
Low cost at favorable sites
Noise and some CO2 emissions
10-7 What Are the Advantages and Disadvantages
of Using Hydrogen as an Energy Source? ▲
C O NC EPT 10-7 Hydrogen fuel holds great promise for powering cars and generating electricity, but in order for it to be environmentally beneficial, we would have to produce it without the use of fossil fuels.
Will Hydrogen Save Us? Some scientists say that the fuel of the future is hydrogen gas (H2). In the quest to make it so, most research has been focused on using fuel cells, which combine H2 and oxygen gas (O2) to produce electricity and water vapor. Widespread use of hydrogen as a fuel would eliminate most of the outdoor air pollution problems that we face today. It would also greatly reduce the threat of projected climate change, because using it emits no CO2—as long as the H2 is not produced with the use of fossil fuels or nuclear power. So what is the catch? There are three challenges in turning the vision of hydrogen as a fuel into reality. First, hydrogen is chemically locked up in water and in organic compounds such as methane and gasoline, so it takes energy to produce H2 fuel from these compounds. Second, fuel cells are the best way to use H2 to produce electricity, but current versions of fuel cells are expensive. Third, whether or not a hydrogen-based energy system produces less outdoor air pollution and CO2 than a fossil fuel system depends on how the H2 is produced. We could use electricity from coal-burning and conventional nuclear power plants to decompose water into hydrogen gas and oxygen gas. But this approach does not avoid the harmful environmental effects associated with using coal and the nuclear fuel cycle. We can also make H2 from coal and strip it from organic com-
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pounds found in fuels such as gasoline or natural gas. However, according to a 2002 study, using these methods to produce H2 would add much more CO2 to the atmosphere per unit of heat generated than does burning these carbon-containing fuels directly. Most proponents of hydrogen believe that if we are to receive its very low pollution and low CO2 emission benefits, the energy used to produce H2 must come from lowpolluting, renewable sources that emit little or no CO2, such as wind farms, solar cells, geothermal energy, and microhydropower plants. Once produced, H2 can be stored in a pressurized tank as liquid hydrogen or in solid metal hydride compounds, which releases H2 when heated. Scientists are also evaluating ways to store H2 by coating the surfaces of activated charcoal or tiny carbon fibers with it; when heated the coated surfaces also release the H2. Another possibility is to store H2 inside very tiny glass microspheres that can easily be filled and refilled. Yet another possibility is the development of ultracapacitors, devices that can quickly store large amounts of electrical energy, which would then be used to propel cars or to produce H2 on demand. More research is needed to transform these possibilities into realities. Metal hydrides, sodium borohydride, and the other H2 storage devices listed above will not explode or burn if a vehicle’s fuel tank is ruptured in an accident. Thus, H2 stored in such ways is a much safer fuel than gasoline, diesel fuel, natural gas, or concentrated ethanol.
Energy Efficiency and Renewable Energy
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Trade-Offs
Figure 10-17 Using hydrogen as a fuel for vehicles and for providing heat and electricity has advantages and disadvantages (Concept 10-7). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Hydrogen A d v a nta g e s Can be produced from plentiful water at some sites
D i sad v antag e s Fuel cell
No direct CO2 emissions if produced from water Good substitute for oil
Negative net energy yield
CO2 emissions if produced from carbon-containing compounds High costs require subsidies
Also, the use of ultralight car bodies with an energyefficient aerodynamic design and made of composites would improve fuel efficiency so that large hydrogen fuel tanks would not be needed. Figure 10-17 lists the advantages and disadvantages of using hydrogen as an energy resource (Concept 10-7). HOW WOULD YOU VOTE?
High efficiency (45–65%) in fuel cells
Needs H2 storage and distribution system
✓ ■
Do the advantages of producing and burning hydrogen as an energy resource outweigh the disadvantages? Cast your vote online at www.cengage.com/login.
10-8 How Can We Make the Transition
to a More Sustainable Energy Future? ▲
We can make the transition to a more sustainable energy future by greatly improving energy efficiency, using a mix of renewable energy resources, and including the environmental costs of all energy resources in their market prices.
CONC EPT 10-8
Choosing Energy Paths In developing energy policies—the laws, regulations, and programs that affect energy production and use—governments must keep the future in mind, because experience shows that it usually takes at least 50 years and huge investments to phase in new energy alternatives. Creating energy policy involves trying to answer the following questions for each energy alternative: •
How much of the energy resource is likely to be available in the near future (the next 25 years) and in the long term (the next 50 years)?
•
What is the estimated net energy yield (see Chapter 9, Science Focus, p. 190) for the resource?
•
How much will it cost to develop, phase in, and use the resource?
•
What government research and development subsidies and tax breaks will be needed in order to develop the resource?
•
How will dependence on the resource affect national and global economic and military security?
•
How vulnerable is the resource to terrorism?
•
How will extracting, transporting, and using the resource affect the environment, the earth’s climate, and human health? Can we include these harmful costs in the market price of the resource through mechanisms like taxing and reducing environmentally harmful subsidies?
•
Does use of the resource produce hazardous, toxic, or radioactive substances that we must safely store for very long periods of time?
Our energy future depends primarily on which energy resources the government and private companies decide to promote, and on political and economic pressure from citizens and consumers. Energy expert Amory Lovins describes this process as “choosing an energy path.” In considering possible energy paths, scientists and energy experts who have evaluated energy alternatives have come to three general conclusions. First, there will likely be a gradual shift from large, centralized macropower systems to smaller, decentralized micropower systems (Figure 10-18, p. 222) such as wind turbines, household solar-cell panels, rooftop solar water heaters, small natural gas turbines, and eventually fuel cells for cars, houses, and commercial buildings. CONCEPT 10-8
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221
Bioenergy power plants
Wind farm
Small solar-cell power plants
Fuel cells
Rooftop solarcell arrays
Solar-cell rooftop systems
Smart electrical and distribution system
Commercial
Small wind turbine Residential
Industrial
Microturbines
Figure 10-18 Solutions: During the next few decades, we will probably shift from dependence on a centralized macropower system, based on a few hundred large coal-burning and nuclear power plants, to a decentralized micropower system, in which electricity is produced by a large number of dispersed, small-scale, local power generating systems. The smaller systems would be largely based on locally available renewable energy resources and could feed the power they produce into a new smart grid. Question: Can you think of any disadvantages of a decentralized power system?
This shift from centralized macropower to dispersed micropower would be similar to the computer industry’s shift from large, centralized mainframes to increasingly smaller, widely dispersed PCs, laptops, and handheld computers. Such a shift would improve national and economic security because countries would GOOD rely on diverse, dispersed, domestic, and renew- NEWS able energy resources instead of on a smaller number of large power plants that burn nonrenewable fossil fuels, depend on an aging electrical grid, and are vulnerable to sabotage. The second general conclusion of experts is that a combination of greatly improved energy efficiency and the temporary use of natural gas will be the best way to make the transition to a diverse mix of locally available renewable energy resources over the next several decades (Concept 10-8). By using a variety of locally available renewable energy resources, we would be applying the diversity principle of sustainability by not putting all of our “energy eggs” in a single basket. The third general conclusion is that because of their still-abundant supplies and artificially low prices, fossil
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fuels will continue to be used in large quantities. This presents two major challenges. One is to find ways to reduce the harmful environmental impacts of widespread fossil fuel use. The other is to find ways to include more of the harmful environmental costs of using fossil fuels in their market prices, as less environmentally harmful alternatives are phased in. Figure 10-19 summarizes these and other strategies for making the transition to a more sustain- GOOD able energy future over the next 50 years (Con- NEWS cept 10-8).
Economics, Politics, and Education Can Help Us Shift to More Sustainable Energy Resources Most analysts suggest that economics, politics, and consumer education hold the keys to making a shift to more sustainable energy resources. Governments can use three strategies to stimulate or reduce the shortterm and long-term use of a particular energy resource.
Energy Efficiency and Renewable Energy
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Solutions Making the Transition to a More Sustainable Energy Future Improve Energy Efficiency
More Renewable Energy
Increase fuel-efficiency standards for vehicles, buildings, and appliances
Greatly increase use of renewable energy Provide large subsidies and tax credits for use of renewable energy
Provide large tax credits for buying efficient cars, houses, and appliances
Reward utilities for reducing demand for electricity
Greatly increase renewable energy research and development
Reduce Pollution and Health Risk Phase out coal subsidies and tax breaks Levy taxes on coal and oil use
Greatly increase energy efficiency research and development
Phase out nuclear power subsidies, tax breaks, and loan guarantees
Figure 10-19 Energy analysts have made a number of suggestions for helping us make the transition to a more sustainable energy future (Concept 10-8). Questions: Which five of these solutions do you think are the best ones? Why?
First, they can keep the prices of selected energy resources artificially low to encourage use of those resources. They do this by providing research and development subsidies, tax breaks, and loan guarantees to encourage the development of those resources, and by enacting regulations that favor them. For decades, this approach has been employed to stimulate the development and use of fossil fuels and nuclear power in the United States as well as in most other more-developed countries. This has created an uneven economic playing field that encourages energy waste and rapid depletion of nonrenewable energy resources, while it discourages improvements in energy efficiency and the development of renewable energy resources. The second major strategy that governments can use is to keep the prices of selected energy resources artificially high to discourage their use. They can do this by eliminating existing tax breaks and other subsidies that favor use of the targeted resource, and by enacting restrictive regulations or taxes on its use. Such measures can increase government revenues, encourage improvements in energy efficiency, reduce dependence on imported energy, and decrease the use of energy resources that have limited supplies. To make such changes acceptable to the public, analysts suggest that governments can offset energy taxes by reducing income and payroll taxes and providing an energy safety net for low-income users. HOW WOULD YOU VOTE?
✓ ■
Should the government of the country where you live greatly increase taxes on fossil fuels and offset this by reducing income and payroll taxes, and providing an energy safety net for the poor and lower middle class? Cast your vote online at www.cengage.com/login.
Third, governments can emphasize consumer education. Even if governments offer generous financial incentives for energy efficiency and renewable energy use, people will not make such investments if they are uninformed—or misinformed—about the availability, advantages, disadvantages, and hidden environmental costs of various energy resources. For example, cloudy Germany has more solar water heaters and solar-cell panels than sunny France and Spain, mostly because the German government has made the public aware of the benefits of these technologies. We have the creativity, wealth, and most of GOOD the technology needed to make the transition to NEWS a more sustainable energy future. Making this transition depends primarily on education, economics, and politics—on how well individuals understand environmental and energy problems and their possible solutions, and on the elected officials they vote in and how they then influence those officials. People can also vote with their wallets by refusing to buy energy-inefficient and environmentally harmful products and services, and by letting company executives know about their choices. Figure 10-20 (p. 224) lists some ways in which you can contribute to making the transition to a more sustainable energy future. We can make the transition to a more sustainable energy future by applying the three principles of sustainability. This means: •
Relying much more on direct and indirect forms of solar energy, such as wind power and biomass, and on geothermal energy.
•
Recycling and reusing materials and thus reducing wasteful and excessive consumption of energy and matter. CONCEPT 10-8
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What Can You Do? Shifting to More Sustainable Energy Use ■
Get an energy audit done for your house or office
■
Use passive solar heating
■
Drive a vehicle that gets at least 15 kilometers per liter (35 miles per gallon)
■
For cooling, open windows and use ceiling fans or whole-house attic or window fans
■
Use a carpool to get to work or to school
■
Turn thermostats down in winter and up in summer
■
Walk, bike, and use mass transit
■
■
Superinsulate your house and plug all air leaks
Buy the most energy-efficient home heating and cooling systems, lights, and appliances available
■
Turn off lights, TV sets, computers, and other electronic equipment when they are not in use
■
Turn down the thermostat on water heaters to 43–49°C (110–120°F) and insulate hot water heaters and pipes
■
Wash laundry in warm or cold water
Figure 10-20 Individuals matter: You can reduce your use and waste of energy. Questions: Which three of these steps do you think are the most important? Why? Which things in this list do you already do or plan to do?
•
Mimicking nature’s reliance on biodiversity by using a diverse mix of locally and regionally available renewable energy resources.
■ Using a mix of renewable energy sources would drastically reduce pollution, greenhouse gas emissions, and biodiversity losses.
Here are this chapter’s three big ideas:
■ Making the transition to a more sustainable energy future will require sharply reducing energy waste, using a mix of renewable energy resources, and including the harmful environmental costs of energy resources in their market prices.
■ The best way to evaluate energy resources is on the basis of their potential supplies, their estimated net energy yields, and the environmental impacts of using them.
A transition to renewable energy is inevitable, not because fossil fuel supplies will run out—large reserves of oil, coal, and gas remain in the world—but because the costs and risks of using these supplies will continue to increase relative to renewable energy. MOHAMED EL-ASHRY
REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 205. Distinguish between energy conservation and energy efficiency. Explain why we can think of energy efficiency as an energy resource. How much of the energy used in the United States is wasted unnecessarily? What are the major advantages of reducing energy waste? What are four commonly used devices that waste large amounts of energy? Describe a smart energy grid and summarize its benefits. 2. What is cogeneration (combined heat and power, or CHP)? List three ways to save energy in industry. Describe the trends in fuel efficiency in the United States since the 1970s. Explain why the real cost of gasoline is much higher than what consumers pay at the pump. Distinguish among hybrid, plug-in hybrid, and fuel-cell motor
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vehicles. Describe three elements of energy-efficient building design. Describe five ways to save energy in an existing building. 3. List five advantages of relying more on a variety of renewable energy sources and describe two factors holding back such a transition. 4. Distinguish between passive solar heating and active solar heating systems, and discuss the major advantages and disadvantages of such systems. Discuss the major advantages and disadvantages of using solar energy to generate high-temperature heat and electricity. What are solar cells (photovoltaic [PV] cells) and what are the major advantages and disadvantages of using them to produce electricity?
Energy Efficiency and Renewable Energy
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5. What are the major advantages and disadvantages of using flowing water to produce electricity in hydropower plants? What is the potential for using tides and waves to produce electricity? 6. How can we capture wind energy for electrical generation? What are the major advantages and disadvantages of using wind to produce electricity?
major advantages and disadvantages of using geothermal energy as a source of heat and as a way to produce electricity? 9. What are three challenges that face us in using hydrogen as a fuel on a widespread basis? Why is it important to use renewable energy sources in the process of creating hydrogen fuel? What are the major advantages and disadvantages of using hydrogen as fuel?
7. Define and distinguish between biomass and biofuels. What are the major advantages and disadvantages of using solid biomass as fuel? Describe three major advantages that biofuels have over gasoline and diesel fuel. Discuss the major advantages and disadvantages of using ethanol as a vehicle fuel. Why is the use of corn to make ethanol controversial?
10. What are six questions that we should consider for any energy source in creating energy policy? List three general conclusions from energy experts about possible future energy paths for the world. Describe three strategies that governments can use to encourage the use of certain energy resources.
8. What is geothermal energy? What can a geothermal heat pump system do for home owners? What are the
Note: Key terms are in bold type.
CRITICAL THINKING 1. List five ways in which you unnecessarily waste energy during a typical day, and explain how these actions violate any of the three principles of sustainability (see back cover). 2. Congratulations! You have won $500,000 to build a more sustainable house of your choice. With the goal of maximizing energy efficiency, what type of house would you build? How large would it be? Where would you locate it? What types of materials would you use? What types of materials would you not use? How would you heat and cool the house? How would you heat water? What type of lighting, stove, refrigerator, washer, and dryer would you use? Which of these appliances could you do without? 3. Should buyers of energy-efficient motor vehicles receive large government subsidies, funded by taxes on gasguzzlers? Explain. 4. Explain why you agree or disagree with the following proposals made by various energy analysts: a. Government subsidies for all energy alternatives should be eliminated so that all energy choices can compete in a true free-market system. b. All government tax breaks and other subsidies for conventional fuels (oil, natural gas, and coal), synthetic
natural gas and oil, and nuclear power (fission and fusion) should be phased out. They should be replaced with subsidies and tax breaks for improving energy efficiency and developing solar, wind, geothermal, hydrogen, and biomass energy alternatives. c. Development of solar, wind, and hydrogen energy should be left to private enterprise and should receive little or no help from the federal government, but nuclear energy and fossil fuels should continue to receive large federal government subsidies. 5. Imagine that you are in charge of the U.S. Department of Energy (or the energy agency in the country where you live). What percentage of your research and development budget will you devote to each of the following: fossil fuels, nuclear power, renewable energy, and improvements in energy efficiency? How would you distribute your funds among the various renewable energy options? Explain your thinking. 6. Congratulations! You are in charge of the world. List the five most important features of your energy policy. 7. List two questions that you would like to have answered as a result of reading this chapter.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 10 for many study aids and ideas for further
reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles. WWW.CENGAGEBRAIN.COM
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11
Environmental Hazards and Human Health
Key Questions and Concepts 11-1
What major health hazards do we face?
11-4
How can we evaluate chemical hazards?
C O N C E P T 1 1 - 1 We face health hazards from biological, chemical, physical, and cultural factors, and from the lifestyle choices we make.
CONCEPT 11-4A
11-2 What types of biological hazards do we face?
C O N C E P T 1 1 - 4 B Many health scientists call for much greater emphasis on pollution prevention to reduce our exposure to potentially harmful chemicals.
C O N C E P T 1 1 - 2 The most serious biological hazards we face are infectious diseases, especially flu, AIDS, tuberculosis, diarrheal diseases, and malaria.
Scientists use live laboratory animals, case reports of poisonings, and epidemiological studies to estimate the toxicity of chemicals, but these methods have limitations.
How do we perceive risks and how can we avoid the worst of them? 11-5
What types of chemical hazards do we face? 11-3
C O N C E P T 1 1 - 5 We can reduce the major risks we face by becoming informed, thinking critically about risks, and making careful choices.
C O N C E P T 1 1 - 3 There is growing concern about chemicals in the environment that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine systems.
The dose makes the poison. PARACELSUS, 1540
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Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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11-1 What Major Health Hazards Do We Face? ▲
We face health hazards from biological, chemical, physical, and cultural factors, and from the lifestyle choices we make.
CONC EPT 11-1
Risks Are Usually Expressed as Probabilities A risk is the probability of suffering harm from a hazard that can cause injury, disease, death, economic loss, or damage. It is usually expressed as a mathematical statement about how probable it is that harm will be suffered from a hazard. Scientists often state probability in terms such as “The lifetime probability of developing lung cancer from smoking one pack of cigarettes per day is 1 in 250.” This means that 1 of every 250 people who smoke a pack of cigarettes every day will likely develop lung cancer over a typical lifetime (usually considered to be 70 years). Probability can also be expressed as a percentage, as in a 30% chance of rain. It is important to distinguish between possibility and probability. When we say that it is possible that a smoker can get lung cancer, we are saying that this event could happen. Probability gives us an estimate of the likelihood of such an event. Risk assessment is the process of using statistical methods to estimate how much harm a particular hazard can cause to human health or to the environment. Risk management involves deciding whether or how to reduce a particular risk to a certain level and at what cost. Figure 11-1 summarizes how risks are assessed and managed.
Risk Assessment Hazard identification What is the hazard?
Probability of risk How likely is the event?
Consequences of risk What is the likely damage?
Risk Management Comparative risk analysis How does it compare with other risks? Risk reduction How much should it be reduced? Risk reduction strategy How will the risk be reduced? Financial commitment How much money should be spent?
Figure 11-1 Science: Risk assessment and risk management are used to estimate the seriousness of various risks and how to reduce such risks. Question: What is an example of how you have applied this process in your daily living?
organisms. Examples are bacteria, viruses, parasites, protozoa, and fungi. •
Chemical hazards from harmful chemicals in air, water, soil, food, and human-made products.
•
Physical hazards such as fire, earthquakes, volcanic eruptions, floods, and storms.
We Face Many Types of Hazards
•
Cultural hazards such as unsafe working conditions, unsafe highways, criminal assault, and poverty.
We can suffer harm from five major types of hazards (Concept 11-1):
•
Lifestyle hazards stemming from choices people make such as to smoke, to eat unhealthy foods, to drink too much alcohol, and to have unsafe sex.
•
Biological hazards from more than 1,400 pathogens—organisms that can cause disease in other
11-2 What Types of Biological Hazards Do We Face? ▲
The most serious biological hazards we face are infectious diseases, especially flu, AIDS, tuberculosis, diarrheal diseases, and malaria.
CONC EPT 11-2
Some Diseases Can Spread from One Person to Another An infectious disease is caused when a pathogen such as a bacterium, virus, or parasite invades the body and multiplies in its cells and tissues. Important examples are
flu viruses and bacteria that cause tuberculosis. A transmissible disease (also called a contagious or communicable disease) is an infectious disease that can be transmitted from one person to another. Examples are flu, acquired immune deficiency syndrome (AIDS), tuberculosis, and measles. CONCEPT 11-2
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Figure 11-2 Science: There are a number of pathways on which infectious disease organisms can enter the human body. Question: Can you think of other pathways not shown here?
Pets
Livestock
Wild animals
Insects
Food
Water
Air
Fetus and babies
Other humans
Humans
A nontransmissible disease is caused by something other than a living organism and does not spread from one person to another. Such diseases tend to develop slowly and have multiple causes. They include cardiovascular (heart and blood vessel) diseases, most cancers, asthma, and diabetes. Figure 11-2 shows major pathways on which infectious disease organisms can enter the human body. Such diseases can then be spread through air, water, food, and body fluids such as feces, urine, blood, and droplets sprayed by people sneezing and coughing. Two factors have increased the spread of infectious diseases over time: the sheer number of humans and the speed of human travel from one place to another. A large-scale outbreak of an infectious disease in a region or a country is called an epidemic. A global epidemic such as tuberculosis or AIDS is called a pandemic. Figure 11-3 shows the annual death toll from the world’s seven deadliest infectious diseases (Concept 11-2). One reason why infectious disease is still a serious threat is that many disease-carrying bacteria have developed genetic immunity to widely used antibiotics (Science Focus, at right). Also, many disease-transmit-
ting insects such as certain species of mosquitoes have become immune to widely used pesticides that once helped to control their populations. ■ C AS E S T UDY
The Growing Global Threat from Tuberculosis Since 1990, one of the world’s most underreported stories has been the rapid spread of tuberculosis (TB), an extremely contagious bacterial infection of the lungs.
Disease (type of agent) Pneumonia and flu (bacteria and viruses)
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3.2 million
HIV/AIDS (virus)
2.0 million
Tuberculosis (bacteria) Diarrheal diseases (bacteria and viruses)
Figure 11-3 Global outlook: The World Health Organization estimates that each year, the world’s seven deadliest infectious diseases kill 11.1 million people—most of them poor people in less-developed countries. This averages about 30,400 mostly preventable deaths every day, or about one every 3 seconds. Question: What conditions in lessdeveloped countries do you think contribute to the high number of deaths caused by infectious diseases in such countries? (Data from the World Health Organization, 2007)
Deaths per year
1.8 million
1.6 million
Hepatitis B (virus)
1 million
Malaria (protozoa)
900,000
Measles (virus)
800,000
Environmental Hazards and Human Health
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S C I E NC E FO C U S Genetic Resistance to Antibiotics Is Increasing
W
e risk falling behind in our efforts to prevent infectious bacterial diseases because of the astounding reproductive rate of bacteria, some of which can produce well over 16 million offspring in 24 hours. This allows bacteria to quickly become genetically resistant to an increasing number of antibiotics—or chemicals designed to kill bacteria—through natural selection (see Figure 3-2, p. 53). Other factors also play key roles in fostering such genetic resistance. One is the spread of bacteria around the globe by human travel and international trade. Another is the overuse of pesticides, which increases populations of pesticide-resistant insects and other carriers of bacterial diseases. In addition, some drug-resistant bacteria can quickly transfer
their resistance to nonresistant bacteria by exchanging genetic material. Yet another factor is overuse of antibiotics for colds, flu, and sore throats, most of which are viral diseases that cannot be treated with antibiotics. In many countries, antibiotics are available without a prescription, which promotes unnecessary use. Bacterial resistance to some antibiotics has increased because of their widespread use in livestock and dairy animals to control disease and to promote growth. In addition, the growing use of antibacterial hand soaps and other cleansers is probably promoting genetic resistance in bacteria as well. As a result of these factors acting together, every major disease-causing bacterium now has strains that resist at least one of the
According to the World Health Organization (WHO), this highly infectious bacterial disease strikes 9.2 million people per year and kills 1.7 million—about 84% of them in developing countries. On average, someone dies of TB every 20 seconds. Many TB-infected people do not appear to be sick, and about half of them do not know they are infected. Left untreated, each person with active TB typically infects a number of other people. Without treatment, about half of the people with active TB die from bacterial destruction of their lung tissue. Several factors account for the recent spread of TB. One is that there are too few TB screening and control programs, especially in less-developed countries, where 95% of the new cases occur. A second problem is that most strains of the TB bacterium have developed genetic resistance to the majority of the effective antibiotics. Also, population growth, urbanization, and air travel have greatly increased person-to-person contacts, and TB is spreading faster in areas where large numbers of poor people crowd together. In addition, AIDS patients are highly vulnerable to TB, because AIDS greatly weakens its victims’ immune systems. Slowing the spread of TB requires early identification and treatment of people with active TB, especially those with a chronic cough. Treatment with a combination of four inexpensive drugs can cure 90% of individuals with active TB. To be effective, the drugs must be taken every day for 6–9 months. Because the symptoms disappear after a few weeks, many patients, thinking they are cured, stop taking the drugs, allowing the disease to recur in drug-resistant forms and to spread to other people. In recent years, a deadly and apparently incurable form of tuberculosis, known as multidrug-resistant
roughly 160 antibiotics used to treat bacterial infections such as tuberculosis (see the Case Study below). Each year, at least 90,000 people die from infections they picked up while staying in U.S. hospitals, and genetic resistance to antibiotics plays a role in these deaths, according to the U.S. Centers for Disease Control and Prevention (CDC). This serious problem is much worse in hospitals in many other countries. A particularly deadly bacterium, methicillin-resistant staphylococcus aureus, commonly known as MRSA, has become resistant to most common antibiotics. Critical Thinking What are three things that we could do to slow the rate at which disease-causing organisms develop resistance to antibiotics?
TB has been on the rise, especially in parts of Africa, China, India, and Russia. According to the WHO, this drug-resistant form of TB is now found in 49 countries, and each year, there are about 490,000 new cases and 120,000 deaths. Because this disease cannot be treated effectively with antibiotics, victims must be permanently isolated from the rest of society. Victims also pose a threat to health workers and to potentially every person on the planet who takes a train or a plane and is exposed to undiagnosed people with this incurable form of TB.
Viral Diseases and Parasites Kill Large Numbers of People Viruses evolve quickly, are not affected by antibiotics, and can kill large numbers of people. The biggest viral killer is the influenza or flu virus (Concept 11-2), which is transmitted by the body fluids or airborne emissions of an infected person. Easily transmitted and especially potent flu viruses could spread around the world in a pandemic that could kill millions of people in only a few months. The second biggest viral killer is the human immunodeficiency virus (HIV) (see the Case Study that follows) which causes AIDS. It is transmitted by unsafe sex, sharing of needles by drug users, infected mothers who pass the virus to their offspring before or during birth, and exposure to infected blood. On a global scale, HIV infects about 2.5 million people each year, and the complications resulting from AIDS kill about 2 million people annually. The third largest viral killer is the hepatitis B virus (HBV), which damages the liver and kills about a million people each year. It is spread in the same ways as HIV is spread. CONCEPT 11-2
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■ CAS E STUDY
The Global HIV/AIDS Epidemic The global spread of acquired immune deficiency syndrome (AIDS), caused by infection with the human immunodeficiency virus (HIV), is a major global health threat. The virus itself is not deadly, but it cripples the immune system and leaves the body vulnerable to infectious bacteria and other viruses. Since the HIV virus was identified in 1981, this viral infection has spread around the globe. According to the WHO, in 2008 a total of about 33 million people worldwide (more than 1 million in the United States) were living with HIV. About 72% of them were in African countries located south of the Sahara Desert (subSaharan Africa). Also, 2008 saw about 2.7 million new cases of AIDS—an average of about 7,400 new cases per day. Treatment that includes combinations of antiviral drugs can slow the progress of HIV to AIDS, but the drugs are expensive. With such drugs, a person with AIDS can expect to live about 24 years after being infected, on average, at a cost of about $25,200 a year. These medications cost too much for extensive use in less-developed countries with widespread AIDS infections.
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Age
In recent years, several other viruses that cause previously unknown diseases have received widespread media coverage. They are examples of emergent diseases that were previously unknown or were absent in human populations for at least 20 years. One is the West Nile virus, which is transmitted to humans by the bite of a common mosquito that has been infected by feeding on birds that carry the virus. Fortunately, the chance of being infected and killed by West Nile virus is low (about 1 in 2,500). A second highly publicized virus is the severe acute respiratory syndrome (SARS) virus, which first appeared in humans in China in 2002. SARS, which has flulike symptoms, can easily spread from person to person and quickly turn into life-threatening pneumonia. Swift local action by the WHO and other health agencies helped to contain the spread of this disease by July 2003. But without careful vigilance, it might break out again. Health officials are concerned about the spread of West Nile virus, SARS, the newest avian flu, and other emergent diseases. But in terms of annual infection rates and deaths, the three most dangerous viruses by far are still flu, HIV, and HBV (Concept 11-2). You can greatly reduce your chances of getting infectious diseases by practicing good old-fashioned hygiene. Wash your hands thoroughly and frequently, avoid touching your face, and stay away from people who have flu or other viral diseases. Yet another growing health hazard is infectious diseases caused by parasites, especially malaria (see the second Case Study that follows).
100+ 95–99 90–94 85–89 80–84 75–79 70–74 65–69 60–64 55–59 50–54 45–49 40–44 35–39 30–34 25–29 20–24 15–19 10–14 5–9 0–4
Males
Females
120 100 80 60 40 20 0 20 40 60 80 100 120 Population (thousands) With AIDS
Without AIDS
Figure 11-4 Global outlook: Worldwide, AIDS is the leading cause of death for people ages 15–49. This loss of productive working adults can affect the age structure of a population. In Botswana, more than 24% of this age group was infected with HIV in 2008 and about 148,000 people died. This figure shows two projected age structures for Botswana’s population in 2020—one including the possible effects of the AIDS epidemic (darker bars), and the other not including those effects (lighter bars). Question: How might this affect Botswana’s economic development?
Between 1981 and 2008, more than 25 million people (584,000 in the United States) died of AIDS-related diseases. Every year, AIDS claims about 2 million more lives (about 15,000 in the United States)—an average of nearly 5,500 deaths every day. AIDS has reduced the life expectancy of the 750 million people living in sub-Saharan Africa from 62 to 47 years, on average, and to 40 years in the seven countries most severely affected by AIDS. The premature deaths of teachers, health-care workers, soldiers, and other young, productive adults affect the population age structure in African countries such as Botswana (Figure 11-4). These deaths also lead to diminished education and health care, decreased food production and economic development, and disintegrating families. ■ C AS E S T UDY
Malaria—The Spread of a Deadly Parasite About one of every five people in the world—most of them living in poor African countries—is at risk from malaria (Figure 11-5). So is anyone traveling to malariaprone areas, because there is no vaccine for preventing this disease.
Environmental Hazards and Human Health
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Figure 11-5 Global outlook: About 40% of the world’s population lives in areas in which malaria is prevalent. Malaria kills at least 1 million people a year or about 2 people every minute. More than 80% of these victims live in sub-Saharan Africa and most of them are children younger than age 5. (Data from the World Health Organization and U.S. Centers for Disease Control and Prevention)
Malaria is caused by a parasite that is spread by the bites of certain mosquito species. It infects and destroys red blood cells, causing intense fever, chills, drenching sweats, severe abdominal pain, vomiting, headaches, and increased susceptibility to other diseases. It kills an average of at least 2,700 people per day (Concept 11-2). About 90% of those dying are children younger than age 5. Many of the children who survive suffer brain damage or impaired learning ability. Four species of protozoan parasites in the genus Plasmodium cause malaria. Most infections occur when an uninfected female of any of about 60 Anopheles mosquito species bites a person (usually at night) who is infected with the Plasmodium parasite, ingests blood that contains the parasite, and later bites an uninfected person (Figure 11-6). Plasmodium parasites then move out of the mosquito and into the human’s bloodstream and liver where they multiply. Malaria can also be transmitted by contaminated blood transfusions and by drug users sharing needles. Over the course of human history, malarial protozoa probably have killed more people than all the wars ever fought. During the 1950s and 1960s, the spread of malaria was sharply curtailed when swamplands and marshes where mosquitoes breed were drained or sprayed with insecticides, and drugs were used to kill the parasites in victims’ bloodstreams. Since 1970, however, malaria has come roaring back. Most species of the Anopheles mosquito have become genetically resistant to most insec-
ticides. Worse, the Plasmodium parasites have become genetically resistant to common antimalarial drugs. In addition, the clearing and development of tropical forests has led to the spread of malaria among workers and the settlers who follow them. During this century, climate change as projected by scientists is likely to spread cases of malaria across a wider area of the globe. As the average atmospheric temperature increases,
Female mosquito bites infected human, ingesting blood that contains Plasmodium gametocytes
Merozoites enter bloodstream and develop into gametocytes causing malaria and making infected person a new reservoir of parasites.
Plasmodium develop in mosquito. Sporozoites penetrate liver and develop into merozoites.
Female mosquito bites human host and injects Plasmodium sporozoites.
Figure 11-6 Science: The life cycle of malaria. Plasmodium parasites circulate from mosquito to human and back to mosquito.
CONCEPT 11-2 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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populations of malaria-carrying mosquitoes will likely spread from tropical areas to warmer temperate areas of the earth. Researchers are working to develop new antimalarial drugs, vaccines, and biological controls for Anopheles mosquitoes. But these approaches receive too little funding and have proved more difficult to implement than they were originally thought to be. There is now an important effort to provide poor people in malarial regions with free or inexpensive, long-lasting, insecticide-treated bed nets and window screens. Zinc and vitamin A supplements could also be given to children to boost their resistance to malaria. In addition, we can greatly reduce the incidence of malaria by spraying the insides of homes with low concentrations of the pesticide DDT twice a year at a low cost. While it is being phased out in most countries, the WHO supports the use of DDT for malaria control. Some public health officials believe the world needs to make a more coordinated and aggressive effort to control malaria. This will gain increasing urgency as malaria parasites develop greater genetic resistance to treatments, and as the range of Anopheles mosquitoes expands due to projected climate change. Columbia University economist Jeffrey Sachs estimates that spending $2–3 billion a year on preventing and treating malaria might save more than a million lives a year. Sachs notes, “This is probably the best bargain on the planet.”
one-fourth of all deaths of children younger than age 5 (Concept 11-2). This therapy involves administering a simple solution of boiled water, salt, and sugar or rice at a cost of only a few cents per person. It has been the major factor in reducing the annual number of deaths from diarrhea from 4.6 million in 1980 to 1.6 million in 2008. The WHO has estimated that implementing the solutions in Figure 11-7 could save the lives of as many as 4 million children younger than age 5 each year. A key to reducing sickness and premature death from infectious disease is to provide simple latrines and access to safe drinking water to people who do not have them. The United Nations estimates that this could be done for about $20 billion a year—about what rich countries spend each year on bottled water. The WHO estimates that only 10% of global medical research and development money goes toward preventing infectious diseases in less-developed countries, even though more people worldwide suffer and die from these diseases than from all other diseases combined. But the problem is getting more attention. In recent years, philanthropists, including Bill and Melinda Gates GOOD and Warren E. Buffet, have donated billions of NEWS dollars to improve global health, with primary emphasis on infectious diseases in less-developed countries.
Solutions We Can Reduce the Incidence of Infectious Diseases According to the WHO, the global death rate from infectious diseases decreased by more than two- GOOD thirds between 1970 and 2006 and is projected NEWS to continue dropping. Also, between 1971 and 2006, the percentage of children in less-developed countries who were immunized with vaccines to prevent tetanus, measles, diphtheria, typhoid fever, and polio increased from 10% to 90%—saving about 10 million lives each year. Between 1990 and 2008, the estimated annual number of children younger than age 5 who died from preventable diseases such as diarrhea, pneumonia, and malaria dropped from nearly 12 million to 7.7 million. Figure 11-7 lists measures promoted by health scientists and public health officials to help prevent or reduce the incidence of infectious diseases—especially in less-developed countries. An important breakthrough has been the development of simple oral rehydration therapy to help prevent death from dehydration for victims of severe diarrhea, which causes about
Infectious Diseases Increase research on tropical diseases and vaccines Reduce poverty Decrease malnutrition Improve drinking water quality Reduce unnecessary use of antibiotics Educate people to take all of an antibiotic prescription Reduce antibiotic use to promote livestock growth Require careful hand washing by all medical personnel Immunize children against major viral diseases Provide oral rehydration for diarrhea victims
Figure 11-7 There are a number of ways to prevent or reduce the incidence of infectious diseases, especially in less-developed countries. Questions: Which three of these approaches do you think are the most important? Why?
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Conduct global campaign to reduce HIV/AIDS
Environmental Hazards and Human Health
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11-3 What Types of Chemical Hazards Do We Face? ▲
There is growing concern about chemicals in the environment that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine systems.
CONC EPT 11-3
Some Chemicals Can Cause Cancers, Mutations, and Birth Defects A toxic chemical is one that can cause temporary or permanent harm or even death to humans and animals. In 2004, the U.S. Environmental Protection Agency (EPA) listed arsenic, lead, mercury (Science Focus, below), vinyl chloride (used to make PVC plastics), and polychlorinated biphenyls (PCBs) as the top five toxic substances in terms of human and environmental health. There are three major types of potentially toxic agents. Carcinogens are chemicals, types of radiation, or certain viruses that can cause or promote cancer—a disease in which malignant cells multiply uncontrollably and create tumors that can damage the body and often lead to premature death. Examples of carcinogens are arsenic, benzene, formaldehyde, PCBs, radon, cer-
tain chemicals in tobacco smoke, and ultraviolet (UV) radiation. Typically, 10–40 years may elapse between the initial exposure to a carcinogen and the appearance of detectable cancer symptoms. Partly because of this time lag, many healthy teenagers and young adults have trouble believing that their smoking, drinking, eating, and other habits today could lead to some form of cancer before they reach age 50. The second major type of toxic agent, mutagens, includes chemicals or forms of radiation that cause or increase the frequency of mutations, or changes, in the DNA molecules found in cells. Most mutations cause no harm but some can lead to cancers and other disorders. For example, nitrous acid, formed by the digestion of nitrite preservatives in foods, can cause mutations linked to increases in stomach cancer in people who consume large amounts of processed foods and
S C I E NC E FO C U S Mercury’s Toxic Effects
M
ercury (Hg) and its compounds are all toxic. Research indicates that longterm exposure to high levels of mercury can permanently damage the human nervous system, kidneys, and lungs. Fairly low levels of mercury can also harm fetuses and cause birth defects. This toxic metal is released into the air from rocks, soil, and volcanoes, and by vaporization from the ocean. Such natural sources account for about one-third of the mercury reaching the atmosphere each year. According to the EPA, the remaining twothirds come from human activities—primarily from the smokestacks of coal-burning power plants, cement kilns, and coal-burning industrial facilities. When it rains, these emissions are washed out of the atmosphere onto the soil and into bodies of water. Because mercury is an element, it cannot be broken down or degraded. Thus, this indestructible pollutant accumulates in soil, water, and the bodies of people, fish, and other animals that feed high on food chains. According to the National Resources Defense Council, large predatory fish such as tuna, swordfish, mackerel, and sharks can have
mercury concentrations in their bodies that are as much as 10,000 times higher than the levels in the water around them. In the atmosphere, some elemental mercury is converted to more toxic inorganic and organic mercury compounds that can be deposited in aquatic environments. For example, under certain conditions in aquatic systems, bacteria can convert inorganic mercury compounds to highly toxic methyl mercury, which can be biologically magnified in food chains and webs. As a result, in such aquatic systems high levels of methyl mercury are often found in the tissues of large fishes, which feed at high trophic levels. The greatest risk from exposure to low levels of methyl mercury is brain damage in fetuses and young children. Studies estimate that 30,000–60,000 of the children born each year in the United States are likely to have reduced IQs and possible nervous system damage because of such exposure. Also, methyl mercury has been shown to harm the heart, kidneys, and immune systems of some adults. A 2009 EPA study found that almost half of the fish tested in 500 lakes and reservoirs
across the United States had levels of mercury that exceeded what the EPA says is safe for people eating fish more than two times a week. Similarly, a 2009 study by the U.S. Geological Survey of nearly 300 streams across the United States found traces of mercury in every fish tested, with one-fourth of the fish exceeding levels determined by the EPA to be safe. All but two U.S. states—Wyoming and Alaska—have issued advisories warning people not to eat certain types of fish. In its 2003 report on global mercury pollution, the UN Environment Programme (UNEP) recommended phasing out coal-burning power plants and waste incinerators throughout the world as rapidly as possible. Other recommendations are to reduce or eliminate mercury in the production of batteries, paints, and chlorine by no later than 2020. Substitute materials and processes are available for these products. Critical Thinking Do you agree with the UNEP recommendation to phase out all coal-burning facilities as rapidly as possible? Explain. How might your lifestyle change if this were done?
CONCEPT 11-3 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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wine containing such preservatives. Harmful mutations occurring in reproductive cells can be passed on to offspring and to future generations. The third major type of toxic agents, teratogens, includes chemicals that cause harm or birth defects to a fetus or embryo. Ethyl alcohol is a teratogen. Drinking during pregnancy can lead to offspring with low birth weight and a number of physical, developmental, behavioral, and mental problems. Other teratogens are benzene, formaldehyde, lead, and mercury (Science Focus, p. 233).
Some Chemicals May Affect Our Immune, Nervous, and Endocrine Systems Since the 1970s, research on wildlife and laboratory animals, along with some studies of humans, have yielded a growing body of evidence that suggests longterm exposure to some chemicals in the environment can disrupt the body’s immune, nervous, and endocrine systems (Concept 11-3). The immune system consists of specialized cells and tissues that protect the body against disease and harm-
ful substances by forming antibodies that render invading agents harmless. Some chemicals such as arsenic, methyl mercury, and dioxins can weaken the human immune system and leave the body vulnerable to attacks by allergens and infectious bacteria, viruses, and protozoa. Some natural and synthetic chemicals in the environment, called neurotoxins, can harm the human nervous system (brain, spinal cord, and peripheral nerves). Effects can include behavioral changes, learning disabilities, retardation, attention deficit disorder, paralysis, and death. Examples of neurotoxins are PCBs, methyl mercury (Science Focus, p. 233), arsenic, lead, and certain pesticides. The endocrine system is a complex network of glands that release tiny amounts of hormones into the bloodstreams of humans and other vertebrate animals. Low levels of these chemical messengers regulate the bodily systems that control sexual reproduction, growth, development, learning ability, and behavior. Exposure to low levels of certain chemicals, called hormonally active agents (HAAs), could impair reproductive systems and sexual development and cause physical and behavioral disorders. Examples of HAAs include aluminum, atrazine and several other herbicides, DDT, mercury, and PCBs.
11-4 How Can We Evaluate Chemical Hazards? ▲
C O NC EPT 11-4A
▲
C O NC EPT 11-4B
Scientists use live laboratory animals, case reports of poisonings, and epidemiological studies to estimate the toxicity of chemicals, but these methods have limitations. Many health scientists call for much greater emphasis on pollution prevention to reduce our exposure to potentially harmful chemicals.
Many Factors Determine the Harmful Health Effects of a Chemical Toxicology is the study of the harmful effects of chemicals on humans and other organisms. Toxicity is a measure of the harmfulness of a substance—its ability to cause injury, illness, or death to a living organism. A basic principle of toxicology is that any synthetic or natural chemical can be harmful if ingested in a large enough quantity. But the critical question is this: At what level of exposure to a particular toxic chemical will the chemical cause harm? This is the meaning of the chapter-opening quote by the German scientist Paracelsus: The dose makes the poison. This is a difficult question to answer because of the many variables involved in estimating the effects of human exposure to chemicals. A key factor is the dose, the amount of a harmful chemical that a person has ingested, inhaled, or absorbed through the skin. Other factors are the age and genetic makeup of the person
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exposed to the chemical, and how well that person’s detoxification systems (such as the liver, lungs, and kidneys) work. The damage to health resulting from exposure to a chemical is called the response. One type of response, an acute effect, is an immediate or rapid harmful reaction ranging from dizziness and nausea to death. A chronic effect is a permanent or long-lasting consequence (kidney or liver damage, for example) of exposure to a single dose or to repeated lower doses of a harmful substance.
Scientists Use Live Laboratory Animals and Non-Animal Tests to Estimate Toxicity The most widely used method for determining toxicity is to expose a population of live laboratory animals to measured doses of a specific substance under controlled
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Figure 11-8 Science: Scientist use two types of dose-response curves to help them estimate the toxicity of various chemicals. The linear and nonlinear curves in the left graph apply if even the smallest dosage of a chemical has a harmful effect that increases with the dosage. The curve on the right applies if a harmful effect occurs only when the dosage exceeds a certain threshold level. Which model is better for measuring the effects of a specific harmful agent is uncertain and controversial because of the difficulty in estimating the responses to very low dosages.
Nonlinear dose-response
Effect
Effect
Linear doseresponse
Threshold level Dose
Dose Threshold
No threshold
conditions and to measure the animals’ responses. Animal tests take 2–5 years, involve hundreds to thousands of test animals, and cost as much as $2 million per substance tested. Such tests can be painful to the test animals and can kill or harm them. Animal welfare groups want to limit or ban the use of test animals and, at the very least, to ensure that they are treated in the most humane manner possible. Scientists estimate the toxicity of a chemical by determining the effects of various doses of the chemical on test organisms and plotting the results in a doseresponse curve (Figure 11-8). One approach is to determine the lethal dose—the dose that will kill an animal. A chemical’s median lethal dose (LD50) is the dose that can kill 50% of the animals (usually rats and mice) in a test population within an 18-day period. There are two general types of dose-response curves. With the nonthreshold dose-response model (Figure 11-8, left), any dosage of a toxic chemical causes harm that increases with the dosage. With the threshold dose-response model (Figure 11-8, right), a certain level of the chemical must be reached before any detectable harmful effects occur, presumably because the body can ward off or repair the damage caused by low dosages of some substances. Chemicals vary widely in their toxicity (Table 11-1). Some poisons can cause serious harm or death after a
single exposure at very low dosages. Others cause such harm only at dosages so huge that it is nearly impossible to get enough into the body to cause injury or death. Most chemicals fall between these two extremes. Establishing which model applies at low dosages is extremely difficult and controversial. To be on the safe side, scientists often choose the no-threshold doseresponse model. Fairly high dosages are used to reduce the number of test animals needed, obtain results quickly, and lower costs. Otherwise, manufacturers would need to run tests on millions of laboratory animals for many years, and they could not afford to test most chemicals. For the same reasons, scientists usually use mathematical models to extrapolate, or estimate, the effects of low-dose exposures based on the measured results of high-dose exposures. Then they extrapolate these results from test organisms to humans as a way of estimating LD50 values for acute toxicity (Table 11-1). Some scientists challenge the validity of extrapolating data from test animals to humans, because human physiology and metabolism often differ from those of the test animals. Other scientists say that such tests and models work fairly well (especially for revealing cancer risks) when the correct experimental animal is chosen or when a chemical is toxic to several different testanimal species.
Table 11-1 Toxicity Ratings and Average Lethal Doses for Humans Toxicity Rating
LD50 (milligrams per kilogram of body weight)*
Average Lethal Dose**
Examples
Supertoxic
Less than 5
Less than 7 drops
Nerve gases, botulism toxin, mushroom toxin, dioxin (TCDD)
Extremely toxic
5–50
7 drops to 1 teaspoon
Potassium cyanide, heroin, atropine, parathion, nicotine
Very toxic
50–500
1 teaspoon to 1 ounce
Mercury salts, morphine, codeine
Moderately toxic
500–5,000
1 ounce to 1 pint
Lead salts, DDT, sodium hydroxide, sodium fluoride, sulfuric acid, caffeine, carbon tetrachloride
Slightly toxic
5,000–15,000
1 pint to 1 quart
Ethyl alcohol, Lysol, soaps
Essentially nontoxic
15,000 or greater
More than 1 quart
Water, glycerin, table sugar
*Dosage that kills 50% of individuals exposed. **Amounts of substances in liquid form at room temperature that are lethal when given to a 70-kilogram (150-pound) human.
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More humane methods for toxicity testing are available and are being used more often to replace GOOD testing on live animals. They include making NEWS computer simulations and using tissue cultures of cells and bacteria, chicken egg membranes, and individual animal cells, instead of whole, live animals. High-speed robotic testing devices can now screen the biological activity of more than one million compounds a day to help determine their possible toxic effects. There are several problems with estimating toxicities by using laboratory experiments (Concept 11-4A). In real life, each of us is exposed to a variety of chemicals, some of which can interact in ways that decrease or enhance their short- and long-term individual effects. Toxicologists already have great difficulty in estimating the toxicity of a single substance. Adding the problem of evaluating mixtures of potentially toxic substances, separating out which are the culprits, and determining how they can interact with one another is overwhelming from a scientific and economic standpoint. For example, just studying the interactions of 3 of the 500 most widely used industrial chemicals would take 20.7 million experiments—a physical and financial impossibility.
There Are Other Ways to Estimate the Harmful Effects of Chemicals Scientists use several other methods to get information about the harmful effects of chemicals on human health. For example, case reports, usually made by physicians, provide information about people suffering an adverse health effect or dying after exposure to a chemical. Such information often involves accidental or deliberate poisonings, drug overdoses, homicides, or suicide attempts. Most case reports are not reliable sources for estimating toxicity because the actual dosage and the exposed person’s health status are often unknown. But such reports can provide clues about environmental hazards and suggest the need for laboratory investigations. Another source of information is epidemiological studies, which compare the health of people exposed to a particular chemical (the experimental group) with the health of a similar group of people not exposed to the agent (the control group). The goal is to determine whether the statistical association between exposure to a toxic chemical and a health problem is strong, moderate, weak, or undetectable. Four factors can limit the usefulness of epidemiological studies. First, in many cases, too few people have been exposed to high-enough levels of a toxic agent to detect statistically significant differences. Second, the studies usually take a long time. Third, closely linking an observed effect with exposure to a particular chemical is difficult because people are exposed to many dif-
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ferent toxic agents throughout their lives and can vary in their sensitivity to such chemicals. Fourth, we cannot use epidemiological studies to evaluate hazards from new technologies or chemicals to which people have not yet been exposed.
Are Trace Levels of Toxic Chemicals Harmful? Should we be concerned about trace amounts of various synthetic chemicals in air, water, food, and our bodies? The honest answer is that, in most cases, we do not know because there is too little data and because of the difficulty in determining the effects of exposures to low levels of these chemicals. Some scientists view trace amounts of such chemicals with alarm, especially because of their potential long-term effects on the human immune, nervous, and endocrine systems. Others view the risks from trace levels as minor. They point out that average life expectancy has been increasing in most countries, especially moredeveloped countries, for decades. Also, chemists are able to detect increasingly smaller amounts of potentially toxic chemicals in air, water, and food. This is good news, but it can give the false impression that dangers from toxic chemicals are increasing. In some cases, we may simply be uncovering levels of chemicals that have been around for a long time.
Why Do We Know So Little about the Harmful Effects of Chemicals? As we have seen, all methods for estimating toxicity levels and risks have serious limitations (Concept 11-4A). But they are all we have. To take this uncertainty into account and to minimize harm, scientists and regulators typically set allowed levels of exposure to toxic substances at 1/100 or even 1/1,000 of the estimated harmful levels. According to risk assessment expert Joseph V. Rodricks, “Toxicologists know a great deal about a few chemicals, a little about many, and next to nothing about most.” The U.S. National Academy of Sciences estimates that only 10% of 100,000 registered synthetic chemicals in commercial use have been thoroughly screened for toxicity, and only 2% have been adequately tested to determine whether they are carcinogens, mutagens, or teratogens. Hardly any of the chemicals in commercial use have been screened for possible damage to the human nervous, endocrine, and immune systems. Because of insufficient data and the high costs of regulation, federal and state governments do not regulate the use of nearly 99.5% of the commercially available chemicals in the United States.
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How Far Should We Go in Using Pollution Prevention and the Precautionary Principle? We know little about the potentially toxic chemicals around us and inside of us, and estimating their effects is very difficult, time-consuming, and expensive. So where does this leave us? Some scientists and health officials, especially those in European Union countries, are pushing for much greater emphasis on pollution prevention. They say we should not release into the environment chemicals that we know or suspect can cause significant harm. This means looking for harmless or less harmful substitutes for toxic and hazardous chemicals. Another option is to recycle them within production processes to keep them from reaching the environment. Pollution prevention is a strategy for implementing the precautionary principle. According to this principle, when there is substantial preliminary evidence that an activity, technology, or chemical substance can harm humans or the environment, we should take precautionary measures to prevent or reduce such harm, rather than waiting for more conclusive (reliable) scientific evidence (Concept 11-4B). With this approach, those proposing to introduce a new chemical or technology would bear the burden of establishing its safety. This requires two major changes in the way we evaluate risks. First, we would assume that new chemicals and technologies are harmful until scientific studies could show otherwise. Second, we would remove from the market existing chemicals and technologies that appear to have a strong chance of causing significant harm until we could establish their safety. Some movement is being made in this direction, especially in the European Union. In 2000, negotiators agreed to a global treaty that would ban or phase out use of 12 of the most notorious persistent organic pollutants
(POPs), also called the dirty dozen. The list includes DDT and a number of other pesticides, PCBs, and dioxins. In 2009, nine more POPs were added, some of which are widely used in pesticides and in flame retardants added to clothing, furniture, and other consumer goods. The POPs treaty went into effect in 2004 but has not been ratified and implemented by the United States. In 2007, the European Union enacted regulations known as REACH (for registration, evaluation, and authorization of chemicals). It required the registration of 30,000 untested, unregulated, and potentially harmful chemicals. In the REACH process, the most hazardous substances are not approved for use if safer alternatives exist. In addition, when there is no alternative, producers must present a research plan aimed at finding one. While conventional regulation has put the burden on governments to show that chemicals are dangerous, REACH puts more of the burden on industry to show that they are safe. Manufacturers and businesses contend that widespread application of this approach would make it too expensive and almost impossible to introduce any new chemical or technology. They argue that we will never have a risk-free society. Proponents of increased reliance on pollution prevention agree that we can go too far, but argue we have an ethical responsibility to reduce known or potentially serious risks to human health and to our life-support system. They also point out that using the precautionary principle focuses the efforts and creativity of scientists, engineers, and businesses on finding solutions to pollution problems based on prevention rather than on cleanup. HOW WOULD YOU VOTE?
✓ ■
Should we rely more on the use of the precautionary principle to implement pollution prevention as a way to reduce the potential risks from chemicals and technologies? Cast your vote online at www.cengage.com/login.
11-5 How Do We Perceive Risks and
How Can We Avoid the Worst of Them? ▲
We can reduce the major risks we face by becoming informed, thinking critically about risks, and making careful choices.
CONC EPT 11-5
The Greatest Health Risks Come from Poverty, Gender, and Lifestyle Choices Risk analysis involves identifying hazards and evaluating their associated risks (risk assessment; Figure 11-1, left), ranking risks (comparative risk analysis), determin-
ing options, and making decisions about reducing or eliminating risks (risk management; Figure 11-1, right). A related activity is to inform decision makers and the public about risks (risk communication). Risk evaluators use statistical probabilities based on past experience, animal testing, and other information to estimate risks from older technologies and chemicals.
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Cause of death
Annual deaths
Poverty/malnutrition/ disease cycle
11 million (150)
Tobacco
5.4 million (74)
Pneumonia and flu
3.2 million (44)
Air pollution
2.4 million (33)
HIV/AIDS
2 million (27)
Diarrhea
1.6 million (22)
Tuberculosis
1.5 million (21)
Automobile accidents
1.2 million (16)
Work-related injury and disease
1.1 million (15)
Malaria
1 million (14)
Hepatitis B
1 million (14)
Measles
800,000 (11)
Figure 11-9 Global outlook: Scientists have estimated the number of deaths per year in the world from various causes. Numbers in parentheses represent death tolls in terms of the number of fully loaded 200-passenger jet airplanes crashing every day of the year with no survivors. Because of the lack of media coverage of most of these causes of death and sensational media coverage of other causes of death, most people are misinformed and guided by irrational fears about the comparative levels of risk. Question: Which three of these hazards are most likely to shorten your life span? (Data from World Health Organization, 2007)
To evaluate new technologies and products, risk evaluators use more uncertain statistical probabilities, based on models rather than on actual experience and testing. The greatest risks that many people face today are rarely dramatic enough to make the daily news. In terms of the number of premature deaths per year (Figure 11-9) and reduced life span (Figure 11-10), the greatest risk by far is poverty. The high death toll ultimately resulting from poverty is caused by malnutrition, increased susceptibility to normally nonfatal infectious diseases, and often-fatal infectious diseases transmitted by unsafe drinking water. After poverty and gender, the greatest risks of premature death result primarily from lifestyle choices that people make (Figures 11-9 and 11-10). The best ways to reduce one’s risk of premature death and serious health problems are to avoid smoking and exposure to smoke (see the Case Study that follows), lose excess weight, reduce consumption of foods containing cholesterol and saturated fats, eat a variety of fruits and vegetables, exercise regularly, drink little or no alcohol (no more than two drinks in a single day), avoid excess sunlight (which ages skin and can cause skin cancer), and practice safe sex (Concept 11-5). A 2005 study by Majjid Ezzati, with participation by 100 scientists around the world, estimated that one-third of the 7.6 million annual deaths from cancer could be prevented if individuals were to follow these guidelines. ■ CAS E STUDY
Death from Smoking What is roughly the diameter of a 30-caliber bullet, can be bought almost anywhere, is highly addictive, and kills an average of about 14,800 people every day, or
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about one every 6 seconds? It is a cigarette. Cigarette smoking is the world’s most preventable major cause of suffering and premature death among adults. In 2007, the WHO estimated that tobacco use contributed to the premature deaths of 100 million people during the 20th century and could kill 1 billion people during this century unless smoking is dramatically reduced. The WHO estimates that each year, tobacco contributes to the premature deaths of at least 5.4 million people (about half from more-developed and half from less-developed countries) from 25 illnesses including heart disease, stroke, lung and other cancers, and bronchitis. Another disease related to smoking is emphysema, which results in irreversible damage to air sacs in the lung and chronic shortness of breath. According to the WHO, lifelong smokers reduce their life spans by an average of 15 years. By 2030, the annual death toll from smoking-related diseases is projected to reach more than 8 million—an average of 21,900 preventable deaths per day. About 80% of these deaths are expected to occur in less-developed countries, especially China, where 30% of the world’s smokers live. According to the U.S. Centers for Disease Control and Prevention (CDC), smoking kills about 442,000 Americans per year—an average of 1,211 deaths per day, or nearly one every minute (Figure 11-11). This death toll is roughly equivalent to six fully loaded 200passenger jet planes crashing every day of the year with no survivors! Yet, this ongoing major human tragedy in the United States and throughout the world rarely makes the news. The overwhelming scientific consensus is that the nicotine inhaled in tobacco smoke is highly addictive.
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Shortens average life span in the United States by
Hazard
7–10 years
Poverty
7.5 years
Born male Smoking
6–10 years
Overweight (35%)
6 years
Unmarried
5 years
Overweight (15%)
2 years
Spouse smoking
1 year
Driving
7 months
Air pollution
5 months
Alcohol
5 months
Drug abuse
4 months
Flu
4 months
AIDS
3 months
Drowning
1 month
Pesticides
1 month
Fire
1 month
Natural radiation
8 days
Medical X rays
5 days
Oral contraceptives
5 days
Toxic waste
4 days
Flying
1 day
Hurricanes, tornadoes
1 day
Living lifetime near nuclear plant
10 hours
Figure 11-10 Global outlook: This figure compares key risks that people can face, expressed in terms of an estimated shortened average life span (Concept 11-5). Except for poverty and gender, the greatest risks people face come primarily from the lifestyle choices they make. These are merely generalized relative estimates. Individual responses to these risks differ because of factors such as genetic variation, family medical history, emotional makeup, stress, and social ties and support. Question: Which three of these factors are most likely to shorten your life span? (Data from Bernard L. Cohen)
Only one in ten people who try to quit smoking succeeds. Smokers suffer about the same relapse rate as do recovering alcoholics and those addicted to heroin or
Cause of Death
Deaths per Year
Tobacco use
442,000
Accidents Alcohol use Infectious diseases Pollutants/toxins Suicides
101,500 (33,960 auto) 85,000
crack cocaine. A British government study showed that adolescents who smoke more than just one cigarette have an 85% chance of becoming addicted to nicotine. Studies also show that passive smoking, or breathing secondhand smoke, poses health hazards for children and adults. Children who grow up living with smokers are more likely to develop allergies and asthma. Among adults, nonsmoking spouses of smokers have a 30% higher risk of both heart attack and lung cancer than spouses of nonsmokers have. In 2006, the CDC estimated that each year, secondhand smoke causes an
75,000 (15,000 from AIDS) 55,000 30,600
Homicides
20,622
Illegal drug use
17,000
Figure 11-11 Smoking is by far the nation’s leading cause of preventable death, causing more premature deaths each year than all the other categories in this figure combined. (Data from U.S. National Center for Health Statistics, Centers for Disease Control and Prevention, and U.S. Surgeon General)
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estimated 3,000 lung cancer deaths and 46,000 deaths from heart disease in the United States. A study published in 2004 by Richard Doll and Richard Peto found that kicking the habit—even at 50 years of age—can cut a person’s risk of premature death in half. If people quit smoking by the age of 30, they can avoid nearly all the risk of dying prematurely, but again, the longer one smokes, the harder it is to quit. There is some encouraging news: the average number of cigarettes smoked per person in the United GOOD States declined by 56% between 1976 and 2006, NEWS and dropped globally by 16% between 1988 and 2004. That number is dropping in most other countries, as well. In the United States, the percentage of adults who smoke dropped from roughly 40% in the 1960s to 21% in 2008. Such declines can be attributed partly to media coverage about the harmful health effects of smoking and to the banning of smoking in workplaces, bars, restaurants, and public buildings. HOW WOULD YOU VOTE?
✓ ■
Do you favor banning the use of tobacco in all workplaces and public buildings? Cast your vote online at www.cengage .com/login.
Estimating Risks from Technologies Is Not Easy The more complex a technological system and the more people needed to design and run it, the more difficult it is to estimate the risks of using the system. The overall reliability or the probability (expressed as a percentage) that a person, device, or complex technological system will complete a task without failing is the product of two factors: System reliability (%) = Technology reliability (%) × Human reliability (%)
With careful design, quality control, maintenance, and monitoring, a highly complex system such as a nuclear power plant or space shuttle can achieve a high degree of technological reliability. But human reliability usually is much lower than technological reliability and is almost impossible to predict: To err is human. Suppose the technological reliability of a nuclear power plant is 95% (0.95) and human reliability is 75% (0.75). Then the overall system reliability is 71% (0.95 × 0.75 = 71%). Even if we could make the technology 100% reliable (1.0), the overall system reliability would still be only 75% (1.0 x 0.75 = 75%). The crucial dependence of even the most carefully designed systems on unpredictable human reliability helps to explain tragedies that had been deemed almost impossible, such as the Chernobyl nuclear power plant accident (see Chapter 9, Case Study, p. 200) and the Challenger and Columbia space shuttle accidents. One way to make a system more foolproof is to move more of the potentially fallible elements from the
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human side to the technological side. However, chance events such as a lightning strike can knock out an automatic control system, and no machine or computer program can completely replace human judgment. Also, the parts in any automated control system are manufactured, assembled, tested, certified, and maintained by fallible human beings. In addition, computer software programs used to monitor and control complex systems can be flawed because of human error or can be deliberately sabotaged to cause them to malfunction.
Most People Do a Poor Job of Evaluating Risks Most of us are not good at assessing the relative risks from the hazards that surround us. Many people deny or shrug off the high-risk chances of death or injury from voluntary activities they enjoy such as motorcycling (1 death in 50 participants), smoking (1 in 250 by age 70 for a pack-a-day smoker), hang gliding (1 in 1,250), and driving (1 in 3,300 without a seatbelt and 1 in 6,070 with a seatbelt). Indeed, the most dangerous thing that most people in many countries do each day is to drive or ride in a car. Yet some of these same people may be terrified about their chances of being killed by the flu (1 in 130,000), a nuclear power plant accident (1 in 200,000), West Nile virus (1 in 1 million), lightning (1 in 3 million), a commercial airplane crash (1 in 9 million), snakebite (1 in 36 million), or shark attack (1 in 281 million). Five factors can cause people to see a technology or a product as being more or less risky than experts judge it to be. First is fear. Many people fear a new, unknown product or technology more than they do an older, more familiar one. For example, some people fear genetically modified food and trust food produced by traditional plant-breeding techniques. Second is the degree of control we have in a given situation. Most of us have a greater fear of things over which we do not have personal control. For example, some individuals feel safer driving their own car for long distances through bad traffic than traveling the same distance on a plane. But look at the numbers. The risk of dying in a car accident in the United States while using a seatbelt is 1 in 6,070, whereas the risk of dying in a commercial airliner crash is 1 in 9 million. Third is whether a risk is catastrophic, not chronic. We usually are more frightened by news of catastrophic accidents such as a plane crash than we are of a cause of death such as smoking, which has a much larger death toll spread out over time. Fourth, some people suffer from optimism bias, the belief that risks that apply to other people do not apply to them. Although people get upset when they see others driving erratically while talking on a cell phone or text messaging, they may believe that talking on the cell phone or text messaging does not impair their own driving ability.
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about risks over which you have no control. But you do have control over major ways to reduce risks from heart attack, stroke, and many forms of cancer because you can decide whether to smoke, what to eat, and how much alcohol to drink. Focus on avoiding these and other true risks and you will have a much greater chance of living a longer, healthier, happier, and less fearful life.
A fifth factor is that many of the risky things we do are highly pleasurable and give instant gratification, while the potential harm from such activities comes later. Examples are smoking cigarettes, eating lots of ice cream, and getting a tan.
Several Principles Can Help Us Evaluate and Reduce Risk Here are some guidelines for evaluating and reducing risk (Concept 11-5): •
Compare risks. Is there a risk of getting cancer by eating a charcoal-broiled steak once or twice a week for a lifetime? Yes, because almost any chemical can harm you if the dose is large enough. The question is whether this danger is great enough for you to worry about. In evaluating a risk, the key question is not “Is it safe?” but rather “How risky is it compared to other risks?”
•
Determine how much risk you are willing to accept. For most people, a 1 in 100,000 chance of dying or suffering serious harm from exposure to an environmental hazard is a threshold for changing their behavior. Others might accept a higher or lower probability.
•
•
Determine the actual risk involved. The news media usually exaggerate the daily risks we face in order to capture our interest and sell newspapers and magazines or gain television viewers. As a result, most people who take a daily dose of such exaggerated reports believe that the world is much more riskfilled than it really is. Concentrate on evaluating and carefully making important lifestyle choices. There is no point in worrying
Finally, we can use the three principles of sustainability (see back cover) to help us reduce major risks to our health. If we depend more on the sun, shifting from nonrenewable fossil fuels to renewable energy, we might reduce pollution and the threats of climate change. By cutting down on waste of energy and matter resources and by reusing and recycling them, we will help to provide enough resources for most people to avoid poverty. We can also emphasize the use of diverse strategies for solving environmental and health problems, and especially for reducing poverty and controlling population growth. Here are this chapter’s three big ideas: ■ We face significant hazards from infectious diseases such as flu, AIDS, diarrheal diseases, malaria, and tuberculosis; from exposure to chemicals that can cause cancers and birth defects, and disrupt the human immune, nervous, and endocrine systems; and from certain lifestyle choices. ■ Because of the difficulty in evaluating the harm caused by exposure to chemicals, many health scientists call for much greater emphasis on pollution prevention. ■ Becoming informed, thinking critically about risks, and making careful choices can reduce the major risks we face.
The burden of proof imposed on individuals, companies, and institutions should be to show that pollution prevention options have been thoroughly examined, evaluated, and used before lesser options are chosen. JOEL HIRSCHORN
REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 226. Define and distinguish among risk, risk assessment, and risk management. Distinguish between possibility and probability. What is a pathogen? Give an example of a risk from each of the following: a biological hazard, a chemical hazard, a physical hazard, a cultural hazard, and a lifestyle choice. 2. Define and distinguish among an infectious disease, a transmissible disease, and a nontransmissible disease, and give an example of each. Describe five possible
pathways for infectious diseases. Distinguish between an epidemic and a pandemic of an infectious disease. Describe the causes and possible solutions for the increasing genetic resistance in microbes to commonly used antibiotics. 3. Describe the global threat from tuberculosis. Describe the health threats from the global HIV/AIDS pandemic and the effects it can have on a population. Describe the threats from the hepatitis B, West Nile, and SARS viruses. What are emergent diseases? Describe the threat from malaria for 40% of the world’s people and how we can reduce this WWW.CENGAGEBRAIN.COM
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so little about the harmful effects of chemicals? Discuss the use of pollution prevention and the precautionary principle in dealing with health threats from chemicals.
threat. List eight ways to prevent or reduce the incidence of infectious diseases. 4. What is a toxic chemical? Distinguish among mutagens, teratogens, and carcinogens, and give an example of each. Describe the human immune, nervous, and endocrine systems and give an example of a chemical that can threaten each of these systems. What are hormonally active agents, what risks do they pose, and how can we reduce these risks? Summarize the hazards of mercury in the environment.
7. What is risk analysis? Distinguish among risk assessment, comparative risk analysis, risk management, and risk communication. In terms of premature deaths, what are the three greatest threats that humans face? Summarize the dangers of using tobacco products. 8. How can we estimate the risks from complex technologies? How can we reduce the threats from the use of various technologies?
5. Define toxicology, toxicity, dose, and response. Describe how we can estimate the toxicity of a substance by using laboratory animals and discuss the limitations of this approach. What is a dose-response curve? Describe how toxicities are estimated by case reports and epidemiological studies, and discuss the limitations of these approaches.
10. How can we use the three principles of sustainability to help us in reducing the major risks to our health?
6. Are trace levels of toxic chemicals harmful? Discuss the controversy surrounding this question. Why do we know
Note: Key terms are in bold type.
9. What five factors cause people to misjudge risks? List four strategies that help us to evaluate and reduce risk.
CRITICAL THINKING c. We should not worry much about exposure to toxic chemicals because we can use genetic engineering to reduce our susceptibility to the effects of those chemicals.
1. List three ways in which you could apply Concept 11-5 to making your lifestyle more environmentally sustainable while reducing the major risks you face. 2. How can changes in the age structure of a human population increase the spread of infectious diseases? How can the spread of infectious diseases such as HIV/AIDS affect the age structure of human populations? 3. What are three actions you would take to reduce the global threats to human health and life from (a) tuberculosis and (b) malaria? 4. Evaluate the following statements: a. We should not worry about exposure to toxic chemicals because almost any chemical at a large enough dosage can cause some harm. b. We should not worry much about exposure to toxic chemicals because, through genetic adaptation, we can develop immunity to such chemicals.
5. What are the three major risks you face from (a) your lifestyle, (b) where you live, and (c) what you do for a living? Which of these risks are voluntary and which are involuntary? List the three most important things you can do to reduce these risks. Which of these things do you plan to do? 6. Would you support legislation requiring the use of pollution prevention to implement the precautionary principle in deciding what to do about risks from chemicals in the United States or the country where you live? Explain. 7. List two questions that you would like to have answered as a result of reading this chapter.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 11 for many study aids and ideas for further
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CHAPTER 11
reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
Environmental Hazards and Human Health
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Air Pollution, Climate Change, and Ozone Depletion
12
Key Questions and Concepts 12-1
What is the nature of the atmosphere?
C O N C E P T 1 2 - 1 The two innermost layers of the atmosphere are the troposphere, which supports life, and the stratosphere, which contains the protective ozone layer.
12-2 What are the major outdoor air pollution problems? C O N C E P T 1 2 - 2 Pollutants mix in the air to form industrial smog, primarily as a result of burning coal, and photochemical smog, caused by emissions from motor vehicles, industrial facilities, and power plants.
Acid deposition is mainly caused by emissions from coal-burning power plants and motor vehicles, and in some regions it threatens human health, aquatic life and ecosystems, forests, and man-made structures. CONCEPT 12-3
What are the major indoor air pollution problems?
12-4
The most threatening indoor air pollutants are smoke and soot from wood and coal fires (mostly in less-developed countries), cigarette smoke, and chemicals used in building materials and in many consumer products. 12-5
How should we deal with air pollution?
Legal, economic, and technological tools can help us to clean up air pollution, but the best solution is to prevent it. CONCEPT 12-5
C O N C E P T 1 2 - 6 A Evidence indicates that the earth’s atmosphere is warming because of a combination of natural effects and human activities, and that this warming is likely to lead to significant climate change during this century. C O N C E P T 1 2 - 6 B The projected rapid change in the atmosphere’s temperature could have severe and longlasting consequences, including increased drought and flooding, rising sea levels, and shifts in the locations of croplands and wildlife habitats.
12-3 What is acid deposition and why is it a problem?
CONCEPT 12-4
12-6 In the future, how might the earth’s temperature and climate change, and with what effects?
What can we do to slow projected climate change? 12-7
C O N C E P T 1 2 - 7 To slow the projected rate of atmospheric warming and climate change, we can increase energy efficiency, sharply reduce greenhouse gas emissions, rely more on renewable energy resources, and slow population growth.
12-8 How have we depleted ozone in the stratosphere and what can we do about it? C O N C E P T 1 2 - 8 A Our widespread use of certain chemicals has reduced ozone levels in the stratosphere, which allows more harmful ultraviolet radiation to reach the earth’s surface. C O N C E P T 1 2 - 8 B To reverse ozone depletion, we must stop producing ozone-depleting chemicals and comply with the international treaties that ban such chemicals.
Pollution is nothing but the resources we are not harvesting. We allow them to disperse because we’ve been ignorant of their value. RICHARD BUCKMINSTER (BUCKY) FULLER
Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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12-1 What Is the Nature of the Atmosphere? ▲
The two innermost layers of the atmosphere are the troposphere, which supports life, and the stratosphere, which contains the protective ozone layer.
C O NC EPT 12-1
The Atmosphere Consists of Several Layers We live under a thin blanket of gases surrounding the earth, called the atmosphere. It is divided into several spherical layers (Figure 12-1). Our focus in this book is on the atmosphere’s two innermost layers: the troposphere and the stratosphere. About 75–80% of the earth’s air mass is found in the troposphere, the atmospheric layer closest to the earth’s surface. This layer extends only about 17 kilometers (11 miles) above sea level at the equator and 6 kilometers (4 miles) over the poles. If the earth were the size of an apple, this lower layer containing the air we breathe would be no thicker than the apple’s skin.
120
Atmospheric pressure (millibars) 200 400 600 800
0
1,000 75
Temperature 110
Thermosphere
65
100 90
55
Mesosphere
70
45
60 35 50
Altitude (miles)
Altitude (kilometers)
80
Stratosphere
40
25
Take a deep breath. About 99% of the air you inhaled consists of two gases: nitrogen (78%) and oxygen (21%). The remainder consists of water vapor (varying from 0.01% at the frigid poles to 4% in the humid tropics), 0.93% argon (Ar), 0.039% carbon dioxide (CO2), and trace amounts of dust and soot particles as well as other gases including methane (CH4), ozone (O3), and nitrous oxide (N2O). The troposphere is a dynamic system involved in the chemical cycling of the earth’s vital nutrients. Its rising and falling air currents and winds play a major role in the planet’s short-term weather and long-term climate. The atmosphere’s second layer is the stratosphere, which extends from about 17–48 kilometers (11–30 miles) above the earth’s surface (Figure 12-1). Although the stratosphere contains less matter than the troposphere, its composition is similar, with two notable exceptions: its volume of water vapor is about 1/1,000 that of the troposphere and its concentration of ozone is much higher. Much of the atmosphere’s small amount of ozone is concentrated in a portion of the atmosphere called the ozone layer, found within the stratosphere at roughly 17–30 kilometers (11–19 miles) above sea level. Stratospheric ozone is produced when some of the oxygen molecules there interact with ultraviolet (UV) radiation emitted by the sun. This “global sunscreen” of stratospheric ozone keeps about 95% of the sun’s harmful UV radiation from reaching the earth’s surface. It allows humans and other forms of life to exist on land and helps protect us from sunburn, skin and eye cancers, cataracts, and damage to our immune systems. It also prevents much of the oxygen in the troposphere from being converted to photochemical ozone, a harmful air pollutant (Concept 12-1).
30 Ozone layer
20
15
Earth Has Many Different Climates 10 (Sea 0 level)
Pressure
–80
–40
Troposphere
0 40 80 Temperature (˚C)
120
5 Pressure = 1,000 millibars at ground level
Figure 12-1 Natural capital: The earth’s atmosphere is a dynamic system that includes four layers. The average temperature (gray line) of the atmosphere varies with altitude and with differences in the absorption of incoming solar energy. Most ultraviolet radiation from the sun is absorbed by ozone (O3), found primarily in the stratosphere’s ozone layer, 17–30 kilometers (11–19 miles) above sea level. Question: Why do you think most of the planet’s air is in the troposphere?
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Weather is an area’s short-term temperature, precipitation, humidity, wind speed, cloud cover, and other atmospheric conditions measured over time periods of hours or days. Climate is an area’s general pattern of atmospheric or weather conditions over long periods of time ranging from at least three decades to thousands of years. Average temperature and average precipitation are the two main factors determining climate, along with the closely related factors of latitude (distance from the equator) and altitude. The earth’s major climate zones are shown in Figure 12-2.
Air Pollution, Climate Change, and Ozone Depletion
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ska Ala ent r cur ific c a P th ft Nor dri
rth No
m
Ku
nt
dr i
S
th
equ
a t o ri a l c u r re
nt
an cu rren t
Be ng ue la
Capricorn
ou
current
Peru current
Bra zil c urrent
Tropic of
ft
equatorial curren North t
So
South equatorial current
North equatorial current
onso
r
re
M
Gu inea curr ent ut he quatorial cu r r e nt
drift
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li tra us tA Wes
West wind drift
re
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us tral ian c u
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nc
on
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Car i b
Equatorial countercurrent
West w i nd
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Oy curre nt
ea
Ca na ries
u
st r
G
lf
rren t
u ia c Californ
Cancer
en
ash
b La
r
Tropic of
ift dr tic n a l At r
t
ad
Circle
io cu r
o r c u rr e n
Arctic
Figure 12-2 Natural capital: This generalized map of the earth’s current climate zones shows the major contributing ocean currents and drifts. Question: Based on this map, what is the general type of climate where you live?
West wind drift
Antarctic Circle
Polar (ice) Warm temperate
Subarctic (snow) Dry
Cool temperate Tropical
Highland
Major upwelling zones
Climate varies in different parts of the earth mostly because patterns of global air circulation and ocean currents distribute heat and precipitation unevenly. Three major factors determine how air circulates in the lower atmosphere and how it helps distribute heat and moisture from the tropics to other parts of the world. First is the uneven heating of the earth’s surface by the sun. Air is heated much more at the equator, where the sun’s rays strike directly, than at the poles, where sunlight strikes at a slanted angle and spreads out over a much greater area. Hence, tropical regions near the equator are hot, polar regions are cold, and temperate regions in between generally have intermediate average temperatures. The second major factor is rotation of the earth on its axis. Because the earth’s equator spins faster than its polar regions, heated air masses rising above the equator and moving north and south to cooler areas are deflected to the west or east over different parts of the planet’s surface. The direction of air movement in the resulting huge atmospheric regions called cells (Figure 12-3) sets up belts of prevailing winds: major surface winds that blow almost continuously and help distribute air, heat, and moisture over the earth’s surface. A third factor affecting global air circulation is properties of air, water, and land. Heat from the sun evaporates ocean water and transfers heat from the oceans to the atmosphere, especially near the hot equator. This evaporation of water creates giant cyclical convection cells that circulate air, heat, and moisture both vertically and from place to place in the atmosphere.
Warm ocean current
River
Cold ocean current
Moist air rises, cools, and releases moisture as rain Polar cap Arctic tundra Evergreen 60° coniferous forest Temperate deciduous forest and grassland Desert
30°
Tropical deciduous forest Equator
0° Tropical rain forest Tropical deciduous forest 30°
60°
Polar cap
Desert Temperate deciduous forest and grassland
Figure 12-3 Global air circulation, ocean currents, and biomes: Heat and moisture are distributed over the earth’s surface by six giant convection cells at different latitudes. The resulting uneven distribution of heat and moisture over the planet’s surface leads to the forests, grasslands, and deserts that make up the earth’s terrestrial biomes (see also Figure 3-5, p. 58)
CONCEPT 12-1 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Prevailing winds blowing over the oceans produce mass movements of surface water called ocean currents. The earth’s major ocean currents help to redistribute heat around the planet, thereby influencing climate and vegetation, especially near coastal areas. The earth’s air circulation patterns, prevailing winds, and mixture of continents and oceans result in six giant convection cells (Figure 12-3) in which warm, moist air rises and cools, and the cool, dry air sinks. This leads to an irregular distribution of climates and deserts, grasslands, and forests, as shown in Figure 12-2.
Greenhouse Gases Warm the Lower Atmosphere Small amounts of certain gases in the atmosphere, including water vapor (H2O), carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), play a role in
determining the earth’s average temperatures and thus its climates. These greenhouse gases allow mostly visible light and some infrared radiation and ultraviolet (UV) radiation from the sun to pass through the atmosphere. The earth’s surface absorbs much of this solar energy and transforms it to longer-wavelength infrared radiation (heat), which then rises into the troposphere. Some of this heat escapes into space, but some is absorbed by molecules of greenhouse gases and emitted into the lower atmosphere as even longer-wavelength infrared radiation. Some of this released energy radiates into space, and some warms the lower atmosphere and the earth’s surface. Recall that this natural warming effect of the troposphere is called the greenhouse effect (see Figure 2-10, p. 33). Without the warming caused by these greenhouse gases, the earth would be a cold and mostly lifeless planet. When concentrations of these gases rise, they tend to make the atmosphere warmer, which scientists believe, is happening now.
12-2 What Are the Major
Outdoor Air Pollution Problems? ▲
Pollutants mix in the air to form industrial smog, primarily as a result of burning coal, and photochemical smog, caused by emissions from motor vehicles, industrial facilities, and power plants.
C O NC EPT 12-2
Air Pollution Comes from Natural and Human Sources Air pollution is the presence of chemicals in the atmosphere in concentrations high enough to harm organisms, ecosystems, or human-made materials, or to alter
climate. Note that almost any chemical in the atmosphere can become a pollutant if it occurs in a high enough concentration. The effects of air pollution range from annoying to lethal. Table 12-1 lists the major classes and sources of air pollutants. Most of these air pollutants are gases or vol-
Table 12-1 Major Air Pollutants and Their Sources Pollutant
Sources
Pollutant
Sources
Carbon oxides Carbon monoxide (CO) Carbon dioxide (CO2)
Industries, motor vehicles, forest and grassland fires, open fires and poorly designed stoves for indoor cooking (CO), faulty furnaces (CO)
Nitrogen oxides Nitric oxide (NO) Nitrogen dioxide (NO2) Nitrous oxide (N2O)
Industries, motor vehicles, fires, volcanoes, fertilized cropland (N2O), woodstoves, unvented gas stoves, kerosene heaters
Volatile organic compounds (VOCs) Methane (CH4) Isoprene (C3H6) Benzene (C6H6)
Industries, green plants (isoprene), natural gas wells (CH4) and facilities, aerosol sprays, paint strippers and thinners
Ozone (O3)
Sulfur oxides Sulfur dioxide (SO2) Sulfur trioxide (SO3)
Coal-burning electric power plants, industries, volcanoes, reactions in the atmosphere
Reactions in the atmosphere resulting from a combination of nitrogen oxides, VOCs, and sunlight
Radioactive radon (Rn)
Released into homes from certain types of rock formations
Suspended particulate Soot (C) Lead (Pb) Sulfuric acid (H2SO4) Nitric acid (HNO3)
Industries, motor vehicles, windstorms, fires, volcanoes, reactions in the atmosphere (H2SO4 and HNO3), open fires and poorly designed stoves for indoor cooking (soot), tobacco smoke, pollen, pet dander, dust mites
Toxics Chlorine (Cl) Hydrogen sulfide (H2S) Formaldehyde (H2CO) Carbon tetrachloride (CCl4)
Industries, businesses such as dry cleaning (CCl4), decomposing plants (H2S), volcanoes (H2S), building materials (H2CO), carpets, furniture stuffing, paneling, particleboard, foam insulation
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Air Pollution, Climate Change, and Ozone Depletion
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from urban and industrial areas to the countryside and to other urban areas. Over the past 30 years, the quality of outdoor GOOD air in most of the more-developed countries has NEWS improved greatly. This has occurred primarily because grassroots pressure from citizens has led governments to pass and enforce air pollution control laws. On the other hand, according to the World Health Organization (WHO) more than 1.1 billion people (one of every six people on the earth) live in urban areas where outdoor air is unhealthy to breathe. Most of them live in densely populated cities in less-developed countries where air pollution control laws do not exist or are poorly enforced. However, the biggest pollution threat to poor people is indoor air pollution caused by their burning of wood, charcoal, coal, or dung in open fires or poorly designed stoves to heat their dwellings and cook their food. Cigarette smoke is another important part of this problem. Air pollution was once a regional problem limited mostly to cities. Now it is a global problem, largely due to the sheer volume of pollutants produced by human activities. Long-lived pollutants entering the atmosphere in India and China now find their way across the Pacific where they affect the west coast of North America. Even in arctic regions where very few people live, air pollutants flowing north from Europe, Asia, and North America collect to form arctic haze. There is no place on the planet that has not been affected by air pollution.
atile liquids that can evaporate into the air. Some, called suspended particulate matter (SPM), or aerosols, consist of tiny particles of solids or droplets of liquids suspended in the air. Air pollutants come from natural and human sources. Natural sources include wind-blown dust, pollutants from wildfires and volcanic eruptions, and volatile organic chemicals released by some plants. Most natural air pollutants are spread out over the globe or removed by chemical cycles, precipitation, and gravity. But in areas experiencing volcanic eruptions or forest fires, chemicals emitted by these events can temporarily reach harmful levels. Most human inputs of outdoor air pollutants occur in industrialized and urban areas where people, cars, and factories are concentrated. These pollutants are generated mostly by the burning of fossil fuels in power plants and industrial facilities (stationary sources) and in motor vehicles (mobile sources). Scientists classify outdoor air pollutants into two categories: Primary pollutants are chemicals or substances emitted directly into the air (Figure 12-4, center). While in the atmosphere, some primary pollutants react with one another and with other natural components of air to form new harmful chemicals, called secondary pollutants (Figure 12-4, right). With their high concentrations of cars and factories, urban areas normally have higher outdoor air pollution levels than rural areas have. But prevailing winds can spread long-lived primary and secondary air pollutants
Primary Pollutants CO SO2
Secondary Pollutants
CO2 NO
NO2
N2O SO3
CH4 and most other hydrocarbons HNO3
Most suspended particles
H2O2
H2SO4 O3
–
PANs
Most NO3 and SO4
2–
Natural Source
Stationary
salts
Human Source
Human Source Mobile
Figure 12-4 Human inputs of air pollutants come from mobile sources (such as cars) and stationary sources (such as industrial, power, and cement plants). Some primary air pollutants react with one another and with other chemicals in the air to form secondary air pollutants.
CONCEPT 12-2 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
247
Burning Coal Produces Industrial Smog Sixty years ago, cities such as London, England, and the U.S. cities of Chicago, Illinois, and Pittsburgh, Pennsylvania, were burning large amounts of coal in power plants and factories, and for heating homes. People in such cities, especially during winter, were exposed to industrial smog consisting mostly of an unhealthy mix of sulfur dioxide, suspended droplets of sulfuric acid, and a variety of suspended solid particles (Concept 12-2). Particles of carbon (soot) and other substances give the smog a gray color, which is why it is sometimes called gray-air smog. Today, urban industrial smog is rarely a problem in more-developed countries where coal and heavy oil are burned only in large power and industrial plants with reasonably good pollution control, or in facilities with tall smokestacks that send the pollutants high into air where prevailing winds carry them downwind to rural areas. However, industrial smog remains a problem in industrialized urban areas of China, India, Ukraine, and some other eastern European countries, where large quantities of coal are still burned in houses, power plants, and factories with inadequate pollution controls.
Sunlight Plus Cars Equals Photochemical Smog A photochemical reaction is any chemical reaction activated by light. Photochemical smog is a mixture of primary and secondary pollutants formed under the influence of UV radiation from the sun (Concept 12-2). In greatly simplified terms, ground level ozone (O3) + other photochemical VOCs + NOx + heat + sunlight
oxidants + aldehydes + other secondary pollutants
The formation of photochemical smog begins when exhaust from morning commuter traffic releases large amounts of NO and VOCs into the air over a city. The NO is converted to reddish-brown NO2, explaining why photochemical smog is sometimes called brown-air smog. When exposed to ultraviolet radiation from the sun, some of the NO2 reacts in complex ways with VOCs released by certain trees (such as some oak species, sweet gums, and poplars), motor vehicles, and businesses (such as bakeries and dry cleaners). The resulting mixture of chemicals usually builds up to peak levels by late morning, irritating people’s eyes and respiratory tracts.
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All modern cities have some photochemical smog, but it is much more common in cities with sunny, warm, and dry climates, and a great number of motor vehicles. Examples are Los Angeles, California, and Salt Lake City, Utah, in the United States; Sydney, Australia; São Paulo, Brazil; Bangkok, Thailand; Mexico City, Mexico. According to a 1999 study, if 400 million people in China were to drive conventional gasoline-powered cars by 2050, the resulting photochemical smog could regularly cover the entire western Pacific, extending to the United States.
Several Factors Can Decrease or Increase Outdoor Air Pollution Five natural factors help to reduce outdoor air pollution. First, particles heavier than air settle out as a result of gravitational attraction to the earth. Second, rain and snow partially cleanse the air of pollutants. Third, salty sea spray from the oceans washes out many pollutants from air that flows from land over the oceans. Fourth, winds sweep pollutants away and mix them with cleaner air. Fifth, some pollutants are removed by chemical reactions that combine chemicals to form secondary pollutants that fall to the ground. Six other factors can increase outdoor air pollution. First, urban buildings slow wind speed and reduce the dilution and removal of pollutants. Second, hills and mountains reduce the flow of air in the valleys below them and allow pollutant levels to build up at ground level. Third, high temperatures promote the chemical reactions leading to formation of photochemical smog. Fourth, emissions of volatile organic compounds (VOCs) from certain trees and plants in heavily wooded urban areas can play a large role in the formation of photochemical smog. A fifth factor—the so-called grasshopper effect—occurs when air pollutants are transported at high altitudes by evaporation and winds from tropical and temperate areas through the atmosphere to the earth’s polar areas. This happens mostly during winter and creates dense layers of reddish-brown haze over the Arctic. The sixth factor is temperature inversions— weather events in which a layer of warm air temporarily lies atop a layer of cooler air nearer the ground, preventing the natural rising and mixing of air from the ground to higher levels that normally disperses pollutants. If this condition persists, pollutants can build up to harmful and even lethal concentrations in the stagnant layer of cool air near the ground. Temperature inversions can be a problem in cities located in mountainous areas where the weather is cold and cloudy during part of the year. They can also occur in a city with a sunny climate, lots of motor vehicles, mountains on three sides, and an ocean on the fourth side.
Air Pollution, Climate Change, and Ozone Depletion
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12-3 What Is Acid Deposition and Why Is It a Problem? ▲
Acid deposition is mainly caused by emissions from coal-burning power plants and motor vehicles, and in some regions it threatens human health, aquatic life and ecosystems, forests, and man-made structures.
CONC EPT 12-3
Acid Deposition Is a Serious Regional Air Pollution Problem Most coal-burning power plants, ore smelters, and other industrial facilities in more-developed countries use tall smokestacks to vent the exhausts from burned fuel high into the atmosphere where wind can dilute and disperse them. These exhausts contain primary pollutants—sulfur dioxide, suspended particles, and nitrogen oxides—that are picked up by prevailing winds and can be transported as far as 1,000 kilometers (600 miles) downwind. During their trip, these compounds form secondary pollutants such as droplets of sulfuric acid, nitric acid vapor, and particles of acid-forming sulfate and nitrate salts. These acidic substances remain in the atmosphere for 2–14 days, depending mostly on prevailing winds, precipitation, and other weather patterns. During this period, they descend to the earth’s surface in two forms: wet deposition, consisting of acidic rain, snow, fog, and cloud vapor, and dry deposition, consisting of acidic particles. The resulting mixture is called acid deposition
(Figure 12-5)—sometimes called acid rain. Most dry deposition occurs within 2–3 days of emission, fairly near the industrial sources, whereas most wet deposition takes place within 4–14 days in more distant downwind areas. Acid deposition is a regional air pollution problem (Concept 12-3) in areas that lie downwind from coalburning facilities and from urban areas with large numbers of cars. Such areas include the eastern United States and other parts of the world (Figure 12-6, p. 250). In some areas, soils contain basic compounds, such as calcium carbonate (CaCO3), or limestone, which can react with and neutralize, or buffer, some inputs of acids. The areas most sensitive to acid deposition are those with thin, acidic soils that provide no such natural buffering (Figure 12-6, some darker shaded areas) and those where the buffering capacity of soils has been depleted by decades of acid deposition. Acid-producing chemicals generated in one country are often exported to other countries by prevailing winds. For example, acidic emissions from the United Kingdom and Germany blow into Switzerland, Austria,
Wind Transformation to sulfuric acid (H2SO4) and nitric acid (HNO3)
Windborne ammonia gas and some soil particles partially neutralize acids and form dry sulfate and nitrate salts
Wet acid depostion (droplets of H2SO4 and HNO3 dissolved in rain and snow)
Nitric oxide (NO) Sulfur dioxide (SO2) and NO
Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts)
Acid fog Lakes in deep soil high in limestone are buffered
Lakes in shallow soil low in limestone become acidic
Figure 12-5 Natural capital degradation: Acid deposition, which consists of acidic rain, snow, dust, or gas, is commonly called acid rain. Soils and lakes vary in their ability to neutralize excess acidity. Question: What are three ways in which your daily activities contribute to acid deposition?
CONCEPT 12-3 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Potential problem areas because of sensitive soils Potential problem areas because of air pollution: emissions leading to acid deposition Current problem areas (including lakes and rivers) Figure 12-6 This map shows regions where acid deposition is now a problem and regions with the potential to develop this problem. Such regions have large inputs of air pollution (mostly from power plants, industrial facilities, and ore smelters) or are sensitive areas with naturally acidic soils that cannot neutralize (buffer) additional inputs of acidic compounds. Question: Do you live in or near an area that is affected by acid deposition or an area that is likely to be affected by acid deposition in the future? (Data from World Resources Institute and U.S. Environmental Protection Agency)
Norway, and other neighboring countries, while emissions from coal-burning power and industrial plants in the United States end up in southeastern Canada. The worst acid deposition occurs in Asia, especially in China, which gets 70% of its total energy and 80% of its electricity from burning coal. According to its government, China is the world’s top emitter of SO2. The resulting acid precipitation is damaging crops and threatening food security in China, Japan, and North and South Korea.
Acid Deposition Has a Number of Harmful Effects Acid deposition causes harm in several ways. It contributes to human respiratory diseases, and damages buildings, statues, national monuments, metals, and car finishes. It can also leach toxic metals (such as lead and mercury) from soils and rocks into lakes used as sources of drinking water. Acidic particles in the air can also decrease visibility. Acid deposition harms aquatic ecosystems. Because of excess acidity, several thousand lakes in Norway and Sweden, and 1,200 in Ontario, Canada, contain few if any fish. In the United States, several hundred lakes (most in the Northeast) are similarly threatened.
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Acid deposition (often along with other air pollutants such as ozone) can harm crops. It reduces plant productivity and the ability of soils to buffer or neutralize acidic inputs. Likewise, it can also affect forests by leaching essential plant nutrients such as calcium and magnesium from soils. It also releases ions of aluminum, lead, cadmium, and mercury, which are toxic to trees. These two effects rarely kill the trees directly, but can weaken them and leave them vulnerable to stresses such as severe cold, diseases, insect attacks, and drought. Mountaintop forests are the terrestrial areas hardest hit by acid deposition. These areas tend to have thin soils without much buffering capacity. In addition, mountaintop trees (especially conifers such as red spruce and balsam fir) are bathed almost continuously in highly acidic fog and clouds. Acid deposition is not seriously destroying or harming most of the world’s forests and lakes. Rather, this regional problem is harming forests and lakes that lie downwind from coal-burning facilities and from large, motor vehicle–dominated cities without adequate pollution controls (Concept 12-3). Figure 12-7 summarizes ways to reduce acid GOOD deposition. According to most scientists studying NEWS the problem, the best solutions take a preventive approach that reduces or eliminates emissions of sulfur dioxide, nitrogen oxides, and particulates.
Air Pollution, Climate Change, and Ozone Depletion
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Figure 12-7 There are several ways to reduce acid deposition and its damage. Questions: Which two of these solutions do you think are the best ones? Why?
Solutions Acid Deposition P r eventi o n
Cleanup
Reduce coal use
Add lime to neutralize acidified lakes
Burn low-sulfur coal
Increase use of natural gas and renewable energy resources
Add phosphate fertilizer to neutralize acidified lakes
Remove SO2 particulates and NOx from smokestack gases and remove NOx from motor vehicular exhaust
Tax emissions of SO2
Controlling acid deposition is politically difficult. One problem is that the people and ecosystems it affects often are quite far downwind from the sources of the problem. Also, countries with large supplies of coal (such as China, India, Russia, and the United States) have a strong incentive to use it as a major energy resource. Owners of coal-burning power plants resist adding the latest pollution control equipment, using low-sulfur coal, or removing sulfur from coal before burning it, arguing that these measures would increase the cost of electricity for consumers. Environmental scientists counter that affordable and much cleaner resources are available to produce electricity, including wind, hydropower, and natural gas. They also point out that including the largely hidden harmful health and environmental costs of burning coal in its market prices would reduce coal use, spur the use of cleaner ways to generate electricity, and help prevent acid deposition.
12-4 What Are the Major
Indoor Air Pollution Problems? ▲
CONC EPT 12-4 The most threatening indoor air pollutants are smoke and soot from wood and coal fires (mostly in less-developed countries), cigarette smoke, and chemicals used in building materials and in many consumer products.
Indoor Air Pollution Is a Serious Problem If you are reading this book indoors, you may be inhaling more air pollutants than you would if you were outside. Figure 12-8 (p. 252) shows some typical sources of indoor air pollution in a modern home. EPA studies have revealed some alarming facts about indoor air pollution. First, levels of 11 common pollutants generally are 2 to 5 times higher inside U.S. homes and commercial buildings than they are outdoors, and in some cases they are as much as 100 times higher. Second, pollution levels inside cars in traffic-clogged urban areas can be up to 18 times higher than outside levels. Third, the health risks from exposure to such chemicals are magnified because most people in developed urban areas spend 70–98% of their time indoors or inside vehicles. Since 1990, the EPA has placed indoor air pollution at the top of the list of 18 sources of cancer risk. It
causes as many as 6,000 premature cancer deaths per year in the United States. At greatest risk are smokers, children younger than age 5, the elderly, the sick, pregnant women, people with respiratory or heart problems, and factory workers. Danish and U.S. EPA studies have linked various air pollutants found in buildings to a number of health effects, a phenomenon known as the sick-building syndrome. Such effects include dizziness, headaches, coughing, sneezing, shortness of breath, nausea, burning eyes, sore throats, chronic fatigue, irritability, skin dryness and irritation, respiratory infections, flu-like symptoms, and depression. EPA and Labor Department studies in the United States indicate that almost one in five commercial buildings in the United States exposes employees to these health risks. According to the EPA and public health officials, the four most dangerous indoor air pollutants in moredeveloped countries are tobacco smoke (see Chapter 11, Case Study, p. 238); formaldehyde emitted from many
CONCEPT 12-4 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Chloroform Source: Chlorine-treated water in hot showers Possible threat: Cancer
Para-dichlorobenzene Source: Air fresheners, mothball crystals Threat: Cancer
Tetrachloroethylene Source: Dry-cleaning fluid fumes on clothes Threat: Nerve disorders, damage to liver and kidneys, possible cancer
1,1,1-Trichloroethane Source: Aerosol sprays Threat: Dizziness, irregular breathing
Formaldehyde Source: Furniture stuffing, paneling, particleboard, foam insulation Threat: Irritation of eyes, throat, skin, and lungs; nausea; dizziness
Styrene Source: Carpets, plastic products Threat: Kidney and liver damage
Nitrogen oxides Source: Unvented gas stoves and kerosene heaters, woodstoves Threat: Irritated lungs, children's colds, headaches
Benzo- -pyrene Source: Tobacco smoke, woodstoves Threat: Lung cancer
Particulates Source: Pollen, pet dander, dust mites, cooking smoke particles Threat: Irritated lungs, asthma attacks, itchy eyes, runny nose, lung disease Tobacco smoke Source: Cigarettes Threat: Lung cancer, respiratory ailments, heart disease Asbestos Source: Pipe insulation, vinyl ceiling and floor tiles Threat: Lung disease, lung cancer
Carbon monoxide Source: Faulty furnaces, unvented gas stoves and kerosene heaters, woodstoves Threat: Headaches, drowsiness, irregular heartbeat, death
Radon-222 Source: Radioactive soil and rock surrounding foundation, water supply Threat: Lung cancer
Methylene chloride Source: Paint strippers and thinners Threat: Nerve disorders, diabetes
Figure 12-8 Numerous indoor air pollutants are found in most modern homes (Concept 12-4). Question: To which of these pollutants are you exposed? (Data from U.S. Environmental Protection Agency)
building materials and various household products; radioactive radon-222 gas (see the Case Study that follows); and very small (ultrafine) particles of various substances in emissions from motor vehicles, coal-burning and industrial power plants, the burning of wood, and forest and grass fires. The chemical that causes problems for most people in more-developed countries is formaldehyde, a colorless, extremely irritating chemical. According to the EPA and the American Lung Association, 20–40 million Americans suffer from chronic breathing problems, dizziness, rashes, headaches, sore throats, sinus and eye irritations, skin irritation, wheezing, and nausea caused by daily exposure to low levels of formaldehyde emitted from common household materials. These materials include building materials (such as plywood, particleboard, paneling, and high-gloss finishes on wood floors and cabinets), furniture, drapes, upholstery, adhesives in carpeting and wallpaper, ure-
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thane-formaldehyde foam insulation, fingernail hardener, and wrinkle-free coatings on permanent-press clothing. The EPA estimates that 1 of every 5,000 people who live in manufactured (mobile) homes for more than 10 years will develop cancer from formaldehyde exposure.
■ C AS E S T UDY
Radioactive Radon Gas Radon-222 is a colorless, odorless, radioactive gas that is produced by the natural radioactive decay of uranium238, small amounts of which are contained in most rocks and soils. But this isotope is much more concentrated in underground deposits of minerals such as uranium, phosphate, granite, and shale. When radon gas from such deposits seeps upward through the soil and is released outdoors, it disperses
Air Pollution, Climate Change, and Ozone Depletion
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quickly in the air and decays to harmless levels. However, in buildings above such deposits, radon gas can enter through cracks in a foundation’s slab and walls, openings around sump pumps and drains, and hollow concrete blocks. Once inside, it can build up to high levels, especially in unventilated lower levels of homes and buildings. Radon-222 gas quickly decays into solid particles of other radioactive elements such as polonium210, which if inhaled, will expose lung tissue to large amounts of ionizing radiation from alpha particles. This exposure can damage lung tissue and lead to lung cancer over the course of a 70-year lifetime. Your chances of getting lung cancer from radon depend mostly on how much radon is in your home, how much time you spend in your home, and whether you are a smoker or have ever smoked. About 90% of radon-related lung cancers occur among current or former smokers. According to the EPA, radioactive radon is the second leading cause of lung cancer and is responsible for 3% to 14% of lung cancer deaths in the United States. In 2010, the WHO estimated that radioactive radon gas in homes had killed an estimated 20,000 Americans in the previous year. Ideally, radon levels should be monitored continuously in the main living areas (not basements or crawl spaces) for 2 months to a year. But less than 20% of U.S. households have followed the EPA’s recommendation to conduct radon tests (most lasting only 2–7 days and costing $20–100 per home). For information about radon testing, visit the EPA website at http://www.epa.gov/radon/index.html. According to the EPA, radon control could add $350– 500 to the cost of a new home, and correcting a radon problem in an existing house could run $800–2,500. Remedies include sealing cracks in the foundation’s slab and walls, increasing ventilation by cracking a window or installing vents in the basement, and using a fan to create cross ventilation.
Prolonged or acute exposure to air pollutants, including tobacco smoke, can overload or break down these natural defenses. Fine and ultrafine particulates get lodged deep in the lungs, contributing to lung cancer, asthma, heart attack, and stroke. A French study found that asthma attacks increased by about 30% on smoggy days. Years of smoking or breathing polluted air can lead to other lung ailments such as chronic bronchitis and emphysema, which leads to acute shortness of breath and usually to death.
Air Pollution Is a Big Killer According to the WHO, at least 2.4 million people worldwide die prematurely each year—an average of nearly 274 deaths every hour—from the effects of air pollution. According to a 2007 World Bank study, most of these deaths occur in Asia, with about 750,000 deaths (500,000 from indoor air pollution) per year in China alone. The EPA estimates that in the United States, the annual number of deaths related to indoor and outdoor air pollution ranges from 150,000 to 350,000 people—equivalent to 2–5 fully loaded, 200-passenger airliners crashing every day with no survivors. Millions more suffer from asthma attacks and other respiratory disorders. Inhalation of very small particulates, mostly from coal-burning power plants, is responsible for as many as 70,000 premature deaths a year in the United States (Figure 12-9). A 2009 study by Canadian scientists, examining health data from 500,000 people living in soot-laden areas of 116 U.S. cities, found that inhalation of soot particles raised the chances of deadly heart attacks by 24% for this group.
Deaths per 100,000 adults per year <1
1–5
5–10 10–20 20–30 30+
Your Body’s Natural Defenses against Air Pollution Can Be Overwhelmed Your respiratory system has a number of ways that help protect you from air pollution. Hairs in your nose filter out large particles. Sticky mucus in the lining of your upper respiratory tract captures smaller (but not the smallest) particles and dissolves some gaseous pollutants. Sneezing and coughing expel contaminated air and mucus when pollutants irritate your respiratory system. In addition, hundreds of thousands of tiny, mucuscoated, hair-like structures, called cilia, line your upper respiratory tract. They continually move back and forth and transport mucus and the pollutants it traps to your throat where they are swallowed or expelled.
Figure 12-9 This map shows the distribution of premature deaths from air pollution in the United States, mostly from very small, fine, and ultra-fine particles added to the atmosphere by coal-burning power plants. Question: Why do the highest death rates occur in the eastern half of the United States? (Data from U.S. Environmental Protection Agency)
CONCEPT 12-4 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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12-5 How Should We Deal with Air Pollution? ▲
Legal, economic, and technological tools can help us to clean up air pollution, but the best solution is to prevent it.
C O NC EPT 12-5
Laws and Regulations Can Reduce Outdoor Air Pollution The United States provides an excellent example of how a regulatory approach can reduce air pollution (Concept 12-5). The U.S. Congress passed the Clean Air Acts in 1970, 1977, and 1990. With these laws, the federal government established air pollution regulations for key pollutants that are enforced by states and major cities. According to a 2009 EPA report, the combined GOOD emissions of the six key pollutants decreased by NEWS about 54% between 1980 and 2008, even with significant increases during the same period in gross domestic product, vehicle miles traveled, energy consumption, and population (see the Case Study that follows). According to the EPA, in 2008 about 57% of Americans lived in an area where the air was unhealthy to breathe during part of the year. This occurred mostly because concentrations of ground-level ozone and particulate matter exceeded the national air quality standards at various times. In 2008, the EPA warned that projected atmospheric warming during this century is likely to increase the rates of the chemical reactions that produce photochemical smog. Elsewhere in the world, especially in less-developed countries, pollution levels are much worse. But some countries, such as Taiwan, Singapore, Malaysia, South Korea, Thailand, and parts of China, are making some progress in improving outdoor urban air quality. While the U.S. regulatory model has been successful in reducing outdoor air pollution, environmental scientists point to areas where it still needs improvement (see the second Case Study that follows). ■ CAS E STUDY
Lead Can Be a Highly Toxic Pollutant Because it is a chemical element, lead (Pb) does not break down in the environment. This potent neurotoxin can harm the nervous system, especially in young children. Each year, 12,000–16,000 American children under age 9 are treated for acute lead poisoning, and about 200 die. About 30% of the survivors suffer from palsy, partial paralysis, blindness, and mental retardation. Children under age 6 and unborn fetuses even with only low blood levels of lead are especially vulnerable to nervous system impairment, lowered IQ (by an average of 7.4 points), shortened attention span, hyperactivity, hearing damage, and various behavior disorders.
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Between 1976 and 2006, the percentage of GOOD U.S. children ages 1 to 5 years with blood levels NEWS of lead above the safety standard dropped from 85% to about 1 %, which prevented at least 9 million childhood lead poisonings. The primary reason for this drop was that government regulations banned leaded gasoline in 1976 (with a complete phase-out by 1986) and greatly reduced the allowable levels of lead in paints in 1970 (even though illegal use continued until about 1978). This is an excellent example of the effectiveness of pollution prevention. But the U.S. Centers for Disease Control and Prevention estimates that at least 310,000 U.S. children still have unsafe blood levels of lead caused by exposure to a number of sources. Major sources are lead particles from peeling lead-based paint found in about 24 million houses built before 1960. Lead can also leach from water lines and pipes and faucets containing lead. Also, in 2007, major U.S. toy companies had to recall millions of toys made in China that contained lead paint. Other sources are older coal-burning power plants that have been able to delay meeting the emission standards of new plants, as well as lead smelters and waste incinerators. Health scientists have proposed a number of ways to help protect children from lead poisoning, as listed in Figure 12-10. Although the threat from lead has been greatly reduced in the United States, this is not the case in many developing countries. About 80% of the gasoline sold in the world today is unleaded, but about 100 countries still use leaded gasoline. The WHO estimates that 130 million to 200 million children around the world are at risk from lead poisoning, and 15 million to 18 million children in less-developed countries have permanent brain damage because of lead poisoning—mostly from the use of leaded gasoline. Some good news is that China recently phased out leaded gasoline in less than 3 years.
■ C AS E S T UDY
U.S. Air Pollution Laws Could Be Improved The reduction of outdoor air pollution in the GOOD United States since 1970 has been a remarkable NEWS success story, primarily because of two factors. First, U.S. citizens insisted that laws be passed and enforced to improve air quality. Second, the country was affluent enough to afford such controls and improvements.
Air Pollution, Climate Change, and Ozone Depletion
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using a typical gas-powered riding lawn mower for 1 hour creates as much air pollution as driving 34 cars for an hour.
Solutions Lead Poisoning P r e v e ntion
Co n t r ol
Phase out leaded gasoline worldwide
Replace lead pipes and plumbing fixtures containing lead solder
Phase out waste incineration
Remove leaded paint and lead dust from older houses and apartments
Ban use of lead solder Ban use of lead in computer and TV monitors Ban lead glazing for ceramicware used to serve food Ban candles with lead cores Test blood for lead by age 1
Sharply reduce lead emissions from incinerators Remove lead from TV sets and computer monitors before incineration or land disposal Test for lead in existing ceramicware used to serve food Test existing candles for lead Wash fresh fruits and vegetables
Figure 12-10 Ways to help protect children from lead poisoning are shown here. Questions: Which two of these solutions do you think are the most important? Why?
Environmental scientists applaud the success of U.S. air pollution control laws. But they call for strengthening the Clean Air Acts by: •
Putting much greater emphasis on preventing air pollution. The power of prevention is clear (Concept 12-6). In the United States, the air pollutant with the largest drop in its atmospheric level was lead, which was banned in gasoline and in most paints (see Case Study, p. 254).
•
Sharply reducing emissions from older coal-burning power and industrial plants, cement plants, oil refineries, and waste incinerators. Approximately 20,000 of such facilities in the United States have not been forced to meet the air pollution standards required for new facilities.
•
Improving fuel efficiency standards for motor vehicles to match or exceed those of European Union countries, Japan, and China (see Figure 10-3, right, p. 208).
•
More strictly regulating emissions from motorcycles and two-cycle gasoline engines. A 2005 Swiss study indicated that motorcycles collectively emit 16 times more hydrocarbons and three times more carbon monoxide than cars emit. The EPA estimates that
•
Setting much stricter air pollution regulations for airports and oceangoing ships in U.S. waters. Major U.S. airports are among the top polluters in their areas. According to the Earth Justice Legal Defense Fund, a single cargo ship emits more air pollution than 2,000 diesel trucks or 350,000 cars.
•
Sharply reducing indoor air pollution.
Executives of companies that would be affected by implementing stronger air pollution regulations claim that correcting these problems would cost too much and would hinder economic growth. Proponents of stronger regulations contend that history has shown that most industry cost estimates for implementing U.S. air pollution control standards have been much higher than the costs actually proved to be. In addition, implementing such standards has boosted economic growth and created jobs by stimulating companies to develop new pollution control technologies. HOW WOULD YOU VOTE?
✓ ■
Should the 1990 U.S. Clean Air Act be strengthened? Cast your vote online at www.cengage.com/login.
We Can Use the Marketplace to Reduce Outdoor Air Pollution One approach to reducing pollutant emissions has been to allow producers of air pollutants to buy and sell government air pollution allotments in the marketplace. This approach has had mixed results. With the goal of reducing SO2 emissions, the Clean Air Act of 1990 authorized an emissions trading, or capand-trade program, which enables the 110 most polluting coal-fired power plants in 21 states to buy and sell SO2 pollution rights. Each plant is annually given a number of pollution credits, which allow it to emit a certain amount of SO2. A utility that emits less than its allotted amount of SO2 has a surplus of pollution credits. That utility can use its credits to offset SO2 emissions at another of its plants, keep them for future plant expansions, or sell them to other utilities or private citizens or groups. Proponents of this approach say it is cheaper and more efficient than government regulation of air pollution. Critics of this approach contend that it allows utilities with older, dirtier power plants to buy their way out of their environmental responsibilities and continue to pollute. In addition, without strict government oversight, this approach makes cheating possible, because cap-and-trade is based largely on self-reporting of emissions. The ultimate success of any emissions trading approach depends on two factors: how low the initial
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cap is set and how often it is lowered in order to promote continuing innovation in air pollution prevention and control. Without these two elements, emissions trading programs mostly shift pollution problems from one area to another without achieving any overall improvement in air quality. Between 1990 and 2006, the emissions trad- GOOD ing system helped to reduce SO2 emissions from NEWS power plants in the United States by 53%, at a cost of less than one-tenth what was projected by the industry. An emissions trading system is also being used for NOx. However, environmental and health scientists strongly oppose a cap-and-trade program for controlling emissions of toxic mercury (Hg) by coal-burning power plants and industries. They warn that coal-burning plants that choose to buy permits instead of sharply reducing their mercury emissions will create toxic hotspots with unacceptably high levels of mercury. HOW WOULD YOU VOTE?
✓ ■
Should we use emissions trading to help control emissions of all major air pollutants? Cast your vote online at www .cengage.com/login.
There Are Many Ways to Reduce Outdoor Air Pollution Figure 12-11 summarizes ways to reduce emissions of sulfur oxides, nitrogen oxides, and particulate matter from stationary sources such as coal-burning power plants and industrial facilities.
Solutions Stationary Source Air Pollution P r eventi o n
R ed uc t i on or Disp os al
Burn low-sulfur coal or remove sulfur from coal
Disperse emissions (which can increase downwind pollution) with tall smokestacks
Convert coal to a liquid or gaseous fuel
Phase out coal use
Remove pollutants from smokestack gases
Tax each unit of pollution produced
Figure 12-11 There are several ways to prevent, reduce, or disperse emissions of sulfur oxides, nitrogen oxides, and particulate matter from stationary sources such as coal-burning power plants and industrial facilities (Concept 12-5). Questions: Which two of these solutions do you think are the best ones? Why?
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Solutions Motor Vehicle Air Pollution P r event i on
C le a nup
Walk, bike, or use mass transit
Require emission control devices
Inspect car exhaust systems twice a year
Improve fuel efficiency
Get older, polluting cars off the road
Set strict emission standards
Figure 12-12 There are a number of ways to prevent and reduce emissions from motor vehicles (Concept 12-5). To find out what and how much your car emits, go to www.cleancarsforkids.org. Questions: Which two of these solutions do you think are the best ones? Why?
HOW WOULD YOU VOTE?
✓ ■
Should older coal-burning power and industrial plants have to meet the same air pollution standards that new facilities must meet? Cast your vote online at www.cengage.com/login.
Figure 12-12 lists ways to prevent and reduce emissions from motor vehicles, the primary factor in the formation of photochemical smog. Unfortunately, the already poor air quality in urban areas of many less-developed countries is worsening as the numbers of motor vehicles in these countries rises. Many of these vehicles are 10 or more years old, have no pollution control devices, and burn leaded gasoline. However, because of the Clean Air Acts, a new car today in the United States emits 75% less pollution than did a pre-1970 car. Over the next 10–20 years, technology will bring more gains through improved GOOD engines and emission systems, and new energy- NEWS efficient cars.
Reducing Indoor Air Pollution Should Be a Priority Little effort has been devoted to reducing indoor air pollution even though it poses a much greater threat to human health than does outdoor air pollution. Air pollution experts suggest several ways to prevent or reduce indoor air pollution, as shown in Figure 12-13. In less-developed countries, indoor air pollution from open fires and leaky, inefficient cooking stoves that burn wood, charcoal, or coal could be reduced. More
Air Pollution, Climate Change, and Ozone Depletion
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Solutions
What Can You Do?
Indoor Air Pollution
Indoor Air Pollution
Prev e n t io n
Cleanup or D ilu tion
■
Test for radon and formaldehyde inside your home and take corrective measures as needed
Ban indoor smoking
Use adjustable fresh air vents for work spaces
■
Do not buy furniture and other products containing formaldehyde
■
Remove your shoes before entering your house to reduce inputs of dust, lead, and pesticides
■
Switch to phthalate-free detergents
■
Test your house or workplace for asbestos fiber levels, and check for any crumbling asbestos materials if it was built before 1980
■
Do not store gasoline, solvents, or other volatile hazardous chemicals inside a home or attached garage
■
If you smoke, do it outside or in a closed room vented to the outside
■
Make sure that wood-burning stoves, fireplaces, and kerosene and gas-burning heaters are properly installed, vented, and maintained
■
Install carbon monoxide detectors in all sleeping areas
Set stricter formaldehyde emissions standards for carpet, furniture, and building materials
Prevent radon infiltration
Use less polluting cleaning agents, paints, and other products
Circulate air more frequently
Circulate a building’s air through rooftop greenhouses
Use efficient venting systems for wood-burning stoves
Figure 12-14 Individuals matter: You can reduce your exposure to indoor air pollution. Questions: Which three of these actions do you think are the most important? Why?
Figure 12-13 There are several ways to prevent and reduce indoor air pollution (Concept 12-5). Questions: Which two of these solutions do you think are the most important? Why?
people could use inexpensive clay or metal stoves that burn biofuels more efficiently and vent their exhausts to the outside, or they could use stoves that use solar energy to cook food. Figure 12-14 lists some ways in which you can reduce your exposure to indoor air pollution.
We Need to Put More Emphasis on Pollution Prevention Since 1970, most of the world’s more-developed countries have enacted laws and regulations that have significantly reduced outdoor air pollution. Most of these laws emphasize controlling outdoor air pollution by using output approaches. Environmental and health scientists argue that the next step is to shift our emphasis to preventing air pollution (Concept 12-5). With this approach, the question is not What can we do about the air pollutants we produce? but rather How can we avoid producing these pollutants in the first place? Figure 12-15 shows ways to prevent outdoor and indoor air pollution over the next 30–40 years. Like the shift to controlling outdoor air pollution between 1970 and 2010, this new shift to preventing outdoor and indoor air pollution will not take place unless individual citizens and groups put political pressure on elected officials and economic pressure on companies.
Solutions Air Pollution O ut d oor
I nd oor
Improve energy efficiency to reduce fossil fuel use
Reduce poverty
Rely more on lower-polluting natural gas Rely more on renewable energy (especially solar cells, wind, geothermal and solar-produced hydrogen) Transfer energy efficiency, renewable energy, and pollution prevention technologies to developing countries
Distribute cheap and efficient cookstoves or solar cookers to poor families in developing countries
Reduce or ban indoor smoking
Develop simple and cheap tests for indoor pollutants such as particulates, radon, and formaldehyde
Figure 12-15 Ways to prevent outdoor and indoor air pollution over the next 30–40 years (Concept 12-5) are shown here. Questions: Which two of these solutions do you think are the best ones? Why?
CONCEPT 12-5 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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12-6 In the Future, How Might the Earth’s Temperature
and Climate Change, and with What Effects? ▲
C O NC EPT 12-6A
▲
C O NC EPT 12-6B The projected rapid change in the atmosphere’s temperature could have severe and long-lasting consequences, including increased drought and flooding, rising sea levels, and shifts in the locations of croplands and wildlife habitats.
Evidence indicates that the earth’s atmosphere is warming because of a combination of natural effects and human activities, and that this warming is likely to lead to significant climate change during this century.
AVERAGE TEMPERATURE (over past 900,000 years) 17 16 15 14 13 12 11 10 9 900 800 700 600 500 400 300 200 100 Present
2 1 0 -1 -2 -3 -4 -5
AVERAGE TEMPERATURE (over past 130 years) 15.0 14.8 14.6 14.4 14.2 14.0 13.8 13.6 1880 1900 1920 1940 1960 1980 2000 2020
Thousands of years ago
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TEMPERATURE CHANGE (over past 22,000 years)
TEMPERATURE CHANGE (over past 1,000 years) Temperature change (°C)
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Average surface temperature (°C)
Climate change is neither new nor unusual. Over the past 3 billion or more years, the planet’s climate has been altered by the sun’s output of energy, volcanic eruptions and impacts by large meteorites that throw immense amounts of ash and dust into the atmosphere, and slight changes in the earth’s orbit around the sun. Over the past 900,000 years, the atmosphere has experienced prolonged periods of global cooling and global warming (Figure 12-16, top left). These alternating cycles of freezing and thawing are known as glacial and interglacial (between ice ages) periods.
For roughly 10,000 years, we have had the good fortune to live in an interglacial period characterized by a fairly stable climate based mostly on a generally steady global average surface temperature (Figure 12-16, bottom left). These conditions allowed the human population to grow as agriculture developed, and later as cities grew. For the past 1,000 years, the average temperature of the atmosphere has remained fairly stable but began to rise during the last century (Figure 12-16, bottom right) when people began clearing more forests and burning more fossil fuels. The top right graph in Figure 12-16 shows that most of the recent increase in temperature has taken place since 1975 (Concept 12-6A). Average surface temperature (°C)
Climate Change Is Not New
Agriculture established
End of last ice age
Average temperature over past 10,000 years = 15°C (59°F)
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Figure 12-16 Science: The global average temperature of the atmosphere near the earth’s surface has changed significantly over different periods of time. The two graphs in the top half of this figure are rough estimates of longand short-term global average temperatures, and the two graphs on the bottom are estimates of changes in the average temperature of the earth’s lower atmosphere over thousands (left) or hundreds (right) of years. They are based on scientific evidence that contains gaps, but they do indicate general trends. Question: Assuming these are good estimates, what are two conclusions you can draw from these graphs? (Data from NASA Goddard Institute for Space Studies, Intergovernmental Panel on Climate Change, National Academy of Sciences, National Aeronautics and Space Administration, National Center for Atmospheric Research, and National Oceanic and Atmospheric Administration)
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Air Pollution, Climate Change, and Ozone Depletion
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Human Activities Emit Large Quantities of Greenhouse Gases
Measurements of CO2 and CH4 in bubbles at various depths in ancient glacial ice indicate that changes in the levels of these gases correlate fairly closely with changes in the global average temperature near the earth’s surface during the past 400,000 years, and with changes in the average global sea level (Figure 12-17). The burning of fossil fuels tops the list of human activities that emit CO2. Not all fossil fuels emit the same amount of CO2 per unit of energy generated, however.
CO2 concentration (ppm)
Since the beginning of the Industrial Revolution in the mid-1700s, human actions—mainly burning fossil fuels in industry and for transportation, burning coal to generate electricity, deforestation, and agriculture, in that order—have led to significant increases in the greenhouse gases CO2 and CH4 in the lower atmosphere.
400 380 360 340 320 300 280 260 240 220 200 180
160
Temperature change (°C)
CH4 concentration (ppb)
400,000
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CO2
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20 0 –20 –40 –60 –80 –100 –120 400,000
200,000 Year before present
200,000 Year before present Sea level
350,000
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Figure 12-17 Science: Atmospheric levels of carbon dioxide (CO2) and methane (CH4), as well as the global average temperature of the atmosphere near the earth’s surface and the average global sea level have changed drastically over the past 400,000 years. These data were obtained by analysis of ice cores removed at Russia’s Vostok Research Station in Antarctica. More recent ice core analyses from Antarctica in 2007 indicate that current levels of CO2 in the atmosphere are higher than at any time during the past 800,000 years. Question: What are two conclusions that you can draw from these data? (Data from Intergovernmental Panel on Climate Change, National Center for Atmospheric Research, and F. Vimeux et al., Earth and Planetary Science Letters, vol. 203 (2002): 829–843)
CONCEPTS 12-6A AND 12-6B Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Average surface temperature (°C)
15.0
400 Average annual temperature Running mean CO2
14.8 14.6
380 360
14.4 14.2
340
14.0
320
13.8 300
13.6 13.4
Atmospheric CO2 concentration (ppm)
Coal is by far the highest emitter. When natural gas is burned, it emits just over half of the amount of CO2 per unit of energy that coal emits. Carbon dioxide levels in the atmosphere are still increasing rapidly, according to scientists from many organizations, including the U.S. National Oceanographic and Atmospheric Administration (NOAA). The average atmospheric concentration of carbon dioxide rose from a level of 280 parts per million at the start of the Industrial Revolution to 389 parts per million in 2010. Figure 12-18 shows changes in atmospheric CO2 concentrations and the average temperature of the atmosphere between 1880 and 2009.
280
1880 1900 1920 1940 1960 1980 2000 2020
Human Activities Play a Role in Recent Atmospheric Warming Working through the World Meteorological Organization, several nations established the Intergovernmental Panel on Climate Change (IPCC) in 1988 to document past climate changes and project future changes. The IPCC network includes more than 2,500 climate scientists and scientists in disciplines related to climate studies from more than 130 countries. Its 2007 report was based on more than 29,000 sets of data, many of them collected since 2002. In this report, the IPCC listed a number of findings indicating that it is very likely that
Year Figure 12-18 This graph compares atmospheric concentrations of carbon dioxide (CO2) and the atmosphere’s average temperature for the period 1880–2009. The temperature data show the average temperature by year as well as a mean of these data. While the data show an apparent correlation between these two variables, they do not firmly establish such a correlation. (Data from Intergovernmental Panel on Climate Change, NASA Goddard Institute for Space Studies, and NOAA Earth System Research Laboratory)
the lower atmosphere is getting warmer (Concept 12-6A) and that human activities have played a role in temperature increases since 1950 (see Science Focus below). Here are a few of the many pieces of evidence that the IPCC used to help support the major conclusions in
SCIE N C E FO C US How Valid Are IPCC Conclusions?
S
cientists are professional skeptics who are always saying “show me your evidence and explain your reasoning,” while vigorously arguing with one another over almost everything, with the goal of reaching general agreement and moving on to another scientific problem. They often question scientific data, the statistical methods used to evaluate the data, and the conclusions drawn from the data. Throughout the history of science, skeptical scientists have played a key role in encouraging other scientists to improve their measurements and models, and to take a closer look at their assumptions and hypotheses. Thus, it is natural and healthy that there are skeptics who doubt the validity of various hypotheses and models having to do with climate change. For over two decades, more than 2,500 of the world’s top scientists in a variety of disciplines related to climate studies have been examining all of the evidence they could find about climate and climate change.
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They have poured over tens of thousands of peer-reviewed studies and looked into the validity of a variety of climate models. During this long period, they have also been debating what valid conclusions they can draw from such evidence. This unprecedented effort to evaluate climate data has been one of the longest and most thorough studies in the history of science. The goals of this continuing effort have been to see if these top scientists can reach a general agreement, or consensus, about the usefulness of the data and conclusions that they have evaluated, and to report their findings to the world. In climate science, there are still many gaps in the data and much debate about interpretations of the data. There is also a need for significant improvement in our understanding of the complex mix of variables in the earth’s climate system and in the climate models that attempt to mimic how these variables interact.
But despite many uncertainties, after three decades of research and debate, there is general agreement among most of the earth’s climate scientists that the earth’s climate has warmed by about 0.6 Co (1 Fo) since 1980 and that human activities played a role in this warming (although the degree of human influence is still being debated). Scientists in any field rarely reach a general agreement on anything because of their habitual skepticism and the nature of the scientific process (see Chapter 2, pp. 22–23). Thus, this degree of consensus found among the world’s top climate experts on the subject of climate change is extremely rare. Critical Thinking Some critics argue that the hypothesis that the earth’s atmosphere has warmed and that humans have played a role in this warming is a scientific hoax. Explain why you agree or disagree with this argument based on the material in this Science Focus.
Air Pollution, Climate Change, and Ozone Depletion
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its 2007 report, plus additional scientific data collected after that report was made: •
Between 1906 and 2005, the average global surface temperature has risen by about 0.74 C° (1.3 F°). Most of this increase has taken place since 1980 (Figure 12-16, top right, and Figure 12-18).
•
Annual greenhouse gas emissions from human activities rose 70% between 1970 and 2009, and average CO2 concentrations are higher than they have been in 650,000 or more years.
•
The first decade in this century (2000–2009) was the warmest decade since 1881 (Figure 12-16, top right, and Figure 12-18).
•
In some parts of the world, glaciers are melting and floating sea ice is shrinking, both at increasing rates.
•
During the 20th century, the world’s average sea level rose by 19 centimeters (7 inches), mostly because of runoff from melting landbased ice and the expansion of ocean water as its temperature increased. By comparison, sea levels rose 2 centimeters (3/4 of an inch) in the 18th century and 6 centimeters (2 inches) in the 19th century.
More recent data about the melting of arctic sea ice and ice sheets in Greenland have alarmed some climate scientists who now contend that the 2007 IPCC report underestimated the likely effects of climate change. Sea level rises during this century, for example, are projected to be 2–3 times what the IPCC projected in 2007. This is because of new measurements showing that ice sheets in Greenland are melting much faster than the IPCC realized in 2007.
Also, a 2009 study led by U.S. National Aeronautics and Space Administration (NASA) scientist Ron Kwok found that arctic sea ice is also growing thinner, having lost 40% of its thickness since 2004. Kwok noted that the thinner the sea ice is, the faster it will tend to melt. A number of scientific studies and major climate models indicate that we need to prevent CO2 levels from exceeding a certain threshold, or irreversible tipping point, that could set into motion large-scale climate changes for hundreds to thousands of years. According to NASA climate scientist James Hansen (Individuals Matter, below), we need to bring CO2 levels down below where they are now in order to maintain an environment similar to that in which our civilizations developed over the last 10,000 years. HOW WOULD YOU VOTE?
✓ ■
Do you think that we will experience significant atmospheric warming and climate change during this century? Cast your vote online at www.cengage.com/login.
What Role Do Oceans Play in Climate Change? The world’s oceans absorb CO2 from the atmosphere as part of the carbon cycle and thus help to moderate the earth’s average surface temperature and its climate. It is estimated that the oceans remove about 25–30% of the CO2 pumped into the lower atmosphere by human activities. In 2009, the world’s oceans were the warmest in 130 years of record keeping. The ability of the oceans to absorb CO2 also decreases when water temperatures
I ND I VI D UALS M ATTE R Sounding the Alarm—James Hansen
I
n 1988, American climate scientist James Hansen appeared before a U.S. Congressional committee and stated he was 99% certain that atmospheric warming was a grave threat made worse every day by large and growing emissions of carbon dioxide and other greenhouse gases resulting from human activities. With that, he kicked off the public debate over what most climate scientists believe is our greatest environmental challenge. Hansen has used his decades of experience as a climate scientist and head of NASA’s Goddard Institute for Space Studies to help develop several climate models for the earth. He is well respected by his peers and is also known for his willingness to speak out despite scientific and public skepticism about
climate change. This is unusual because most scientists prefer to stay out of the political arena where the rules of evidence and debate are quite different and much more lax than they are in the scientific arena. Hansen’s message is that, based on what he has learned by studying climate and climate change for many decades, rising levels of greenhouse gases will likely lead to catastrophic climate change during this century unless those levels are drastically reduced. He has stated repeatedly that what motivates him is his concern for future generations. “The difficulty of this problem,” Hansen said, “is that its main impacts will be felt by our children and by our grandchildren.” In 2006, he received the American Association for the Advancement of Science Award
for Scientific Freedom and Responsibility. He was also listed by Time magazine as one of the world’s 100 most influential people in 2006. In 2009, Hansen received the American Meteorological Society’s highest award for his “outstanding contributions to climate modeling, understanding climate change, and for clear communication of climate science in the public arena.” In addition to sounding the alarm, Hansen uses his knowledge and experience to inspire some hope about the future. For example, using the climate models that he helped to develop, he evaluates and makes projections about the effectiveness of various possible solutions to the problem of projected climate disruption.
CONCEPTS 12-6A AND 12-6B Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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increase. As the oceans warm up, some of their dissolved CO2 is released into the lower atmosphere, like CO2 bubbling out of a warm carbonated soft drink. According to scientific measurements from a 2007 study, the upper portion of the oceans warmed by an average of 0.32–0.67Co (0.6–1.2Fo) during the last century—an astounding increase considering the huge volume of water involved. Much of the CO2 absorbed by the ocean reacts with water to produce carbonic acid (H2CO3)—the same weak acid found in carbonated drinks. In 2005, the United Kingdom’s Royal Society reported that higher levels of CO2 in the ocean have increased the acidity of its surface by 30% from preindustrial times, and the report warned that ocean acidity could reach dangerous levels before 2050. The increased acidity threatens corals and other organisms with shells and body structures composed of calcium carbonate, which dissolves when acidity reaches a certain level. It also further reduces the ability of the oceans to absorb CO2, which could lead to accelerating climate disruption.
There Is Uncertainty about the Effects of Cloud Cover on Atmospheric Warming The role played by clouds in the warming of the atmosphere is a major unknown in global climate models and a key reason why there is such a wide range of projected future temperatures. Warmer temperatures increase evaporation of surface water and create more clouds, which can cool or warm the atmosphere. An increase in thick and continuous cumulus clouds at low altitudes could decrease surface warming by reflecting more sunlight back into space. But an increase in thin, wispy cirrus clouds at high altitudes could increase the warming of the lower atmosphere by preventing more heat from escaping into space. In fact, satellite images indicate that wispy condensation trails (contrails) left behind by jet planes expand and turn into large cirrus clouds, which tend to heat the atmosphere. If these preliminary results are confirmed, we may find that emissions from jet planes are responsible for as much as half of the warming of the lower atmosphere in the northern hemisphere where much of the world’s air travel is concentrated. Climate modelers have not been able to show which of these effects is the most important and are working hard to understand more about the role of clouds in their climate models.
Outdoor Air Pollution Can Temporarily Slow Climate Change There is some evidence that aerosols (suspended microscopic droplets and solid particles) in the atmosphere have slowed the rate of atmospheric warming. Aero-
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sols of various air pollutants are released or formed in the troposphere by volcanic eruptions and human activities. Most aerosols, such as light-colored sulfate particles produced by fossil fuel combustion, tend to reflect incoming sunlight and cool the lower atmosphere. Sulfate particles also serve as condensation nuclei that form cooling clouds. But tiny particles of soot or black carbon aerosols, produced mainly from incomplete combustion in coal burning, diesel engines, and open fires, may contribute to warming. A 2008 study by atmospheric scientist V. Ramanathan and his colleagues found that soot has a warming effect on the atmosphere four times greater than was estimated earlier. Climate scientists do not expect aerosols and soot pollutants to counteract or enhance projected climate change very much in the next 50 years for two reasons. First, aerosols and soot fall back to the earth or are washed out of the lower atmosphere within weeks or months, whereas CO2 remains in the lower atmosphere for 80–120 years. Second, aerosol and soot inputs into the lower atmosphere are being reduced—especially in more-developed countries—because of their harmful impacts.
Projected Climate Disruption Could Have Severe Consequences Climate scientists are concerned not only about how much the temperature might change, but also about how rapidly the change will occur. Most historic changes in the temperature of the lower atmosphere took place over thousands of years (Figure 12-16, top left and bottom left). What makes the current problem urgent is that we face a rapid projected increase in the average temperature of the lower atmosphere during this century. Climate models indicate that such changes will determine where we can grow food and how much of it we can grow; which areas will suffer from increased drought and which will experience increased flooding; and in what areas people and many forms of wildlife can live. If the models are correct, we will have to deal with these effects within this century—an incredibly short time span in terms of the earth’s overall climate history. A 2003 U.S. National Academy of Sciences report laid out a nightmarish worst-case scenario in which human activities, alone or in combination with natural factors, trigger new and abrupt climate and ecological changes. At that point, the global climate system would reach an irreversible tipping point after which it would be too late to reverse catastrophic changes for tens of thousands of years. The report describes ecosystems suddenly collapsing, flooding of low-lying coastal cities, forests consumed in vast wildfires, and grasslands, dried out from prolonged drought, turning into dust bowls. It warns of rivers drying up—and with them, drinking water and irriga-
Air Pollution, Climate Change, and Ozone Depletion
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tion water supplies—as the mountain glaciers that feed them melt and disappear. It also describes premature extinction of up to half of the world’s species, prolonged heat waves and droughts, more destructive storms, and tropical infectious diseases spreading beyond their current ranges. These possibilities were supported by a 2003 analysis carried out for the U.S. Department of Defense by Peter Schwartz and Doug Randall. They concluded that projected climate disruption “must be viewed as a serious threat to global stability and should be elevated to a U.S. national security concern.” Let us look more closely at some of the current signs, and projected effects, of climate change. Drought: Recall that drought occurs when evaporation resulting from higher temperatures greatly exceeds precipitation for a prolonged period. According to a 2005 study by NASA climate scientist Aiguo Dai and his colleagues, severe and prolonged drought now affects at least 30% of the earth’s land (excluding Antarctica). As drought increases, there will be less moisture in the soil, stream flows and available surface water will decline, and net primary productivity will fall. Tree growth will slow, which will reduce CO2 removal from the atmosphere, and forest and grassland fires will increase, which will add CO2 to the atmosphere. Some lakes and seas will shrink or disappear and 1–3 billion people will face severe shortages of water. Areas of dry climate biomes such as savannas, prairies, and deserts will expand. Melting ice and snow: Climate models project that atmospheric warming will be the most severe in the world’s polar regions. Ice and snow in these regions help to cool the earth by reflecting incoming solar energy. The melting of such ice and snow exposes much darker land and sea areas that reflect much less sunlight and absorb more solar energy. This is causing polar regions to warm faster than lower latitudes and to accelerate atmospheric warming by reflecting less of the solar energy reaching the earth’s surface. The world is losing its vast polar ice sheets faster than scientists thought possible only a few years ago. Sea ice plays an important role in the earth’s climate. Loss of arctic sea ice could reduce rainfall and snowfall in the already arid American West and affect food production there by reducing the availability of irrigation water. This loss of sea ice could also increase precipitation and flooding in western and southern Europe. Mountain glaciers are affected by two climatic factors: average snowfall, which adds to their mass during the winter, and average warm temperatures, which spur their melting during the summer. During the past 25 years, many of the world’s mountain glaciers have been slowly melting and shrinking. For example, climate models predict that by 2070, Glacier National Park in the U.S. state of Montana will have no glaciers for the first time in at least 7,000 years. The U.S. Geological
Survey reported in 2009 that 99% of Alaska’s glaciers are also shrinking. In 2009, Swiss scientists reported that Himalayan glaciers as well as glaciers in Europe’s Alps shrank farther and faster in the last decade than they had in 150 years. About 80% of the mountain glaciers in South America’s Andes range are also slowly shrinking. If this continues, sometime during the next one or two centuries, millions of people in countries such as Bolivia, Peru, and Ecuador who rely on meltwater from the glaciers could face severe shortages. Melting permafrost: Climate change could be accelerated by the release of methane from melting permafrost, the frozen water in soils and lakebeds of the polar regions. The amount of carbon locked up as methane (CH4) in permafrost soils is 50–60 times the amount emitted as carbon dioxide from burning fossil fuels each year. According to the 2004 Arctic Climate Impact Assessment, 10–20% of the Arctic’s current permafrost might thaw during this century. The resulting increase in CH4 and CO2 emissions would cause more warming, which would in turn melt more permafrost. Rising sea levels: Sea levels are rising faster than IPCC scientists had reported in 2007, according to newer studies. A 2008 U.S. Geological Survey report concluded that the world’s average sea level will most likely rise 0.8–2 meters (3–6.5 feet) by the end of this century— 3 to 5 times the increase estimated in the 2007 IPCC report—and will probably keep rising for centuries. This rise is due to the expansion of seawater as it warms, and to the melting of land-based ice. Such a rise in sea level would be more dramatic if the vast land-based glaciers in Greenland and western Antarctica, as well as many of the world’s mountaintop glaciers, continue melting at their current, or higher, rates as the atmosphere warms. A 2009 study by British climate scientist Jonathan Bamber estimated that a loss of just 15% of Greenland’s ice sheet would cause a 1-meter (3.3-foot) rise in sea level. According to the IPCC, this projected rise in sea levels during this century (excluding the additional effects of storm surges) could cause the following serious effects: •
Degradation or destruction of at least one-third of the world’s coastal estuaries, wetlands, and coral reefs.
•
Disruption of many of the world’s coastal fisheries.
•
Flooding and erosion of low-lying barrier islands and gently sloping coastlines, especially in the U.S. coastal states of Texas, Louisiana, Florida, North Carolina, and South Carolina.
•
Flooding of agricultural lowlands and deltas in coastal areas where much of the world’s rice is grown.
•
Saltwater contamination of freshwater coastal aquifers and decreased supplies of groundwater. CONCEPTS 12-6A AND 12-6B
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•
Submersion of low-lying islands in the Indian Ocean, the Pacific Ocean, and the Caribbean Sea, which are home to 1 of every 20 of the world’s people.
•
Flooding of some of the world’s largest coastal cities, including Calcutta (India), Mumbai (India), Dhaka (Bangladesh), Guangzhou (China), Ho Chi Minh City (Vietnam), Shanghai (China), Bangkok (Thailand), Rangoon (Myanmar), Haiphong (Vietnam), New York, New York (USA) and Miami, Florida (USA), and displacement of at least 100 million people.
Extreme weather events: According to the IPCC, atmospheric warming will increase the incidence of extreme weather such as severe droughts and heat waves in some areas, which could kill large numbers of people, reduce crop production, and expand deserts. At the same time, because a warmer atmosphere can hold more moisture, other areas will experience increased flooding from heavy and prolonged precipitation. There is controversy among scientists over whether climate change will increase the frequency and intensity of tropical storms and hurricanes. In 2008, climatologists Mark Saunders and Adam Lea analyzed data collected since 1950 and found that for every increase of about 0.8C° (1F°) in the water temperature of the Atlantic Ocean, the overall number of hurricanes and tropical storms increased by about a third, and the number of intense hurricanes increased by 45%. However, some researchers blame the ups and downs in the intensity of tropical Atlantic hurricanes on natural climate cycles that can change ocean circulation patterns. In 2010, a World Meteorological Organization panel of experts on hurricanes and climate change from both sides of this scientific debate reached the following consensus view: projected atmospheric warming is likely to lead to fewer but stronger hurricanes, overall. While there will be fewer weak and moderate tropical storms and hurricanes, there are likely to be larger ones that cause more damage. Threats to biodiversity: According to the 2007 IPCC report, projected climate change is likely to disrupt ecosystems and decrease biodiversity in areas of every continent. Approximately 30% of the land-based plant and animal species assessed so far could disappear if the average global temperature change exceeds 1.5–2.5oC (2.7–4.5oF). This percentage could grow to 70% if the temperature change exceeds 3.5oC (6.3oF). The hardest hit species will be plants and animals in colder climates such as the polar bear in the Arctic and penguins in Antarctica; species that live at higher elevations; plant and animal species with limited ranges such as some amphibians; and those with limited tolerance for temperature change. Coral reefs are the ecosystems most likely to suffer disruption and species loss from climate change, mostly due coral bleaching. Other ecosystems especially vul-
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nerable to climate change are polar seas, coastal wetlands, high-elevation mountaintops, and alpine and arctic tundra. Some types of forests that are unable to migrate fast enough to keep up with climate change will decline, while others may expand northward. Because of drier conditions, forest fires could become more frequent in some areas such as the southeastern and western United States. This would severely degrade some forest ecosystems, add more CO2 to the atmosphere, reduce total CO2 uptake by trees and plants, and help to accelerate climate change. A warmer climate can also greatly increase populations of insects and fungi that damage trees. In the Canadian province of British Columbia, for example, warmer winters have already led to surges in mountain pine beetle populations that have infected huge areas of lodgepole pine forests, which are now dying. Pine beetles have also damaged about 60% of the lodgepole pines in the U.S. state of Colorado. Disruptions in agriculture: According to the 2007 IPCC report, crop productivity is projected to increase slightly at middle to high latitudes with moderate warming, but to decrease if warming goes too far. For example, moderately warmer temperatures and increased precipitation in parts of mid-western Canada, as well as in Russia and Ukraine, could lead to higher productivity there. But this effect may be limited because soils generally are more lacking in plant nutrients in these northern regions. Models project a decline in agricultural productivity in tropical and subtropical regions, especially in Southeast Asia and Central America, where many of the world’s poorest people live. Threats to human health: According to the IPCC and other reports, more frequent and prolonged heat waves in some areas will increase numbers of deaths and illnesses, especially among older people, people in poor health, and the urban poor. On the other hand, in a warmer world, fewer people will die from cold weather. A warmer, CO2-rich world will be a great place for rapidly multiplying insects, microbes, toxic molds, and fungi that make us sick, and for plants that produce pollens that cause allergies and asthma attacks. Organisms causing tropical infectious diseases such as dengue fever (Figure 12-19), yellow fever, and malaria are likely to expand their ranges, along with the mosquitoes that carry them, to temperate and higher-elevation areas that are getting warmer. Increasing illness, hunger, flooding, and drought will likely lead to the forced migrations of tens of millions of people in search of tolerable places to live. Environmental scientist Norman Myers says that projected climate change during this century could produce at least 150 million, and perhaps 250 million, environmental refugees. A 2009 study by a research institute led by former UN Secretary General Kofi Annan estimated that climate change already contributes to the premature
Air Pollution, Climate Change, and Ozone Depletion
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Figure 12-19 The shaded areas on this map are counties in the United States where one or both species of mosquitoes that transmit dengue fever have been found. Some scientists expect that projected climate change will expand the range of mosquitoes that carry dengue fever, a debilitating and potentially deadly disease. As of 2009, occurrences of this disease in the United States were limited to the U.S.–Mexico border and to parts of Hawaii. But some scientists warn that, with projected climate change, the disease could spread throughout the country.
deaths of more than 300,000 people annually—an average of 822 people a day. The report estimated that 325 million people—a number greater than the U.S. population—are now seriously affected by accelerating climate change through natural disasters and environmental degradation.
12-7 What Can We Do to Slow
Projected Climate Disruption? ▲
To slow the projected rate of atmospheric warming and climate change, we can increase energy efficiency, sharply reduce greenhouse gas emissions, rely more on renewable energy resources, and slow population growth.
CONC EPT 12-7
What Are Our Options? Many scientists argue that our most urgent priority is to do all we can to avoid any and all irreversible climate or ecological tipping points. Once we reach such a point, there is no going back. It is like going over a cliff. Figure 12-20 Atmospheric carbon level of 450 ppm Melting of all Arctic summer sea ice Collapse and melting of the Greenland ice sheet Severe ocean acidification, collapse of phytoplankton populations, and a sharp drop in the ability of the oceans to absorb CO2 Massive release of methane from thawing Arctic permafrost Collapse and melting of most of the western Antarctic ice sheet Severe shrinkage or collapse of Amazon rainforest
Tipping point
Figure 12-20 Environmental scientists have come up with this list of possible climate tipping points. They urge us to focus on avoiding these thresholds beyond which large-scale, irreversible, and possibly catastrophic climate changes can occur. The problem is that we do not know how close we are to such tipping points.
summarizes some of the tipping points that scientists are most concerned about. There are two basic approaches to dealing with projected climate disruption. One is to drastically reduce greenhouse gas emissions to slow down the rate of atmospheric warming and shift to noncarbonbased energy options in time to prevent major climate changes. The other is to recognize that some warming is unavoidable and to devise strategies to reduce its harmful effects. Most analysts believe we need a mix of both approaches. In 2006, NASA climate scientist James Hansen (Individuals Matter, p. 261) warned that we probably have no longer than a decade to mount a massive global effort to prevent an irreversible change in the earth’s climate that will fundamentally alter the planet, cause ecological and economic havoc, and threaten civilization as we know it. He and other prominent climate scientists urge policy makers and business leaders to mount an unprecedented crash program to cut global CO2 emissions 50–85% by 2050 in an effort to slow down or avoid their projected harmful effects that could last for thousands of years. In 2009, investors who collectively manage more than $13 trillion of the world’s financial assets issued a joint call for U.S. and international policy makers to come up with an effective international agreement on climate change. They warned that climate disruption poses a threat to the global economy and projected that moving to a low-carbon world is an enormous global investment opportunity. CONCEPT 12-7
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HOW WOULD YOU VOTE?
✓ ■
Should we take serious action now to help slow climate change as a result of human actions? Cast your vote online at www.cengage.com/login.
We Can Reduce the Threat We know a number of ways to slow the rate and GOOD degree of atmospheric warming and the resulting NEWS climate disruption caused by our activities, as summarized in Figure 12-21. The solutions listed on the left side of Figure 12-21 come down to three major strategies that together could reduce net CO2 emissions by 80%: improve energy efficiency to reduce fossil fuel use; shift from nonrenewable carbon-based fossil fuels to a mix of low-carbon renewable energy resources; and stop cutting down tropical forests while planting more trees to help remove more CO2 from the atmosphere.
Solutions Slowing Climate Disruption Pr e v e nt i o n
Cl e anup
Cut fossil fuel use (especially coal)
Remove CO2 from smokestack and vehicle emissions
Shift from coal to natural gas Improve energy efficiency Shift to renewable energy resources Transfer energy efficiency and renewable energy technologies to developing countries
Store (sequester) CO2 by planting trees Sequester CO2 in soil by using no-till cultivation and taking cropland out of production Sequester CO2 deep underground (with no leaks allowed)
Reduce deforestation Use more sustainable agriculture and forestry
Sequester CO2 in the deep ocean (with no leaks allowed)
Put a price on greenhouse gas emissions
Repair leaky natural gas pipelines and facilities
Reduce poverty
Use animal feeds that reduce CH4 emissions from cows (belching)
Slow population growth
Figure 12-21 These are some ways to slow atmospheric warming and the resulting projected climate change during this century (Concept 12-7). Questions: Which five of these solutions do you think are the most important? Why?
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Removing Carbon from the Atmosphere The solutions listed on the right side of Figure 12-21 are output, or cleanup, strategies that focus on dealing with CO2 after we have produced it. One such strategy is to increase the uptake of CO2 by planting trees on a massive scale. The 2007 global campaign to plant a billion trees, inspired by Nobel laureate Wangari Maathai (see Chapter 6, Individuals Matter, p. 117), is a start. A similar approach is to preserve and restore forests. Scientists have found that old-growth and secondgrowth natural forests store considerably more CO2 than comparable areas of tree plantations. Also, we can restore wetlands that have been drained for farming. Wetlands are very efficient at taking up CO2, and they provide other valuable natural services as well. Another cleanup approach is to plant large areas of degraded land with fast-growing perennial plants such as switchgrass that remove CO2 from the air and store it in the soil. To be successful, this approach could not involve clearing forests. Along these lines, a measure that is getting more attention among scientists is the use of biochar. Scientists have rediscovered this fertilizer that Amazon Basin natives used for growing crops several centuries ago. Producing it involves burning biomass such as chicken waste or wood in a low-oxygen environment to make a charcoal-like material. Biochar makes an excellent organic fertilizer that helps to keep carbon in the soil for as long as 1,000 years. While making biochar does release CO2, burying it stores considerably more CO2 in the soil. Farmers could plant fast-growing trees on degraded land and use them to make biochar. They could then make money selling this rich organic fertilizer. Another approach that is receiving a lot of attention is to remove CO2 from the smokestacks of coal-burning power and industrial plants and to store it somewhere. This approach is generally referred to as carbon capture and storage, or CCS (Science Focus, at right).
Governments Can Help to Reduce the Threat of Climate Change Governments can use five major methods to promote the solutions listed in Figure 12-21 (Concept 12-7). One is to strictly regulate carbon dioxide and methane as air pollutants, which they do not now consistently do. Second, governments could phase in carbon taxes on each unit of CO2 or CH4 emitted by fossil fuel use or place energy taxes on each unit of fossil fuel that is burned. To make this strategy more politically acceptable, such taxes could be offset by reducing taxes on income, labor, and profits. A third approach is to place a cap on total humangenerated greenhouse gas emissions in a country or region, issue permits to allow polluters to emit these pollutants,
Air Pollution, Climate Change, and Ozone Depletion
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S C I E NC E FO C U S Is Capturing and Storing CO2 the Answer?
O
utput strategies for dealing with CO2 (Figure 12-21, right) would allow us to keep burning fossils fuels. But they would require us to capture and store as much CO2 as possible in soil and vegetation, as well as underground and beneath the ocean floor, and to hope that none of it would ever leak out. Scientists are now exploring several of these carbon capture and storage (CCS) schemes, some of which involve intensive, high-tech efforts. Some researchers are studying ways to remove CO2 from smokestack fumes and to pump it deep underground into abandoned coal beds and oil and gas fields. Another approach is to liquefy it and inject it into sediments under the sea floor. However, it is becoming clear to scientists that stored CO2 would have to remain sealed from the atmosphere forever. Any large-scale leaks caused by earthquakes or other shocks,
as well as any number of smaller continuous leaks from CO2 storage sites around the world, could dramatically increase atmospheric warming and climate change in a very short time. Some scientists doubt that we can develop the technology to guarantee that all such captured CO2 would remain safely stored forever, without some of it leaking out. There are other problems. Removing all or most of the CO2 from smokestack emissions and transporting and storing it takes a lot of energy. This would greatly reduce the net energy yield and significantly raise the cost of burning coal to supply electricity. Power plants using CCS would also require 90% more freshwater than conventional coal plants use. Most worrisome to some scientists, CCS promotes the increased use of coal, the world’s most environmentally harmful fuel.
and then let those polluters trade their permits in the marketplace. This cap-and-trade approach (Figure 12-22) has a political advantage over taxes, but it is difficult to manage because there are so many emitters of greenhouse gases. In addition, this approach works only if the original caps are set low enough to encourage a serious reduction in greenhouse gas emissions and are lowered on a regular basis to promote further cuts. A fourth strategy is to level the economic playing field by greatly increasing government subsidies for using energy-efficiency technologies, low-carbon renewable-
Trade-Offs Cap and Trade Policies Adva nta ge s
Disad vant ag es
Clear legal limit on emissions
Revenues not predictable
Rewards cuts in emissions
& CAP DE TRA
Vulnerable to cheating
Record of success
Rich polluters can keep polluting
Low expense for consumers
Puts variable price on carbon
Figure 12-22 Using a cap-and-trade policy to help reduce greenhouse gas emissions has advantages and disadvantages. Questions: Which two advantages and which two disadvantages do you think are the most important? Why?
Environmental scientists such as Peter Montague argue that CCS is a costly and extremely risky output solution to a serious problem that can be dealt with by using a variety of cheaper, quicker, and safer input, or prevention, approaches (Figure 12-21, left). They argue for producing the electricity we need by using low-carbon energy resources such as energy efficiency, solar cells, and wind power. To these scientists, when we face a problem such as CO2 coming out of a smokestack or exhaust pipe, the most important question to ask is not What do we do with it? but, How do we avoid producing the CO2 in the first place? Critical Thinking Do you think that a government-supported crash program to build coal-burning power plants with CCS components would be a good investment? Explain.
energy technologies, and more sustainable agriculture. This would also include phasing out or sharply reducing subsidies and tax breaks for using fossil fuels, nuclear power, and unsustainable agriculture. A fifth strategy would focus on technology transfer. Governments of more-developed countries could help to fund the transfer of the latest green technologies mentioned above to less-developed countries. Reductions of greenhouse gas emissions will not be sufficient to avoid catastrophic climate change unless all nations partake in serious reductions. So it is in everyone’s interest to share technologies.
Governments Can Enter into International Climate Negotiations In December 1997, more than 2,200 delegates from 161 nations met in Kyoto, Japan, to negotiate a treaty to slow atmospheric warming and the resulting projected climate change. The first phase of the resulting Kyoto Protocol went into effect in February 2005 with 187 of the world’s 194 countries (not including the United States) ratifying the agreement by late 2009. This agreement requires the 36 participating moredeveloped countries to cut their emissions of CO2, CH4, and N2O to an average of at least 5.2% below their 1990 levels by 2012. Less-developed countries were excluded from this requirement in this first phase, because such reductions would curb their economic growth. The original protocol also allowed trading of greenhouse gas emissions among participating countries. For CONCEPT 12-7
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example, a country or business that reduces its CO2 emissions or plants trees receives a certain number of credits. It can use these credits to avoid having to reduce its emissions in other areas, it can bank them for future use, or it can sell them to other countries or businesses. However, the system has not worked well because the caps were set too high and greenhouse gas emissions have actually increased. Some analysts praise the original Kyoto agreement, along with the general non-binding agreements reached at the 2009 UN climate change conference in Copenhagen, Denmark, as small but important steps in attempting to slow projected climate change. They hope that rapidly developing nations such as China, Brazil, India, and Indonesia will agree to reduce their greenhouse gas emissions and that more-developed nations will agree to much deeper cuts in their greenhouse gas emissions during the next few decades. Other analysts see these agreements as weak and slow responses to an urgent global problem, pointing out that atmospheric carbon dioxide levels have increased 35% faster than was expected under the Kyoto agreement. Many have also concluded that a top-down international agreement will be too slow and ineffective. Some call for the nations that produce most of the world’s greenhouse gas emissions—especially the United States, China, India, Brazil, and the European Union nations—to get together and work out an agreement to sharply lower their emissions.
tric have set goals for seriously reducing their GOOD greenhouse gas emissions, knowing that this NEWS will also save them money. Between 1990 and 2006, DuPont slashed its energy usage and cut its greenhouse gas emissions by 72% and saved $3 billion, while the company increased its business by almost a third. Leaders of these and many other major companies see an enormous profit opportunity in developing or using energy-efficient and cleaner-energy technologies. Some colleges and universities are also taking action. Students and faculty at Oberlin College in the U.S. state of Ohio have asked their board of trustees to reduce the college’s CO2 emissions to zero by 2020 by purchasing or producing renewable energy. In the U.S. state of Pennsylvania, 25 colleges have joined to purchase wind power and other forms of primarily low-carbon renewable energy. Each of us plays a part in atmospheric warming and projected climate change. To calculate your carbon footprint, the amount of carbon dioxide generated by your lifestyle, you can go to several websites, including the following: nature.org/climatecalculator epa.gov/climatechange/emissions/ ind_calculator.html carbonfootprint.com climatecrisis.net/takeaction/carboncalculator gocarbonzero.org worldwildlife.org/carboncalculator
Some Governments, Corporations, and Individuals Are Leading the Way Some nations are leading others in facing the GOOD challenges of climate change. Costa Rica aims to NEWS be the first country to become carbon neutral by cutting its net carbon emissions to zero by 2030. The country generates 78% of its electricity with renewable hydroelectric power and another 18% from renewable wind and geothermal energy. China has the most intensive energy efficiency program in the world, according to ClimateWorks, a global energy-consulting firm. Chinese automobile fuel-efficiency standards are higher than U.S. standards, and China’s government is working with the country’s top 1,000 industries to implement tough energy efficiency goals. China is also rapidly becoming the world’s leader in developing and selling solar cells, solar water heaters, wind turbines, and plug-in hybrid electric cars. Some U.S. states have taken significant strides in dealing with climate change. By 2009, 30 U.S. states had in place goals for reducing greenhouse gas emissions. Since 1990, local governments in more than 650 cities around the world (including more than 450 U.S. cities) have established programs to reduce their greenhouse gas emissions. A growing number of major global companies, including Alcoa, DuPont, IBM, Toyota, and General Elec-
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Figure 12-23 lists some ways in which you can cut your CO2 emissions.
GOOD NEWS
What Can You Do? Reducing CO2 Emissions ■
Calculate your carbon footprint (see websites listed above)
■
Drive a fuel-efficient car, walk, bike, carpool, and use mass transit
■
Reduce garbage by recycling and reusing more items
■
Use energy-efficient appliances and compact fluorescent or LED lightbulbs
■
Wash laundry in warm or cold water
■
Dry clothes on a rack or line
■
Use a low-flow showerhead
■
Eat less meat or no meat
■
Heavily insulate your house and seal all air leaks
■
Use energy-efficient windows
■
Insulate your electric hot water heater (but not if it is gas-fired) and set it no higher than 49ºC (120ºF)
■
Plant trees to shade your house during summer
■
Buy from businesses working to reduce their emissions
Figure 12-23 Individuals matter: You can reduce your annual emissions of CO2. Question: Which of these steps, if any, do you take now or plan to take in the future?
Air Pollution, Climate Change, and Ozone Depletion
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Figure 12-24 Solutions: There are many ways for us to prepare for the possible long-term harmful effects of climate change. Questions: Which three of these adaptation plans do you think Waste less water are the most important? Why?
Develop crops that need less water
Connect wildlife reserves with corridors
Move hazardous material storage tanks away from coast
Move people away from low-lying coastal areas
Stockpile 1- to 5-year supply of key foods Prohibit new construction on low-lying coastal areas or build houses on stilts
Expand existing wildlife reserves toward poles
We Can Prepare for Climate Change According to recent global climate models, the world needs to make a 50–85% cut in emissions of greenhouse gases by 2050 to stabilize concentrations of these gases in the atmosphere and to help prevent the planet from heating up by more than 2oC (3.6oF).
However, because of the difficulty of making such large reductions, many analysts believe that while we work to slash emissions, we should also begin to prepare for the possible harmful effects of projected climate disruption. Figure 12-24 shows some other ways to do so.
12-8 How Have We Depleted Ozone in the
Stratosphere and What Can We Do about It? ▲
CONC EPT 12-8A
▲
CONC EPT 12-8B To reverse ozone depletion, we must stop producing ozonedepleting chemicals and comply with the international treaties that ban such chemicals.
Our widespread use of certain chemicals has reduced ozone levels in the stratosphere, which allows more harmful ultraviolet radiation to reach the earth’s surface.
Our Use of Certain Chemicals Threatens the Ozone Layer A layer of ozone in the lower stratosphere keeps about 95% of the sun’s harmful ultraviolet (UV) radiation from reaching the earth’s surface (Figure 12-1). How-
ever, measurements taken by meteorologists show a considerable seasonal depletion (thinning) of ozone concentrations in the stratosphere above Antarctica and the Arctic. Similar measurements reveal a lower overall ozone thinning everywhere except over the tropics. CONCEPTS 12-8A AND 12-8B
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Based on these measurements as well as mathematical and chemical models, the overwhelming consensus of researchers in this field is that ozone depletion in the stratosphere poses a serious threat to humans, other animals, and some primary producers (mostly plants) that use sunlight to support the earth’s food webs (Concept 12-8A). This problem began with the discovery of the first chlorofluorocarbon (CFC) in 1930. Chemists soon developed similar compounds to create a family of highly useful CFCs, known by their trade name of Freons. These chemically unreactive, odorless, nonflammable, nontoxic, and noncorrosive compounds seemed to be dream chemicals. Inexpensive to manufacture, they became popular as coolants in air conditioners and refrigerators, propellants in aerosol spray cans, cleaners for electronic parts such as computer chips, fumigants for granaries and ships’ cargo holds, and as gases used to make insulation and packaging. It turned out that CFCs were too good to be true. Starting in 1974 with the work of chemists Sherwood Rowland and Mario Molina (Individuals Matter, below), scientists demonstrated that CFCs are persistent chemicals that destroy protective ozone in the stratosphere. CFCs are not the only ozone-depleting chemicals; others are halons and hydrobromoflurocarbons (HBFCs) (used in fire extinguishers), methyl bromide (a widely used fumigant), hydrogen chloride (emitted into the stratosphere by the U.S. space shuttles), and cleaning solvents. Measurements and models indicate that 75–85% of the observed ozone losses in the stratosphere since 1976
are the result of CFCs and other ozone-depleting chemicals released into the atmosphere by human activities beginning in the 1950s.
Ozone Levels over the Earth’s Poles Drop for a Few Months Each Year In 1984, researchers analyzing satellite data discovered that each year, 40–50% of the ozone in the upper stratosphere over Antarctica disappeared during October and November. This observed loss of ozone has been called an ozone hole. A more accurate term is ozone thinning because the ozone depletion varies with altitude and location. When partial sunlight returns to Antarctica in October, huge masses of ozone-depleted air there flow northward and linger for a few weeks over parts of Australia, New Zealand, South America, and South Africa. This raises biologically damaging UV-B levels in these areas by 3–10% and in some years as much as 20%. In 1988, scientists discovered that similar, but usually less severe, ozone thinning occurs over the Arctic from February to June, resulting in a typical ozone loss of 11–38% (compared to a typical 50% loss above Antarctica). When this mass of air above the Arctic breaks up each spring, large masses of ozone-depleted air flow south to linger over parts of Europe, North America, and Asia. Models indicate that the Arctic is unlikely to develop the large-scale ozone thinning found over the Antarctic. They also project ozone depletion over the Antarctic and Arctic will be at its worst between 2010 and 2019.
I N D I V ID U ALS MAT T E R Sherwood Rowland and Mario Molina—A Scientific Story of Expertise, Courage, and Persistence
I
n 1974, calculations by chemists Sherwood Rowland and Mario Molina at the University of California–Irvine indicated that chlorofluorocarbons (CFCs) were lowering the average concentration of ozone in the stratosphere. They shocked both the scientific community and the $28-billion-per-year CFC industry by calling for an immediate ban of CFCs in spray cans, for which substitutes were available. The research of these two scientists led them to four major conclusions. First, once injected into the atmosphere, these persistent CFCs remain there. Second, over 11–20 years, these compounds rise into the stratosphere through convection, random drift, and the turbulent mixing of air in the lower atmosphere.
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Third, once they reach the stratosphere, the CFC molecules break down under the influence of high-energy UV radiation. This releases highly reactive chlorine atoms (Cl), as well as atoms of fluorine (F) and bromine (Br), all of which accelerate the breakdown of ozone (O3) into O2 and O in a cyclic chain of chemical reactions. As a consequence, ozone is destroyed faster than it forms in some parts of the stratosphere. Fourth, each CFC molecule can last in the stratosphere for 65–385 years, depending on its type. During that time, each chlorine atom released during the breakdown of CFCs can convert hundreds of O3 molecules to O2. The CFC industry (led by DuPont) was a powerful, well-funded adversary with a lot of
profits and jobs at stake. It attacked Rowland and Molina’s calculations and conclusions, but the two researchers held their ground, expanded their research, and explained their results to other scientists, elected officials, and the media. After 14 years of delaying tactics, DuPont officials acknowledged in 1988 that CFCs were depleting the ozone layer and they agreed to stop producing them. In 1995, Rowland and Molina received the Nobel Prize in chemistry for their work on CFCs. In awarding the prize, the Royal Swedish Academy of Sciences said that these two scientists contributed to “our salvation from a global environmental problem that could have had catastrophic consequences.”
Air Pollution, Climate Change, and Ozone Depletion
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Natural Capital Degradation Effects of Ozone Depletion Human Health
Wildlife
Worse sunburns
Increased eye cataracts in some species
More eye cataracts and skin cancers
Decreased populations of aquatic species sensitive to UV radiation
Immune system suppression Reduced populations of surface phytoplankton Food and Forests Disrupted aquatic food webs from reduced phytoplankton Reduced yields for some crops Air Pollution and Materials Reduced seafood supplies from reduced phytoplankton Increased acid deposition Decreased forest productivity for UV-sensitive tree species Increased photochemical smog Climate Change Degradation of outdoor paints and plastics While in troposphere, CFCs act as greenhouse gases
Figure 12-25 Decreased levels of ozone in the stratosphere can have a number of harmful effects. (Concept 12-8A). Questions: Which three of these effects do you think are the most threatening? Why?
Why Should We Worry about Ozone Depletion? Why should we care about ozone loss? Figure 12-25 lists some of the expected effects of decreased levels of ozone in the stratosphere. One effect is that more biologically damaging UV radiation will reach the earth’s surface (Concept 12-8A). This will give people worse sunburns, more eye cataracts, and more skin cancers (Science Focus, p. 272). The most serious threat from ozone depletion is that the resulting increase in UV radiation can impair or destroy phytoplankton, especially in Antarctic waters. These tiny marine plants play a key role in removing CO2 from the atmosphere. They also form the base of ocean food webs. Destroying them would eliminate the vital ecological services they provide. Figure 12-26 lists ways in which you can pro- GOOD NEWS tect yourself from harmful UV radiation.
We Can Reverse Stratospheric Ozone Depletion According to ozone depletion researchers, we should immediately stop producing all ozone-depleting chemicals (Concept 12-8B). However, even with immediate and sustained action, models indicate it will take about 60 years for the ozone layer to return to 1980 levels and about 100 years for recovery to pre-1950 levels. Substitutes are available for most uses of CFCs, and others are being developed. In 1987, representatives of 36 nations met in Montreal, Canada, and developed the Montreal Protocol. This
treaty’s goal was to cut emissions of CFCs (but not other ozone-depleting chemicals) by about 35% between 1989 and 2000. After hearing more bad news about seasonal ozone thinning above Antarctica in 1989, representatives of 93 countries met in London in 1990 and then in Copenhagen, Denmark, in 1992. They adopted the Copenhagen Protocol, an amendment that accelerated the phasing out of key ozone-depleting chemicals.
What Can You Do? Reducing Exposure to UV Radiation ■
Stay out of the sun, especially between 10 A.M. and 3 P.M.
■
Do not use tanning parlors or sunlamps.
■
When in the sun, wear protective clothing and sunglasses that protect against UV-A and UV-B radiation.
■
Be aware that overcast skies do not protect you.
■
Do not expose yourself to the sun if you are taking antibiotics or birth control pills.
■
When in the sun, use a sunscreen with a protection factor of at least 15.
■
Examine your skin and scalp at least once a month for moles or warts that change in size, shape, or color and sores that do not heal. If you observe any of these signs, consult a doctor immediately.
Figure 12-26 Individuals matter: You can reduce your exposure to harmful UV radiation. Question: Which of these precautions do you already take?
CONCEPTS 12-8A AND 12-8B Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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SCIE N C E FO C US Skin Cancer
R
esearch indicates that exposure to the UV-B ionizing radiation in sunlight is the primary cause of squamous cell and basal cell skin cancers, which together account for 95% of all skin cancers. Typically, a 15- to 40-year lag separates excessive exposure to UV-B and development of these cancers. Caucasian children and adolescents who experience only a single severe sunburn double their chances of getting these two types of cancers. Some 90–95% of these types of skin cancer can be cured if detected early enough, although their removal may leave disfiguring scars. These cancers kill 1–2% of their victims, which amounts to about 2,300 deaths in the United States each year.
A third type of skin cancer, malignant melanoma, occurs in pigmented areas such as moles. Within a few months, this type of cancer can spread to other organs. It kills about one-fourth of its victims (most younger than age 40) within 5 years, despite surgery, chemotherapy, and radiation treatments. Each year, it kills about 100,000 people (including 7,700 Americans), mostly Caucasians. A 2003 study found that women who visited tanning parlors once a month or more increased their chance of developing malignant melanoma by 55%. The risk was highest for young adults. A 2004 study at Dartmouth College found that people using tanning beds
These landmark international agreements, now signed by 191 countries, are important examples of global cooperation in response to a serious global environmental problem (Concept 12-8B). If nations continue to follow these agreements, ozone levels should return to 1980 levels by 2068 and to 1950 levels by 2100. The ozone protocols set an important precedent by using prevention to solve a serious environmental problem. Nations and companies agreed to work together to solve this global problem for three reasons. First, there was convincing and dramatic scientific evidence of a serious problem. Second, CFCs were produced by a small number of international companies. Third, the certainty that CFC sales would decline over a period of years unleashed the economic and creative resources of the private sector to find even more profitable and safer substitute chemicals. However, the most widely used substitutes, such as HCFC-22, cause some ozone depletion as well. In 2007, delegates from 191 nations met in Montreal, Canada, and agreed to phase out the production of HCFCs. On its trip to the stratosphere, a typical HCFC molecule helps to warm the troposphere up to 10,000 times more than a molecule of CO2. Thus, phasing out HCFCs to help protect the stratosphere will also help to reduce the projected warming of the troposphere. We can use the three principles of sustainability to help reduce the problems of air pollution, climate change, and stratospheric ozone deple-
were also more likely to develop basal cell and squamous cell skin cancers. People (especially Caucasians) who experience three or more blistering sunburns before age 20 are five times more likely to develop malignant melanoma than those who have never had severe sunburns. About one of every ten people who get malignant melanoma has an inherited gene that makes them especially susceptible to the disease. Critical Thinking Does knowledge of skin cancer risks make you more likely to protect yourself from the sun? Explain.
tion. We can reduce inputs of pollutants, greenhouse gases, and ozone-depleting chemicals into the troposphere by relying more on direct and indirect forms of solar energy and relying less on fossils fuels. We can also sharply reduce the waste of matter and energy resources and reuse and recycle matter resources. Finally, we can mimic biodiversity by using a variety of low-carbon renewable energy resources based on local and regional availability. Here are this chapter’s three big ideas: ■ We need to put our primary emphasis on preventing outdoor and indoor air pollution throughout the world, in order to reduce the serious harmful health effects of pollution. ■ Considerable scientific evidence indicates that the earth’s atmosphere is warming, at least partly because of human activities, and that this is likely to lead to significant climate change during this century that could have severe and long-lasting harmful consequences. ■ Reducing the projected harmful effects of rapid climate disruption and ozone thinning during this century requires emergency action to increase energy efficiency, sharply reduce greenhouse gas emissions, shift to renewable energy resources as much as possible, slow population growth, and phase out the use of ozone-depleting chemicals.
People who say it cannot be done should not interrupt those who are doing it. GEORGE BERNARD SHAW
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Air Pollution, Climate Change, and Ozone Depletion
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REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 243. Define and distinguish among atmosphere, troposphere, stratosphere, and ozone layer. Describe how the troposphere and stratosphere differ. Distinguish between weather and climate. List three major factors that determine how heat and moisture are distributed in the atmosphere. Define ocean currents and describe how they affect climate. Define greenhouse gases, describe the greenhouse effect, and explain why the latter is important to life on earth. 2. What is air pollution? Distinguish between primary pollutants and secondary pollutants, and give an example of each. Distinguish between industrial smog and photochemical smog, and describe how each is formed. List five natural factors that help to reduce outdoor air pollution and six natural factors that help to worsen it. What is a temperature inversion and how can it affect air pollution levels? 3. What is acid deposition and how does it form? Explain why it is a regional problem and briefly describe its major environmental impacts on ecosystems and human health. List the major ways to reduce acid deposition. 4. Why is indoor air pollution alarming, according to the EPA, and what are the top three indoor air pollutants in the United States? What is the major indoor air pollutant in many of the less-developed countries? Describe indoor air pollution by radon-222 and what can be done about it. 5. Briefly describe the human body’s defenses against air pollution, how air pollution can overwhelm them, and the illnesses that can result. About how many people die prematurely from air pollution each year? 6. Describe air pollution laws in the United States. Summarize the story of lead pollution. Summarize the accomplishments of U.S. laws and discuss how we can improve them. List the advantages and disadvantages of using an emissions trading program. Summarize the major ways to reduce emissions from power plants and motor vehicles, and the ways to reduce indoor air pollution. 7. Describe atmospheric warming and cooling over the past 900,000 years and during the last century. Discuss the
conclusions of the IPCC and the general agreement among most climate scientists about atmospheric warming. List four examples of evidence that support this consensus. Summarize James Hansen’s contribution to the public discussion about climate change. Describe the role of the oceans in helping to regulate the average atmospheric temperature. Describe how each of the following might affect atmospheric warming: (a) cloud cover and (b) air pollution. 8. Briefly describe the projected effects of climate change on drought, ice cover, sea levels, permafrost, extreme weather, biodiversity, crop yields, and human health during this century. List six possible climate tipping points. What are three major strategies for slowing projected climate disruption? What are four strategies for dealing with CO2 after it has been produced? Discuss the work of scientists exploring carbon capture and storage (CCS) strategies and the benefits and drawbacks of CCS. 9. List five things that governments could do to help slow projected climate change. What are the pros and cons of the Kyoto Protocol? Give two examples of what some governments and major corporations have done to reduce their carbon footprint. List five ways in which you can reduce your carbon footprint. List five ways in which we can prepare for the projected long-term harmful effects of climate disruption. 10. Describe how human activities have depleted ozone in the stratosphere and list five harmful effects of such depletion. Describe how scientists Sherwood Roland and Mario Molina helped awaken the world to this threat. Explain how ozone levels over the earth’s poles drop during a few months each year and the harmful effects of such thinning on humans. Describe the relationships between higher UV levels and skin cancer. What has the world done to reduce the threat from ozone depletion in the stratosphere? How can we apply the three principles of sustainability to the problems of air pollution, climate change, and ozone depletion?
Note: Key terms are in bold type.
CRITICAL THINKING 1. China relies on coal for two-thirds of its commercial energy usage, partly because the country has abundant supplies of this resource. Yet China’s coal burning has caused innumerable and growing problems for China and for neighboring countries. Do you think China is justified in developing this resource to the maximum, as other
countries, including the United States, have done with their resources? Explain. What are its alternatives? 2. Photochemical smog is largely the result of motor vehicle emissions. Considering your use of motor vehicles, now and in the future, what are three ways in which you could reduce your contribution to photochemical smog?
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3. List three important ways in which your life would be different today if grassroots actions by U.S. citizens between the 1970s and 1990s had not led to the Clean Air Acts of 1970, 1977, and 1990, despite massive political opposition from the affected industries. List three important ways in which your life in the future might be different if grassroots actions now do not lead to strengthening of the U.S. Clean Air Act or a similar law in the country where you live. 4. A top U.S. presidential economic adviser once gave a speech in Williamsburg, Virginia (USA), to representatives of governments from a number of countries. He told his audience not to worry about projected climate change because the average global temperature increases predicted by scientists were much less than the temperature increase he had experienced that day in traveling from Washington, DC, to Williamsburg. What was the flaw in his reasoning? Write an argument that you could use to counter his claim.
5. What changes might occur in (a) the global hydrologic cycle (see Figure 2-19, p. 41) and (b) the global carbon cycle (see Figure 2-20, p. 42) if the atmosphere continues to experience significant warming? Explain. 6. One way to help slow the rate of CO2 emissions is to reduce the clearing of forests—especially in tropical developing countries where intense deforestation is taking place. Should the United States and other more-developed countries pay poorer countries to stop cutting their forests? Explain. 7. Congratulations! You are in charge of the world. List your three most important actions for dealing with the problems of (a) outdoor air pollution, (b) indoor air pollution, (c) projected climate disruption, and (d) depletion of ozone in the stratosphere. 8. List two questions that you would like to have answered as a result of reading this chapter.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 12 for many study aids and ideas for further
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reading and research. These include flashcards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
Air Pollution, Climate Change, and Ozone Depletion
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Urbanization and Solid and Hazardous Waste
13
Key Questions and Concepts 13-1 What are the major population trends and problems in urban areas?
hazardous waste contributes to pollution, natural capital degradation, and human health problems.
C O N C E P T 1 3 - 1 Urbanization continues to increase steadily, and most cities are unsustainable because of high levels of resource use and waste, as well as pollution and poverty.
13-2 How does transportation affect urban environmental impacts?
13-5
How should we deal with solid waste?
A sustainable approach to solid waste is first to reduce it, then to reuse or recycle it, and finally to safely dispose of what is left.
CONCEPT 13-5A
Technologies for burning and burying solid wastes are well developed, but burning contributes to pollution and greenhouse gas emissions, and buried wastes eventually contribute to the pollution and degradation of land and water resources.
CONCEPT 13-5B
C O N C E P T 1 3 - 2 In some countries, many people live in dispersed urban areas and depend mostly on motor vehicles for their transportation, which greatly expands their ecological footprints.
13-3 How can cities become more sustainable and livable? Urban land-use planning can help to reduce uncontrolled sprawl and slow the resulting degradation of air, water, land, biodiversity, and other natural resources.
CONCEPT 13-3A
An ecocity allows people to choose walking, biking, or mass transit for most transportation needs; to recycle or reuse most of their wastes; to grow much of their food; and to protect biodiversity by preserving surrounding land.
CONCEPT 13-3B
13-6 How should we deal with hazardous waste? C O N C E P T 1 3 - 6 A sustainable approach to hazardous waste is first to produce less of it, then to reuse or recycle it, then to convert it to less hazardous materials, and finally to safely store what is left.
13-7 How can we make the transition to a more sustainable low-waste society? C O N C E P T 1 3 - 7 Shifting to a low-waste society will require individuals and businesses to reduce resource use and to reuse and recycle more of their wastes at local, national, and global levels.
What are solid waste and hazardous waste, and why are they problems? 13-4
Solid waste contributes to pollution and represents the unnecessary consumption of resources;
CONCEPT 13-4
The city is not an ecological monstrosity. It is rather the place where both the problems and the opportunities of modern technological civilization are most potent and visible. PETER SELF
Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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13-1 What Are the Major Population
Trends and Problems in Urban Areas? ▲
Urbanization continues to increase steadily, and most cities are unsustainable because of high levels of resource use and waste, as well as pollution and poverty.
C O NC EPT 13-1
Half of the World’s People Live in Urban Areas
proportion of the global population living in urban areas is increasing (Concept 13-1). Between 1850 and 2009, the percentage of people living in urban areas increased from 2% to 50%, and it could reach 66% by 2030. About 88% of this growth will occur in already overcrowded and stressed cities in less-developed countries. Second, the numbers and sizes of urban areas are mushrooming. Each week, more than 1 million people are added to the world’s urban areas. Demographers project that by 2025, China will add 60 new cities, each hosting 1.5 million to 5 million people. By comparison, the United States currently has just 9 cities of more than 1 million people (see the Case Study that follows). Around the world, there are 18 megacities or megalopolises—cities with 10 million or more people—up from 8 in 1985. Fifteen of them are in less-developed countries (Figure 13-1). Megacities will soon be eclipsed by hypercities with more than 20 million people. Tokyo, Japan, with 35 million people, is the largest city in this category.
Urbanization is the creation and growth of urban and suburban areas. It is measured as the percentage of the people in a country or in the world living in such areas. Urban growth is the rate of increase of urban populations. The world’s first cities emerged about 6,000 years ago. Since then, the world has become increasingly urbanized. Today, half of the world’s people, and 79% of Americans, live in urban areas. Urban areas grow in two ways—by natural increase (more births than deaths) and by immigration, mostly from rural areas. Some rural people are pulled to urban areas in search of jobs and a better life. Others are pushed from rural to urban areas by factors such as poverty, declining agricultural jobs, famine, and war. Four major trends are important for understanding the problems and challenges of urban growth. First, the
Delhi 18.6 million
Moscow 15 million
Hong Kong 15.8 million
Beijing 22 million
Tokyo 32 million
London 12.9 million
Los Angeles 15.2 million
New York 19.7 million
Mexico City 20.5 million
Shanghai 17 million
Cairo 14.5 million
Lagos 13.4 million
Karachi 11.8 million
Buenos Aires 13.1 million
Seoul 20.6 million Manila 16.3 million
Kolkata (Calcutta) 15.1 million
Rio de Janeiro 12 million São Paulo 18.9 million
Osaka 17.4 million
Mumbai (Bombay) 19.2 million
Bangkok 12 million Dhaka 13 million
Jakarta 18.9 million
Figure 13-1 Global outlook: Major urban areas throughout the world are revealed in these satellite images of the earth at night, showing city lights. Currently, the 50% of the world’s people that live in urban areas occupy about 2% of the earth’s land area. Note that most of the urban areas are found along the continental coasts. This figure also shows the populations of the world’s 18 megacities (each with 10 million or more people) in 2010. All but three are located in less-developed countries. Question: In order, what were the world’s five most populous cities in 2010? (Data from National Geophysics Data Center, National Oceanic and Atmospheric Administration, and United Nations)
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Urbanization and Solid and Hazardous Waste
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Third, urban growth is much slower in more-developed countries than in less-developed countries. However, moredeveloped countries, now with 75% urbanization, are projected to reach 81% urbanization by 2030. Fourth, poverty is becoming increasingly urbanized, primarily in less-developed countries. The United Nations estimates that at least 1 billion people in less-developed countries (more than three times the current U.S. population) live in crowded and unsanitary slums and shantytowns within most cities or on their outskirts. Within 30 years, this number may double. ■ CAS E S TUDY
Urbanization in the United States Between 1800 and 2008, the percentage of the U.S. population living in urban areas increased from 5% to 79%. This population shift has occurred in four phases. First, people migrated from rural areas to large central cities. Currently, three-fourths of Americans live in cities with at least 50,000 people, and nearly half live in urban areas with 1 million or more residents (Figure 13-2). Second, many people migrated from large central cities to smaller cities and suburbs. Currently, about half of urban Americans live in the suburbs, nearly a third in central cities, and the rest in rural housing developments beyond suburbs. Third, many people migrated from the North and East to the South and West. Since 1980, about 80% of the U.S. population increase has occurred in the South and West. Between 2009 and 2043, demographers project that the fastest growing U.S. states will continue to be Nevada, Arizona, and Florida. Fourth, since the 1970s, and especially since 1990, some people have fled both cities and suburbs, and migrated to developed rural areas. The result has been the rapid growth of exurbs—housing developments scattered over vast areas that lie beyond suburbs and have no socioeconomic centers. Since 1920, many of the worst urban environ- GOOD mental problems in the United States have been NEWS
reduced significantly. Most people have better working and housing conditions, while air and water quality have improved. Better sanitation, clean public water supplies, and medical care have slashed death rates and incidences of sickness from infectious diseases. Concentrating most of the population in urban areas also has helped protect the country’s biodiversity by reducing the destruction and degradation of wildlife habitat. However, a number of U.S. cities—especially older ones—have deteriorating services and aging infrastructures (streets, bridges, dams, power lines, sewers, water supply pipes, waste management, and schools). Indeed, according to a 2009 study by the American Society of Civil Engineers (ASCE), the United States has fallen $2.2 trillion behind in maintaining its public infrastructure. This amounts to more than $7,000 for each U.S. citizen. At the same time, many U.S. cities face budget crises and the resulting cuts to public services, as businesses and people move to the suburbs and exurbs, and city revenues from property taxes decline.
Urban Sprawl Gobbles Up the Countryside In the United States and some other countries, urban sprawl—the growth of low-density development on the edges of cities and towns—is eliminating surrounding agricultural and wild lands. It results in a far-flung hodgepodge of housing developments, shopping malls, parking lots, and office complexes that are loosely connected by multilane highways and freeways. In a nutshell, urban sprawl is the product of affordable land, automobiles, cheap gasoline, and little or no urban planning. Figure 13-3 (p. 278) summarizes some of the undesirable consequences of urban sprawl. Sprawl forces people to drive more, which adds to pollution and greenhouse gas emissions. It has decreased energy efficiency, increased traffic congestion, and destroyed prime cropland, forests, and wetlands. It has also led to the economic death of many central cities as people and businesses move out of these areas. On the other hand, many people prefer living in suburbs and exurbs. Compared to central cities, these areas provide lower-density living and access to larger lot sizes and single-family homes. Often they also have newer public schools and lower crime rates.
Figure 13-2 About eight of every ten Americans live in urban areas, which occupy a small but growing fraction of the country’s land area. Nearly half (48%) of Americans live in consolidated metropolitan areas with 1 million or more people. These areas are projected to merge into the megacities shown by the shaded areas in this figure. (Data from U.S. Census Bureau)
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Figure 13-3 These are some of the undesirable impacts of urban sprawl, which is a car-dependent form of development. Questions: Which five of these effects do you think are the most harmful? Why? Explain whom or what is harmed and how they are harmed.
Natural Capital Degradation Urban Sprawl
Water
Land and Biodiversity Loss of cropland Loss and fragmentation of forests, grasslands, wetlands, and wildlife habitat
Increased use and pollution of surface water and groundwater Increased runoff and flooding
As they grow outward, separate urban areas sometimes merge to form megacities. For example, the remaining open spaces between the U.S. cities of Boston, Massachusetts, and Washington, DC, are rapidly urbanizing and coalescing. The result is an almost 800kilometer-long (500-mile-long) urban area that contains about 35 million people and is sometimes called Bowash (Figure 13-4).
Urbanization Has Advantages Urbanization has many benefits. From an economic GOOD standpoint, cities are centers of economic develop- NEWS ment, innovation, education, technological advances, and jobs. They serve as centers of industry, commerce, and transportation.
Bowash (Boston to Washington)
Boston
Springfield Hartford
Providence
Allentown Newark
New York
Harrisburg Philadelphia Baltimore Washington Figure 13-4 This map shows the U.S. megalopolis of Bowash, consisting of urban sprawl between Boston, Massachusetts, and Washington, DC. Question: What are two ways in which this development might be harming ecosystems along the Atlantic Coast?
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Energy, Air, and Climate Increased energy use and waste Increased emissions of carbon dioxide and other air pollutants
Economic Effects Decline of downtown business districts More unemployment in central cities
Urban residents in many parts of the world tend to live longer than do rural residents and urban areas tend to have lower infant mortality and fertility rates. Residents also have better access to medical care, family planning, education, and social services than do their rural counterparts. Urban areas also have some environmental advantages. Recycling is more economically feasible because concentrations of recyclable materials and funding for recycling programs tend to be higher in urban areas. Concentrating people in cities also helps to preserve biodiversity by reducing the stress on wildlife habitats.
Urbanization Has Disadvantages Half of the world’s 6.9 billion people live in urban areas and each year about 63 million people—an average of nearly 7,200 per hour—are added to these areas. Such intense population pressure and high population densities make most of the world’s cities more environmentally unsustainable every year. Consider some of the problems faced by cities. (Also, see the Case Study on page 280.) Cities Have Huge Ecological Footprints. According to the Worldwatch Institute, although urban populations occupy only about 2% of the earth’s land area, they consume about 75% of its resources and produce about 75% of all human-generated CO2 emissions. Because of this high resource input and the resulting high waste output (Figure 13-5), most of the world’s cities are not self-sustaining systems (Concept 13-1). By concentrating people in relatively small areas, urbanization helps to preserve some of the earth’s biodiversity. But at the same time, large areas of land must be disturbed and degraded to provide urban dwellers with food, water, energy, minerals, and other
Urbanization and Solid and Hazardous Waste
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Inputs Energy Food Water
Outputs Solid wastes Waste heat Air pollutants Water pollutants
Raw materials Manufactured goods
Greenhouse gases Manufactured goods Noise
Money Information
London
resources. This decreases and degrades the earth’s overall biodiversity. Thus, urban areas have huge ecological footprints that extend far beyond their boundaries. If you live in a city, you can calculate its ecological footprint by going to the website www.redefiningprogress.org/. Most Cities Lack Vegetation. In urban areas, most trees, shrubs, grasses, and other plants are destroyed to make way for buildings, roads, parking lots, and housing developments. Thus, most cities do not benefit from vegetation that would absorb air pollutants, give off oxygen, provide shade, muffle noise, reduce soil erosion, provide urban wildlife habitats, and give aesthetic pleasure. Cities Often Have Water Problems. As cities grow and their water demands increase, expensive reservoirs and canals must be built and deeper wells must be drilled. This can deprive rural and wild areas of surface water and can deplete underground water supplies. Flooding also tends to be greater in some cities that are built on floodplains near rivers or along low-lying
Wealth Ideas
Figure 13-5 Natural capital degradation: Urban areas are rarely sustainable systems (Concept 13-1). The typical city depends on large nonurban areas for huge inputs of matter and energy resources, while it generates large outputs of waste matter and heat. According to an analysis by Mathis Wackernagel and William Rees, developers of the ecological footprint concept, London, England, requires an area 58 times as large as the city to supply its residents with resources. They estimate that if all of the world’s people used resources at the same rate as Londoners do, it would take at least three more planet Earths to meet their needs. Question: How would you apply the three principles of sustainability (see back cover) to lessen some of these impacts?
coastlines subject to natural flooding. In addition, covering land with buildings, asphalt, and concrete causes precipitation to run off quickly and overload storm drains. Further, urban development has often destroyed or degraded large areas of wetlands that have served as natural sponges to help absorb excess storm water. Many of the world’s largest coastal cities (Figure 13-1) face a new threat of flooding some time in this century as sea levels rise because of projected climate change (see Chapter 12, p. 264). Cities Concentrate Pollution and Health Problems. Because of their high population densities and high resource consumption, cities produce most of the world’s air pollution, water pollution, and solid and hazardous wastes. Pollutant levels are generally higher because pollution is produced in a smaller area and cannot be dispersed and diluted as readily as pollution produced in rural areas can. In addition, high population densities in urban areas can increase the spread of infectious diseases, especially if adequate drinking water and sewage systems are not available. CONCEPT 13-1
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Cities Generate Excessive Noise. Most urban dwellers are subjected to noise pollution: any unwanted, disturbing, or harmful sound that damages, impairs, or interferes with hearing, causes stress, hampers concentration and work efficiency, or causes accidents. Noise levels are measured in decibel-A (dbA) sound pressure units that vary with different human activities. Sound pressure becomes damaging at about 85 dbA and painful at around 120 dbA. At 180 dbA, it can kill. Urbanization Affects Local Climates and Causes Light Pollution. On average, cities tend to be warmer, rainier, foggier, and cloudier than suburbs and nearby rural areas. In cities, the enormous amount of heat generated by cars, factories, furnaces, lights, air conditioners, and heat-absorbing dark roofs and streets creates an urban heat island that is surrounded by cooler suburban and rural areas. As cities grow and merge, their heat islands merge, which can reduce the natural dilution and cleansing of polluted air. The artificial light created by cities (Figures 13-1, left and 13-4) is a form of light pollution that affects some plant and animal species. For example, some endangered sea turtles lay their eggs on beaches at night and require darkness to do so. In addition, each year large numbers of migrating birds, lured off course by the lights of highrise buildings, fatally collide with these structures. Light pollution also makes it difficult for astronomers and urban dwellers to study and enjoy the night sky.
Life Is a Desperate Struggle for the Urban Poor in Less-Developed Countries Poverty is a way of life for many urban dwellers in lessdeveloped countries. At least 1 billion people live under crowded and unsanitary conditions in cities in these countries (see the Case Study that follows). Some live in slums—areas dominated by dilapidated tenements and rooming houses where numerous people might live in a single room. Others live in squatter settlements and shantytowns on the outskirts of cities. They build shacks from corrugated metal, plastic sheets, scrap wood, cardboard, and other scavenged building materials, or they live in the streets. These people usually lack clean water supplies, sewers, electricity, and roads, and are exposed to severe air and water pollution as well as hazardous wastes from nearby factories. Many of these settlements are in locations especially prone to landslides, flooding, or earthquakes. Some city governments regularly bulldoze squatter shacks and send police to drive illegal settlers out. The settlers usually move back in within a few days or weeks, or build another shantytown elsewhere. Some municipal governments in countries such as Brazil and Peru legally recognize existing slums and grant legal titles to the land. They base this on evidence that poor people usually improve their living conditions
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once they know they have a permanent place to live. They can then become productive working citizens who contribute to tax revenues that, in turn, pay for the government programs that assist the poor.
■ C AS E S T UDY
Mexico City Mexico City—the world’s second most populous city— is an urban area in crisis. Its 20 million residents number about the same as the entire population of Australia or of the U.S. state of New York. Every year, at least 400,000 new residents arrive. Mexico City suffers from severe air pollution, close to 50% unemployment, deafening noise, overcrowding, traffic congestion, inadequate public transportation, and a soaring crime rate. More than one-third of its residents live in slums called barrios or in squatter settlements that lack running water and electricity. At least 3 million people in the barrios have no sewage facilities. As a result, huge amounts of human waste are deposited in gutters, vacant lots, and open ditches every day, attracting armies of rats and swarms of flies. When the winds pick up dried excrement, a fecal snow blankets parts of the city. This bacteria-laden fallout leads to widespread salmonella and hepatitis infections, especially among children. Mexico City has one of the world’s worst air pollution problems because of a combination of factors: too many cars, polluting factories, a warm, sunny climate and thus more smog, and topographical bad luck. The city sits in a high-elevation, bowl-shaped valley surrounded on three sides by mountains—conditions that can trap air pollutants at ground level. Breathing its air is said to be roughly equivalent to smoking three packs of cigarettes per day, and respiratory diseases are rampant. The city’s air and water pollution cause an estimated 100,000 premature deaths per year. Writer Carlos Fuentes has nicknamed it “Makesicko City.” Large-scale water withdrawals from the city’s aquifer have caused parts of the city to subside by 9 meters (30 feet) during the last century. Some areas are now subsiding as much as 30 centimeters (1 foot) a year. The city’s growing population increasingly relies on pumping in water from as far away as 150 kilometers (93 miles) and then using large amounts of energy to pump the water 1,000 meters (3,300 feet) uphill to reach this high-elevation city. Progress has been made in solving some of GOOD Mexico City’s problems. The percentage of days NEWS each year in which air pollution standards are violated has fallen from 50% to 20%. The city government has banned cars in its central zone, required air pollution controls on all cars made after 1991, phased out the use of leaded gasoline, and called for old buses, taxis, and delivery trucks to be replaced with cleaner vehicles. The city also bought land for use as green space and planted more than 25 million trees to help absorb pollutants.
Urbanization and Solid and Hazardous Waste
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13-2 How Does Transportation
Affect Urban Environmental Impacts? ▲
In some countries, many people live in dispersed urban areas and depend mostly on motor vehicles for their transportation, which greatly expands their ecological footprints.
CONC EPT 13-2
Cities Can Grow Outward or Upward If a city cannot spread outward, it must grow vertically—upward and downward (below ground)—so that it occupies a small land area with a high population density. Most people living in compact cities such as Hong Kong, China, and Tokyo, Japan, get around by walking, biking, or using mass transit. In other parts of the world, a combination of plentiful land, relatively cheap gasoline, and networks of highways have produced dispersed cities whose residents depend on motor vehicles for most travel (Concept 13-2). Such car-centered cities are found in the United States, Canada, Australia, and other countries where ample land often is available. The resulting urban sprawl can have a number of undesirable effects (Figure 13-3). The United States is a prime example of a car-centered nation. With 4.5% of the world’s people, the United States has almost one-third of the world’s passenger cars and commercial vehicles. In its dispersed urban areas, passenger vehicles are used for 98% of all transportation, and three of every four residents drive alone to work every day. Largely because of urban sprawl, all Americans combined drive about the same distance each year as the total distance driven by all other drivers in the world combined, and in the process, use about 43% of the world’s gasoline.
Motor Vehicles Have Advantages and Disadvantages Motor vehicles provide mobility and offer a convenient and comfortable way to get from one place to another. For many people, they are also symbols of power, sex appeal, social status, and success. Much of the world’s economy is also built on producing motor vehicles and supplying fuel, roads, services, and repairs for them. Despite their important benefits, motor vehicles have many harmful effects on people and the environment. Globally, automobile accidents kill approximately 1.2 million people a year—an average of nearly 3,300 premature deaths per day—and injure another 15 million people. They also kill about 50 million wild animals and family pets every year. In the United States, motor vehicle accidents kill more than 40,000 people per year and injure another 5 million, at least 300,000 of them severely. Car acci-
dents have killed more Americans than have all the wars in the country’s history. Motor vehicles are the world’s largest source of outdoor air pollution, which causes 30,000–60,000 premature deaths per year in the United States, according to the Environmental Protection Agency. They are also the fastest-growing source of climate-changing CO2 emissions. In addition, they account for two-thirds of the oil used in the form of gasoline in the United States and one-third of the world’s oil consumption. Motor vehicles have helped to create urban sprawl. At least a third of the world’s urban land and half of that in the United States is devoted to roads, parking lots, gasoline stations, and other automobile-related uses. This prompted urban expert Lewis Mumford to suggest that the U.S. national flower should be the concrete cloverleaf. Another problem is congestion. If current trends continue, U.S. motorists will spend an average of 2 years of their lives in traffic jams, as streets and freeways often resemble parking lots. According to a 2008 report by the American Society of Civil Engineers, about 45% of all major urban U.S. highways are regularly congested. Traffic congestion in some cities in less-developed countries is much worse.
Reducing Automobile Use Is Not Easy, but It Can Be Done Some environmental scientists and economists suggest that we can reduce the harmful effects of automobile use by making drivers pay directly for most of the environmental and health costs caused by their automobile use—a user-pays approach, based on honest environmental accounting. One way to phase in such full-cost pricing would be to charge a tax or fee on gasoline to cover the estimated harmful costs of driving. According to a study by the International Center for Technology Assessment, such a tax would amount to about $3.18 per liter ($12 per gallon) of gasoline in the United States. Gradually phasing in such a tax, as has been done in many European nations, would spur the use of more energyefficient motor vehicles and mass transit, decrease dependence on imported oil, and thus increase economic and national security. It would also reduce pollution and environmental degradation and help to slow projected climate disruption. CONCEPT 13-2
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Proponents of this approach urge governments to fund programs to educate people about the hidden costs they are paying for gasoline. They also argue for using gasoline tax revenues to help finance mass transit systems, bike lanes, and sidewalks as alternatives to cars, and to reduce taxes on income, wages, and wealth to offset the increased taxes on gasoline. Such a tax shift would help to make higher gasoline taxes more politically and economically acceptable. Taxing gasoline heavily would be difficult in the United States, for three reasons. First, it faces strong opposition from two groups, one being the many consumers who are largely unaware of the huge hidden costs they are paying for gasoline. The other group is made up of the powerful politically influential transportation-related industries such as carmakers, oil and tire companies, road builders, and many real estate developers. Second, the dispersed nature of most U.S. urban areas makes people dependent on cars. Third, fast, efficient, reliable, and affordable mass transit options, bike lanes, and sidewalks are not widely available in the United States. Another way to reduce automobile use and urban congestion is to raise parking fees and charge tolls on roads, tunnels, and bridges leading into cities—especially during peak traffic times. Also, more than 300 cities in Germany, Austria, Italy, Switzerland, and the Netherlands have car-sharing networks. Members reserve a car in advance or call the network and are directed to the closest car. They are billed monthly for the time they use a car and the distance they travel. In Berlin,
Trade-Offs
Germany, car sharing has cut car ownership by 75%. According to the Worldwatch Institute, car sharing in Europe has reduced the average driver’s CO2 emissions by 40–50%. Car-share companies have sprouted up in the United States in cities such as Madison, Wisconsin, Portland, Oregon, New York, New York, and Los Angeles, California, among others. There are several other alternatives to driving a motor vehicle regularly, each of which has its own advantages and disadvantages. Four widely used alternatives are the bicycle (Figure 13-6), mass transit rail systems in urban areas (Figure 13-7), bus systems in urban areas (Figure 13-8), and rapid-rail systems between urban areas (Figure 13-9).
Trade-Offs Mass Transit Rail A d vant ag es
D i s a d v a nt a g e s
Uses less energy and produces less air pollution than cars do
Expensive to build and maintain Cost-effective only along a densely populated corridor
Use less land than roads and parking lots use Causes fewer injuries and deaths than cars
Commits riders to transportation schedules
Figure 13-7 Mass transit rail systems in urban areas have advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Bicycles A d v a nta g e s
D i sad v antag e s
Are quiet and non-polluting
Provide little protection in an accident
Buses Ad vant ag es
D i s a d v a nt a g e s Can lose money because they require affordable fares
Take few resources to make
Provide no protection from bad weather
Reduce car use and air pollution
Burn no fossil fuels
Are impractical for long trips
Can be rerouted as needed
Require little parking space
Secure bike parking not yet widespread
Cheaper than heavy-rail system
Figure 13-6 Bicycle use has advantages and disadvantages. The key to increasing bicycle use is the creation of bicycle-friendly systems, including bike lanes. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
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Trade-Offs
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Can get caught in traffic and add to noise and pollution Commit riders to transportation schedules
Figure 13-8 Bus rapid-transit systems and conventional bus systems in urban areas have advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Urbanization and Solid and Hazardous Waste
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Trade-Offs Rapid Rail Adva nta ge s
Disad vant ag es
Much more energy efficient per rider than cars and planes are
Costly to run and maintain
Less air pollution than cars and planes
Causes noise and vibration for nearby residents
Can reduce need for air travel, cars, roads, and parking areas
Adds some risk of collision at car crossings
Figure 13-9 Rapid-rail systems between urban areas have advantages and disadvantages. Western Europe and Japan have highspeed bullet trains that travel between cities at up to 306 kilometers (190 miles) per hour. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
13-3 How Can Cities Become
More Sustainable and Livable? ▲
CONC EPT 13-3A Urban land-use planning can help to reduce uncontrolled sprawl and slow the resulting degradation of air, water, land, biodiversity, and other natural resources.
▲
CONC EPT 13-3B An ecocity allows people to choose walking, biking, or mass transit for most transportation needs; to recycle or reuse most of their wastes; to grow much of their food; and to protect biodiversity by preserving surrounding land.
Smart Growth Works Most urban and some rural areas use some form of land-use planning to determine the best present and future use of each parcel of land. Much land-use planning encourages future population growth and economic development, regardless of the environmental and social consequences, and such planning typically leads to urban sprawl. One way to encourage more environmentally sustainable development with less dependence on cars, more controls on sprawl, and reduction of wasteful resource use is to employ smart growth. It is a form of planning that recognizes that urban growth will occur. At the same time, it uses laws and other tools (Figure 13-10, p. 284) to channel growth into areas where it can cause less harm (Concept 13-3A). Some communities are going further and using the goals of new urbanism to develop entire villages and promote mixed-use neighborhoods within existing cities. These goals include: •
walkability, with most stores and recreational activities located within a 10-minute walk of most homes.
•
mixed-use and diversity, which provides a blend of pedestrian-friendly shops, offices, apartments, and homes to encourage people of different ages, classes, cultures, and races to move into the villages.
•
quality urban design, emphasizing beauty, aesthetics, and architectural diversity.
•
environmental sustainability based on development with minimal environmental impact.
•
smart transportation, with well-designed train and bus systems connecting neighborhoods, towns, and cities.
The Ecocity Concept: Cities Built for People, Not for Cars According to most environmentalists and urban planners, the primary problem with large cities is not urban growth but our failure to make them more sustainable and livable. These same environmentalists and planners call for us to make new and existing urban areas more self-reliant, sustainable, and enjoyable places to live through good ecological design.
CONCEPTS 13-3A AND 13-3B Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
283
Figure 13-10 We can use these smart growth or new urbanism tools to prevent and control urban growth and sprawl. Questions: Which five of these tools do you think would be the best methods for preventing or controlling urban sprawl? Which, if any, of these tools are used in your community?
Solutions Smart Growth Tools Limits and Regulations
Protection Preserve open space
Limit building permits
Buy new open space Prohibit certain types of development
Draw urban growth boundaries
Taxes
Create greenbelts around cities
Tax land, not buildings Tax land on value of actual use instead of on highest value as developed land
Zoning Promote mixed use of housing and small businesses
Tax Breaks For owners agreeing not to allow certain types of development
Concentrate development along mass transportation routes
For cleaning up and developing abandoned urban sites
Planning Ecological land-use planning
Revitalization and New Growth Revitalize existing towns and cities
Environmental impact analysis Integrated regional planning
Build well-planned new towns and villages within cities
New urbanism is a step in the right direction, but we can go further by creating more environmentally sustainable cities, called ecocities or green cities, which emphasize the following practices built around the three principles of sustainability (see back cover):
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•
Use solar and other locally available renewable energy resources.
•
Design buildings to be heated and cooled as much as possible by natural processes.
•
Use energy and matter resources efficiently.
•
Prevent pollution and reduce waste.
•
Reuse, recycle, and compost as much municipal solid waste as possible.
•
Protect and encourage biodiversity by preserving undeveloped land and protecting and restoring natural systems and wetlands.
•
Promote urban gardens, farmers markets, and community-supported agriculture.
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An ecocity is a people-oriented city, not a caroriented city. Its residents are able to walk, bike, or use low-polluting mass transit for most of their travel. Trees and plants that are adapted to the local climate and soils are planted throughout the city to provide shade, beauty, and wildlife habitats, and to reduce air pollution, noise, and soil erosion. Small organic gardens and a variety of plants adapted to local climate conditions often replace monoculture grass lawns. In an ecocity, abandoned lots and industrial sites are cleaned up, restored, and put to new uses. People work on cleaning up and restoring polluted creeks and rivers, and on preserving urban-area forests, grasslands, wetlands, and farms. Parks are easily available to everyone. In an ecocity, much of the food that people eat comes from nearby organic farms, solar greenhouses, community gardens, and small gardens on rooftops, in yards, and in windows boxes. Finally, an ecocity provides plenty of educational opportunities for its residents by teaching them about environmental problems and solutions (Concept 13-3B). This may sound like a futuristic dream, but GOOD ecocities are real, and one example is the city of NEWS Curitiba, Brazil (see the Case Study that follows). Other examples of cities that have attempted to become more like an ideal ecocity are Bogota, Colombia; Waitakere City, New Zealand; Stockholm, Sweden; Leicester, England; and in the United States, Portland, Oregon; Davis, California; and Chattanooga, Tennessee. Globally, Sweden is leading the way with 70 “ecomunicipalities.” China is also planning to develop model ecocities. In fact, despite the environmental problems plaguing cities, there are dozens of examples of cities and villages around the world that are striving to become environmentally sustainable. While cities can magnify environmental problems, they can also gather people with the energy and imagination needed to solve some of those problems. ■ C AS E S T UDY
Curitiba Strives to Be an Ecocity Curitiba (“koor-i-TEE-ba”), known as the “ecological capital” of Brazil, is a city of 3.2 million people. In 1969, planners in this city decided to focus on an inexpensive and efficient mass transit system rather than on the car. Curitiba now has the world’s best bus system, in which clean and modern buses transport about 72% of all commuters every day throughout the city using express lanes dedicated to buses. Only high-rise apartment buildings are allowed near major bus routes, and each building must devote its bottom two floors to stores—a practice that reduces the need for residents to travel. Cars have been banned from 49 blocks in the center of the downtown area, which has a network of pedestrian walkways connected to bus stations, parks, and bicycle paths running throughout most of the city. Consequently, Curitiba uses less energy per person and has
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lower emissions of greenhouse gases and other air pollutants, as well as less traffic congestion than do most comparable cities. The city transformed flood-prone areas along its six rivers into a series of interconnected parks. Volunteers have planted more than 1.5 million trees throughout the city, none of which can be cut down without a permit, which also requires that two trees must be planted for each one that is cut down. Curitiba recycles roughly 70% of its paper and 60% of its metal, glass, and plastic, which is collected from households three times a week. Recovered materials are sold mostly to the city’s more than 500 major industries, which must meet strict pollution standards. Most of these businesses are located in an industrial park outside the city limits. A major bus line runs to the park, but many of the workers live nearby and can walk or bike to work. The city uses old buses as roving classrooms to give the poor basic skills needed for jobs. Other retired buses
have become school classrooms, health clinics, soup kitchens, and day care centers, which are open 11 hours a day and are free for low-income parents. The poor receive free medical and dental care, child care, and job training, and 40 feeding centers are available for street children. Poor people can collect garbage and exchange filled garbage bags for surplus food, bus tokens, and school supplies. Also, the city has a build-ityourself program that gives a poor family a plot of land, building materials, two trees, and an hour’s consultation with an architect. This internationally acclaimed model of urban planning and sustainability is the brainchild of architect and former college professor Jaime Lerner, who has served as the city’s mayor three times since 1969. Curitiba now faces new challenges, as do all cities, mostly because of increasing population pressure. But Lerner believes that by continuing to apply strategies that have made Curitiba a model ecocity, Curitiba’s leaders and residents can find solutions to these problems.
13-4 What Are Solid Waste and Hazardous Waste,
and Why Are They Problems? ▲
CONC EPT 13-4 Solid waste contributes to pollution and represents the unnecessary consumption of resources; hazardous waste contributes to pollution, natural capital degradation, and human health problems.
We Throw Away Huge Amounts of Useful Things and Hazardous Materials In the natural world, there is essentially no waste because the wastes of one organism become nutrients for others (see Figure 2-13, p. 36). This is in keeping with one of the three principles of sustainability (see back cover). On the other hand, modern humans produce huge amounts of waste material (see Case Study that follows). One major category of waste is solid waste—any unwanted or discarded material we produce that is not a liquid or a gas. We can divide solid waste into two types. One type is industrial solid waste produced by mines, farms, and industries that supply people with goods and services. The other is municipal solid waste (MSW), often called garbage or trash, which consists of the combined solid waste produced by homes and workplaces other than factories. The other major category of waste is hazardous, or toxic, waste that threatens human health or the environment because it is poisonous, dangerously chemically reactive, corrosive, or flammable. The two largest
classes of hazardous wastes are organic compounds (such as various solvents, pesticides, PCBs, and dioxins) and toxic heavy metals (such as lead, mercury, and arsenic). Examples of hazardous waste include industrial solvents, hospital medical waste, car batteries (containing lead and acids), household pesticide products, drycell batteries (containing mercury and cadmium), and incinerator ash. Figure 13-11 (p. 286) lists some of the harmful chemicals found in many homes. There are two reasons for sharply reducing the amount of solid and hazardous wastes we produce. One reason is that at least three-fourths of these materials represent an unnecessary waste of the earth’s resources. The second reason is that, in producing the products we use and often discard, we create huge amounts of air pollution, greenhouse gases, water pollution, and land degradation (Concept 13-4). ■ C AS E S T UDY
Solid Waste in the United States The United States leads the world in producing solid waste. With only 4.6% of the world’s population, the United States produces about one-third of the world’s
CONCEPT 13-4 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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What Harmful Chemicals Are in Your Home? Gardening
Cleaning Disinfectants
Pesticides
Drain, toilet, and window cleaners
Weed killers
Spot removers
Ant and rodent killers Flea powders
• •
about 24 million rolls of toilet paper a day
•
about 2.5 million nonreturnable plastic bottles every hour
•
about 274 million plastic shopping bags per day, an average of nearly 3,200 every second
•
about 25 million metric tons (27 million tons) of edible food per year
•
enough office paper each year to build a wall 3.5 meters (11 feet) high across the country from New York City to San Francisco, California
•
some 186 billion pieces of junk mail (an average of 660 pieces per American) each year, about 45% of which are thrown away unopened
Septic tank cleaners
Paint Products Paints, stains, varnishes, and lacquers Paint thinners, solvents, and strippers Wood preservatives Artist paints and inks
Automotive Gasoline Used motor oil Antifreeze
General Dry-cell batteries (mercury and cadmium) Glues and cements
Battery acid Brake and transmission fluid
Figure 13-11 Harmful chemicals are found in many homes. The U.S. Congress has exempted disposal of most of these materials from government regulation. Question: Which of these chemicals, if any, are in your home?
solid waste. About 98.5% of all solid waste produced in the United States is industrial solid waste from mining, agriculture, and industry. The remaining 1.5% of U.S. solid waste is municipal solid waste (MSW), the largest categories of which are paper and cardboard (31% of total U.S. MSW), yard waste (13%), food waste (13%), plastics (12%), and metals (8%). This 1.5% of the overall U.S. solid waste problem is still huge. The United States also leads the world in trash production (by weight) per person, followed by Canada. Each day, the average American produces more than 2.0 kilograms (4.5 pounds) of MSW; two-thirds of it is dumped into landfills or incinerated. That is about twice the amount of solid waste per person produced in other industrial countries such as Japan and Germany, and 5–10 times the amount produced in most lessdeveloped countries. Every year, the United States generates enough MSW to fill a bumper-to-bumper convoy of garbage trucks encircling the globe almost eight times. Consider some of the solid wastes that consumers throw away in the high-waste economy of the United States:
286
•
enough tires each year to encircle the planet almost three times
•
an amount of disposable diapers each year that, if linked end to end, would reach to the moon and back seven times
CHAPTER 13
enough carpeting every year to cover the U.S. state of Delaware
Some encouraging news is that since 1990, GOOD the average weight of MSW per American has NEWS leveled off, mostly because of increased recycling and the use of lighter-weight products, and also because of reduced product packaging overall.
Electronic Waste Is a Growing Problem Electronic waste, or e-waste, consists of discarded television sets, cell phones, computers, and other electronic devices. It is the fastest-growing solid waste problem in the United States and in the world. Every year, Americans discard an estimated 155 million cell phones, 48 million personal computers, and many more millions of television sets and other electronic products. Most e-waste ends up in landfills and incinerators, but much of it is shipped to China, India, and poor African nations where labor is cheap and environmental regulations are weak. Workers there—many of them children—dismantle, burn, and treat e-waste products with acids to recover valuable metals and reusable parts. As they do this, they are exposed to toxic metals and other harmful chemicals. The remaining scrap is often dumped into waterways and fields or burned in open fires, exposing many more people to highly toxic chemicals called dioxins. The transferring of such hazardous waste from moredeveloped to less-developed countries was banned by the International Basel Convention, a treaty now signed by 172 countries, but not by the United States. Despite this ban, much e-waste is not officially classified as hazardous waste or is illegally smuggled into China and other countries. The European Union (EU) has led the way in dealing with e-waste. It requires manufacturers to take back electronic products at the end of their useful lives for repair or recycling, and e-waste is banned from landfills and incinerators. Japan has also adopted such a cradleto-grave approach to handling e-waste. Some electronics manufacturers in the United States offer free recycling programs to their customers.
Urbanization and Solid and Hazardous Waste
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13-5 How Should We Deal with Solid Waste? ▲
CONC EPT 13-5A A sustainable approach to solid waste is first to reduce it, then to reuse or recycle it, and finally to safely dispose of what is left.
▲
CONC EPT 13-5B Technologies for burning and burying solid wastes are well developed, but burning contributes to pollution and greenhouse gas emissions, and buried wastes eventually contribute to the pollution and degradation of land and water resources.
We Can Burn or Bury Solid Waste or Produce Less of It
We Can Cut Solid Wastes by Reducing, Reusing, and Recycling
We can deal with the solid wastes we create in two ways. One is waste management, in which we attempt to reduce the environmental impact of MSW without seriously trying to reduce the amount of waste we produce. It typically involves mixing wastes together and then transferring them from one part of the environment to another, usually by burying them, burning them, or shipping them to another location. The second approach is waste reduction, in which we produce much less waste and pollution, and the wastes we do produce are considered to be potential resources that we can reuse, recycle, or compost (Concept 13-5A). With this approach, we can think of trash cans and garbage trucks as resource containers that carry materials to recycling or composting facilities. There is no single solution to the solid waste problem. Most analysts call for using integrated waste management—a variety of strategies for both waste management and waste reduction (Figure 13-12). Some scientists and economists estimate that we could reduce 75–90% of the solid waste we produce by a combination of the strategies shown in Figure 13-12. Let us look more closely at these options in the order of priorities suggested by scientists.
Waste reduction (Concept 13-5A) is based on three Rs: reduce, reuse, and recycle. Figure 13-13 (p. 288) lists some ways in which you can use the three Rs to reduce your output of solid waste. Here are six strategies that industries and communities can use to reduce resource use, waste, and pollution: First, redesign manufacturing processes and products to use less material and energy. For example, the weight of a typical car has been reduced by about one-fourth since the 1960s through use of lighter steel and lightweight plastics and composite materials. Second, develop products that are easy to repair, reuse, remanufacture, compost, or recycle. A Xerox photocopier made of reusable or recyclable parts that allow for easy remanufacturing could eventually save the company $1 billion in manufacturing costs. Third, eliminate or reduce unnecessary packaging. Use the following hierarchy for product packaging: no packaging, reusable packaging, and recyclable packaging. Fourth, use fee-per-bag waste collection systems that charge consumers for the amount of waste they throw away, but provide free pickup of recyclable and reusable items.
First Priority
Second Priority
Last Priority
Primary Pollution and Waste Prevention
Secondary Pollution and Waste Prevention
Waste Management
Change industrial process to eliminate use of harmful chemicals Use less of a harmful product Reduce packaging and materials in products Make products that last longer and are recyclable, reusable, or easy to repair
Reuse
Treat waste to reduce toxicity
Repair
Incinerate waste
Recycle
Bury waste in landfills
Compost
Release waste into environment for dispersal or dilution
Buy reusable and recyclable products
Figure 13-12 Integrated waste management: The U.S. National Academy of Sciences suggests these priorities for dealing with solid waste. To date, these waste-reduction priorities have not been followed in the United States or in most other countries. Instead, most efforts are devoted to waste management through disposal (bury it, burn it, or send it somewhere else). Question: Why do you think most countries do not follow these priorities, even though they are based on reliable science? (Data from U.S. Environmental Protection Agency and U.S. National Academy of Sciences)
CONCEPTS 13-5A AND 13-5B Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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What Can You Do? Solid Waste ■
Follow the three Rs of resource use: Reduce, Reuse, and Recycle
■
Ask yourself whether you really need a particular item, and refuse packaging where possible
■
Rent, borrow, or barter goods and services when you can, buy secondhand, and donate or sell unused items
■
Buy things that are reusable, recyclable, or compostable, and be sure to reuse, recycle, and compost them
■
Avoid disposables and do not use throwaway paper and plastic plates, cups, eating utensils, and other disposable items when reusable or refillable versions are available
■
Use e-mail or text-messaging in place of conventional paper mail
■
Read newspapers and magazines online and read e-books
■
Buy products in bulk or concentrated form whenever possible
Figure 13-13 Individuals matter: You can save resources by reducing your output of solid waste and pollution. Questions: Which three of these actions do you think are the most important? Why? Which of these things do you already do?
Fifth, establish cradle-to-grave responsibility laws that require companies to take back various consumer products such as electronic equipment, appliances, and motor vehicles, as Japan and many European countries do. Sixth, restructure urban transportation systems to rely more on mass transit and bicycles than on cars.
Reuse Is an Important Way to Reduce Solid Waste and Pollution and Save Money In today’s modern societies, we have increasingly substituted throwaway items for reusable ones. For example, if the 1 billion throwaway paper coffee cups used by one famous chain of donut shops each year were lined up end-to-end, they would encircle the earth two times. Rewarding customers who bring their own refillable coffee mugs by discounting the price of their coffee helps to reduce this waste in the many coffee shops that now do this. Reuse involves cleaning and using materials over and over, and thus increasing the typical life span of a product (see the Case Study that follows). This form of waste reduction decreases the use of matter and energy resources, cuts waste and pollution (including greenhouse gases), creates local jobs, and saves money. Traditional forms of reuse include salvaging automobile parts from older cars in junkyards and recovering materials from old houses and buildings. Other reuse strategies
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involve yard sales, flea markets, secondhand stores, auctions, and classified newspaper ads. The Internet has brought online auctions and sites such as www .freecycle.org, which links people who want to give away household belongings free to people in their area who may want or need them. Reuse is alive and well in many less-developed countries. But reuse has a downside, as poor people who scavenge in open dumps for items that they can reuse or sell are often exposed to toxins and infectious diseases.
■ C AS E S T UDY
We Can Use Refillable Containers and Other Items Two examples of reusable items are refillable glass beverage bottles and refillable soft drink bottles made of polyethylene terephthalate (PET) plastic. Typically, such bottles make 15 refilling round-trips before they become too damaged for reuse and are then recycled. Reusing these containers saves energy while reducing CO2 emissions, air pollution, water pollution, and solid wastes, and it stimulates local economies by creating local jobs related to the collection and refilling of containers. But big companies make more money by producing and shipping throwaway beverage and food containers from centralized facilities. This has contributed to the demise of many small, local bottling companies, breweries, and dairies that had collected and reused most of their containers, and it hurt local economies. Some Canadian provinces and ten U.S. states have bottle laws that place a deposit fee on all beverage containers. Consumers can get the fee refunded when they return the bottle. Retailers must accept the used containers and pass them on for recycling or reuse. Experience with such an approach shows that more jobs are gained than lost, consumers’ costs have not risen, resources are saved, and both roadside litter and the amount of solid waste arriving at landfills decreases. Reuse is on the rise. Denmark, Finland, and GOOD the Canadian province of Prince Edward Island NEWS have banned all beverage containers that cannot be reused. In Finland, 95% of the soft drink, beer, wine, and spirits containers are refillable. Instead of using paper or plastic bags to carry groceries and other items, many people have switched to reusable cloth bags. Both paper and plastic bags are environmentally harmful, and the question of which is more damaging has no clear-cut answer. To encourage this trend, the governments of Ireland, Taiwan, and the Netherlands put a tax on plastic shopping bags. In Ireland, the tax helped to cut plastic bag litter by 90%. Bangladesh, Taiwan, Rwanda, South Africa, Uganda, China, Australia, and several other countries, plus the U.S. city of San Francisco, have banned the use of all or most types of plastic shopping bags.
Urbanization and Solid and Hazardous Waste
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
HOW WOULD YOU VOTE?
✓ ■
What Can You Do?
Should consumers have to pay for plastic or paper bags at grocery stores and other outlets? Cast your vote online at www.cengage.com/login.
There are many other ways to reuse various items, some of which are listed in Figure 13-14.
GOOD NEWS
Reuse ■
Buy beverages in refillable glass containers instead of cans or throwaway bottles
■
Use reusable plastic or metal lunchboxes
■
Carry sandwiches and store refrigerated food in reusable containers instead of wrapping them in aluminum foil or plastic wrap
■
Use rechargeable batteries and recycle them when their useful life is over
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When eating out, bring your own reusable silverware and napkin
■
Bring your own reusable container for takeout food or restaurant meal leftovers
■
Carry groceries and other items in a reusable basket or cloth bag
■
Buy used furniture, computers, cars, and other items instead of buying new
■
Give away or sell items you no longer use
There Are Two Types of Recycling Recycling involves reprocessing discarded solid materials into new, useful products. Households and workplaces produce five major types of recyclable materials: paper products, glass, aluminum, steel, and some plastics (see Case Study, p. 290). We can reprocess such materials in two ways. In primary, or closed-loop, recycling, materials such as aluminum cans are recycled into new products of the same type. In secondary recycling, waste materials are converted into different products. For example, we can shred used tires and turn them into rubberized road surfacing material. Scientists distinguish between two types of recyclable wastes: preconsumer waste generated in a manufacturing process, and postconsumer waste generated by consumers’ use of products. Preconsumer waste makes up more than three-fourths of the total. Just about anything (except energy) is recyclable, but there are two key questions. First, do the items that are separated for recycling actually get recycled? Second, do businesses, governments, and individuals complete the recycling loop by buying products that are made from recycled materials? The United States now recycles about 25% of GOOD its MSW—up from 6.4% in 1960. This increase NEWS has received a boost by almost 9,000 curbside-pickup recycling programs that serve about half of the U.S. population. Recycling rates vary with different waste items and include 88% for newsprint, 45% for aluminum drink cans, 31% for PET plastic soft drink bottles, and 21% for glass bottles and jars. Experts say that with education and proper incentives, the United States could recycle 60–75% of its MSW, in keeping with the chemical recycling principle of sustainability.
We Can Mix or Separate Household Solid Wastes for Recycling One way to recycle is to send mixed household and business wastes to centralized materials-recovery facilities (MRFs). There, machines or workers separate the mixed wastes to recover valuable materials for sale to manufacturers as raw materials. The remaining paper, plastics, and other combustible wastes are recycled or burned to produce steam or electricity, which is used to run the recovery plant or sold to nearby industries or homes.
Figure 13-14 Individuals matter: There are many ways to reuse the items we purchase. Question: Which of these suggestions have you tried and how did they work for you?
Such plants are expensive to build, operate, and maintain. If not operated properly, they can emit CO2 and toxic air pollutants, and they produce a toxic ash that must be disposed of safely, usually in landfills. Because MRFs require a steady diet of garbage to make them financially successful, their owners have a vested interest in increasing the throughput of matter and energy resources. Thus, use of MRFs encourages people to produce more trash—the reverse of what many scientists believe we should be doing (Figure 13-12). To many experts, it makes more environmental and economic sense for households and businesses to separate their trash into recyclable categories such as glass, paper, metals, certain types of plastics, and compostable materials. This source separation approach produces much less air and water pollution, and costs less to implement than does building and operating MRFs. It also saves more energy, provides more jobs per unit of material, and yields cleaner and usually more valuable recyclables. To promote separation of wastes for recycling, more than 4,000 communities in the United States use a payas-you-throw (PAUT) or fee-per-bag waste collection system. They charge households and businesses for the amount of mixed waste picked up, but they do not charge for pickup of materials separated for recycling or reuse. When the U.S. city of Fort Worth, Texas, instituted such a program, the proportion of households recycling their trash went from 21% to 85%.
CONCEPTS 13-5A AND 13-5B Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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HOW WOULD YOU VOTE?
✓ ■
Should households and businesses be charged for the amount of mixed waste they generate for pickup, but not for pickup of the materials they separate for recycling? Cast your vote online at www.cengage.com/login.
making plastic resins is so low that the cost of virgin plastic resins is much lower than that of recycled resins. An exception is PET (polyethylene terephthalate), used mostly in plastic drink bottles. However, progress is being made in the recycling of plastics and in the development of more degradable bioplastics (Science Focus, below).
■ CAS E STUDY
Recycling Plastics Plastics consist of various types of large polymers, or resins—organic molecules made of combinations of organic chemicals produced mostly from oil and natural gas. About 46 different types of plastics are used in consumer products, and some products contain several kinds of plastic. Many plastic containers and other items are thrown away and end up as litter on roadsides and beaches. Each year, they threaten terrestrial animal species as well as millions of seabirds, marine mammals, and sea turtles, which can mistake a floating plastic sandwich bag for a jellyfish—a major food source for them. About 80% of the plastics in the ocean are blown or washed in from beaches, rivers, and storm drains, and the rest get dumped into the ocean from ships, fishing boats, and garbage barges. Currently, only about 4% by weight of all plastic wastes in the United States is recycled. There are three reasons for this low percentage. First, many plastics are hard to isolate from other wastes because the many different resins used to make them are often difficult to identify, and some plastics are composites of different resins. Most plastics also contain stabilizers and other chemicals that must be removed before recycling. Second, recovering individual plastic resins does not yield much material because only small amounts of any given resin are used per product. Third, the inflationadjusted price of oil used to produce petrochemicals for
We Can Copy Nature and Recycle Biodegradable Solid Wastes Composting is a form of recycling that mimics nature’s recycling of nutrients—one of the three principles of sustainability (see back cover). It involves using decomposer bacteria to recycle yard trimmings, vegetable food scraps, and other biodegradable organic wastes. Then we can add the resulting organic material to soil to supply plant nutrients, slow soil erosion, retain water, and improve crop yields. Homeowners can compost such wastes in simple backyard containers and in composting piles that they must turn over occasionally to aerate the compost and speed decomposition. Some cities in Canada and in many European Union countries collect and compost more than 85% of their biodegradable wastes in centralized community facilities. The United States has about 3,300 municipal composting programs that recycle about 37% of the country’s yard wastes. In 2009, San Francisco, California, became the first U.S. city to mandate composting as part of its goal to eliminate the dumping of MSW into landfills by 2020. The resulting compost can be used as organic soil fertilizer, topsoil, or landfill cover. It can also be used to help restore eroded soil on hillsides and along highways, as well as on strip-mined land, overgrazed areas, and eroded cropland.
SCIE N C E FO C US Bioplastics
T
he search for biologically based plastics dates from 1913, when a French scientist and a British scientist each filed for patents on a soy-based plastic. At that time, there was intense competition between the petrochemical and agricultural industries to dominate the market for plastics made from organic polymers. But as oil became widely available, petrochemical plastics took over the market. Now, with climate change and other environmental problems associated with the use of oil, chemists are stepping up efforts to make
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biodegradable and more environmentally sustainable plastics from a variety of green polymers. These bioplastics can be made from corn, soy, sugarcane, switchgrass, chicken feathers, and some components of garbage. The key to making such biopolymers is to find chemicals called catalysts that speed up the reactions that form polymers from biologically based chemicals without the use of high-temperature heat. With proper design and mass production, bioplastics could be lighter, stronger, and cheaper compared to conventional oil-based plastics, and the
process of making them would require less energy and produce less pollution per unit of weight. Instead of being sent to landfills, packaging made from bioplastics could be composted to produce a soil conditioner, in keeping with the chemical recycling principle of sustainability (see back cover). Critical Thinking What might be some disadvantages of more rapidly degradable bioplastics? Do you think they outweigh the advantages? Why?
Urbanization and Solid and Hazardous Waste
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Trade-Offs
Figure 13-15 Recycling solid waste has advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Recycling Adva nta ge s
Disad vant ag es
Reduces energy and mineral use and air and water pollution
Can cost more than burying in areas with ample landfill space
Reduces greenhouse gas emissions
Reduces profits for landfill and incinerator owners
Reduces solid waste Can save landfill space
Source separation inconvenient for some
Recycling Has Advantages and Disadvantages Figure 13-15 lists the advantages and disadvantages of recycling. Whether recycling makes economic sense depends on how you look at its economic and environmental benefits and costs. Critics of recycling programs argue that recycling is costly and adds to the taxpayer burden in communities where recycling is funded through taxation. Proponents of recycling argue that the U.S. recycling industry employs about 1.1 million people and that its annual revenues are much larger than those of the waste management industry, which is also financed through taxation in most communities. They also point to studies showing that the net economic, health, and environmental benefits of recycling (Figure 13-15, left) far outweigh the costs.
We Can Encourage Reuse and Recycling Three factors hinder reuse and recycling. First, the market prices of almost all products do not include the harmful environmental and health costs associated with producing, using, and discarding them. Second, the economic playing field is uneven, because in most countries, resource-extracting industries receive more government tax breaks and subsidies than reuse and recycling industries get. Third, the demand and thus the price paid for recycled materials fluctuates, mostly because buying goods made with recycled materials is not a priority for most governments, businesses, and individuals. How can we encourage reuse and recycling? Proponents say that leveling the economic playing field is the
best way to start. Governments can increase subsidies and tax breaks for reusing and recycling materials and decrease subsidies and tax breaks for making items from virgin resources. Other strategies are to greatly increase use of the fee-per-bag waste collection system and to encourage or require government purchases of recycled products to help increase the demand for and lower the prices of these products. Governments can also pass laws requiring companies to take back and recycle or reuse packaging and electronic waste discarded by consumers of their products, as has been done in Japan and in some European Union countries. HOW WOULD YOU VOTE?
✓ ■
Should governments pass laws requiring manufacturers to take back and reuse or recycle all packaging waste, appliances, electronic equipment, and motor vehicles at the end of their useful lives? Cast your vote online at www.cengage.com/login.
One reason for the popularity of recycling is that it helps to soothe the consciences of people living in a throwaway society. Many people think that recycling their newspapers and aluminum cans is all they need do to meet their environmental responsibilities. Recycling is important, but reducing resource consumption and reusing resources are more effective prevention approaches to reducing the flow and waste of resources (Concept 13-5A).
Burning Solid Waste Has Advantages and Disadvantages Globally, MSW is burned in more than 600 large wasteto-energy incinerators (98 in the United States), which use the heat generated to boil water and make steam for heating water or space, or for producing electricity. Great Britain burns about 90% of its MSW in incinerators, compared to 13% in the United States and 8% in Canada. Trace the flow of materials through this process, as diagrammed in Figure 13-16 (p. 292). To be economically feasible, incinerators must be fed huge volumes of trash every day. This encourages trash production and discourages reuse, recycling, and waste reduction. Since 1985, more than 280 new incinerator projects have been delayed or canceled in the United States because of high costs, concern over air pollution, and intense citizen opposition. CONCEPTS 13-5A AND 13-5B
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Electricity
Steam
Crane
Smokestack
Turbine Generator
Wet scrubber
Furnace Boiler
Electrostatic precipitator
Waste pit
Water added Conveyor
Bottom ash
Dirty water Fly ash To waste treatment plan
t
Figure 13-16 Solutions: A waste-to-energy incinerator with pollution controls burns mixed solid wastes and recovers some of the energy generated to produce steam to use for heating or to produce electricity. Questions: Would you invest in such a project? Why or why not?
Trade-Offs Waste-to-Energy Incineration
Figure 13-17 lists the advantages and disadvantages of using incinerators to burn solid waste (Concept 13-5B). HOW WOULD YOU VOTE?
✓ ■
Do the advantages of incinerating solid waste outweigh the disadvantages? Cast your vote online at www.cengage .com/login.
A d v a nt a g e s
D i sad v antag e s
Reduces trash volume
Expensive to build
Produces energy
Produces a hazardous waste
Concentrates hazardous substances into ash for burial
Burying Solid Waste Has Advantages and Disadvantages
Emits some CO2 and other air pollutants
Sale of energy reduces cost
Encourages waste production
About 55% by weight of the MSW in the United States is buried in sanitary landfills, compared to 80% in Canada, 15% in Japan, and 12% in Switzerland. There are two types of landfills. Open dumps are essentially fields or holes in the ground where garbage is deposited and sometimes burned. They are rare in more-developed countries, but are widely used near major cities in many less-developed countries. In newer landfills, called sanitary landfills (Figure 13-18), solid wastes are spread out in thin layers, compacted, and covered daily with a fresh layer of clay or plastic foam, which helps keep the material dry and
Figure 13-17 Incinerating solid waste has advantages and disadvantages (Concept 13-5B). These trade-offs also apply to the incineration of hazardous waste. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
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Ash for treatment, disposal in landfill, or use as landfill cover
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Urbanization and Solid and Hazardous Waste
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When landfill is full, layers of soil and clay seal in trash
Topsoil
Electricity generator building
Sand Clay Garbage
Probes to detect methane leaks
Methane storage and compressor building
Methane gas recovery well
Leachate treatment system
Pipes collect explosive methane for use as fuel to generate electricity Leachate storage tank
Compacted solid waste
Leachate pipes
Garbage Sand
Groundwater monitoring well
Leachate pumped up to storage tank for safe disposal
Synthetic liner Groundwater
Sand Clay and plastic lining to prevent leaks; pipes collect leachate from bottom of landfill
Clay Subsoil
Figure 13-18 Solutions: A state-of-the-art sanitary landfill is designed to eliminate or minimize environmental problems that plague older landfills. Since 1997, only modern sanitary landfills have been permitted in the United States. As a result, many small, older landfills have been closed and replaced with larger local or regional landfills. Question: Some experts say that these landfills will eventually develop leaks and could emit toxic liquids. How do you think this could happen?
reduces leakage of contaminated water (leachate) from the landfill. This covering also lessens the risk of fire, decreases odor, and reduces accessibility to vermin. Figure 13-19 lists the advantages and disadvantages of using sanitary landfills to dispose of solid waste (Concept 13-5B). HOW WOULD YOU VOTE?
Leachate monitoring well
Trade-Offs Sanitary Landfills Ad v antag e s
D isa dv a n t a ge s
Low operating costs
Noise, traffic, and dust
Can handle large amounts of waste
Releases greenhouse gases (methane and CO2) unless they are collected
Filled land can be used for other purposes
Output approach that encourages waste production
No shortage of landfill space in many areas
Eventually leaks and can contaminate groundwater
✓ ■
Do the advantages of burying solid waste in sanitary landfills outweigh the disadvantages? Cast your vote online at www.cengage.com/login.
Figure 13-19 Using sanitary landfills to dispose of solid waste has advantages and disadvantages (Concept 13-5B). Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
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13-6 How Should We Deal with Hazardous Waste? ▲
C O NC EPT 13-6 A sustainable approach to hazardous waste is first to produce less of it, then to reuse or recycle it, then to convert it to less hazardous materials, and finally to safely store what is left.
We Can Use Integrated Management of Hazardous Waste Figure 13-20 shows an integrated management approach suggested by the U.S. National Academy of Sciences that establishes three priorities for dealing with hazardous waste: produce less; convert as much of it as possible to less hazardous substances; and put the rest in long-term, safe storage (Concept 13-6). As with solid waste, the top priority should be pollution prevention and waste reduction. With this approach, industries try to find substitutes for toxic or hazardous materials, reuse or recycle the hazardous materials within industrial processes, or use them as raw materials for making other products.
We Can Detoxify Hazardous Wastes The first step in dealing with hazardous wastes is to collect them. In Denmark, all hazardous and toxic waste from industries and households is delivered to any of 21 transfer stations throughout the country. From there it is taken to a large processing facility, where threefourths of the waste is detoxified by physical, chemical, and biological methods. The rest is buried in a carefully designed and monitored landfill. Physical methods include using charcoal or resins to filter out harmful solids, and distilling liquid wastes to separate out harmful chemicals. Especially deadly wastes can be encapsulated in glass, cement, or ceramics and then put in secure storage sites. Chemical methods are used to convert hazardous chemicals to harmless or less harmful chemicals through chemical reactions.
Produce Less Hazardous Waste
Some scientists and engineers consider biological methods for treatment of hazardous waste to be the wave of the future. One such approach is bioremediation, in which bacteria and enzymes help to destroy toxic or hazardous substances, or convert them to harmless compounds. Another approach is phytoremediation, which involves using natural or genetically engineered plants to absorb, filter, and remove contaminants from polluted soil and water. Various plants have been identified as “pollution sponges” that can help to clean up soil and water contaminated with chemicals such as pesticides, organic solvents, and radioactive or toxic metals. Phytoremediation is still being evaluated and is slow (requiring several growing seasons) compared to other alternatives. However, it can be used to help clean up toxic hotspots. We can incinerate hazardous wastes to break them down and convert them to harmless or less harmful chemicals such as carbon dioxide and water. This has the same combination of advantages and disadvantages as does burning solid wastes (Figure 13-16). But incinerating hazardous waste can also release highly toxic air pollutants such as dioxins, and it produces a highly toxic ash that must be safely and permanently stored in a landfill or vault especially designed for this hazardous end product.
We Can Store Some Forms of Hazardous Waste Ideally, we should use land disposal and long-term storage of hazardous wastes only as the third and last resort after we have exhausted the first two priorities
Convert to Less Hazardous or Nonhazardous Substances
Put in Perpetual Storage
Change industrial processes to reduce or eliminate hazardous waste production
Natural decomposition
Landfill
Incineration
Underground injection wells
Recycle and reuse hazardous waste
Thermal treatment
Surface impoundments
Chemical, physical, and biological treatment
Underground salt formations
Dilution in air or water Figure 13-20 Integrated hazardous waste management: The U.S. National Academy of Sciences has suggested these priorities for dealing with hazardous waste (Concept 13-6). To date, these priorities have not been followed in the United States or in most other countries, one exception being Denmark. Question: Why do you think that most countries do not follow these priorities? (Data from U.S. National Academy of Sciences)
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Urbanization and Solid and Hazardous Waste
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Trade-Offs
Figure 13-21 Injecting liquid hazardous wastes into deep underground wells has advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
Deep-Well Disposal Adva nta ge s
Disad vant ag es
Safe if sites are chosen carefully
Leaks from corrosion of well casing
Emits CO2 and other air pollutants
Wastes can often be retrieved
Output approach that encourages waste production
Low cost
(Figure 13-20 and Concept 13-6). But currently, burial on land is the most widely used method in the United States and in most countries. The most common form of burial is deep-well disposal, in which liquid hazardous wastes are pumped under pressure through a pipe into dry, porous rock formations far beneath aquifers that are tapped for drinking and irrigation water. Theoretically, these liquids soak into the porous rock material and are isolated from overlying groundwater by essentially impermeable layers of clay and rock. However, this fairly cheap, out-of-sight and out-ofmind approach presents some problems. There are a limited number of such sites and limited space within them. Sometimes the wastes can leak into groundwater from the well shaft or migrate into groundwater in unexpected ways. In the United States, roughly 64% of liquid hazardous wastes are injected into deep disposal wells. Many scientists believe that current regulations for deep-well disposal in the United States are inadequate and should be improved. Figure 13-21 lists the advantages and disadvantages of deep-well disposal of liquid hazardous wastes.
HOW WOULD YOU VOTE?
✓ ■
Do the advantages of deep-well disposal of hazardous wastes outweigh the disadvantages? Cast your vote online at www .cengage.com/login.
ally all impoundment liners are likely to leak and could contaminate groundwater. HOW WOULD YOU VOTE?
✓ ■
Do the advantages of storing hazardous wastes in surface impoundments outweigh the disadvantages? Cast your vote online at www.cengage.com/login.
There are some highly toxic materials, such as mercury, that we cannot destroy, detoxify, or safely bury. The best way to deal with such materials is to prevent or reduce their use and to put what is produced in metal drums or other containers. These containers are placed aboveground in especially designed storage buildings or underground in salt mines or bedrock caverns where they can be inspected on a regular basis and retrieved if necessary. Sometimes both liquid and solid hazardous wastes are put into drums or other containers and buried in carefully designed and monitored secure hazardous waste landfills (Figure 13-23, p. 296). This is the least-used method because of the expense involved. In the United States, there are only 23 commercial hazardous waste landfills, although the EPA licenses some companies to store their hazardous waste in approved landfill sites. Some more-developed countries are more careless with their hazardous wastes. In some countries, certain hazardous wastes are mixed with household garbage and stored in conventional landfills. Most less-developed
Trade-Offs Surface Impoundments A d vant ag es
D i s a d v a nt a g e s
Low cost
Groundwater contamination from leaking liners (and overflow from flooding)
Wastes can often be retrieved
Air pollution from volatile organic compounds
Surface impoundments are lined ponds, pits, or lagoons in which liquid hazardous wastes are stored. As the water evaporates, the waste settles and becomes more concentrated. Figure 13-22 lists the advantages and disadvantages of this method. EPA studies found that 70% of the storage ponds in the United States have no liners and could threaten groundwater supplies. According to the EPA, eventu-
Can store wastes indefinitely with secure double liners
Output approach that encourages waste production
Figure 13-22 Storing liquid hazardous wastes in surface impoundments has advantages and disadvantages. Questions: Which single advantage and which single disadvantage do you think are the most important? Why?
CONCEPT 13-6 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Bulk waste
Gas vent
Topsoil
Sand
Impervious clay
■ C AS E S T UDY
Plastic cover
Earth Impervious clay cap
Clay cap
Water table Earth Leak detection system
Groundwater
Double leachate collection system
Plastic double liner
Reactive wastes in drums
Groundwater monitoring well
Figure 13-23 Solutions: Hazardous wastes can be isolated and stored in a secure hazardous waste landfill.
countries do little to regulate and control what happens to their hazardous wastes. To most environmental scientists, the best solution to the hazardous waste problem is to produce as little as possible of it in the first place—a prevention approach. Figure 13-24 lists some ways in which you can reduce your output of hazardous waste—the first step in dealing with it.
What Can You Do? Hazardous Waste ■
Avoid using pesticides and other hazardous chemicals, or use them in the smallest amounts possible.
■
Use less harmful and usually cheaper substances instead of commercial chemicals for most household cleaners. For example, use vinegar to polish metals, clean surfaces, and remove stains and mildew; baking soda to clean utensils and to deodorize and remove stains; and borax to remove stains and mildew.
■
Do not dispose of pesticides, paints, solvents, oil, antifreeze, or other hazardous chemicals by flushing them down the toilet, pouring them down the drain, burying them, throwing them into the garbage, or dumping them down storm drains. Instead, use hazardous waste disposal services available in many cities.
Figure 13-24 Individuals matter: You can reduce your output of hazardous wastes (Concept 13-6). Questions: Which two of these measures do you think are the most important? Why?
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Hazardous Waste Regulation in the United States Some of the hazardous waste produced in the United States is regulated under the Resource Conservation and Recovery Act (RCRA, pronounced “RICK-ra”), passed by the U.S. Congress in 1976 and amended in 1984. Under this act, the EPA sets standards for the management of several types of hazardous waste and issues permits to companies that allow them to produce and dispose of a certain amount of those wastes by approved methods. Permit holders must keep track of their wastes and use only EPA-approved disposal facilities. RCRA is a good start, but only about 5% of the hazardous and toxic wastes, including e-waste, produced in the United States is regulated. In most other countries, especially less-developed countries, an even smaller amount of this waste is regulated. In 1980, the U.S. Congress passed the Comprehensive Environmental Response, Compensation, and Liability Act, commonly known as the CERCLA or Superfund program. Its goals are to identify sites where hazardous wastes have contaminated the environment and to clean them up on a priority basis. The worst sites—those that represent an immediate and severe threat to human health— are put on a National Priorities List and scheduled for cleanup by means of EPA-approved methods. In 2009, there were about 1,500 sites on this list, and more than 300 sites had been cleaned up and removed from the list. The Waste Management Research Institute estimates that at least 10,000 sites should be on the priority list and that cleanup of these sites would cost about $1.7 trillion, not including legal fees. This is a glaring example of the economic and environmental value of emphasizing waste reduction and pollution prevention over “end of the pipe” cleanup. The Superfund Act, designed to make polluters pay for cleaning up abandoned hazardous waste sites, greatly reduced the number of illegal dumpsites around the country. It also forced waste producers who were fearful of liability claims to reduce their production of such waste and to recycle or reuse much more of it. However, under pressure from polluters, the U.S. Congress refused to renew the tax on oil and chemical companies that had financed the Superfund legislation after it expired in 1995. The Superfund is now broke, and taxpayers, not polluters, are footing the bill for future cleanups when the responsible parties cannot be found. As a result, the pace of cleanup has slowed. HOW WOULD YOU VOTE?
✓ ■
Should the U.S. Congress reinstate the polluter-pays principle by levying taxes on chemical, oil, mining, and smelting companies to reestablish a fund for cleaning up existing and new Superfund sites? Register your vote online at www.cengage .com/login.
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The U.S. Congress and several state legisla- GOOD tures have also passed laws that encourage the NEWS cleanup of brownfields—abandoned industrial and commercial sites such as factories, junkyards, older landfills,
and gas stations. In most cases, they are contaminated with hazardous wastes. By 2009, more than 42,000 former brownfield sites had been cleaned up and restored in the United States.
13-7 How Can We Make the Transition
to a More Sustainable Low-Waste Society? ▲
Shifting to a low-waste society will require individuals and businesses to reduce resource use and to reuse and recycle more of their wastes at local, national, and global levels.
CONC EPT 13-7
Grassroots Action Has Led to Better Solid and Hazardous Waste Management In the United States, individuals have organized GOOD to prevent the construction of hundreds of incin- NEWS erators, landfills, treatment plants for hazardous and radioactive wastes, and polluting chemical plants in or near their communities. Health risks from incinerators and landfills, when averaged over the entire country, are quite low, but the risks for people living near such facilities are much higher. Manufacturers and waste industry officials point out that something must be done with the toxic and hazardous wastes created in the production of certain goods and services. They contend that even if local citizens adopt a “not in my back yard” (NIMBY) approach, the waste will always end up in someone’s back yard. Many citizens do not accept this argument. To them, the best way to deal with most toxic and hazardous waste is to produce much less of it, as suggested by the U.S. National Academy of Sciences (Figure 13-20). For such materials, they believe that the goal should be “not in anyone’s back yard” (NIABY) or “not on planet Earth” (NOPE), which calls for drastically reducing production of such wastes by emphasizing pollution prevention and using the precautionary principle. Environmental justice is an ideal whereby every person is entitled to protection from environmental hazards regardless of race, gender, age, national origin, income, social class, or any political factor. Studies have shown that a lopsided share of polluting factories, hazardous waste dumps, incinerators, and landfills in the United States are located in communities populated mostly by African Americans, Asian Americans, Latinos, and Native Americans. Studies have also shown that, in general, toxic waste sites in white communities have been cleaned up faster and more completely than have similar sites in African American and Latino communities.
Such environmental discrimination in the United States and in other parts of the world has led to a growing grassroots approach to this problem that is known as the environmental justice movement. Supporters of this group have pressured governments, businesses, and environmental organizations to become aware of environmental injustice and to act to prevent it. They have made some progress toward their goals, but have a long way to go.
International Treaties Have Reduced Hazardous Waste Environmental justice also applies at the international level. For decades, some more-developed countries had been shipping hazardous wastes to less-developed countries. Since 1992, an international treaty known as the Basel Convention has been in effect. It banned the more-developed countries that participate in the treaty from shipping hazardous waste to or through other countries without their permission. By 2009, this agreement had been signed by 175 countries and ratified (formally approved and implemented) by 172 countries. Those nations that signed but did not ratify the convention are the United States, Afghanistan, and Haiti. In 2000, delegates from 122 countries completed a global treaty to regulate the use of 12 widely used persistent organic pollutants (POPs). These toxic and persistent chemicals can accumulate to levels hundreds of thousands of times higher than their levels in the general environment in the fatty tissues of humans and other organisms that occupy high trophic levels in food webs (see Figure 5-11, p. 103). POPs can also be transported long distances by wind and water. The original list of 12 chemicals, called the dirty dozen, includes DDT and 8 other chlorine-containing persistent pesticides, PCBs, dioxins, and furans. The POPs treaty seeks to ban or phase out use of these chemicals and to detoxify or isolate stockpiles of them.
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It allows 25 countries to continue using DDT to combat malaria until safer alternatives are available. The United States has not yet ratified this treaty. Environmental scientists consider the POPs treaty to be an important milestone in international environmental law and pollution prevention because it uses the precautionary principle to manage and reduce the risks of harm from toxic chemicals. This list is expected to grow. In 2000, the Swedish Parliament enacted a law that, by 2020, will ban all chemicals that are persistent in the environment and that can accumulate in living tissue. This law also requires industries to perform risk assessments on the chemicals they use and to show that these chemicals are safe to use, as opposed to requiring the government to show that they are dangerous. In other words, chemicals are assumed to be guilty until proven innocent—the reverse of the current policy in the United States and most other countries. There is strong opposition to this approach in the United States, especially from most of the industries that produce and use potentially dangerous chemicals.
We Can Make the Transition to Low-Waste Societies According to physicist Albert Einstein, “A clever person solves a problem, a wise person avoids it.” To prevent pollution and reduce waste, many environmental scientists argue that we can make a transition to a lowwaste society by understanding and following some key principles: •
Everything is connected.
•
There is no away, as in to throw away, for the wastes we produce.
•
Polluters and producers should pay for the wastes they produce.
•
The best and cheapest ways to deal with solid and hazardous wastes are waste reduction and pollution prevention.
•
We ought to mimic nature by reusing, recycling, or composting most of the municipal solid wastes we produce—treating them as potential resources (see the Case Study that follows).
■ CAS E STUDY
Industrial Ecosystems: Copying Nature An important goal for a more sustainable society is to make its industrial manufacturing processes cleaner and more sustainable by redesigning them to mimic how nature deals with wastes. In nature, because of chemical recycling, the waste outputs of one organism become the nutrient inputs of another organism, so that all of the earth’s nutrients are endlessly recycled.
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One way for industries to mimic nature is to reuse or recycle most of the minerals and chemicals they use, instead of burying or burning them or shipping them somewhere. Another method that industries could use to mimic nature would be for them to interact through resource exchange webs in which the wastes of one manufacturer become the raw materials for another—similar to food webs in natural ecosystems (see Figure 2-16, p. 38). This copying of nature is happening in Kalundborg, Denmark, where an electric power plant and GOOD nearby industries, farms, and homes are collab- NEWS orating to reduce their outputs of waste and pollution and to save money, within what is called an ecoindustrial park, or industrial ecosystem. They exchange waste outputs and convert them into resources, as shown in Figure 13-25. This cuts pollution and waste and reduces the flow of nonrenewable mineral and energy resources through the local economy. Today, more than 40 ecoindustrial parks operate in various places around the world (with 18 of them in the United States), and more are being built or planned—some of them on brownfield sites. These and other industrial forms of biomimicry provide many economic benefits for businesses. By encouraging recycling and pollution prevention, they reduce the costs of managing solid wastes, controlling pollution, and complying with pollution regulations. They also reduce a company’s chances of being sued because of any damages it might cause to people and to the environment. In addition, companies improve the health and safety of workers by reducing their exposure to toxic and hazardous materials, thereby reducing company health insurance costs. Biomimicry also encourages companies to come up with new, environmentally beneficial, and less resourceintensive chemicals, processes, and products that they can sell worldwide. In addition, these companies convey a better image to consumers based on actual results rather than public relations campaigns. Biomimicry involves two major steps. The first is to observe certain changes in nature and to study how natural systems have responded to such changing conditions over many millions of years. The second step is to try to copy or adapt these responses within human systems in order to help us deal with various environmental challenges. In the case of solid and hazardous wastes, the food web serves as a natural model for responding to the growing problem of these wastes, in keeping with the chemical cycling principle of sustainability (see back cover).
Applying the Principles of Sustainability In determining how our cities will grow and develop, we can apply the three principles of sustainability (see back cover). We can rely more on solar
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Sludge
Pharmaceutical plant
Local farmers Sludge
Greenhouses Waste heat
Waste heat
Waste heat Fish farming
Waste heat
Oil refinery
Surplus natural gas
Electric power plant Fly ash
Surplus sulfur
Waste calcium sulfate
Surplus natural gas
Waste heat
Cement manufacturer
Sulfuric acid producer Wallboard factory
Area homes
Figure 13-25 Solutions: This industrial ecosystem in Kalundborg, Denmark, reduces waste production by mimicking a natural ecosystem’s food web. The wastes of one business become the raw materials for another, thus mimicking the way that nature recycles chemicals. Question: Is there an industrial ecosystem near where you live or go to school? If not, think about where and how such a system could be set up in your community.
energy to power cities. We can also think in terms of preserving biodiversity by leaving adequate green space around developing cities, while using other tools of smart growth. And cities can become more sustainable by reusing and recycling more materials, mimicking nature’s nutrient cycling. To accomplish all this, we must make the transition from a high-waste, throwaway mode to a low-waste, reducing-reusing-recycling economy. Such a transition will likewise require applying the three principles of sustainability. Shifting from reliance on fossil fuels and nuclear power (which produces long-lived, hazardous, radioactive wastes) to greater use of renewable solar energy, wind, and flowing water will reduce our outputs of solid and hazardous waste. Reusing and recycling more of what now becomes waste will be an application of nature’s chemical cycling processes.
Here are this chapter’s three big ideas: ■ Most expanding urban areas are unsustainable with their large and growing ecological footprints and high levels of poverty, but most urban areas can be made more sustainable and livable. ■ The order of priorities for dealing with solid and hazardous wastes should be to produce less of them, reuse and recycle as much waste as possible, convert hazardous material to less hazardous material, and safely store or dispose of what is left. ■ We need to view solid wastes as wasted resources and hazardous wastes as materials that we should not be producing in the first place.
A sustainable world will be powered by the sun; constructed from materials that circulate repeatedly; made mobile by trains, buses, and bicycles; populated at sustainable levels; and centered around just, equitable, and tight-knit communities. GARY GARDNER
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REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 275. Distinguish between urbanization and urban growth. Describe two factors that can increase the population of a city. List four trends in global urban growth. Describe four phases of urban growth in the United States. What is urban sprawl? List five undesirable effects of urban sprawl. 2. What are four advantages of urbanization? Describe six disadvantages of urbanization. Define noise pollution. Explain why most cities and urban areas are not sustainable. About how many people in the world live in slums, squatter settlements, and shantytowns? Describe some of the problems faced by the poor who live in urban areas. How can governments reduce these problems? Describe the urban problems of Mexico City, Mexico. 3. Distinguish between compact and dispersed cities and give an example of each. What are the major advantages and disadvantages of using motor vehicles? List two ways to reduce dependence on motor vehicles. Describe the major advantages and disadvantages of relying more on (a) bicycles, (b) mass transit rail systems, (c) buses within urban areas, and (d) rapid-rail systems between urban areas. 4. What is smart growth? List five tools used to promote smart growth. What are five goals of new urbanism? List six practices that describe the ecocity concept. Describe Curitiba’s efforts to be a model ecocity. 5. Define and distinguish among solid waste, municipal solid waste (MSW), industrial solid waste, and hazardous (toxic) waste and give an example of each. Give two reasons for sharply reducing the amount of solid and hazardous waste that we produce. Describe the production of solid waste in the United States and what happens to such waste. Describe the growing problem of e-waste. 6. Distinguish among waste management, waste reduction, and integrated waste management. Describe the priorities that scientists believe we should use for dealing with solid waste. List the 3 Rs and give an example of each. Summarize six strategies that industries and communities can use to apply the 3 Rs. Distinguish between
primary (closed-loop) and secondary recycling and give an example of each. Describe two approaches to recycling household solid wastes. What is a materials recovery facility? What is composting? Describe the recycling of plastics and the problems involved. What are the major advantages and disadvantages of recycling? What are three factors that hinder recycling? 7. What are the major advantages and disadvantages of using incinerators to burn solid and hazardous waste? Distinguish between open dumps and sanitary landfills. What are the major advantages and disadvantages of burying solid waste in sanitary landfills? 8. What priorities do scientists believe we should use in dealing with hazardous waste? What is bioremediation? What is phytoremediation? What are the major advantages and disadvantages of (a) storing liquid hazardous wastes in a deep underground well and (b) in surface impoundments? What is a secure hazardous waste landfill? Describe the regulation of hazardous waste in the United States under the Resource Conservation and Recovery Act and the Comprehensive Environmental Response, Compensation, and Liability, or Superfund, Act. 9. How has grassroots action improved solid and hazardous waste management in the United States? What is environmental justice and how well has it been applied in cleaning up hazardous waste sites in the United States? Describe regulation of hazardous wastes at the global level using the Basel Convention and the treaty to control persistent organic pollutants. List five key principles that could guide efforts to prevent pollution and reduce waste. Describe an industrial ecosystem and summarize its benefits. 10. Describe how we can apply the three principles of sustainability (see back cover) in (a) controlling the growth of cities and in (b) managing solid and hazardous waste.
Note: Key terms are in bold type.
CRITICAL THINKING 1. Do you think that urban sprawl is a problem and something that should be controlled? Develop three arguments to support your answer. Compare your arguments with those of your classmates. 2. Write a brief essay that includes at least three reasons why you (a) enjoy living in a large city, (b) would like to live in a large city, or (c) do not wish to live in a large city. Be
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specific in your reasoning. Compare your essay with those of your classmates. 3. If you own a car or hope to own one, what conditions, if any, would encourage you to rely less on the automobile and to travel to school or work by bicycle, on foot, by mass transit, or by carpool or vanpool? What conditions in your community would make this hard to do?
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4. Find three items you regularly use once and then throw away. Are there other alternative reusable products that you could use in place of these disposable items? Compare the cost of using the disposable option for a year versus the cost of buying the alternatives. 5. Would you oppose having a hazardous waste landfill, waste treatment plant, deep-injection well, or incinerator in your community? Explain. If you oppose these disposal facilities, how do you believe the hazardous waste generated in your community and your state should be managed?
6. How does your school dispose of its solid and hazardous waste? Does it have a recycling program? How well does it work? Does it have a hazardous waste collection system? If so, what does it do with these wastes? List three ways to improve your school’s waste reduction and management system. 7. List two questions you would like to have answered as a result of reading this chapter.
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 13 for many study aids and ideas for further
reading and research. These include flashcards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
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14
Economics, Politics, Worldviews, and Sustainability
Key Questions and Concepts 14-1
How are economic systems related to the biosphere?
14-5
What is environmental policy and how is it made?
Ecological economists and most sustainability experts regard human economic systems as subsystems of the biosphere.
CONCEPT 14-5
Through its policies, a government can help to protect environmental and public interests, and encourage more environmentally sustainable economic development.
CONCEPT 14-1
How can we use economic tools to deal with environmental problems? 14-2
We can use resources more sustainably by including their harmful environmental and health costs in the market prices of goods and services (full-cost pricing); by subsidizing environmentally beneficial goods and services; and by taxing pollution and waste instead of wages and profits.
CONCEPT 14-2
How can reducing poverty help us to deal with environmental problems?
14-3
14-6 How can we improve global environmental security? C O N C E P T 1 4 - 6 Global environmental security is necessary for economic security and is at least as important as national security.
What are some major environmental worldviews?
14-7
Major environmental worldviews differ over which is more important—human needs and wants or the overall health of ecosystems and the biosphere.
CONCEPT 14-7
Reducing poverty can help us to reduce population growth, resource use, and environmental degradation.
CONCEPT 14-3
14-8
How can we make the transition to more environmentally sustainable economies? 14-4
How can we live more sustainably?
C O N C E P T 1 4 - 8 We can live more sustainably by becoming environmentally literate, learning from nature, living more simply and lightly on the earth, and becoming active environmental citizens.
C O N C E P T 1 4 - 4 We can use the three principles of sustainability as well as various economic and environmental strategies to develop more environmentally sustainable economies.
When it is asked how much it will cost to protect the environment, one more question should be asked: How much will it cost our civilization if we do not? GAYLORD NELSON
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Links:
refers to the book’s sustainability theme.
GOOD NEWS
refers to good news about the environmental challenges we face.
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14-1 How Are Economic Systems
Related to the Biosphere? ▲
CONC EPT 14-1 Ecological economists and most sustainability experts regard human economic systems as subsystems of the biosphere.
Economic Systems Are Supported by Three Types of Resources
Inputs (from environment)
An economic system is a social institution through which goods and services are produced, distributed, and consumed to satisfy people’s needs and wants, ideally in the most efficient way possible. Three types of capital, or resources, are used to produce goods and services (Figure 14-1). Natural capital includes resources and services produced by the earth’s natural processes that support all economies and all life. Human capital, or human resources, includes people’s physical and mental talents that provide labor, organizational and management skills, and innovation. Manufactured capital, or manufactured resources, refers to items such as machinery, equipment, and factories made from natural resources with the help of human resources.
Economists Disagree over the Importance of Natural Capital and Whether Economic Growth Is Sustainable Neoclassical economists view the earth’s natural capital as a subset or part of a human economic system, and they assume that the potential for economic growth is essentially unlimited. Most of today’s advanced industrialized countries have high-throughput economies, which attempt to boost economic growth by increasing the flow of matter and energy resources extracted from the environment
+
Natural Capital
High-quality energy
Outputs (into environment) Low-quality energy (heat)
High-waste economy
High-quality matter
Waste and pollution
Figure 14-2 The high-throughput economies of most of the world’s more-developed countries rely on continually increasing the flow of energy and matter resources to increase economic growth. This practice produces valuable goods and services, but it also converts high-quality matter and energy resources into waste, pollution, and low-quality heat, and in the process can deplete or degrade various forms of natural capital that support all life and economies. Question: What are three things you regularly do that add to this throughput of matter and energy?
through their economic systems to produce goods and services (Figure 14-2). These resources flow through economies and end up in planetary sinks (air, water, soil, and organisms), where some pollutants and wastes can accumulate to harmful levels. Ecological economists and some environmental economists disagree with this model. They view human economic systems as subsystems of the biosphere that depend heavily on the earth’s irreplaceable natural resources (Concept 14-1) (Figure 14-3, p. 304). In general, the models of ecological economists are built on three major assumptions: 1. Resources are limited and we should not waste them, and there are no substitutes for most types of natural capital (see Figure 1-3, p. 8).
+
Manufactured Capital
System throughputs
=
Human Capital
Goods and Services
Figure 14-1 In an economic system, we use three types of resources to produce goods and services.
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Solar Capital Goods and services Economic Systems Heat Production Depletion of nonrenewable resources
Natural Capital Natural resources such as air, land, soil, biodiversity, minerals, and energy, and natural services such as air and water purification, nutrient cycling, and climate control
Degradation of renewable resources (used faster than replenished)
Consumption
Pollution and waste (overloading nature’s waste disposal and recycling systems)
R e c y c li n g a n d r e u s e
Figure 14-3 Ecological economists see all human economies as subsystems of the biosphere that depend on natural resources and services provided by the sun and earth. Question: Do you agree or disagree with this model? Explain.
2. We should encourage environmentally beneficial and sustainable forms of economic development, and discourage environmentally harmful and unsustainable forms of economic growth.
•
Use eco-labeling to identify products produced by environmentally sustainable methods, and thus help consumers to make informed choices, thereby increasing the demand for such products.
3. We should include the harmful environmental and health effects of producing economic goods and services in their market prices (full-cost pricing), so that consumers will have more accurate information about the harmful environmental and health effects of the goods and services they buy.
•
Phase out environmentally harmful government subsidies and tax breaks while increasing subsidies and tax breaks for environmentally beneficial goods and service (subsidy shifting).
•
Decrease taxes on wages, income, and wealth while increasing taxes on pollution, resource waste, and environmentally harmful goods and services (tax shifting).
•
Use laws and regulations to encourage pollution prevention and to put limits on resource depletion and degradation.
•
Use tradable permits or rights to pollute or to use resources, in order to limit overall pollution and resource use.
•
Sell services instead of things.
•
Reduce poverty, one of the basic causes of environmental degradation, pollution, and poor health and premature death.
Taking the middle ground in this debate are environmental economists. They generally agree with the model proposed by ecological economists in Figure 14-3, and they argue that some forms of economic growth are not sustainable and should be replaced by more sustainable forms. They would accomplish this by fine-tuning existing economic systems and tools, instead of redesigning some of them to be more effective at promoting sustainability, as many ecological economists would do. Ecological and environmental economists have suggested several strategies for implementing these principles and making the transition to more sustainable eco-economies over the next several decades: •
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Use indicators that monitor economic and environmental health for any given community or country and for the world.
CHAPTER 14
In this chapter, we will look at these proposed solutions in more detail.
Economics, Politics, Worldviews, and Sustainability
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14-2 How Can We Use Economic Tools
to Deal with Environmental Problems?
Most Things Cost a Lot More Than We Might Think The market price, or direct price, that we pay for something does not usually include the indirect, or external, costs of harm to the environment and to human health, associated with its production and use. For example, if we buy a car, the direct price we pay includes the direct, or internal, costs of raw materials, labor, and shipping, and a markup for dealer profit. In using the car, we pay additional direct costs for gasoline, maintenance, repair, and insurance. However, we do not pay the harmful external costs, some of which can affect other people now and in the future. For example, to extract and process raw materials to make a car, manufacturers use nonrenewable energy and mineral resources, produce solid and hazardous wastes, disturb land, pollute the air and water, and release greenhouse gases into the atmosphere. These hidden external costs can have short- and longterm harmful effects on other people, on future generations, and on the earth’s life-support systems. Because these harmful external costs are not included in the market price of a car, most people do not connect them with car ownership. Still, the car buyer and other people in a society pay these hidden costs sooner or later in the forms of poorer health, higher expenses for health care and insurance, higher taxes for pollution control, traffic congestion, and land used for highways and parking lots.
Environmental Economic Indicators Could Help Us Reduce Our Environmental Impact Gross domestic product (GDP) and per capita GDP indicators (see Chapter 1, p. 10) provide a standardized and useful method for measuring and comparing the economic outputs of nations. The GDP is deliberately designed to measure such outputs without distinguishing between goods and services that are environmentally or socially beneficial and those that are harmful. Environmental and ecological economists and environmental scientists call for the development and widespread use of new indicators to help monitor environmental quality and human well-being. One such
indicator is the genuine progress indicator (GPI)—the GDP plus the estimated value of beneficial transactions that meet basic needs, but in which no money changes hands, minus the estimated harmful environmental, health, and social costs of all transactions. The per capita GPI would be the GPI for a country divided by that country’s population at mid-year. The GPI was developed by Redefining Progress, a nonprofit organization that develops economic and policy tools to help promote environmental sustainability. (This group also developed the concept of ecological footprints; see Figure 1-6, p. 13.) Examples of beneficial transactions included in the GPI include unpaid volunteer work, health care provided by family members, child care, and housework. Harmful costs that are subtracted to arrive at the GPI include pollution, resource depletion and degradation, and crime. The GPI is calculated as follows: Genuine benefits not progress = GDP + included in indicator market transactions
–
harmful environmental and social costs
Figure 14-4 compares the per capita GDP and GPI for the United States between 1950 and 2004 (the latest 35,000 30,000 1996 Dollars per person
▲
CONC EPT 14-2 We can use resources more sustainably by including their harmful environmental and health costs in the market prices of goods and services (fullcost pricing); by subsidizing environmentally beneficial goods and services; and by taxing pollution and waste instead of wages and profits.
25,000 20,000 Per capita gross domestic product (GDP)
15,000 10,000 5,000
Per capita genuine progress indicator (GPI) 0 1950
1960
1970
1980 Year
1990
2000
Figure 14-4 Monitoring environmental progress: This graph compares the per capita gross domestic product (GDP) and the per capita genuine progress indicator (GPI) in the United States between 1950 and 2004. Questions: Would you favor making widespread use of this or similar green economic indicators? Why hasn’t this been done? (Data from Redefining Progress, 2006)
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data available). While the per capita GDP rose sharply over this period, the per capita GPI stayed nearly flat, even declining slightly and fluctuating. The genuine progress indicator and other environmental indicators under development are far from perfect, which is true of the GDP as well. But without such indicators, we will not know much about what is happening to people, to the environment, and to the planet’s natural capital, nor will we have a way to evaluate which policies are likely to work best in improving environmental quality and life satisfaction.
We Can Include the Harmful Environmental Costs in the Prices of Goods and Services Most environmental and ecological economists argue for a more environmentally honest market system. It would include the estimated harmful environmental and health costs of goods and services in their market prices to reflect as closely as possible their full costs—internal costs plus external costs. According to environmental and ecological economists, full-cost pricing would reduce resource waste, pollution, and environmental degradation and improve human health by encouraging producers to invent more resource-efficient and less-polluting methods of production. It would also allow consumers to make more informed choices. Jobs and profits would be lost in environmentally harmful businesses as consumers would more often choose green products and services, but jobs and profits would be created in environmentally beneficial businesses. If a shift to full-cost pricing were phased in over two decades, many environmentally harmful businesses would have time to transform themselves into environmentally beneficial businesses. In addition, consumers would also have time to adjust their buying habits to favor more environmentally beneficial products and services. Full-cost pricing seems to make a lot of sense, but why is it not used more widely? First, many producers of harmful and wasteful products would have to charge more for them, and some would go out of business. Naturally, they oppose such pricing. Second, it is difficult to estimate many environmental and health costs. Third, many environmentally harmful businesses have used their political and economic power to obtain government subsidies and tax breaks that help them make profits while keeping their prices artificially low. HOW WOULD YOU VOTE?
✓ ■
Should full-cost pricing be used to set market prices for goods and services? Cast your vote online at www.cengage .com/login.
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Phasing in such a system would require government action. Few if any companies will volunteer to reduce their short-term profits to become more environmentally responsible. Governments can use several strategies to encourage or force producers to work toward full-cost pricing. Let us take a closer look at each of these strategies.
We Can Reward Environmentally Sustainable Businesses One way to encourage a shift to full-cost pricing and promote sustainability is to phase out environmentally harmful subsidies and tax breaks, which cost the world’s governments (taxpayers) at least $2 trillion a year—an average $3.8 million a minute! Examples include depletion subsidies and tax breaks for extracting minerals and fossil fuels, cutting timber on public lands, and irrigating with low-cost water. On paper, phasing out such subsidies may seem like a great idea. In reality, the economically and politically powerful interests receiving them spend a lot of time and money lobbying, or trying to influence governments to continue and even increase these subsidies. They also lobby against subsidies and tax breaks for more environmentally beneficial competitors. Some countries have begun reducing harm- GOOD ful subsidies. Japan, France, and Belgium have NEWS phased out all coal subsidies and Germany plans to do so by 2018. China has cut coal subsidies by about 73% and has imposed a tax on high-sulfur coals.
We Can Tax Pollution and Wastes Instead of Wages and Profits Another way to discourage pollution and resource waste is to use green taxes, or ecotaxes, to help include in market prices many of the harmful environmental and health costs of production and consumption (Concept 14-2). Taxes could be levied on a per-unit basis on the amount of pollution and hazardous waste produced, and on the use of fossil fuels, nitrogen fertilizer, timber, minerals, water, and other resources. To many analysts, the tax system in most countries is backward. It discourages what we want more of—jobs, income, and profit-driven innovation—and encourages what we want less of—pollution, resource waste, and environmental degradation. A more environmentally sustainable economic and political system would lower taxes on labor, income, and wealth, and raise taxes on environmentally harmful activities. With such a tax shift, for example, a tax on coal would cover the health costs of breathing polluted air and the costs of damage from acid deposition (see Chapter 12, p. 249). Then taxes on wages and wealth could be reduced by an equal amount. Some 2,500
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economists, including eight Nobel Prize winners, have endorsed the concept of tax shifting. Proponents point out three requirements for successful implementation of green taxes. First, green taxes would have to be phased in over 10–20 years to allow businesses to plan for the future. Second, income, payroll, or other taxes would have to be reduced by the same amount as the green tax so that there would be no net increase in taxes. Third, the poor and middle class would need a safety net to reduce the regressive nature of any new taxes on essentials such as fuel and food. In Europe and the United States, polls indicate that once such tax shifting is explained to voters, 70% GOOD of them support the idea. Germany’s green tax on NEWS fossil fuels, introduced in 1999, has reduced pollution and greenhouse gas emissions, helped to create about 250,000 new jobs, and led to lower taxes on wages. HOW WOULD YOU VOTE?
✓ ■
Do you favor shifting taxes from wages and profits to pollution and waste? Cast your vote online at www.cengage .com/login.
Environmental Laws and Regulations Can Discourage or Encourage Innovation Environmental regulation is a form of government intervention in the marketplace that is widely used to help control or prevent pollution and to reduce resource waste and environmental degradation. It involves enacting and enforcing laws that set pollution standards, regulate harmful activities such as the release of toxic chemicals into the environment, and protect certain irreplaceable or slowly replenished resources from unsustainable use. So far, most environmental regulation in the United States and many other more-developed countries has involved passing laws that are enforced through a command and control approach. Critics say that this strategy can unnecessarily increase costs and discourage innovation because many of these regulations concentrate on enforcing cleanup instead of prevention. Some regulations also set compliance deadlines that are too short to allow companies to find innovative solutions to pollution and excessive resource use. They may also require the use of specific technologies where less costly but equally effective alternatives might be available or in the process of development. A regulatory approach favored by many economists, as well as environmental and business leaders, is to use incentive-based environmental regulations. Rather than requiring all companies to follow the same fixed procedures or use the same technologies, this approach uses the economic forces of the marketplace to encourage businesses to be innovative in reducing pollution and resource waste. The experience of several European
nations shows that innovation-friendly environmental regulation sets goals, frees industries to meet them in any way that works, and allows enough time for innovation. This can motivate companies to develop green products and industrial processes that create jobs, increase company profits, and make the companies more competitive in national and international markets. For years, many companies generally fought against environmental regulation. But in recent years, a growing number of companies have realized the economic and competitive advantages of making environmental improvements. They now recognize that the value of their shareholders’ investment depends in part on having a good environmental record and that improvements to energy efficiency and resource conservation can save money and boost profits. In other words, environmental stewardship can be good for business. They also realize that if they do not produce a waste or pollutant, they can reduce government-mandated paperwork and they cannot be sued for any human or environmental damage that such outputs might have caused.
Use the Marketplace to Reduce Pollution and Resource Waste In one incentive-based regulation system, the government decides on acceptable levels of total pollution or resource use, sets limits, or caps, to maintain these levels, and gives or sells companies a certain number of tradable pollution or resource-use permits governed by the caps. With this cap-and-trade approach, a permit holder not using its entire allocation can save credits for future expansion, use them in other parts of its operation, or sell them to other companies. The United States GOOD has used this cap-and-trade approach to reduce NEWS the emissions of sulfur dioxide (see Chapter 12, p. 255) and several other air pollutants. Tradable rights can also be established among countries to help preserve biodiversity and to reduce emissions of greenhouse gases and other regional and global pollutants. The effectiveness of such programs depends on how high or low the initial cap is set, and on the rate at which the cap is reduced to encourage further innovation.
We Can Reduce Pollution and Resource Waste by Selling Services Instead of Things In the mid-1980s, German chemist Michael Braungart and Swiss industry analyst Walter Stahel independently proposed a new economic model that would provide profits while greatly reducing resource use and waste. Their idea for more sustainable economies focuses on shifting from the current material-flow economy (Figure 14-2) to a service-flow economy. Instead of buying many goods outright, customers lease or rent the services that such goods provide. In a service-flow CONCEPT 14-2
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I N D I V ID U ALS MAT T E R Ray Anderson
R
ay Anderson is the founder of Interface, a company based in Atlanta, Georgia (USA). The company is the world’s largest commercial manufacturer of carpet tiles, with 26 factories in six countries, customers in 110 countries, and more than $1 billion in annual sales. Anderson changed the way he viewed the world—and his business—after reading Paul Hawken’s book The Ecology of Commerce. In 1994, he announced plans to develop the nation’s first totally sustainable green corporation. Since then, he has implemented hundreds of projects with goals of producing zero waste, greatly reducing energy use, reducing fossil fuel use, and relying on solar energy.
Within 15 years of setting this and other environmental goals, Interface had decreased water usage by 74%, cut its net greenhouse gas emissions by 71%, reduced solid waste by 63%, reduced fossil fuel use by 60%, and lowered energy use by 44%. The company also gets 27% of its total energy and 88% of its electricity from renewable resources. These efforts have saved the company more than $405 million. To help achieve its goal of zero waste, Interface plans to stop selling carpet and to lease it. The company will install, clean, and inspect the carpet on a monthly basis, repair or replace worn carpet tiles overnight, and recycle worn-out tiles into new carpeting.
economy, a manufacturer makes more money if its product requires the minimum amount of materials, lasts as long as possible, and is easy to maintain, repair, reuse, or recycle. Such an economic shift is under way in some businesses. Since 1992, Xerox has been leasing most of its copy machines as part of its mission to provide document services instead of selling photocopiers. When a customer’s service contract expires, Xerox takes the machine back for reuse or remanufacture. It has a goal of sending no material to landfills or incinerators. To save money, Xerox designs machines to have few parts, be energy efficient, and emit as little noise, heat, ozone, and chemical waste as possible. Canon in Japan and Fiat in Italy are taking similar measures.
Anderson is one of a growing number of business leaders committed to finding more economically and ecologically sustainable, yet profitable, ways to do business. Sales have increased to $1 billion, making Interface the world’s largest seller of carpet tiles, and profits have tripled. Anderson has also created a new consulting group as part of Interface to help other businesses start on the path toward being more sustainable. He believes that businesses can and should practice environmental stewardship and social responsibility in order to benefit their profit margins, their employees and customers, and the planet.
In Europe, Carrier has begun shifting from selling heating and air conditioning equipment to providing a service to customers that gives them the indoor temperatures they want. It makes higher profits by leasing and installing energy-efficient heating and air conditioning equipment that lasts as long as possible and is easy to rebuild or recycle. Carrier also makes money helping clients to save energy by adding insulation, eliminating heat losses, and boosting energy efficiency in offices and homes. Similarly, the large carpet-tile company Interface, led by CEO Ray Anderson, plans to lease rather than sell carpet to its customers. Anderson also promotes several other environmentally beneficial practices (Individuals Matter, above).
14-3 How Can Reducing Poverty Help Us
to Deal with Environmental Problems? ▲
C O NC EPT 14-3 Reducing poverty can help us to reduce population growth, resource use, and environmental degradation.
The Gap between the Rich and the Poor Is Getting Wider Poverty is defined as the inability to meet one’s basic economic needs. According to the World Bank and the United Nations, 1.4 billion people—a number 4.5 times the size of the U.S. population—struggle to survive on an income equivalent to less than $1.25 a day Poverty has numerous harmful health and environmental effects (see Figure 1-11, p. 17). Reducing pov-
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erty benefits individuals, economies, and the environment, while empowering women and helping to slow population growth (Concept 14-3). Most neoclassical economists believe that a growing economy can help the poor by creating more jobs and providing greater tax revenues, which can be used to help the poor to help themselves. This economic process is often referred to as the trickle-down effect. However, since 1960, most of the benefits of global economic growth, as measured by income, have been flooding up
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to the rich, rather than trickling down to workers at the bottom fifth of the economic ladder. Since 1980, this wealth gap between the rich and the poor has grown. A few years ago the United Nations calculated that the world’s 500 richest people earned more than the world’s 416 million poorest people. South African President Thabo Mbeki told delegates at the 2003 Johannesburg World Summit on Sustainable Development, “A global human society based on poverty for many and prosperity for a few, characterized by islands of wealth, surrounded by a sea of poverty, is unsustainable.”
We Can Reduce Poverty Analysts point out that reducing poverty will require the governments of most of the less-developed countries to make policy changes. This will have to include emphasizing education to develop a trained workforce that can participate in an increasingly globalized economy. In 2008, less-developed countries were paying an average of about $571,000 a minute in interest to moredeveloped countries. Analysts have suggested that moredeveloped countries and international lending agencies forgive all of this debt for the poorest, most heavily indebted countries, on the condition that money saved on debt interest be devoted to meeting basic human needs. In 2005, the heads of the eight major industrial countries agreed to cancel the debts of 18 of the poorest debt-ridden countries (14 of them in Africa and 4 in Latin America). Governments, businesses, international lending agencies, and wealthy individuals in more-developed countries could also: •
Mount a massive global effort to combat malnutrition and the infectious diseases that kill millions of people prematurely.
•
Provide universal primary school education and eradicate illiteracy for nearly 800 million of the world’s adults.
•
Provide assistance to stabilize population growth in less-developed countries as soon as possible, mostly by investing in family planning, reducing poverty, and elevating the social and economic status of women.
•
Focus on sharply reducing the total and per capita ecological footprints of their own countries as well as those of rapidly growing less-developed countries such as China and India.
•
Make large investments in small-scale infrastructure such as solar-cell power facilities in villages, as well as sustainable agriculture projects that would enable less-developed nations to work towards more energy-efficient and sustainable economies.
•
Encourage lending agencies to make small loans to poor people who want to increase their income (see the Case Study that follows).
■ C AS E S T UDY
Muhammad Yunus and Microloans for the Poor Most of the world’s poor people are eager to work to escape from their desperate circumstances. But they do not have a credit record or other means necessary to get a loan in order to buy seeds and fertilizer to grow enough food or start a small business. In 1983, economist Muhammad Yunus started the Grameen (Village) Bank in Bangladesh, a country GOOD with a high poverty rate and a rapidly growing NEWS population. Since then, the bank has provided a total of $7.4 billion in microloans of $50 to $500 at very low interest rates to 7.6 million impoverished people who did not qualify for loans at traditional banks. About 97% of these loans have been used by women, mostly to plant crops or to start small businesses. To promote loan repayment, the bank puts borrowers into groups of five. If a group member fails to make a weekly payment, other members must pay it. The average repayment rate has been 95%—much greater than the average repayment rate for loans by conventional banks. Also, the bank has made a consistent profit. Typically, about half of the bank’s microborrowers move above the poverty line and improve their lives within 5 years of receiving their loans. Birth rates are also lower among most of the borrowers. Muhammad Yunus and his Grameen Bank developed a new business model that combined the power of market capitalism with the desire for a more humane and sustainable world. In 2006, Yunus and his colleagues at the bank jointly won the Nobel Peace Prize for their pioneering use of microcredit. Banks based on the Grameen microcredit model have spread to 58 countries, including the United States. By 2009, this approach had helped at least 133 million people worldwide to work their way out of poverty.
We Can Achieve the World’s Millennium Development Goals In 2000, the world’s nations set goals—called Millennium Development Goals—for sharply reducing hunger and poverty, improving health care, and moving toward environmental sustainability by 2015. Moredeveloped countries pledged to donate 0.7% of their annual national income to less-developed countries to help them in achieving these goals. However, by 2009, only five countries—Denmark, Luxembourg, Sweden, Norway, and the Netherlands— had donated what they had promised. In fact, the average amount donated in most years has been 0.25% of national income. The United States gives only 0.16% of its national income to help poor countries. For any country, deciding whether or not to commit 0.7% of annual national income toward these goals requires an evaluation of priorities (Figure 14-5, p. 310). CONCEPT 14-3
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309
Expenditures per year needed to Reforest the earth
Expenditures per year (2008) World military
$6 billion
Protect tropical forests
$8 billion
Restore rangelands
$9 billion
$1.4 trillion
U.S. military
$734 billion
U.S. dog food
$39 billion
U.S. highways Stabilize water tables
$29 billion
$10 billion U.S. foreign aid
Deal with global HIV/AIDS Restore fisheries Provide universal primary education and eliminate illiteracy Protect topsoil on cropland Protect biodiversity Provide basic health care for all Provide clean drinking water and sewage treatment for all
$10 billion
U.S. potato chips and similar snacks
$13 billion
U.S. cosmetics U.S. EPA
$14 billion
$27 billion $22 billion $8 billion $7.2 billion
$24 billion $31 billion $33 billion $37 billion
Eliminate hunger and malnutrition
$48 billion Total Earth Restoration and Social Budget $245 billion
Figure 14-5 What should our priorities be? Question: Which item in the bar graph on the right would you reduce or do without to pay for solving some of the problems listed in the graph on the left part of the figure? (Data from United Nations, World Health Organization, U.S. Department of Commerce, U.S. Office of Management and Budget, World Bank, Earth Policy Institute, and Stockholm International Peace Research Institute)
14-4 How Can We Make the Transition to More
Environmentally Sustainable Economies? ▲
C O NC EPT 14-4 We can use the three principles of sustainability as well as various economic and environmental strategies to develop more environmentally sustainable economies.
We Are Living Unsustainably What might happen if growing populations continue to use and waste energy and matter resources at an increasing rate in today’s high-throughput economies? The law of conservation of matter (see Chapter 2, p. 29) and the two laws of thermodynamics (see Chapter 2, p. 30) tell us that eventually, this resource consumption and waste will exceed the capacity of the environment to sufficiently renew those resources, to dilute and degrade waste matter, and to absorb waste heat. A temporary solution to this problem is to convert our linear throughput economy into a circular matter recycling and reuse economy. Such an economy mimics nature by recycling and reusing most matter
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outputs instead of dumping them into the environment. This involves applying the chemical recycling principle of sustainability (see back cover). Although changing to a matter recycling and reuse economy would buy some time, it would not allow ever more people to use ever more resources indefinitely, even if all matter resources were somehow perfectly recycled and reused. The two laws of thermodynamics tell us that recycling and reusing matter resources always requires using high-quality energy (which cannot be recycled) and adds waste heat and various pollutants to the environment. This is not sustainable. The three scientific laws governing matter and energy changes and the three principles of sustainability suggest that the best long-term solution to our
Economics, Politics, Worldviews, and Sustainability
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System throughputs
Inputs (from environment) High-quality energy
Energy conservation
High-quality matter
Waste and pollution prevention
Outputs (into environment) Low-quality energy (heat)
Low-waste economy
Figure 14-6 Solutions: Learning and applying lessons from nature can help us to design and manage more sustainable economies. A low-throughput economy, based on energy flow and matter recycling, works with nature to reduce excessive throughput and the unnecessary waste of matter and energy resources (as suggested in the four lighter-shaded boxes). This is done by (1) reusing and recycling most nonrenewable matter resources; (2) using renewable resources no faster than they are replenished; (3) reducing resource waste by using matter and energy resources more efficiently; (4) reducing unnecessary and environmentally harmful forms of consumption; (5) emphasizing pollution prevention and waste reduction; and (6) controlling population growth to reduce the number of matter and energy consumers. Question: What are three ways in which your school could operate more like a lowthroughput economy?
Pollution control
Waste and pollution
Recycle and reuse
Environmentally Sustainable Economy (Eco-Economy)
Economics Reward (subsidize) environmentally sustainable economic development Penalize (tax and do not subsidize) environmentally harmful economic growth Shift taxes from wages and profits to pollution and waste Use full-cost pricing
environmental and resource problems is to shift from a high-throughput (high-waste) economy based on everincreasing matter and energy flow (Figure 14-2) to a more sustainable low-throughput (low-waste) economy, as summarized in Figure 14-6. In other words, we can live more sustainably by controlling human population growth, using and wasting less matter and energy resources, and reusing, recycling, or composting most matter resources.
Sell more services instead of more things Do not deplete or degrade natural capital Live off income from natural capital Reduce poverty Use environmental indicators to measure progress Certify sustainable practices and products Use eco-labels on products
We Can Make Money and Create Jobs by Shifting to an Eco-Economy Figure 14-7 summarizes suggestions by Paul Hawken, Lester R. Brown, and other environmental and business leaders for using the economic tools discussed in this chapter to make the transition to more environmentally sustainable economies over the next several decades. Such strategies would also apply the three principles of sustainability (see back cover). Hawken has a simple golden rule for such an economy: “Leave the world better than you found it, take no more than you need, try not to harm life or the environment, and make amends if you do.” In making the shift to eco-economies, some industries and businesses will disappear or remake themselves, and new ones will appear—a normal process in a dynamic and creative capitalist economy. Improving environmental quality is now a major growth GOOD industry that is creating profits and new jobs (Fig- NEWS ure 14-8, p. 312).
Resource Use and Pollution Cut resource use and waste by reducing, reusing, and recycling Improve energy efficiency Rely more on renewable solar, wind and geothermal energy Shift from a nonrenewable carbon-based (fossil fuel) economy to a non-carbon renewable energy economy Ecology and Population Mimic nature Preserve biodiversity Repair ecological damage Stabilize human population Figure 14-7 Solutions: We can use certain tools for shifting to more environmentally sustainable economies, or eco-economies, during this century. Questions: Which five of these solutions do you think are the most important? Why?
CONCEPT 14-4 Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Environmentally Sustainable Businesses and Careers Aquaculture
Environmental law
Biodiversity protection
Environmental nanotechnology Fuel cell technology
Biofuels Climate change research
Geographic information systems (GIS)
Conservation biology
Geothermal geologist
Ecotourism management
Hydrologist
Energy-efficient product design Environmental chemistry Environmental design and architecture Environmental economics Environmental education Environmental engineering Environmental entrepreneur Environmental health
Figure 14-8 Here are some environmental businesses and careers that could grow quickly in coming decades. These businesses are expected to flourish during this century, while environmentally harmful, or sunset, businesses are expected to decline. See the website for this book for more information on various environmental careers. Questions: How could some of these careers help you to apply the three principles of sustainability? Have you considered any of these careers?
Hydrogen energy
Marine science Pollution prevention Recycling and reuse Selling services in place of products Solar cell technology Sustainable agriculture Sustainable forestry Urban gardening Urban planning Waste reduction Watershed hydrologist Water conservation Wind energy
An increasing number of economists and business leaders say that making the shift to an eco-economy could be the greatest investment opportunity of this century. According to Worldwatch Institute estimates, green businesses employ more than 11 million people, including 2 million in the United States, and these numbers are growing rapidly. However, much of this opportunity depends squarely on politics. It involves the difficult task of convincing more business leaders, elected officials, and voters to begin changing current government systems of economic rewards and penalties, as discussed in the next section.
14-5 What Is Environmental Policy
and How Is It Made? ▲
C O NC EPT 14-5 Through its policies, a government can help to protect environmental and public interests, and encourage more environmentally sustainable economic development.
Democracy Does Not Always Allow for Quick Solutions Democracy is government by the people through elected officials and representatives. In a constitutional democracy, a constitution provides the basis of government authority and, in most cases, limits government power by mandating free elections and guaranteeing the right of free speech. Political institutions in most constitutional democracies are designed to allow gradual change that ensures economic and political stability. In the United States, for example, rapid and destabilizing change is curbed by a
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system of checks and balances that distributes power among three branches of government—legislative, executive, and judicial—and among federal, state, and local governments. In passing laws, developing budgets, and formulating regulations, elected and appointed government officials must deal with pressure from many competing specialinterest groups. Each of these groups advocates passing laws, providing subsidies or tax breaks, or establishing regulations favorable to its cause, while attempting to weaken or repeal laws, subsidies, tax breaks, and regulations unfavorable to its position. Some special-interest groups such as corporations are profit-making organiza-
Economics, Politics, Worldviews, and Sustainability
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tions. Others are nongovernmental organizations (NGOs), most of which are nonprofit, such as labor unions and environmental organizations. The design for stability and gradual change in democracies is highly desirable. But several features of democratic governments hinder their ability to deal with environmental problems. For example, problems such as climate change and biodiversity loss are complex and difficult to understand. Such problems also have long-lasting effects, are interrelated, and require integrated, long-term solutions that emphasize prevention. But because local, state, and national elections are held as often as every 2 years, most politicians spend much of their time seeking reelection and tend to focus on short-term, isolated issues rather than on long-term, complex, and time-consuming problems. Another problem is that many political leaders have too little understanding of how the earth’s natural systems work and how those systems support all life, economies, and societies. With hundreds of issues to deal with, they have far too little time for educating themselves in this area.
Certain Principles Can Guide Us in Making Environmental Policy Environmental policy consists of environmental laws, rules, and regulations developed, implemented, and enforced by one or more government agencies, along with environmental programs funded by those agencies. Analysts suggest that when evaluating existing or proposed environmental policies, legislators and individuals should be guided by seven principles designed to minimize environmental harm: 1. The humility principle: Our understanding of nature and how our actions affect nature is quite limited. 2. The reversibility principle: Try not to make a decision that cannot be reversed later if the decision turns out to be wrong. 3. The net energy principle: Do not encourage the widespread use of energy alternatives or technologies with low net-energy yields (see Chapter 9, Science Focus, p. 190), which cannot compete in the open marketplace without government subsidies. 4. The precautionary principle: When substantial evidence indicates that an activity threatens human health or the environment, take precautionary measures to prevent or reduce such harm, even if some of the cause-and-effect relationships are not well-established scientifically.
7. The environmental justice principle: Establish environmental policy to ensure that no group of people will bear an unfair share of the burden created by pollution, environmental degradation, or the execution of environmental laws.
Developing Environmental Policy Is a Controversial Process A major function of government is to develop and implement policy for dealing with various issues. Figure 14-9 (p. 314) is a greatly simplified overview of how individuals and lobbyists working for and against a particular environmental law interact with the three branches of the federal government in the United States. Figure 14-10 (p. 315) lists some of the major environmental laws passed in the United States since 1969. In the United States, passing a law is not enough to make policy. The next step involves trying to get Congress to appropriate enough funds to implement and enforce each law. Indeed, developing and adopting a budget is the most important and controversial activity of the executive and legislative branches (see the two Case Studies that follow). Once Congress has passed a law and funded a program, the appropriate government department or agency must draw up regulations for implementing it. A group affected by the program and its regulations may take the agency to court for failing to implement and enforce the regulations effectively or for enforcing them too rigidly. Businesses facing environmental regulations often put political pressure on regulatory agencies and executives to appoint people from the regulated industries to high positions within the agencies. In other words, the regulated try to take over the regulatory agencies and become the regulators—described by some as “putting foxes in charge of the henhouse.” In addition, people in regulatory agencies work closely with officials in the industries they are regulating, often developing friendships with them. Some companies and organizations within regulated industries also offer high-paying jobs to regulatory agency employees in an attempt to influence their regulatory decisions. This can lead to what some critics have labeled a revolving door regulatory system, in which employees move back and forth between regulatory agencies and the industries they regulate. ■ C AS E S T UDY
5. The prevention principle: Whenever possible, make decisions that help to prevent a problem from occurring or becoming worse.
Managing Public Lands in the United States—Politics in Action
6. The polluter-pays principle: Develop regulations and use economic tools such as green taxes to ensure that polluters bear the costs of dealing with the pollutants and wastes they produce.
No nation has set aside as much of its land for public use, resource extraction, enjoyment, and wildlife habitat as has the United States. The federal government manages roughly 35% of the country’s land, which belongs CONCEPT 14-5
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Laws
Legislative branch
Lobbyists
Lobbyists
Courts
Executive branch
Regulators
Public hearing Civil suits
Environmental organizations
Corporations and small businesses
Membership support
Patronize or boycott
Individuals
Purchase recyclable, recycled, and environmentally safe products
Reuse and recycle various items
Plant an organic garden
Donate clothes and used goods to charities
Use water, energy, and other resources efficiently
Walk, ride a bike, or use a carpool or mass transit
Figure 14-9 This is a greatly simplified overview of how individuals, corporations, and environmental organizations interact with each other and with the legislative, executive, and judicial branches of the U.S. government. The bottom of this diagram also shows some ways in which individuals can bring about environmental change through their own lifestyles. (See the website for this book for details on contacting elected representatives.)
to every American. About three-fourths of this federal public land is in Alaska and another fifth is in the western states (Figure 14-11, p. 316). Some federal public lands are used for many different purposes. For example, the National Forest System consists of 155 national forests and 22 national grasslands. These lands, managed by the U.S. Forest Service (USFS), are used for logging, mining, livestock grazing, farming, oil and gas extraction, recreation, and conservation of watershed, soil, and wildlife resources. The Bureau of Land Management (BLM) manages large areas of land—40% of all land managed by the
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federal government. These lands are used primarily for mining, oil and gas extraction, logging, and livestock grazing. The U.S. Fish and Wildlife Service (USFWS) manages 549 national wildlife refuges. Most refuges protect habitats and breeding areas for waterfowl and big game to provide a harvestable supply of these species for hunters. Permitted activities in most refuges include hunting, trapping, fishing, oil and gas development, mining, logging, grazing, some military activities, and farming. The uses of some other public lands are more restricted. The National Park System, managed by the
Economics, Politics, Worldviews, and Sustainability
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1969
National Environmental Policy Act (NEPA)
1970
Clean Air Act
1971
1973
Clean Water Act; Coastal Zone Management Act; Federal Insecticide, Fungicide, and Rodenticide Act; Marine Mammal Protection Act Endangered Species Act
1974
Safe Drinking Water Act
1972
1975 1976 1977 1978
Resource Conservation and Recovery Act (RCRA); Toxic Substances Control Act; National Forest Management Act Soil and Water Conservation Act; Clean Water Act; Clean Air Act Amendments National Energy Act
1979 1980
Superfund law; National Energy Act Amendments; Coastal Zone Management Act Amendments
1981 1982
Endangered Species Act Amendments
1983 1984
Hazardous and Solid Waste Amendments to RCRA; Safe Drinking Water Act Amendments
1985
Endangered Species Act Amendments
1986
Superfund Amendments and Reauthorization
1987
Clean Water Act Amendments
1988
Federal Insecticide, Fungicide, and Rodenticide Act Amendments; Endangered Species Act Amendments
1989 1990
Clean Air Act Amendments; Reauthorization of Superfund; Waste Reduction Act
1991 1992
Energy Policy Act
1993 1994 1995
Endangered Species Act Amendments
1996
Safe Drinking Water Act Amendments
Figure 14-10 These are some of the major environmental laws and their amended versions enacted in the United States since 1969.
National Park Service (NPS), includes 58 major parks and 331 national recreation areas, monuments, memorials, battlefields, historic sites, parkways, trails, rivers, seashores, and lakeshores. Only camping, hiking, sport fishing, and boating can take place in the national parks, whereas sport hunting, mining, and oil and gas drilling are allowed in national recreation areas. The most restricted public lands are 702 roadless areas that make up the National Wilderness Preservation System. These areas lie within the other public lands and
are managed by the agencies in charge of those lands. Most of these areas are open only for recreational activities such as hiking, sport fishing, camping, and nonmotorized boating. Many federal public lands contain valuable oil, natural gas, coal, geothermal, timber, and mineral resources. The appropriate use and management of the resources on and under these lands has been debated since the 1800s. Most conservation biologists, environmental economists, and many other economists believe that four principles should govern the use of public lands: 1. They should be used primarily for protecting biodiversity, wildlife habitats, and ecosystems. 2. No one should receive government subsidies or tax breaks for using or extracting resources on public lands. 3. The American people deserve fair compensation for the use of their property. 4. All users or extractors of resources on public lands should be fully responsible for any environmental damage they cause. There is strong and effective opposition to these ideas. Developers, resource extractors, numerous neoclassical economists, and many citizens tend to view public lands in terms of their usefulness in providing mineral, timber, and other resources, and increasing short-term economic growth. They have succeeded in blocking implementation of the four principles listed above. For example, in recent years, analyses of budgets and appropriations reveal that the government has given an average of $1 billion a year in subsidies and tax breaks to privately owned interests that use U.S. public lands for mining, fossil fuel extraction, logging, and grazing. Some developers and resource extractors have sought to go farther. Here are five of the proposals that such interests have made to get the U.S. Congress to open up more federal lands (owned jointly by all citizens) for development: 1. Sell public lands or their resources to corporations or individuals, usually at proposed prices that are less than market value, or turn over their management to state and local governments. 2. Slash federal funding for administration of regulations over public lands. 3. Cut old-growth forests in the national forests for timber and for making biofuels, and replace them with tree plantations. 4. Open national parks, national wildlife refuges, and wilderness areas to oil drilling, mining, off-road vehicles, and commercial development. 5. Eliminate or take regulatory control away from the National Park Service and launch a 20-year construction program in the parks to build new concessions and theme parks that will be run by private firms. CONCEPT 14-5
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Figure 14-11 This map shows the national forests, parks, and wildlife refuges managed by the U.S. federal government. These and other public lands are jointly owned by U.S. citizens. Questions: Do you think U.S. citizens should jointly own more or less of the nation’s land? Why or why not? (Data from U.S. Geological Survey)
National parks and preserves National forests National wildlife refuges
Between 2002 and 2009, the U.S. Congress and the executive branch expanded the extraction of mineral, timber, and fossil fuel resources on U.S. public lands, and weakened environmental laws and regulations protecting such lands from abuse and exploitation. Conservation biologists argue that these environmentally unsustainable activities will eventually degrade and deplete the country’s irreplaceable natural capital. They argue for putting more emphasis on scientific principles in the management of public lands (Science Focus, at right). Although this case study has focused on the debate over the use of public lands in the United States, the same issues apply to the use of government or publicly owned lands in other countries.
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■ C AS E S T UDY
U.S. Environmental Laws and Regulations Have Been under Attack Environmental laws in the United States have been highly effective, especially in controlling pollution. However, since 1980 a well-organized and well-funded movement has mounted a strong campaign to weaken or repeal existing environmental laws and regulations, and to change the ways in which public lands (Figure 14-11) are used. Three major groups are strongly opposed to various environmental laws and regulations: some corporate leaders and other powerful people who see them
Economics, Politics, Worldviews, and Sustainability
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S C I E NC E FO C U S Logging in U.S. National Forests Is Controversial
A
ccording to federal law, U.S. national forests are supposed to be managed according to two scientifically based principles: the principle of sustainable yield, which holds that trees in national forests should not be harvested faster than they are replenished; and the principle of multiple use, which calls for a variety of uses on the same forest land at the same time. However, there has been controversy for decades over the multiple-use principle. Timber companies push for the ability to cut as much timber in national forests as possible. Biodiversity experts and many environmental scientists argue that we should manage national forests primarily to provide recreation
and to sustain biodiversity, water resources, and other ecological services. By law, the U.S. Forest Service (USFS) must sell timber for no less than the cost of reforesting the land. However, the USFS timbercutting program loses money because the revenues from timber sales do not cover the expenses of road building, timber sale preparation, administration, and other overhead costs paid for by the nation’s citizens, who jointly own these forests. More than 644,000 kilometers (400,000 miles) of roads have been cut through the national forests at taxpayer’s expense, primarily to facilitate logging. A 2005 study by the Earth Island Institute found that because of such government sub-
as threats to their profits, wealth, and power; citizens who see them as threats to their private property rights and jobs; and state and local government officials who resent having to implement federal laws and regulations with little or no federal funding (unfunded mandates), or who disagree with certain federal regulations. One problem working against strong regulations is that the focus of environmental issues has shifted from easy-to-see dirty smokestacks and filthy rivers to more complex, controversial, long-term, and often invisible environmental problems such as climate change, biodiversity loss, and groundwater pollution. It is difficult to explain such complex issues to the public and to mobilize support for often controversial, expensive, and long-range solutions to such problems. Another problem is that some environmentalists have primarily brought bad news about the state of the environment to the general public. History shows that bearers of bad news are not well received, and opponents of the environmental movement have used this to undermine environmental concerns. History also shows that people are moved to bring about change mostly by an inspiring and hopeful vision of what the world could be like. So far, environmental groups have not worked together to develop broad, compelling, and positive visions of a more environmentally sustainable future for humans and other species. Since 2000, efforts to weaken environmental laws and regulations have escalated. Nevertheless, independent polls show that more than 80% of the U.S. public strongly support environmental laws and regulations and do not want them weakened. However, polls also show that less than 10% of the U.S. public (and in hard economic times only about 2–3%) consider the environment to be one of the nation’s most pressing problems. As a result, environmental concerns often do not get transferred to the ballot box or the pocketbook.
sidies, timber sales from U.S. federal lands had lost money for their taxpayer owners in 97 of the previous 100 years. Thus, not even the value of the timber was being realized, and this situation has not changed. However, according to a 2000 study by the accounting firm ECONorthwest, recreation, hunting, and fishing in national forests add ten times more money to the national economy and provide seven times more jobs than does the extraction of timber and other resources. Critical Thinking Should national forests be managed primarily according to scientific principles or according to market forces? Explain.
Preventing further weakening of the U.S. environmental laws and regulations, repairing the damage that has been done, and improving existing laws and regulations will require the same kind of organized political pressure from concerned citizens that led to passage of important environmental laws in the first place. Science-based environmental education for children and adults should also get a high priority. People on all sides of important environmental issues can listen to one another’s concerns and work together to find solutions and to improve environmental laws.
Individuals Can Influence Environmental Policy A major theme of this book is that individuals matter. History shows that significant change usually comes from the bottom up when individuals join with each other to bring about change. Without grassroots political action by millions of individual citizens and organized citizen groups, the air that millions of people breathe today and the water they drink would be much more polluted, and much more of the earth’s biodiversity would have been lost. Figure 14-12 (p. 318) lists ways in which you can influence and change local, state, and national government policies in constitutional democracies. Many people, on their own, recycle, buy eco-friendly products, and do other important things to help the environment. But when people work together, starting at the local level, they can also influence environmental policy. Pioneering conservation biologist Aldo Leopold (Individuals Matter, p. 325) certainly believed this, as is reflected in his statement: “All ethics rest upon a single premise: that the individual is a member of a community of interdependent parts.” CONCEPT 14-5
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What Can You Do? Influencing Environmental Policy ■
Become informed on issues
■
Make your views known at public hearings
■
Make your views known to elected representatives, and understand their positions on environmental issues
■
Contribute money and time to candidates who support your views
■
Vote
■
Run for office (especially at local level)
■
Form or join nongovernment organizations (NGOs) seeking change
■
Support reform of election campaign financing that reduces undue influence by corporations and wealthy individuals
Figure 14-12 Individuals matter: These are some of the ways in which you can influence environmental policy. Questions: Which three of these actions do you think are the most important? Which ones, if any, do you take?
Not only can we participate, but each of us can also provide environmental leadership in several ways. First, we can lead by example, using our own lifestyles to show others that change is possible and can be beneficial. Second, we can work within existing economic and political systems to bring about environmental improvement by campaigning and voting for eco-friendly candidates and by communicating with elected officials. We can also send a message to companies that we feel are harming the environment through their products or policies by
voting with our wallets—not buying their products or services and letting them know why. Another way to work within the system is to choose one of the many rapidly growing green careers (Figure 14-8). Third, we can run for some sort of local office. Look in the mirror. Maybe you are someone who can make a difference as an officeholder. Fourth, we can propose and work for better solutions to environmental problems. Leadership is much more than just taking a stand for or against something. It also involves coming up with solutions to problems and persuading people to work together to achieve them, If we care enough, each of us can make a difference, as Dianne Wilson did (Individuals Matter, below).
Citizen Environmental Groups Play Important Roles The spearheads of the global conservation, environmental, and environmental justice movements are the tens of thousands of nonprofit, nongovernmental organizations (NGOs) working at the international, national, state, and local levels. The growing influence of these organizations is one of the most important changes influencing environmental decisions and policies (Concept 14-5). NGOs range from grassroots groups with just a few members to organizations like the World Wildlife Fund (WWF), a global organization that operates in 100 countries. Other international groups with large memberships include Greenpeace, The Nature Conservancy, Conservation International, and the Grameen Bank (see Case Study, p. 309).
I N D I V ID U ALS MAT T E R Diane Wilson
I
n 1989, Diane Wilson was a fourthgeneration shrimp boat captain and a working-class mother of five when she had to stop shrimping in Lavaca Bay near Seadrift, Texas, along the U.S. Gulf Coast, because the shrimp catch had declined significantly. One day, another shrimper brought her a newspaper clipping saying that impoverished Calhoun County, where Seadrift is located, was one of the most polluted counties in the United States. Despite living in Seadrift all of her life, Wilson had never heard anything about this pollution that was so poisonous it could threaten the health of many of the town’s residents. She was outraged and set up a public meeting to discuss pollution of the bay caused by chemical plants in the area. Local officials and business leaders were furious about Wilson’s complaints because
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the chemical plants were the county’s largest employer. Her character was called into question, neighbors shunned her, thugs threatened her, and she even received death threats. Wilson and environmental lawyer Jim Blackburn filed a lawsuit charging Formosa Plastics, a multinational Taiwanese chemical company, with dumping toxic chemicals into the bay. With only a high school education, Wilson learned how to file legal briefs and analyze mountains of scientific and highly technical EPA documents. After years of legal proceedings, protests, and bad publicity for their corporations, Formosa Plastics and Dow Chemical (which was also being sued for dumping chemicals into the bay) agreed to stop discharging pollutants into the bay. Wilson is now an
activist for environmental and social justice. She has practiced nonviolent protest and civil disobedience and has gone on hunger strikes to protest releases of toxic chemicals by companies in her community. As a result, she has been arrested and put in jail 13 times. Wilson wrote a book about her struggle entitled An Unreasonable Woman: A True Story of Shrimpers, Politicos, Polluters, and the Fight for Seadrift, Texas (Chelsea Green, 2005). She has received numerous environmental awards and acclaim as an important new writer with an inspiring message. Wilson, who likes to call herself “nobody particular,” urges everyone to help change the world by being committed to a cause and standing up for what they believe.
Economics, Politics, Worldviews, and Sustainability
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In the United States, more than 8 million citizens belong to more than 30,000 NGOs that deal with environmental issues. They range from small grassroots groups to large, heavily funded mainline groups, the latter usually staffed by expert lawyers, scientists, economists, lobbyists, and fund-raisers. The largest of these groups have become powerful and important forces within the U.S. political system. They have helped to persuade Congress to pass and strengthen environmental laws (Figure 14-10), and they fight attempts to weaken or repeal such laws. Some industries and environmental groups are working together to find solutions to environmental problems. For example, the Environmental Defense Fund worked with McDonald’s to redesign its packaging system to eliminate its plastic hamburger containers. In addition, the Rainforest Alliance has worked with Chiquita Banana to certify the health, labor, and environmental practices on Chiquita’s farms. The base of the environmental movement in the United States and throughout the world consists of thousands of grassroots citizens’ groups organized to improve environmental quality, often at the local level. According to political analyst Konrad von Moltke, “There isn’t a government in the world that would have done anything for the environment if it weren’t for the citizen groups.” Taken together, a loosely connected worldwide network of grassroots NGOs working for bottom-up political, social, economic, and envi- GOOD ronmental change can be viewed as an emerging NEWS citizen-based global sustainability movement. These groups have worked with individuals and communities to oppose harmful projects such as landfills, waste incinerators, and nuclear waste dumps, as
well as to fight against the clear-cutting of forests and pollution from factories and power plants. They have also taken action against environmental injustice. Grassroots groups have organized conservation land trusts and other efforts to save wetlands, forests, farmland, and ranchland from development. They have also helped to restore forests, wetlands, and rivers. Most grassroots environmental groups use the nonviolent and nondestructive tactics such as protest marches, tree sitting (see Individuals Matter, below), and other devices for generating publicity to help educate and encourage the public to oppose various environmentally harmful activities. Much more controversial are militant environmental groups that use violent means, such as breaking into labs to free animals used in drug testing and destroying property such as bulldozers and SUVs. Most environmentalists strongly oppose such tactics. HOW WOULD YOU VOTE?
✓ ■
Do you support the use of nonviolent and nondestructive civil disobedience tactics by environmental groups and individuals? Cast your vote online at www.cengage.com/login.
Students and Educational Institutions Can Play Important Environmental Roles Since the mid-1980s, there has been a boom in environmental awareness on college campuses and in public and private schools around the world. Most student environmental groups work with members of their
I ND I VI D UALS M ATTE R Butterfly in a Redwood Tree
J
ulia Butterfly Hill spent 2 years of her life on a small platform near the top of a giant redwood tree in California to protest the clear-cutting of an old-growth forest of these ancient trees, some of them more than 1,000 years old. She and other protesters were illegally occupying these trees in the late 1990s as a form of nonviolent civil disobedience, similar to that used decades ago by Mahatma Gandhi in his efforts to end the British occupation of India, and by Martin Luther King in the U.S. civil rights movement. Hill had never participated in an environmental protest or act of civil disobedience. She went to the site to express her belief that it was wrong for the property owner to cut down these ancient giants for short-term economic gain. She planned to stay for only a few days.
But after seeing the destruction and climbing one of these magnificent trees, she ended up staying in the tree for 2 years to publicize what was happening and to help save the surrounding trees. She became a symbol of the protest and, during her stay, used a cell phone to communicate with members of the mass media throughout the world to help develop public support for saving the trees. Can you imagine spending 2 years of your life in a tree on a platform not much bigger than a king-sized bed, hovering 55 meters (180 feet) above the ground, while enduring high winds, intense rainstorms, snow, and ice? All around her was noise from trucks, chainsaws, and helicopters. Although Hill lost her courageous battle to save the surrounding forest, she persuaded
the timber company Pacific Lumber MAXXAM to save her tree (which she named Luna) and a 60-meter (200-foot) buffer zone around it. Not too long after she descended from her perch, someone used a chainsaw to seriously damage the tree. Cables and steel plates are now used to preserve it. But maybe Hill did not lose, after all. The book she wrote about her stand, and her subsequent travels to campuses all over the world, have inspired a number of young people to stand up for protecting biodiversity and for other environmental causes. Julia Butterfly Hill led others by following in the tradition of Gandhi, who said, “My life is my message.” Would you spend a day or a week of your life protesting something that you believed to be wrong?
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school’s faculty and administration to bring about GOOD environmental improvements in their schools NEWS and local communities. Many of these groups make environmental audits of their campuses or schools. They gather data on practices affecting the environment and use them to propose changes that will make their campuses or schools more environmentally sustainable while usually saving money in the process. In 2008, the National Wildlife Federation published a useful guide for students wishing to perform such audits. See http://www.nwf.org/ campusecology/BusinessCase/index.cfm. There are a number of examples of this greening of college campuses in the United States. Students at Oberlin College in Ohio helped to design a more sustainable environmental studies building powered by solar panels, which produce 30% more electricity than the build-
ing uses. At Northland College in the state of Wisconsin, students helped to design a “green” residence hall that features a large wind generator, panels of solar cells, furniture made from recycled materials, and waterless, composting toilets. Also, a wind turbine at Minnesota’s Carleton College generates 40% of the school’s electricity. New York University gets all of the electricity it uses from wind power. Fueled largely by student pressure, many colleges and universities are integrating sustainability into their institutional cultures. In 2008, Arizona State University opened the country’s first School of Sustainability, which employs more than 60 faculty members from more than 40 disciplines. Most U.S. business schools now require students to take at least one course with an emphasis on sustainability, ethics, or corporate and social responsibility.
14-6 How Can We Improve
Global Environmental Security? ▲
Global environmental security is necessary for economic security and is at least as important as national security.
C O NC EPT 14-6
Why Is Global Environmental Security Important? Countries are legitimately concerned with national security and economic security. However, ecologists and many economists point out that all economies are supported by the earth’s natural capital (see Figure 1-3, p. 8). Thus, environmental security, economic security, and national security are interrelated (Concept 14-6). According to environmental expert Norman Myers, If a nation’s environmental foundations are degraded or depleted, its economy may well decline, its social fabric deteriorate, and its political structure become destabilized as growing numbers of people seek to sustain themselves from declining resource stocks. Thus, national security is no longer about fighting forces and weaponry alone. It relates increasingly to watersheds, croplands, forests, genetic resources, climate, and other factors that, taken together, are as crucial to a nation’s security as are military factors. Some analysts call for all countries to make environmental security a major focus of diplomacy and government policy at all levels. This perspective would be implemented by a council of advisers made up of highly qualified experts in environmental, economic, and mili-
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tary security who would integrate all three security concerns in making major decisions. HOW WOULD YOU VOTE?
✓ ■
Is environmental security just as important as economic and national security? Cast your vote online at www.cengage .com/login.
We Can Develop Stronger International Environmental Policies A number of international environmental organizations help to shape and set global environmental policy. Perhaps the most influential is the United Nations, which houses a large family of organizations including the UN Environment Programme (UNEP), the World Health Organization (WHO), the UN Development Programme (UNDP), and the Food and Agriculture Organization (FAO). Other organizations that make or influence environmental decisions are the World Bank, the Global Environment Facility (GEF), and the World Conservation Union (also known as the IUCN). Despite their
Economics, Politics, Worldviews, and Sustainability
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Figure 14-13 There is good and bad news about international efforts to deal with global environmental problems. Questions: What single piece of good news and what single piece of bad news do you think are the most important? Why?
Trade-Offs Global Efforts to Solve Environmental Problems Good N ew s
B ad N ew s
Over 500 international environmental treaties and agreements
Most international environmental treaties lack criteria for evaluating their effectiveness
UN Environment Programme negotiates and monitors environmental treaties
1992 Rio Earth Summit led to nonbinding agreements, inadequate funding, and little improvement in major problems by 2010
1992 Rio Earth Summit adopted principles for handling global environmental problems 2002 Johannesburg Earth Summit tried to implement 1992 Rio summit policies and goals
2002 Johannesburg Earth Summit failed to deal with climate change, biodiversity loss, and poverty 2009 Copenhagen conference failed to deal with projected climate change
often limited funding, these and other organizations have played important roles in: •
expanding understanding of environmental issues;
•
gathering and evaluating environmental data;
•
developing and monitoring international environmental treaties;
•
providing grants and loans for sustainable economic development and for reducing poverty; and
•
helping more than 100 nations to develop environmental laws and institutions.
Since the 1972 UN Conference on the Human Environment in Stockholm, Sweden, progress has been made in addressing environmental issues at the global level. The conference also created the UNEP to help develop the global environmental agenda. But it is a small and underfunded agency. In 1992, governments of more than 178 nations and hundreds of NGOs met at the UN Conference on Environment and Development (UNCED) in Rio de Janeiro, Brazil. The major policy outcome of this conference was Agenda 21, a global agenda for sustainable development in the 21st century, which was adopted by 178 governments, but not including the United States. This ambitious agenda established goals for addressing the world’s social, economic, and environmental problems.
Figure 14-13 lists some of the good and bad news about international efforts to deal with global environmental problems such as poverty, climate change, biodiversity loss, and ocean pollution. The primary focus of the international community on environmental problems has been the development of various international environmental laws and nonbinding policy declarations called conventions. There are more than 500 international environmental treaties and agreements—known as multilateral environmental agreements (MEAs). To date, the Montreal and Copenhagen Protocols for protecting the ozone layer (see Chapter 12, p. 271) are the most successful examples of how the global community can work together to deal with a serious global environmental challenge. Figure 14-14 lists some major problems with MEAs and solutions to these problems. In 2008, environmental leader Gus Speth argued that global environmental problems are getting worse and that international efforts to solve them are inadequate. This analysis was confirmed by the 2006 Global Governance Initiative Report, which gave the world’s governments and businesses a score of 2 out of 10 in dealing with environmental issues. Speth and other environmental leaders propose the creation of a World Environmental Organization, on the order of the World Health Organization and the World Trade Organization, to deal with global environmental challenges.
Solutions International Environmental Treaties P r ob l ems
Sol ut ions
Take a long time to develop and require full consensus
Stop requiring full consensus among participating parties
Lack of funding and poor monitoring and enforcement
Improve procedures and funding for monitoring and enforcement
Not integrated with one another
Integrate existing agreements
Figure 14-14 Global outlook: These are some major problems with global environmental treaties and agreements, as well as some solutions to these problems. Questions: Which problem and which solution do you think are the most important? Why?
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14-7 What Are Some Major Environmental Worldviews? ▲
C O NC EPT 14-7 Major environmental worldviews differ over which is more important—human needs and wants or the overall health of ecosystems and the biosphere.
There Are a Variety of Environmental Worldviews
and wants of people; others are life-centered, focusing on individual species, the entire biosphere, or some level in between.
People disagree on how serious different environmental problems are and what we should do about them. These conflicts arise mostly out of differing environmental worldviews—how people think the world works and what they believe their role in the world should be. Part of an environmental worldview is determined by a person’s environmental ethics—what one believes about what is right and what is wrong in our behavior toward the environment. Worldviews can lead to beliefs, behavior, and lifestyles that can work for or against achieving environmental sustainability. People with widely differing environmental worldviews can consider the same data and observations and arrive at quite different conclusions because they start with different assumptions and values. Figure 14-15 summarizes the four major beliefs of each of three major environmental worldviews. There are many different environmental worldviews. Some are human-centered, focusing on the needs
Most People Have Human-Centered Environmental Worldviews One human-centered worldview held by many people is the planetary management worldview. The left column in Figure 14-15 summarizes the major beliefs of this worldview. According to this view, we humans are the planet’s most important and dominant species, and we can and should manage the earth mostly for our own benefit. Other species and parts of nature are seen as having only instrumental value based on how useful they are to us. Another largely human-centered environmental worldview is the stewardship worldview. It assumes that we have an ethical responsibility to be caring and responsible managers, or stewards, of the earth. The
Environmental Worldviews
Pl a ne t a r y M a n a ge m e n t We are apart from the rest of nature and can manage nature to meet our increasing needs and wants. Because of our ingenuity and technology, we will not run out of resources. The potential for economic growth is essentially unlimited. Our success depends on how well we manage the earth's lifesupport systems mostly for our benefit.
St ewa rdship
Environm e n t al Wisdo m
We have an ethical responsibility to be caring managers, or stewards, of the earth.
We are a part of and totally dependent on nature, and nature exists for all species.
We will probably not run out of resources, but they should not be wasted.
Resources are limited and should not be wasted.
We should encourage environmentally beneficial forms of economic growth and discourage environmentally harmful forms. Our success depends on how well we manage the earth's lifesupport systems for our benefit and for the rest of nature.
We should encourage earthsustaining forms of economic growth and discourage earthdegrading forms. Our success depends on learning how nature sustains itself and integrating such lessons from nature into the ways we think and act.
Figure 14-15 This is a comparison of three major environmental worldviews (Concept 14-7). Questions: Which of these descriptions most closely fits your worldview? Which of them most closely fits the worldviews of your parents?
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Economics, Politics, Worldviews, and Sustainability
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center column in Figure 14-15 summarizes the major beliefs of this worldview. According to the stewardship view, as we use the earth’s natural capital, we are borrowing from the earth and from future generations. We have an ethical responsibility to pay this debt by leaving the earth in at least as good a condition as what we now enjoy. When thinking about our responsibility toward future generations, some analysts suggest we consider the wisdom expressed in a law of the 18th-century Iroquois Six Nations Confederacy of Native Americans: In our every deliberation, we must consider the impact of our decisions on the next seven generations. Some people believe any human-centered worldview will eventually fail because it wrongly assumes we now have or can gain enough knowledge to become effective managers or stewards of the earth. Critics of human-centered worldviews point out that we do not even know how many plant and animal species live on the earth, much less what their roles are and how they interact with one another and their nonliving environment.
Some People Have LifeCentered and Earth-Centered Environmental Worldviews Critics of human-centered environmental worldviews argue that they should be expanded to recognize that all forms of life have intrinsic value as participating members
of the biosphere, regardless of their potential or actual use to humans. Most people with a life-centered worldview believe we have an ethical responsibility to avoid causing the premature extinction of species through our activities, for two reasons. First, each species is a unique storehouse of genetic information that should be respected and protected simply because it exists (intrinsic value). Second, each species has potential economic benefit for human use (instrumental value). One earth-centered worldview is called the environmental wisdom worldview. The right column in Figure 14-15 summarizes its major beliefs. According to this view, we are within and part of—not apart from— the community of life and the ecological processes that sustain all life. This worldview suggests that the earth does not need us to manage it in order for it to survive, whereas we need the earth for our survival. From this perspective, talk about saving the earth is nonsense, because the earth does not need saving. What we do need to save is the existence of our own species and cultures, which have been around for less than an eyeblink of the 3.5-billion-year history of life on the earth, as well as that of the many other species that may become extinct because of our activities. HOW WOULD YOU VOTE?
✓ ■
Which one of the following comes closest to your environmental worldview: planetary management, stewardship, or environmental wisdom? Cast your vote online at www .cengage.com/login.
14-8 How Can We Live More Sustainably? ▲
We can live more sustainably by becoming environmentally literate, learning from nature, living more simply and lightly on the earth, and becoming active environmental citizens.
CONC EPT 14-8
We Can Become More Environmentally Literate There is widespread evidence and agreement that we are a species in the process of degrading our own lifesupport system at an increasing rate, and that during this century, this behavior will very likely threaten human civilization and the existence of up to half of the world’s species. Part of the problem stems from our ignorance about how nature works, what we are doing to its life-sustaining systems, and how we can change our behavior toward the earth. Correcting this begins by understanding three important ideas that form the foundation of environmental literacy:
1. Natural capital matters because it supports the earth’s life and human economies. 2. Our ecological footprints are immense and are expanding rapidly; in fact, they already exceed the earth’s estimated ecological capacity (see Figure 1-6, p. 13). 3. Ecological and climate-change tipping points are irreversible and should never be crossed. Once we cross such a point, neither money nor technology can save us from the resulting consequences, which could last for thousands of years. Based on such a foundation, acquiring environmental literacy involves being able to answer certain key questions and having a basic understanding of certain key topics, as summarized in Figure 14-16 (p. 324).
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Question s to a n sw e r How does life on earth sustain itself? How am I connected to the earth and other living things? Where do the things I consume come from and where do they go after I use them? What is environmental wisdom? What is my environmental worldview? What is my environmental responsibility as a human being?
Com pone n ts Basic concepts: sustainability, natural capital, exponential growth, carrying capacity Three principles of sustainablility Environmental history The two laws of thermodynamics and the law of conservation of matter Basic principles of ecology: food webs, nutrient cycling, biodiversity, ecological succession Population dynamics Sustainable agriculture and forestry
standing under the stars, sitting in a forest, or taking in the majesty and power of the sea. We might pick up a handful of soil and try to sense the teeming microscopic life within it that helps to keep us alive. We might look at a tree, mountain, rock, or bee, or listen to the sound of a bird and try to sense how each of them is connected to us and we to them through the earth’s life-sustaining processes. Some psychologists believe that, consciously or unconsciously, we spend much of our lives searching for roots—something to anchor us in a bewildering and frightening sea of change. As philosopher Simone Weil observed, “To be rooted is perhaps the most important and least recognized need of the human soul.” Earth-focused philosophers say that to be rooted, each of us needs to find a sense of place by getting to know a stream, a mountain, a yard, a neighborhood lot, or any piece of the earth with which we feel as one, as a place we know, experience emotionally, and love. When we become part of a place, it becomes a part of us. In finding and experiencing a sense of place, we might discover and tap into what conservationist Aldo Leopold (Individuals Matter, p. 325) called “the green fire that burns in our hearts,” and develop a passion for using this energy as a force for respecting and working with the earth and with one another.
Soil conservation Sustainable water use Nonrenewable mineral resources Nonrenewable and renewable energy resources Climate disruption and ozone depletion Pollution prevention and waste reduction Environmentally sustainable economic and political systems Environmental worldviews and ethics
Figure 14-16 Achieving environmental literacy involves being able to answer certain questions and having an understanding of certain key topics (Concept 14-8). Question: After taking this course, do you feel that you can answer the questions asked here and that you have a basic understanding of each of the key topics listed in this figure? Explain.
We Can Live More Simply and Lightly on the Earth Many analysts urge people who have a habit of consuming excessively to learn how to live more simply and sustainably. Seeking happiness through the pursuit of material things is considered folly by almost every major religion and philosophy. Yet mass-market advertising persistently and effectively encourages people to buy more and more things to fill a growing list of wants and imagined needs, presumably as a way to achieve happiness. Some affluent people in more-developed countries are adopting a lifestyle of voluntary simplicity, in which they seek to learn how to live with fewer material possessions and to use products and services that have a smaller environmental impact (Concept 14-8). Voluntary simplicity applies Mahatma Gandhi’s principle of enoughness:
Can We Learn from the Earth? Formal environmental education is important, but is it enough? Many analysts say no. They call for us to appreciate not just the economic value of nature, but also its ecological, aesthetic, and spiritual values. To these analysts, the problem is not just a lack of environmental literacy but also, for many people, a lack of intimate contact with nature and little understanding of how nature works and sustains us. These thinkers suggest that we kindle a sense of awe, wonder, mystery, excitement, and humility by
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The earth provides enough to satisfy every person’s need but not every person’s greed. When we take more than we need, we are simply taking from each other, borrowing from the future, or destroying the environment and other species. Most of the world’s major religions have similar teachings: “You cannot be the slave both of God and money.” (Christianity: Matthew 6:24); “Eat and drink, but waste not by excess.” (Islam: Qur’an 7.31); “One should abstain from acquisitiveness.” (Hinduism: Aca-
Economics, Politics, Worldviews, and Sustainability
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I ND I VI D UALS M ATTE R Aldo Leopold’s Environmental Ethics
A
ccording to Aldo Leopold, the renowned American forester, ecologist, and writer, the role of the human species should be to protect nature, not to conquer it. In 1933, Leopold became a professor at the University of Wisconsin (USA) and in 1935, he helped to found the U.S. Wilderness Society. Through his writings and teachings, he became one of the foremost leaders of the conservation and environmental movements during the 20th century. His energy and foresight helped to lay the critical groundwork for the field of environmental ethics. Leopold’s weekends of planting trees, hiking, and observing nature firsthand on his Wisconsin farm provided much of the material for the environmental classic A Sand
County Almanac. The following quotations from his writings reflect Leopold’s land ethic, and they form the basis for many of the beliefs and principles of the modern stewardship and environmental wisdom worldviews: • All ethics so far evolved rest upon a single premise: that the individual is a member of a community of interdependent parts. • To keep every cog and wheel is the first precaution of intelligent tinkering. • That land is a community is the basic concept of ecology, but that land is to be loved and respected is an extension of ethics. • The land ethic changes the role of Homo sapiens from conqueror of the land-
rangasutra 2.114–19); “He who knows he has enough is rich.” (Taoism: Tao Te Ching, Chapter 33) Living more lightly starts with asking this question: How much is enough? This is not an easy question to answer. People in affluent societies are conditioned to want more and more material possessions. Thus, as a result of a lifetime of exposure to commercial advertising, they often think of such wants as needs. Throughout this text, you have encountered lists of steps we can take to reduce the size and impact of our ecological footprints on the earth. It would be difficult for the majority of us to do all or even most of these things. So which ones are the most important? The human activities that have the greatest harmful impacts on the environment are food production, transportation, home energy use, and overall resource use. Based on this fact, Figure 14-17 (p. 326) lists the sustainability eight— eight key ways in which some people are choosing to live more simply.
How Can We Become Better Environmental Citizens? In the end, the answer to this question comes down to what each of us does to help make the earth a better place to live for current and future generations, for other species, and for the ecosystems that support us. Some suggest that we move beyond blame, guilt, fear, and apathy by recognizing and avoiding the following two common mental traps that lead to denial, indifference, and inaction: •
Gloom-and-doom pessimism (it is hopeless)
•
Blind technological optimism (science and technofixes will save us)
community to plain member and citizen of it. • We abuse land because we regard it as a commodity belonging to us. When we see land as a community to which we belong, we may begin to use it with love and respect. • A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise. Critical Thinking With which of the quotations above do you agree? Which, if any, of these ethical principles do you put into practice in your own life?
Avoiding these traps helps us to hold on to, and be inspired by, empowering feelings of realistic hope, rather than to be immobilized by feelings of despair and fear. Here is what business entrepreneur and environmental writer Paul Hawken told the 2009 graduating class at the University of Portland in the U.S. state of Oregon: When asked if I am pessimistic or optimistic about the future, my answer is always the same: If you look at the science about what is happening on the earth and aren’t pessimistic, you don’t understand the data. But if you meet the people who are working to restore this earth and the lives of the poor, and you aren’t optimistic, you haven’t got a pulse. . . . You join a multitude of caring people. . . . This is your century. Take it and run as if your life depends on it. It is important to recognize that there is no single correct or best solution to each of the environmental problems we face. Indeed, one of nature’s three principles of sustainability (back cover) holds that preserving diversity—in this case, being flexible and adaptable in trying a variety of cultural and technological solutions to our environmental problems—is the best way to adapt to the earth’s largely unpredictable, ever-changing conditions. Finally, we should have fun and take time GOOD to enjoy life. Laugh every day and enjoy and NEWS celebrate nature, beauty, connectedness, friendship, and love. This can empower us to become good earth citizens who practice good earthkeeping. As Mahatma Gandhi reminded us, “Power based on love is a thousand times more effective and permanent than power derived from fear.” CONCEPT 14-8
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F ood R ed uc e meat c ons um p t ion B uy or g r ow org a ni c f ood and b uy l oc al l y g rown f ood
T r ans p or t at i on R ed uc e c ar us e b y wa lking , b i k i ng , c ar p ool i ng , c a r-s ha ring , and us i ng mas s t ra ns it D r i ve an ener g y - e f fi c i e nt v e hic le
H ome Ener g y U s e I ns ul at e y our h ous e , p lug a ir l eak s , and i ns ta l l e ne rg yef fi c i ent w i nd ows U s e ener g y - ef fi c i e nt he a t ing a nd c ool i ng s y s t ems , l i g ht s , a nd ap p l i anc es
E A RT EA RTH
R es our c e U s e R ed uc e, r eus e, re c y c l e , c omp os t , r ep l a nt , a nd s ha re U s e r enew ab l e e ne rg y re s ourc e s w henever p os s i b l e
Figure 14-17 The sustainability eight is a list of eight ways in which people can live more lightly on the earth (Concept 14-8). Questions: Which of these things do you already do? Which, if any, do you hope to do?
Current Emphasis
Sustainability Emphasis
Energy and Climate Fossil fuels
Direct and indirect solar energy
Energy waste
Energy efficiency
Climate disruption
Climate stabilization
Matter High resource use and waste
Less resource use
Consume and throwaway
Reduce, reuse, and recycle
Waste disposal and pollution control
Waste prevention and pollution prevention
Life Deplete and degrade natural capital
Protect natural capital
Reduce biodiversity
Protect biodiversity
Population growth
Population stabilization
Figure 14-18 Solutions: These are some of the cultural shifts in emphasis that will be necessary to bring about the environmental or sustainability revolution. Questions: Which three of these shifts do you think are most important? Why?
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A Vision for Sustainability We believe that a hopeful and promising future is attainable, probably within your lifetime. The Industrial Revolution was a remarkable global transformation that has taken place over the past 275 years. Now in this century, environmental leaders say it is time for another sort of global transformation—an environmental or sustainability revolution. Figure 14-18 lists some of the major cultural shifts in emphasis that we will need to make in order to bring about such an environmental revolution. We can use the incredible power of exponential growth to help us bring about a sustainability revolution. Recall that if you could fold a piece of paper in half 50 times (see Chapter 1, p. 15), you would wind up with a stack of paper almost high enough to reach the sun—some 149 million kilometers (93 million miles) away. We can use the power of exponential growth to promote more sustainable environmental, social, economic, and technological changes at an exhilarating speed (Figure 14-19). History shows that we can change faster than GOOD we might think, once we have the courage to NEWS
Economics, Politics, Worldviews, and Sustainability
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Change
Environmental Concerns
Social Trends
Economic Tools
Technologies
Protecting natural capital Sustaining biodiversity Repairing ecological damage Addressing climate change
Reducing waste Using less Living more simply Reusing and recycling Growth of ecocities and eco-neighborhoods Environmental justice Environmental literacy
Full-cost pricing Micro-lending Green subsidies Green taxes Net energy analysis
Pollution prevention Organic farming Drip irrigation Solar desalinization Energy efficiency Solar energy Wind energy Geothermal energy Environmental nanotechnology Eco-industrial parks
Time Figure 14-19 Change can occur very rapidly. Using the astonishing power of exponential growth, we could bring about a sustainability revolution in a very short time. Exponential growth starts off slowly, as shown by the curve, but at some point it increases at a very rapid rate and heads sharply upward. Listed below this curve are some concerns, trends, tools, and technologies that could all be part of a major shift toward a more sustainable world within your lifetime. Questions: Which two items in each of these four categories do you believe are the most important to promote? Why? What other items would you add to this list? Explain.
leave behind ideas and practices that no longer work and to nurture new ideas for positive change. We can no longer afford to make big mistakes in our treatment of planet Earth, because as biodiversity expert Edward O. Wilson points out, there is only “One Earth. One Experiment.” Some say that making this shift is idealistic and unrealistic. Others say that it is idealistic, unrealistic, and dangerous to keep assuming that our present course is sustainable, and they warn that we have precious little time to change. As Irish playwright George Bernard Shaw (1856–1950) wrote, “I dream things that never were; and I say, ‘Why not?’” If certain individuals had not had the courage to forge ahead with ideas that others called idealistic and unrealistic, very few of the human achievements that we now celebrate would have come to pass.
Revisiting the Principles of Sustainability Shifting to eco-economies by applying the three principles of sustainability (see back cover) and using the strategies listed in Figure 14-7 over the next several decades will result in a new reuse,
reduce, and recycle economy powered by a diversity of solar and other renewable energy resources. This new economy will also have a diverse transportation system that relies more on rail, buses, and bicycles, and less on cars. Making this shift will require bold leadership by business leaders and elected officials, as well as bottomup political pressure from informed and concerned citizens. We can also guide policymaking by applying the three principles of sustainability. Because environmental and social problems are interrelated, their solutions also are interrelated. For example, relying on solar and other renewable energy sources reduces oil and coal use, but also reduces air pollution and greenhouse gas emissions, thus helping to slow climate change and protect biodiversity. Finally, whatever our worldviews are, we must understand that our lives and societies depend on natural capital and that one of the biggest threats to our ways of life is our active role in natural capital degradation. With that understanding, we can begin the search for solutions to difficult environmental problems. Competing interests working together to find the solutions must make trade-offs because this is the essence of the political process. And throughout this whole process of reaching understanding, it is important to note that individuals
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matter. Virtually all of the environmental progress made during the last few decades occurred because individuals came together to insist that we can do better. This journey begins in your own community and with your own lifestyle, because in the final analysis, all sustainability is local. This is the meaning of the motto, “Think globally, act locally.” In working to make the earth a better and more sustainable place to live, we should be guided by George Bernard Shaw’s reminder that “indifference is the essence of inhumanity” and by historian Arnold Toynbee’s observation: “If you make the world ever so little better, you will have done splendidly, and your life will have been worthwhile.”
Here are this chapter’s three big ideas: ■ Making a transition to more sustainable economies will require finding ways to estimate and include the harmful environmental and health costs of producing goods and services in their market prices. ■ An important outcome of the political process is environmental policy, and individuals can work with each other to become part of political processes that influence environmental policies. (Individuals matter.) ■ We need to become more environmentally literate about how the earth works, how we are affecting its life-support systems that keep us and other species alive, and what we can do to live more sustainably.
We have an economy that tells us that it is cheaper to degrade our life support system than to renew, restore, and sustain it. . . . Working for the earth is not a way to get rich, it is a way to be rich. PAUL HAWKEN
REVIEW 1. Review the Key Questions and Concepts for this chapter on p. 302. What is an economic system? Distinguish among natural capital, human capital (human resources), and manufactured capital (manufactured resources). What is a high-throughput economy? Compare how neoclassical economists and ecological and environmental economists view economic systems. List eight strategies that ecological and environmental economists would use to make the transition to more sustainable eco-economies. 2. What is the genuine progress indicator (GPI) and how does it differ from the gross domestic product (GDP) economic indicator? What is full-cost pricing and what are some benefits of using it to determine the market values of goods and services? Give three reasons why it is not widely used. 3. Describe the benefits of shifting from environmentally unsustainable to more environmentally sustainable government subsidies and tax breaks. Describe the proposal to tax pollution and wastes instead of wages and profits. What is the cap-and-trade approach to implementing environmental regulation? What are some environmental benefits of selling services instead of goods? Give two examples of this approach. Describe Ray Anderson’s attempts to develop a more environmentally sustainable carpet business. 4. What is poverty and how is it related to population growth and environmental degradation? List three ways
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in which government can help reduce poverty. What are the advantages of making microloans to the poor? 5. What is a matter recycling and reuse economy? Describe a low-throughput (low-waste) economy. List six tools we can use to shift to more environmentally sustainable economies. 6. What is a democracy? Describe two features of democratic governments that hinder their ability to deal with environmental problems. What is environmental policy? Describe seven principles that decision makers can use in making environmental policy. Explain why developing environmental policy is a difficult and controversial process. What are four major types of public lands in the United States? Describe the controversy over managing these lands. Describe the controversy over logging in U.S. National Forests. Describe efforts to weaken U.S. environmental laws and regulations. 7. Describe five ways in which individuals in democracies can help to develop and change environmental policy. What are four ways to provide environmental leadership? Describe the roles of grassroots and mainstream environmental organizations and give an example of each type of organization. Give two examples of successful roles that students have played in improving environmental quality. 8. Explain the importance of global environmental security relative to economic and military security. List two pieces of good news and two pieces of bad news about international efforts to deal with global environmental problems.
Economics, Politics, Worldviews, and Sustainability
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9. What is an environmental worldview? What are environmental ethics? Distinguish among the following environmental worldviews: planetary management, stewardship, and environmental wisdom. List eight goals for a person seeking environmental literacy. List four questions that lie at the heart of environmental literacy. Describe the environmental worldview of Aldo Leopold.
10. What is your understanding of the relationship between owning things and happiness? What is voluntary simplicity? What are our basic needs? List eight ways in which people can live more lightly on the earth. List seven components of an environmental or sustainability revolution. Note: Key terms are in bold type.
CRITICAL THINKING 1. Should we attempt to maximize economic growth by producing and consuming more and more economic goods and services? Explain. What are the alternatives? 2. According to one definition, sustainable development involves meeting the needs of the present human generation without compromising the ability of future generations to meet their needs. What do you believe are the needs referred to in this definition? Compare this definition with the characteristics of environmentally sustainable economic development described in Figure 14-7. 3. Suppose that over the next 20 years, the environmental and health costs of goods and services are internalized until market prices reflect the total costs of these goods and services. What harmful and what beneficial effects might such full-cost pricing have on your lifestyle? 4. Explain why you agree or disagree with the proposals that various analysts have made for sharply reducing poverty, as discussed on p. 309. Which two of these proposals do you believe are the most important? 5. Assume that you are the dictator of a large nation such as Brazil, the United States, or China. Write a five-point outline of your environmental policy. Do you think such a dictatorial policy process is better for the environment than the democratic policy-making process described in this chapter? Explain.
b. each of the five suggestions made by developers and resource extractors for managing and using U.S. public land (p. 315). 7. Government agencies can help to keep an economy going or to boost certain types of economic development by, for example, building or expanding a major highway through an undeveloped area. Proponents of such development have argued that requiring environmental impact statements as a part of governmental regulation of such projects interferes with efforts to help an economy. Do you agree? Is this a problem? Why or why not? 8. Do you believe that we have an ethical responsibility to leave the earth’s natural systems in as good a condition as they are now or better? Explain. List three aspects of your lifestyle that hinder implementing this ideal and three aspects that promote this ideal. 9. This chapter summarized several different environmental worldviews. Go through these worldviews and find the beliefs you agree with, and then describe your own environmental worldview. Which of your beliefs were added or modified as a result of taking this course? Compare your answer with those of your classmates. 10. List the five most important things that you have learned about life on earth that you would want to pass on your grandchildren.
6. Explain why you agree or disagree with a. each of the four principles that biologists and some economists have suggested for using public lands in the United States (p. 315).
LEARNING ONLINE Log on to the Student Companion Site for this book at www.cengagebrain.com/shop/ISBN/143904984X and choose Chapter 14 for many study aids and ideas for further
reading and research. These include flash cards, practice quizzing, Weblinks, information on Green Careers, and InfoTrac® College Edition articles.
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Appendix: Measurement Units (Chapters 2, 3) LENGTH
Metric–English
Metric 1 kilometer (km) = 1,000 meters (m) 1 meter (m) = 100 centimeters (cm) 1 meter (m) = 1,000 millimeters (mm) 1 centimeter (cm) = 0.01 meter (m) 1 millimeter (mm) = 0.001 meter (m)
English 1 foot (ft) = 12 inches (in) 1 yard (yd) = 3 feet (ft) 1 mile (mi) = 5,280 feet (ft) 1 nautical mile = 1.15 miles
Metric–English 1 kilometer (km) = 0.621 mile (mi) 1 meter (m) = 39.4 inches (in) 1 inch (in) = 2.54 centimeters (cm) 1 foot (ft) = 0.305 meter (m) 1 yard (yd) = 0.914 meter (m) 1 nautical mile = 1.85 kilometers (km)
AREA
1 liter (L) = 0.265 gallon (gal) 1 liter (L) = 1.06 quarts (qt) 1 liter (L) = 0.0353 cubic foot (ft3) 1 cubic meter (m3) = 35.3 cubic feet (ft3) 1 cubic meter (m3) = 1.30 cubic yards (yd3) 1 cubic kilometer (km3) = 0.24 cubic mile (mi3) 1 barrel (bbl) = 159 liters (L) 1 barrel (bbl) = 42 U.S. gallons (gal)
MASS Metric 1 kilogram (kg) = 1,000 grams (g) 1 gram (g) = 1,000 milligrams (mg) 1 gram (g) = 1,000,000 micrograms (μg) 1 milligram (mg) = 0.001 gram (g) 1 microgram (μg) = 0.000001 gram (g) 1 metric ton (mt) = 1,000 kilograms (kg)
English 1 ton (t) = 2,000 pounds (lb) 1 pound (lb) = 16 ounces (oz)
Metric–English
Metric 1 square kilometer (km2) = 1,000,000 square meters (m2) 1 square meter (m2) = 1,000,000 square millimeters (mm2) 1 hectare (ha) = 10,000 square meters (m2) 1 hectare (ha) = 0.01 square kilometer (km2)
1 metric ton (mt) = 2,200 pounds (lb) = 1.1 tons (t) 1 kilogram (kg) = 2.20 pounds (lb) 1 pound (lb) = 454 grams (g) 1 gram (g) = 0.035 ounce (oz)
English
ENERGY AND POWER
1 square foot (ft2) = 144 square inches (in2) 1 square yard (yd2) = 9 square feet (ft2) 1 square mile (mi2) = 27,880,000 square feet (ft2) 1 acre (ac) = 43,560 square feet (ft2)
Metric
Metric–English
Metric–English
1 hectare (ha) = 2.471 acres (ac) 1 square kilometer (km2) = 0.386 square mile (mi2) 1 square meter (m2) = 1.196 square yards (yd2) 1 square meter (m2) = 10.76 square feet (ft2) 1 square centimeter (cm2) = 0.155 square inch (in2)
VOLUME Metric 1 cubic kilometer (km3) = 1,000,000,000 cubic meters (m3) 1 cubic meter (m3) = 1,000,000 cubic centimeters (cm3) 1 liter (L) = 1,000 milliliters (mL) = 1,000 cubic centimeters (cm3) 1 milliliter (mL) = 0.001 liter (L) 1 milliliter (mL) = 1 cubic centimeter (cm3)
1 kilojoule (kJ) = 1,000 joules (J) 1 kilocalorie (kcal) = 1,000 calories (cal) 1 calorie (cal) = 4.184 joules (J) 1 kilojoule (kJ) = 0.949 British thermal unit (Btu) 1 kilojoule (kJ) = 0.000278 kilowatt-hour (kW-h) 1 kilocalorie (kcal) = 3.97 British thermal units (Btu) 1 kilocalorie (kcal) = 0.00116 kilowatt-hour (kW-h) 1 kilowatt-hour (kW-h) = 860 kilocalories (kcal) 1 kilowatt-hour (kW-h) = 3,400 British thermal units (Btu) 1 quad (Q) = 1,050,000,000,000,000 kilojoules (kJ) 1 quad (Q) = 293,000,000,000 kilowatt-hours (kW-h)
Temperature Conversions Fahrenheit (°F) to Celsius (°C): °C = (°F – 32.0) ÷ 1.80 Celsius (°C) to Fahrenheit (°F): °F = (°C × 1.80) + 32.0
English 1 gallon (gal) = 4 quarts (qt) 1 quart (qt) = 2 pints (pt)
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APPENDIX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Glossary abiotic Nonliving. Compare biotic. acid deposition Falling of acids and acidforming compounds from the atmosphere to the earth’s surface. Acid deposition is commonly known as acid rain, a term that refers only to wet deposition of droplets of acids and acid-forming compounds. acidity Chemical characteristic that helps determine how a substance dissolved in water will interact with and affect its environment. acid rain See acid deposition. acid solution Any water solution that has more hydrogen ions (H+) than hydroxide ions (OH-); any water solution with a pH less than 7. active solar heating system Uses solar collectors to capture energy from the sun and store it as heat for space heating and water heating. Liquid or air pumped through the collectors transfers the captured heat to a storage system such as an insulated water tank or rock bed. Pumps or fans then distribute the stored heat or hot water throughout a dwelling as needed. Compare passive solar heating system. adaptation Any genetically controlled structural, physiological, or behavioral characteristic that helps an organism survive and reproduce under a given set of environmental conditions. It usually results from a beneficial mutation. See biological evolution, differential reproduction, mutation, natural selection. adaptive radiation Process in which numerous new species evolve to fill vacant and new ecological niches in changed environments, usually after a mass extinction. Typically, this takes millions of years.
agroforestry Planting trees and crops together. Compare alley cropping. air pollution One or more chemicals in high enough concentrations in the air to harm humans, other animals, vegetation, or materials. Excess heat and noise can also be considered forms of air pollution. Such chemicals or physical conditions are called air pollutants. See primary pollutant, secondary pollutant. alien species See nonnative species. alley cropping Planting of crops in strips with rows of trees or shrubs on each side. Compare agroforestry. alpha particle Positively charged matter, consisting of two neutrons and two protons that are emitted as a form of radioactivity from the nuclei of some radioisotopes. See also beta particle, gamma rays. altitude Height above sea level. Compare latitude. anaerobic respiration Form of cellular respiration in which some decomposers get the energy they need through the breakdown of glucose (or other nutrients) in the absence of oxygen. Compare aerobic respiration. animal manure Dung and urine of animals used as a form of organic fertilizer. Compare green manure. anthropocentric Human-centered. Compare biocentric. applied ecology See reconciliation ecology.
adaptive trait See adaptation.
aquaculture Growing and harvesting fish and shellfish for human use in freshwater ponds, irrigation ditches, and lakes, or in cages or fenced-in areas of coastal lagoons and estuaries. See fish farming, fish ranching.
aerobic respiration Complex process that occurs in the cells of most living organisms, in which nutrient organic molecules such as glucose (C6H12O6) combine with oxygen (O2) and produce carbon dioxide (CO2), water (H2O), and energy. Compare photosynthesis.
aquatic life zone Marine and freshwater portions of the biosphere that can support life. Examples include freshwater life zones (such as lakes and streams) and ocean or marine life zones (such as estuaries, coastlines, coral reefs, and the deep ocean).
affluence Wealth that results in high levels of consumption and the unnecessary waste of resources.
aquifer Porous, water-saturated layers of sand, gravel, or bedrock that can yield an economically significant amount of water.
affluenza Unsustainable addiction to overconsumption and materialism exhibited in the lifestyles of affluent consumers in the United States and other developed countries.
artificial selection Process in which one or more desirable genetic traits in the population of a plant or animal are selected.
age structure Percentage of the population (or number of people of each sex) at each age level in a population.
atmosphere Mass of air surrounding the earth. See stratosphere, troposphere. atom Minute unit made of subatomic particles that is the basic building block of all
chemical elements and thus all matter; the smallest unit of an element that can exist and still have the unique characteristics of that element. Compare ion, molecule. atomic number The number of protons in the nucleus of an atom. Compare mass number. atomic theory Idea that all elements are made up of atoms; the most widely accepted scientific theory in chemistry. autotroph See producer. background extinction rate Normal extinction of various species as a result of changes in local environmental conditions. Compare mass depletion, mass extinction. beta particle Swiftly moving electron emitted by the nucleus of a radioactive isotope. See also alpha particle, gamma rays. bioaccumulation Increase in the concentration of a chemical in specific organs or tissues at a level higher than would normally be expected. Compare biomagnification. biocentric Life-centered. Compare anthropocentric. biodegradable Capable of being broken down by decomposers. biodegradable pollutant Material that can be broken down into simpler substances (elements and compounds) by bacteria or other decomposers. Compare degradable pollutant, nondegradable pollutant, slowly degradable pollutant. biodiversity Variety of the earth’s species (species diversity) or life-forms, the genes they contain (genetic diversity), the variety of ecosystems in which they live (ecological diversity), and the ecosystem processes of energy flow and nutrient cycling that sustain all life (functional diversity). biodiversity hotspots Areas especially rich in plant species that are found nowhere else in the world and are in great danger of extinction. biofuel Gas or liquid fuel (such as ethyl alcohol) made from plant material (biomass). biogeochemical cycle Natural processes that recycle nutrients in various chemical forms from the nonliving environment to living organisms and then back to the nonliving environment. Examples are the carbon, oxygen, nitrogen, phosphorus, sulfur, and hydrologic cycles.
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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biological amplification See biomagnification. biological community See community. biological diversity See biodiversity. biological evolution Change in the genetic makeup of a population of a species in successive generations. If continued long enough, it can lead to the formation of a new species. Note that populations—not individuals— evolve. See also adaptation, differential reproduction, natural selection, theory of evolution. biological extinction When a species can no longer be found anywhere on earth. biomagnification Increase in concentration of DDT, PCBs, and other slowly degradable, fat-soluble chemicals in organisms at successively higher trophic levels of a food chain or web. Compare bioaccumulation. biomass Organic matter produced by plants and other photosynthetic producers; total dry weight of all living organisms that can be supported at each trophic level in a food chain or web; dry weight of all organic matter in plants and animals in an ecosystem; plant materials and animal wastes used as fuel. biome Terrestrial regions characterized by certain types of climate and inhabited by certain types of life, especially vegetation. Examples are various types of deserts, grasslands, and forests. biosphere Zone of earth where life is found. It consists of parts of the atmosphere (the troposphere), hydrosphere (mostly surface water and groundwater), and lithosphere (mostly soil and surface rocks and sediments on the bottoms of oceans and other bodies of water) where life is found. Sometimes called the ecosphere. biotic Of or about living organisms. Compare abiotic. biotic potential Maximum rate at which the population of a given species can increase when there are no limits on its rate of growth. See environmental resistance. birth rate See crude birth rate. carbon capture and storage (CCS) Strategy for dealing with carbon in the atmosphere in which CO2 is removed from exhausts coming out of the smokestack of a coal-burning power or industrial plant and stored somewhere, such as underground in an abandoned mine. carbon cycle Cyclic movement of carbon in different chemical forms from the environment to organisms and then back to the environment. carcinogen Chemicals, ionizing radiation, and viruses that cause or promote the development of cancer. See cancer. Compare mutagen, teratogen. carnivore Animal that feeds on other animals. Compare herbivore, omnivore. carrying capacity (K) Maximum population of a particular species that a given habitat can support over a given period of time.
G2
CCS See carbon capture and storage. cell Smallest living unit of an organism. Each cell is encased in an outer membrane or wall and contains genetic material (DNA) and other parts to perform its life function. Organisms such as bacteria consist of only one cell, but most of the organisms we are familiar with contain many cells. CFCs See chlorofluorocarbons. chain reaction Multiple nuclear fissions, taking place within a certain mass of a fissionable isotope, which release an enormous amount of energy in a short time. chemical change A change in the arrangement of atoms or ions within molecules of a substance. Compare nuclear change, physical change. chemical formula Shorthand way to show the number of atoms (or ions) in the basic structural unit of a compound. Examples are H2O, NaCl, and C6H12O6. chemical reaction Interaction between chemicals in which there is a chemical change, or a change in the arrangement of atoms or ions within molecules of the substances involved. chemosynthesis Process in which certain organisms (mostly specialized bacteria) extract inorganic compounds from their environment and convert them into organic nutrient compounds without the presence of sunlight. Compare photosynthesis. chlorinated hydrocarbon Organic compound made up of atoms of carbon, hydrogen, and chlorine. Examples are DDT and PCBs. chlorofluorocarbons (CFCs) Organic compounds made up of atoms of carbon, chlorine, and fluorine. An example is Freon-12 (CCl2F2), used as a refrigerant in refrigerators and air conditioners and in making plastics such as Styrofoam. Gaseous CFCs can deplete the ozone layer when they slowly rise into the stratosphere and their chlorine atoms react with ozone molecules. Use of these molecules is being phased out. chromosome A special DNA molecule containing groups of various genes and associated proteins in plant and animal cells that carry certain types of genetic information. See genes. chronic malnutrition Long-term deficient nutrition, caused by a diet that does not supply an individual with enough protein, essential fats, vitamins, minerals, and other nutrients needed for good health. Compare overnutrition, chronic undernutrition. chronic undernutrition Long-term lack of enough food to meet basic energy needs, often associated with mental retardation and stunted growth among children and susceptibility to infectious diseases among children and adults. Compare overnutrition, chronic malnutrition. clear-cutting Method of timber harvesting in which all trees in a forested area are
removed in a single cutting. Compare seed-tree cutting, selective cutting, shelterwood cutting, strip cutting. climate Physical properties of the troposphere of an area based on analysis of its weather records over a long period (at least 30 years). The two main factors determining an area’s climate are temperature, with its seasonal variations, and the amount and distribution of precipitation. Compare weather. climate change See global climate change closed-loop recycling See primary recycling. coal Solid, combustible mixture of organic compounds with 30–98% carbon by weight, mixed with various amounts of water and small amounts of sulfur and nitrogen compounds. It forms in several stages as the remains of plants are subjected to heat and pressure over millions of years. coal gasification Conversion of solid coal to synthetic natural gas (SNG). coal liquefaction Conversion of solid coal to a liquid hydrocarbon fuel such as synthetic gasoline or methanol. coastal wetland Land along a coastline, extending inland from an estuary, that is covered with saltwater all or part of the year. Examples are marshes, bays, lagoons, tidal flats, and mangrove swamps. Compare inland wetland. coastal zone Nutrient-rich, shallow part of the ocean that extends from the hightide mark on land to the edge of a shelf-like extension of continental land masses known as the continental shelf. Contains 90% of all marine species and is the site of most large commercial marine fisheries. Compare open sea. coevolution Evolution in which two or more species interact and exert selective pressures on each other that can lead each species to undergo various adaptations. See evolution, natural selection. cogeneration Production of two useful forms of energy, such as high-temperature heat or steam and electricity, from the same fuel source. combined heat and power (CHP) See cogeneration. commensalism Interaction between organisms of different species in which one type of organism benefits and the other type is neither helped nor harmed to any great degree. Compare mutualism. commercial extinction Depletion of the population of a wild species used as a resource to a level at which it is no longer profitable to harvest the species. commercial forest See tree plantation. commercial inorganic fertilizer Commercially prepared mixture of plant nutrients such as nitrates, phosphates, and potassium applied to the soil to restore fertility and increase crop yields. Compare organic fertilizer.
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
common-property resource Resource that people normally are free to use; each user can deplete or degrade the available supply. Most are renewable and are owned by no one. Examples are clean air, fish in parts of the ocean not under the control of a coastal country, migratory birds, gases of the lower atmosphere, and the ozone content of the upper atmosphere (stratosphere). See tragedy of the commons. community Populations of all species living and interacting in an area at a particular time. competition Two or more individual organisms of a single species (intraspecific competition) or two or more individuals of different species (interspecific competition) attempting to use the same scarce resources in the same ecosystem. compost Partially decomposed organic plant and animal matter that can be used as a soil conditioner or fertilizer. compound Combination of atoms, or oppositely charged ions, of two or more different elements held together by attractive forces called chemical bonds. Compare element. concentration Amount of a chemical in a particular volume or weight of air, water, soil, or other medium. consensus science See reliable science. conservation Sensible, careful, and efficient use of natural resources by humans. People with this view are called conservationists. conservation biologist Biologist who investigates human impacts on the diversity of life found on the earth (biodiversity) and develops practical plans for preserving such biodiversity. Compare conservationist, ecologist, environmentalist, environmental scientist, and preservationist. conservation biology Multidisciplinary science created to deal with the crisis of maintaining the genes, species, communities, and ecosystems that make up earth’s biological diversity. Its goals are to investigate human impacts on biodiversity and to develop practical approaches to preserving biodiversity. conservationist Person concerned with using natural areas and wildlife in ways that sustain them for current and future generations of humans and other forms of life. Compare conservation biologist, ecologist, environmentalist, environmental scientist, and preservationist. conservation-tillage farming Crop cultivation in which the soil is disturbed little (minimum-tillage farming) or not at all (no-till farming) to reduce soil erosion, lower labor costs, and save energy. Compare conventional-tillage farming. consumer Organism that cannot synthesize the organic nutrients it needs and gets its organic nutrients by feeding on the tissues of producers or of other consumers; generally divided into primary consumers (herbivores),
secondary consumers (carnivores), tertiary (higher-level) consumers, omnivores, and detritivores (decomposers and detritus feeders). In economics, one who uses economic goods or services. contour farming Plowing and planting across the changing slope of land, rather than in straight lines, to help retain water and reduce soil erosion. conventional-tillage farming Crop cultivation method in which a planting surface is made by plowing land, breaking up the exposed soil, and then smoothing the surface. Compare conservation-tillage farming. crop rotation Planting a field, or an area of a field, with different crops from year to year to reduce soil nutrient depletion. A plant such as corn, tobacco, or cotton, which removes large amounts of nitrogen from the soil, is planted one year. The next year a legume such as soybeans, which adds nitrogen to the soil, is planted. crude birth rate Annual number of live births per 1,000 people in the population of a geographic area at the midpoint of a given year. Compare crude death rate. crude death rate Annual number of deaths per 1,000 people in the population of a geographic area at the midpoint of a given year. Compare crude birth rate. crude oil Gooey liquid consisting mostly of hydrocarbon compounds and small amounts of compounds containing oxygen, sulfur, and nitrogen. Extracted from underground accumulations, it is sent to oil refineries, where it is converted to heating oil, diesel fuel, gasoline, tar, and other materials. cultural eutrophication Overnourishment of aquatic ecosystems with plant nutrients (mostly nitrates and phosphates) because of human activities such as agriculture, urbanization, and discharges from industrial plants and sewage treatment plants. See eutrophication. culture The whole of a society’s knowledge, beliefs, technology, and practices. data information collected for a specific purpose. DDT (Dichlorodiphenyltrichloroethane) Chlorinated hydrocarbon that has been widely used as a pesticide but is now banned in some countries. death rate See crude death rate. decomposer Organism that digests parts of dead organisms and cast-off fragments and wastes of living organisms by breaking down the complex organic molecules in those materials into simpler inorganic compounds and then absorbing the soluble nutrients. Producers return most of these chemicals to the soil and water for reuse. Decomposers consist of various bacteria and fungi. Compare consumer, detritivores, detritus feeder, and producer. deforestation Removal of trees from a forested area without adequate replanting.
degradable pollutant Potentially polluting chemical that is broken down completely or reduced to acceptable levels by natural physical, chemical, and biological processes. Compare biodegradable pollutant, nondegradable pollutant, slowly degradable pollutant. democracy Government by the people through their elected officials and appointed representatives. In a constitutional democracy, a constitution provides the basis of government authority and puts restraints on government power through free elections and freely expressed public opinion. demographic transition Hypothesis that countries, as they become industrialized, have declines in death rates followed by declines in birth rates. demography Study of the size, composition, and distribution of human populations and changes in these characteristics. depletion time Time it takes to use a certain fraction, usually 80%, of the known or estimated supply of a nonrenewable resource at an assumed rate of use. Finding and extracting the remaining 20% usually costs more than it is worth. desalination Purification of saltwater or brackish (slightly salty) water by removal of dissolved salts. desert Biome in which evaporation exceeds precipitation and the average amount of precipitation is less than 25 centimeters (10 inches) a year. Such areas have little vegetation or have widely spaced, mostly low vegetation. Compare forest, grassland. desertification Conversion of rangeland, rain-fed cropland, or irrigated cropland to desert-like land, with a drop in agricultural productivity of 10% or more. It usually is caused by a combination of overgrazing, soil erosion, prolonged drought, and climate change. detritivores Consumer organism, also called detritus feeder, that feeds on detritus, parts of dead organisms, and cast-off fragments and wastes of living organisms. Examples are earthworms, termites, and crabs. Compare decomposer. detritus Parts of dead organisms and castoff fragments and wastes of living organisms. detritus feeder See detritivore. developed country See more-developed country. developing country See less-developed country. differential reproduction Phenomenon in which individuals with adaptive genetic traits produce more living offspring than do individuals without such traits. See natural selection. dissolved oxygen (DO) content Amount of oxygen gas (O2) dissolved in a given volume of water at a particular temperature and pressure, often expressed as a concentration in parts of oxygen per million parts of water.
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
G3
disturbance Discrete event that disrupts an ecosystem or community. Examples of natural disturbances include fires, hurricanes, tornadoes, droughts, and floods. Examples of human-caused disturbances include deforestation, overgrazing, and plowing. DNA (deoxyribonucleic acid) Large molecules in the cells of organisms that carry genetic information in living organisms. dose Amount of a potentially harmful substance an individual ingests, inhales, or absorbs through the skin. Compare response. See dose-response curve, median lethal dose. dose-response curve Plot of data showing effects of various dosages of a toxic agent on a group of test organisms. See dose, median lethal dose, response. doubling time Time it takes (usually in years) for the quantity of something growing exponentially to double. It can be calculated by dividing the annual percentage growth rate into 70.
a rain forest and the melting of land-based glaciers.
tasks or to cause a heat transfer between two objects at different temperatures.
ecologist Biological scientist who studies relationships between living organisms and their environment. Compare conservation biologist, conservationist, environmentalist, environmental scientist, and preservationist.
energy conservation Reducing or eliminating the unnecessary waste of energy.
ecology Study of the interactions of living organisms with one another and with their nonliving environment of matter and energy; study of the structure and functions of nature. economic development Improvement of living standards by economic growth. Compare economic growth, environmentally sustainable economic development. economic growth Increase in the capacity to provide people with goods and services produced by an economy; an increase in GNI (GNP). Compare economic development, environmentally sustainable economic development.
drought Condition in which an area does not get enough water because of lower-thannormal precipitation or higher-than-normal temperatures that increase evaporation.
economic system Method that a group of people uses to choose what goods and services to produce, how to produce them, how much to produce, and how to distribute them to people. See capitalist market economic system, pure free-market economic system.
earthquake Shaking of the ground resulting from the fracturing and displacement of rock, which produces a fault, or from subsequent movement along the fault.
ecosystem Community of different species interacting with one another and with the chemical and physical factors making up its nonliving environment.
ecological diversity Variety of forests, deserts, grasslands, oceans, streams, lakes, and other biological communities interacting with one another and with their nonliving environment. See biodiversity. Compare functional diversity, genetic diversity, species diversity.
ecosystem services Natural services or natural resources that support life on the earth and are essential to the quality of human life and the functioning of the world’s economies. See natural resources.
drainage basin See watershed.
ecological efficiency Percentage of energy transferred from one trophic level to another in a food chain or web. ecological footprint Amount of biologically productive land and water needed to supply a person or a country with the renewable resources and to absorb the wastes from such resource use. It is a measure of the ecological impact of individuals and countries. ecological niche Total way of life or role of a species in an ecosystem. It includes all physical, chemical, and biological conditions a species needs to live and reproduce in an ecosystem.
electromagnetic radiation Forms of kinetic energy traveling as electromagnetic waves. Examples are radio waves, TV waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X rays, and gamma rays. electron (e) Tiny particle moving around outside the nucleus of an atom. Each electron has one unit of negative charge and almost no mass. Compare neutron, proton. element Chemical, such as hydrogen (H), iron (Fe), sodium (Na), carbon (C), nitrogen (N), or oxygen (O), whose distinctly different atoms serve as the basic building blocks of all matter. Two or more elements combine to form compounds that make up most of the world’s matter. Compare compound.
ecological restoration Process of repairing damage caused by humans to the biodiversity and dynamics of natural ecosystems.
emergent disease A disease, often caused by a virus, that has been previously unknown or absent in human populations for at least 20 years.
ecological succession Process in which communities of plant and animal species in a particular area are replaced over time by a series of different and often more complex communities. See primary ecological succession, secondary ecological succession.
endangered species Wild species with so few individual survivors that the species could soon become extinct in all or most of its natural range. Compare threatened species.
ecological tipping point A point beyond which an environmental problem causes an irreversible shift in the behavior of a natural system. Examples include the collapse of
G4
endemic species Species found in only one area. Such species are especially vulnerable to extinction. energy Capacity to do work by performing mechanical, physical, chemical, or electrical
energy efficiency Percentage of the total energy input that does useful work and is not converted into low-quality, usually useless heat in an energy conversion system or process. See energy quality, net energy. Compare material efficiency. energy quality Ability of a form of energy to do useful work. High-temperature heat and the chemical energy in fossil fuels and nuclear fuels are concentrated high-quality energy. Low-quality energy such as low-temperature heat is dispersed or diluted and cannot do much useful work. See high-quality energy, low-quality energy. environment All external conditions and factors, living and nonliving (chemicals and energy), that affect an organism or other specified system during its lifetime. environmental degradation Depletion or destruction of a potentially renewable resource such as soil, grassland, forest, or wildlife that is used faster than it is naturally replenished. If such use continues, the resource can become nonrenewable (on a human time scale) or nonexistent (extinct). See sustainable yield. environmental ethics Our beliefs about what is right or wrong environmental behavior. environmentalism Social movement dedicated to protecting the earth’s life-support systems for us and other species. environmentalist Person concerned about the impact of people on environmental quality who believes some human actions are degrading parts of the earth’s life-support systems for humans and many other forms of life. Compare conservation biologist, conservationist, ecologist, environmental scientist. environmental justice Fair treatment and meaningful involvement of all people regardless of race, color, sex, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies. environmentally sustainable economic development Development that (1) encourages environmentally sustainable forms of economic growth that meet the basic needs of the current generations of humans and other species without preventing future generations of humans and other species from meeting their basic needs and (2) discourages environmentally harmful and unsustainable forms of economic growth. It is the economic component of an environmentally sustainable society. Compare economic development, economic growth. environmentally sustainable society Society that satisfies the basic needs of its people without depleting or degrading its natural resources and thereby preventing
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
current and future generations of humans and other species from meeting their basic needs. environmental policy Consists of environmental laws, rules, and regulations developed, implemented, and enforced by one or more government agencies, along with environmental programs funded by those agencies. environmental resistance All the limiting factors that act together to limit the growth of a population. See biotic potential, limiting factor. environmental revolution Cultural change that involves continual reexamination and possibly reform of lifestyles, political and economic systems, and ways in which we treat the environment, with the goal of helping to sustain the earth for ourselves and other species. This also involves population control and working with the rest of nature by learning more about how nature sustains itself. See environmental wisdom worldview. environmental science Interdisciplinary study that uses information from the physical sciences and social sciences to learn how the earth works, how we interact with the earth, and how to deal with environmental problems. environmental scientist Scientist who uses information from the physical sciences and social sciences to understand how the earth works, learn how humans interact with the earth, and develop solutions to environmental problems. Compare conservation biologist, conservationist, preservationist, and ecologist. environmental wisdom worldview Beliefs that (1) nature exists for all the earth’s species, not just for us, and we are not in charge of the rest of nature; (2) there is not always more, and it is not all for us; (3) some forms of economic growth are beneficial and some are harmful, and our goals should be to design economic and political systems that encourage earth-sustaining forms of growth and discourage or prohibit earth-degrading forms; and (4) our success depends on learning to cooperate with one another and with the rest of nature instead of trying to dominate and manage earth’s life-support systems primarily for our own use. Compare planetary management worldview, spaceship-earth worldview. environmental worldview How people think the world works, what they think their role in the world should be, and what they believe is right and wrong environmental behavior (environmental ethics). epidemiology Study of the patterns of disease or other harmful effects from toxic exposure within defined groups of people to find out why some people get sick and some do not. erosion Process or group of processes by which loose or consolidated earth materials are dissolved, loosened, or worn away and removed from one place and deposited in another. See weathering.
estuary Partially enclosed coastal area at the mouth of a river where its freshwater, carrying fertile silt and runoff from the land, mixes with salty seawater. eutrophication Physical, chemical, and biological changes that take place after a lake, estuary, or slow-flowing stream receives inputs of plant nutrients—mostly nitrates and phosphates—from natural erosion and runoff from the surrounding land basin. See cultural eutrophication. eutrophic lake A lake with a large or excessive supply of plant nutrients, mostly nitrates and phosphates. Compare mesotrophic lake, oligotrophic lake. evaporation Movement of water molecules from the oceans, lakes, rivers, and soil into the atmosphere. evolution See biological evolution. existence value See intrinsic value. experiment Procedure a scientist uses to study some phenomenon under known conditions. Scientists conduct some experiments in the laboratory and others in nature. The resulting scientific data or facts must be verified or confirmed by repeated observations and measurements, ideally by several different investigators.
age of food, usually caused by drought, war, flood, earthquake, or other catastrophic event that disrupts food production and distribution. feedlot Confined outdoor or indoor space used to raise hundreds to thousands of domesticated livestock. Compare rangeland. fermentation See anaerobic respiration. fertility rate Number of children born to an average woman in a population during her lifetime. fertilizer Substance that adds inorganic or organic plant nutrients to soil and improves its ability to grow crops, trees, or other vegetation. See commercial inorganic fertilizer, organic fertilizer. first law of thermodynamics Whenever energy is converted from one form to another in a physical or chemical change, no energy is created or destroyed. You cannot get more energy out of something than you put in; in terms of energy quantity, you cannot get something for nothing. This law does not apply to nuclear changes, in which energy can be produced from small amounts of matter. See second law of thermodynamics. fishery Concentrations of particular aquatic species suitable for commercial harvesting in a given ocean area or inland body of water.
exponential growth Type of growth in which some quantity, such as population size or economic output, increases by a fixed percentage of the whole in a given time period; when the increase in quantity over time is plotted, this type of growth yields a curve shaped like the letter J.
floodplain Flat valley floor next to a stream channel. For legal purposes, the term often is applied to any low area that has the potential for flooding, including certain coastal areas.
external benefit Beneficial social effect of producing and using an economic good that is not included in the market price of the good. Compare external cost, full cost, and internal cost.
food insecurity Condition under which people in a given area are living with chronic hunger and poor nutrition, which threaten their ability to lead healthy and productive lives.
external cost Harmful social effect of producing and using an economic good that is not included in the market price of the good. Compare external benefit, full cost, and internal cost. externalities Social benefits (“goods”) and social costs not included in the market price of an economic good. See external benefit, external cost. Compare full cost, internal cost. extinction Complete disappearance of a species from the earth. This happens when a species cannot adapt and successfully reproduce under new environmental conditions or when it evolves into one or more new species. Compare speciation. See also endangered species, mass depletion, mass extinction, threatened species. extinction rate Percentage or number of species that go extinct within a certain time, such as a year. family planning Providing information, clinical services, and contraceptives to help people choose the number and spacing of children they want to have. famine Widespread malnutrition and starvation in a particular area because of a short-
food chain Series of organisms in which each eats or decomposes the preceding one. Compare food web.
food security Condition under which every person in a given area has daily access to enough nutritious food to have an active and healthy life. food web Complex network of many interconnected food chains and feeding relationships. Compare food chain. forest Biome with enough average annual precipitation (at least 76 centimeters, or 30 inches) to support growth of various tree species and smaller forms of vegetation. Compare desert, grassland. fossil Mineralized or petrified replica of skeletons, bones, teeth, shells, leaves, and seeds, or impressions of such items found in rocks. fossil fuel Products of partial or complete decomposition of plants and animals that occur as crude oil, coal, natural gas, or heavy oils as a result of exposure to heat and pressure in the earth’s crust over millions of years. See coal, crude oil, natural gas. foundation species Species that plays a major role in shaping communities by creating and enhancing their habitats in ways that benefit other species.
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
G5
freshwater life zones Aquatic systems where water with a dissolved salt concentration of less than 1% by volume accumulates on or flows through the surfaces of terrestrial biomes. Examples are (1) standing (lentic) bodies of freshwater such as lakes, ponds, and inland wetlands and (2) flowing (lotic) systems such as streams and rivers. Compare biome. frontier science See tentative science. Compare reliable science, unreliable science. functional diversity Biological and chemical processes or functions such as energy flow and matter cycling needed for the survival of species and biological communities. See biodiversity, ecological diversity, genetic diversity, species diversity. gamma rays Form of electromagnetic radiation with a high energy content emitted by some radioisotopes. They readily penetrate body tissues. See also alpha particle, beta particle. GDP See gross domestic product. gene pool Sum total of all genes found in the individuals of the population of a particular species. generalist species A species with a broad ecological niche. They can live in many different places, eat a variety of foods, and tolerate a wide range of environmental conditions. Examples are flies, cockroaches, mice, rats, and humans. Compare specialist species. genes Coded units of information about specific traits that are passed on from parents to offspring during reproduction. They consist of segments of DNA molecules found in chromosomes. genetic adaptation Changes in the genetic makeup of organisms of a species that allow the species to reproduce and gain a competitive advantage under changed environmental conditions. See differential reproduction, evolution, mutation, natural selection.
global warming Warming of the earth’s atmosphere as a result of increases in the concentrations of one or more greenhouse gases primarily as a result of human activities. See greenhouse effect, greenhouse gases. GNI See gross national income. grassland Biome found in interior continental regions where moderate annual average precipitation (25–76 centimeters, or 10–30 inches) is enough to support the growth of grass and small plants but not enough to support large stands of trees. Compare desert, forest. green architecture Energy-efficient and money-saving building designs using natural lighting, solar energy, recycling of wastewater, and energy-efficient appliances and lighting. greenhouse effect Natural effect that releases heat in the atmosphere (troposphere) near the earth’s surface. Water vapor, carbon dioxide, ozone, and several other gases in the lower atmosphere (troposphere) absorb some of the infrared radiation (heat) radiated by the earth’s surface. This causes their molecules to vibrate and transform the absorbed energy into longer-wavelength infrared radiation (heat) in the troposphere. If the atmospheric concentrations of these greenhouse gases rise and other natural processes do not remove them, the average temperature of the lower atmosphere will increase gradually. Compare global warming. greenhouse gases Gases in the earth’s lower atmosphere (troposphere) that cause the greenhouse effect. Examples are carbon dioxide, chlorofluorocarbons, ozone, methane, water vapor, and nitrous oxide. green manure Freshly cut or still-growing green vegetation that is plowed into the soil to increase the organic matter and humus available to support crop growth. Compare animal manure.
genetically modified organism (GMO) Organism whose genetic makeup has been modified by genetic engineering.
green revolution Popular term for introduction of scientifically bred or selected varieties of grain (rice, wheat, maize) that, with high enough inputs of fertilizer and water, can greatly increase crop yields.
genetic diversity Variability in the genetic makeup among individuals within a single species. See biodiversity. Compare ecological diversity, functional diversity, species diversity.
gross domestic product (GDP) Total market value in current dollars of all goods and services produced within a country, usually during a year. Compare gross national income.
genetic engineering Insertion of an alien gene into an organism to give it a beneficial genetic trait. Compare natural selection.
gross national income (GNI) Total market value in current dollars of all goods and services produced by an economy, usually during a year. Compare gross domestic product.
geographic isolation Physical separation of different groups of the same species for fairly long times into different areas. geosphere Consists of the earth’s intensely hot core, a thick mantle composed mostly of rock, and a thin outer crust.
gross primary productivity (GPP) Rate at which an ecosystem’s producers capture and store a given amount of chemical energy as biomass in a given length of time. Compare net primary productivity.
geothermal energy Heat transferred from the earth’s underground concentrations of dry steam (steam with no water droplets), wet steam (a mixture of steam and water droplets), or hot water trapped in fractured or porous rock.
groundwater Water that sinks into the soil and is stored in slowly flowing and slowly renewed underground reservoirs called aquifers; underground water in the zone of saturation, below the water table. Compare runoff, surface water.
G6
habitat Place or type of place where an organism or population of organisms lives. Compare ecological niche. habitat fragmentation Breakup of a habitat into smaller pieces, usually as a result of human activities. hazard Something that can cause injury, disease, economic loss, or environmental damage. See also risk. hazardous chemical A chemical that can cause harm because it is flammable or explosive, can irritate or damage the skin or lungs (such as strong acidic or alkaline substances), or can cause allergic reactions of the immune system (allergens). See also toxic chemical. hazardous (toxic) waste Any solid, liquid, or containerized gas that can catch fire easily, is corrosive to skin tissue or metals, is unstable and can explode or release toxic fumes, or has harmful concentrations of one or more toxic materials that can leach out. See also toxic waste. heat Total kinetic energy of all the randomly moving atoms, ions, or molecules within a given substance, excluding the overall motion of the whole object. Heat always flows spontaneously from a hot sample of matter to a colder sample of matter. This is one way to state the second law of thermodynamics. Compare temperature. herbicide Chemical that kills a plant or inhibits its growth. herbivore Plant-eating organism. Examples are deer, sheep, grasshoppers, and zooplankton. Compare carnivore, omnivore. heterotroph See consumer. high-level consumers See tertiary consumers. high-input agriculture See industrialized agriculture. high-quality energy Energy that is concentrated and has great ability to perform useful work. Examples are high-temperature heat and the energy in electricity, coal, oil, gasoline, sunlight, and nuclei of uranium235. Compare low-quality energy. high-quality matter Matter that is concentrated and contains a high concentration of a useful resource. Compare low-quality matter. high-throughput economy Economic system in most advanced industrialized countries in which ever-increasing economic growth is sustained by maximizing the rate at which matter and energy resources are used, with little emphasis on pollution prevention, recycling, reuse, reduction of unnecessary waste, and other forms of resource conservation. Compare low-throughput economy, matterrecycling-and-reuse economy. HIPPCO Acronym used by some conservation biologists to summarize the most important causes of premature extinction: Habitat destruction and fragmentation, Invasive (alien) species, Population growth (too many
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people consuming too many resources), Pollution, Climate change, and Over-harvesting.
of suspended solid particles. Compare photochemical smog.
host Plant or animal on which a parasite feeds.
industrial solid waste Waste produced indirectly by mines, factories, refineries, food growers, and businesses that supply people with goods and services.
human capital See human resources. human resources Physical and mental talents of people used to produce, distribute, and sell an economic good. Compare financial resources, manufactured resources, natural resources. humus Slightly soluble residue of undigested or partially decomposed organic material in topsoil. This material helps retain water and water-soluble nutrients, which can be taken up by plant roots. hunger See chronic undernutrition. hydrocarbon Organic compound of hydrogen and carbon atoms. The simplest hydrocarbon is methane (CH4), the major component of natural gas. hydroelectric power plant Structure in which the energy of falling or flowing water spins a turbine generator to produce electricity. hydrologic cycle Biogeochemical cycle that collects, purifies, and distributes the earth’s fixed supply of water from the environment to living organisms and then back to the environment. hydropower Electrical energy produced by falling or flowing water. See hydroelectric power plant. hydrosphere Earth’s (1) liquid water (oceans, lakes, other bodies of surface water, and underground water), (2) frozen water (polar ice caps, floating ice caps, and ice in soil, known as permafrost), and (3) small amounts of water vapor in the atmosphere. See also hydrologic cycle. hypereutrophic lake Lake containing excessive nutrients. igneous rock Rock formed when molten rock material (magma) wells up from the earth’s interior, cools, and solidifies into rock masses. Compare metamorphic rock, sedimentary rock. See rock cycle. immigration Migration of people into a country or area to take up permanent residence. indicator species A species that provides warnings that a community or ecosystem is being degraded. Compare keystone species, native species, nonnative species. industrialized agriculture Using large inputs of energy from fossil fuels (especially oil and natural gas), water, fertilizer, and pesticides to produce large quantities of crops and livestock for domestic and foreign sale. Compare subsistence farming, sustainable agriculture. industrial smog Type of air pollution consisting mostly of a mixture of sulfur dioxide, suspended droplets of sulfuric acid formed from some of the sulfur dioxide, and a variety
infant mortality rate Number of babies out of every 1,000 born each year that die before their first birthday. infectious disease Disease caused when a pathogen such as a bacterium, virus, or parasite invades the body and multiplies in its cells and tissues. infiltration Downward movement of water through soil. inland wetland Land away from the coast, such as a swamp, marsh, or bog, that is covered all or part of the time with fresh water. Compare coastal wetland. inorganic compounds All compounds not classified as organic compounds. See organic compounds. inorganic fertilizer See commercial inorganic fertilizer. input pollution control See pollution prevention. insecticide Chemical that kills insects. instrumental value A value assigned to components of nature based on their usefulness to humans. integrated pest management (IPM) Combined use of biological, chemical, and cultivation methods in proper sequence and timing to keep the size of a pest population below the level that causes economically unacceptable loss of a crop or livestock animal. integrated waste management Variety of strategies for both waste reduction and waste management to deal with the solid wastes. internal cost Direct cost paid by the producer and the buyer of an economic good. Compare external benefit, external cost, full cost. interspecific competition Members of two or more species trying to use the same limited resources in an ecosystem. See competition. intrinsic rate of increase (r) Rate at which a population could grow if it had unlimited resources. Compare environmental resistance. intrinsic value Value assigned to components of nature based solely on their existence, regardless of their usefulness to humans. invasive species See nonnative species. ion Atom or group of atoms with one or more positive (+) or negative (-) electrical charges. Compare atom, molecule. isotopes Two or more forms of a chemical element that have the same number of protons but different mass numbers because they have different numbers of neutrons in their nuclei.
J-shaped curve Curve with a shape similar to that of the letter J; can represent prolonged exponential growth. junk science See unreliable science. keystone species Species that play roles affecting the types and abundance of many other organisms in an ecosystem. Compare indicator species, native species, nonnative species. kinetic energy Energy that matter has because of its mass and speed or velocity. Compare potential energy. lake Large natural body of standing freshwater formed when water from precipitation, land runoff, or groundwater fills a depression in the earth. See eutrophic lake, mesotrophic lake, oligotrophic lake. landfill See sanitary landfill. land-use planning Process for deciding the best present and future use of each parcel of land in an area. latitude Distance from the equator. Compare altitude. law of conservation of energy See first law of thermodynamics. law of conservation of matter In any physical or chemical change, matter is neither created nor destroyed but merely changed from one form to another; in physical and chemical changes, existing atoms are rearranged into different spatial patterns (physical changes) or different combinations (chemical changes). law of nature See scientific law. law of tolerance Existence, abundance, and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by the species. LD50 See median lethal dose. leaching Process in which various chemicals in upper layers of soil are dissolved and carried to lower layers and, in some cases, to groundwater. less-developed country A country that has low to moderate industrialization and low to moderate per capita GNP. Most are located in Africa, Asia, and Latin America. Compare more-developed country. life-cycle cost Initial cost plus lifetime operating costs of an economic good. Compare full cost. life expectancy Average number of years a newborn infant can be expected to live. limiting factor Single factor that limits the growth, abundance, or distribution of the population of a species in an ecosystem. See limiting factor principle. limiting factor principle Too much or too little of any abiotic factor can limit or prevent growth of a population of a species in an ecosystem, even if all other factors are at or near the optimum range of tolerance for the species.
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G7
liquefied natural gas (LNG) Natural gas converted to liquid form by cooling it to a very low temperature. liquefied petroleum gas (LPG) Mixture of liquefied propane (C3H8) and butane (C4H10) gas removed from natural gas and used as a fuel. lithosphere Earth’s crust and upper mantle. logistic growth Pattern in which exponential population growth occurs when the population is small, and population growth decreases steadily with time as the population approaches the carrying capacity. See S-shaped curve. low-input agriculture See sustainable agriculture. low-quality energy Energy that is dispersed and has little ability to do useful work. An example is low-temperature heat. Compare high-quality energy. low-quality matter Matter that is dilute or dispersed, or contains a low concentration of a useful resource. Compare high-quality matter. low-throughput (low-waste) economy Economic system based on working with nature by (1) recycling and reusing discarded matter, (2) preventing pollution, (3) conserving matter and energy resources by reducing unnecessary waste and use, (4) not degrading renewable resources, (5) building things that are easy to recycle, reuse, and repair, (6) not allowing population size to exceed the carrying capacity of the environment, and (7) preserving biodiversity and ecological integrity. See environmental worldview. Compare high-throughput economy, matter-recyclingand-reuse economy. low-waste economy See low-throughput economy. LPG See liquefied petroleum gas. magma Molten rock below the earth’s surface. malnutrition Faulty nutrition, caused by a diet that does not supply an individual with enough protein, essential fats, vitamins, minerals, and other nutrients needed for good health. Compare overnutrition, undernutrition. mantle Zone of the earth’s interior between its core and its crust. See lithosphere. manufactured capital See manufactured resources. manufactured inorganic fertilizer Commercially available, water-soluble fertilizer produced from various minerals. manufactured resources Manufactured items made from natural resources and used to produce and distribute economic goods and services bought by consumers. These include tools, machinery, equipment, factory buildings, and transportation and distribution facilities. Compare financial resources, human resources, natural resources. manure See animal manure, green manure.
G8
mass Amount of material in an object. mass depletion Widespread, often global period during which extinction rates are higher than normal but not high enough to classify as a mass extinction. Compare background extinction, mass extinction. mass extinction Catastrophic, widespread, often global event in which major groups of species are wiped out over a short time compared with normal (background) extinctions. Compare background extinction, mass depletion. mass number Sum of the number of neutrons (n) and the number of protons (p) in the nucleus of an atom. It gives the approximate mass of that atom. Compare atomic number. mass transit Buses, trains, trolleys, and other forms of transportation that carry large numbers of people. material efficiency Total amount of material needed to produce each unit of goods or services. Also called resource productivity. Compare energy efficiency. matter Anything that has mass (the amount of material in an object) and takes up space. It can exist in three physical states—solid, liquid, and gas. On the earth, where gravity is present, we weigh an object to determine its mass. matter quality Measure of how useful a matter resource is, based on its availability and concentration. See high-quality matter, low-quality matter. matter recycling and reuse economy Economy that emphasizes recycling the maximum amount of all resources that can be recycled. The goal is to allow economic growth to continue without depleting matter resources and without producing excessive pollution and environmental degradation. Compare high-throughput economy, lowthroughput economy. mature community Fairly stable, selfsustaining community in an advanced stage of ecological succession; usually has a diverse array of species and ecological niches; captures and uses energy and cycles critical chemicals more efficiently than simpler, immature communities. maximum sustainable yield See sustainable yield. mesotrophic lake Lake with a moderate supply of plant nutrients. Compare eutrophic lake, oligotrophic lake. metamorphic rock Rock produced when a pre-existing rock is subjected to high temperatures (which may cause it to melt partially), high pressures, chemically active fluids, or a combination of these agents. Compare igneous rock, sedimentary rock. See rock cycle. metropolitan area See urban area. microorganisms Organisms such as bacteria that are so small they can be seen only by using a microscope.
migration Movement of people into (immigration) and out of (emigration) specific geographic areas. mineral Any naturally occurring inorganic substance found in the earth’s crust as a crystalline solid. See mineral resource. mineral resource Concentration of naturally occurring solid, liquid, or gaseous material in or on the earth’s crust in a form and amount such that extracting and converting it into useful materials or items is currently or potentially profitable. Mineral resources are classified as metallic (such as iron and tin ores) or nonmetallic (such as fossil fuels, sand, and salt). minimum-tillage farming See conservation-tillage farming. model Approximate representation or simulation of a system being studied. molecule Combination of two or more atoms of the same chemical element (such as O2) or different chemical elements (such as H2O) held together by chemical bonds. Compare atom, ion. monoculture Cultivation of a single crop, usually on a large area of land. Compare polyculture. more-developed country Country that is highly industrialized and has a high per capita GNP. Compare less-developed country. mountain Steep, or high-altitude area of land; mountains cover about one-fourth of the earth’s land surface. municipal solid waste (MSW) Solid materials discarded by homes and businesses in or near urban areas. See solid waste. mutagen Chemical or form of radiation that causes inheritable changes (mutations) in the DNA molecules in the genes found in chromosomes. See carcinogen, mutation, teratogen. mutation Random change in the structure or number of DNA molecules in a cell’s genes that offspring can inherit and can yield changes in anatomy, physiology, or behavior in offspring. See mutagen. mutualism Type of species interaction in which both participating species generally benefit. Compare commensalism. native species Species that normally live and thrive in a particular ecosystem. Compare indicator species, keystone species, nonnative species. natural capital Natural resources and natural services that keep us and other species alive and support our economies. See natural resources and natural services. natural capital degradation See environmental degradation. natural gas Underground deposits of gases consisting of 50–90% by weight methane gas (CH4) and small amounts of heavier gaseous hydrocarbon compounds such as propane (C3H8) and butane (C4H10).
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
natural greenhouse effect Heat buildup in the troposphere because of the presence of certain gases, called greenhouse gases. Without this effect, the earth would be nearly as cold as Mars, and life as we know it could not exist. Compare global warming. natural income Renewable resources such as plants, animals, and soil provided by natural capital. natural law See scientific law. natural radioactive decay Nuclear change in which unstable nuclei of atoms spontaneously shoot out particles (usually alpha or beta particles) or energy (gamma rays) at a fixed rate. natural rate of extinction See background extinction. natural recharge Process by which most aquifers are replenished naturally by precipitation that percolates downward through soil and rock. natural resources Earth’s natural materials and processes that sustain other species and humans. natural selection Process by which a particular beneficial gene (or set of genes) is reproduced in succeeding generations more than other genes. The result of natural selection is a population that contains a greater proportion of organisms better adapted to certain environmental conditions. See adaptation, biological evolution, differential reproduction, mutation. natural services Natural processes (also called ecological services) that maintain natural and other resources for humans and all other species. net energy Total amount of useful energy available from an energy resource or energy system over its lifetime, minus the amount of energy (1) used (the first energy law), (2) automatically wasted (the second energy law), and (3) unnecessarily wasted in finding, processing, concentrating, and transporting it to users. net primary productivity (NPP) Rate at which all the plants in an ecosystem produce net useful chemical energy; equal to the difference between the rate at which the plants in an ecosystem produce useful chemical energy (gross primary productivity) and the rate at which they use some of that energy through cellular respiration. Compare gross primary productivity. neutron (n) Elementary particle in the nuclei of all atoms (except hydrogen-1). It has a relative mass of 1 and no electrical charge. Compare electron, proton. niche See ecological niche. nitrogen cycle Cyclic movement of nitrogen in different chemical forms from the environment to organisms and then back to the environment. noise pollution Any unwanted, disturbing, or harmful sound that impairs or interferes
with hearing, causes stress, hampers concentration and work efficiency, or causes accidents. nondegradable pollutant Material that is not broken down by natural processes. Examples are the toxic elements lead and mercury. Compare biodegradable pollutant, degradable pollutant, slowly degradable pollutant.
process releases a large amount of energy. Compare nuclear fission. nucleus Extremely tiny center of an atom, making up most of the atom’s mass. It contains one or more positively charged protons and one or more neutrons with no electrical charge (except for a hydrogen-1 atom, which has one proton and no neutrons in its nucleus).
nonnative species Species that migrate into an ecosystem or are deliberately or accidentally introduced into an ecosystem by humans. Compare native species.
nutrient Any food, element, or compound an organism must take in to live, grow, and reproduce.
nonpoint source Broad and diffuse areas, rather than points, from which pollutants enter bodies of surface water or the air. Compare point source.
nutrient cycling Circulation of chemicals necessary for life, from the environment (mostly from soil and water) through organisms and back to the environment.
nonrenewable resource Resource that exists in a fixed amount (stock) in various places in the earth’s crust and has the potential for renewal by geological, physical, and chemical processes taking place over hundreds of millions to billions of years. Examples are copper, aluminum, coal, and oil. We classify these resources as exhaustible because we are extracting and using them at a much faster rate than they were formed. Compare renewable resource.
oil See crude oil.
nontransmissible disease Disease that is not caused by living organisms and does not spread from one person to another. Examples are most cancers, diabetes, cardiovascular disease, and malnutrition. Compare transmissible disease. no-till farming See conservation-tillage farming.
nutrient cycle See biogeochemical cycle.
ocean currents Mass movements of surface water pushed by prevailing winds blowing over the oceans. oil sand See tar sand. old-growth forest Virgin and old, regenerated second-growth forests that have not been seriously disturbed by human activities or natural disasters for 200 years or more; these forests contain trees that are often hundreds, sometimes thousands of years old. Examples include forests of Douglas fir, western hemlock, giant sequoia, and coastal redwoods in the western United States. Compare second-growth forest, tree plantation. oligotrophic lake Lake with a low supply of plant nutrients. Compare eutrophic lake, mesotrophic lake.
nuclear change Process in which nuclei of certain isotopes spontaneously change, or are forced to change, into one or more different isotopes. The three principal types of nuclear change are natural radioactivity, nuclear fission, and nuclear fusion. Compare chemical change, physical change.
omnivore Animal that can use both plants and other animals as food sources. Examples are pigs, rats, cockroaches, and humans. Compare carnivore, herbivore.
nuclear energy Energy released when atomic nuclei undergo a nuclear reaction such as the spontaneous emission of radioactivity, nuclear fission, or nuclear fusion.
open sea Part of an ocean that is beyond the continental shelf. Compare coastal zone.
nuclear fission Nuclear change in which the nuclei of certain isotopes with large mass numbers (such as uranium-235 and plutonium-239) are split apart into lighter nuclei when struck by a neutron. This process releases more neutrons and a large amount of energy. Compare nuclear fusion. nuclear fuel cycle Cycle that includes the mining of uranium, processing it to make a satisfactory fuel, using it in a reactor, and safely storing the resulting highly radioactive wastes for 10,000–240,000 years until their radioactivity falls to safe levels. nuclear fusion Nuclear change in which two nuclei of isotopes of elements with a low mass number (such as hydrogen-2 and hydrogen-3) are forced together at extremely high temperatures until they fuse to form a heavier nucleus (such as helium-4). This
open dumps Fields or holes in the ground where garbage is deposited and sometimes covered with soil.
organic agriculture Producing crops with little or no use of synthetic pesticides, synthetic fertilizers, or genetically engineered seeds, and raising livestock without the use of genetic engineering, synthetic growth regulators, or feed additives. See sustainable agriculture. organic compounds Compounds containing carbon atoms combined with each other and with atoms of one or more other elements such as hydrogen, oxygen, nitrogen, sulfur, phosphorus, chlorine, and fluorine. All other compounds are called inorganic compounds. organic farming See organic agriculture. organic fertilizer Organic material such as animal manure, green manure, and compost, applied to cropland as a source of plant nutrients. Compare commercial inorganic fertilizer. organism Any form of life.
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
G9
output pollution control See pollution cleanup. overfishing Harvesting so many fish of a species, especially immature fish, that not enough breeding stock is left to replenish the species, such that it is not profitable to harvest them. overgrazing Destruction of vegetation when too many grazing animals feed too long and exceed the carrying capacity of a rangeland or pasture area. overnutrition Diet so high in calories, saturated (animal) fats, salt, sugar, and processed foods, and so low in vegetables and fruits that the consumer runs high risks of diabetes, hypertension, heart disease, obesity, and other health hazards. Compare malnutrition, undernutrition.
used, the results of their experiments, and the reasoning behind their hypotheses for other scientists working in the same field (their peers) to examine and evaluate. per capita ecological footprint Amount of biologically productive land and water needed to supply an individual with resources and to absorb the wastes from such resource use. per capita GDP Annual gross domestic product (GDP) of a country divided by its total population. See gross domestic product. per capita GNI Annual gross national income (GNI) of a country divided by its total population at mid-year. It gives the average slice of the economic pie per person. Used to be called per capita GNP. See gross national income.
oxygen-demanding wastes Organic materials that are usually biodegraded by aerobic (oxygen-consuming) bacteria if there is enough dissolved oxygen in the water. See also dissolved oxygen content.
perpetual resource Essentially inexhaustible resource on a human time scale. Solar energy is an example. See renewable resource. Compare nonrenewable resource, renewable resource.
ozone depletion Decrease in concentration of ozone (O3) in the stratosphere. See ozone layer.
persistence How long a pollutant stays in the air, water, soil, or body.
ozone layer A layer of gaseous ozone (O3) in the stratosphere that protects life on earth by filtering out most harmful ultraviolet radiation from the sun. parasite Consumer organism that lives on or in and feeds on a living plant or animal, known as the host, over an extended period of time. The parasite draws nourishment from and gradually weakens its host; it may or may not kill the host. See parasitism. parasitism Interaction between species in which one organism, called the parasite, preys on another organism, called the host, by living on or in the host. See host, parasite. parts per billion (ppb) Number of parts of a chemical found in 1 billion parts of a particular gas, liquid, or solid. parts per million (ppm) Number of parts of a chemical found in 1 million parts of a particular gas, liquid, or solid. parts per trillion (ppt) Number of parts of a chemical found in 1 trillion parts of a particular gas, liquid, or solid. passive solar heating system Captures sunlight directly within a structure without the use of mechanical devices and converts it into low-temperature heat for space heating or for heating water for domestic use. Compare active solar heating system. pathogen Organism that produces disease. Examples are harmful bacteria, viruses, and protozoa. peak production When, after years of pumping, usually a decade or so, the pressure in an oil well drops and its rate of conventional crude oil production starts to decline. peer review Process in which scientists report details of the methods and models they
G10
persistent pollutant See slowly degradable pollutant. pest Unwanted organism that directly or indirectly interferes with human activities. pesticide Any chemical designed to kill or inhibit the growth of an organism that people consider undesirable. petrochemicals Chemicals obtained by refining (distilling) crude oil. They are used as raw materials in manufacturing most industrial chemicals, fertilizers, pesticides, plastics, synthetic fibers, paints, medicines, and many other products. petroleum See crude oil. pH Numeric value that indicates the relative acidity or alkalinity of a substance on a scale of 0 to 14, with the neutral point at 7. Acid solutions have pH values lower than 7, and basic or alkaline solutions have pH values greater than 7. phosphorus cycle Cyclic movement of phosphorus in different chemical forms from the environment to organisms and then back to the environment. photochemical smog Complex mixture of air pollutants produced in the lower atmosphere by the reaction of hydrocarbons and nitrogen oxides under the influence of sunlight. Especially harmful components include ozone, peroxyacyl nitrates (PANs), and various aldehydes. Compare industrial smog. photosynthesis Complex process that takes place in cells of green plants. Radiant energy from the sun is used to combine carbon dioxide (CO2) and water (H2O) to produce oxygen (O2) and carbohydrates (such as glucose, C6H12O6) and other nutrient molecules. Compare aerobic respiration, chemosynthesis. photovoltaic (PV) cell See solar cell.
physical change Process that alters one or more physical properties of an element or a compound without altering its chemical composition or the arrangement of its atoms or ions within molecules. Examples are changing the size and shape of a sample of matter (crushing ice and cutting aluminum foil) and changing a sample of matter from one physical state to another (boiling and freezing water). Compare chemical change, nuclear change. phytoplankton Small drifting plants, mostly algae and bacteria, found in aquatic ecosystems. Compare plankton, zooplankton. planetary management worldview Beliefs that (1) we are the planet’s most important species; (2) there is always more, and it is all for us; (3) all economic growth is good, more economic growth is better, and the potential for economic growth is limitless; and (4) our success depends on how well we can understand, control, and manage the earth’s life-support systems for our own benefit. See spaceship-earth worldview. Compare environmental wisdom worldview. plankton Small plant organisms (phytoplankton) and animal organisms (zooplankton) that float in aquatic ecosystems. plantation agriculture A form of industrialized agriculture for growing specialized crops such as bananas, coffee, and cacao in tropical developing countries, primarily for sale to developed countries. point source Single identifiable source that discharges pollutants into the environment. Examples are the smokestack of a power plant or an industrial plant, drainpipe of a meatpacking plant, chimney of a house, or exhaust pipe of an automobile. Compare nonpoint source. politics Process through which individuals and groups try to influence or control government policies and actions that affect the local, state, national, and international communities. pollutant Particular chemical or form of energy that can adversely affect the health, survival, or activities of humans or other living organisms. See pollution. pollution Undesirable change in, or presence of a chemical or other agent in, the physical, chemical, or biological characteristics of air, water, soil, or food that can adversely affect the health, survival, or activities of humans or other living organisms. pollution cleanup Device or process that removes or reduces the level of a pollutant after it has been produced or has entered the environment. Examples are automobile emission control devices and sewage treatment plants. Compare pollution prevention. pollution prevention Device, process, or strategy used to prevent a potential pollutant from forming or entering the environment or sharply reduces the amount entering the environment. Compare pollution cleanup.
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
polyculture Complex form of intercropping in which a large number of different plants that mature at different times are planted together. See also intercropping. Compare monoculture.
primary ecological succession Sequential development of communities in a bare area that has never been occupied by a community of organisms. Compare secondary ecological succession.
netic radiation). See alpha particle, beta particle, gamma rays.
population Group of individual organisms of the same species living in a particular area.
primary pollutant Chemical that has been added directly to the air by natural events or human activities and occurs in a harmful concentration. Compare secondary pollutant.
radioactive isotope See radioisotope.
population crash A population dieback occurring when a population uses up the given resource supplies of its environment and exceeds the environment’s carrying capacity. population change Increase or decrease in the size of a population. It is equal to (Births + Immigration) – (Deaths + Emigration). population density Number of organisms in a particular population found in a specified area or volume. population size Number of individuals making up a population’s gene pool. potential energy Energy stored in an object because of its position or the position of its parts. Compare kinetic energy. poverty Inability to meet basic needs for food, clothing, and shelter. ppb See parts per billion. ppm See parts per million. ppt See parts per trillion. precautionary principle When there is scientific uncertainty about potentially serious harm from chemicals or technologies, decision makers should act to prevent harm to humans and the environment. See pollution prevention. precipitation Water in the form of rain, sleet, hail, and snow that falls from the atmosphere onto the land and bodies of water. predation Situation in which an organism of one species (the predator) captures and feeds on parts or all of an organism of another species (the prey). predator Organism that captures and feeds on parts or all of an organism of another species (the prey). predator–prey relationship Interaction between two organisms of different species in which one organism, called the predator, captures and feeds on parts or all of another organism, called the prey. preservationist Person concerned primarily with setting aside or protecting undisturbed natural areas from harmful human activities. Compare conservation biologist, conservationist, ecologist, environmentalist, environmental scientist. prey Organism that is captured and serves as a source of food for an organism of another species (the predator). primary consumer Organism that feeds on all or part of plants (herbivore) or on other producers. Compare detritivore, omnivore, secondary consumer.
primary productivity See gross primary productivity, net primary productivity. primary recycling Method of recycling in which materials are recycled into new products of the same type, such as turning used aluminum cans into new aluminum cans. Also called closed-loop recycling. Compare secondary recycling. primary sewage treatment Mechanical sewage treatment in which large solids are filtered out by screens and suspended solids settle out as sludge in a sedimentation tank. Compare secondary sewage treatment. principles of sustainability Three principles by which life on the earth has sustained itself over its 3.5-billion-year history: (1) Reliance on solar energy: the sun warms the planet and supports photosynthesis used by plants to provide food for themselves and for us and most other animals. (2) Nutrient Cycling: natural processes recycle chemicals that plants and animals need to stay alive and reproduce; there is little or no waste in natural systems. Reliance on these four principles could guide us to a more sustainable society. (3) Biodiversity: the variety of different organisms, the genetic information they contain, the ecosystems in which they exist, and the natural services they provide have yielded ways for life to adapt to changing environmental conditions throughout the earth’s history. probability Mathematical statement about how likely it is that something will happen. producer Organism that uses solar energy (green plant) or chemical energy (some bacteria) to manufacture the organic compounds it needs as nutrients from simple inorganic compounds obtained from its environment. Compare consumer, decomposer. proton (p) Positively charged particle in the nuclei of all atoms. Each proton has a relative mass of 1 and a single positive charge. Compare electron, neutron. proven oil reserves Identified deposits from which conventional oil can be extracted profitably at current prices with current technology. PV cell See solar cell. pyramid of energy flow Diagram representing the flow of energy through each trophic level in a food chain or food web. With each energy transfer, only a small part (typically 10%) of the usable energy entering one trophic level is transferred to the organisms at the next trophic level. radiation Fast-moving particles (particulate radiation) or waves of energy (electromag-
radioactive decay Change of a radioisotope to a different isotope by the emission of radioactivity. radioactive waste Waste products of nuclear power plants, research, medicine, weapon production, or other processes involving nuclear reactions. See radioactivity. radioactivity Nuclear change in which unstable nuclei of atoms spontaneously shoot out “chunks” of mass, energy, or both at a fixed rate. The three principal types of radioactivity are gamma rays and fast-moving alpha particles and beta particles. radioisotope Isotope of an atom that spontaneously emits one or more types of radioactivity (alpha particles, beta particles, or gamma rays). rangeland Land that supplies forage or vegetation (grasses, grass-like plants, and shrubs) for grazing and browsing animals and is not intensively managed. Compare feedlot. range of tolerance Range of chemical and physical conditions that must be maintained for populations of a particular species to stay alive and grow, develop, and function normally. See law of tolerance. recharge area Any area of land allowing water to pass through it and into an aquifer. See aquifer. reconciliation ecology Science of inventing, establishing, and maintaining new habitats to conserve species diversity in places where people live, work, or play. recycling Collecting and reprocessing a resource so it can be made into new products. An example is collecting aluminum cans, melting them down, and using the aluminum to make new cans or other aluminum products. Compare reuse. reforestation Renewal of trees and other types of vegetation on land where trees have been removed; can be done naturally by seeds from nearby trees or artificially by planting seeds or seedlings. reliable surface runoff Surface runoff of water that generally can be counted on as a stable source of freshwater from year to year. See runoff. reliable science Data, hypotheses, theories, and laws that are widely accepted by scientists who are considered experts in the field under study. The results of reliable science are based on the self-correcting process of testing, open peer review, reproducibility, and debate. Compare tentative science, unreliable science. renewable resource A resource that can be replenished fairly rapidly (hours to several decades) through natural processes. Examples are trees in forests, grasses in grasslands, wild animals, fresh surface water in lakes and streams, most groundwater, fresh air, and fertile soil. If such a resource is used faster
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than it is replenished, it can be depleted and converted into a nonrenewable resource. See environmental degradation. Compare nonrenewable resource, perpetual resource. replacement-level fertility rate Number of children a couple in a population must have to replace themselves. The average for a country or the world usually is slightly higher than 2 children per couple (2.1 in the United States and 2.5 in some developing countries) because some children die before reaching their reproductive years. See also total fertility rate. reproductive isolation Mutation and change by natural selection operating independently in the gene pools of populations of a particular sexually reproducing species experiencing long-term geographic separation. reserves Resources that have been identified and from which a usable mineral can be extracted profitably at present prices with current mining technology. resource Anything obtained from the living and nonliving environment to meet human needs and wants. It can also be applied to other species. resource partitioning Process of dividing up resources in an ecosystem so species with similar needs (overlapping ecological niches) use the same scarce resources at different times, in different ways, or in different places. See ecological niche. respiration See aerobic respiration. response Amount of health damage caused by exposure to a certain dose of a harmful substance or form of radiation. See dose, dose-response curve, median lethal dose. resource Anything obtained from the environment to meet human needs and wants. resource partitioning Occurs when species competing for similar scarce resources evolve specialized traits that allow them to use shared resources at different times, in different ways, or in different places.
hazards associated with the use of a particular product or technology. See risk, risk-benefit analysis. risk-benefit analysis Estimate of the shortand long-term risks and benefits of using a particular product or technology. See risk assessment. risk communication Communicating information about risks to decision makers and the public. See risk, risk analysis, riskbenefit analysis. risk management Using risk assessment and other information to determine options and make decisions about reducing or eliminating risks. See risk, risk analysis, risk-benefit analysis, risk communication. rock Any material that makes up a large, natural, continuous part of earth’s crust. See mineral. rock cycle Largest and slowest of the earth’s cycles, consisting of geologic, physical, and chemical processes that form and modify rocks and soil in the earth’s crust over millions of years. runoff Freshwater from precipitation and melting ice that flows on the earth’s surface into nearby streams, lakes, wetlands, and reservoirs. See reliable runoff, surface runoff, surface water. Compare groundwater. salinity Amount of various salts dissolved in a given volume of water. salinization Accumulation of salts in soil that can eventually make the soil unable to support plant growth. saltwater intrusion Movement of saltwater into freshwater aquifers in coastal and inland areas as groundwater is withdrawn faster than it is recharged by precipitation. sanitary landfill Waste disposal site on land in which waste is spread in thin layers, compacted, and covered with a fresh layer of clay or plastic foam each day.
reuse Using a product over and over again in the same form. An example is collecting, washing, and refilling glass beverage bottles. Compare recycling.
science Attempts to discover order in nature and use that knowledge to make predictions about what should happen in nature. See frontier science, scientific data, scientific hypothesis, scientific law, scientific methods, scientific model, scientific theory, sound science.
risk Probability that something undesirable will result from deliberate or accidental exposure to a hazard. See risk analysis, risk assessment, risk-benefit analysis, risk management.
scientific data Facts obtained by making observations and measurements. Compare scientific hypothesis, scientific law, scientific methods, scientific model, scientific theory.
risk analysis Identifying hazards, evaluating the nature and severity of risks (risk assessment), and using this and other information to determine options and make decisions about reducing or eliminating risks (risk management), and communicating information about risks to decision makers and the public (risk communication).
scientific hypothesis Educated guess that attempts to explain a scientific law or certain scientific observations. Compare scientific data, scientific law, scientific methods, scientific model, scientific theory.
risk assessment Process of gathering data and making assumptions to estimate shortand long-term harmful effects on human health or the environment from exposure to
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scientific law Description of what scientists find happening repeatedly in nature in the same way, without known exception. See first law of thermodynamics, law of conservation of matter, second law of thermodynamics. Compare scientific data, scientific hypothesis, scientific methods, scientific model, scientific theory.
scientific methods Ways that scientists gather data and formulate and test scientific hypotheses, models, theories, and laws. See scientific data, scientific hypothesis, scientific law, scientific model, scientific theory. scientific model Simulation of complex processes and systems. Many are mathematical models that are run and tested using computers. scientific theory Well-tested and widely accepted scientific hypothesis. Compare scientific data, scientific hypothesis, scientific law, scientific methods, scientific model. secondary consumer Organism that feeds only on primary consumers. Compare detritivore, omnivore, primary consumer. secondary ecological succession Sequential development of communities in an area in which natural vegetation has been removed or destroyed but the soil is not destroyed. Compare primary succession. secondary pollutant Harmful chemical formed in the atmosphere when a primary air pollutant reacts with normal air components or other air pollutants. Compare primary pollutant. secondary recycling Method of recycling in which waste materials are converted into different products. Compare primary recycling. secondary sewage treatment Second step in most waste treatment systems in which aerobic bacteria break down up to 90% of degradable, oxygen-demanding organic wastes in wastewater. Bringing sewage and bacteria together in trickling filters or in the activated sludge process usually does this. Compare primary sewage treatment. second-growth forest Stands of trees resulting from secondary ecological succession. Compare old-growth forest, tree plantation. second law of thermodynamics Whenever energy is converted from one form to another in a physical or chemical change, we end up with lower-quality or less usable energy than we started with. In any conversion of heat energy to useful work, some of the initial energy input is always degraded to a lower-quality, more dispersed, less useful energy, usually low-temperature heat that flows into the environment; you cannot break even in terms of energy quality. See first law of thermodynamics. sedimentary rock Rock that forms from the accumulated products of erosion and in some cases from the compacted shells, skeletons, and other remains of dead organisms. Compare igneous rock, metamorphic rock. See rock cycle. selective cutting Cutting of intermediateaged, mature, or diseased trees in an unevenaged forest stand, either singly or in small groups. This encourages the growth of younger trees and maintains an uneven-aged stand. Compare clear-cutting. septic tank Underground tank for treating wastewater from a home in rural and sub-
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
urban areas. Bacteria in the tank decompose organic wastes and the sludge settles to the bottom of the tank. The effluent flows out of the tank into the ground through a field of drainpipes. shale oil Oil extracted from crushed and heated shale. shelterbelt See windbreak. slash-and-burn agriculture Cutting down trees and other vegetation in a patch of forest, leaving the cut vegetation on the ground to dry, and then burning it. The ashes that are left add nutrients to the low-fertility soils found in most tropical forest areas. Crops are planted between tree stumps. Plots must be abandoned after a few years (typically 2–5 years) because of loss of soil fertility or invasion of vegetation from the surrounding forest.
solar cell Device in which radiant (solar) energy is converted directly into electrical energy.
for domesticated plants and animals and the rest of nature. Compare environmental wisdom worldview, planetary management worldview.
solar collector Device for collecting radiant energy from the sun and converting it into heat. See active solar heating system, passive solar heating system.
stratosphere Second layer of the atmosphere, extending about 17–50 kilometers (11–30 miles) above the earth’s surface. It contains small amounts of gaseous ozone (O3), which filters out about 99% of the incoming harmful ultraviolet (UV) radiation emitted by the sun. Compare troposphere.
solar energy Direct radiant energy from the sun and a number of indirect forms of energy produced by the direct input. Principal indirect forms of solar energy include wind, falling and flowing water (hydropower), and biomass (solar energy converted into chemical energy stored in the chemical bonds of organic compounds in trees and other plants). solid waste Any unwanted or discarded material that is not a liquid or a gas. See municipal solid waste.
slowly degradable pollutant Material that is slowly broken down into simpler chemicals or reduced to acceptable levels by natural physical, chemical, and biological processes. Compare biodegradable pollutant, degradable pollutant, nondegradable pollutant.
sound science Scientific concepts, data, models, theories, and laws that are widely accepted by scientists considered experts in the area of study. These results of science are very reliable. Compare frontier science, junk science.
sludge Gooey mixture of toxic chemicals, infectious agents, and settled solids removed from wastewater at a sewage treatment plant.
spaceship-earth worldview View of the earth as a spaceship: a machine we can understand, control, and change at will by using advanced technology. See planetary management worldview. Compare environmental wisdom worldview.
smart growth Form of urban planning that recognizes that urban growth will occur but uses zoning laws and an array of other tools to prevent sprawl, direct growth to certain areas, protect ecologically sensitive and important lands and waterways, and develop urban areas that are more environmentally sustainable and more enjoyable places to live. smog Originally a combination of smoke and fog, but now used to describe other mixtures of pollutants in the atmosphere. See industrial smog, photochemical smog. soil Complex mixture of inorganic minerals (clay, silt, pebbles, and sand), decaying organic matter, water, air, and living organisms. soil conservation Methods used to reduce soil erosion, prevent depletion of soil nutrients, and restore nutrients already lost by erosion, leaching, and excessive crop harvesting. soil erosion Movement of soil components, especially topsoil, from one place to another, usually by wind, flowing water, or both. This natural process can be greatly accelerated by human activities that remove vegetation from soil. soil horizons Horizontal zones that make up a particular mature soil. Each horizon has a distinct texture and composition that varies with different types of soils. See soil profile. soil profile Cross-sectional view of the horizons in a soil. See soil horizon. solar capital Solar energy from the sun reaching the earth. Compare natural resources.
specialist species A species with a narrow ecological niche. They may be able to live in only one type of habitat, tolerate only a narrow range of climatic and other environmental conditions, or use only one type or a few types of food. Compare generalist species. speciation Formation of two species from one species as a result of divergent natural selection in response to changes in environmental conditions; usually takes thousands of years. Compare extinction. species Group of organisms that resemble one another in appearance, behavior, chemical makeup and processes, and genetic structure. Organisms that reproduce sexually are classified as members of the same species only if they can actually or potentially interbreed with one another and produce fertile offspring. species diversity Number of different species and their relative abundances in a given area. See biodiversity. Compare ecological diversity, genetic diversity. S-shaped curve Leveling off of an exponential, J-shaped curve when a rapidly growing population exceeds the carrying capacity of its environment and ceases to grow. statistics A field of study involving the use of mathematical tools to collect, organize, and interpret numerical data. stewardship worldview View that because of our superior intellect and power or because of our religious beliefs, we have an ethical responsibility to manage and care
stream Flowing body of surface water. Examples are creeks and rivers. strip-cropping Planting regular crops and close-growing plants, such as hay or nitrogenfixing legumes, in alternating rows or bands to help reduce depletion of soil nutrients. strip-mining Form of surface mining in which bulldozers, power shovels, or stripping wheels remove large chunks of the earth’s surface in strips. See surface mining. Compare subsurface mining. subsidence Slow or rapid sinking of part of the earth’s crust that is not slope related. subsurface mining Extraction of a metal ore or fuel resource such as coal from a deep underground deposit. Compare surface mining. surface mining Removing soil, subsoil, and other strata and then extracting a mineral deposit found fairly close to the earth’s surface. Compare subsurface mining. surface runoff Water flowing off the land into bodies of surface water. See reliable runoff. surface water Precipitation that does not infiltrate the ground or return to the atmosphere by evaporation or transpiration. See runoff. Compare groundwater. sustainability Ability of earth’s various systems, including human cultural systems and economies, to survive and adapt to changing environmental conditions indefinitely. sustainability revolution Major cultural transformation that would involve learning how to reduce our ecological footprints and to live more sustainability. sustainable agriculture Method of growing crops and raising livestock based on organic fertilizers, soil conservation, water conservation, biological pest control, and minimal use of nonrenewable fossil fuel energy. sustainable development See environmentally sustainable economic development. sustainable society Society that manages its economy and population size without doing irreparable environmental harm by overloading the planet’s ability to absorb environmental insults, replenish its resources, and sustain human and other forms of life over a specified period, usually hundreds to thousands of years. During this period, it satisfies the needs of its people without depleting natural resources and thereby jeopardizing the prospects of current and future generations of humans and other species.
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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sustainable yield Highest rate at which we can use a potentially renewable resource without reducing its available supply throughout the world or in a particular area. See environmental degradation. synfuels Synthetic gaseous and liquid fuels produced from solid coal or sources other than natural gas or crude oil. syngas Abbreviated name for synthetic natural gas. synthetic natural gas (SNG) Gaseous fuel containing mostly methane produced from solid coal. tar sand Mixture of clay, sand, water, and a combustible, organic material that is a thick and sticky heavy oil with a high sulfur content. temperature Measure of the average speed of motion of the atoms, ions, or molecules in a substance or combination of substances at a given moment. Compare heat. temperature inversion Layer of dense, cool air trapped under a layer of less dense, warm air. This prevents upward-flowing air currents from developing. In a prolonged inversion, air pollution in the trapped layer may build up to harmful levels. tentative science Preliminary scientific data, hypotheses, and models that have not been widely tested and accepted. Compare reliable science, unreliable science. teratogens Chemical, radiation, or virus that causes birth defects. See carcinogen, mutagen. terracing Planting crops on a long steep slope that has been converted into a series of broad, nearly level terraces with short vertical drops from one to another that run along the contour of the land to retain water and reduce soil erosion. tertiary (high-level) consumers Animals that feed on the flesh of other carnivores. They feed at high trophic levels in food chains and webs. Examples are hawks, lions, bass, and sharks. Compare detritivore, primary consumer, secondary consumer. theory of evolution Widely accepted scientific idea that all life forms developed from earlier life forms. Although this theory conflicts with the creation stories of many religions, it is the way biologists explain how life has changed over the past 3.6–3.8 billion years and why it is so diverse today. thermal inversion See temperature inversion. third-level consumers See tertiary consumers. threatened species Wild species that is still abundant in its natural range but likely to become endangered because of a decline in numbers. Compare endangered species. throughput Rate of flow of matter, energy, or information through a system. throwaway society See high-throughput economy.
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tolerance limits Minimum and maximum limits for physical conditions (such as temperature) and concentrations of chemical substances beyond which no members of a particular species can survive. See law of tolerance. total fertility rate (TFR) Estimate of the average number of children who will be born alive to a woman during her lifetime if she passes through all her childbearing years (ages 15–44) conforming to age-specific fertility rates of a given year. In simpler terms, it is an estimate of the average number of children a woman will have during her childbearing years. toxic chemical A chemical that is fatal to humans in low doses or fatal to more than 50% of test animals at stated concentrations. Most are neurotoxins, which attack nerve cells. See carcinogen, hazardous chemical, mutagen, teratogen. toxicity Measure of how harmful a substance is. toxicology Study of the adverse effects of chemicals on the health of humans and other organisms. toxic waste Form of hazardous waste that causes death or serious injury (such as burns, respiratory diseases, cancers, or genetic mutations). See hazardous waste. toxin See poison. traditional intensive agriculture Production of enough food for a farm family’s survival and perhaps a surplus that can be sold. This type of agriculture uses higher inputs of labor, fertilizer, and water than traditional subsistence agriculture. See traditional subsistence agriculture. Compare industrialized agriculture. traditional subsistence agriculture Production of enough crops or livestock for a farm family’s survival and, in good years, a surplus to sell or put aside for hard times. Compare industrialized agriculture, traditional intensive agriculture. tragedy of the commons Depletion or degradation of a potentially renewable resource to which people have free and unmanaged access. An example is the depletion of commercially desirable fish species in the open ocean beyond areas controlled by coastal countries. See common-property resource. traits Characteristics passed on from parents to offspring during reproduction in an animal or plant by means of coded units of genetic information. transgenic organisms See genetically modified organisms. transmissible disease Infectious disease caused by living organisms (such as bacteria, viruses, and parasitic worms) that can spread from one person to another by air, water, food, or body fluids (or in some cases by insects or other organisms). Compare nontransmissible disease.
transpiration Process by which water evaporates from the surfaces of plants. tree farm See tree plantation. tree plantation Site planted with one or only a few tree species in an even-aged stand. When the stand matures it is usually harvested by clear-cutting and then replanted. These farms normally are used to grow rapidly maturing tree species for fuelwood, timber, or pulpwood. See even-aged management. Compare old-growth forest, second-growth forest, uneven-aged management. trophic level All organisms that are the same number of energy transfers away from the original source of energy (for example, sunlight) that enters an ecosystem. For example, all producers belong to the first trophic level, and all herbivores belong to the second trophic level in a food chain or a food web. troposphere Innermost layer of the atmosphere. It contains about 75% of the mass of earth’s air and extends about 17 kilometers (11 miles) above sea level. Compare stratosphere. true cost See full cost. undernutrition Consuming insufficient food to meet one’s minimum daily energy needs for a long enough time to cause harmful effects. Compare malnutrition, overnutrition. unreliable science Scientific hypotheses and results that are presented as reliable science without having undergone the rigors of peer review, or that have been discarded as a result of peer review. Compare reliable science, tentative science. urban growth Rate of increase of urban populations. urbanization Creation and growth of urban areas, or cities and their surrounding developed land. urban sprawl Growth of low-density development on the edges of cities and towns. See smart growth. virtual water Water that is not directly consumed but is used to produce food and other products, and represents a large part of our water footprints, especially in moredeveloped nations. volcano Vent or fissure in the earth’s surface through which magma, liquid lava, and gases are released into the environment. vulnerable species See endangered species. waste management Dealing with solid wastes in ways that attempt to reduce their environmental harm without seriously trying to reduce the amount of waste produced. Compare waste reduction. waste reduction Ways to deal with solid waste in which much less waste and pollution are produced, and what is produced is viewed as potential resources that can be reused, recycled, or composted. Compare waste management. water cycle See hydrologic cycle.
GLOSSARY Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
water footprint A rough measure of the volume of water that we use directly and indirectly to keep us alive and to support our lifestyles. waterlogging Saturation of soil with irrigation water or excessive precipitation so the water table rises close to the surface and deprives plants of the oxygen they need to survive. water pollution Any physical or chemical change in surface water or groundwater that can harm living organisms or make water unfit for certain uses.
weather Short-term changes in the temperature, barometric pressure, humidity, precipitation, sunshine, cloud cover, wind direction and speed, and other conditions in the troposphere at a given place and time. Compare climate. weathering Physical and chemical processes in which solid rock exposed at earth’s surface is changed to separate solid particles and dissolved material, which can then be moved to another place as sediment. See erosion.
watershed Land area that delivers water, sediment, and dissolved substances via small streams to a major stream (river).
wetland Land covered all or part of the time with saltwater or freshwater, excluding streams, lakes, and the open ocean. See coastal wetland, inland wetland.
water table Upper surface of the zone of saturation, in which all available pores in the soil and rock of the earth’s crust are filled with water.
wilderness Area where the earth and its community of life-forms have not been seriously disturbed by humans and where humans are only temporary visitors.
windbreak Row of trees or hedges planted to partially block wind flow and reduce soil erosion on cultivated land. wind farm Cluster of small to medium-sized wind turbines in a windy area to capture wind energy and convert it into electrical energy. worldview Set of beliefs about how the world works and about what one’s role in the world should be. See environmental wisdom worldview, planetary management worldview, spaceship-earth worldview. zone of saturation Area where all available pores in the soil and rock of the earth’s crust are filled by water. See water table. zoning Regulating how various parcels of land can be used. zooplankton Animal plankton. Small floating herbivores that feed on plant plankton (phytoplankton). Compare phytoplankton.
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Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Index Note: Page numbers in boldface indicate terms in boldface in the text. Page numbers followed by italicized f or t indicate figures or tables, and b indicates boxed material. Abiotic components in ecosystems, 34 Abortion, birth rate and availability of, 82 Abyssal zone of ocean, 61f Accidentally-introduced species, 99–102 Acid deposition (acid rain), 43, 249–51 formation of, 249f global regions affected by, 250f harmful effects of, 250–51 solutions for preventing and cleaning up, 251f Acidity, 26, 27f Acid rain. See Acid deposition Active solar heating system, 211, 212f Acute effect of toxic chemicals, 234 Adaptation, 52 limits on evolution through, 52–53 Adaptive trait, 52 Advanced tissue culture, 137 Aerobic respiration, 36, 43 Affluence, 16 in China, 13 in U.S., 16 Affluenza, 16 simple living as response to, 324–25, 326f Africa biodiversity hotspots in east, 123b Green Belt movement and reforestation in, 117b Age structure of population, 83, 84f deaths caused by AIDS and, 230f U.S. baby-boom generation, 84–85 Agribusiness, 135 Agricultural revolution, 14f Agriculture. See also Crop(s); Food production aquaculture, 137–38, 142–43, 151f effects of climate change on, 264 effects of ozone depletion on, 271f green revolutions in, 135 human population growth and, 79 industrialized (high-input), 133–34, 135–37, 152f irrigation and (see Irrigation) meat production, 137, 150 monoculture, 133–34 organic, 151–52 pest management in, 143–48 polyculture, 134 slash-and-burn, 134–35 soils and (see Soil; Soil erosion) solutions for sustainable, 151f traditional, 134–35 water pollution caused by, 171 Agrobiodiversity, 141 Agroforestry, 148, 149f
AIDS (acquired immune deficiency syndrome), 230 death rate, 230f HIV and, 229, 230 population declines attributed to, 85 Air circulation, climate and global, 245f Air plants, 74 Air pollutants formaldehyde as, 251–52 indoor, 247, 251–53 lead as, 246t, 254, 255f major types and sources of, 246t primary, and secondary, 247 radon gas as, 246t, 252–53 soot and black carbon aerosols as, 262 Air pollution, 246–57 acid deposition and, 249–51 atmospheric ozone depletion and increased, 271f climate change and effects of, 262 coal burning as source of, 248 food production as cause of, 139f harmful effects of, on human health, 247, 253 indoor, 247, 251–53 in Mexico City, 280 outdoor, 246–48 radioactive radon gas as, 252–53 solutions for reducing and preventing, 254–57 Alien (nonnative) species, in Great Lakes, 128, 175. See also Nonnative species Alley cropping, 148, 149f Altitude, climate, biomes, and effects of, 244, 245f Amino acids, 27 Ammonification, 43 Amphibians, 55 case study on disappearing, 69, 70f, 71 Anderson, Ray, development of sustainable corporation by, 308b Anemia, 132 Animal(s) as food source, 137, 142f, 150f toxic chemical laboratory studies on, 234–36 zoos and aquariums for protection of endangered, 107 Animal feedlots, 137, 142f Animal manure, 149 as fuel, 217 Ant(s), E.O. Wilson on, 51b Antarctica, ozone depletion over, 269–72 Antibiotics, bacterial resistance to, 53f, 229b Antibodies, 234 Aquaculture, 133, 137–38 environmental problems caused by, 142, 143f sustainable, 150, 151f Aquatic life zones, 33, 60–65 biodiversity in, 60 ecological and economic resources in, 60–62
effects of acid deposition on, 250 freshwater, 62–64 human impact on, 62, 64 marine (saltwater), 60–62 net primary productivity in, 40f protecting biodiversity in, 125–29 range of tolerance for temperature in, 35f Aquifers, 41, 156, 157f. See also Groundwater deep, 162 withdrawing groundwater from, 161–62 Aral Sea ecological disaster, 164–65 Arboreta, 107 Arctic Climate Impact Assessment, 263 Arctic National Wildlife Refuge (ANWR), oil reserves in, 191f Arctic region air pollution in, 247f oil supplies in, 191f ozone depletion over, 269–72 permafrost of, 263 Argentine fire ant, 100, 102f Arsenic as water pollutant, 175–76 Artificial ecosystems, 123 Artificial selection, 137 El-Ashry, Mohamed, 224 Asian carp, 128 Asteroids, 54 Atmosphere, 32f, 244–46 air pollution in (see Air pollution) carbon dioxide and methane levels in, over time, 259f, 260f climate, weather, and, 244–46 (see also Climate) layers of, 244f greenhouse gases and natural greenhouse effect in, 34, 246 ocean currents, biomes, and air circulation in, 245f ozone layer of, 244 removal of carbon dioxide from, and storage, 266, 267 stratosphere of, 244 (see also Stratosphere) temperature of, 259f, 260f (see also Atmospheric warming; Climate change) troposphere of, 244 (see also Troposphere) Atmospheric warming. See also Climate change effects of, on biodiversity, 55 J. Hansen on climate change and, 261b human activities as factor in, 259–61 projected disruption caused by, 262–65 Atom(s), 25–26, 31f Atomic number, 25 Atomic theory, 25 Auditory learners, 4 Autotrophs (producers), 35–36 Baby boom generation, U.S., 80, 81f, 84–85 Background extinction of species, 93 Background extinction rate, 55
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
I1
Bacon, Francis, 90 Bacteria nitrogen-fixing, 43 resistance to antibiotics in pathogenic, 53f, 229b Balance of nature, 75 Bangladesh flooding in, 170 microlending by Grameen Bank in, 309 Basal cell skin cancer, 272b Bathyal zone, ocean, 61f Beavers, 71 Bicycles as transportation, trade-offs of, 282f Billion Tree Campaign, 117 Bioaccumulation of DDT, 103f Biochar, 266 Biodegradable pollutants, 11 Biodiesel, 208–9, 217 Biodiversity, 6, 49–66 in aquatic life zones, 60–65, 125–29 biomes and, 56–59 definition and types of, 50f ecosystems approach to preserving (see Ecosystem approach to sustaining biodiversity) effects of atmospheric warming/climate change on, 55, 264 effects of human activities on, 59f, 62f, 64 evolution of, 51–54 food production linked to loss of, 139f, 140–41 importance of, 50–51 instrumental value of, 97–98 intrinsic value of, 98 loss of (see Extinction of species) reasons for protecting, 128–29 species, speciation, and, 50, 54–56 (see also Species) species approach to preserving (see Species approach to sustaining biodiversity) sustainability principles and protection of, 6, 7f, 64–65 Biodiversity hot spots, 94, 122 global, 123f in Tanzania, 123b Biofuels, 217–19 Biogeochemical (nutrient) cycles, 40–46 Biological capacity, 12, 13f Biological community, 32. See also Community(ies) Biological diversity, 50. See also Biodiversity Biological evolution, 51–52. See also Evolution Biological extinction of species, 93. See also Extinction of species Biological hazards, 227–32. See also Disease HIV and AIDS epidemic, 230 infectious disease as, 227–28 malaria as, 144–45, 230–32 pathogen resistance to antibiotics and, 53f, 229b reducing incidence of infectious disease, 232 tuberculosis as, 228–29 viruses and parasites as, 229–30 Biological income, 51 Biological pollution, 175. See also Introduced species; Invasive species Biomagnification of DDT, 103f Biomass, 37, 217 energy production from, 188, 217–19 in food chains and food webs, 37–39 Biomass plantations, 217
I2
Biome(s), 33, 56–59 characteristics of, 57–59 climate and, 56–57, 245f earth’s major, 57f global air circulation and, 245f human impact on, 59f precipitation, temperature, and, 58f Bioplastics, 290b Bioremediation of hazardous waste, 294 Biosphere, 31f, 32. See also Biome(s); Ecosystem(s) Biosphere reserve, 120f Biotic components in ecosystems, 34, 35–36 Biotic potential of populations, 76–77 Birds brown pelican, 106 distribution of, in North and South America, 105f effect of pesticides on, 103 extinct, 93 mutualism between rhinoceros and oxpecker, 74f resource partitioning among warblers, 73f threatened, 104–5 Birth control methods, effectiveness of, 82 Birth rate (crude birth rate), 79 fertility rates and, 80–82 reducing, by empowering women, 81–82, 87 reducing, with family planning programs, 87–89 in United States, 80, 81f Bitumen, 192 Black carbon aerosols, 262 Blackfoot Challenge, U.S., 124–25 Boomerang effect, pesticides and, 146 Boreal forests, 58, 111 Botanical gardens, 107 Bottled water, 177 Bowash megalopolis, 278f Brazil biofuel production in, 218 Curitiba, as sustainable city in, 284–85 tropical forests in, 114, 120 Brown, Lester R., 205, 218, 311 Brown-air smog, 248 Brownfields, 297 Buffer zone concept, 120f Buildings indoor air pollution in, 251–53 net energy ratios for heating, 190f saving energy in, 209, 210f solar-heated, 211, 212f Bureau of Land Management (BLM), U.S., 314 Burning. See Incineration Buses as transportation, trade-offs of, 282f Business environmental leadership by, 268 environmentally-sustainable, 306, 308b, 312f reducing water use by, 167–68 CAFE (Corporate Average Fuel Economy) standards, 208 California Water Project, 164f Canada freshwater resources in, 156 oil reserves in, 191 Canals, 64, 192–93 Cancer caused by toxic chemicals, 233–34 UV radiation and skin, 272b
Cap-and-trade programs, 255–56, 307 trade-offs of, 267f Capital, 8. See also Natural capital Captive breeding, 107 Carbohydrates, 26, 27 Carbon, 25 atom, 26f Carbon cycle, 42f–43 effects of human activities on, 43 Carbon dioxide (CO2), 43 as air pollutant, 246t atmospheric levels of, over time, 259f, 260f emissions of, by energy sources, 196f fossil fuels and emissions of, 192, 193, 194, 196f, 29–60 global temperature and levels of, 259f, 260f reducing emissions of, 266, 267f, 268f removing from atmosphere, and storing, 266, 267b storage of, in oceans, 261–62 Carbon monoxide as air pollutant, 246t Carbon neutral, 268 Carbon taxes, 266 Carcinogens, 233 Careers, environmentally-sustainable, 312f Carnivores, 35 Carrying capacity (K), 77 results of exceeding, 77–78 Carson, Rachel, dangers of pesticides revealed by, 144b Case reports on chemical toxicity, 236 Case studies affluent consumers in China, 13 AIDS disease and HIV virus, 230 amphibians as indicator species, 69–71 Aral Sea disaster, 164–65 Blackfoot Challenge as reconciliation ecology, 124–25 bottled water, 177 Chernobyl nuclear power plant accident, 200 Chesapeake Bay water pollution, 179f coal ash, 196 Costa Rica as conservation leader, 120–21 Curitiba, Brazil as ecocity, 284–85 deaths caused by smoking, 238–40 ethanol as fuel, 218–19 flooding in Bangladesh, 170 Great Lakes water pollution, 174–75 high-level radioactive waste in U.S., 201 human population growth in U.S., 80 industrial ecosystems, 298, 299f introduced snake species in Everglades, 102 lead as toxic pollutant, 246t, 254, 255f malaria, 230–32 Mexico City as urban area, 280 microlending programs to reduce poverty, 309 organic agriculture, 151–52 passenger pigeon, 93 polar bears and climate change, 103–4 radioactive radon gas, 252 recycling plastics, 290 reuse of refillable containers, 288–89 sharks, protection of, 71–72 slowing population growth in China and India, 88–89 threatened bird species, 104–5 tuberculosis, 228–29 U.S. baby boom generation, 84–85 U.S. Blackfoot Challenge, 124–25 U.S. environmental laws and regulations, threats to, 316–17
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
U.S. forests, re-growth of, 113–14 U.S. freshwater resources, 157, 158f U.S. Great Lakes and alien species, 128 U.S. hazardous waste regulation, 296–97 U.S. immigration and population size, 82–83 U.S. industrial food production, 135–37 U.S. public lands management, 313–16 U.S. public parks, 118 U.S. reduction of point-source water pollution, 181 U.S. solid wastes, 285–86 U.S. wilderness protection, 121 U.S. urbanization, 277 water resource conflicts in Middle East, 160–61 Catastrophes, natural selection, evolution, and, 53–54 Cell(s), 27, 31f relationship of chromosomes, genes, DNA and, 28f Cells (atmosphere), 245 Cellulosic ethanol, 218 Center-pivot low-pressure sprinkler, 166f, 167 Centers for Disease Control and Prevention (CDCs), 133, 238, 254 Central Arizona Project, 164f Centralized macropower systems, 221, 222f Central receiver system, 212 Chain reaction, nuclear, 197f Channelization of streams, 170 Chemical bonds, 26 Chemical change in matter, 28 Chemical cycling, 8. See also Nutrient cycling sustainability principles and, 6, 7f Chemical energy, 30 Chemical reaction, 28 Chemical formula, 26 Chemical hazards, 327, 233–37. See also Hazardous wastes; Toxic chemicals arsenic as, 175–76 dirty dozen, 297–98 evaluating toxicity of, 234–37 harmful effects of, on human body, 233–34 in homes, 286f indoor air pollutants as, 251, 252f, 253 lead, 246t, 254, 255f mercury, 233b persistent organic pollutants (POPs), 146, 237, 297–98 pesticides (see Pesticides) pollution prevention and precautionary principle applied to, 237 Chemical reactions, 28 Chernobyl nuclear power accident, 200 Chesapeake Bay, pollution in, 179f Children cost of rearing and educating, 80 hunger and malnutrition in, 132 in labor force, 80 lead as health threat to, 254, 255f mercury as health threat to, 233b China acid deposition in, 250 affluent consumers in, 13 basic demographic data for, 88f ecological footprint, 12, 89 energy efficiency program in, 268 human population in, 79, 80f human population regulation in, 88–89 water resources and water pollution in, 156, 159, 173, 175
Chlorinated hydrocarbons, 26 Chlorofluorocarbons (CFCs) cutting emissions of, 271–72 stratospheric ozone depletion and role of, 270 Chromosomes, 27 relationship of cells, genes, DNA and, 28f Chronic effects of toxic chemicals, 234 Chronic malnutrition, 132 Chronic undernutrition, 132 Circle of poison, pesticides and, 146 Cirrus clouds, 262 Cities. See Urban areas Citizens environmental groups, 297, 318–19 Clean Air Acts, U.S., 254, 255 Cleanup approach to acid deposition, 251f to air pollution, 256f to climate disruption, 266f to soil salinization, 150f to water pollution, 177f, 180f Clean Water Acts, U.S., 181 Clear-cutting of forests, 112, 113f Climate, 33–34, 53, 244–46 atmospheric gases, natural greenhouse effect and, 34, 246 biomes and, 56–57f, 58f (see also Biome(s)) change in (see Climate change) global air circulation and, 245f global zones of, 245f ocean currents and, 246 in urban areas, 280 Climate change, 258–69. See also Atmospheric warming atmospheric concentrations of greenhouse gases and, 259–60 evolution, natural selection, and, 53–54 historic changes in earth’s temperature and past, 258f human activities leading to, 259–61 nuclear energy and mitigation of, 201–2 ocean absorption of CO2 and, 261–62 options for slowing projected, 265–69 outdoor air pollution and, 262 potential effect of cloud cover on, 262 preparing for, 269 projected severe consequences of, 55, 159, 103–4, 262–65 scientist J. Hansen sounds alarm on, 261b species extinction linked to, 103, 104 validity of IPCC report, and scientific consensus on, 260b water resources and effects of, 159 Climax community, 75 Cloud cover, climate change and, 262 Coal, 194–97 coal ash a byproduct of, 171, 181, 196 converting, into gaseous and liquid fuel, 197f energy production from burning, 195f environmental impact of burning, 194, 196f, 248, 249, 260 formation of, 195f trade-offs of, 196f Coal ash, 171, 181 as environmental problem, 196 Coal bed methane gas, 193 Coal-burning power plants, 195f air pollution produced by, 248, 249 energy waste in, 207 Coal gasification, 197 Coal liquefaction, 197
Coastal coniferous forests, 58 Coastal wetlands, 61 feeding niches of birds in, 68f Coastal zones, 60, 61f Chesapeake Bay estuary, 179 integrated coastal management of, 126–27 pollution in, 178–79, 180f Cockroaches, 68b Cogeneration, 207 Combined heat and power (CHP) systems, 207 Command and control approach to environmental regulation, 307 Commensalism, 74 Commercial energy, 188 fossil fuels as main source of, 188–97 global sources of, 189f in U.S., 189f, 206f Commercial forests, 111f Common-property resources, 12 Community(ies), 31f, 32. See also Ecosystem(s) ecological succession in, 74, 75f, 76f foundation species in, 71 indicator species in, 69–71 keystone species in, 72 responses of, to changing environmental conditions, 74–76 species interactions in, 72–74 Community-based conservation, 124 Community ecology, 67–76 environmental conditions and, 74–76 species interactions, 72–74 species roles, 68–72 Compact cities, 281 Companies, environmental leadership by global, 268. See also Business Comparative risk analysis, 237 Competitor species, 78 Complex carbohydrates, 27 Compost and composting, 149–50 of biodegradable organic waste, 290 toilet systems, 168, 183 Compounds, 25 molecular, and ionic, 26 organic, and inorganic, 26–27 Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA Superfund program), U.S., 296 Concentrated animal feeding operations (CAFOs), 137 Coniferous forests, 58, 111 Conservation concessions, 116 Conservation land trusts, 319 Conservation of matter, law of, 29, 310 Conservation-tillage farming, 149 Constitutional democracy, 312 Consumer education, 223–24 Consumers (heterotrophs), 35, 36f Consumption in China, 13 excessive, and species extinctions, 103 simple living, and reduced, 324–25, 326f Containers, reuse of refillable, 288–89 Contour farming, 148, 149f Control rods, nuclear reactors, 198 Convention(s), 321. See also International agreements Conventional natural gas, 193, 194f Conventional oil, 189, 192f. See also Oil Convention on Biological Diversity (CBD), 105 Convention on International Trade in Endangered Species (CITES), 105
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
I3
Coolant, nuclear reactors, 198 Copenhagen Protocol, 271, 321 Coral reef(s), 61, 125–26 climate change as threat to, 264 human impact and degradation of, 62f Coral Reef Monitoring Network, 126 Corn, ethanol production from, 218 Corporate Average Fuel Economy (CAFE) standards, 208 Costa Rica, 268 nature reserves in, 120–21f Costs external, and internal, 305 including environmental, in market prices, 306 pricing based on full, 281, 304, 306 Cradle-to-grave responsibility laws, 288 Crash (dieback) of populations, 77–78 Critical thinking skills, developing, 2–3 Crop(s) crossbreeding, and genetic engineering of, 137, 141f effects of acid deposition on, 250 energy production from residues of, 217 grain, 133, 135f, 150f green revolution and increased yields in, 135 industrialized production of, and monoculture of, 133–34 pesticide use on (see Pesticides) polyculture of, 134, 135 sustainable pest protection for, 143–48 Croplands, 133 drought and flooding causing degradation of, 139–40 Crop residues, 217 Crude birth rate, 79. See also Birth rate Crude death rate, 79. See also Death rate Crude oil, 180, 189. See also Oil refining, 190, 191f Crude petroleum, 179. See also Oil Crust, earth’s, 32f, 33 Cultural eutrophication of lakes, 174 Cultural hazards, 227 Culture, ecological footprint and, 14–15 Cumulus clouds, 26 Curitiba, Brazil, as sustainable ecocity, 284–85 Cuyahoga River, Ohio, cleanup of, 172–73 Dams and reservoirs, 64, 161. See also Lakes capturing water resources using, 162, 163f hydropower at, 214–15 reducing flood risks with, 170–71 water pollution in, 173–74 Darwin, Charles, 49, 67 Data, 22 DDT, 144–45 bioaccumulation and biomagnification of, 103f Death rate (crude death rate), 79, 82 AIDS as cause of higher, for ages 15 to 49, 230 air pollution as cause of human, 253f death from select causes, 238f factors affecting, 82 hazards and risks of death, 239f among infants, 81 from select infectious diseases, 228f Debt-for-nature swaps, 116 Decentralized micropower systems, 221, 222f Decommissioned nuclear power plants, 201 Decomposers, 35, 36f Deep aquifers, 162
I4
Deep-well disposal of hazardous wastes, 295 Deforestation, 112–13 flooding caused by, 169f harmful environmental effects of, 113f tropical, 98, 114, 115f Degradable wastes in water, 176 Deliberately-introduced species, 99, 101f Democracy(ies), 312 making environmental policy in U.S., 312–20 Demographic transition, 86, 87f Dengue fever, 265f Denitrification, 43 Denmark detoxification of hazardous wastes in, 294 industrial ecosystem, 298, 299f Department of Energy (DOE), U.S., 191, 206, 207 Desalination of seawater, 165 Desert(s), 57 human impacts on, 59f Desertification, 139–40 Detritivores, 35, 36f Detritus feeders, 35, 36f Deuterium-tritium nuclear fusion reactions, 202f Differential reproduction, 52 Direct costs, 305 Direct prices. See Market prices Dirty dozen (chemical hazards), 297–98 Disasters Aral Sea, 164–65 Chernobyl nuclear, 200 Discharge trading policy, 181 Disease, 227–32 climate change and increased, 264 death rates from infectious, 228f emergent, 230 HIV and AIDS, 229, 230 malaria, 144–45, 230–32 nutritional deficiencies and, 132–33 pathogen resistance to antibiotics and, 229b reducing incidence of, 232 tobacco, smoking, and, 238–40 tuberculosis, 228–29 viral, 229–30 Disperse cities, 281 Dissolved oxygen (DO) content, 34 DNA (deoxyribonucleic acid), 27 mutations in, 233 relationship of cells, chromosomes, genes, and, 28f Document services, 308 Dose, toxic chemical, 235 average lethal, for humans, 235t Dose-response curve, 234f Drainage basin, 63, 64f, 156 Drinking water. See also Freshwater bottled, 177 groundwater and, 175 (see also Groundwater) purification of, 176–77 reducing disease by disinfecting, 232 water pollution and lack of access to clean, 17 Drip irrigation systems, 166f, 167 Drought, 139–40, 158–59 climate change and, 263 Dry deposition, 249 Dry casks, 200 Dubos, René, 5 Earth atmosphere (see Atmosphere) average global temperature of, 258f
biomes of (see Biome(s)) climate and rotation of, 245f (see also Climate) climate change (see Climate change) conditions on, as favorable for life, 54b ecosystems of (see Ecosystem(s)) energy flow between sun and, 33f human overpopulation on, 86 (see also Human population) life-support systems of (see Life-support systems, earth’s) natural capital of (see Natural capital) as ocean planet, 60f poles of, ozone depletion at, 270 structure of, 32f Earthquakes, 53 Ecocities, 283–84 Curitiba, Brazil, as, 284–85 Eco-labeling programs, 304 Ecological deficit, 12 Ecological diversity, 50f Ecological economists, 303, 304f Ecological efficiency, 39 Ecological extinction of species, 93 Ecological footprint, human, 10–15 defined, 12 as model of unsustainability, 12, 13f per capita, 12, 13f of urban areas, 278, 279f Ecological niche, 68 of birds in coastal wetlands, 68f generalist, 68–69 specialist, 68 Ecological restoration, 122–24 Ecological services provided by forests, 111f provided by freshwater systems, 62f provided by marine ecosystems, 60f provided by rivers, 163f Ecological succession, 74–76 lack of predictability in, 75–76 primary, 74, 75f secondary, 75, 76f Ecological tipping point, 14, 265f Ecology, 6, 31 community, 67–76 ecosystems, and, 6 (see also Ecosystem(s)) organisms and, 6 (see also Organism(s)) population, 76–90 reconciliation, 124–25 of species (see Species) Economic development, 10 demographic transition and, 86, 87f Economic growth, 10 Economics, 303–12 disagreements on natural capital and economic growth, 303–4 reducing poverty to improve environmental quality, 308–10 resources supporting systems of, 303 sustainable energy future and, 222–24 transition to environmentally-sustainable economies, 310–12 using economic tools to deal with environmental problems, 305–8 Economic security, 320 Economic services provided by forests, 111f provided by freshwater systems, 62f provided by marine ecosystems, 60f Economic systems, 303 resources supporting, 303
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Economists, schools of, 303–4 Economy(ies). See also Economics high-throughput (high-waste), 303f low-throughput, 311 matter recycling and reuse, 310–11 poverty reduction in, 308–10 role of natural capital and growth in, 303–4 transition to environmentally-sustainable, 310–12 using tools of, to deal with environmental problems, 305–8 Ecosystem(s), 6, 31f, 32, 34–36. See also Community(ies) abiotic and biotic components of, 34, 35f aquatic (see Aquatic life zones) artificial, 123 biodiversity and (see Biodiversity; Ecosystem approach to sustaining biodiversity) biomes and (see Biome(s)) ecological succession in, 74, 75f, 76f energy flow in, 37, 38f, 39f, 40 food chains and food webs in, 37–39 gross and net primary productivity of, 39, 40f limiting factors in, 34 major components of, 34–36, 37f matter cycling in, 40–46 population range of tolerance in, 34, 35f producers and consumers in, 35–36 responses of, to changing environmental conditions, 74–76 restoration of, 122–24 species’ roles in, 68–72 terrestrial (see Terrestrial life zones) Ecosystem approach to sustaining biodiversity, 110–30 in forests, 111–17 four-point strategy, 122 in freshwater aquatic systems, 127–28 in marine aquatic systems, 125–27 in parks and nature reserves, 118–21 priorities for, 128–29 protecting biodiversity hotspots, 122, 123b reconciliation ecology and, 124, 125f rehabilitating and restoring ecosystems, 122–24 species approach versus (see Species approach to sustaining biodiversity) for terrestrial biodiversity, 122–25 Ecotaxes, 306–7 Ecotourism, 97 Eddington, Arthur S., 47 Education of consumers, 223–24 environmental literacy, 323, 324f learning from the earth, 324 Educational institutions environmental roles of, 319–20 greenhouse gas emissions reduced by, 268 Egg pulling, 107 Electricity, generation of from biomass incineration, 217 from coal (see Coal; Coal-burning power plants) energy efficiency in, 207 from flowing water (hydropower), 214–15 from geothermal resources, 219–20 from nuclear plants (see Nuclear energy) renewable energy for, 211 solar thermal and solar cells for, 212–14 from wind, 215–16 Electric motors, energy waste in, 207
Electromagnetic radiation, 29f Electron(s) (e), 25 Electronic waste (e-waste), 286 Electron probability cloud, 26f Elements, 25 Elephants, 71 reduction range of, 100f Emergent diseases, 230 Emissions trading, 255–56 Endangered species, 94–96. See also Extinction of species birds, 104–5 characteristics of, 96f examples of, 95f gene banks, botanical gardens, and wildlife farms to protect, 106–7 gray wolf, 119b laws and treaties to protect, 105–6, 107b polar bears, 103–4 refuges and sanctuaries to protect, 106 sustainability principles to protect, 107–8 zoos and aquariums to protect, 107, 108f Endangered Species Act of 1973, U.S., 106, 124, 126 gray wolf restoration and, 119b reviewing record of, 107b Endemic species, 55, 98 Endocrine system, chemical hazards to human, 234 Energy, 21, 29–31. See also Energy resources efficiency in use of (see Energy efficiency) flow of (see Energy flow) forms, and quality of, 29–30 laws of thermodynamics governing changes in, 30–31, 38f net, 188–89, 190b Energy conservation, 206 Energy efficiency, 206–11, 266 in buildings, 209–10 in industry and utilities, 207 reducing energy waste, 206–7 sustainable energy future and role of, 2 22, 223f in transportation, 208–9 Energy-efficient diesel car, 208 Energy flow between earth and sun, 33f in ecosystems, 37, 38f, 39f, 40 pyramid of, 39f Energy quality, 30 Energy resources, 9 biomass as renewable, 217–19 commercial (see Commercial energy) energy efficiency as, 206–11 fossil fuels as nonrenewable, 188–97 geothermal, as renewable, 219–20 hydrogen as renewable, 220–21 hydropower as renewable, 214–15 net energy, 188–89, 190b nuclear energy as nonrenewable, 197–203 requirements of, by industrialized agriculture, 138 solar, as renewable, 211–14 solid waste incineration to produce, 291–92f transition to using sustainable, 221–24 wind power as renewable, 215–16 Energy taxes, 266 Enoughness, principle of, 324 Environment, 6 community and ecosystems response to conditions in, 74–76
Environmental audits, 320 Environmental citizenship, 325 Environmental costs and market prices, 17. See also Market prices of water, 166, 168 Environmental degradation, 10, 11f. See also Environmental problems; Natural capital degradation Environmental economists, 304 Environmental ethics, 17, 322 environmental worldviews and, 17–18, 322–23 A. Leopold on, 325b Environmental groups grassroots citizen, 297, 318–19 student, 319–20 Environmental hazards. See Hazard(s) Environmentalism, 6. See also Environmental groups Environmental justice, 297 environmental policy and principle of, 313 Environmental law. See also Environmental policy on air pollution, 254–55 attacks on U.S., 316–17 cradle-to-grave responsibility, 288 hazardous wastes, 295, 296–97 improving environmental quality with innovation-friendly, 307 major U.S., 315f passage of, in democracies, 312–13, 314f on pesticides, 146 to protect endangered species, 105–6, 107b to protect marine biodiversity, 126 on public lands in U.S., 313–16 on water pollution and water quality, 172–73, 176, 181 Environmental leadership, reducing threat of climate change and role of, 268 Environmental literacy, 323, 324f Environmentally-sustainable economies making transition to, 310–12 methods of improving environmental quality in, 305–8 reducing poverty in, 308–10 Environmentally-sustainable society, 18–19, 323–28 components of, 324f environmental citizenship and, 325 environmental literacy in, 323, 324f individuals matter in, 18–19 (see also Individuals matter) low-waste in, 297–99 simple living and, 324–25, 326f sustainability principles and, 327–28 vision of, 326–27 Environmental policy, 312–20 attacks on environmental law, regulations, and, in U.S., 316–17 citizen groups, and making of, 318–19 controversies surrounding, 313, 314f defined, 313 democratic political systems, politics, and making, 312–13 on energy, 221 global environmental security and international, 320–21 individual’s influence on, 317, 318b, 319b principles for making, 313 on public lands management in U.S., 313–16
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
I5
Environmental policy (cont’d) reducing threat of climate change through, 266–68 student and educational groups, and making of, 319–20 Environmental problems, 5–20 affluence and, 16 biodiversity loss (see Extinction of species) causes of, 15–18 economic tools used to deal with, 305–8 environmentally-sustainable society and, 18–19 environmental worldviews and, 17–18, 322–23 food production as cause of, 138–43 human ecological footprint and, 10–15 human population growth as cause of, 15–16 (see also Human population growth) pollution as (see Air pollution; Pollution; Water pollution) poverty and, 16–17, 308–10 (see also Poverty) prices, value of natural capital and, 17 sustainability principles and, 6–10 trade-offs of global efforts to solve, 321f waste as (see Waste) Environmental Protection Agency (EPA), U.S., 144, 146, 174, 175, 181, 196, 210, 251, 253, 281, 295, 296 Environmental quality, economic measurements and indicators of, 305–6 Environmental refugees, 82 Environmental regulations, improving environmental quality with innovationfriendly, 307. See also Environmental law Environmental resistance, 77 Environmental revolution, 326, 327f Environmental science, 1, 6 Environmental security, global, 320–21 Environmental wisdom worldview, 18, 322f, 323 Environmental worldview(s), 17–18, 322–23 Epidemic, 228 HIV and AIDS, 230 Epidemiological studies on toxic chemicals, 236 Epiphytes, 74 Erosion. See Soil erosion Estuary, 61 Chesapeake Bay water pollution, 179f Ethanol as fuel, 217, 218, 219f Ethics. See Environmental ethics Euphotic zone, ocean, 61f Euphrates River, 160f, 161 European Union, 237, 286 European wild boar, 99 Eutrophication, 174 Eutrophic lake, 63 Evaporation, 40 Everglades, introduced snake species in, 102 Evergreen coniferous forests, 58 Evolution, 51–54 adaptation and, 52–53 geologic processes, climate change, and catastrophes affecting, 53–54 mutation and, 52 natural selection and, 52, 53f, 53–54 species extinction and (see Extinction of species) sustainability principles and, 64–65 theory of, 51–52 Executive branch of democratic governments, 312, 314f
I6
Existence value of species, 98 Experiments, scientific, 22 Exponential growth of populations, 15, 16f, 77f Extinction of species, 55–56, 93–108 amphibians and threat of, 69–71 background, 55, 93 biological, 93 endangered and threatened species and, 94–96 (see also Endangered species; Threatened (vulnerable) species) human activities as cause of, 94, 98–105 illegal killing or sale of species as cause of, 104 mass, 55 passenger pigeons, case study, 93 protecting species from extinction, 105–8 rates of, 94, 96b reasons for concern about, 97–99 role of climate change and pollution in, 55 Extinction rate, 96b Exurbs, 277 Family planning, 87–88 in China, 88–89 Federal Water Pollution Control Act of 1972, 181 Feeding niches of coastal-wetland birds, 68f Feedlots, 137, 142f Fee-per-bag waste collection systems, 287, 289 Fertility rate, 80 Fertilizers, inorganic and organic, 149–50 First law of thermodynamics, 30 Fish as food resource, 137–38 invasive species of, 128, 175 mutualism between sea anemone and clownfish, 74f sharks, 71–72 temperature range of tolerance in, 35f Fishery(ies), 133, 137–38 aquaculture, 137–38 management of, 127f marine, 126–27 Fitness, biological, 53 Flooding, 169–71 in Bangladesh, 170 damage to cropland caused by, 139–40 deforestation as cause of, 169f reducing risk of, 170–71 Flood irrigation, 166 Floodplains, 63, 64f, 169 Flowing (lotic) freshwater systems, 62 Food and Agricultural Organization (FAO), U.N., 111, 132, 320 Food chains, 37 bioaccumulation and biomagnification of toxins in, 103f energy flows in, 37, 38f, 39 Food insecurity, 132 Food production, 133–38. See also Agriculture crossbreeding and genetic engineering for, 137 effects of ozone depletion on, 271f energy required for, 138 environmental problems arising from, 138–43 fish and shellfish production, 137–38 green revolution in, 135 increase in, 133 industrialized, 133–38, 152f meat production, 137, 150 pest management and, 143–48
soil and, 136b (see also Soil) sustainable, 148–53 traditional methods of, 134–35 Food security, 132–33 improving, 148–53 Food web, 37 energy flow in, 37–39 in southern hemisphere, 38f Forest(s), 58, 115–17 age, types, and origins of, 111 climate change as threat to, 264 deforestation as threat to, 112–13, 114–15 ecological and economic services provided by, 111f, 112 effects of acid deposition on, 250 effects of ozone depletion on, 271f Green Belt movement in Kenya, 117b human impacts on, 59f nonviolent civil disobedience to protect, 319b reforestation of U.S., 113–14 sustainable management of, 115–17 tropical deforestation, 114–15, 116–17 U.S. national (see National Forest System, U.S.) unsustainable logging as threat to, 112, 113f Formaldehyde, 251–52 Fossil(s), 52 Fossil fuels, 33, 222 air emissions from burning, 248, 249 coal, 194–97 commercial energy supplied by, 188, 189f greenhouse gas emissions from, 259–60 natural gas, 193–94 nuclear power as alternative to, 197–203 oil, 189–93 Foundation species, 71 Fox, speciation of arctic and gray, 55f Freshwater conflict over supplies of, 160–61 groundwater, 156, 157f, 161–62 (see also Groundwater) increasing supplies of, 161–65 as mismanaged resource, 156 reducing waste of, 165–68 shortages of, 158–59 surface, 156, 157 in U.S., 157, 158f uses of, 159b water pollution in (see Water pollution) Freshwater life zones, 33, 62–64 ecological and economic services provided by, 62f human impact on, 64 inland wetlands, 63–64, 128 lakes, 62, 63f protecting biodiversity in, 128 streams and rivers, 63, 64f threats to, 127 Frogs, life cycle of, 69, 70f Frontier science, 23 Fuel(s) biofuels, 217–19 biomass, 217 carbon dioxide emissions, by select, 196f fossil fuels (see Coal; Fossil fuels; Oil) global energy sources by, 189f nuclear (see Nuclear energy) Fuel cells, 209, 220 Fuel economy, motor vehicle, 208 Fuel rods, nuclear, 200 Fuelwood shortage, 217
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Full-cost pricing, 281, 304, 306. See also Market prices Fuller, Richard Buckminster (Bucky), 243 Functional diversity, 50f Fungicides, 143 Gandhi, Mahatma, 319b, 324 Gasoline taxing, 282 true cost of, 208 Gasoline-electric hybrid car, 208, 209f Gender(s) as health risk, 237–38 imbalance of, 89 Gene(s), 27 relationship of cells, chromosomes, DNA and, 28f Gene banks, 106–7 Generalist species, 68 cockroaches as, 68–69b Gene revolution, 137 Genetically-modified food (GMF), 141f Genetically-modified organisms (GMOs), 137 Genetic diversity, 31, 50f, 52 Genetic engineering, 56, 137 changing genetic traits in populations through, 56b food production and, 141 Genetic information, preserving biodiversity for, 98 Genetic resistance, 52 of bacteria to antibiotics, 53f of crops to pests, 146 of pests, to pesticides, 145 Genetic variability (genetic diversity), 52 Genuine progress indicator (GPI), 305f, 306 Geographic isolation, speciation and, 55f Geologic processes, evolution and, 53–54 Geosphere, 32f, 33 Geothermal energy, 219–20 CO2 emissions from burning, 196f Geothermal heat pump system, 219 Giant pandas, 68 Glacial and interglacial periods in earth’s history, 258 Glacier National Park, U.S., 263 Glaciers, 41 climate change and melting, 263 Global cooling, 258 Global Environment Facility (GEF), 320 Global Governance Initiative Report, 321 Global warming, 258. See also Atmospheric warming; Climate change Global Water Policy Project, 173 Goldsteib, David, 203 Goods and services, resources needed to produce, 303f Government(s) democratic, 312–13, 314f energy policies of, 223 environmental leadership by, 268 environmental policy and (see Environmental policy) role of, in reducing threats of climate change, 266–68 role of, in reducing tropical deforestation, 116–17 subsidies provided by (see Subsidies) Grain crops, 133 conversion of, in to meat, 150f global, and per capita production of, 135f
Grameen Bank, Bangladesh, 309 Grasshopper effect, 248 Grassland(s), 57–58 human impacts on, 59f Grassroots environmental action, 297, 318–19 Gravity, 33 Gravity-flow irrigation, 166f Gray-air smog, 248 Great Lakes case study on pollution and cleanup in, 174–75 invasive species in, 128, 175 primary ecological succession on Isle Royal in, 75f Green architecture, 209 Green Belt Movement, Kenya, 117b Greenhouse effect, 246. See also Climate change; Greenhouse gases natural, 34 Greenhouse gases, 32, 34, 246 cap on emissions of, 266–67 carbon dioxide as (see Carbon dioxide (CO2) climate change due to human activities and emissions of, 259–61 methane as, 142, 246 nitrous oxide as, 43–44, 246 water vapor as, 246 Green manure, 149 Green revolution in agriculture, 135 limits to expansion of, 141–42 Green taxes, 306–7 Gross domestic product (GDP), 10, 305 genuine progress indicator (GPI) versus, 305–6 Gross primary productivity (GPP), 39 Groundwater, 41, 156, 157f pollution in, 175–76, 177f withdrawal of, 161–62 Gulf of Mexico, oil pollution in, 179–80 Habitat, 31, 68 species extinction due to fragmented, degraded, and lost, 98–99, 100f Habitat fragmentation, 99 Habitat islands, 98 Halons, 270 Hansen, James, on atmospheric warming and climate change, 261b, 265 Hardin, Garrett, 12 Harmful algal blooms (HABs), 179 Hawken, Paul G., 311, 325, 328 Hazard(s), 226–42 biological, 227–32 (see also Disease; Infectious disease) chemical, 227, 233–37 risk, risk assessment, risk management, and risk perception of, 227, 237–41 types of, 227 Hazardous chemicals. See Chemical hazards; Hazardous wastes sewage and, 182 Hazardous wastes, 285, 294–97 detoxifying, 294 grassroots action on management of, 297 in homes, 286f individual’s role in reducing, 296f integrated management of, 294 international treaties for reduction of, 297–98 regulation of, in U.S., 295, 296–97 storage of, 294–96
Health. See Human health Heat, 29 Heating net energy ratios for, 190f renewable energy for, 211 saving energy in, 210 solar, 211–13 space, 190f Heavy oils, 192–93 Heliostats, 212 Herbicides, 143 Herbivores (primary consumers), 35 Heritable trait, 52 Heterotrophs (consumers), 35, 36f High-input (industrialized) agriculture, 133. See also Industrialized (high-input) agriculture High-quality energy, 30 one-way flow of, and life on earth, 33f High-quality matter, 27, 28f High-temperature heat and electricity solar generation, 212, 213f High-temperature industrial heat, net energy ratio for, 190f High-throughput (high-waste) economy, 303f Hill, Julia Butterfly, 319b HIPPCO (Habitat destruction, degradation, and fragmentation; Invasive (nonnative) species; Population growth and increasing use of resources; Pollution; Climate change; Overexploitation) 98–99 Hirschorn, Joel, 241 HIV (human immunodeficiency virus), 85, 229 Homes indoor air pollution in, 247, 251, 252f net energy ratios for heating, 190f reducing energy use in, 210f reducing water use in, 167f, 168 solar-heated, 211, 212f toxic and hazardous chemicals in, 286f Homo sapiens sapiens, time on earth, 7f, 14 Hormonally active agents (HAAs), 234 Hormone(s) chemical hazards to human, 234 controlling insects by disrupting, 147 Hot, dry rock, 219 Human activities, environmental effects of, 9. See also Environmental problems; Natural capital degradation air pollution (see Air pollution) on aquatic life zones, 62, 64 on biodiversity, 59, 62, 64 on carbon cycle, 43 climate change, greenhouse gas emissions, and role of, 259–61 ecological footprint (see Ecological footprint, human) extracting, processing of mineral resources, 171 on nitrogen cycle, 43–44 pesticide use and, 103f, 144–46 on phosphorus cycle, 44–45 protection of wild species from, 105–8 species extinction threat due to, 94, 98–105 on terrestrial ecosystems, 59f unsustainable living, 310–11 on water (hydrologic) cycle, 42 water pollution as (see Water pollution) Human capital/human resources, 303 Human culture, ecological footprint linked to, 14–15
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Human health. See also Human nutrition biological hazards to, 227–32 chemical hazards to, 237, 233–37 effects of air pollution on, 247, 253 effects of ozone depletion and ultraviolet radiation on, 271, 272b effects of radiation on, 197–98 effects of water pollution on, 171 food production linked to problems of, 139f pesticides as threat to, 145 poisons and (see Poisons; Toxic chemicals) poverty as risk to, 16–17 risk, risk assessment, risk management, and risk perception of hazards to, 227, 237–41 smoking, tobacco, and damage to, 238–40 threats of climate change to, 264 types of hazards to, 227 in urban areas, 279 Human immunodeficiency virus (HIV), 85, 229 Humanities, 6 Human nutrition food security and, 133 hunger, malnutrition and, 132–33 overnutrition, 133 vitamins, minerals, and, 132–33 Human population age structure of, 83, 84–85 aging, 83, 85 crash of, 78 declines in, 85 factors influencing size of, 79–85 growth of (see Human population growth) influencing size of, 86–90 most populous countries, 79, 80f rapid decline in, 85 sustainability principles and control of, 90 in urban areas (see Urban areas; Urbanization) Human population growth, 79–85 age structure and, 83, 84f as cause of environmental problems, 15f birth/death rates and, 79, 80–82 exponential rate of, 15, 16f factors affecting, 79–80 fertility rates and, 80–82 migration and, 82–83 poverty and (see Poverty) slowing, 86–90 species extinction linked to, 103 uneven distribution and, 79 in U.S., 80, 84–85 Humility principle, environmental policy and, 313 Hunger, 132 Hybrid gas-electric vehicles, 208, 209f Hydrobromoflurocarbons (HBFCs), 270 Hydrocarbons, 26 Hydrogen, 25 Hydrogen as energy source, 220–21 motor vehicles powered by, 209 role of fuel cells, 209, 220 Hydrogen chloride, 270 Hydrological poverty, 160 Hydrologic (water) cycle, 40, 41f, 42, 156 effects of human activities on, 42 Hydroponics, 134 Hydropower, 30, 188, 214–15f Hydrosphere, 32f Hydrothermal reservoirs, 219 Hypereutrophic lakes, 63
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Ice, climate change and melting, 263 Igneous rock, 45 Immigration into United States, 82–83f urban growth and, 276 Immune system, chemical hazards to human, 234 Incandescent light bulb, energy waste by, 30, 206, 207 Incentive-based environmental regulations, 307 Incineration of biomass, to produce energy, 217 of fossil fuels, 194, 196f, 248, 249, 259–60 of solid wastes, 291, 292f India basic demographic data for, 88f human population in, 79, 80f slowing population growth in, 89 Indicator species, 69 amphibians as, 69–71 Indirect costs, 305 Individuals matter, 9, 18–19 R. Anderson and creation of sustainable corporation, 308b R. Carson on dangers of pesticides, 144b environmental policy and influence of, 268 J. Hansen on atmospheric warming and climate change, 261b J. Hill and protecting forests, 319b influencing environmental policy, 317, 318f, 319b A. Leopold and environmental ethics, 325b W. Maathai and Kenyan Green Belt movement, 117b protecting wild species, 108f reducing air pollution, 257f reducing CO2 emissions, 268f reducing energy use and waste, 210f reducing exposure to UV radiation, 271f reducing hazardous waste output, 296f reducing pesticide exposure, 145f reducing solid waste, 288f reducing threat of invasive species, 103f reducing water pollution, 184f reducing water use and waste, 168f S. Rowland and M. Molina discovery of ozone depletion, 270b reuse of materials, 289f sustainable energy future and, 224f sustainable food production, 153f sustaining terrestrial biodiversity, 125f D. Wilson on toxic chemicals cleanup, 318b E.O. Wilson as biodiversity champion, 51b Indoor air pollution, 247, 251–53 harmful health effects of, 253 individual’s role in reducing, 257f radioactive radon gas as, 252–53 reducing, 256, 257f types and sources of, 251, 252f Industrial ecosystems, 298, 299f Industrial heat, net energy ratios for hightemperature, 190f Industrialized (high-input) agriculture, 133 crop production, 133–34 green revolution and, 135 meat production, 137 organic agriculture versus, 152f in United States, 135–37, 152f Industrial-medical revolution, 14f Industrial smog, 248 Industrial solid wastes, 285
Industry brownfields and abandoned, 297 improving energy efficiency in, 207 reducing water use by, 167f, 168 water pollution caused by, 171 Infant mortality rate, 81, 82 Infectious agents. See Pathogens Infectious disease, 227–32 antibiotic resistance in bacteria and, 229b climate change and increased, 264 deadliest, 228f HIV and AIDS, 230 influenza, 229 malaria, 144–45, 230–32 reducing incidence of, 232 SARS, 230 tuberculosis, 228–29 viruses and parasites, 229–30 West Nile virus, 230 Influenza (flu), 229 Information-globalization revolution, 14f–15 Inland wetlands, freshwater, 63–64, 128 Innovation-friendly environmental regulations, 307 Inorganic compounds, 26 Inorganic fertilizers, 149–50 Insect(s) ants, 51b Argentine fire ants, 100, 102f bees, 69 cockroaches, 68b ecological role of, 32b sex attractants (pheromones) for, 147 Insecticides, 143 Institute for the Analysis of Global Security, 192 Instrumental value of species, 97 Integrated coastal management, 179 Integrated pest management (IPM), 147–48 Integrated waste management, 287 of hazardous waste, 294f of solid waste, 287f Intergovernmental Panel on Climate Change (IPCC), 260–61 validity of report conclusions of, 260b Internal combustion engine, energy waste by, 207 International agreements. See also Treaties global environmental policy and, 320–21 on hazardous waste, 286, 297–98 on protecting ozone layer, 271–72 reducing greenhouse emissions, and responding to threat of climate change, 267–68 International Basel Convention, 286, 297 International Convention on Biological Diversity, 126 International Union for Conservation of Nature (IUCN), 71, 94, 126, 320 Interspecific competition, 72 Intrinsic rate of increase (r), population growth, 77 Intrinsic value of species, 98 Introduced species. See also Nonnative species accidentally introduced, 99–102 deliberately introduced, 99, 101f in Great Lakes, 128, 175 Invasive species, 102. See also Nonnative species in Great Lakes, 128, 175 Iodine, as micronutrient, 132–33 Ionic compounds, 26
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Ions, 26 Ireland, human population crash in, 78 Iron, as micronutrient, 132 Irrigation major systems of, 166f reducing water wastage in, 166, 167f soil salinization and waterlogging caused by, 140f, 150f Island species, 98 Isotopes, 26 Israel, water resources in, 167 Jet airplane emissions, 262 Jordan River basin, 160–61 J-shaped curve of population growth, 16f Judicial branch of democratic governments, 312, 314f Kenya, Green Belt Movement in, 117b Kerogen, 193 Keystone species, 71–72, 119b Kinetic energy, 29 Kyoto Protocol, 267 Lakes, 62–63. See also Dams and reservoirs Aral Sea ecological disaster, 164–65 eutrophic, 63 eutrophication and cultural eutrophication in, 174 Great Lakes (see Great Lakes) hypereutrophic, 63 mesotrophic, 63 oligotrophic, 63 water pollution in, 173–75 zones of, 63f Landfills open dumps, 292 sanitary, 292, 293f secure hazardous waste, 295, 296f Land trust groups, 119–20 Lateral recharge, 156 Latitude, climate, biomes, and effects of, 244, 245f Law. See Environmental law Law of conservation of energy, 30 Law of conservation of matter, 29, 310 Law of nature (scientific law), 23 Law of thermodynamics, 30–31, 38f Lead as air pollutant, 246t health threat of, to children, 254 solutions for protecting children from poisoning by, 255f Learning skills, 1–4 importance of studying environmental science and, 1 improving critical thinking skills and, 2–3 improving study and, 1–2 learning styles and, 3–4 Legislative branch of democratic governments, 312, 314f Leopold, Aldo, 92, 129, 131 environmental ethics of, 325b Less-developed countries, 10. See also names of individual countries, e.g. India reducing poverty in, 308–10 stream pollution in, 173 urban poverty in, 280 Lethal dose (LD) of chemicals, 235t Levees, flood-control, 64 Life, organization of, 31f
Life expectancy, 82 AIDS and, 230 Lifestyle hazards, health risks of, 227, 237–38 smoking and, 238–40 Life-support systems, earth’s components of, 32–33 ecology, organization of life and, 31–32 major components of ecosystems and, 34–36 role of insects in, 32b role of microorganisms in, 36b solar energy. nutrient cycling, and gravity as factors of, 33 Light bulb, incandescent, 30, 206, 207 Light crude oil, 189 Light-emitting diodes (LEDs), 207 Lighting, energy-efficient, 207, 210 Light pollution, 280 Light-water reactors (LWR), nuclear, 198f nuclear fuel cycle in, 198, 199f Limiting factor principle, 34 Limiting factors in ecosystems, 34 population growth and, 77 Lipids, 27 Liquefied natural gas (LNG), 293 Liquefied petroleum gas (LPG), 193 Living machines, sewage treatment with, 183f Living roofs, 209 Living sustainably. See Sustainable living Lobbying, 306 Local extinction of species, 93 Logging threat of unsustainable, to forests, 112, 113f in U.S. national forests, 317b Logical learners, 4 Logistic growth of populations, 77f London, England, ecological footprint of, 279f Lovins, Amory, 206 Low-energy precision application (LEPA) sprinklers, 167 Low-quality energy, 30 Low-quality matter, 27, 28f Low-throughput economy, 311f Low-waste society, 297–99, 311f grassroots action, 297 industrial ecosystems for, 298, 299f international treaties, 297–98 sustainability principles and, 298–99 Maathai, Wangari, Green Belt Movement founded by, 117b, 266 Macromolecules, 26 Macronutrients, human nutrition and, 132 Malaria, 144–45, 230–32 global distribution of, 213f life cycle of Plasmodium parasite, 213f Malignant melanoma, 272b Malnutrition, 17, 132 Mangrove forest swamps, 61 Mantle, earth’s, 32f, 33 Manufactured inorganic fertilizer, 149, 150 Manufactured resources/manufactured capital, 303 Marine life zones, 33, 60. See also Ocean(s) coastal zone, 60, 61f (see also Coastal zones) ecological and economic services provided by, 60f, 61–62 human impact on, and degradation of, 62f open sea, 61f, 62 pollution in, 178–80 protecting biodiversity in, 125–27
Marine Mammal Protection Act of 1972, U.S., 126 Marine protected areas (MPAs), 126 Marine reserves, 126 Market-based economic systems, 305–8 encouraging innovation using laws and regulations, 307 environmental and economic indicators in, 305–6 including harmful environment costs in, 306 market prices and costs in, 305 reducing pollution and resource waste in, 307–8 rewarding environmentally-sustainable businesses in, 306 taxing pollution and waste in, 306–7 Market forces. See also Economics; Market prices improving environmental quality using, 305–8 reducing air pollution using, 255–56 Market prices, 305 of energy resources, 211, 223 exclusion of environmental costs from, 15f, 17 full-cost, 281, 304, 306 including environmental costs in, 306 increasing food security by controlling, 148 reducing automobile use with, 281–82 of water, 166, 168 Marriage, birth rate and average age at, 82 Marsh, freshwater, 63 Mass extinction, 55 Mass number, 25 Mass transit rail, trade-offs of, 282f Materials-flow economy, shift from, 307–8 Materials-recovery facilities (MRFs), 289 Matter, 21, 25–29 atoms, molecules, and ions of, 25–26 in ecosystems, 40–46 elements and compounds of, 25 genetic materials and cells of, 27, 28f law of conservation of, 29 organic and inorganic compounds and, 26–27 organization of, in nature, 31f physical and chemical changes in, 28–20 physical states of, 25 quality of, 27, 28f Matter cycling in ecosystems, 40–46 biogeochemical (nutrient) cycles and, 40 carbon cycle, 42–43 nitrogen cycle, 43–44 phosphorus cycle, 44–45 rock cycle, 45–46 water (hydrologic) cycle, 40–42 Matter quality, 27, 28f Matter-recycling-and-reuse economy, 310 Mature soils, 136 Meat production, 137 animal feedlots, 142f conversion of grain into meat, 150f environmental costs of industrialized, 142 sustainable, 150 Median lethal dose (LD50), 235 Megacities/megalopolis, 276f, 278f Megareserves, 121 Mercury, toxic effects of, 233b Mesotrophic lake, 63 Metallic mineral resources, 9 Metamorphic rock, 45 Methane (CH4) atmospheric levels of, over time, 259f
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I9
Methane (CH4) (cont’d) as greenhouse gas, 142, 246 melting permafrost and release of, 263 regulating emissions of, 266 Methane hydrates, 193 Methyl bromide, 270 Metropolitan areas. See Urban areas Mexico City, environmental problems of, 280 Microbes (microorganisms), 36b, 98. See also Bacteria Microirrigation, 167 Microlending (microfinance), 309 Micronutrients, human nutrition and, 132 Microorganisms (microbes), ecological role of, 36b, 98. See also Bacteria Micropower generators, 215 Middle East, water conflicts in, 160, 161f Migration, population size and, 82–83 Military security, 320 Millennium Development Goals, strategies for achieving, 309, 310f Millennium Ecosystem Assessment (2005), 10, 44 Mineral resources, metallic and nonmetallic, 9–10 Minerals, human nutrition and, 132–33 Mining water pollution caused by mineral, 171 of water resources, 156 Models, scientific, 23 Molecular compounds, 26 Molecule(s), 26, 31f Molina, Mario, 270b Monoculture, 133–34 Monomer, 26 Montreal Protocol, 271–72, 321 More-developed countries, 10. See also names of individual countries, e.g. Canada Mosquito as disease vector, 144-45, 231f, 265f Motor vehicles, 208–9 advantages and disadvantages of, 281 air pollution caused by, 246t, 247f alternatives to cars, 282f, 283f car-centered societies, 281 ethanol fuel for, 217, 218, 219f fuel cell, 209 hybrid gas-electric, 208, 209f reducing air pollution from, 256f reducing use of, 281–82 in United States, 208 Mountain(s), 58 human impacts on, 59f MSW. See Municipal solid waste Multidrug resistant TB, 229 Multilateral environmental agreements (MEAs), 321 Multiple cropping, 135 Municipal solid waste (MSW), 285 recycling, 289 in U.S., 286, 289 Mutagens, 52, 233–34 Mutations, 52 biological evolution and, 52, 53f caused by toxic chemicals, 233 Mutualism, 73–74f Myers, Norman, 320 National Forest System, U.S., 114, 314, 316f logging in, 317b nonviolent civil disobedience to protect, 319b National Marine Fisheries Service (NMFS), U.S., 106
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National parks, 118–21 environmental threats to, 118, 263 U.S., 118, 119b, 314–15, 316f National Park Service, U.S. (NPS), 315 National Park System, U.S., 118, 119b, 314–15, 316f National Priorities List, U.S., 296 National security climate change as issue of, 263 environmental policy and, 320–21 National Wilderness Preservation System, U.S., 315 National Wildlife Refuges, U.S., 314, 316f Native species, 69 Natural capital, 8f–9, 303 atmosphere as, 244f biodiversity as, 50f biomes as, 57f carbon cycle as, 42f climate as, 245f earth structure as, 32f economic systems supported by, 303 ecosystem components as, 37f failure to value, in market prices, 17 food production as, 134f forests as, 111f freshwater systems as, 62f groundwater system, 157f hydrologic (water) cycle as, 41f marine ecosystems as, 60f nitrogen cycle as, 44f nonrenewable energy sources as, 188f pharmaceutical plants as, 97f phosphorus cycle as, 45f rivers as, 163f rock cycle as, 46f species as vital part of earth’s, 97–98 temperature, precipitation, and terrestrial ecosystems, 58f Natural capital, endangered and threatened, 95f, 96f in biodiversity hot spots, 123f Natural capital, lost, 93f Natural capital degradation, 9, 10, 11f acid deposition as, 249f of coastal zones and ocean ecosystems, 178f deforestation, 113f, 115f, 169f ecological footprint, 13f food production linked to, 139f, 140f groundwater pollution, 176f in marine ecosystems and coral reefs, 62f ozone depletion as, 271f of soil resources, 139f, 140f species extinction and depletion due to, 99f, 100f in terrestrial ecosystems, 59f in urban areas, 279f urban sprawl as, 278f of water resources, 160f, 169f, 176f, 178f Natural gas, 193–94 CO2 emissions from burning, 193, 196f sustainable energy future and role of, 222 trade-offs of conventional, 194f Natural greenhouse effect, 34, 246 Natural income, 18 Natural recharge, 156 Natural resources, 8f. See also Natural capital; Resource(s) Natural sciences, 6 Natural selection, 52 adaptation through, 52–53
Natural services, 8f Natural systems, tipping points in, 14, 265f Nature Conservancy, 119 Nature reserves, 118–20 biosphere, 120f in Costa Rica, 120–21 wilderness as, 121 Nelson, Gaylord, 302 Neoclassical economists, 303 Nervous system, chemical hazards to human, 234 Net energy, 188, 190b Net energy principle, environmental policy and, 313 Net energy ratios, 190b Net primary productivity (NPP), 39 in coastal-zone primary productivity, 61 estimated average, of select ecosystems, 40f in open sea, 61–62 Neurotoxins, 234 lead as, 254, 255 Neutrons (n), 25, 26f New urbanism, 284 Niche, 68. See also Ecological niche Nile River water resources, 160 Nitrate ions, 43, 175 Nitric acid (HNO3) as air pollutant, 246t Nitrification, 43 Nitrite ions, 43 Nitrogen, 25 Nitrogen cycle, 43, 44f human impact on, 43–44 Nitrogen fixation, 43 Nitrogen-fixing bacteria, 43 Nitrogen oxide (NO) as air pollutant, 246t Nitrous oxide (N2O), 43–44, 246 Noise pollution, 280 Nonbiodegradable pollutants, 11 Nondegradable wastes in water, 176 Nongovernment organizations (NGOs), environmental policy and, 313, 314f, 318–19 Nonmetallic mineral resources, 10 Nonnative species, 69. See also Introduced species in Great Lakes, 128, 175 human introduction of, 99–102 in national parks, 118 preventing threats from, 102, 103f Nonpoint sources of pollution, 11 water pollution, 171, 180–81 Nonrenewable aquifers, 156 Nonrenewable energy, 187–204 coal, 194–97 natural gas, 193–94 net energy and, 188–89 nuclear energy, 197–203 oil, 189–93 sustainability principles and, 203 Nonrenewable resources, 9–10 Nonthreshold dose-response model, 235 Nontransmissible disease, 228 Nonviolent civil disobedience, 319b Nuclear energy, 197–203 CO2 emissions from fuel cycle, 196f Chernobyl nuclear plant accident, 200 fuel cycle, 198, 199f future of, 202–3 history of, 199–200 new generation nuclear reactors, 202 nuclear fission reactors, 197–99
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
nuclear fusion and, 202 problem of aging and worn-out reactors, 201 radioactive waste produced by, 201 reducing dependence on imported oil by using, 201–2 spent fuel rods as environmental risk, 200 sustainability principles and, 203 trade-offs of conventional fuel cycle, 200f Nuclear fission, 197–99 Nuclear fission reactors, 198f accidents at, 200 decommissioning old, 201 energy waste by, 207 radioactive waste produced by, 200, 201 Nuclear fuel cycle, 198, 199f Nuclear fusion, 202 Nucleic acids, 27 Nucleus (atom), 25, 26f Nutrient(s), 6, 33 Nutrient cycles (biogeochemical cycles), 40–46 Nutrient cycling, 9f, 33, 40–46 sustainability principles and, 6, 7f, 8 Nutrition. See Human nutrition Ocean(s), 33, 60. See also Marine life zones acidity of, 262 as carbon dioxide-storage and heat reservoir, 261–62 climate change and rising levels of, 263–64 coastal zones 60, 61f, 126–27, 178–79, 180f ecological and economic services provided by, 60–62 energy produced by tides and waves of, 215 open sea of, 61f pollution (see Ocean pollution) Ocean currents, climate and, 245f, 246 Ocean pollution, 178–80 Chesapeake Bay estuary as case study, 179f coastal areas affected by, 178–79 oil as cause of, 179–80 solutions for protecting coastal waters, 180f sources of, 178f Ogallala Aquifer, 161 Oil, 189–93 advantages/disadvantages of conventional, 192f CO2 emissions from burning, 196f crude, 180, 189 dependence on, 189–90 oil shale and oil sands as sources of heavy, 192–93 refining of crude, 190, 191f reserves of, 191–92 as water pollutant in oceans, 179–80 Oil sand, 192, 193f Oil shale, 192, 193f Old-growth forests, 111, 319b Oligotrophic lake, 63 Omnivores, 35 Open-access renewable resources, 12 Open dumps, 292 Open sea, 61f Opportunist species, 78 Oral rehydration therapy, 232 Organic agriculture, 151–52f, 180–81 Organic compounds, 26–27, 285 Organic fertilizers, 149, 266 Organism(s), 6, 31f–34 See also names of specific organisms, eg. Animal(s) genetically modified, 137, 141f limiting factors on, 34
Organization of Petroleum Exporting Countries (OPEC), 191 Outdoor air pollution, 246–51 acid deposition and, 249–51 factors influencing levels of, 248 industrial smog as, 248 major pollutants, 246t, 247 photochemical smog as, 248 potential effects on climate change, 262 preventing and reducing, 256f, 257f Overconsumption, species extinction linked to, 103 Overgrazing, 78 Overnutrition, 133 Overshoot, population, 77–78 Oxygen, 25 Oxygen sag curve, 172, 173f Ozone (O3) as air pollutant, 246t in stratosphere, 32, 244, 269–72 Ozone hole, 270 Ozone layer, 244 Ozone layer, depletion of, 269–72 chemical causes of, 269–70 discovery of, 270b at earth’s poles, 270 effects of, 271, 272b reasons for concern about, 271 reversing, 271–72 reducing exposure to UV radiation linked to, 271f Ozone thinning, 270 Pandemic, 228 Parasitism and parasites, 73 Parks. See National parks Passenger pigeon, extinction of, 93 Passive smoking, 239 Passive solar heating system, 211, 212f Pastures, 133 Pathogens, 227. See also Disease; Infectious disease antibiotic resistance and immunity of, 53f, 229b entry pathways into human body, 228f Pay-as-you-throw (PAUT) waste collection system, 289 Peak production, 189–90 Peer review, 23 Pension systems, birth rates and availability of, 80–81 Peracelsus, 226 Per capita ecological footprint, 12, 13f Per capita GDP, 10, 305 Permafrost, 33 climate change and melting, 263 Perpetual resource, 9 Persistent organic pollutants (POPs), 146, 237, 297–98 Pest(s), 32b, 143 alternative methods of controlling, 146–48 chemical control of, 143–46 natural enemies of, 143 Pesticides, 143–44 advantages of modern synthetic, 144–45 alternatives to, 146–48 bioaccumulation and biomagnification of DDT, 103f R. Carson on environmental effects of, 144b disadvantages of modern synthetic, 145 effectiveness of, 146b
laws and treaties to protect from harmful effects of, 146 reducing individual exposure to, 145f trade-offs of conventional chemical, 144f Petrochemicals, 190 Petroleum, 179, 189. See also Oil pH, 26 scale, 27f Pheromones, controlling insects using, 147 Phosphorus cycle, 44, 45f human impact on, 45 Photochemical reaction, 248 Photochemical smog, 248 Photosynthesis, 6, 30, 35, 43 Photovoltaic (PV) cells, 213f Physical change in matter, 28 Physical hazards, 227 Phytoplankton, 35, 71 Phytoremediation of hazardous waste, 294 Planetary management worldview, 18, 322f Plant(s). See also Tree(s) biofuels produced from, 217–19 botanical gardens and arboreta for protection of, 107 epiphytes, 74 pharmaceutical, 97f Plantation agriculture, 133–34 Plasmodium parasite, 231f Plastics, 171 bioplastics, 290b recycling, 290 Plug-in hybrid electric vehicles, 208, 209f Poaching, 104 Poincaré, Henri, 21 Point sources of pollution, 11, 171 water pollution, 171, 181 Poisons, 246t. See also Toxic chemicals arsenic, 175–76 lead as, 254, 255f pesticides and circle of, 146 toxicity ratings and lethal doses for, 235t Polar bears, climate change and extinction threat to, 103–4 Polar ice sheets, climate change and melting, 263 Policy. See Environmental policy Politics, 312–21 in democracies, 312–13, 314f environmental citizen groups in, 318–19 environmental student groups, schools, and, 319–20 environmental laws and, 314f, 315f, 316–17 environmental policy development, 313 global environmental security and, 320–21 individual’s role in environmental policy, 317, 318f, 319b public lands management in U.S. and, 313–16 sustainable energy future and, 222–24 Pollan, Michael, 153 Pollutants, 11. See also Air pollutants; Water pollutants Polluter-pays principle, environmental policy and, 313 Pollution, 11–12 air (see Air pollution) biodegradable, and nonbiodegradable, 11 economic solutions for (see Economics) light, 280 marketplace solutions for waste and, 307–8 noise, 280 point, and nonpoint sources of, 11
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Pollution (cont’d) prevention versus cleanup of, 11–12 (see also Prevention approach) species extinction linked to, 103 taxes on, 306–7 tradable, 307 in urban areas, 279 water (see Water pollution) Pollution cleanup (output pollution control), 11 Pollution prevention (input pollution control), 11–12. See also Prevention approach Polyculture, 134, 135 Polymer, 26 Population(s), 31f–32. See also Human population; Human population growth; Population dynamics biotic potential of, 76–77 carrying capacity and size of, 77–78 genetic engineering of traits in, 56b limits on growth of, 76–78 range of tolerance in, 34, 35f reproductive patterns of, 78 Population change, calculation of, 79 Population crash, 78 Possibility, risk and, 227 Postconsumer wastes, recycling of, 289 Potential energy, 29 Poverty, 16–17, 308–10 achieving Millennium Development Goals, 309–10 environmental problems caused by, 15f, 16–17 food security, hunger, malnutrition and, 132 harmful effects of, 17f as human health risk, 237–38 hydrological, 160 microlending as solution for, 309 priorities and costs of reducing, 310f strategies for reducing, 309 in urban areas, 277, 280 wealth gap and, 308–9 Power tower, 212 Prairie potholes, 63 Precautionary principle. See also Prevention approach chemical hazards and, 237 environmental policy and, 313 Precipitation, 34, 40–41 acid deposition, 249–51 climate, biomes, and average, 56, 57f, 58f, 244, 245f climate change and reduced, 263 as surface water, 63 in U.S., 158f Preconsumer waste, recycling of, 289 Predation, 72–72 Predator-prey relationship, 72 Predators, 72 wolves, in national parks, 119b Prevention approach to acid deposition, 251f to air pollution, 256f, 257f to chemical hazards, 237 climate disruption, 266f flood-damage reduction, 170f groundwater depletion, 162f integrated pest management as, 147 to introduced, invasive species, 102 to lead poisoning, 255f to soil salinization, 150f to water pollution, 176, 177f, 180f
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Prevention principle, environmental policy and, 313 Prey species, 72 Prices. See Market prices Primary air pollutants, 247f Primary consumers (herbivores), 35 Primary ecological succession, 74, 75f Primary (closed-loop) recycling, 289 Primary sewage treatment, 182, 183f Private property, 12 Probability, 24b risk and, 227 Producers (autotrophs), 35–36 Profit-making organizations, 312–13 Proteins, 27 conversion of grain into animal, 150f Protons (p), 25, 26f Proven oil reserves, 191–92 Public lands in United States, 313–16 national forests, 114, 314, 316f Pyramid of energy flow, 39f Radiation, ultraviolet. See Ultraviolet (UV) radiation Radioactive isotopes (radioisotopes), 197 Radioactive radon gas, 246t, 252–53 Radioactive wastes, high-level, 201 Radon gas, radioactive, 246t, 252–53 Rain. See Precipitation Rangelands, 133 Range of tolerance, 34 for temperature, 35f Rapid rail as transportation, 282, 283f Reconciliation ecology, 124 Blackfoot Challenge as, 124–25 Recycling, 10, 289–91 advantages and disadvantages of, 291 of biodegradable solid wastes, 290 encouraging, 291 of household solid wastes, 289 by industry, to save money and energy, 207 of plastics, 290 two types of 289 Red Lists, IUCN, 94, 126 Red tides, 178f Rees, William, 12, 279f Refined oil, 180 Refined petroleum, 179 Refinery, oil, 190, 191f Rehabilitation of ecosystems, 122–23 Reindeer, excessive population growth of, 78f Reliable science, 23 Reliable surface runoff, 157 Religious beliefs, 82 Renewable energy, 266 biomass, 217–19 geothermal, 219–20 hydrogen, 220–21 hydropower, 214–15 solar, 211–14 wind, 215–16 Renewable resources, 9 biodiversity as, 51 degradation of, 11f tragedy of the commons and degradation of, 12 Replacement-level fertility rate, 80 Replacement of ecosystems, 123 Reproduction, differential, 52 Reproductive isolation, speciation and, 55f Reproductive patterns, 78
Reproductive time lag, 78 Reservoirs. See Dams and reservoirs Resource(s), 9–10. See also Natural capital common-property, 12 ecological footprint affecting, 12–13 environmental degradation of (see Natural capital degradation) environmental problems and unsustainable use of, 15f, 16 nonrenewable, 9–10 perpetual, and renewable, 9 (see also Renewable resources) tragedy of the commons in caring for, 12 Resource Conservation and Recovery Act (RCRA), U.S., 296 Resource partitioning, 72, 73f Resource-use permits, 307 Respiratory system, effects of air pollutants on human, 17 Response to toxic chemicals, 234, 235f Reuse, 10, 287–88 encouraging, 291 individual’s role in, 289f for reducing solid waste, 288 refillable containers as, 288–89 Reversibility principle, environmental policy and, 313 Rhinoceros mutualism between birds and black, 74f reduced range of black, 100f Risk, 227 perception of, 240–41 principles for assessment of, 241 probability, possibility, and, 227 of technologies, 240 Risk analysis, 237–38 Risk assessment, 227, 237 principles for, 241 of toxic chemicals, 234–37 Risk communication, 237 Risk management, 227, 237 Rivers. See also Streams flow zones in, 64f in Middle East, 160f pollution in, 172–73 stresses on global systems of, 160f in U.S., 158f RNA (ribonucleic acid), 27 Road-building into forests, 112f, 114 Rock, 45 Rock cycle, 45, 46f Rodenticides, 143 Rosenzweig, Michael L., 124 Rowland, Sherwood, 270b Runoff, 63 reliable, 157 surface, 41, 156, 157 Russia, natural gas reserves in, 194 Salinity of aquatic life zones, 60 as ecosystem limiting factor, 34 Salinization of soils, 140f solutions for, 150f Salt marsh, 61 A Sand County Almanac (Leopold), 325 Sanitary landfill, 292, 293f Sanitation, human health and, 232 SARS (severe acute respiratory syndrome), 230 Saudi Arabia, oil reserves in, 191 Savanna, 114
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Science, 21, 22–25 environmental, 1, 6 hypotheses in, 22–23 limitations of, 24–25 process of, 22f, 23 results of, 23–24 theories and laws of, 23 Science Focus biodiversity hotspot in east Africa, 123b bioplastics, 290b capturing and storing carbon dioxide, 267b ecological role of insects, 32b ecological role of microorganisms, 36b effectiveness of pesticides, 146b Endangered Species Act, 107b genetic engineering, 56b genetic resistance to antibiotics, 229b gray wolf reintroduced into Yellowstone Park, 119b “just right” conditions for life on earth, 54b living machines for sewage treatment, 183b logging in U.S. national forests, 317b mercury, toxic effects of, 233b net energy, 190b skin cancer and UV exposure, 272b smart grid, 207b soils, 136b statistics and probability, 24b validity of IPCC conclusions on climate change, 260b water footprints and virtual water, 159b Scientific consensus, 23 Scientific hypotheses, 22, 23 Scientific law (law of nature), 22f, 23 Scientific methods, 22 Scientific solutions, 9 Scientific theory, 22f, 23 Scientists, 22–25 process followed by, 22f Sea anemone, mutualism between clownfish and, 74f Seafood, 137, 138f Sea lamprey, 128 Sea levels, climate change and rising, 263–64 Seasonal wetlands, 63 Seawater, desalination of, 165 Secondary air pollutants, 247f Secondary consumers, 35 Secondary ecological succession, 75, 76f Secondary recycling, 289 Secondary sewage treatment, 182, 183f Second-growth forests, 111 Second law of thermodynamics, 30, 38f, 310 Secure hazardous waste landfills, 295, 296f Sedimentary rock, 45 Seed bank, 106–7 Selective cutting, tree harvesting by, 112, 113f Self, Peter, 275 Septic tank, 182f Service-flow economy, shift to, 307–8 Sewage, reducing water pollution through treatment of, 182–83 Shale oil, 193 Shantytowns, 280 Sheep, logistic population growth of, on Tasmania, 77f Sick-building syndrome, 251 Silent Spring (Carson), 144b Simple carbohydrates, 26 Simple living, 324–25, 326f Skin cancer, UV radiation and, 272b
Slash-and-burn agriculture, 134–35 Slowly degradable wastes in water, 176 Slums, 280 Smart grid, 207b Smart growth, 283, 284f Smog, 248 Smoking health hazards of, 238–40 indoor air pollution caused by, 251 Snakes, introduced species of nonnative, 100, 101f in U.S. Everglades, 102 Soil, 136b erosion of (see Soil erosion) food production and degradation of, 139f, 140 impact of food production on, 136 profile of, 136f restoring fertility of, 149–50 Soil conservation, 148–49 fertilizers and, 149–50 solutions for soil salinization, 150f tillage methods for, 148, 149 Soil erosion, 139–40 farming methods to reduce, 148–49f, 180 food production as cause of, 139f, 140f global, 140f salinization, and waterlogging as, 140f Soil fertility erosion and loss of, 139–40 restoring, 149–50 Soil horizons, 136f Soil profile, 136f Solar cells, 213f, 214f Solar cookers, 212–13 Solar energy, 6, 30, 211–14 flow of energy to and from earth, 33f generating high-temperature heat and electricity with, 212–13 heating buildings and water with, 211, 212f natural greenhouse effect and, 34, 246 solar cells to produce electricity, 213–14 sustainability principles and reliance on, 6, 7f Solar thermal systems, 212–13 Solid biomass, energy production from, 217 Solid wastes, 285–93 biodegradable, 290 burning, 287, 291, 292f burying, 287, 292–93 electronic, 286 grass roots action on management of, 297 hazardous (see Hazardous waste) individual’s role in reducing, 288f industrial, 285 integrated management of, 287f municipal (MSW), 285, 289 producing less, and reducing amount of, 287–88 recycling to reduce amount of, 287, 289–91 reuse as method of reducing, 287, 288, 289f, 291 transition to society low in, 297–99 in United States, 285–86 Solutions, 9 for acid deposition, 251f air pollution, 256f, 257f for coastal water pollution, 180f decentralized micropower system, 222f fisheries management, 127f groundwater depletion, 162f international environmental treaties as, 321f
lead poisoning, 255f low through-put economy, 311f megareserves, 121f national parks management, 119 preparing for climate change, 269f principles of sustainability (see Sustainability principles reducing energy waste, 206f reducing flood damage, 170f reducing infectious disease, 232f reducing water pollution, 184f reducing water waste, 167f sanitary landfills, 293f sewage treatment systems, 183f for slowing climate disruption, 266f smart growth tools in urban areas as, 284f for soil salinization, 150f sustainability principles and, 9 sustainable aquaculture, 151f sustainable water use, 168f sustaining tropical forests, 117f tools for shifting to sustainable economies, 311f waste-to-energy incineration as, 292f Soot in atmosphere, 246t, 262 Source zone in streams, 63, 64f Space heating, net energy ratios for, 190f Special-interest groups, 312 Specialist species, 68 Speciation, 54–55f Species, 6, 31 competitor, 78 endemic, 55, 98 evolution of, 51–54 extinction of, 55–56 (see also Extinction of species) foundation, 71 generalist, 68–69 indicator, 69–71 interactions among, 72–74 introduced, 99–102 keystone, 71–72 native, 69 nonnative, 69 (see also Nonnative species) opportunist, 78 preservation of (see Ecosystem approach to sustaining biodiversity; Species approach to sustaining biodiversity) roles of, in ecosystems, 68–72 specialist, 68 Species approach to sustaining biodiversity, 92–109 background and biological extinctions of species and, 93–94, 96b (see also Extinction of species) endangered and threatened species and, 94–96 human acceleration of species extinction, 98–105 protecting wild species from human activities, 105–8 reasons for concern about species extinctions, 97–98 Species diversity, 50f. See also Biodiversity Squamous cell skin cancer, 272b Squatter settlements, 280 S-shaped curve of population growth, 16f Standing (lentic) freshwater systems, 62 State of the Marine Environment, 178 Statistics, 24b Stewardship environmental worldview, 18, 322f
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Stratosphere, 32, 244f ozone depletion in, 269–72 Streams, 63. See also Rivers channelization of, 170 flow zones in, 64f pollution in, 172, 173f Strip cropping, 148, 149f Strip cutting in forests, 112, 113f Strong, Maurice, 187 Student environmental groups, 319–20 Subsidies, 114 for energy resources, 208, 211 increasing food security with government, 148 for nuclear energy, 199, 202 for reuse and recycling, 291 shifting, 304 reducing water wastage using, 166 Sulfur dioxide (SO2) as air pollutant, 246t emissions trading of, 256, 307 Sulfuric acid as air pollutant, 246t Sun. See Solar energy Superfund Act, U.S., 296 Superinsulation, 209 Surface impoundment of hazardous waste, 295 Surface runoff, 41, 156 reliable, 157 Surface water, 63, 156 reducing pollution in, 180–81 Suspended particulate matter (SPM) as air pollutant, 246t, 247 Sustainability, 302–29 components of, 8–9 economics and, 303–12 environmental citizenship and, 323–28 environmental worldviews and, 322–23 levels of, 10 politics and, 312–21 poverty reduction and, 308–10 principles of (see Sustainability principles) Sustainability principles, 6, 7f, 8, 327–28 air pollution, climate change, ozone depletion and, 272 biodiversity, evolution, and, 65–65, 129 food production and, 152–53 energy and, 223–34 hazards and risks to human health, 241 matter, energy, ecosystems, and, 46 nonrenewable energy and, 203 population, population growth, and, 90 protecting wild species using, 107–8, 129 reducing solid and hazardous waste, 298–99 reducing water pollution and, 183–84 risk assessment and, 241 water resources, water pollution, and, 184 Sustainability revolution, 15 Sustainable agriculture, 151f Sustainable energy future, 221–24 economics, politics, education, and, 222–24 energy policies and, 221 individual’s role in, 224f solutions to create, 222, 223f transition from centralized macropower to decentralized micropower system, 221, 222f Sustainable living, 323–28 environmental citizenship, 325 environmental ethics and, 322, 325b environmental literacy and, 323, 324f learning from the earth, 324 living more simply as, 324–25, 326f sustainability principles and, 327–28 vision for, 326, 327f
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Sustainable yield, 9 Swamps, 63 Switchgrass, 218, 266 Synfuels, 197 Synthetic natural gas (SNG, synfuels), 197f Taigas, 58 Tanzania, biodiversity hotspots, 123b Tar sand, 192, 193f CO2 emissions from burning, 196f Taxes and fees, 194, 196f carbon, and energy, 266 green, 306–7 on pollution and waste, 306–7 shifting, 304, 306–7 Technology estimating risks of, 240 innovations in, and human ecological footprint, 14f transfer of, to reduce threat of climate change, 267 Tectonic plates, 53 Temperate deciduous forests, 58 Temperate rain forests, 58 Temperature biomes, climate, and average, 56, 58f, 244, 245f (see also Climate; Climate change) of earth, as favorable for living organisms, 54b global atmospheric, 259f, 260f range of tolerance for, 35f Temperature inversions, 248 Tentative science, 23 Teratogens, 234 Terracing, 148, 149f Terrestrial life zones. See also Biome(s) ecosystem approach to preserving biodiversity in, 122–25 ecological succession in, 74–76 human impacts on, 59f net primary productivity of, 40f Terrorism, 192 nuclear technology and potential, 200 Tertiary consumers, 35 Thermodynamics, laws of, 30–31, 310 Thoreau, Henry David, 19 Threatened (vulnerable) species, 94–96, 100f birds, 104–5 polar bears, 103–4 Threshold dose-response model, 235 Tiger, reduced range of Indian, 100f Tigris-Euphrates River basin, 160f, 161 Tillage methods for soil conservation, 148, 149f Timber, harvesting methods, 112, 113f Tipping point, 14, 265f Tobacco and smoking as cause of indoor air pollution, 251 health effects of, 238–40 Todd, John, 155 Toilet systems, composting, 168, 183 Topsoil A horizon, 136f erosion of, 139, 140f Total fertility rate (TFR), 80 in United States, 81f Toxic chemicals, 233 as air pollutants, 246t determining toxicity of, 234–37 harmful effects of, on human body, 233–34 human body’s response to, 234, 235f mercury as, 233b persistent organic pollutants (POPs), 146, 237
prevention and precautionary principle applied to, 237 reasons for lack of knowledge about, 236 sewage and, 182 Toxic heavy metals, 285 Toxicity, 234 case reports and epidemiological studies to determine, 236 dose, response, and ratings of, 234, 235f factors affecting, 234 laboratory studies to determine, 234–36 of trace levels of chemicals, 236 Toxicology, 234–37 Toxic wastes, 285. See also Hazardous wastes Trace levels of toxic chemicals, 236 Trade-offs, 9 of animal feedlots, 142f of aquaculture, 143f of bicycles, 282f of biomass energy production, 217f of bus transportation, 282f of cap-and-trade policies, 267f of chemical pesticides, 144f of coal as energy source, 196f of conventional natural gas as fuel, 194f of conventional oil as energy source, 192f of dams and reservoirs, 163f of deep-well disposal of hazardous wastes, 295f of ethanol fuel, 219f of genetically-modified crops and foods, 141f of geothermal energy, 220f of global efforts to solve environmental problems, 321f of groundwater withdrawal from aquifers, 161f of heavy oils from oil shale and tar sand, 193f of hydrogen as energy source, 221f of large-scale hydropower, 215f of mass transit rail, 282f of nuclear fuel cycle, 200f of oil shale and oil sand fuels, 193f of passive or active solar heating, 212f of rapid-rail systems, 282, 283f of recycling, 291f of sanitary landfills, 293f of solar cells, 214f of solar energy for high-temperature heat and electricity, 213f of surface impoundments of hazardous waste, 295f of synthetic fuels, 197f of waste-to-energy incineration, 292f of wind power, 216f Traditional intensive agriculture, 134–35 Traditional subsistence agriculture, 134–35 Tragedy of the commons, 12 Trait, genetic, 27, 52 adaptive, and heritable, 52 genetic engineering of, 56b Transition zone in streams, 63, 64f Transmissible diseases, 227. See also Infectious disease Transpiration, 41 Transportation motor vehicles, 208, 209f net energy ratios for, 190f saving energy in, 208–9 in urban areas, 281–83 Treaties. See also International agreements on electronic wastes, 286
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
international environmental, as solution, 321f protecting endangered species with international, 105 for reducing hazardous wastes, 297–98 reducing use of ozone-depleting chemicals, 271–72 Tree(s). See also Forest(s) climate regulation and role of, 266 harvesting methods, 112, 113f Tree farms, 111f Tree plantations, 111f Trickle irrigation, 167 Trophic levels in ecosystems, 35, 38f Tropical forests, 111 deforestation of, 98, 114, 115f pharmaceutical plants from, 97f reducing deforestation in, 116–17 reforestation in Kenya, 117b sustaining, 117f, 266 Tropical rain forests, 58 Troposphere, 32, 244f greenhouse gases and warming of (see Atmospheric warming; Climate change) Tuberculosis, 228–29 Tundra, 58, 63 Ukraine, nuclear power plant accident in, 200 Ultralight and ultrastrong materials, 209 Ultraviolet (UV) radiation, 32, 33, 246 ozone depletion and human health problems caused by, 271f, 272b reducing exposure to, 271f stratospheric ozone layer as protection from, 244 Unconventional natural gas, 193 Undernutrition, chronic, 132 United Nations Conference on Environment and Development (UNCED), 321 United Nations Conference on the Human Environment, 321 United Nations Development Programme (UNDP), 320 United Nations Environment Programme (UNEP), 117, 139, 178, 320 United States affluence and resources consumption in, 16 baby boom generation in, 80, 81f, 84–85 Bowash megalopolis in, 278f changes in life quality (years 1900-2000), 81f commercial energy in, 189f, 206f deaths from air pollution in, 253f deaths from tobacco use and smoking in, 238, 239f ecological footprint of, 12 environmental law in (see Environmental law) ethanol production in, 218 Everglades, introduced snake species in, 102 forest re-growth in, 113–14 freshwater resources in, 157, 158f geothermal energy in, 219 Great Lakes invasion by alien species, 128, 175 Great Lakes pollution, 174–75 groundwater withdrawal in, 161, 162f high-level radioactive wastes in, 201 human population in, 79, 80f, 81f immigration to, 82–83 industrialized food production in, 135–37, 152f infant mortality rate in, 82 land use in, 208 mosquitoes as disease vector in, 265f motor vehicle use in, 281
oil reserves and oil use in, 191f overgrazing in, 78 public lands in, 114, 313–16 recycling in, 286, 289 solid waste production in, 285–86 urbanization in, 277, 278f water-deficit regions in, 158f water pollution in, 175, 176f, 181 wilderness in, 121 U.S. Energy Information Agency, 192 U.S. Fish and Wildlife Service (USFWS), 99, 106, 314 U.S. Forest Service (USFS), 314, 317 U.S. Geological Survey (USGS), 191, 233, 263 Unreliable science, 23–24 Unsustainability, 10–11 Upwellings in marine life zones, 62 Urban areas compact, and disperse, 281 ecocity Curitiba, Brazil, 283–85 effect of transportation on environment of, 281–83 global, 276f growth of, 276–77 increasing sustainability and quality of life in, 283–85 megacities, 276f Mexico City, Mexico, 280 poverty in, 277, 280 in United States, 277f Urban growth, 276–77 smart growth, 283, 284f Urban heat island, 280 Urbanization, 81, 276–85 advantages of, 278 disadvantages of, 278–80 effects of transportation on, 281–83 Mexico City as case study, 280 poverty and, 277, 280 sprawl associated with, 277–78 sustainability and livability accompanying, 283–85 in United States, 277 Urban sprawl, 277, 278f Van Doren, Mark, 1 Van Leeuwenhock, Antoine, 65 Vegetation flooding caused by removal of, 169 lack of, in urban areas, 279 Very small (ultrafine) particles as air pollutant, 252 Viral diseases, 229–30 Virtual water, 159b Visual learners, 3 Vitamins, human nutrition and, 132–33 Volatile organic compounds (VOCs), 180 as air pollutant, 246t, 248 Volcanic eruptions, 53 Voluntary simplicity, 324 Vulnerable species. See Threatened (vulnerable) species Wackernagel, Mathis, 12, 279f Ward, Barbara, 5 Waste electronic, 286 energy, 206–7 hazardous, 285, 294–97 integrated management of, 287f marketplace solutions for waste and, 307–8
radioactive, 201 taxes on, 306–7 of water resources, 165–68 Waste management, 287 hazardous, 294–97 integrated, 287f solid, 287–93 Waste reduction, 287 Waste-to-energy incinerator, 291, 292f Wastewater treatment plants, 168, 182–83 Water. See also Water pollution; Water resources drinking (see Drinking water) fresh (see Freshwater) hydrologic cycle, 40–42 producing electricity from flowing/falling, 214–15 virtual, 159b Water (hydrologic) cycle, 40, 41f, 42 effects of human activities on, 42 Water-filled pools in nuclear reactors, 200 Water footprints, 159b Water hot spots, U.S., 158f Waterlogging of soils, 140f Water pollutants, 171, 172t degradable, slowly-degradable, and nondegradable wastes as, 176 in groundwater, 175–76 harmful effects of, on human health, 171 major categories of, 171t Water pollution, 139, 171–84 in groundwater and drinking water sources, 175–77 individual role in reducing, 184f in oceans, 178–80 point and nonpoint sources of, 171 pollutants (see Water pollutants) reducing and preventing, 180–84 sources and causes of, 171 in streams and lakes, 172–75 sustainable reduction and prevention of, 183–84 Water Quality Act of 1987, 181 Water resources, 155–71 Aral Sea disaster, 164–65 conflict over, in Middle East, 160–61f dams and reservoirs to capture, 162, 163f desalination of seawater, 165 drinking water (see Drinking water) food production and degradation of, 139f, 142–43 freshwater, 156–58 groundwater, 156, 157f, 161–62 increasing supplies of, 161–65 polluted (see Water pollution) problems with, in urban areas, 279 reducing floods, 169–71 reducing waste of, 165–68 shortages of, 158–59 surface, 156, 157 sustainable use of, 165–68 transfer systems for, 164 in U.S., 157–58 water footprints and virtual water, 159b Watershed, 63, 64f, 156 protecting, 128 Water table, 156 Water transfer systems, 164f Water vapor, 246 Wealth gap, 309. See also Poverty Weather, 244–46 climate change and extremes of, 264
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
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Weathering (soil), 136 West Nile virus, 230 Wet deposition, 249 Wetland(s) coastal, 61 flooding caused by destruction of, 171 inland, 63–64 seasonal, 63 Wetland–based sewage treatment systems, 183 Whale Conservation and Protection Act of 1976, U.S., 126 Wilderness, 121 in U.S., 121, 315 Wilderness Society, U.S., 325 Wildlife effects of climate change on, 103, 104 effects of habitat destruction, degradation, and fragmentation on, 98–99, 100f effects of ozone depletion on, 271f effects of pesticides on, 103f extinction of 93–98 (see Extinction of species) introduced species as threat to, 99–102 killing, capturing and selling as threat to, 104 pesticide threat to, 145
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protecting, 105–8 reasons for preserving, 97–98 reintroduction of gray wolf, 118, 119b Wildlife refuges, 106 Wilson, Diane, role in toxic chemicals cleanup, 318b Wilson, Edward O., 94, 96, 108, 110 as biodiversity champion, 51b priorities for protecting biodiversity by, 128–29 Wind climate and prevailing, 245 generation of electricity with, 215–16 Windbreaks, 149f Wind energy, 30, 188 Wind farms, 216f Wind turbines, 216f Wolf, reintroduced populations of gray, 118, 119b Women fertility rates among, 80 population regulation through empowerment of, 81–82, 87 Wood as energy source, 217
World Commission on Water, 173 World Conservation Union. See International Union for Conservation of Nature (IUCN) World Environmental Organization (WEO), proposed, 321 World Health Organization (WHO), 171, 228, 229, 232, 247, 253, 320 World Meteorological Organization, 260, 264 World Resources Institute (WRI), 139, 165 World Water Vision Report, 184 World Wildlife Fund, 318 Wright, Frank Lloyd, 4 Xerox Corporation, 308 Yellowstone National Park, reintroduction of gray wolf into, 118, 119b Yucca Mountain nuclear waste storage facility, 201 Yunnas, Muhammad, 309 Zebra mussel, 128 Zone of saturation, 156 Zoos, protecting endangered species in, 107
INDEX Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
