Environment the science behind the stories [5. ed., global ed] 9780321897428, 1292063319, 9781292063317, 2612622632, 3783803853, 0321897420, 9780133540147, 0133540146, 9780321927576, 0321927575

Table of contents :
Cover......Page 1
Title......Page 2
Copyright......Page 3
Contents......Page 6
Part One Foundations of Environmental Science......Page 20
1 Science and Sustainability: An Introduction to Environmental Science ......Page 21
Our Island, Earth......Page 22
The Nature of Environmental Science......Page 24
The Science Behind the Story: What Are the Lessons of Easter Island? ......Page 25
The Nature of Science......Page 28
Sustainability and Our Future......Page 33
2 Earth’s Physical Systems: Matter, Energy, and Geology......Page 40
CENTRAL CASE STUDY The Tohoku Earthquake: Has It Shaken the World’s Trust in Nuclear Power?......Page 41
Matter, Chemistry, and the Environment......Page 42
The Science Behind the Story: Tracking Fukushima’s Nuclear Legacy......Page 45
Energy: An Introduction......Page 48
Geology: The Physical Basis for Environmental Science ......Page 52
The Science Behind the Story: Have We Brought On a New Geologic Epoch? ......Page 57
Geologic and Natural Hazards......Page 58
3 Evolution, Biodiversity, and Population Ecology......Page 66
CENTRAL CASE STUDY Saving Hawaii’s Native Forest Birds......Page 67
Evolution: The Source of Earth’s Biodiversity......Page 68
The Science Behind the Story: Hawaii: Species Factory and Lab of Evolution......Page 75
Levels of Ecological Organization......Page 79
Population Ecology......Page 80
The Science Behind the Story: Monitoring Bird Populations at Hakalau Forest......Page 83
Conserving Biodiversity......Page 88
4 Species Interactions and Community Ecology......Page 93
CENTRAL CASE STUDY Black and White, and Spread All Over: Zebra Mussels Invade the Great Lakes ......Page 94
Species Interactions......Page 95
Ecological Communities......Page 99
The Science Behind the Story: Determining Zebra Mussels’ Impacts on Fish Communities ......Page 105
The Science Behind the Story: Chronicling Ecological Recovery at Mount St. Helens ......Page 109
Earth’s Biomes......Page 112
5 Environmental Systems and Ecosystem Ecology......Page 123
CENTRAL CASE STUDY The Vanishing Oysters of the Chesapeake Bay......Page 124
Earth’s environmental systems......Page 125
Ecosystems......Page 129
Biogeochemical Cycles......Page 136
The Science Behind the Story: “Turning the Tide” for Native Oysters in Chesapeake Bay ......Page 137
The Science Behind the Story: FACE-ing a High-CO2 Future ......Page 143
6 Ethics, Economics, and Sustainable Development......Page 151
CENTRAL CASE STUDY Costa Rica Values Its Ecosystem Services ......Page 152
Culture, Worldview, and the Environment......Page 153
Environmental Ethics......Page 154
Economics and the Environment......Page 160
The Science Behind the Story: Do Payments Help Preserve Forest?......Page 163
The Science Behind the Story: Ethics in Economics: Discounting and Global Climate Change......Page 167
Sustainable Development......Page 175
7 Environmental Policy: Making Decisions and Solving Problems......Page 180
CENTRAL CASE STUDY Hydrofracking the Marcellus Shale......Page 181
Environmental Policy: An Overview......Page 183
The Science Behind the Story: Does Fracking Contaminate Drinking Water?......Page 185
U.S. Environmental Law and Policy......Page 188
International Environmental Policy......Page 197
Approaches to Environmental Policy......Page 199
Part Two Environmental Issues and the Search for Solutions......Page 206
8 Human Population......Page 207
CENTRAL CASE STUDY China’s One-Child Policy......Page 208
Our World at Seven Billion......Page 209
The Science Behind the Story: Mapping Our Population’s Environmental Impact......Page 213
Demography......Page 215
Population and Society ......Page 221
The Science Behind the Story: Did Soap Operas Reduce Fertility in Brazil? ......Page 223
9 Soil and Agriculture......Page 233
CENTRAL CASE STUDY Iowa’s Farmers Practice No-Till Agriculture ......Page 234
Soil: The Foundation for Sustainable Agriculture......Page 235
Soil as a System......Page 237
Conserving Soil......Page 241
The Science Behind the Story: Can No-Till Farming Help Us Fight Climate Change? ......Page 249
Watering and Fertilizing Crops ......Page 251
The Science Behind the Story: Restoring the Malpai Borderlands......Page 253
Agricultural Policy......Page 256
10 Agriculture, Biotechnology, and the Future of Food ......Page 262
CENTRAL CASE STUDY Transgenic Maize in Southern Mexico? ......Page 263
The Race to Feed the World......Page 264
Raising Animals for Food......Page 268
Preserving Crop Diversity......Page 271
Conserving Pollinators,Controlling Pests......Page 273
Organic Agriculture......Page 276
The Science Behind the Story: How Productive Is Organic Farming? ......Page 277
Genetically Modified Food......Page 280
The Science Behind the Story: Transgenic Contamination of Native Maize?......Page 285
Sustainable Food Production......Page 287
11 Biodiversity and Conservation Biology ......Page 293
CENTRAL CASE STUDY Will We Slice through the Serengeti?......Page 294
Our Planet of Life......Page 295
Extinction and Biodiversity Loss ......Page 300
The Science Behind the Story: Wildlife Declines in African Reserves ......Page 305
Benefits of Biodiversity......Page 309
Conservation Biology: The Search for Solutions......Page 313
The Science Behind the Story: Using Forensics to Uncover Illegal Whaling ......Page 319
12 Forests, Forest Management, and Protected Areas......Page 325
CENTRAL CASE STUDY Certified Sustainable Paper in Your Textbook ......Page 326
Forest Ecosystems and Forest Resources......Page 327
Forest Loss......Page 330
Forest Management......Page 333
Parks and Protected Areas......Page 342
The Science Behind the Story: Fighting over Fire and Forests ......Page 343
The Science Behind the Story: Forest Fragmentation in the Amazon ......Page 349
13 The Urban Environment: Creating Sustainable Cities......Page 354
CENTRAL CASE STUDY Managing Growth in Portland, Oregon ......Page 355
Our Urbanizing World......Page 356
Sprawl......Page 358
Creating Livable Cities......Page 361
Urban Sustainability......Page 369
The Science Behind the Story: Baltimore and Phoenix Showcase Urban Ecology ......Page 371
14 Environmental Health and Toxicology ......Page 377
CENTRAL CASE STUDY Poison in the Bottle: Is Bisphenol A Safe?......Page 378
Environmental Health......Page 379
The Science Behind the Story: Testing the Safety of Bisphenol A ......Page 381
Toxic Substances and Their Effects on Organisms......Page 386
Toxic Substances and Their Effects on Ecosystems......Page 391
Studying Effects of Hazards ......Page 393
The Science Behind the Story: Pesticides and Child Development in Mexico’s Yaqui Valley ......Page 397
Risk Assessment and Risk Management......Page 399
Philosophical and Policy Approaches ......Page 401
15 Freshwater Systems and Resources ......Page 407
CENTRAL CASE STUDY Starving the Louisiana Coast of Sediment......Page 408
Freshwater Systems......Page 410
Human Activities Affect Waterways......Page 415
The Science Behind the Story: Is It Better in a Bottle? ......Page 419
Solutions to Depletion of Fresh Water......Page 424
Freshwater Pollution and Its Control ......Page 427
The Science Behind the Story: Hypoxia and the Gulf of Mexico’s “Dead Zone” ......Page 429
16 Marine and Coastal Systems and Resources......Page 438
CENTRAL CASE STUDY Collapse of the Cod Fisheries......Page 439
The Oceans......Page 440
Marine and Coastal Ecosystems......Page 445
The Science Behind the Story: Will Climate Change Rob Us of Coral Reefs?......Page 447
Marine Pollution......Page 451
The Science Behind the Story: Predicting the Oceans’ “Garbage Patches”......Page 453
Emptying the Oceans......Page 456
Marine Conservation......Page 462
17 Atmospheric Science, Air Quality, and Pollution Control......Page 467
CENTRAL CASE STUDY Clearing the Air in L.A. and Mexico City......Page 468
The Atmosphere......Page 469
Outdoor Air Quality......Page 475
The Science Behind the Story: Measuring the Health Impacts of Mexico City’s Air Pollution......Page 485
Ozone Depletion and Recovery......Page 487
The Science Behind the Story: Discovering Ozone Depletion and the Substances Behind It......Page 489
Addressing Acid Deposition......Page 492
Indoor Air Quality......Page 494
18 Global Climate Change......Page 501
CENTRAL CASE STUDY Rising Seas May Flood the Maldives ......Page 502
Our Dynamic Climate......Page 503
Studying Climate Change......Page 507
The Science Behind the Story: Reading History in the World’s Longest Ice Core ......Page 509
Current and Future Trends and Impacts......Page 511
The Science Behind the Story: How Do Climate Models Work? ......Page 513
Responding to Climate Change......Page 526
19 Fossil Fuels, Their Impacts, and Energy Conservation ......Page 537
CENTRAL CASE STUDY Alberta’s Oil Sands and the Keystone XL Pipeline......Page 538
Sources of Energy......Page 539
Fossil Fuels and Their Extraction......Page 543
The Science Behind the Story: Locating Fossil Fuel Deposits Underground ......Page 549
Addressing Impacts of Fossil Fuel Use......Page 555
The Science Behind the Story: Discovering Impacts of the Gulf Oil Spill ......Page 559
Energy Efficiency and Conservation......Page 565
20 Conventional Energy Alternatives......Page 571
CENTRAL CASE STUDY Sweden’s Search for Alternative Energy......Page 572
Alternatives to Fossil Fuels......Page 573
Nuclear Power......Page 574
The Science Behind the Story: Health Impacts of Chernobyl and Fukushima ......Page 581
Bioenergy......Page 585
The Science Behind the Story: Assessing EROI Values of Energy Sources ......Page 591
Hydroelectric Power ......Page 593
21 New Renewable Energy Alternatives ......Page 599
CENTRAL CASE STUDY Germany Goes Solar......Page 600
“New” Renewable Energy Sources......Page 601
The Science Behind the Story: Comparing Energy Sources ......Page 605
Solar Energy......Page 607
The Science Behind the Story: What Are the Impacts of Solar and Wind Development?......Page 611
Wind Power......Page 613
Geothermal Energy......Page 617
Ocean Energy Sources......Page 619
Hydrogen......Page 621
22 Managing Our Waste ......Page 627
CENTRAL CASE STUDY Transforming New York’s Fresh Kills Landfill ......Page 628
Approaches to Waste Management ......Page 629
Municipal Solid Waste......Page 630
The Science Behind the Story: Tracking Trash ......Page 639
Industrial Solid Waste......Page 641
Hazardous Waste......Page 643
The Science Behind the Story: Testing the Toxicity of “E-Waste” ......Page 647
23 Minerals and Mining......Page 652
CENTRAL CASE STUDY Mining for . . . Cell Phones? ......Page 653
Earth’s Mineral Resources......Page 654
Mining Methods and Their Impacts ......Page 658
The Science Behind the Story: Mountaintop Removal Mining: Assessing the Environmental Impacts ......Page 663
Toward Sustainable Mineral Use......Page 665
24 Sustainable Solutions......Page 672
CENTRAL CASE STUDY De Anza College Strives for a Sustainable Campus ......Page 673
Sustainability on Campus......Page 674
Strategies for Sustainability......Page 684
Precious Time......Page 689
Appendix A Answers to Data Analysis Questions......Page 702
Appendix B How to Interpret Graphs......Page 706
Appendix C Metric System......Page 710
Appendix D Periodic Table of the Elements ......Page 712
Appendix E Geologic Time Scale......Page 714
Glossary......Page 716
Selected Sources and References for Further Reading ......Page 740
Credits ......Page 756
A......Page 760
B......Page 761
C......Page 762
D......Page 764
E......Page 765
F......Page 767
G......Page 768
H......Page 769
K......Page 770
M......Page 771
N......Page 772
O......Page 773
P......Page 774
R......Page 776
S......Page 777
T......Page 778
U......Page 779
W......Page 780
Z......Page 781

Citation preview

Environment

The Science Behind the Stories

For these Global Editions, the editorial team at Pearson has collaborated with educators across the world to address a wide range of subjects and requirements, equipping students with the best possible learning tools. This Global Edition preserves the cutting-edge approach and pedagogy of the original, but also features alterations, customization, and adaptation from the North American version.

Global edition

Global edition

Environment

Global edition

The Science Behind the Stories FIFTH edition

Jay Withgott • Matthew Laposata

FIFTH edition

Withgott • Laposata

This is a special edition of an established title widely used by colleges and universities throughout the world. Pearson published this exclusive edition for the benefit of students outside the United States and Canada. If you purchased this book within the United States or Canada you should be aware that it has been imported without the approval of the Publisher or Author. Pearson Global Edition

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Environment

The Science Behind the Stories 5th Edition Global Edition

Jay Withgott Matthew Laposata

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Editor-in-Chief: Beth Wilbur Executive Director of Development: Deborah Gale Acquisitions Editor: Alison Rodal Project/Development Editor: Anna Amato Editorial Assistant: Libby Reiser Associate Media Producer: Daniel Ross Marketing Manager: Amee Mosley Managing Editor: Michael Early Project Manager: Shannon Tozier Production Management: Kelly Keeler, Cenveo Publisher Services Compositor: Cenveo Publisher Services Illustrators: Imagineeringart.com Inc. Design Manager: Derek Bacchus Interior Designer: Tandem Creative, Inc.

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Cover Photo Credit: Hari Krishnan/123rf Credits and acknowledgments for materials borrowed from other sources and reproduced, with permission, in this textbook appear on the appropriate page within the text or on page CR-1. Pearson Education Limited Edinburgh Gate Harlow Essex CM20 2JE England and Associated Companies throughout the world Visit us on the World Wide Web at: www.pearsonglobaleditions.com © Pearson Education Limited 2015 The rights of Jay Withgott and Matthew Laposata to be identified as the authors of this work have been asserted by them in accordance with the Copyright, Designs and Patents Act 1988. Authorized adaptation from the United States edition, entitled Environment: The Science Behind the Stories, 5th Edition, ISBN 9780-321-89742-8, by Jay Withgott and Matthew Laposata, published by Pearson Education © 2015. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without either the prior written permission of the publisher or a license permitting restricted copying in the United Kingdom issued by the Copyright Licensing Agency Ltd, Saffron House, 6–10 Kirby Street, London EC1N 8TS. All trademarks used herein are the property of their respective owners. The use of any trademark in this text does not vest in the author or publisher any trademark ownership rights in such trademarks, nor does the use of such trademarks imply any affiliation with or endorsement of this book by such owners. ISBN 10: 1-292-06331-9 ISBN 13: 9781-292-06331-7 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Typeset by Cenveo Publisher Services, in Times LT Std/10 pt. Printed by Ashford Colour Press Ltd, Gosport

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About the Authors Jay Withgott has authored Environment: The Science Behind the Stories as well as its brief version, Essential Environment, since their inception. In dedicating himself to these books, he works to keep abreast of a diverse and rapidly changing field and continually seeks to develop new and better ways to help today’s students learn environmental science. As a researcher, Jay has published scientific papers in ecology, evolution, animal behavior, and conservation biology in journals ranging from Evolution to Proceedings of the National Academy of Sciences. As an instructor, he has taught university lab courses in ecology and other disciplines. As a science writer, he has authored articles for numerous journals and magazines including Science, New Scientist, BioScience, Smithsonian, and Natural History. By combining his scientific training with prior experience as a newspaper reporter and editor, he strives to make science accessible and engaging for general audiences. Jay holds degrees from Yale University, the University of Arkansas, and the University of Arizona. Jay lives with his wife, biologist Susan Masta, in Portland, Oregon.

Matthew Laposata is a professor of environmental science at Kennesaw State University (KSU). He holds a bachelor’s degree in biology education from Indiana University of Pennsylvania, a master’s degree in biology from Bowling Green State University, and a doctorate in ecology from The Pennsylvania State University. Matt is the coordinator of KSU’s two-semester general education science sequence titled Science, Society, and the Environment, which enrolls roughly 6000 students per year. He focuses exclusively on introductory environmental science courses and has enjoyed teaching and interacting with thousands of nonscience majors during his career. He is an active scholar in environmental science education and has received grants from state, federal, and private sources to develop and evaluate innovative curricular materials. His scholarly work has received numerous awards, including the Georgia Board of Regents’ highest award for the Scholarship of Teaching and Learning. Matt resides in suburban Atlanta with his wife, Lisa, and children, Lauren, Cameron, and Saffron.

ABOUT OUR SUSTAINABILITY INITIATIVES This book is carefully crafted to minimize environmental impact. The materials used to manufacture this book originated from sources committed to responsible forestry practices. The paper is Forest Stewardship Council™ (FSC®) certified. The printing, binding, cover, and paper come from facilities that minimize waste, energy consumption, and the use of harmful chemicals. Pearson closes the loop by recycling every out-of-date text returned to our warehouse. We pulp the books, and the pulp is used to produce items such as paper coffee cups and shopping bags. In addition, Pearson has become the first climate-neutral educational publishing company. The future holds great promise for reducing our impact on Earth’s environment, and Pearson is proud to be leading the way. We strive to publish the best books with the most up-to-date and accurate content, and to do so in ways that minimize our environmental impact.

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Brief Contents Part ONE Foundations of Environmental Science 19

1 2 3 4 5 6 7



Science and Sustainability: An Introduction to Environmental Science 20 Earth’s Physical Systems: Matter, Energy, and Geology 39 Evolution, Biodiversity, and Population Ecology 65 Species Interactions and Community Ecology 92 Environmental Systems and Ecosystem Ecology 122 Ethics, Economics, and Sustainable Development 150 Environmental Policy: Making Decisions and Solving Problems 179

PART TWO Environmental Issues and the Search for Solutions 205

8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

4



Human Population 206 Soil and Agriculture 232 Agriculture, Biotechnology, and the Future of Food 261 Biodiversity and Conservation Biology 292 Forests, Forest Management, and Protected Areas 324 The Urban Environment: Creating Sustainable Cities 353 Environmental Health and Toxicology 376 Freshwater Systems and Resources 406 Marine and Coastal Systems and Resources 437 Atmospheric Science, Air Quality, and Pollution Control 466 Global Climate Change 500 Fossil Fuels, Their Impacts, and Energy Conservation 536 Conventional Energy Alternatives 570 New Renewable Energy Alternatives 598 Managing Our Waste 626 Minerals and Mining 651 Sustainable Solutions 671

Appendix A: Answers to Data Analysis Questions A-1 Appendix B: How to Interpret Graphs B-1 Appendix C: Metric System C-1 Appendix D: Periodic Table of the Elements D-1 Appendix E: Geologic Time Scale E-1 Glossary G-1 Selected Sources and References for Further Reading R-1 Credits CR-1 Index I-1

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Contents Geology: The Physical Basis for Environmental Science51

P art O ne

The Science Behind the Story: Have We Brought On a New Geologic Epoch? 56 Geologic and Natural Hazards57

3

 volution, Biodiversity, E and Population Ecology65 CENTRAL CASE STUDY Saving Hawaii’s Native Forest Birds 

Foundations of Environmental Science

Evolution: The Source of Earth’s Biodiversity

1

S cience and Sustainability: An Introduction to Environmental Science20

Our Island, Earth21 The Nature of Environmental Science  23 The Science Behind the Story: What Are the Lessons of Easter Island? The Nature of Science  Sustainability and Our Future 

2

24 27 32

 arth’s Physical Systems: E Matter, Energy, and Geology39

67

The Science Behind the Story: Hawaii: Species Factory and Lab of Evolution 74 Levels of Ecological Organization78 Population Ecology 79 The Science Behind the Story: Monitoring Bird Populations at Hakalau Forest Conserving Biodiversity

4

82 87

S pecies Interactions and Community Ecology92 CENTRAL CASE STUDY Black and White, and Spread All Over: Zebra Mussels Invade the Great Lakes

93

Species Interactions 94 Ecological Communities98

CENTRAL CASE STUDY The Tohoku Earthquake: Has It Shaken the World’s Trust in Nuclear Power? 

66

40

The Science Behind the Story: Tracking Fukushima’s Nuclear Legacy 44 Energy: An Introduction47

104

The Science Behind the Story: Chronicling Ecological Recovery at Mount St. Helens 108 Earth’s Biomes111

CONTENTS

Matter, Chemistry, and the Environment41

The Science Behind the Story: Determining Zebra Mussels’ Impacts on Fish Communities

5

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5

 nvironmental Systems E and Ecosystem Ecology122 CENTRAL CASE STUDY The Vanishing Oysters of the Chesapeake Bay

International Environmental Policy196 Approaches to Environmental Policy198

P art T W O 123

Earth’s Environmental Systems 124 Ecosystems128 Biogeochemical Cycles135

6

The Science Behind the Story: “Turning the Tide” for Native Oysters in Chesapeake Bay

136

The Science Behind the Story: FACE-ing a High-CO2 Future

142

 thics, Economics, and E Sustainable Development150

Environmental Issues and the Search for Solutions

8

CENTRAL CASE STUDY

CENTRAL CASE STUDY Costa Rica Values Its Ecosystem Services

China’s One-Child Policy

The Science Behind the Story: Ethics in Economics: Discounting and Global Climate Change Sustainable Development

207

151

152 Culture, Worldview, and the Environment Environmental Ethics153 Economics and the Environment159 The Science Behind the Story: Do Payments Help Preserve Forest?

Human Population206

162

166 174

Our World at Seven Billion208 The Science Behind the Story: Mapping 212 Our Population’s Environmental Impact Demography214 Population and Society220 The Science Behind the Story: Did Soap Operas Reduce Fertility in Brazil?

9

222

Soil and Agriculture232 CENTRAL CASE STUDY

7

 nvironmental Policy: E Making Decisions and Solving Problems179

233

180

Soil: The Foundation for Sustainable Agriculture234 Soil as a System236 Conserving Soil240

Environmental Policy: An Overview182

The Science Behind the Story: Can No-Till Farming Help Us Fight Climate Change? 248 Watering and Fertilizing Crops250

The Science Behind the Story: Does Fracking Contaminate Drinking Water? 184 U.S. Environmental Law and Policy187

The Science Behind the Story: Restoring the Malpai Borderlands 252 Agricultural Policy255

CENTRAL CASE STUDY Hydrofracking the Marcellus Shale

6

Iowa’s Farmers Practice No-Till Agriculture

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10

 griculture, A Biotechnology, and the Future of Food261 CENTRAL CASE STUDY Transgenic Maize in Southern Mexico?

262

The Race to Feed the World263 Raising Animals for Food 267 Preserving Crop Diversity270 Conserving Pollinators, Controlling Pests272 Organic Agriculture275

Forest Ecosystems and Forest Resources326 Forest Loss329 Forest Management332 Parks and Protected Areas341 The Science Behind the Story: Fighting over Fire and Forests

342

The Science Behind the Story: Forest Fragmentation in the Amazon

348

13

The Science Behind the Story: 276 How Productive Is Organic Farming? Genetically Modified Food279 The Science Behind the Story: Transgenic Contamination of Native Maize? 284 Sustainable Food Production286

11

 iodiversity and B Conservation Biology292 CENTRAL CASE STUDY Will We Slice through the Serengeti?

The Science Behind the Story: Wildlife Declines in African Reserves 304 Benefits of Biodiversity308 Conservation Biology: The Search for Solutions312

12

318

F orests, Forest Management, and Protected Areas324

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Managing Growth in Portland, Oregon

354

Our Urbanizing World355 Sprawl357 Creating Livable Cities360 Urban Sustainability368 The Science Behind the Story: Baltimore and Phoenix Showcase Urban Ecology

370

325

14

 nvironmental Health E and Toxicology376 CENTRAL CASE STUDY Poison in the Bottle: Is Bisphenol A Safe?

377

Environmental Health378 The Science Behind the Story: Testing the Safety of Bisphenol A 380 Toxic Substances and Their 385 Effects on Organisms Toxic Substances and Their Effects on Ecosystems390 Studying Effects of Hazards392 The Science Behind the Story: Pesticides and Child Development in Mexico’s Yaqui Valley 396 Risk Assessment and Risk Management398 Philosophical and Policy Approaches400

CONTENTS

CENTRAL CASE STUDY Certified Sustainable Paper in Your Textbook

CENTRAL CASE STUDY

293

Our Planet of Life294 Extinction and Biodiversity Loss299

The Science Behind the Story: Using Forensics to Uncover Illegal Whaling

 he Urban Environment: T Creating Sustainable Cities353

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15

F reshwater Systems and Resources406 CENTRAL CASE STUDY Starving the Louisiana Coast of Sediment

407

Freshwater Systems409 Human Activities Affect Waterways 414

Ozone Depletion and Recovery486 The Science Behind the Story: Discovering Ozone Depletion and the Substances Behind It 488 Addressing Acid Deposition491 Indoor Air Quality493

18

CENTRAL CASE STUDY

The Science Behind the Story: Is It Better in a Bottle? 418 Solutions to Depletion of Fresh Water423 Freshwater Pollution and Its Control 426 The Science Behind the Story: Hypoxia and the Gulf of Mexico’s “Dead Zone”

16

428

 arine and Coastal M Systems and Resources437 CENTRAL CASE STUDY Collapse of the Cod Fisheries

Rising Seas May Flood the Maldives

The Science Behind the Story: Reading 508 History in the World’s Longest Ice Core Current and Future Trends and Impacts510 The Science Behind the Story: 512 How Do Climate Models Work? Responding to Climate Change525

438

439 The Oceans Marine and Coastal Ecosystems444 The Science Behind the Story: Will Climate Change Rob Us of Coral Reefs? 446 Marine Pollution450 The Science Behind the Story: Predicting the Oceans’ “Garbage Patches” 452 Emptying the Oceans455 Marine Conservation461

 tmospheric Science, A Air Quality, and Pollution Control466 CENTRAL CASE STUDY Clearing the Air in L.A. and Mexico City

467

The Atmosphere468 Outdoor Air Quality474

8

The Science Behind the Story: Measuring the Health Impacts of Mexico City’s Air Pollution

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501

Our Dynamic Climate502 Studying Climate Change506

19

17

Global Climate Change500

F ossil Fuels, Their Impacts, and Energy Conservation536 CENTRAL CASE STUDY Alberta’s Oil Sands and the Keystone XL Pipeline

537

Sources of Energy538 Fossil Fuels and Their Extraction542 The Science Behind the Story: Locating 548 Fossil Fuel Deposits Underground Addressing Impacts of Fossil Fuel Use554 The Science Behind the Story: Discovering Impacts of the Gulf Oil Spill 558 Energy Efficiency and Conservation564

20

 onventional Energy C Alternatives570 CENTRAL CASE STUDY Sweden’s Search for Alternative Energy

571

484

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Alternatives to Fossil Fuels572 Nuclear Power573

23

Minerals and Mining651 CENTRAL CASE STUDY

The Science Behind the Story: Health Impacts of Chernobyl and Fukushima 580 Bioenergy584 The Science Behind the Story: 590 Assessing EROI Values of Energy Sources Hydroelectric Power592

21

 ew Renewable Energy N Alternatives598 CENTRAL CASE STUDY Germany Goes Solar

599

Mining for . . . Cell Phones?

652

Earth’s Mineral Resources653 Mining Methods and Their Impacts657 The Science Behind the Story: Mountaintop Removal Mining: Assessing 662 the Environmental Impacts Toward Sustainable Mineral Use664

24

Sustainable Solutions671 CENTRAL CASE STUDY

“New” Renewable Energy Sources

600

The Science Behind the Story: 604 Comparing Energy Sources Solar Energy606 The Science Behind the Story: What Are the Impacts of Solar 610 and Wind Development? Wind Power612 Geothermal Energy616 Ocean Energy Sources618 Hydrogen620

De Anza College Strives for a Sustainable Campus

672

Sustainability on Campus673 Strategies for Sustainability683 Precious Time688

Appendix A Answers to Data Analysis Questions

A-1

Appendix B

22

How to Interpret Graphs

Managing Our Waste626 Transforming New York’s Fresh Kills Landfill

Appendix C Metric System

CENTRAL CASE STUDY

B-1 C-1

Appendix D 627

Periodic Table of the Elements

D-1

Appendix E Approaches to Waste Management628 Municipal Solid Waste629 The Science Behind the Story: 638 Tracking Trash Industrial Solid Waste640 Hazardous Waste642 646

E-1

Glossary

G-1

Selected Sources and References for Further Reading

R-1

Credits Index

CR-1 I-1

CONTENTS

The Science Behind the Story: Testing the Toxicity of “E-Waste”

Geologic Time Scale

9

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Preface Dear Student,

Dear Instructor,

You are coming of age at a unique and momentous time in history. Within your lifetime, our global society must chart a promising course for a sustainable future. The stakes could not be higher. Today we live long lives enriched with astonishing technologies, in societies more free, just, and equal than ever before. We enjoy wealth on a scale our ancestors could hardly have dreamed of. Yet we have purchased these wonderful things at a price. By exploiting Earth’s resources and ecological services, we are depleting our planet’s bank account and running up its credit card. We are altering our planet’s land, air, water, nutrient cycles, biodiversity, and climate at dizzying speeds. More than ever before, the future of our society rests with how we treat the world around us. Your future is being shaped by the phenomena you will learn about in your environmental science course. Environmental science gives us a big-picture understanding of the world and our place within it. Environmental science also offers hope and solutions, revealing ways to address the problems we create. Environmental science is not simply some subject you learn in college. Rather, it provides you basic literacy in the foremost issues of the 21st century, and it relates to everything around you over your entire lifetime. We have written this book because today’s students will shape tomorrow’s world. At this unique moment in history, students of your generation are key to achieving a sustainable future for our civilization. The many environmental challenges that face us can seem overwhelming, but you should feel encouraged and motivated. Remember that each dilemma is also an opportunity. For every problem that human carelessness has created, human ingenuity can devise a solution. Now is the time for innovation, creativity, and the fresh perspectives that a new generation can offer. Your own ideas and energy will make a difference.

You perform one of our society’s most vital jobs by educating today’s students—the citizens and leaders of tomorrow—on the fundamentals of the world around them, the nature of science, and the most central issues of our time. We have written this book to assist you in this endeavor because we feel that the crucial role of environmental science in today’s world makes it imperative to engage, educate, and inspire a broad audience of students. In Environment: The Science Behind the Stories, we strive to implement a diversity of modern teaching approaches and to show how science can inform efforts to bring about a sustainable society. We aim to encourage critical thinking and to maintain a balanced approach as we flesh out the vibrant social debate that accompanies environmental issues. As we assess the challenges facing our civilization and our planet, we focus on providing forward-looking solutions, for we truly feel there are many reasons for optimism. In crafting the fifth edition of this text, we have incorporated the most current information from this fast-moving field and have streamlined our presentation to promote learning. We have examined every line with care to make sure all content is accurate, clear, and up-to-date. Moreover, we have introduced a number of major changes that are new to this edition.

–Jay Withgott and Matthew Laposata

New to This Edition With the fifth edition we welcome Dr. Matthew Laposata as an author. Professor of environmental science at Kennesaw State University in Georgia, Matt teaches and coordinates his university’s environmental science courses while actively engaging in outside projects to promote environmental science education. Matt’s ideas, energy, and commitment to outstanding teaching have already enlivened and strengthened this book as well as its brief version, Essential Environment. Please welcome him to our author team! This fifth edition includes an array of revisions that together enhance our content and presentation while strengthening our commitment to teach science in an engaging and accessible way.

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CENTR AL C A S E S T UDY

Ten of our 23 Central Case Studies are new to this edition, providing a wealth of fresh stories and new ways to frame issues in environmental science. Students will travel from Pennsylvania to Hawai‘i and from Africa to Japan as they learn how debates over hydraulic fracturing, oil sands extraction, air pollution, and wildlife conservation are affecting people’s lives.

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• Chapter 2: The Tohoku Earthquake: Has it Shaken the World’s Trust in Nuclear Power? • Chapter 3:  Saving Hawaii’s Native Forest Birds • Chapter 5: The Vanishing Oysters of the Chesapeake Bay • Chapter 6:  Costa Rica Values its Ecosystem Services • Chapter 7:  Hydrofracking the Marcellus Shale • Chapter 9:  Iowa’s Farmers Practice No-Till Agriculture • Chapter 11:  Will We Slice through the Serengeti? • Chapter 15:  Starving the Louisiana Coast of Sediment • Chapter 17: Clearing the Air in L.A. and Mexico City • Chapter 19: Alberta’s Oil Sands and the Keystone XL Pipeline

THE SCIENCE BEHIND THE STORY

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new feature highlights questions frequently FAQ This posed by students in introductory environmental science courses. Some FAQs address widely held misconceptions, whereas others fill in common conceptual gaps in student knowledge. This feature addresses not only the questions students ask, but also the questions they sometimes hesitate to ask. In so doing, it shows students they are not alone in having these questions, and it helps to foster an environment of open inquiry in the classroom.

Each chapter now contains questions that help students to actively engage with graphs and other data-driven figures. The questions accompany several figures in each chapter, challenging students to practice quantitative skills of interpretation and analysis. To encourage students to test their understanding as they read, answers are provided in Appendix A. Currency and coverage of topical issues  To live up to our book’s hard-won reputation for currency, we’ve incorporated the most recent data possible throughout, and we’ve enhanced coverage of issues now gaining prominence. As climate change and energy concerns play ever-larger roles in today’s world, our coverage has evolved. This edition highlights how renewable energy is growing, yet also how we continue reaching further for fossil fuels with deep offshore drilling,  Arctic drilling, hydraulic fracturing for oil and shale gas, and extraction of oil sands. These choices make energy returned on investment (EROI) ratios crucially important, especially as climate change gathers force. Climate change connections continue to proliferate among topics throughout our text, and our climate change chapter includes new coverage of climate modeling, geoengineering, research into jet stream effects on extreme weather, impacts of Hurricane Sandy and other events, the latest climate predictions for the United States and the world, efforts toward carbon neutrality, and political responses at all levels. This edition also expands its coverage of a diversity of topics including the valuation of ecosystem services, introduced species and their ecological impacts on islands, prospects for nuclear power and safety after Fukushima, advanced biofuels, hormone-disrupting substances, impacts on coastal wetlands, plastic pollution in the oceans, environmental policy, ocean acidification, sustainable agriculture, green-collar jobs, and the rebound effect in energy conservation. We continue to use sustainability as an organizing theme throughout

P R E FAC E

Fully 18 of our 42 Science Behind the Story features are new to this edition, providing a current and exciting selection of scientific studies to highlight. Students will follow researchers as they help to restore an oyster fishery; monitor animal populations; evaluate energy sources; and assess impacts of smog, aquifer contamination, fallout from Fukushima, and oil from the Deepwater Horizon spill. Selected features are supported by new “Process of Science” exercises online in MasteringEnvironmentalScience that use these examples to help students explore how scientists conduct their work. • Chapter 2:  Tracking Fukushima’s Nuclear Legacy • Chapter 3: Hawaii: Species Factory and Lab of Evolution • Chapter 3: Monitoring Bird Populations at Hakalau Forest • Chapter 4: Chronicling Ecological Recovery at Mount St. Helens • Chapter 5: “Turning the Tide” for Native Oysters in Chesapeake Bay • Chapter 6:  Do Payments Help Preserve Forest? • Chapter 7: Does Fracking Contaminate Drinking Water? • Chapter 8: Did Soap Operas Reduce Fertility in Brazil? • Chapter 9: Can No-Till Farming Help Us Fight Climate Change? • Chapter 11:  Wildlife Declines in African Reserves • Chapter 16: Predicting the Oceans’ “Garbage Patches” • Chapter 17: Measuring the Health Impacts of Mexico City’s Air Pollution • Chapter 18:  How Do Climate Models Work? • Chapter 19: Discovering Impacts of the Gulf Oil Spill

• Chapter 20: Health Impacts of Chernobyl and Fukushima • Chapter 20: Assessing EROI Values of Energy Sources • Chapter 21:  Comparing Energy Sources • Chapter 21: What are the Impacts of Solar and Wind Development?

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the book, and we aid these efforts by moving primary coverage of sustainable development to Chapter 6 and previewing Chapter 24’s campus sustainability coverage in Chapter 1. Enhanced style elements We have updated and improved the look and clarity of our visual presentation throughout the text. A more open layout, more engaging photo treatments, improved maps in the case studies, and redesigned table styles all make the book more inviting and accessible for learning. This edition includes over 30% new photos, graphs, and illustrations, while existing figures have been revised to reflect current data or for better clarity or pedagogy.

Existing Features We have also retained the major features that made the first four editions of our book unique and that are proving so successful in classrooms across North America: An emphasis on science and data analysis  We have maintained and strengthened our commitment to a rigorous presentation of modern scientific research while at the same time making science clear, accessible, and engaging to students. Explaining and illustrating the process of science remains a foundational goal of this endeavor. We also continue to provide an abundance of clearly cited data-rich graphs, with accompanying tools for data analysis. In our text, our figures, and numerous print and online features, we aim to challenge students and to assist them with the vital skills of data analysis and interpretation. An emphasis on solutions  For many students, today’s deluge of environmental dilemmas can lead them to believe that there is no hope or that they cannot personally make a difference in tackling these challenges. We have aimed to counter this impression by highlighting innovative solutions being developed around the world. While being careful not to paint too rosy a picture of the challenges that lie ahead, we demonstrate that there is ample reason for optimism, and we encourage action. Our campus sustainability coverage (Chapters 1 and 24) shows students how their peers are applying principles and lessons from environmental science to forge sustainable solutions on their own campuses. Central Case Studies integrated throughout the text. We integrate each chapter’s Central Case Study into the main text, weaving information and elaboration throughout the chapter. In this way, compelling stories about real people and real places help to teach foundational concepts by giving students a tangible framework with which to incorporate novel ideas. We are gratified that students and instructors using our book have so consistently applauded this approach, and we hope it con-

tinues to bring further success in environmental science education. The Science Behind the Story Because we strive to engage students in the scientific process of testing and discovery, we feature The Science Behind the Story boxes in each chapter. By guiding students through key research efforts, this feature shows not merely what scientists discovered, but how they discovered it. Weighing the Issues These questions aim to help develop the critical-thinking skills students need to navigate multifaceted issues at the juncture of science, policy, and ethics. They serve as stopping points for students to reflect on what they have read, wrestle with complex dilemmas, and engage in spirited classroom discussion. Diverse end-of-chapter features  Reviewing Objectives summarizes each chapter’s main points and relates them to the chapter’s learning objectives, enabling students to confirm that they have understood the most crucial ideas and to review concepts by turning to specified page numbers. Testing Your Comprehension provides concise study questions on main topics, while Seeking Solutions encourages broader creative thinking aimed at finding solutions. “Think It Through” questions place students in a scenario and empower them to make decisions to resolve problems. Calculating Ecological Footprints enables students to quantify the impacts of their own choices and measure how individual impacts scale up to the societal level.

MasteringEnvironmentalScience With this edition we are thrilled to offer expanded opportunities through MasteringEnvironmentalScience, our powerful yet easy-to-use online learning and assessment platform. We have developed new content and activities specifically to support features in the textbook, thus strengthening the connection between these online and print resources. This approach encourages students to practice their science literacy skills in an interactive environment with a diverse set of automatically graded exercises. Students benefit from self-paced activities that feature immediate wrong-answer feedback, while instructors can gauge student performance with informative diagnostics. By enabling assessment of student learning outside the classroom, MasteringEnvironmentalScience helps the instructor to maximize the impact of in-classroom time. As a result, both educators and learners benefit from an integrated text and online solution. New to this edition  Informed by instructor feedback and instructors’ desires for students to leave their environmental science course with a mastery of science literacy skills, the following are additions to MasteringEnvironmentalScience. The first three were created specifically for the fifth edition by our textbook’s co-author Matthew Laposata:

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• Process of Science activities help students navigate the scientific method, guiding them through in-depth explorations of experimental design using Science Behind the Story features from the fifth edition. These activities encourage students to think like a scientist and to practice basic skills in experimental design. • Interpreting Graphs and Data: Data Q activities pair with the new in-text Data Analysis Questions and coach students to further develop skills related to presenting, interpreting, and thinking critically about environmental science data. • “First Impressions” Pre-Quizzes help instructors determine their students’ existing knowledge of environmental issues and core content areas at the outset of the academic term, providing class-specific data that can then be employed for powerful teachable moments throughout the term. Assessment items in the Test Bank connect to each quiz item, so instructors can formally assess student understanding. • More Video Field Trips have been added to the existing library in MasteringEnvironmentalScience. With three new videos you can now kick off your class period with a short visit to a wind farm, a site tackling invasive species, or a sustainable college campus.

Instructor Supplements Instructor Resource Center Instructor Resource Center includes chapter-by-chapter teaching resources in one convenient location. You’ll find Video Field Trips, PowerPoint presentations, Active Lecture questions to facilitate class discussions (for use with or without clickers), test bank that includes hundreds of multiple choice questions plus unique graphing, and scenario-based questions, and an image library that contains all art and tables from the text. All teaching resources are available at www.pearson globaleditions.com/Withgott

Instructor Guide This comprehensive resource available at www.pearsonglobal editions.com/Withgott provides chapter outlines, key terms, and teaching tips for lecture and classroom activities.

Existing features MasteringEnvironmentalScience also retains its popular existing features. These include existing Interpreting Graphs and Data exercises and the interactive GraphIt! program, each of which guides students in exploring how to present and interpret data and how to create graphs; interactive Causes and Consequences exercises, which let students probe the causes behind major issues, their consequences, and possible solutions; and Viewpoints, paired essays authored by invited experts who present divergent points of view on topical questions. Environment: The Science Behind the Stories has grown from our experiences in teaching, research, and writing. We have been guided in our efforts by input from the hundreds of instructors across North America who have served as reviewers and advisors. The participation of so many learned, thoughtful, and committed experts and educators has improved this volume in countless ways. We sincerely hope that our efforts are worthy of the immense importance of our subject matter. We invite you to let us know how well we have achieved our goals and where you feel we have fallen short. Please write to us in care of our editor Alison Rodal ([email protected]) at Pearson Education. We value your feedback and are eager to know how we can serve you better. P R E FAC E

–Jay Withgott and Matthew Laposata

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Acknowledgments

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A textbook is the product of many more minds and hearts than one might guess from the names on the cover. The two of us are exceedingly fortunate to be supported and guided by a tremendous publishing team and by a small army of experts in environmental science who have generously shared their time and expertise. The strengths of this book result from the collective labor and dedication of innumerable people. We would first like to thank our acquisitions editor, Alison Rodal. Alison joined us at the outset of this edition, bringing a fresh perspective to the book along with skills and experience from multiple aspects of publishing. Her insight, alacrity, and efficacy have greatly enhanced the outcome. We—and the instructors and students who use this book—are fortunate to have her at the helm. Project editor Anna Amato was also key to the success of this edition. Anna’s careful and perceptive editing benefited all of us, and her creative involvement in layout and in the art program improved the book in many ways. We also appreciated her skillful management of the endless publishing logistics during the preparation of this edition. It was a pleasure to work with Alison and Anna on this edition, and we appreciate their patience with us and their dedication to top-quality work. We wish to thank our editor-in-chief Beth Wilbur for her strong and steady support of this book through its five editions. We also thank executive director of development Deborah Gale. Sincere gratitude is due to Beth and to Pearson’s upper management for continuing to invest the resources and topnotch personnel that our books are enjoying now and have enjoyed over the past decade. Editorial assistants Rachel Brickner and Libby Reiser provided timely and effective help. We also thank Camille Herrera, who helped launch production of this edition, and Shannon Tozier, who saw it through production. Sally Peyrefitte once again provided meticulous copy editing of our text, and photo researcher Zoe Milgram helped acquire quality photos. Wynne Au Yeung did an exceptionally smooth job with the art program, and Yvo Riezebos designed the brilliant new text interior and the cover. We send a huge thank-you to production editor Kelly Keeler and the rest of the staff at Cenveo® Publisher Services for their fantastic work putting this fifth edition together. In addition, we remain grateful for lasting contributions to the book’s earlier editions by Nora Lally-Graves, Mary Ann Murray, Susan Teahan, Tim Flem, and Dan Kaveney, as well as by Etienne Benson, Russell Chun, Jonathan Frye, April Lynch, Kristy Manning, and many others. Needless to say, Scott Brennan was instrumental. His ideas, words, and voice have reverberated through the editions even as the particulars have evolved many times over. And as much as anyone, our former editor Chalon Bridges deserves credit for making this book what it is. Chalon’s heartfelt commitment to quality educational publishing has long inspired us all, and our efforts continue to owe a great deal to her astute guidance and vision.

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As we move deeper into the electronic age, MasteringEnvironmentalScience plays an ever-larger role in what we do. As we worked to expand our online offerings with this edition, we thank Kayla Rihani, Julie Stoughton, Steven Frankel, Karen Sheh, Tania Mlawer, Juliana Golden, Lee Ann Doctor, and Daniel Ross for their work on the Mastering website and our media supplements. A special thanks to Eric Flagg for his tremendous Video Field Trips. As always, a select number of top instructors from around North America have teamed up with us to produce the supplementary materials used by so many educators, and we remain deeply grateful for their valuable help. Our thanks go to Danielle DuCharme for updating our Instructor’s Guide, to Todd Tracy for his help with the Test Bank, and to Steven Frankel for revising the PowerPoint lectures and clicker questions. Of course, none of this has any impact on education without the sales and marketing staff to get the book into your hands. Marketing Managers Amee Mosley and Lauren Harp are dedicating their talent and enthusiasm to the book’s promotion and distribution. Moreover, the many sales representatives who help to communicate our vision, deliver our product to instructors, and work with instructors to assure their satisfaction, are absolutely vital. We have been blessed with an amazingly sharp and dedicated sales force, and we deeply appreciate their tireless work and commitment. In the lists of reviewers that follow, we acknowledge the many instructors and outside experts who have helped us to maximize the quality and accuracy of our content and presentation through their chapter reviews, feature reviews, class tests, focus group participation, and other services. If the thoughtfulness and thoroughness of these hundreds of people are any indication, we feel confident that the teaching of environmental science is in excellent hands! Lastly, we each owe personal debts to the people nearest and dearest to us. Jay thanks his parents and his many teachers and mentors over the years for making his own life and education so enriching. He gives loving thanks to his wife, Susan, who has endured this book’s writing and revision over the years with patience and understanding, and who has provided caring support throughout. Matt thanks his family, friends, and colleagues, and is grateful for his children, who give him three reasons to care passionately about the future. Most importantly, he thanks his wife, Lisa, for blessing every day of his life for the past 25 years with her keen insight, passion for life, unconscious grace, and effortless beauty—and for understanding him in ways no one else ever could. The talents, input, and advice of Susan and of Lisa have been vital to this project, and without their support our own contributions would not have been possible. We dedicate this book to today’s students, who will shape tomorrow’s world. –Jay Withgott and Matthew Laposata

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Reviewers We wish to express special thanks to the dedicated reviewers who shared their time and expertise to help make this fifth edition the best it could be. Their efforts built on those of the roughly 600 instructors and outside experts who have reviewed material for the previous four editions of this book through chapter reviews, pre-revision reviews, feature consultation, student reviews, class testing, and focus groups. Our sincere gratitude goes out to all of them.

Reviewers for the Fifth Edition

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Reviewers for Previous Editions Matthew Abbott, Des Moines Area Community College; David Aborne, University of Tennessee–Chattanooga; Jeffrey Albert, Watson Institute of International Studies; Shamim Ahsan, Metropolitan State College of Denver; Isoken T. Aighewi, University of Maryland–Eastern Shore; John V. Aliff, Georgia Perimeter College; Mary E. Allen, Hartwick College; Deniz Z. Altin, Georgia Perimeter College; Dula Amarasiriwardena, Hampshire College; Gary I. Anderson, Santa Rosa Junior College; Mark W. Anderson, The University of Maine; Corey Andries, Albuquerque Technical Vocational Institute; David M. Armstrong, University of Colorado–Boulder; David L. Arnold, Ball State University; Joseph Arruda, Pittsburg State University; Thomas W. H. Backman, Linfield College; Timothy J. Bailey, Pittsburg State University; Stokes Baker, University of Detroit; Kenneth Banks, University of North Texas; Narinder Bansal, Ohlone College; Jon Barbour, University of Colorado–Denver; Reuben Barret, Prairie State College; Morgan Barrows, Saddleback College; Henry Bart, LaSalle University; James Bartalome, University of California– Berkeley; Marilynn Bartels, Black Hawk College; David Bass, University of Central Oklahoma; Christy Bazan, Illinois State University; Christopher Beals, Volunteer State Community College; Laura Beaton, York College, City University of New York; Hans T. Beck, Northern Illinois University; Richard Beckwitt, Framingham State College; Barbara Bekken, Virginia Polytechnic Institute and State University; Elizabeth Bell, Santa Clara University; Timothy Bell, Chicago State University; David Belt, Johnson County Community College; Gary Beluzo, Holyoke Community College; Terrence Bensel, Allegheny College; Bob Bennett, University of Arkansas; William B. N. Berry, University of California, Berkeley; Kristina Beuning, University of Wisconsin–Eau Claire; Peter Biesmeyer, North Country Community College; Donna Bivans, Pitt Community College; Grady Price Blount, Texas A&M University– Corpus Christi; Marsha Bollinger, Winthrop University; Lisa K. Bonneau, Metropolitan Community College–Blue River; Bruno Borsari, Winona State University; Richard D. Bowden, Allegheny College; Frederick J. Brenner, Grove City College; Nancy Broshot, Linfield College; Bonnie L. Brown, Virginia Commonwealth University; David Brown, California State University– Chico; Evert Brown, Casper College; Hugh Brown, Ball State University; J. Christopher Brown, University of Kansas; Dan Buresh, Sitting Bull College; Dale Burnside, Lenoir-Rhyne University; Lee Burras, Iowa State University; Hauke Busch, Augusta State University; Christina Buttington, University of Wisconsin–Milwaukee; Charles E. Button, University of Cincinnati, Clermont College; John S. Campbell, Northwest College; Myra Carmen Hall, Georgia Perimeter College; Mike Carney, Jenks High School; Kelly S. Cartwright, College of Lake County; Jon Cawley, Roanoke College; Michelle Cawthorn, Georgia Southern University; Linda Chalker-Scott, University of Washington; Brad S. Chandler, Palo Alto College; Paul Chandler, Ball State University; David A. Charlet, Community College of Southern Nevada; Sudip Chattopadhyay, San Francisco State University; Tait Chirenje, Richard Stockton College; Luanne Clark, Lansing Community College; Richard Clements, Chattanooga State Technical Community College; Kenneth E. Clifton, Lewis and Clark College; Reggie Cobb, Nash Community College; John E. Cochran, Columbia Basin College; Donna Cohen, MassBay Community College; Luke W. Cole, Center on Race, Poverty, and the Environment; Mandy L. Comes, Rockingham Community College; Thomas L. Crisman, University of Florida; Jessica Crowe, South Georgia College; Ann Cutter, Randolph Community College; Gregory A. Dahlem, Northern Kentucky University; Randi Darling, Westfield State College; Mary E. Davis, University of Massachusetts, Boston;

REVIEWERS

Charles Acosta, Northern Kentucky University Eric Atkinson, Northwest College Terrence Bensel, Allegheny College Jill Bessetti, Columbia College Donna Bivans, Pitt Community College Philip A. Clifford, Volunteer State Community College Dolores M. Eggers, University of North Carolina at Asheville James English, Gardner-Webb University Jonathan Fingerut, St. Joseph’s University Robyn Fischer, Aurora University Eric J. Fitch, Marietta College Michael Freake, Lee University Karen Gaines, Eastern Illinois University Katharine A. Gehl, Asheville Buncombe Technical Community College Jeffrey J. Gordon, Bowling Green State University Jennifer A. Hanselman, Westfield State University William Hopper, Florida Memorial University Jack Jeffrey, formerly USFWS, Pepeekeo, Hawaii Richard R. Jurin, University of Northern Colorado Karen Klein, Northampton Community College Ned Knight, Linfield College George Kraemer, Purchase College Diana Kropf Gomez, Dallas County Community College Max Kummerow, Curtin University Hugh Lefcort, Gonzaga University Jeffrey Mahr, Georgia Perimeter College, Newton Allan Matthias, University of Arizona Chuck McClaugherty, University of Mount Union Annabelle McKie-Voerste, Dalton State College Alberto Mestas-Nuñez, Texas A&M University–Corpus Christi William C. Miller, Temple University Bruce Olszewski, San Jose State University Anthony Overton, East Carolina University Gulni Ozbay, Delaware State University Clayton Penniman, Central Connecticut State University Thomas Pliske, Florida International University Daniel Ratcliff, Rose State College Irene Rossell, University of North Carolina at Asheville Dana Royer, Wesleyan University Steve Rudnick, University of Massachusetts–Boston Dork Sahagian, Lehigh University Andrew Shella, Terra State Community College Jeff Slepski, Mt. San Jacinto College Rik Smith, Columbia Basin College

Michelle Stevens, California State University–Sacramento Keith S. Summerville, Drake University Todd Tracy, Northwestern College Ray Williams, Rio Hondo College Sharon Walsh, New Mexico State University

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Thomas A. Davis, Loras College; Lola M. Deets, Pennsylvania State University–Erie; Ed DeGrauw, Portland Community College; Roger del Moral, University of Washington; Bob Dennison, Lead teacher at HISD and Robert E. Lee High School; Michael L. Denniston, Georgia Perimeter College; Doreen Dewell, Whatcom Community College; Craig Diamond, Florida State University; Darren Divine, Community College of Southern Nevada; Stephanie Dockstader, Monroe Community College; Toby Dogwiler, Winona State University; Jeffrey Dorale, University of Iowa; Tracey Dosch, Waubonsee Community College; Michael L. Draney, University of Wisconsin–Green Bay; Iver W. Duedall, Florida Institute of Technology; Dee Eggers, University of North Carolina–Asheville; Jane Ellis, Presbyterian College; Amy Ellwein, University of New Mexico; JodyLee Estrada Duek, Pima Community College; Jeffrey R. Dunk, Humboldt State University; Jean W. Dupon, Menlo College; Robert M. East, Jr., Washington & Jefferson College; Margaret L. Edwards-Wilson, Ferris State University; Anne H. Ehrlich, Stanford University; Thomas R. Embich, Harrisburg Area Community College; Kenneth Engelbrecht, Metropolitan State College of Denver; Bill Epperly, Robert Morris College; Corey Etchberger, Johnson County Community College; W. F. J. Evans, Trent University; Paul Fader, Freed Hardeman University; Joseph Fail, Johnson C. Smith University; Bonnie Fancher, Switzerland County High School; Jiasong Fang, Iowa State University; Marsha Fanning, Lenoir Rhyne College; Leslie Fay, Rock Valley College; Debra A. Feikert, Antelope Valley College; M. Siobhan Fennessy, Kenyon College; Francette Fey, Macomb Community College; Steven Fields, Winthrop University; Brad Fiero, Pima Community College; Dane Fisher, Pfeiffer University; David G. Fisher, Maharishi University of Management; Linda M. Fitzhugh, Gulf Coast Community College; Doug Flournoy, Indian Hills Community College–Ottumwa; Johanna Foster, Johnson County Community College; Chris Fox, Catonsville Community College; Nancy Frank, University of Wisconsin–Milwaukee; Steven Frankel, Northeastern Illinois University; Arthur Fredeen, University of Northern British Columbia; Chad Freed, Widener University; Robert Frye, University of Arizona; Laura Furlong, Northwestern College; Navida Gangully, Oak Ridge High School; Sandi B. Gardner, Triton College; Kristen S. Genet, Anoka Ramsey Community College; Stephen Getchell, Mohawk Valley Community College; Marcia Gillette, Indiana University–Kokomo; Scott Gleeson, University of Kentucky; Sue Glenn, Gloucester County College; Thad Godish, Ball State University; Nisse Goldberg, Jacksonville University; Michele Goldsmith, Emerson College; Jeffrey J. Gordon, Bowling Green State University; John G. Graveel, Purdue University; Jack Greene, Millikan High School; Cheryl Greengrove, University of Washington; Amy R. Gregory, University of Cincinnati, Clermont College; Carol Griffin, Grand Valley State University; Carl W. Grobe, Westfield State College; Sherri Gross, Ithaca College; David E. Grunklee, Hawkeye Community College; Judy Guinan, Radford University; Gian Gupta, University of Maryland, Eastern Shore; Mark Gustafson, Texas Lutheran University; Daniel Guthrie, Claremont College; Sue Habeck, Tacoma Community College; David Hacker, New Mexico Highlands University; Greg Haenel, Elon University; Mark Hammer, Wayne State University; Grace Hanners, Huntingtown High School; Michael Hanson, Bellevue Community College; Alton Harestad, Simon Fraser University; Barbara Harvey, Kirkwood Community College; David Hassenzahl, University of Nevada Las Vegas; Jill Haukos, South Plains College; Keith Hench, Kirkwood Community College; George Hinman, Washington State University; Jason Hlebakos, Mount San Jacinto College; Joseph Hobbs, University of Missouri–Columbia; Jason Hoeksema, Cabrillo College; Curtis Hollabaugh, University of West Georgia; Robert D. Hollister, Grand Valley State University; David Hong, Diamond Bar High School; Catherine Hooey, Pittsburgh State University; Kathleen Hornberger, Widener University; Debra Howell, Chabot College; April Huff, North Seattle Community College; Pamela Davey Huggins, Fairmont State University; Barbara Hunnicutt, Seminole Community College; Jonathan E. Hutchins, Buena Vista University; James M. Hutcheon, Asian University for Women; Don Hyder, San Juan College; Daniel Hyke, Alhambra High School; Juana Ibanez, University of New Orleans; Walter Illman, University of Iowa; Neil Ingraham, California State University, Fresno; Daniel Ippolito, Anderson University; Bonnie Jacobs, Southern Methodist University; Jason Janke, Metropolitan State College of Denver; Nan Jenks-Jay, Middlebury College; Linda Jensen-Carey, Southwestern Michigan College; Stephen R. Johnson, William Penn University; Gail F. Johnston, Lindenwood University; Gina Johnston, California State University, Chico; Paul Jurena, University of Texas–San Antonio; Richard R. Jurin, University of Northern Colorado; Thomas M. Justice, McLennan Community College; Stanley S. Kabala, Duquesne University; Brian Kaestner, Saint Mary’s Hall; Steve Kahl,

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Plymouth State University; David M. Kargbo, Temple University; Susan Karr, Carson–Newman College; Jerry H. Kavouras, Lewis University; Carol Kearns, University of Colorado–Boulder; Richard R. Keenan, Providence Senior High School; Dawn G. Keller, Hawkeye Community College; Myung-Hoon Kim, Georgia Perimeter College; Kevin King, Clinton Community College; John C. Kinworthy, Concordia University; Cindy Klevickis, James Madison University; Ned J. Knight, Linfield College; David Knowles, East Carolina University; Penelope M. Koines, University of Maryland; Alexander Kolovos, University of North Carolina–Chapel Hill; Erica Kosal, North Carolina Wesleyan College; Steven Kosztya, Baldwin Wallace College; Robert J. Koester, Ball State University; Tom Kozel, Anderson College; Robert G. Kremer, Metropolitan State College of Denver; Jim Krest, University of South Florida–South Florida; Sushma Krishnamurthy, Texas A&M International University; Diana Kropf-Gomez, Richland College (DCCCD); Jerome Kruegar, South Dakota State University; James Kubicki, The Pennsylvania State University; Frank T. Kuserk, Moravian College; Diane M. LaCole, Georgia Perimeter College; Troy A. Ladine, East Texas Baptist University; William R. Lammela, Nazareth College; Vic Landrum, Washburn University; Tom Langen, Clarkson University; Andrew Lapinski, Reading Area Community College; Matthew Laposata, Kennesaw State University; Michael T. Lares, University of Mary; Kim D. B. Largen, George Mason University; John Latto, University of California– Berkeley; Lissa Leege, Georgia Southern University; James Lehner, Taft School; Kurt Leuschner, College of the Desert; Stephen D. 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College; Barry Welch, San Antonio College; Kelly Wessell, Tompkins Cortland Community College; James W.C. White, University of Colorado; Susan Whitehead, Becker College; Jeffrey Wilcox, University of North Carolina at Asheville; Richard D. Wilk, Union College; Donald L. Williams, Park University; Justin Williams, Sam Houston University; Ray E. Williams, Rio Hondo College; Roberta Williams, University of Nevada–Las Vegas; Dwina Willis, Freed-Hardeman University; Shaun Wilson, East Carolina University; Tom Wilson, University of Arizona; James Winebrake, Rochester Institute of Technology; Danielle Wirth, Des Moines Area Community College; Lorne Wolfe, Georgia Southern University; Brian G. Wolff, Minnesota State Colleges and Universities; Marjorie Wonham, University of Alberta; Wes Wood, Auburn University; Jessica Wooten, Franklin University; Jeffrey S. Wooters, Pensacola Junior College; Joan G. Wright, Truckee Meadows Community College; Michael Wright, Truckee Meadows Community College; S. Rebecca Yeomans, South Georgia College; Karen Zagula, Waketech Community College; Lynne Zeman, Kirkwood Community College; Zhihong Zhang, Chatham College. Pearson would like to thank the following people for their work on the Global Edition: Contributor Dr. Lincoln Fok, The Hong Kong Institute of Education Reviewer Dr. Sumitra Datta, SASTRA University

Suppliers of Student Reviews Christine Brady, California State Polytechnic University, Pomona Steven Rudnick, University of Massachusetts–Boston Ninian R. Stein, Wheaton College Todd Tracy, Northwestern College Lorne Wolfe, Georgia Southern University

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Environment

The Science Behind the Stories 5th Edition Global Edition

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PA R T O N E

Foundations of Environmental Science

Climber on “The Diving Board” at Half Dome in Yosemite National Park.

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1

Our Island, Earth

Science and Sustainability: An Introduction to Environmental Science Upon completing this chapter, you will be able to: Define the term environment and describe the field of environmental science Explain the importance of natural resources and ecosystem services to our lives Discuss the consequences of population growth and resource consumption

Understand the scientific method and the process of science Diagnose and illustrate some of the pressures on the global environment Articulate the concept of sustainability and describe campus sustainability efforts

Characterize the nature of environmental science

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Our Island, Earth Viewed from space, our home planet resembles a small blue marble suspended in a vast inky-black void. Earth may seem enormous to us as we go about our lives on its surface, but the astronaut’s view reveals that our planet is finite and limited. With this perspective, it becomes clear that as our population, technological power, and resource consumption all increase, so does our capacity to alter our surroundings and damage the very systems that keep us alive. Finding ways to live peacefully, healthfully, and sustainably on our diverse and complex planet is our society’s prime challenge today. Meeting this challenge will require a solid scientific understanding of natural and social systems alike. The field of environmental science is crucial in this endeavor.

Our environment surrounds us

Environmental science explores our interactions with the world Understanding our relationship with the world around us is vital because we depend utterly on our environment for air, water, food, shelter, and everything else essential for living. Moreover, we modify our environment. Many of our actions have enriched our lives, bringing us better health, longer life spans, and greater material wealth, mobility, and leisure time—yet they have also often degraded the natural systems that sustain us. Impacts such as air and water pollution, soil erosion, and species extinction compromise our well-being and jeopardize our ability to build a society that will survive and thrive in the long term. Environmental science is the study of how the natural world works, how our environment affects us, and how we affect our environment. We need to understand how we

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We rely on natural resources An island by definition is finite and bounded, and its inhabitants must cope with limitations in the materials they need. On our island—planet Earth—human beings, like all living things, ultimately face environmental constraints. Specifically, there are limits to many of our natural resources, the substances and energy sources that we take from our environment and that we need in order to survive. Natural resources that are replenished over short periods are known as renewable natural resources. Some renewable natural resources, such as sunlight, wind, and wave energy, are perpetually renewed and essentially inexhaustible. In contrast, nonrenewable natural resources, such as minerals and crude oil, are in finite supply and are formed much more slowly than we use them. Once we deplete a nonrenewable resource, it is no longer available. We can view the renewability of natural resources as a continuum (FIGURE 1.1). Renewable resources such as timber, water, and soil renew themselves over months, years, or decades, and can be depleted if we use them faster than they are replenished. For example, pumping groundwater faster than it is restored can deplete underground aquifers and turn lush landscapes into deserts. Populations of animals and plants we harvest from the wild may vanish if we overharvest them.

We rely on ecosystem services If we think of natural resources as “goods” produced by nature, then it is also true that Earth’s natural systems provide “services” on which we depend. Our planet’s ecological systems purify air and water, cycle nutrients, regulate climate, pollinate plants, and receive and recycle our waste. Such essential services are commonly called ecosystem services. Ecosystem services arise from the normal functioning of natural systems and are not meant for our benefit, yet we could not survive without them. Later we will examine the countless and profound ways that ecosystem services support our lives and civilization (pp. 134–135, 170, 308). Just as we may deplete natural resources, we may degrade ecosystem services. This can occur when we deplete resources, destroy habitat, or generate pollution. In recent years, our depletion of nature’s goods and our disruption of nature’s services have intensified, driven by rising affluence and a human population that grows larger every day.

C H A P T E R 1 • S C I E N C E A N D S U S TA I N A B I L I T Y: A N I N T R O D U C T I O N T O E N V I R O N M E N TA L S C I E N C E

A photograph of Earth offers a revealing perspective, but it cannot convey the complexity of our environment. Our environment consists of all the living and nonliving things around us. It includes the continents, oceans, clouds, and ice caps you can see in the photo of Earth from space, as well as the animals, plants, forests, and farms that comprise the landscapes surrounding us. In a more inclusive sense, it also encompasses the structures, urban centers, and living spaces that people have created. In its broadest sense, our environment includes the complex webs of social relationships and institutions that shape our daily lives. People commonly use the term environment in the first, most narrow sense—to mean a nonhuman or “natural” world apart from human society. This usage is unfortunate, because it masks the vital fact that people exist within the environment and are part of nature. As one of many species on Earth, we share with others the same dependence on a healthy, functioning planet. The limitations of language make it all too easy to speak of “people and nature,” or “humans and the environment,” as though they were separate and did not interact. However, the fundamental insight of environmental science is that we are part of the “natural” world and that our interactions with the rest of it matter a great deal.

interact with our environment in order to devise solutions to our most pressing challenges. It can be daunting to reflect on the sheer magnitude of environmental dilemmas that confront us today, but these problems also bring countless opportunities for creative solutions. Environmental scientists study the issues most centrally important to our world and its future. Right now, global conditions are changing more quickly than ever. Right now, through science, we are gaining knowledge more rapidly than ever. And right now, the window of opportunity for acting to solve problems is still open. With such bountiful opportunities, this particular moment in history is indeed an exciting time to be alive—and to be studying environmental science.

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Renewable natural resources

Nonrenewable natural resources

• Sunlight • Wind energy • Wave energy • Geothermal energy

• Fresh water • Forest products • Agricultural crops • Soils

• Crude oil • Natural gas • Coal • Copper, aluminum, and other metals

Figure 1.1 Natural resources lie along a continuum from perpetually renewable to nonrenewable. Perpetually renewable, or inexhaustible, resources such as sunlight and wind energy (left), will always be there for us. Renewable resources such as timber, soils, and fresh water (center) may be replenished on intermediate time scales, if we are careful not to deplete them. Nonrenewable resources such as oil and coal (right) exist in limited amounts that could one day be gone.

Population growth amplifies our impact For nearly all of human history, fewer than a million people populated Earth at any one time. Today our population has grown beyond 7 billion people. This means that for every one person who used to exist, several thousand people exist today! FIGURE 1.2 shows just how recently and suddenly this dramatic change has come about. Two phenomena triggered our remarkable increase in population size. The first was our transition from a huntergatherer lifestyle to an agricultural way of life. This change began around 10,000 years ago and is known as the agricultural r­ evolution. As people began to grow crops, domesticate animals, and live sedentary lives on farms and in villages, they

6 5 4 3

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Figure 1.2 The global human population increased after the agricultural revolution and then skyrocketed as a result of the industrial revolution. Data compiled from U.S. Census Bureau, U.N. Population Division, and other sources.

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produced more food to meet their nutritional needs and began having more children. The second notable phenomenon, known as the industrial revolution, began in the mid-1700s. It entailed a shift from rural life, animal-powered agriculture, and handcrafted goods toward an urban society provisioned by the mass production of factorymade goods and powered by fossil fuels (nonrenewable energy sources including oil, coal, and natural gas; pp. 542–544). Industrialization brought technological advances and improvements in sanitation and medicine, and it enhanced agricultural production through the use of fossil-fuel-powered equipment and synthetic pesticides and fertilizers (pp. 236, 265). The factors driving population growth have brought us better lives in many ways. Yet as our world fills up with people, population growth has begun to threaten our well-being. We must ask how well the planet can accommodate 7 billion of us—or the 9 billion forecast by 2050. Already our sheer numbers, unparalleled in history, are putting unprecedented stress on natural systems and the availability of resources.

Resource consumption exerts social and environmental pressures Besides stimulating population growth, industrialization increased the amount of resources each one of us consumes. As we mined energy sources and manufactured ever-greater numbers of goods, we enhanced the material affluence of many of the world’s people. In the process, however, human society has consumed more and more of the planet’s limited resources. One way to quantify resource consumption is to use the concept of the “ecological footprint,” developed in the 1990s by environmental scientists Mathis Wackernagel and William Rees. An ecological footprint expresses environmental impact in terms

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Global footprint (number of planets)

1.6 1.4 1.2

Biocapacity Overshoot

1.0 0.8 0.6

Ecological footprint

0.4 0.2 0 1960

1970

1980

1990

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Figure 1.4 Data indicate that we have overshot Earth’s biocapacity—its capacity to support us—by 50%. We are using renewable natural resources 50% faster than they are being replenished. Data from WWF, 2012. Living planet report 2012. WWF International, Gland, Switzerland.

Figure 1.3 An “ecological footprint” represents the total area of biologically productive land and water needed to produce the resources and dispose of the waste for a given person or population. Adapted from an illustration by Philip Testemale in Wackernagel, M., and W. Rees, 1996. Our ecological footprint: Reducing human impact on the Earth. Gabriola Island, British Columbia: New Society Publishers.

of the cumulative area of biologically productive land and water required to provide the resources a person or population consumes and to dispose of or recycle the waste the person or population produces (FIGURE 1.3). It measures the total area of Earth’s biologically productive surface that a given person or population “uses” once all direct and indirect impacts are totaled up. For humanity as a whole, Wackernagel and his colleagues calculate that our species is now using 50% more of the planet’s resources than are available on a sustainable basis. That is, we are depleting renewable resources by using them 50% faster than they are being replenished. This is essentially like drawing the money out of a bank account rather than living off the interest the money makes. This excess use has been termed overshoot because we are overshooting, or surpassing, Earth’s capacity to sustainably support us (FIGURE 1.4). Moreover, people from wealthy nations such as the United States have much larger ecological footprints than do people from poorer nations. If all the world’s people consumed resources at the rate of U.S. citizens, we would need the equivalent of four planet Earths.

Environmental science can help us avoid past mistakes It remains to be seen what consequences resource consumption and population growth will have for today’s global

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society, but historical evidence shows that civilizations can crumble when pressures from population and consumption overwhelm resource availability. Historians have inferred that environmental degradation contributed to the fall of the Greek and Roman empires; the Angkor civilization of Southeast Asia; and the Maya, Anasazi, and other civilizations of the New World. In Iraq and other regions of the Middle East, areas that are barren desert today were lush enough to support the origin of agriculture when great ancient societies thrived there. Easter Island has long been held up as the most striking case of a society’s self-destruction after depleting its resources, although new research disputes this interpretation (see THE SCIENCE BEHIND THE STORY, pp. 24–25). In his 2005 book Collapse, scientist and author Jared Diamond synthesized existing research and formulated general reasons why civilizations succeed and persist, or fail and collapse. Success and persistence, he argued, depend largely on how societies interact with their environments and on how they respond to problems. In today’s globalized society, the stakes are higher than ever because our environmental impacts are global. If we cannot forge sustainable solutions to our problems, then the resulting societal collapse will be global. Fortunately, environmental science holds keys to building a better world. By studying environmental science, you will learn to evaluate the many changes happening around us and to think critically and creatively about ways to respond.

The Nature of Environmental Science Environmental scientists aim to comprehend how Earth’s natural systems function, how these systems affect people, and how we are influencing those systems. Many environmental

C H A P T E R 1 • S C I E N C E A N D S U S TA I N A B I L I T Y: A N I N T R O D U C T I O N T O E N V I R O N M E N TA L S C I E N C E

How much larger is the global ecological footprint today than it was half a century ago?

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THE SCIENCE BEHIND THE STORY What are the Lessons of Easter Island? A mere speck of land in the vast Pacific Ocean, fully 3750 km (2325 mi) from South America, Easter Island is one of the most remote spots on the globe. Yet this far-flung island—called Rapa Nui by its inhabitants—is the focus of an intense debate among scientists seeking to clarify its enigmatic history and decipher the lessons it has to offer us. Ever since European explorers stumbled upon Rapa Nui on Easter Sunday, 1722, outsiders have been struck by the island’s barren landscape. Early European accounts suggested that the 2000–3000 people living on the island seemed impoverished, subsisting on a few meager crops and possessing only stone tools. Yet the forlorn island also featured hundreds of gigantic statues of carved rock. How could people without wheels or ropes, on an island without trees, have moved 90-ton statues 10 m (33 ft) high as far as 10 km (6.2 mi) from the quarry where they were chiseled to the sites where they were erected? Apparently some calamity must have befallen a once-mighty civilization. Many researchers have set out to solve Easter Island’s mysteries. A key discovery was that the island was once lushly forested. Scientist John Flenley and his colleagues drilled cores deep into lake sediments and examined ancient pollen grains preserved there, seeking to reconstruct, layer by layer, the history of vegetation in the region. Finding a great deal of palm pollen, they inferred that when Polynesian people colonized the island (a.d. ­300–900, they estimated), it was covered with palm trees similar to the Chilean wine palm—a tall, slow-growing tree that can live for centuries. Archaeologists found ancient palm nut casings buried in soil near carbon-lined channels made by palm roots. Researchers deciphering script

Easter Island’s immense statues

on stone tablets discerned characters etched in the form of palm trees. By studying pollen and the remains of wood from charcoal, archaeologist Catherine Orliac found that at least 21 other plant species—now gone—had also been common. Clearly the island had supported a diverse forest. Forest plants would have provided fuelwood, building material for houses and canoes, fruit to eat, fiber for clothing— and, researchers guessed, logs and fibrous rope to help move statues. Pollen analysis showed that trees declined, replaced by ferns and grasses. Then between 1400 and 1600, pollen levels plummeted. Charcoal in the soil proved the forest had been burned, likely in slash-andburn farming. Researchers concluded that the islanders, desperate for forest resources and cropland, had deforested their own island. With the forest gone, soil eroded away (data from lake bottoms showed a great deal of sediment accumulating). Erosion would have lowered yields of bananas, sugarcane, and sweet potatoes, perhaps leading to starvation and population decline. Further evidence indicated that wild animals disappeared. Archaeologist David Steadman analyzed 6500 bones and found that at least 31 bird species provided food for the islanders.

Today, only one native bird species is left. Remains from charcoal fires show that early islanders feasted on fish, sharks, porpoises, turtles, octopus, and shellfish—but in later years they consumed little seafood. As resources declined, researchers concluded, people fell into clan warfare, revealed by unearthed weapons and skulls with head wounds. Rapa Nui appeared to be a tragic case of ecological suicide: A once-flourishing civilization depleted its resources and destroyed itself. In this interpretation— advanced by Flenley and writer Paul Bahn, and by scientist Jared ­Diamond in his best-selling 2005 book Collapse—Rapa Nui seemed to offer a clear lesson: We on our global island, planet Earth, had better learn to use our limited resources sustainably. When Terry Hunt and Carl Lipo began research on Rapa Nui in 2001, they expected simply to help fill gaps in a well-understood history. But science is a process of discovery, and sometimes evidence leads researchers far from where they anticipated. For Hunt, an anthropologist at University of Hawaii at Manoa, and Lipo, an archaeologist at California State University, Long Beach, their work ended up convincing them that nearly everything about the traditional “ecocide” interpretation was wrong.

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on other islands. Moreover, people brought the rats, so the forest was still destroyed as a result of human colonization. Despite the forest loss, Hunt and Lipo argue that islanders were able to persist and thrive. Archaeology shows how islanders adapted to Rapa Nui’s poor soil and windy weather by developing rock gardens to protect crop plants and nourish the soil. Tools that previous researchers viewed as weapons were actually farm implements, Hunt and Lipo concluded; lethal injuries were rare; and no evidence of battle or defensive fortresses was uncovered. Hunt, Lipo, and others also unearthed old roads and inferred how the statues were transported. It had been thought that a powerful central authority forced armies of laborers to move them, but Hunt and Lipo concluded that small numbers of people could move them by tilting and rocking them upright like refrigerators. Indeed, the distribution of statues on the island suggested the work of family

Were the haunting statues of Easter Island (Rapa Nui) erected by a civilization that collapsed after devastating its environment, or by a sustainable civilization that fell because of outside influence?

groups. Islanders had adapted to their resource-poor environment by becoming a peaceful and cooperative society, with the statues providing a harmless outlet for competition over status and prestige. Altogether, the evidence led Hunt and Lipo to propose that far from destroying their environment, the islanders had acted as responsible stewards. The collapse of this sustainable civilization, they argue, came with the arrival of Europeans, who unwittingly brought contagious diseases to which the islanders had never been exposed. Indeed, historical journals of sequential European voyages depict a society falling into disarray as if reeling from epidemics, its statues tumbling around it. Peruvian ships then began raiding Rapa Nui and taking islanders away into slavery. Foreigners acquired the land, forced the remaining people into labor, and introduced thousands of sheep, which destroyed the few native plants left on the island. Thus, the collapse of Rapa Nui civilization resulted from a barrage of disease, violence, and slave-raids following foreign contact. Before that, Hunt and Lipo say, Rapa Nui’s people boasted 500 years of a peaceful and resilient society. Hunt and Lipo’s interpretation, put forth in a 2011 book, The Statues That Walked, represents a paradigm shift (p. 31) in how we view Easter Island. Debate between the two camps remains heated. Meanwhile, research continues as scientists look for new ways to test the differing hypotheses. In the long-term, data from additional studies should lead us closer and closer to the truth. Like the people of Rapa Nui, we are all stranded together on an island with limited resources. What is the lesson of Easter Island for our global island, Earth? Perhaps there are two: That any island population must learn to live within its means—but that with care and ingenuity, there is hope that we can.

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First, their radiocarbon dating (p. 42) indicated that people had not colonized the island until about a.d. 1200. This finding suggested that deforestation occurred suddenly, soon after arrival. How could so few people have destroyed so much forest so fast? Hunt and Lipo’s answer: rats. When Polynesians settled new islands, they brought crop plants, domestic animals such as chickens, and rats. Whether rats were stowaways or were brought intentionally as food is not known. In either case, rats can multiply quickly, and they soon overran Rapa Nui. Rats ate palm nuts (researchers see their tooth marks on old nut casings). Hunt and Lipo suggest they ate so many nuts and shoots that the trees could not regenerate. With no young trees growing, the palm went extinct once mature trees died. Diamond and others counter that over 20 additional plant species went extinct on Rapa Nui, that plenty of palm nuts escaped rat damage, and that most plants survived rats

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scientists are motivated by a desire to develop solutions to environmental problems. These solutions (such as new technologies, policy decisions, or resource management strategies) are applications of environmental science. The study of such applications and their consequences is, in turn, also part of environmental science.

Environmental science is interdisciplinary Studying our interactions with our environment is a complex endeavor that requires expertise from many disciplines, including ecology, earth science, chemistry, biology, geography, economics, political science, demography, ethics, and others. Environmental science is thus an interdisciplinary field—one that borrows techniques from multiple disciplines and brings their research results together into a broad synthesis (FIGURE 1.5). Traditional established disciplines are valuable because their scholars delve deeply into topics, developing expertise in particular areas and uncovering new knowledge. In contrast, interdisciplinary fields are valuable because their practitioners consolidate and synthesize the specialized knowledge from many disciplines and make sense of it in a broad context to better serve the multifaceted interests of society. Environmental science is especially broad because it encompasses not only the natural sciences (disciplines that examine the natural world), but also the social sciences (disciplines that address human interactions and institutions). Most environmental science programs focus more on the natural sciences, whereas programs that emphasize the social sciences often use the term environmental studies. Whichever approach one takes, these fields bring together many diverse perspectives and sources of knowledge. Just as an interdisciplinary approach to studying issues can help us better understand them, an integrated approach to addressing environmental problems can produce ­effective

Ethics

Environmental science arose in the latter half of the 20th century as people sought to better understand environmental problems, their origins, and their solutions. However, the perception of what constitutes a problem may vary from one person to another, or from one situation to another. A person’s age, gender, class, race, nationality, employment, income, and educational background can all affect whether he or she considers a given environmental condition or change to be a “problem.” For instance, Americans today are more likely to view the application of the pesticide DDT as a problem than in the 1940s and 1950s, because today more is known about the health risks of pesticides (FIGURE 1.6). However, a person living

Biology

Chemistry

Engineering

Environmental science

Political science

Atmospheric science

Oceanography

History

Anthropology

Geology

Archaeology Geography

Figure 1.5 Environmental science is an interdisciplinary pursuit. It involves input from many different established fields of study across the natural sciences and social sciences.

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People vary in how they perceive environmental problems

Ecology

Economics

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solutions for society. For example, we used to add lead to gasoline to make cars run more smoothly, even though researchers knew that lead emissions from tailpipes caused health problems, including brain damage and premature death. In 1970 air pollution was severe, and motor vehicles accounted for 78% of U.S. lead emissions. In response, environmental scientists, engineers, medical researchers, and policymakers all merged their knowledge and skills into a process that eventually brought about a ban on leaded gasoline. By 1996 all gasoline sold in the United States was unleaded, and the nation’s largest source of atmospheric lead pollution had been completely eliminated.

Figure 1.6 How a person or a society defines an environmental problem can vary with time and circumstance. In 1945, health hazards of the pesticide DDT were not yet known, so children were doused with the chemical to treat head lice. Today, knowing of its toxicity to people, many developed nations have banned DDT. However, in developing countries where malaria is a public health threat, DDT is welcomed as a means of eradicating mosquitoes that transmit the disease.

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today in a malaria-infested village in Africa may welcome the use of DDT if it kills mosquitoes that transmit malaria, because he or she may view malaria as a more immediate health threat. Thus an African and an American who have each knowledgeably assessed the pros and cons may, because of differences in their circumstances, differ in their attitude toward DDT. People also vary in their awareness of problems. For example, in many cultures women are responsible for collecting water and fuelwood, and as a result they perceive environmental degradation that affects these resources more readily than men do. Moreover, in most societies information about environmental health risks tends to reach wealthy people more readily than poor people. Thus, who you are, where you live, and what you do influences how you perceive your environment, how change affects you, and how you react to change.

Environmental science is not the same as environmentalism

FAQ

Aren’t environmental scientists also environmentalists?

Not necessarily. Although environmental scientists search for solutions to environmental problems, they strive to keep their research rigorously objective and free from advocacy. Of course, like all human beings, scientists are motivated by personal values and interests—and like any human endeavor, science can never be entirely free of social influence. Yet while personal values and social concerns may help shape the questions scientists ask, scientists do their utmost to carry out their work impartially and to interpret their results with wideopen minds. Remaining open to whatever conclusions the data demand is a hallmark of the effective scientist.

The Nature of Science Modern scientists describe science as a systematic process for learning about the world and testing our understanding of it. The term science is also commonly used to refer to the accumulated body of knowledge that arises from this dynamic process of questioning, observation, testing, and discovery. Knowledge gained from science can be applied to address societal needs—for instance, to develop technology or to

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inform policy and management decisions (FIGURE 1.8). Many scientists are motivated by the potential for developing useful applications, whereas others are motivated simply by a desire to understand how the world works. Why does science matter? As astronomer and author Carl Sagan wrote in his 1995 treatise, The Demon Haunted World: Science as a Candle in the Dark, “We’ve arranged a global civilization in which the most crucial elements—transportation, communications, and all other industries; agriculture, medicine, education, entertainment, protecting the environment; and even the key democratic institution of voting—profoundly depend on science and technology.” Indeed, from the food we eat to the clothing we wear to the healthcare we depend on, virtually everything in our lives has been improved by the application of science. Sagan and countless other thinkers have argued that science is essential if we hope to develop solutions to the challenges we face.

Scientists test ideas by critically examining evidence Science is all about asking and answering questions. Scientists examine how the world works by making observations, taking measurements, and testing whether their ideas are supported by evidence. The effective scientist thinks critically and does not simply accept conventional wisdom from others. The scientist becomes excited by novel ideas but is skeptical and judges ideas by the strength of evidence that supports them. In these ways, scientists are good role models for all of us, because we can all benefit from learning to think critically in our everyday lives. A great deal of scientific work is observational science or descriptive science, research in which scientists gather basic information about organisms, materials, systems, or processes that are not yet well known. In this approach, researchers explore new frontiers of knowledge by observing and measuring phenomena to gain a better understanding of them. Such research is common in traditional fields such as astronomy, paleontology, and taxonomy, as well as in newer, fast-growing fields such as molecular biology and genomics.

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Although many environmental scientists are interested in solving problems, it would be incorrect to confuse environmental science with environmentalism or environmental activism. They are very different. Environmental science involves the scientific study of the environment and our interactions with it. In contrast, environmentalism is a social movement dedicated to protecting the natural world—and, by extension, people—from undesirable changes brought about by human actions (FIGURE 1.7).

Figure 1.7 Environmental scientists play roles very different from those of environmental activists, like those shown here. Although many environmental scientists search for solutions to environmental problems, they aim to keep their research objective and to avoid advocacy.

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Because science is an active, creative process, innovative researchers regularly depart from the traditional scientific method when particular situations demand it. Moreover, scientists in different fields approach their work differently because they deal with dissimilar types of information. A natural scientist, such as a chemist, conducts research quite differently than a social scientist, such as a sociologist. Nonetheless, scientists of all persuasions broadly agree on fundamental elements of the process of scientific inquiry. As practiced by individual researchers or research teams, the scientific method (FIGURE 1.9) typically consists of the steps outlined below.

Make observations  Advances in science typically begin (a) Chevy Volt, an electric hybrid car

with the observation of some phenomenon that the scientist wishes to explain. Observations set the scientific method in motion and also function throughout the process.

Ask questions  Curiosity is a fundamental human characteristic. Just observe the explorations of young children in a new environment—they want to touch, taste, watch, and listen to everything that catches their attention, and as soon as they can speak, they begin asking questions. Scientists, in this respect, are kids at heart. Why are certain plants or animals less common today than they once were? Why are storms becoming more severe and flooding more frequent? What is causing excessive growth of algae in local ponds? When ­pesticides poison fish or frogs, are people also affected? All of these are questions environmental scientists ask. Scientific method Observations

(b) Prescribed burning

Figure 1.8 Scientific knowledge can be applied in engineering and technology and in policy and management decisions. Energy-efficient electric automobiles such as the Chevy Volt (a) are technological advances made possible by materials and energy research. Prescribed burning (b), shown here in the Ouachita National Forest, Arkansas, is a management practice to restore healthy forests that is informed by scientific research into forest ecology.

Once enough basic information is known about a subject, scientists can begin posing questions that seek deeper explanations about how and why things are the way they are. At this point they may pursue hypothesis-driven science, research that proceeds in a more targeted and structured manner, using experiments to test hypotheses within a framework traditionally known as the scientific method.

The scientific method is a traditional approach to research

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The scientific method is a technique for testing ideas with observations. There is nothing mysterious or intimidating about the scientific method; it is merely a formalized version of the way any of us might naturally use logic to resolve a question.

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Questions

Hypothesis

Predictions

Test

Fail to reject hypothesis. Test a new prediction.

Reject hypothesis. Form a new one.

Results

Figure 1.9 The scientific method is the traditional experimental approach that scientists use to learn how the world works. This simple diagram, although useful and instructive, cannot convey the true dynamic and creative nature of science. Researchers often pursue their work in ways that vary legitimately from this model.

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Develop a hypothesis  Scientists address their questions by devising explanations that they can test. A h ­ ypothesis is a statement that attempts to explain a phenomenon or answer a scientific question. For example, a scientist investigating the question of why algae are growing excessively in local ponds might observe that chemical fertilizers are being applied on farm fields nearby. The scientist might then propose a hypothesis as follows: “Agricultural fertilizers running into ponds cause the amount of algae in the ponds to increase.” Make predictions  The scientist next uses the hypothesis to generate predictions, specific statements that can be directly and unequivocally tested. In our algae example, a researcher might predict: “If agricultural fertilizers are added to a pond, the quantity of algae in the pond will increase.” Test the predictions  Scientists test predictions by gath-

Analyze and interpret results  Scientists record data, or information, from their studies (FIGURE 1.10). They particularly value quantitative data (information expressed using numbers), because numbers provide precision and are easy to compare. The scientist running the fertilization experiment, for instance, might quantify the area of water surface covered by algae in each pond or might measure the dry weight of algae in a certain volume of water taken from each. It is vital, however, to collect data that is representative. Because it is impractical to measure a pond’s total algal growth, our researcher would instead sample from multiple areas of the pond. These areas must be selected in a random manner, since choosing areas with the most growth or the least growth, or areas most convenient to sample, would not provide a representative sample. Even with the precision that numbers provide, a scientist’s results may not be clear-cut. Data from treatments and controls may vary only slightly, or replicates may yield different results. The researcher must therefore analyze the data using statistical tests. With these mathematical methods,

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Figure 1.10 Researchers gather data in order to test predictions in experiments. Here, Dr. Jennifer Smith of the Scripps Institution of Oceanography in San Diego photographs coral at a remote reef in the South Pacific. Data from analysis of the photos will help her test hypotheses about how human impacts affect the condition and community structure of coral reefs.

s­ cientists can determine objectively and precisely the strength and reliability of patterns they find. Some research, especially in the social sciences, involves data that is qualitative, or not expressible in terms of numbers. Research involving historical texts, personal interviews, surveys, case studies, or descriptive observation of behavior can include qualitative data on which quantitative statistical analysis may not be possible. If experiments disprove a hypothesis, the scientist will reject it and may formulate a new hypothesis to replace it. If experiments fail to disprove a hypothesis, this lends support to the hypothesis but does not prove it is correct. The scientist may choose to generate new predictions to test the hypothesis in different ways and further assess its likelihood of being true. Thus, the scientific method loops back on itself, often giving rise to repeated rounds of hypothesis revision and new experimentation (see Figure 1.9). If repeated tests fail to reject a hypothesis, evidence in favor of it accumulates, and the researcher may eventually conclude that the hypothesis is well supported. Ideally, the scientist

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ering evidence that could potentially refute them and thus disprove the hypothesis. The strongest form of evidence comes from experimentation. An ­experiment is an activity designed to test the validity of a prediction or a hypothesis. It involves manipulating variables, or conditions that can change. For example, a scientist could test the prediction linking algal growth to fertilizer by selecting two identical ponds and adding fertilizer to one of them. In this example, fertilizer input is an independent variable, a variable the scientist manipulates, whereas the quantity of algae that results is the dependent variable, one that depends on the fertilizer input. If the two ponds are identical except for a single independent variable (fertilizer input), then any differences that arise between the ponds can be attributed to that variable. Such an experiment is known as a controlled experiment because the scientist controls for the effects of all variables except the one he or she is testing. In our example, the pond left unfertilized serves as a control, an unmanipulated point of comparison for the manipulated treatment pond. Whenever possible, it is best to replicate one’s experiment; that is, to stage multiple tests of the same comparison. Our scientist could perform a replicated experiment on, say, 10 pairs of ponds, adding fertilizer to one of each pair.

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would want to test all possible explanations. For instance, our researcher might formulate an additional hypothesis, proposing that algae increase in fertilized ponds because chemical fertilizers diminish the numbers of fish or invertebrate animals that eat algae. It is possible, of course, that both hypotheses could be correct and that each may explain some portion of the initial observation that local ponds were experiencing algal blooms.

We test hypotheses in different ways

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The scientific process continues beyond the scientific method Scientific work takes place within the context of a community of peers. To have impact, a researcher’s work must be published and made accessible to this community. Thus, the scientific method is embedded within a larger process involving the scientific community as a whole (FIGURE 1.11).

Peer review  When a researcher’s work is done and the An experiment in which the researcher actively chooses results analyzed, he or she writes up the findings and suband manipulates the independent variable is known as a mits them to a journal (a scholarly publication in which scimanipulative experiment. A manipulative experiment provides entists share their work). The journal’s editor asks several the strongest type of evidence a scientist can obtain, because other scientists who specialize in the subject area to examine it can reveal causal relationships, showing that changes in an the manuscript, provide comments and criticism (generally independent variable cause changes in a dependent variable. In anonymously), and judge whether the work merits publication practice, however, we cannot run manipulative experiments for in the journal. This procedure, known as peer review, is an all questions, especially for processes involving large spatial essential part of the scientific process. scales or long time scales. For example, in studying the effects Peer review is a valuable guard against faulty research of global climate change (Chapter 18), we cannot run a manipcontaminating the literature on which all scientists rely. ulative experiment adding carbon dioxide to 10 treatment planHowever, because scientists are human, personal biases and ets and 10 control planets and then compare the results! politics can sometimes creep into the review process. FortuThus, in environmental science, it is common for researchnately, just as individual scientists strive to remain objective ers to run n ­ atural experiments, which compare how dependent in conducting their research, the scientific community does variables are expressed in naturally different contexts. In such its best to ensure fair review of all work. Winston Churchill experiments, the independent variable varies naturally, and once called democracy the worst form of government, except researchers test their hypotheses by searching for correlation, or statistical association among variables. For instance, let’s suppose our sciScientific process (as practiced by scientific community) entist studying algae surveys 50 ponds, 25 of which happen to be fed by fertilizer runoff from nearby farm fields and 25 of which are not. Let’s say he or she Further finds seven times more algal growth in research by scientific the fertilized ponds than in the unfertiScientific method (as practiced by community lized ponds. The scientist would conindividual researcher or research group) clude that algal growth is correlated with fertilizer input; that is, that one tends to Observations Publication increase along with the other. in This type of evidence is not as scientific strong as the causal demonstration that journal Questions manipulative experiments can provide, but often a natural experiment is the only feasible approach for studying a subject Hypothesis Paper accepted Paper rejected of immense scale, such as an ecosystem or a planet. Because many questions Revise Predictions in environmental science are complex paper and exist on large scales, they must be Reject Fail to addressed with correlative data. As such, hypothesis reject Test environmental scientists cannot always Peer review hypothesis provide clear-cut, black-and-white answers to questions from policymakResults ers and the public. Nonetheless, good correlative studies can make for very Scientific paper strong science, and they preserve the real-world complexity that manipulative experiments often sacrifice. Whenever Figure 1.11 The scientific method followed by individual research teams exists within possible, scientists try to integrate natu- the overall process of science at the level of the scientific community. This process ral and manipulative experiments to gain includes peer review and publication of research, acquisition of funding, and the elaboration of the advantages of each. theory through the cumulative work of many researchers.

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for all the others that had been tried. The same might be said about peer review; it is an imperfect system, yet it is the best we have.

Conference presentations  Scientists frequently present their work at professional conferences, where they interact with colleagues and receive comments on their research. Such feedback can help improve a researcher’s work before it is submitted for publication.

WEIGHING THE ISSUES FOLLOW THE MONEY  Let us say you are a research scientist, and you want to study the impacts of chemicals released into lakes by pulp-and-paper mills. Obtaining research funding has been difficult. Then a representative from a large pulp-andpaper company contacts you. The company also is interested in how its chemical effluents affect water bodies, and it would like to fund your research. What are the benefits and drawbacks of this offer? Would you accept the offer?

Repeatability  The careful scientist may test a hypothesis repeatedly in various ways. Following publication, other scientists may attempt to reproduce the results in their own experiments and analyses. Scientists are inherently cautious about accepting a novel hypothesis, so the more a result can be reproduced by different research teams, the more confidence scientists will have that it provides the correct explanation for an observed phenomenon. Theories  If a hypothesis survives repeated testing by numerous research teams and continues to predict experimental outcomes and observations accurately, it may potentially be incorporated into a theory. A theory is a widely accepted, well-tested explanation of one or more cause-andeffect relationships that has been extensively validated by a great amount of research. Whereas a hypothesis is a simple explanatory statement that may be disproven by a single experiment, a theory consolidates many related hypotheses that have been supported by a large body of experimental and observational data.

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Applications  Knowledge gained from scientific research may be applied to help meet society’s needs and address society’s problems. As discussed earlier (see Figure 1.8), scientific research informs and facilitates new technologies, engineering approaches, policy decisions, and management strategies. Still, even when research is able to provide clear information, deciding on the optimal social response to a problem can be difficult. Moreover, many predicaments addressed by environmental science are so-called wicked problems: problems complex enough to have no simple solution and whose very nature changes over time. For this reason, society will benefit if it trains and funds scientists to continue studying such problems as they evolve.

Science goes through “paradigm shifts” As the scientific community accumulates data in an area of research, interpretations sometimes may change. Thomas Kuhn’s influential 1962 book The Structure of Scientific Revolutions argued that science goes through periodic upheavals in thought, in which one scientific paradigm, or dominant view, is abandoned for another. For example, before the 16th century, European scientists believed that Earth was at the center of the universe. Their data on the movements of planets fit that concept somewhat well—yet the idea eventually was disproved after Nicolaus Copernicus showed that placing the sun at the center of the solar system explained the planetary data much better. Another paradigm shift occurred in the 1960s, when geologists accepted plate tectonics (pp. 52–54). By this time, evidence for the movement of continents and the action of tectonic plates had accumulated and become overwhelmingly convincing. Paradigm shifts demonstrate the strength and vitality of science, showing science to be a process that refines and improves itself through time. Understanding how science works is vital to assessing how scientific interpretations progress through time as information accrues. This is especially relevant in environmental science— a young field that is changing rapidly as we attain vast amounts of new information, as human impacts on our planet multiply, and as we gather lessons from the consequences of our actions.

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Grants and funding  To fund their research, most scientists need to spend enormous amounts of time requesting money from private foundations or from government agencies such as the National Science Foundation. Grant applications undergo peer review just as scientific papers do, and competition for funding is generally intense. Scientists’ reliance on funding sources can occasionally lead to conflicts of interest. A researcher who obtains data showing his or her funding source in an unfavorable light may be reluctant to publish the results for fear of losing funding— or worse yet, could be tempted to doctor the results. This situation can arise, for instance, when an industry funds research to test its products for safety or environmental impact. Most scientists resist these pressures, but when you are critically assessing a scientific study, it is always a good idea to note where the researchers obtained their funding.

Note that scientific use of the word theory differs from popular usage of the word. In everyday language when we say something is “just a theory,” we are suggesting it is a speculative idea without much substance. However, scientists mean just the opposite when they use the term. To them, a theory is a conceptual framework that effectively explains a phenomenon and has undergone extensive and rigorous testing, such that confidence in it is extremely strong. For example, Darwin’s theory of evolution by natural selection (pp. 68–71) has been supported and elaborated by many thousands of studies over 150 years of intensive research. Large bodies of research have shown repeatedly and in great detail how plants and animals change over generations, or evolve, expressing characteristics that best promote survival and reproduction. Because of its strong support and explanatory power, evolutionary theory is the central unifying principle of modern biology. Other prominent scientific theories include atomic theory, cell theory, big bang theory, plate tectonics, and general relativity.

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Sustainability and Our Future Throughout this book you will encounter environmental scientists asking questions, testing hypotheses, conducting experiments, analyzing data, and drawing conclusions about the causes and consequences of environmental change. Environmental scientists who study the condition of our environment and the consequences of our impacts are addressing the most centrally important issues of our time.

Brazil (2.9 ha)

United States (7.2 ha)

Mexico (3.3 ha) Afghanistan (0.5 ha)

Achieving sustainable solutions is vital The primary challenge in our increasingly populated world is how to live within our planet’s means, such that Earth and its resources can sustain us—and all life—for the future. This is the challenge of sustainability, a guiding principle of modern environmental science. Sustainability means leaving our children and grandchildren a world as rich and full as the world we live in now. It means conserving Earth’s resources so that our descendants may enjoy them as we have. It means developing solutions that work in the long term. Sustainability requires maintaining ecological systems, because we cannot sustain human civilization without sustaining the natural systems that nourish it. We can think of our planet’s resources as a bank account. If we deplete resources, we draw down the bank account. However, we can choose instead to use the interest and leave the principal intact so that we can continue using the interest far into the future. Currently we are drawing down Earth’s natural capital, its accumulated wealth of resources. Recall (p. 23) that one research group estimates that we are withdrawing our planet’s natural capital 50% faster than it is being replenished. To live off nature’s interest—its replenishable resources—is sustainable. To draw down resources faster than they are replaced is to eat into nature’s capital—the bank account for our planet and our civilization—and we cannot get away with this for long.

Population and consumption drive environmental impact

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We modify our environment in many ways, but the steep and sudden rise in human population (Chapter 8) has amplified nearly all of our impacts. We add about 80 million people to the planet each year—that’s over 200,000 per day. The rate of population growth is now slowing, but our absolute numbers continue to increase. Our consumption of resources has risen even faster than our population. The modern rise in affluence has been a positive development for humanity, and our conversion of the planet’s natural capital has made life better for most of us so far. However, like rising population, rising per capita consumption magnifies the demands we make on our environment. The world’s citizens have not benefited equally from our overall rise in affluence. Today the 20 wealthiest nations boast over 55 times the per capita income of the 20 poorest nations— three times the gap that existed just two generations ago. The ecological footprint of the average citizen of a developed nation such as the United States is considerably larger than that of the average resident of a developing country (FIGURE 1.12). Within the United States, the richest 10% of people claim fully half the income, and the richest 1% claim nearly a quarter of all income.

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Canada (6.4 ha)

World average (2.7 ha)

Indonesia (1.1 ha)

Haiti (0.6 ha)

China (2.1 ha)

France (4.9 ha)

Israel (4.0 ha)

India (0.9 ha)

Rwanda (0.7 ha)

Figure 1.12 The citizens of some nations have much larger ecological footprints than the citizens of others. Ecological footprints for average citizens of several nations are shown, along with the world’s average per capita footprint of 2.7 hectares. One hectare (ha) = 2.47 acres. Data from Global Footprint Network, in: WWF, 2012. Living planet report 2012. WWF International, Gland, Switzerland.

Which nation has the largest footprint, and how many times larger is it than that of the nation with the smallest footprint?

WEIGHING THE ISSUES ECOLOGICAL FOOTPRINTS What do you think accounts for the variation in sizes of per capita ecological footprints among societies? Do you feel that nations with larger footprints have a moral obligation to reduce their environmental impact, so as to leave more resources available for nations with smaller footprints? Why or why not?

Our dramatic growth in population and consumption is intensifying the many environmental impacts we examine in this book, including erosion and other impacts from agriculture (Chapters 9 and 10), deforestation (Chapter 12), toxic substances (Chapter 14), fresh water depletion (Chapter 15), fisheries declines (Chapter 16), air and water pollution (Chapters 15–17), waste generation (Chapter 22), mineral extraction and mining impacts (Chapter 23), and of course, global climate change (Chapter 18). These impacts degrade our health and quality of life, and they alter the ecosystems and

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Human Influence Index High

Low

agriculture and other land uses all influence terrestrial ecosystems. A U.S. map summarizing these influences shows that we live in a highly modified environment and suggests we would be wise to carefully nurture natural systems and manage remaining resources. Used by permission of the Center for International Earth Science Information Network (CIESIN), The Earth Institute, Columbia University. © 2012.

Can you find where you live on the map? Do the ecosystems in your area experience a more-thanaverage, less-than-average, or average amount of human influence? What human impacts do you think most affect natural systems in your region?

­landscapes in which we live (FIGURE 1.13). They are also driving the loss of Earth’s biodiversity (Chapter 11)—perhaps our greatest problem, because extinction is irreversible. Once a species becomes extinct, it is lost forever. The most comprehensive scientific assessment of the condition of the world’s ecological systems and their capacity to continue supporting our civilization was completed in 2005, when over 2000 leading environmental scientists from nearly 100 nations completed the Millennium Ecosystem Assessment (TABLE 1.1). The Millennium Ecosystem Assessment makes clear that our degradation of environmental systems is having negative impacts on all of us, but that with care and diligence we can still turn many of these trends around.

Our energy choices will influence our future enormously Our reliance on fossil fuels to power our civilization has intensified virtually every impact we exert on our environment, from habitat alteration to air pollution to climate change. Fossil fuels have also helped to bring us the material affluence we enjoy. By exploiting the richly concentrated energy in coal, oil, and natural gas, we have been able to power the machinery of the industrial revolution, produce the chemicals that boost agricultural yields, run the vehicles and transportation networks of our mobile society, and manufacture and distribute our countless consumer products. The lifestyles we lead today are a direct result of the availability of fossil fuels (Chapter 19).

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However, in extracting coal, oil, and natural gas, we are splurging on a one-time bonanza, for these fuels are nonrenewable and in finite supply. Scientists calculate that we have depleted roughly half the world’s conventional oil supplies and that a crisis could hit once supply begins to decline while demand continues to rise (pp. 550–551). How we handle future fossil fuel shortages will greatly influence the nature of our lives in the 21st century.   TABLE 1.1  M  ain Findings of the Millennium Ecosystem Assessment •

 ver the past 50 years, people have altered ecosystems O more rapidly and extensively than ever, largely to meet growing demands for food, fresh water, timber, fiber, and fuel. This has caused a substantial and largely irreversible loss in the diversity of life on Earth.

•

 hanges to ecosystems have contributed to substantial C net gains in human well-being and economic development. However, these gains have been achieved at growing costs, including the degradation of ecosystems and the services they provide and, for some people, the worsening of poverty.

•

 his degradation could grow significantly worse during the T first half of this century.

•

 e can reverse the degradation of ecosystems while meetW ing increasing demands for their services, but doing so will require that we significantly modify many policies, institutions, and practices.

Adapted from Millennium Ecosystem Assessment, 2005. Ecosystems and human well-being: biodiversity synthesis. World Resources Institute, Washington, DC.

C H A P T E R 1 • S C I E N C E A N D S U S TA I N A B I L I T Y: A N I N T R O D U C T I O N T O E N V I R O N M E N TA L S C I E N C E

Figure 1.13 Human settlement, roads and transportation networks, nighttime light pollution, and

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Figure 1.14 We can develop clean and renewable energy sources for our sustainable use. Just as a flowering plant gathers energy from the sun, rooftop panels like these harness solar energy.

Sustainable solutions abound Humanity’s challenge is to develop solutions that enhance our quality of life while protecting and restoring the environment that supports us. Fortunately, many workable solutions are at hand. For instance: • Renewable energy sources (Chapters 20 and 21) are being developed to replace fossil fuels (FIGURE 1.14), and energy-efficiency efforts are gaining ground. • In response to agricultural impacts, scientists and others have developed and promoted soil conservation, highefficiency irrigation, and organic agriculture (Chapters 9 and 10). • Laws and new technologies have reduced the pollution emitted by industry and automobiles in wealthier countries (Chapters 15–17). • Conservation biologists are helping to protect habitat and safeguard endangered species (Chapter 11). • Recycling is helping us conserve resources and alleviate waste disposal problems (Chapter 22). • Governments, businesses, and individuals are taking steps to reduce emissions of the greenhouse gases that drive climate change (Chapter 18). These are a few of the many efforts we will examine while exploring sustainable solutions in the course of this book.

Students are promoting solutions on campus

34

As a college student, you can help to design and implement sustainable solutions on your own campus. Proponents of campus sustainability seek ways to help colleges and universities reduce their ecological footprints. Student-run organizations often play a key role in initiating recycling programs, finding

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ways to reduce energy use, and agitating for new courses or majors in environmental science or environmental studies. We tend to think of colleges and universities as enlightened and progressive institutions that benefit society. This may be true, but colleges and universities are also centers of lavish resource consumption. Institutions of higher education feature extensive infrastructure including classrooms, offices, research labs, residential housing, dining establishments, sports arenas, vehicle fleets, and road networks. The 4500 campuses in the United States interact with thousands of businesses and spend $400 billion each year on products and services. The ecological footprint of a typical college or university is substantial, and together these institutions generate perhaps 2% of U.S. carbon emissions. Reducing the size of this footprint is challenging. Colleges and universities tend to be bastions of tradition, where institutional habits are deeply ingrained and where bureaucratic inertia can block the best intentions for positive change. Nonetheless, faculty, staff, administrators, and students are progressing on a variety of fronts to make the operations of educational institutions more sustainable (FIGURE 1.15). Students are often the ones who initiate change, although support from faculty, staff, and administrators is crucial for success. Students often feel freest to express themselves. Students also arrive on campus with new ideas and perspectives, and they generally are less attached to traditional ways of doing things.

Campus sustainability efforts are diverse Students are advancing sustainability efforts on their campuses by promoting efficient transportation options, running recycling programs, planting trees and restoring native plants, growing organic gardens, and fostering sustainable dining halls. They are working with faculty and administrators to improve energy efficiency and water conservation in campus buildings and to ensure that new buildings meet certification guidelines for sustainable construction. To help address global climate change, students are urging their institutions to reduce greenhouse gas emissions and to use and invest in renewable energy. In response, nearly 700 university presidents have signed onto the American College and University Presidents’ Climate Commitment: a public pledge to inventory emissions, set target dates and milestones for becoming carbon-neutral, take immediate steps to lower emissions, and integrate sustainability into the curriculum. Students who take the initiative to promote sustainable practices on their campuses accomplish several things at once: • Students can truly make a difference by reducing the ecological footprint of a campus. The consumptive impact of educating, feeding, and housing hundreds or thousands of students is immense, so considerable opportunity exists for reducing the waste of resources. • Students who act to advance campus sustainability can serve as models for their peers, helping to make them aware that they, too, can address problems.

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(b) Installing energy-efficient CFLs at Dickinson

(c) Recycling at Davidson

(d) Collecting electronic waste at UT Austin

Figure 1.15 Students are helping to make their campuses more sustainable in all kinds of ways.

• Students can learn and grow as a result. Colleges and universities are microcosms of society at large, and the challenges, successes, and failures encountered while working with others as part of a team can serve as valuable preparation for similar efforts in our broader society. In our final chapter and throughout this book you will encounter examples of campus sustainability efforts. Should you wish to pursue such efforts on your own campus, information and links available in the Selected Sources and References point you toward organizations and resources that can help. You will also see that the general concept of sustainability is infused throughout this book with one issue after another, and that the vital concept of sustainable development is tackled in Chapter 6. Our final chapter (Chapter 24) rounds out our discussion by presenting a summary of approaches to sustainability—on college and university campuses and in the world at large. All along the way, we will explore a wide array of issues in our far-reaching search for sustainable solutions.

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Environmental science prepares you for the future By taking a course in environmental science, you are helping to prepare yourself for a lifetime in a world increasingly dominated by concerns over sustainability. As society’s concerns have evolved, colleges and universities have adapted their ­academic curricula. The course for which you are using this book right now likely did not exist a generation ago. As our society comes to appreciate the looming challenges of creating a sustainable future, colleges and universities are attempting to better train students to confront these challenges. Still, the latest nationwide survey of campus sustainability efforts (in 2008) found that the percentage of American colleges and universities that require all students to take at least one course related to environmental science or sustainability had actually decreased, from 8% in 2001 to just 4% in 2008. At most schools, fewer than half of

C H A P T E R 1 • S C I E N C E A N D S U S TA I N A B I L I T Y: A N I N T R O D U C T I O N T O E N V I R O N M E N TA L S C I E N C E

(a) Urging divestment from fossil fuels

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students take even a single course on the basic functions of Earth’s natural systems, and still fewer take courses on the links between human activity and sustainability. As a result, the report stated, “students are slightly less likely to be environmentally literate when they graduate in 2008 than in 2001.” This surprising finding suggests that students like you are in a privileged minority, benefiting from a valuable education that most of your peers are missing. As a result of your environmental science course, you will come away from your college years with a better understanding of how the world works. You will be better qualified for tomorrow’s green-collar job opportunities. And you will be ­better ­prepared to navigate the many challenges of creating a sustainable future.

Conclusion Finding effective ways of living peacefully, healthfully, and sustainably on our diverse and complex planet will require a thorough scientific understanding of both natural and social systems. Environmental science helps us understand our intricate relationship with our environment and informs our attempts to solve and prevent environmental problems. Many of the trends detailed in this book may cause us worry, but others give us reason for optimism. Solving environmental problems can move us toward health, longevity, peace, and prosperity. Science in general, and environmental science in particular, can aid us in our efforts to develop balanced and workable solutions to the many challenges we face today and to create a better world for ourselves and our children.

Reviewing Objectives You should now be able to: Define the term environment and describe the field of environmental science

• Environmental science employs approaches and insights from numerous disciplines in the natural sciences and social sciences. (p. 26)

• Our environment consists of everything around us, including living and nonliving things. (p. 21)

• Environmental scientists are not advocates for environmental causes; instead, they study scientific issues objectively. (p. 27)

• People are part of the environment and are not separate from nature. (p. 21)

Understand the scientific method and the process of

• Environmental science is the study of how the natural world works, how our environment affects us, and how we affect our environment. (p. 21)

• Science is a process of using observations to test ideas. (pp. 27–28)

Explain the importance of natural resources and ecosystem services to our lives

• Some resources are inexhaustible or perpetually renewable, others are nonrenewable, and still others are renewable if we do not overexploit them. (pp. 21–22)

science

• The scientific method consists of making observations, formulating questions, stating a hypothesis, generating predictions, testing predictions, and analyzing results. (pp. 28–30) • There are different ways to test questions scientifically (for example, with manipulative experiments to determine causation or with natural experiments and correlation). (p. 30)

• Ecosystem services are benefits we receive from the processes and normal functioning of natural systems. (p. 21)

• Scientific research occurs within a larger process that includes peer review, journal publication, and interaction with colleagues. (pp. 30–31)

• Resources and ecosystem services are essential to human life and civilization, yet we are depleting and degrading many of them. (p. 21)

• Science goes through paradigm shifts. This openness to change is what gives science its strength. (p. 31)

Discuss the consequences of population growth and resource consumption

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Characterize the nature of environmental science

Diagnose and illustrate some of the pressures on the global environment

• Rapid growth of the human population magnifies our environmental impacts. (p. 22)

• Rising human population and intensifying per capita consumption magnify human impacts on the environment. (p. 32)

• An ecological footprint quantifies a person’s or nation’s resource consumption in terms of area of biologically productive land and water. (pp. 22–23)

• Human activities are having diverse impacts, including resource depletion, air and water pollution, climate change, habitat destruction, and biodiversity loss. (pp. 32–33)

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• Fossil fuel use drives many of our impacts. Replacing fossil fuels with clean renewable energy can reduce these impacts. (pp. 33–34) • We are developing sustainable solutions that promote our quality of life while protecting and restoring our environment. (p. 34)

• Many college students are taking action to promote sustainable solutions on their campuses, ranging from recycling to energy efficiency to water conservation to transportation, and more. (pp. 34–35) • Your environmental science course will help prepare you for the challenges and opportunities in a world striving for a sustainable future. (pp. 35–36)

Articulate the concept of sustainability and describe campus sustainability efforts

• Sustainability means living within our planet’s means, such that Earth’s resources can sustain us—and all life—for the future. (p. 32)

Testing Your Comprehension 6. Describe the scientific method. What is its typical sequence of steps? 7. What is a natural experiment? Name the challenges of performing a natural experiment as opposed to a manipulative experiment? 8. What needs to occur before a researcher’s results are published? Why is this process important? 9. Give examples of three major environmental problems in the world today, along with their causes. How are these problems interrelated? Can you name a potential solution for each? 0. What qualities are present in a sustainable enterprise? 1

Seeking Solutions 1. Many resources are renewable if we use them in moderation but can become nonrenewable if we overexploit them. Order the following resources on a continuum of renewability (see Figure 1.1), from most renewable to least renewable: soils, timber, fresh water, food crops, and biodiversity. What factors influenced your choices? For each resource, what might constitute overexploitation, and what might constitute sustainable use? 2. What do you think is the lesson of Easter Island? What more would you like to learn or understand about this island and its people? What similarities do you perceive between the history of Easter Island and the modern history of our society? What differences do you see between their predicament and ours? 3. What environmental problem do you feel most acutely yourself? Do you think there are people in the world who do not view your issue as a problem? Who might they be, and why might they take a different view? 4. If the human population were to stabilize tomorrow and never reach 8 billion people, would that solve our

M01_WITH7428_05_SE_C01.indd 37

environmental problems? Which types of problems might get better, and which might become worse? 5. Find out what sustainability efforts are being made on your campus. What results have these efforts produced so far? What further efforts would you like to see pursued on your campus? Do you foresee any obstacles to these efforts? How could these obstacles be overcome? How could you become involved? 6. THINK IT THROUGH You have become head of a major funding agency that disburses funding to scientists pursuing research in environmental science. You must give your staff several priorities to determine what types of scientific research to fund. What environmental problems would you most like to see addressed with research? Describe the research you think would need to be completed so that workable solutions to these problems could be developed. What else, beyond scientific research, might be needed to develop sustainable solutions?

C H A P T E R 1 • S C I E N C E A N D S U S TA I N A B I L I T Y: A N I N T R O D U C T I O N T O E N V I R O N M E N TA L S C I E N C E

1. What do renewable resources and nonrenewable resources have in common? How are they different? Identify two renewable and two nonrenewable resources. 2. How and why did the agricultural revolution affect human population size? How and why did the industrial revolution affect human population size? Explain what benefits and what environmental impacts have resulted. 3. What is an ecological footprint? Explain what is meant by the term overshoot. 4. Define environmental science and environmentalism. How are they different? Explain the similarities between the two. 5. What are the two meanings of science? Name three applications of science.

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Calculating Ecological Footprints Mathis Wackernagel and his colleagues at the Global Footprint Network have continually been refining the method of calculating ecological footprints—the amount of biologically productive land and water required to produce the energy and natural resources we consume and to absorb the wastes we generate. According to their most recent data, there are 1.8 hectares (4.4 acres) available for each

Nation Bangladesh

p­ erson in the world, yet we use on average 2.7 ha (6.7 acres) per person, creating a global ecological deficit, or overshoot (p. 23), of 50%. Compare the ecological footprints of each nation listed in the table. Calculate their proportional relationships to the world population’s average ecological footprint and to the area available globally to meet our ecological demands.

Ecological footprint (hectares per person)

Proportion relative to world average footprint

Proportion relative to world area available

0.7

0.3 (0.7 ÷ 2.7)

0.4 (0.7 ÷ 1.8)

Tanzania

1.2

 

 

Colombia

1.8

 

 

Thailand

2.4

 

 

Mexico

3.3

 

 

Sweden

5.7

 

 

United States

7.2

 

 

1.0 (2.7 ÷ 2.7)

1.5 (2.7 ÷ 1.8)

World average Your personal footprint (see Question 4)

2.7  

 

 

Data from Global Footprint Network, in: WWF, 2012. Living planet report 2012. WWF International, Gland, Switzerland.

1. Why do you think the ecological footprint for people in Bangladesh is so small? 2. Why is it so large for people in the United States? 3. Based on the data in the table, how do you think average per capita income affects ecological footprints? 4. Go to an online footprint calculator such as the one at http://www.myfootprint.org or http://www.footprintnetwork.org/en/index.php/GFN/page/personal_footprint

STUDENTS Go to MasteringEnvironmentalScience for assignments, the etext, and the Study Area with practice tests, videos, current events, and activities.

and take the test to determine your own personal ecological footprint. Enter the value you obtain in the table and calculate the other values as you did for each nation. How does your footprint compare to those of the average person in the United States? How does it compare to that of people from other nations? Name three actions you could take to reduce your footprint. (Note: Save this number— you will calculate your footprint again in Chapter 24 at the end of your course!)

INSTRUCTORS Go to MasteringEnvironmentalScience for automatically graded activities, current events, videos, and reading questions that you can assign to your students, plus Instructor Resources.

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2

Rescue workers in northeastern Japan

Earth’s Physical ­Systems: Matter, Energy, and ­Geology Upon completing this chapter, you will be able to: Explain the fundamentals of matter and chemistry and apply them to real-world situations

Explain how plate tectonics and the rock cycle shape the landscape around us and the earth beneath our feet

Differentiate among forms of energy and explain the basics of energy flow

List major types of geologic hazards and describe ways to mitigate their impacts

Distinguish photosynthesis, cellular respiration, and chemosynthesis and summarize their importance to living things

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CEN C entral T RA L CA Case S E S Ttudy U DY

The Tohoku Earthquake: Has It Shaken the World’s Trust in Nuclear Power? “This used to be one of the best places for a business. I’m amazed at how little is left.”

NORTH KOREA Sea of Japan (East Sea) Fukushima Daiichi SOUTH KOREA

JAPAN

North Pacific Ocean

40

At 2:46 p.m. on March 11, 2011, the land along the northeastern coast of the Japanese island of Honshu began to shake violently—and continued to shake for six minutes. These tremors were caused when a large section of the seafloor along a fault line 125 km (77 mi) offshore suddenly lurched, releasing huge amounts of energy through the crust and generating an earthquake of magnitude 9.0 on the Richter scale (a scale used to measure the strength of earthquakes). Little did anyone know at the time that this quake would initiate a series of events that would affect not only Japan, but also the future of nuclear power around the world. The Tohoku earthquake, as it was later named, was not the first major earthquake to strike Japan. The city of Kobe experienced substantial damage from a quake in 1995 that claimed over 5500 lives. And in 1923, an earthquake devastated the ­cities of Tokyo and Yokohama, resulting in over 142,000 deaths. Losses of life and property from the Tohoku quake were far less extensive than the losses from these earlier events, thanks to new stringent building codes that enable buildings to resist crumbling and toppling over during earthquakes. But even when the earth stopped shaking, the residents of northeastern Japan knew that further danger might still await them—from a tsunami. A tsunami (“harbor wave” in English) is a powerful surge of seawater generated when an offshore earthquake displaces large volumes of rocks and sediment on the ocean bottom, suddenly pushing the overlying ocean water upward. This upward movement of water creates waves that speed outward from the earthquake site in all directions. These waves are hardly noticeable at sea, but can rear up to staggering heights when they enter the shallow waters near shore and can sweep inland with great force. The fear of a tsunami was well founded,

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—Takahiro Chiba, surveying the devastated downtown area of Ishinomaki, Japan, where his family’s sushi restaurant was located

“Fukushima should not just contain lessons for Japan, but for all 31 countries with nuclear power.” —Tatsujiro Suzuki, Vice-chairman, Japan Atomic Energy Commission

as strong ocean surges followed the 1923 Tokyo–Yokohama earthquake, pushing walls of debris in front of them and drowning victims still trapped in the wreckage from the earthquake. The Japanese had built seawalls to protect against tsunamis, but the Tohoku quake caused the island of Honshu to sink, lowering the height of the seawalls by up to 2 m (6.5 ft) in some locations. Waves reaching up to 15 m (49 ft) in height then overwhelmed these defenses (Figure 2.1). The raging water swept up to 9.6 km (6 mi) inland, scoured buildings from their foundations, and

Figure 2.1 Tsunami waves overtop a seawall following the Tohoku earthquake in 2011. The tsunami caused a greater loss of life and property than the earthquake that generated it and led to a meltdown at the Fukushima Daiichi nuclear power plant.

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inundated towns, villages, and productive agricultural land. As the water’s energy faded, it receded, carrying structural debris, vehicles, livestock, and human bodies out to sea. When the tsunami overtopped the 5.7-m (19-ft) seawall protecting the Fukushima Daiichi nuclear power plant, it flooded the diesel-powered emergency generators responsible for circulating water to cool the plant’s nuclear reactors. With the local electrical grid knocked out by the earthquake and the backup generators off-line, the nuclear fuel in the cores of the three active reactors at the plant began to overheat. The water that normally kept the nuclear fuel submerged within the reactor cores boiled off, exposing the nuclear material to the air and further elevating temperatures inside the cores. As the overheated nuclear fuel melted (called a nuclear meltdown), chemical reactions within the reactors generated hydrogen gas, which set off explosions in each of the three reactor buildings, releasing radioactive material into the air. As events worsened over several tense days, Japanese authorities became desperate to cool the reactors, contain the radioactive emissions, and prevent a full-blown catastrophe that could render large portions of their nation uninhabitable. They sent in teams of engineers and soldiers who risked their lives amid the radiation and flooded the reactor cores with seawater pumped in from the ocean. The 1–2–3 punch of the earthquake–tsunami–nuclear accident left over 19,000 people dead or missing and caused $300 billion in material damage. Around 340,000 people were displaced

The tragic events in northeastern Japan were the result of largescale forces generated by the powerful geological processes that shape the surface of our planet. Environmental scientists regularly study these types of processes to understand how our planet works. Because all large-scale processes are made up of small-scale components, however, environmental science— the broadest of scientific fields—must also study small-scale phenomena. At the smallest scale, an understanding of matter itself helps us to fully appreciate all the processes of our world. All material in the universe that has mass and occupies space—solid, liquid, and gas alike—is called matter. In our quick tour of matter in the pages that follow, we examine types of matter and some of the important ways they interact—phenomena that together we term chemistry. Once you examine any environmental issue, you will likely discover chemistry playing a central role. Knowledge of chemistry is crucial for understanding how gases such as carbon dioxide and methane contribute to global climate change, how pollutants such as sulfur dioxide and nitric oxide cause acid rain, and how pesticides and other compounds we release into the environment affect the health of wildlife and people. Such knowledge is central, too, in understanding water pollution and wastewater treatment, hazardous waste and its cleanup and disposal, atmospheric ozone depletion, and most energy issues. Moreover, c­ountless applications of chemistry can help us address these environmental problems.

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Matter is conserved To appreciate the chemistry involved in environmental science, we must begin with a grasp of the fundamentals. Matter may be transformed from one type of substance into others, but it cannot be created or destroyed. This principle is referred to as the law of conservation of matter. In environmental science, this principle helps us understand that the amount of matter stays constant as it is recycled in ecosystems and nutrient cycles (p. 135). It also makes it clear to us that we cannot simply wish away “undesirable” matter, such as nuclear waste and toxic pollutants. Since harmful substances like these can’t be destroyed, we must take prudent steps to mitigate their impacts on the environment.

Atoms and elements are chemical building blocks The nuclear reactor at Fukushima used uranium to power its reactors, and uranium is an example of an element. An element is a fundamental type of matter, a chemical substance with a given set of properties that cannot be broken down into substances with other properties. Chemists currently recognize 92 elements occurring in nature, as well as more than 20 others that they have created in the lab. Elements especially ­abundant on our planet include hydrogen (in water), oxygen (in the air), silicon (in Earth’s crust), nitrogen (in the air), and carbon (in living organisms) (Table 2.1). Each element is assigned an abbreviation, or chemical symbol (for instance,

C H A P T E R 2 • E art h ’ s P h y s i cal ­S y s te m s : Matter , E ner g y , an d ­Ge o l o g y

Matter, Chemistry, and the Environment

from their homes, including 100,000 people from towns near the Fukushima Daiichi plant where radioactive f­allout contaminated the soil to unsafe levels. A 20-km (12-mi) area around the Fukushima Daiichi plant has been permanently evacuated, and the full extent of nuclear contamination is still being determined (see The Science behind the Story, pp. 44–45). Some of the greatest concerns center on contaminated food and water, so domestically produced crops and seafood will require testing for radiation for years to come. Full recovery from these events is expected to take decades. One of the longest-lasting legacies of these events may be the impact on the future of nuclear power in Japan and around the world. The Japanese government had championed a view that nuclear power was perfectly safe, but the events at Fukushima have shaken public support for nuclear power in Japan. In the summer of 2012, over 100,000 people marched in Tokyo to protest the restarting of nuclear reactors that had been shut down after the Tohoku quake, and public opinion surveys found 70% of Japanese wished for their nation to rely less on nuclear power. In North America and Europe, the events at Fukushima Daiichi caused a public already skeptical of the safety of nuclear power to become further wary of its use. But with the challenges facing us in climate change (Chapter 18), many energy analysts, scientists, and policymakers caution that we should not abandon a carbon-free source of energy like nuclear power, but rather refocus efforts on maximizing its safety. Whatever the eventual outcome of these analyses, the events of March 11, 2011, will not soon be forgotten—in Japan or elsewhere.

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Table 2.1 Earth’s Most Abundant Chemical Elements, by Mass Earth’s crust

Oceans

Oxygen (O)

49.5%

Silicon (Si) Aluminum (Al)

Air

Oxygen (O)

88.3%

25.7%

Hydrogen (H)

7.4%

Chlorine (Cl)

78.1%

11.0%

Oxygen (O)

21.0%

1.9%

Argon (Ar)

0.9%

Iron (Fe)

4.7%

Sodium (Na)

1.1%

Other

Calcium (Ca)

3.6%

Magnesium (Mg)

0.1%

 

Sodium (Na)

2.8%

Sulfur (S)

Potassium (K)

2.6%

Calcium (Ca)

Oxygen (O)

65.0%

Carbon (C)

18.5%

Hydrogen (H)

100 in a million

Figure 17.19 Risks for cancer throughout the United States are mapped in the EPA’s most recent national-scale assessment of toxic air pollutants. Darker colors reflect higher risk. At least 80 toxic air pollutants are carcinogens, including formaldehyde, benzene, naphthalene, and others. Geographic patterns for non-cancerous respiratory ailments are similar. Data from U.S. EPA, 2011. 2005 National-Scale Air Toxics Assessment.

What is the cancer rate due to toxic pollutants in the location where you live?

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Industrializing nations are suffering increasing air pollution Although the United States and other industrialized nations have improved their air quality, outdoor air pollution is growing worse in many industrializing countries. In these societies, proliferating factories and power plants are emitting more pollutants as governments encourage economic growth. Additionally, more citizens own and drive automobiles. At the same time, most people continue to burn traditional sources of fuel, such as wood, charcoal, and coal, for cooking and home heating. Mexico embodies these trends, and despite the progress in its capital, residents of Mexico City and many other Mexican

M17_WITH7428_05_SE_C17.indd 481

Figure 17.20 Air quality is poor in cities of today’s developing nations. At Tiananmen Square in Beijing, China, children don face masks during the “airpocalypse” that gripped the city in 2013.

cities and towns suffer a variety of health impacts from heavily polluted air (see THE SCIENCE BEHIND THE STORY, pp. 484–485). Altogether across the world, the World Health Organization (WHO) estimates that outdoor air pollution in cities causes 3.2 million premature deaths each year. The people of China suffer some of the world’s worst air pollution. China has fueled its rapid industrial development with its abundant reserves of coal, the most-polluting fossil fuel. Power plants and factories have sprung up across the nation, often using outdated, inefficient, heavily polluting technology because it is cheaper and quicker to build. Car ownership is skyrocketing; in the capital of Beijing alone 1500 new cars hit the streets each day. As a result, in many Chinese cities, the haze is often too thick for people to see the sun. In Beijing in January–February 2013, smog became so severe that airplane flights were cancelled and people wore face masks to breathe (Figure 17.20). Levels of particulate matter were literally off the charts; a pollution monitor atop the U.S. Embassy designed to measure air quality on an index from 0 to 500 detected record-breaking readings up to 755. During this so-called airpocalypse, a fire at a factory went unnoticed for three hours because the smog was so thick that no one could see the smoke from the fire! Countless thousands of people suffered ill health as the pollution soared 30 times past the WHO’s safe limits. Conditions were so bad that the government and the official state media were finally forced to admit the problem and begin a public discussion about solutions. Across China, the health impacts of air pollution day in and day out are enormous. A 2013 international research report blamed outdoor air pollution for 1.2 million premature deaths in China each year. Winds carry some of China’s pollution to neighboring nations. Some even travels across the Pacific Ocean to Los Angeles and other western U.S. cities.

C H A P T E R 1 7 • A t m o s pher i c Sc i e n ce , A i r Q u a l i t y , a n d P o l l u t i o n C o n tr o l

utilities generate much of these emissions, but all of us contribute by living carbon-intensive lifestyles. Each year the average U.S. vehicle driver releases close to 6 metric tons of carbon dioxide, 275 kg (605 lb) of methane, and 19 kg (41 lb) of nitrous oxide, all of them greenhouse gases that drive climate change. In 2007 the U.S. Supreme Court ruled that the EPA has legal authority under the Clean Air Act to regulate carbon dioxide and other greenhouse gases as air pollutants. President Barack Obama voiced his preference that Congress address greenhouse gas emissions through bipartisan legislation. When Congress failed to pass climate change legislation, Obama instructed EPA Administrator Lisa Jackson to begin developing regulations to address greenhouse gas emissions. In 2011, the EPA introduced moderate carbon emission standards for cars and light trucks, and in 2012 it announced that it would limit carbon emissions for new coal-fired power plants and cement factories (but not existing ones). The EPA decided to phase in regulations gradually, beginning with the largest emitters. The coal-mining and petrochemical industries objected, and these industries and several states sued to stop the regulations. A court of appeals unanimously upheld the EPA regulations in 2012. The automotive industry supported the regulations. U.S. automakers had already begun investing in fuel-efficient vehicles, and were glad to have one set of federal emissions standards, so as not to have to worry about meeting many differing state standards. The public also voiced strong support; 2.1 million Americans sent comments to the EPA in favor of the regulations—a record number of public comments for any federal regulation. The EPA will no doubt continue to face formidable political opposition from emitting industries and from policymakers who fear that regulations will hamper economic growth. Yet if we were able to reduce emissions of other major pollutants sharply since 1970 while advancing our economy, we can hope to achieve similar results in reducing greenhouse gas emissions. Indeed, although U.S. carbon dioxide emissions rose by 51% from 1970 to 2007, they decreased by 12% from 2007 to 2012. This decrease in emissions resulted partly from reduced energy use during a time of economic recession, but also from a shift from coal to cleaner-burning natural gas, and from improved fuel-efficiency in automobiles and other technologies.

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China’s government is now striving to reduce pollution. It has closed down some heavily polluting factories and mines, phased out some subsidies for polluting industries, installed pollution controls in power plants, and encouraged the development of wind, solar, and nuclear power. It subsidizes people to buy efficient electric heaters for their homes to replace dirty, inefficient coal stoves. It has mandated cleaner formulations for gasoline and diesel and has raised standards for fuel efficiency and emissions for cars above what the United States requires. In Beijing, mass transit is being expanded, many buses run on natural gas, and heavily polluting vehicles are restricted from operating in the central city. China is also aggressively developing cleaner wind, solar, and nuclear power to substitute for power produced by burning coal. The nation likely will need to accelerate such steps, as its 1.35 billion citizens are becoming increasingly fed up with air pollution. Pollution from autos, industry, agriculture, and woodburning stoves in China, India, and other industrializing nations of Asia has resulted in a persistent 2-mile-thick layer of pollution that hangs over southern Asia throughout the dry season each December through April. Dubbed the Asian Brown Cloud, or Atmospheric Brown Cloud, this massive layer

of brownish haze is estimated to reduce the sunlight reaching Earth’s surface in southern Asia by 10–20%; promote flooding in some areas and drought in others by altering the monsoon; decrease rice productivity by 5–10%; speed the melting of Himalayan glaciers by depositing dark soot that absorbs sunlight; and contribute to many thousands of deaths each year.

Smog poses health risks Let’s now examine one of our most prevalent types of air pollution: smog. Smog is an unhealthy mixture of air pollutants that often forms over urban areas as a result of fossil fuel combustion. Since the onset of the industrial revolution, cities have suffered a type of smog known as industrial smog. When coal or oil is burned, some portion is completely combusted, forming CO2; some is partially combusted, producing CO; and some remains unburned and is released as soot (particles of carbon). Moreover, coal contains contaminants such as mercury and sulfur. Sulfur reacts with oxygen to form sulfur dioxide, which can undergo a series of reactions to form sulfuric acid and ammonium sulfate (Figure 17.21a). These chemicals and others produced by further reactions, along with soot, are the main components of industrial smog.

Figure 17.21 Industrial smog results from fossil fuel combustion. When fossil fuels are burned, sulfur contaminants give rise to sulfur dioxide, which may react with atmospheric gases to produce other sulfur compounds (a). Industrial smog also consists of particulate matter, carbon monoxide, and carbon dioxide. Under certain weather conditions, industrial smog can blanket whole towns or regions, as it did in Donora, Pennsylvania (b), shown in the daytime during its deadly 1948 smog episode. Coal and oil

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(b) Donora, Pennsylvania, at midday in the 1948 smog event

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The thick and blinding “killer smog” of 1952 in London occurred when weather conditions trapped emissions from the coal used to fire the city’s industries and heat people’s homes. Sulfur dioxide and particulate matter caused most of the 4000–12,000 deaths from that episode. In the wake of this catastrophe and others, the governments of developed nations began regulating industrial emissions and have greatly reduced industrial smog. However, in industrializing regions such as China, India, and eastern Europe, coal burning and lax pollution control result in industrial smog that poses significant health risks. As we’ve seen, weather and topography play roles in smog formation. Four years before London’s killer smog, a similar event occurred in Pennsylvania in a small town named Donora (Figure 17.21b). Donora is located in a mountain valley, and one day after air had cooled during the night, the morning sun did not reach the valley floor to warm and disperse the cold air. The resulting thermal inversion trapped smog containing particulate matter emissions from a steel and wire factory. Twenty-one people died, and over 6000 people—nearly half the town—became ill. For most urban areas today, however, pollution results largely from automobile exhaust. In Mexico City, vehicles contribute 31% of volatile organic compounds, 50% of sulfur dioxide, and 82% of nitrogen oxides. Cities like Mexico City

and Los Angeles also have sunny climates. As a result, such cities suffer from a different type of smog. Photochemical smog forms when sunlight drives chemical reactions between primary pollutants and normal atmospheric compounds, producing a mix of over 100 different chemicals, tropospheric ozone often being the most abundant (Figure 17.22a). Because it also includes NO2, photochemical smog generally appears as a brownish haze (Figure 17.22b). Hot, sunny, windless days in urban areas provide perfect conditions for the formation of photochemical smog. On a typical weekday, exhaust from morning traffic releases NO and VOCs into a city’s air. Sunlight then promotes the production of ozone and other constituents of photochemical smog. Levels of photochemical pollutants in urban areas typically peak in midafternoon and can irritate people’s eyes, noses, and throats.

We can take steps to reduce smog Los Angeles’s struggle with air pollution began in 1943, when the city’s first major smog episode cut visibility to three blocks. Since then, L.A. residents have dealt with headaches, eye irritation, asthma, lung damage, and related illnesses. However, Los Angeles confronted its problem and has made great progress in clearing the air since the 1970s.

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Figure 17.22 Photochemical smog results when pollutants from automobile exhaust react with sunlight. Nitric oxide can start a chemical chain reaction (a) that produces compounds including nitrogen dioxide, nitric acid, ozone, and peroxyacyl nitrates (PANs). PANs can induce further reactions that damage living tissues. Photochemical smog is common over Mexico City (b) and many other urban areas, especially those with hilly topography or frequent inversion layers.

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The SCIENCE behind the Story Measuring the Health Impacts of Mexico City’s Air Pollution “I know I’m inhaling poison,” a 38-yearold candy vendor named Guadalupe told a reporter amid the fumes of a traffic-choked intersection in Mexico City. “But there is nothing I can do.” For as long as we have polluted our air, people have felt effects on their health. But identifying and quantifying those impacts poses a challenge for scientists. For researchers wanting to understand pollution’s health impacts—and design solutions for people like Guadalupe—what better place to go than Mexico City, long home to some of the world’s worst air pollution? A key first step is to determine what’s actually in the air. One researcher who has led the way is Mario Molina, the Nobel Prize–winning chemist who helped discover the cause of stratospheric ozone depletion and who appears in this chapter’s other Science behind the Story feature (pp. 488–489). Molina stepped away from scholarly work at U.S. universities to return to his hometown of Mexico City and help address its pollution issues. Here, in 2003 and 2006, Molina organized intensive airsampling projects involving hundreds of scientists. Nearly 200 research publications later, these efforts have clarified many aspects of the city’s pollution. For instance, one study used machines that could identify and record individual particles in real time, and found that metal-rich particulates from trash incinerators were peaking in the morning, whereas smoke from fires outside the city blew in during the afternoon. Other researchers discovered that volatile organic compounds control the amount

Dr. Lilian Calderón-Garcidueñas

of tropospheric ozone formed in smog (not nitrogen oxides, as was expected). City officials responded by targeting VOC emissions for reduction. Few people today understand Mexico City’s air pollution in more detail than Armando Retama, the city’s director of atmospheric monitoring. But he may grasp its impacts best when he leaves town. “I can breathe better. I’m not all dry. My eyes aren’t irritated. My skin doesn’t crack,” he says. “We have chronic symptoms that we aren’t aware of.” Most health impacts of urban pollution affect the respiratory system. At high altitudes like Mexico City’s, the “thin air” forces people to breathe deeply to obtain enough oxygen. This means they pull more air pollutants into their lungs than people at lower elevations. As result, respiratory problems are commonplace. Many studies have confirmed that Mexico City residents show reduced lung function in comparison with people from less-polluted areas and that respiratory problems become worse and emergency room visits become more numerous when pollution is severe. Most studies have looked at short-term exposure, but in 2007 a research team led by Isabelle Romieu of Mexico’s National Institute of Public Health examined the effects of growing up amid polluted air. Her team measured lung function in 3170 8-year-old

children from 39 Mexico City schools across 3 years and correlated this with their exposure to tropospheric ozone, nitrogen dioxide, and particulate matter. The children’s ability to inhale and exhale deeply improved as they matured, but children from more polluted areas lagged behind those from cleaner areas, indicating smaller, weaker lungs. Romieu and her colleagues also showed in a series of studies that the city’s pollution worsens asthma in children, particularly those with certain genetic profiles. In 2008 her team analyzed data from 200 asthmatic and healthy children and found that children in areas with more traffic and pollutants coughed, wheezed, and used medication more often. Another Mexican researcher, Lilian Calderón-Garcidueñas, has led several studies comparing chest X-ray films and medical records of Mexico City children with those of similar children from nonpolluted locations. Her team found hyperinflation and other problems with the lungs of the Mexico City youth. Mexico City children also reported many respiratory problems whereas rural children did not (FIGURE 1). Air pollution harms the heart and the cardiovascular system, too. Multiple recent studies reveal that pollution can affect heart rate, blood pressure, blood clotting, blood vessels, and atherosclerosis. Epidemiological studies (pp. 393–394) show that pollution correlates with emergency room admissions for heart attacks, chest pain, and heart failure, as well as death from heart-related causes. Part of the reason smog impacts the cardiovascular system is that tiny particulates can work their way into the bloodstream, causing the heart to reduce blood flow or go out of rhythm. Even young people are at risk. One Mexican research team analyzed the hearts of 21 people from

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Figure 1 Most Mexico City children show respiratory symptoms from air pollution. Similar children from less-polluted areas outside Mexico City show none of these conditions. Data from Calderónin children exposed to urban pollution. Pediatric Pulmonology 36: 148–161.

Mexico City who had died at an early age. They found that pollution exacts a toll before the age of 18 and that tiny bits of dead bacteria that cling to pollutant particles are part of the problem. The heart mounts an inflammatory response to try to repel the bacteria-laden particles, but because the pollution is persistent, the inflammation becomes chronic and stresses the heart. Recent research also shows that air pollution affects children’s brains, sometimes leaving damage in brain tissue that is similar to that seen in Alzheimer’s disease. In one study using brain scans, Calderón-Garcidueñas and her colleagues found that 56% of Mexico City youth had lesions on the brain’s prefrontal cortex, whereas fewer than 8% did in a region with clean air. Studies elsewhere, from Italy to Boston, are finding similar results. In 2011, Calderón-Garcidueñas’s team compared 20 children aged

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Figure 2 Rates of (a) death and (b) infant mortality each increase in Mexico City with the intensity of air pollution. Data from (a) Borja-Aburto, V., et al., 1997. Ozone, suspended particulates, and daily mortality in Mexico City. Am. J. Epidemiology 145: 258–268; and (b) Loomis, D., et al., 1999. Air pollution and infant mortality in Mexico City. Epidemiology 10: 118–123.

The extensive research showing a diversity of health impacts from air pollution in Mexico City has caught the attention of city leaders. These scientific findings have helped push them to work hard toward cleaning up their city’s air.

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Garcidueñas, L., et al., 2003. Respiratory damage

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7–8 from Mexico City with 10 similar children from a Mexican city with clean air, measuring their cognitive skills and scanning their brains with magnetic resonance imagery (MRI). Results showed that the Mexico City children performed more poorly on most cognitive tests of reasoning, knowledge, and memory. The differences in cognition were consistent with differences in volume of white matter in key portions of the brain as revealed by the MRIs. Pollution even damages the sense of smell. In 2006–2008 Robyn Hudson and colleagues ran lab experiments comparing Mexico City residents with residents of a geographically similar rural region with clean air. Hudson’s team presented the subjects with various smells at different intensities. Compared with the rural residents, Mexico City residents had trouble smelling distinct and familiar scents such as orange juice and coffee. They also struggled to distinguish between the common Mexican beverages horchata and atole. The city-dwellers even had trouble noticing the stench of rotting food! The researchers attributed this to tissue damage in the noses of city-dwellers from a lifetime of exposure to pollutants. Indeed, other scientists were documenting such tissue damage with electron microscopy. All these impacts can lead to higher rates of death. Studies by a U.S. and Mexican research team in Mexico City in the late 1990s confirmed this by comparing death certificate records against air pollution measurements. The team found that death rates rose on the day of and the day after severe pollution episodes, especially in response to particulate matter (FiGURE 2a). They also found that infant mortality was significantly higher in the days following strong pollution episodes (Figure 2b).

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California took the lead among U.S. states in adopting pollution control technology and setting emissions standards for vehicles. California’s demands helped lead the auto industry to develop less-polluting cars. A 2010 study by the nonprofit group Environment California concluded that a new car today generates just 1% of the smog-forming emissions of a 1960s-era car. Because today’s cars are 99% cleaner, the air is cleaner, even with more drivers on the road. In Los Angeles, peak smog levels have decreased 60–70% since 1980 (Figure 17.23). In 2012, researchers added that VOCs in L.A.’s air had declined by 98% since 1960, even while the city’s drivers burned 2.7 times more gasoline. Today in California and 33 other states, drivers are required to have their vehicle exhaust inspected periodically. Vehicle inspection programs have cut emissions leading to photochemical smog by 30% in many of these states, helping to make the air measurably cleaner for all of us. Despite its progress, Los Angeles still suffers the worst tropospheric ozone pollution of any U.S. metropolitan area, according to 2012 rankings by the American Lung Association. L.A. residents breathe air exceeding California’s health standard for ozone on more than 130 days per year. A 2008 study calculated that air pollution in the L.A. basin and the nearby San Joaquin Valley each year caused nearly 3900 premature deaths and cost society $28 billion (due to hospital admissions, lost workdays, etc.). Many of L.A.’s sister cities across the world also struggle with photochemical smog and are working hard to develop solutions. Athens, Greece, provides its citizens incentives to replace aging vehicles and also mandates that autos with odd-numbered license plates be driven only on odd-numbered days, and those with even-numbered plates only on evennumbered days. Smog has been reduced by 30% as a result. In Tehran, Iran, vehicle inspections are required, traffic into the city center is restricted, and drivers are paid to turn in

old polluting cars for newer cleaner ones. Sulfur was reduced in diesel fuel, lead was removed from gasoline, and buses running on (cleaner-burning) natural gas hit the roads. To raise public awareness, 22 real-time pollution indicator boards were installed around the city, electronically displaying current pollutant levels. All these efforts helped reduce pollution, yet so many people were streaming into the city and buying cars that these trends overtook the government’s efforts, and pollution grew worse again after 2006. In response, officials lowered gasoline subsidies, rationed fuel, began expanding the subway system, and strengthened some previous programs. Of all the world’s cities, Mexico City is gaining attention today for its success in reducing smog—once the world’s worst—even as population, cars, and economic activity have grown. Regulations now require cars to have catalytic converters and get emissions tests. Some industrial facilities cleaned up their processes, and others were forced out. Under pressure from city leaders, the national oil company Pemex removed lead from gasoline, improved its refineries, imported cleaner gasoline, and removed pollutants from the liquefied petroleum gas that city residents use for cooking and heating. The subway system and a fleet of low-emission buses continue to be expanded today, while residents begin using new bike-sharing and car-sharing programs. As a result, since 1990 smog has been reduced by more than half, and particulate matter is down by 70%, carbon monoxide by 74%, sulfur dioxide by 86%, and lead by 95%.

Weighing the Issues Smog-Busting Solutions  Does the city you live in, or the nearest major city to you, suffer from photochemical smog or other air pollution? How is this city responding? What policies do you think it should pursue? What benefits might your city enjoy from such policies? Would they bring any problems?

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Figure 17.23 Peak levels of tropospheric ozone in the Los Angeles region have been reduced since the 1970s, thanks to public policy and improved automotive technology. Ozone pollution still violates the state health standard, however. Data from Environment California, 2010. Clean cars in California: Four decades of progress in the unfinished battle to clean up our air.

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By what percentage has Los Angeles reduced its ozone pollution since the 1970s?

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Although ozone in the troposphere is a pollutant in photochemical smog, ozone is a highly beneficial gas in the stratosphere, where it forms the ozone layer (p. 469; see Figure 17.2). In this region of the stratosphere, concentrations of ozone reach only about 12 parts per million. However, ozone molecules are so effective at absorbing incoming ultraviolet (UV) radiation from the sun that even this diffuse concentration helps to protect life on Earth’s surface from radiation’s damaging effects. One generation ago, scientists discovered that our planet’s stratospheric ozone was being depleted, posing a major threat to human health and the environment. Years of dynamic research by hundreds of scientists (see The Science behind the Story, pp. 488–489) revealed that certain airborne chemicals destroy ozone and that most of these ozone-depleting ­substances are human-made. Our subsequent campaign to halt degradation of the ozone layer stands as one of society’s most successful efforts addressing a major environmental problem.

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UV radiation

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Figure 17.24 CFCs destroy ozone in a multistep process, repeated many times. A chlorine atom released from a CFC molecule in the presence of UV radiation reacts with an ozone molecule, forming one molecule of oxygen gas and one chlorine monoxide (ClO) molecule. The oxygen atom of the ClO molecule then binds with a stray oxygen atom to form oxygen gas, leaving the chlorine atom to begin the destructive cycle anew. In this way, a single chlorine atom can destroy up to 100,000 ozone molecules.

The Antarctic ozone hole appears each spring

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Synthetic chemicals deplete stratospheric ozone

thinned ozone concentration that was soon named the ozone hole (Figure 17.25). During each Southern Hemisphere spring since then, ozone concentrations over this immense region have dipped to roughly half their historic levels. Extensive scientific detective work has revealed why seasonal ozone depletion is so severe over Antarctica (and to a lesser extent, the Arctic). During the dark and frigid Antarctic winter, temperatures in the stratosphere dip below –80°C (–112°F), enabling unusual high-altitude polar stratospheric clouds to form. Many of these icy clouds contain condensed nitric acid, which splits chlorine atoms off from compounds such as CFCs. The freed chlorine atoms accumulate in the clouds, trapped over Antarctica by wind currents that swirl in a circular polar vortex that prevents air from mixing with the rest of Earth’s atmosphere. In the Antarctic spring (starting in September), sunshine returns, and UV radiation dissipates the clouds. This releases the chlorine atoms, which begin destroying ozone. The solar radiation also catalyzes chemical reactions, speeding up ozone depletion as temperatures warm. The ozone hole lingers over Antarctica until December, when warmed air shuts down the polar vortex, allowing ozone-depleted air to diffuse away and ozone-rich air from elsewhere to stream in. The ozone hole vanishes until the following spring. By the time scientists had worked most of this out, plummeting ozone levels were becoming a serious international concern. Already worried that intensified UV exposure at Earth’s surface would lead to more skin cancer, scientists were also predicting damage to crops and to ocean phytoplankton, the base of the marine food chain.

In 1985, researchers shocked the world by announcing that stratospheric ozone levels over Antarctica in springtime had declined by nearly half in just the previous decade, leaving a

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Researchers identifying ozone-depleting substances pinpointed primarily halocarbons—human-made compounds derived from simple hydrocarbons (p. 46), such as ethane and methane, in which hydrogen atoms are replaced by halogen atoms, such as chlorine, bromine, or fluorine. Industry was mass-producing one type of halocarbon, chlorofluorocarbons (CFCs), at a rate of a million tons per year in the early 1970s, and this rate was growing by 20% a year. CFCs were useful as refrigerants, fire extinguishers, propellants for aerosol spray cans, cleaners for electronics, and for making polystyrene foam. Because CFCs rarely reacted with other chemicals, scientists surmised that they would be harmless to people and the environment. Alas, the nonreactive qualities that made CFCs ideal for industrial purposes were having disastrous consequences for the ozone layer. Whereas reactive chemicals are broken down quickly in the troposphere, CFCs reach the stratosphere unchanged and can linger there for a century or more. In the stratosphere, intense UV radiation from the sun eventually breaks CFCs into their constituent chlorine and carbon atoms. In a two-step chemical reaction (Figure 17.24), each newly freed chlorine atom can split an ozone molecule and then ready itself to split another one. During its long residence time in the stratosphere, each free chlorine atom can catalyze the destruction of as many as 100,000 ozone molecules!

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Figure 17.25 The “ozone hole” is a vast area of thinned ozone density in the stratosphere over the Antarctic region. It has reappeared seasonally each September in recent decades. This colorized satellite imagery of Earth’s Southern Hemisphere from September 24, 2006, shows the ozone hole (purple/blue) at its maximal recorded extent to date.

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The SCIENCE behind the Story Discovering Ozone Depletion and the Substances Behind It In discovering the depletion of stratospheric ozone and coming to understand the roles of halocarbons and other substances, scientists have relied on historical records, field observations, laboratory experiments, computer models, and satellite technology. The story starts back in 1924, when British scientist G.M.B. Dobson built an instrument that measured atmospheric ozone concentrations by sampling sunlight at ground level and comparing the intensities of wavelengths that ozone does and does not absorb. By the 1970s, the Dobson ozone spectrophotometer was being used by a global network of observation stations. Meanwhile, atmospheric chemists were learning how stratospheric ozone is created and destroyed. Ozone and oxygen exist in a natural balance, with one occasionally reacting to form the other, and oxygen being far more abundant. Researchers found that certain chemicals naturally present in the atmosphere, such as hydroxyl (OH) and nitric oxide (NO), destroy ozone, keeping the ozone layer thinner than it would otherwise be. And nitrous oxide (N2O) produced by soil bacteria can make its way to the stratosphere and produce NO, Dutch meteorologist Paul Crutzen reported in 1970. This last observation was important, because some human activities, such as fertilizer application, were increasing emissions of N2O. Following Crutzen’s report, American scientists Richard Stolarski and Ralph Cicerone showed in 1973 that chlorine atoms can catalyze the destruction of ozone even more effectively than N2O can. And two

Mario Molina with F. Sherwood Rowland (L) and Paul Crutzen (R) upon their receipt of the Nobel Prize

years earlier, British scientist James Lovelock had developed an instrument to measure trace amounts of atmospheric gases and found that virtually all the chlorofluorocarbons (CFCs) humanity had produced in the past four decades were still aloft, accumulating in the stratosphere. This set the stage for the key insight. In 1974, American chemist F. Sherwood Rowland and his Mexican postdoctoral associate Mario Molina took note of all the preceding research and realized that CFCs were rising into the stratosphere, being broken down by UV radiation, and releasing chlorine atoms that ravaged the ozone layer (see Figure 17.24, p. 487). Molina and Rowland’s analysis, published in the journal Nature, earned them the 1995 Nobel prize in chemistry jointly with Crutzen. The paper also sparked discussion about setting limits on CFC emissions. Industry leaders attacked the research; DuPont’s chairman of the board reportedly called it “a science fiction tale . . . a load of rubbish . . . utter nonsense.” But measurements in the lab and in the stratosphere by

numerous researchers soon confirmed that CFCs and other halocarbons were indeed depleting ozone. In response, the United States and several other nations banned the use of CFCs in aerosol spray cans in 1978. Other uses continued, however, and by the early 1980s global production of CFCs was again on the rise. Then, a shocking new finding spurred the international community to take action. In 1985, Joseph Farman and colleagues analyzed data from a British research station in Antarctica that had been recording ozone concentrations since the 1950s. Farman’s team reported in Nature that springtime Antarctic ozone concentrations had plummeted by 40–60% just since the 1970s (FIGURE 1a). Farman’s team had beaten a group of NASA scientists to the punch. The NASA scientists were sitting on reams of data from satellites showing a global drop in ozone levels (FIGURE 1b), but they had not yet submitted their analysis for publication. But why should an “ozone hole” be localized over Antarctica, of all places? And why only in the southern spring? To

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500 Ozone depletion potential (kilotons/year)

By 1987, the mass of scientific evidence helped convince the world’s nations to agree on the Montreal Protocol, which aimed to cut CFC production in half by 1998. Within two years, further scientific evidence and computer modeling showed that more drastic measures were needed. In 1990, the Montreal Protocol was strengthened to include a complete phaseout of CFCs by 2000, in the first of several follow-up agreements. Today, amounts of ozone-depleting

determine what was causing this odd phenomenon, atmospheric chemists Susan Solomon, James Anderson, Crutzen, and others mounted expeditions in 1986 and 1987 to analyze atmospheric gases using ground stations and high-altitude balloons and aircraft. From their data they figured out how the region’s polar stratospheric clouds and circulating winds provide ideal conditions for chlorine from CFCs and other chemicals to set in motion the destruction of massive amounts of ozone.

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substances were phased out beginning in 1987, nitrous oxide (N2O; left bar) has become the primary ozonedepleting substance we emit. It has less impact than CFCs and other halocarbons did in 1987 (full-bar values), but more impact than any other substance today (lower portion of bars). Adapted

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(a) Monthly mean ozone levels at Halley, Antarctica

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(b) Global ozone readings from 5 satellites

Figure 1 Monitoring shows ozone depletion. Data from Halley, Antarctica (a), show a decrease in stratospheric ozone concentrations from the 1960s to 1990. Once ozonedepleting substances began to be phased out, ozone concentrations stopped declining. Ozone decline and stabilization are also evident globally (b), as seen in data from five satellites. Data from (a) British Antarctic Survey; and (b) NASA.

substances in the stratosphere are beginning to level off. As the ozone layer begins a longterm recovery, scientists continue their research. In 2009, a team led by A.R. Ravishankara of the National Oceanic and Atmospheric Administration determined that nitrous oxide (N2O) had now become the leading cause of ozone depletion (Figure 2). Its emissions are not regulated, so its impacts have come to surpass those that the remaining halocarbons currently exert. Ravishankara’s team points out that regulating nitrous oxide, which is also a potent greenhouse gas, would help mitigate climate change as well as speed ozone recovery.

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Ozone levels (Dobson units)

Figure 2 Since most ozone-depleting

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FAQ

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Is the ozone hole related to global ­warming?

This is a common misconception held by the public. Some people are under the impression that the depletion of stratospheric ozone helps to prevent global warming by letting heat or greenhouse gases out of the atmosphere. Other people suppose that ozone depletion worsens warming by letting heat into the atmosphere. Neither is true. Ozone depletion lets in excess ultraviolet radiation from the sun, but this does not appreciably warm or cool the atmosphere. Research published in 2011 suggested that the ozone hole may in fact affect atmospheric circulation and rainfall in the Southern Hemisphere, and perhaps researchers will discover other connections between aspects of climate change and ozone depletion. However, on the whole the two phenomena are very different and largely unrelated.

We addressed ozone depletion with the Montreal Protocol In response to the scientific concerns, international policy efforts to restrict production of CFCs bore fruit in 1987 with the Montreal Protocol. In this treaty, signatory nations (eventually numbering 196) agreed to cut CFC production in half by 1998. Five follow-up agreements deepened the cuts, advanced timetables for compliance, and addressed additional ozone-depleting substances (Figure 17.26). The substances covered by these agreements have now been mostly phased out, and industry has been able to shift to safer alternative chemicals that are inexpensive and efficient. As a result, we have evidently stopped the Antarctic ozone hole from growing worse (Figure 17.27)—a success that all humanity can celebrate.

Effective stratospheric chlorine (parts per billion)

15 Montreal 1987

No protocol

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London 1990

Copenhagen 1992 Beijing 1999 Zero emissions 2000

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2040 Year

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Figure 17.26 The Montreal Protocol reduced stratospheric ozone depletion, and follow-up agreements in London, Copenhagen, and Beijing reduced it still more. In this graph, the y-axis values give a collective measure of ozone-destructive potential from all substances. Data from Emmanuelle Bournay, UNEP/

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GRID-Arendal, http://maps.grida.no/go/graphic/effects-of-the-montreal-protocolamendment-and-their-phase-out-schedules.

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Figure 17.27 The Antarctic ozone hole grew quickly after its appearance, but phase-outs of ozone-depleting substances beginning in 1987 have halted its growth. Data from NASA, reflecting averages from 7 Sept. to 13 Oct. each year.

The ozone layer is not expected to recover completely until 2060–2075. Much of the 5 billion kg (11 billion lb) of CFCs emitted into the troposphere has yet to diffuse up into the stratosphere, so concentrations may not peak there until 2020. Because of this time lag and the long residence times of many halocarbons, we can expect many years to go by before our policies have the desired environmental effect. Indeed, it is common for there to be a time lag between our response to an environmental problem and the resolution of the problem. This is one reason scientists often argue for proactive policy guided by the precautionary principle (p. 283), rather than reactive policy that risks responding too late. One challenge in restoring the ozone layer is that nations can plead for some ozone-depleting substances to be exempt from the ban. For instance, the United States was allowed to continue using methyl bromide, a fumigant used to control pests on strawberries. Yet despite the remaining challenges, the Montreal Protocol and its follow-up amendments are widely considered our biggest success story so far in addressing a global environmental problem. The success has been attributed to several factors: 1. Informative scientific research developed rapidly, facili-

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tated by new and evolving technologies. 2. Policymakers engaged industry in helping to solve the problem. Industry became willing to develop replacement chemicals in part because patents on CFCs were running out and firms wanted to position themselves to profit from next-generation chemicals. . Implementation of the Montreal Protocol after 1987 3 followed an adaptive management approach (p. 333), adjusting strategies midstream in response to new scientific data, technological advances, or economic figures. Because of its success in addressing ozone depletion, the Montreal Protocol is widely viewed as a model for international cooperation in addressing other pressing global problems, from biodiversity loss (p. 315) to persistent organic pollutants (p. 402) to climate change (pp. 528–529).

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Addressing Acid Deposition

Table 17.1  Impacts of Acid Deposition

Just as stratospheric ozone depletion crosses political boundaries, so does another atmospheric pollution concern—acid deposition. As with ozone depletion, we are seeing some success in addressing this challenge.

Fossil fuel pollution spreads acidic substances widely

Acid deposition has many impacts Acid deposition has wide-ranging, cumulative detrimental effects on ecosystems and on our infrastructure (Table 17.1). Acids leach

•

Accelerated leaching of base cations (ions such as Ca2+, Mg2+, NA+, and K+, which counteract acid deposition) from soil

•

 llowed sulfur and nitrogen to accumulate in soil, where exA cess N can overfertilize native plants and encourage weeds

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Increased dissolved inorganic aluminum in soil, hindering plant uptake of water and nutrients

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 eached calcium from needles of red spruce, causing trees to L die from wintertime freezing

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Increased mortality of sugar maples due to leaching of base cations from soil and leaves

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 cidified 41% of Adirondack, New York, lakes and 15% of A New England lakes

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Diminished lakes’ capacity to neutralize further acids

•

Elevated aluminum levels in surface waters

•

 educed species diversity and abundance of aquatic life, R affecting entire food webs

Source: Adapted from Driscoll, C.T., et al., 2001. Acid rain revisited. Hubbard Brook Research Foundation. © 2001 C.T. Driscoll. Used with permission.

nutrients such as calcium, magnesium, and potassium ions from the topsoil, altering soil chemistry and harming plants and soil organisms. This occurs because hydrogen ions from acid precipitation take the place of calcium, magnesium, and potassium ions in soil compounds, and these valuable nutrients leach into the subsoil, where they become inaccessible to plant roots. Acid precipitation also “mobilizes” toxic metal ions such as aluminum, zinc, mercury, and copper by chemically converting them from insoluble forms to soluble forms. Elevated soil concentrations of metal ions such as aluminum weaken plants by damaging root tissue, hindering their uptake of water and nutrients. In some areas, acid fog with a pH of 2.3 (equivalent to vinegar, and

Primary pollutants

Sulfur dioxide (SO2) Nitric oxide (NO)

Secondary pollutants Water (H2O) Oxygen (O2) and oxidants

Sulfuric acid (H2SO4) Nitric acid (HNO3)

Acid precipitation

Figure 17.28 Acid deposition can have consequences far downwind from its source. Sulfur dioxide and nitric oxide emitted by industries and utilities are transformed into sulfuric acid and nitric acid through chemical reactions in the atmosphere. These acidic compounds descend to Earth’s surface in rain, snow, fog, and dry deposition.

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Acid deposition (or acidic deposition) refers to the deposition of acidic (pp. 45–46) or acid-forming pollutants from the atmosphere onto Earth’s surface. This can take place either by precipitation (commonly referred to as acid rain, but also including acid snow, sleet, and hail), by fog, by gases, or by the deposition of dry particles. Acid deposition is one type of atmospheric deposition, which refers more broadly to the wet or dry deposition on land of a wide variety of pollutants, including mercury, nitrates, organochlorines, and others. Acid deposition originates primarily with the emission of sulfur dioxide and nitrogen oxides, largely through fossil fuel combustion by automobiles, electric utilities, and industrial facilities. Once airborne, these pollutants can react with water, oxygen, and oxidants to produce compounds of low pH (p. 46), primarily sulfuric acid and nitric acid. Suspended in the troposphere, droplets of these acids may travel days or weeks for hundreds of kilometers before falling in precipitation (Figure 17.28). Depending on climate, 20% to 80% of all acidic compounds emitted into the atmosphere may fall in precipitation, with the remainder falling as dry deposition.

Acid deposition in northeastern forests has . . .

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to buffer themselves against acid deposition. This also means that once calcium or similar ions are leached from a soil, the soil becomes more sensitive to acidification. Besides altering natural ecosystems, acid precipitation damages crops, erodes stone buildings, corrodes cars, and erases the writing from tombstones. Ancient cathedrals in Europe, monuments in Washington, D.C., temples in Asia, and stone statues in London are experiencing billions of dollars of damage as their features dissolve away (Figure 17.30). Because the pollutants leading to acid deposition can travel long distances, their effects may be felt far from their sources. For instance, much of the pollution from power plants and factories in Pennsylvania, Ohio, and Illinois falls out in states to their east, including New York, Vermont, and New Hampshire, as well as in regions of Canada to the north. As a result, regions of greatest acidification tend to be downwind from heavily industrialized source areas of pollution.

Figure 17.29 Acid deposition killed these trees on Mount Mitchell in North Carolina.

over 1000 times more acidic than normal rainwater) has enveloped forests for extended periods, killing trees (Figure 17.29). When acidic water runs off from land, it affects streams, rivers, and lakes. Thousands of lakes in Canada, Scandinavia, the United States, and elsewhere have lost their fish because acid precipitation leaches aluminum ions out of soil and rock and into waterways, where they damage the gills of fish and disrupt their salt balance, water balance, breathing, and circulation. Terrestrial animals are affected, too; populations of snails and other invertebrates typically decline, and this reduces the food supply for birds. The severity of all these effects depends not only on the pH of the deposition, but also on the acid-neutralizing capacity of the soil, rock, or water that receives the acidic input. Substrates differ naturally in their chemistry and pH, and regions with more alkaline soil, rock, or water have a greater capacity

(a) Before acid rain damage

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We are addressing acid deposition The emissions trading program for sulfur dioxide established by the Clean Air Act of 1990 has helped us address acid deposition. The economic incentives created by this cap-and-trade program have encouraged polluters to invest in technologies such as scrubbers (p. 479) and to devise other ways to become cleaner and more efficient. As a result, SO2 emissions across the United States have fallen by 67%, and the program is now preventing the emission of 10 million tons of SO2 per year (see Figure 7.16, p. 201). The EPA has calculated that the program’s economic benefits outweigh its costs by 40 to 1. As a result of declining SO2 emissions, average sulfate loads in precipitation across the eastern United States were 51% lower in 2008–2010 than in 1989–1991. Emissions of NOX also have been lowered significantly, thanks to the emissions-trading program, and wet nitrogen deposition declined between these periods as well. As a result, air and water quality has improved throughout the eastern United States (Figure 17.31).

(b) After acid rain damage

Figure 17.30 Acid deposition corrodes statues and buildings. Shown is an Egyptian obelisk known as Cleopatra’s Needle, in Central Park, New York City, (a) before and (b) after the onset of significant acid deposition.

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≤ 4.1 4.5 4.9 5.3 ≥ 5.7 (a) Acid deposition in 1990

vulnerable. Moreover, scientists point out that further pollution reductions are needed if we are to fully restore ecosystems in the Northeast and prevent further damage to property and infrastructure. While the United States, Canada, and Western Europe are beginning to recover from acid deposition after cutting sulfur emissions, acid deposition is becoming worse in industrializing nations. Today China emits the most sulfur dioxide of any nation and has the world’s worst acid rain problem, as a result of extensive coal combustion in power plants and factories that often lack effective pollution control equipment. The government is tackling the issue, but it faces a challenge as the nation’s industrial sector continues to expand by leaps and bounds. Overall, data on acid deposition show that we have made advances in controlling outdoor air pollution, but that more can be done. The same can be said for indoor air pollution, a source of human health threats that is less familiar to most of us, but statistically more dangerous.

Indoor Air Quality

(b) Acid deposition in 2011

Figure 17.31 Precipitation has become less acidic as a result of air quality improvements following the Clean Air Act. Average pH values for precipitation have risen between (a) 1990 and (b) 2011. Precipitation remains most acidic in the Northeast and Midwest, near and downwind from (roughly east of) areas of heavy industry. Data from the National Atmospheric Deposition Program. In the area where you live, how did the pH of precipitation change between 1990 and 2011? Has precipitation become more acidic or less acidic?

At Hubbard Brook Experimental Forest in New Hampshire, where scientists first studied acid deposition’s effects in the United States, researchers jumpstarted a long, slow recovery by using a helicopter to distribute 50 tons of a calciumcontaining mineral called wollastonite over one watershed. Within three years of this experimental application, topsoil pH rose from 3.9 to 4.2. Sugar maples (one of the forest’s key tree species that had been declining) are now producing healthier foliage, thicker root growth, more seeds, and more surviving seedlings. Over the next 50 years, scientists plan to evaluate the impact of calcium addition on the watershed’s soil, water, and life, and compare these results to watersheds where calcium remains depleted. As with ozone depletion, there is a time lag before the positive consequences of emissions cuts kick in, so it will take time for acidified ecosystems to recover. Research in 2012 indicated that soils across the northeastern United States are showing signs of recovery, but that they remain degraded and

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Indoor air generally contains higher concentrations of pollutants than does outdoor air. As a result, the health impacts from indoor air pollution in workplaces, schools, and homes outweigh those from outdoor air pollution. The World Health Organization (WHO) attributes nearly 3.5 million premature deaths each year to indoor air pollution (compared with 3.3 million for outdoor air pollution). Indoor air pollution takes nearly 10,000 lives each day. If this seems surprising, consider that the average U.S. citizen spends at least 90% of his or her time indoors. Then consider the dizzying array of consumer products in our homes and offices that play major roles in our daily lives. Many of these products are made of synthetic materials, and novel synthetic substances are not comprehensively tested for health effects before being brought to market (Chapter 14). Products and materials as diverse as cleaning fluids, insecticides, furniture, carpeting, and the many varieties of plastics all exude volatile chemicals into the air. Ironically, some attempts to be environmentally prudent during the “energy crises” of the 1970s (p. 562) worsened indoor air quality. To improve energy efficiency by reducing heat loss, building managers sealed off ventilation in buildings, and designers constructed new buildings with limited ventilation and with windows that did not open. These steps saved energy, but they also worsened indoor air quality by trapping stable, unmixed air—and pollutants—inside. There is good news, however. In both developing and developed nations, we have known and feasible ways to address the primary causes of indoor air pollution.

Burning fuelwood causes indoor pollution in the developing world Indoor air pollution has by far the greatest impact in the developing world, where poverty forces millions of people

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≤ 4.1 4.5 4.9 5.3 ≥ 5.7

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Geologic Radon Potential Low Moderate / Variable

Figure 17.32 In the developing world, many people build fires inside their homes for cooking and heating, as seen here in a Maasai home in Kenya. Indoor fires expose people to severe pollution from particulate matter and carbon monoxide.

to burn wood, charcoal, animal dung, or crop waste inside their homes for cooking and heating, with little or no ventilation (Figure 17.32). In the air of such homes, the WHO has found that concentrations of particulate matter are commonly 20 times above U.S. EPA standards. As a result, people inhale dangerous amounts of soot, carbon monoxide, and other pollutants, which together increase risks of premature death by pneumonia, bronchitis, and lung cancer, as well as allergies, sinus infections, cataracts, asthma, emphysema, and heart disease. International health researchers estimate that indoor air pollution from burning fuelwood, dung, and coal kills 3.5 million people each year, comprising nearly 7% of all deaths. Many people are not aware of the health risks, and of those who are, many are too poor to have viable alternatives.

Tobacco smoke and radon are the primary indoor pollutants in industrialized nations

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In industrialized nations, the primary indoor air health risks are cigarette smoke and radon, a naturally occurring radioactive gas. Smoking cigarettes irritates the eyes, nose, and throat; worsens asthma and other respiratory ailments; and greatly increases the risk of lung cancer. Inhaling secondhand smoke (smoke inhaled by a nonsmoker who is nearby or shares an enclosed airspace with a smoker) causes many of the same problems. This hardly seems surprising when one considers that tobacco smoke is a brew of over 4000 chemical compounds, some of which are known or suspected to be toxic or carcinogenic. Smoking has become less popular in developed nations in recent years as a result of public education campaigns, and many public and private venues now ban smoking. Still, smoking is estimated in the United States alone to cause 160,000 lung cancer deaths per year, and secondhand smoke to cause 3000.

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High

Figure 17.33 One’s risk from radon depends largely on underground geology. This map shows levels of risk across the United States. Testing your home for radon is the surest way to determine whether this colorless, odorless gas could be a problem. Data from U.S. Geological Survey, 1993. Generalized geological radon potential of the United States, 1993.

Radon gas is the second-leading cause of lung cancer in the developed world, responsible for an estimated 21,000 deaths per year in the United States and for 15% of lung cancer cases worldwide. Radon (p. 384) is a radioactive gas resulting from the natural decay of uranium in soil, rock, or water. It seeps up from the ground and can infiltrate buildings. Colorless and odorless, radon’s presence can be impossible to predict without knowing an area’s underlying geology (Figure 17.33). The only way to determine whether radon is entering a building is to sample air with a test kit. The EPA estimates that 6% of U.S. homes exceed its safety standard for radon. Since the 1980s, millions of U.S. homes have been tested for radon and close to a million have undergone radon mitigation. New homes are being built with radon-resistant features.

Many VOCs pollute indoor air In our daily lives at home, we are exposed to many indoor air pollutants (Figure 17.34). The most diverse are volatile organic compounds (p. 477). These airborne carbon-containing compounds are released by plastics, oils, perfumes, paints, cleaning fluids, adhesives, and pesticides. VOCs evaporate from furnishings, building materials, color film, carpets, laser printers, fax machines, and sheets of paper. Some products, such as chemically treated furniture, release large amounts of VOCs when new and progressively less as they age. Other items, such as photocopying machines, emit VOCs each time they are used. Although we are surrounded by products that emit VOCs, they are released in very small amounts. Studies have found total levels of VOCs in buildings to be nearly always less than 1 part per 10 million. This is, however, a much greater concentration than is found outdoors. Moreover, we experience instances of especially high exposure. The “new car smell” that fills the interiors of new automobiles comes from

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Heating and cooling ducts Pollutants: Mold and bacteria Health risks: Allergies, asthma, respiratory problems

Hot showers with chlorine-treated water Pollutant: Chloroform Health risks: Nervous system damage

Furniture; carpets; foam insulation; pressed wood Pollutant: Formaldehyde Health risks: Respiratory irritation, cancer

Old paint Pollutant: Lead Health risks: Nervous system and organ damage

Leaky or unvented gas and wood stoves and furnaces; car left running in garage Pollutant: Carbon monoxide Health risks: Neural impairment, fatal at high doses

Fireplaces; wood stoves Pollutant: Particulate matter Health risks: Respiratory problems, lung cancer

Gasoline Pollutant: VOCs Health risks: Cancer

Pipe insulation; floor and ceiling tiles Pollutant: Asbetos Health risks: Asbestosis

Pets Pollutant: Animal dander Health risks: Allergies Pesticides; paints; cleaning fluids Pollutants: VOCs and others Health risks: Neural or organ damage, cancer Rocks and soil beneath house Pollutant: Radon Health risks: Lung cancer

Computers and office equipment Pollutant: VOCs Health risks: Irritation, neural or organ damage, cancer

Tobacco smoke Pollutants: Many toxic or carcinogenic compounds Health risks: Lung cancer, respiratory problems

Figure 17.34 The typical home contains many sources of indoor air pollution. Shown are common sources, the major pollutants they emit, and some of the health risks they pose.

a complex mix of dozens of VOCs as they outgas from the newly manufactured plastic, metal, and leather components of the car. The smell diminishes with time, but some scientific studies warn of health risks from this brew and recommend that you keep a new car well ventilated. The implications for human health of chronic exposure to volatile organic compounds are far from clear. Because they generally exist in low concentrations and because individuals regularly are exposed to mixtures of many different types, it is extremely difficult to study the effects of any one pollutant. An exception is formaldehyde, a VOC that has clear and known health impacts. Widely used in pressed wood, insulation, and other products, formaldehyde irritates mucous membranes, induces skin allergies, and causes a number of other ailments. The use of plywood has decreased in the last decade because of health concerns over formaldehyde.

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Living organisms can pollute The most widespread source of indoor air pollution in the developed world may be tiny living organisms. Dust mites and animal dander can worsen asthma in children. The airborne spores of some fungi, molds, and mildews can cause allergies, asthma, and other respiratory ailments. Some airborne bacteria can cause infectious disease, including Legionnaires’ disease. Of the estimated 10,000–15,000 annual U.S. cases of Legionnaires’ disease, 5–15% are fatal. Heating and cooling systems in buildings make ideal breeding grounds for microbes, providing moisture, dust, and foam insulation as substrates, along with air currents to carry the organisms aloft. Microbes that induce allergic responses are thought to be a major cause of building-related illness, a sickness produced by indoor pollution. When the cause of such an illness is a

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Unvented stoves and heaters Pollutant: Nitrogen oxides Health risks: Respiratory problems

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mystery, and when symptoms are general and nonspecific, the illness is often called sick-building syndrome. The U.S. Occupational Safety and Health Administration (OSHA) estimates that 30–70 million Americans have suffered ailments related to the building in which they live. We can reduce the prevalence of sick-building syndrome by using low-toxicity construction materials and ensuring that buildings are well ventilated.

Weighing the Issues How Safe Is Your Indoor Environment? Think about the amount of time you spend indoors. Name some potential indoor air quality hazards in your home, work, or school environment. Are these spaces well ventilated? What could you do to improve the safety of the indoor spaces you use?

We can enhance indoor air quality Using low-toxicity materials, monitoring air quality, keeping rooms clean, and providing adequate ventilation are the keys to alleviating indoor air pollution in most situations. Remedies for fuelwood pollution in the developing world include drying wood before burning (which reduces the amount of smoke produced), cooking outside, shifting to less-polluting fuels (such as natural gas), and replacing inefficient fires with cleaner stoves that burn fuel more efficiently. The Chinese government invested in a program that has placed fuel-efficient stoves in millions of homes across China. Installing hoods, chimneys, or cooking windows can increase ventilation for little cost, alleviating most indoor smoke pollution. In the industrialized world, we can try to avoid cigarette smoke, limit our use of plastics and treated wood, and restrict our exposure to pesticides, cleaning fluids, and other toxic substances by keeping them in garages or outdoor sheds. The EPA recommends that we test our homes and offices for radon,

mold, and carbon monoxide. Because carbon monoxide is so deadly and so hard to detect, many homes are equipped with detectors that sound an alarm if incomplete combustion produces dangerous levels of CO. In addition, keeping rooms and air ducts clean and free of mildew and other biological pollutants will reduce potential irritants and allergens. Most of all, keeping our indoor spaces well ventilated will minimize concentrations of the pollutants among which we live. Progress is being made worldwide in alleviating the health toll of indoor air pollution. Researchers calculate that rates of premature death from indoor air pollution dropped nearly 40 percent from 1990 to 2010. Taking steps like those described here should bring us further progress in safeguarding people’s health.

Conclusion Indoor air pollution poses potentially serious health hazards, but by keeping informed and taking appropriate precautions on a personal basis, we each can minimize our risks. Outdoor air pollution has been addressed more effectively by government legislation and regulation, together with pollutioncontrol technologies. Indeed, reductions in outdoor air pollution in the United States and other industrialized nations represent some of the greatest strides made in environmental protection to date. The global depletion of stratospheric ozone has been halted thanks to our efforts, and acid deposition is gradually being addressed. Room for improvement remains, however, particularly in reducing acid deposition and photochemical smog. In the developing world, indoor and outdoor air pollutant levels are higher and take a heavy toll on people’s health. Reducing pollution from indoor fuelwood burning, automobile exhaust, coal combustion in outmoded facilities, and other sources will continue to pose challenges as the world’s less-wealthy nations industrialize.

Reviewing Objectives You should now be able to: Describe the composition, structure, and function of Earth’s atmosphere

• The atmosphere moderates climate, provides us oxygen, conducts and absorbs solar radiation, and transports and recycles nutrients and waste. (p. 468) • The atmosphere consists of 78% nitrogen gas, 21% oxygen gas, and a variety of other gases in minute concentrations. (p. 468)

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• The atmosphere includes four layers: the troposphere, stratosphere, mesosphere, and thermosphere. Temperature and other characteristics vary across these layers. Ozone is concentrated in the stratosphere. (pp. 468–469)

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Relate weather and climate to atmospheric conditions

• The sun’s energy heats the atmosphere, drives air circulation, and helps determine weather, climate, and the seasons. (pp. 470–471) • Weather is a short-term phenomenon, whereas climate is a long-term phenomenon. Fronts, pressure systems, and the interactions among air masses influence weather. (pp. 471–472) • Global convective cells called Hadley, Ferrel, and polar cells create latitudinal climate zones. (p. 473) • Hurricanes and tornadoes are types of cyclonic storms that can threaten life and property. (p. 474)

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Identify major pollutants, outline the scope of outdoor air pollution, and assess solutions

• Natural sources such as fires, volcanoes, and windblown dust pollute the atmosphere. Human activity can worsen some of these phenomena. (pp. 474–475) • The pollutants we emit include primary and secondary pollutants from point and non-point sources. (p. 475) • To safeguard public health under the Clean Air Act, the U.S. EPA and state governments monitor emissions of six major pollutants: carbon monoxide, sulfur dioxide, nitrogen oxides, volatile organic compounds, particulate matter, and lead. (pp. 476–477) • Agencies also monitor ambient concentrations of the six criteria pollutants: carbon monoxide, sulfur dioxide, nitrogen dioxide, tropospheric ozone, particulate matter, and lead. (p. 478) • Thanks to public policy and to pollution-control technologies, emissions in the United States have decreased substantially since 1970, and ambient air quality has improved in most respects. (pp. 477–480) • Emissions of 187 toxic air pollutants are also declining, but they still pose health risks. (p. 480)

• Industrializing nations such as China and India are experiencing some of the world’s worst air pollution today. (pp. 481–482) • Industrial smog produced by fossil fuel combustion is still a problem in urban and industrial areas of many developing nations. (pp. 482–483) • Photochemical smog is created by chemical reactions of pollutants in the presence of sunlight. It impairs visibility and human health in urban areas. (p. 483) • Cities such as Los Angeles and Mexico City are taking bold steps to address photochemical smog. (pp. 483, 486) Explain stratospheric ozone depletion and identify steps taken to address it

• CFCs and other persistent human-made compounds destroy stratospheric ozone. Thinning ozone concentrations pose

• Ozone depletion is most severe over Antarctica, where an “ozone hole” appears each spring. (p. 487) • The Montreal Protocol and its follow-up agreements have proven remarkably successful in reducing emissions of ozone-depleting substances. (p. 490) • The long residence time of CFCs in the atmosphere accounts for a time lag between the protocol and full restoration of stratospheric ozone. (p. 490) Define acid deposition, illustrate its consequences, and explain how we are addressing it

• Acid deposition results when pollutants such as SO2 and NO react in the atmosphere to produce strong acids that are deposited on Earth’s surface. (p. 491) • Acid deposition may be wet (e.g., “acid rain”) or dry, and it may occur a long distance from the source of pollution. (p. 491) • Acid deposition damages soils, water bodies, plants, animals, ecosystems, and human property and infrastructure. (pp. 491–492) • Regulation, cap-and-trade programs, and technology are all helping to reduce acid deposition in North America. Industrializing nations will need to tackle the problem as well. (pp. 492–493) Characterize the scope of indoor air pollution and assess solutions

• Indoor air pollution causes more deaths and health problems worldwide than outdoor air pollution. (p. 493) • Indoor burning of fuelwood is the developing world’s primary indoor air pollution risk. (pp. 493–494) • Tobacco smoke and radon are the worst indoor pollutants in the developed world. (p. 494) • Volatile organic compounds and living organisms can pollute indoor air. (pp. 494–495) • Using low-toxicity materials, keeping spaces clean, monitoring air quality, and maximizing ventilation all help to enhance indoor air quality. (p. 496)

Testing Your Comprehension 1. What determines the amount of solar radiation that strikes Earth’s surface? What is the role of solar energy in creating seasons? 2. Where is the “ozone layer” located? How and why is stratospheric ozone beneficial for people, whereas tropospheric ozone is harmful?

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3. How does solar energy influence weather and climate? Describe how Hadley, Ferrel, and polar cells help to determine long-term climatic patterns and the location of biomes.

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• The U.S. EPA is taking early steps toward regulating greenhouse gases as pollutants because they drive climate change. (pp. 480–481)

dangers to life because they allow more ultraviolet radiation to reach Earth’s surface. (pp. 486–487)

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4. List the main sources responsible for the emission of the following pollutants—CO, SO2, NOx, VOCs, and particulate matter into the atmosphere. 5. How does a primary pollutant differ from a secondary pollutant? Give an example of each. 6. Using the examples of Tehran and Los Angeles, discuss the special problems that vehicles create for urban outdoor air pollution. 7. How does photochemical smog differ from industrial smog? How do the weather and topography influence smog formation?

8. Explain how chlorofluorocarbons (CFCs) deplete stratospheric ozone. Why is this depletion considered a longterm international problem? What was done to address this problem? 9. Why are the effects of acid deposition often felt in areas far from where the primary pollutants are produced? List three impacts of acid deposition. 10. Why is indoor pollution still such a huge problem? What are the most dangerous indoor pollutants in developing and developed nations?

Seeking Solutions 1. Consider responses to the photochemical smog pollution that has plagued Los Angeles, Mexico City, and other metropolitan areas. Describe several ways in which major cities have tried to improve their air quality. 2. Name one type of natural air pollution, and discuss how human activity can sometimes worsen it. What potential solutions can you think of to minimize this human impact? 3. Describe how and why emissions of major pollutants have been reduced by well over 50% in the United States since 1970, despite increases in population, energy use, and economic activity. 4. International action through a treaty has helped to halt further stratospheric ozone depletion, but other transboundary pollution issues, including acid deposition, have not yet been addressed as effectively. What types of actions do you feel are appropriate for pollutants that cross political boundaries? 5. Think it Through  You have become the head of your county health department, and the EPA informs you that your county has failed to meet the national ambient air quality standards for ozone, sulfur dioxide, and nitrogen

dioxide. Your county is partly rural but is home to a city of 200,000 people and 10 sprawling suburbs. There are several large and aging coal-fired power plants, a number of factories with advanced pollution control technology, and no public transportation system. What steps would you urge the county government to take to meet the air quality standards? Explain how you would prioritize these steps. 6. Think it Through You have been elected mayor of the largest city in your state. Your city’s residents are complaining about photochemical smog and traffic congestion. Traffic engineers and city planners project that population and traffic will grow by 20% in the next decade. Some experts are urging you to restrict traffic into the city, allowing only cars with odd-numbered license plates on oddnumbered days, and those with even-numbered plates on even-numbered days. However, business owners fear losing money should these measures discourage shoppers from visiting. Consider the particulars of your city, and then decide whether you will pursue an odd-day/even-day driving program, and explain why or why not. What other steps would you take to address your city’s smog problem?

Calculating Ecological Footprints

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“While only some motorists contribute to traffic fatalities, all motorists contribute to air pollution fatalities.” So stated a writer for the Earth Policy Institute, pointing out that air pollution kills far more people than vehicle accidents. According to EPA data, emissions of nitrogen oxides in the United States in 2012 totaled 11.3 million tons. Nitrogen oxides come from fuel combustion in motor vehicles, power plants, and other industrial, commercial, and residential sources, but fully 6.4 million tons of the 2012 total came from vehicles. The U.S. Census Bureau estimates the nation’s population to have been 313.9 million in 2012 and projects that it will reach 346.7 million in 2025. Considering these data, calculate the missing values in the table below (1 ton = 2000 lb).

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Total NOX emissions (lb)

NOX emissions from vehicles (lb)

You

 

 

Your class

 

 

Your state

 

 

United States

22.6 billion 

 12.8 billion

Data from U.S. EPA.

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1. By what percentage is the U.S. population projected to increase between 2012 and 2025? Do you think that NOX emissions will increase, decrease, or remain the same over that period of time? Why? (You may want to refer to Figure 17.14.) 2. Assume you are an average American driver. Using the 2012 emissions totals, how many pounds of NOX

STUDENTS Go to MasteringEnvironmentalScience for assignments, the etext, and the Study Area with practice tests, videos, current events, and activities.

emissions are you responsible for creating? How many pounds would you prevent if you were to reduce by half the vehicle miles you travel? What percentage of your total NOX emissions would that be? 3. How might you reduce your vehicle miles traveled by 50%? What other steps could you take to reduce the NOX emissions for which you are responsible?

INSTRUCTORS Go to MasteringEnvironmentalScience for automatically graded activities, current events, videos, and reading questions that you can assign to your students, plus Instructor Resources.

C H A P T E R 1 7 • A t m o s pher i c Sc i e n ce , A i r Q u a l i t y , a n d P o l l u t i o n C o n tr o l

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18

The Maldives’ underwater cabinet meeting

Global Climate Change Upon completing this chapter, you will be able to: Describe Earth’s climate system and explain the factors influencing global climate

Outline current and future trends and impacts of global climate change

Characterize human influences on the atmosphere and on climate

Suggest ways we may respond to climate change

Summarize how researchers study climate

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C EN T R AL CA S E S T U DY

Rising Seas May Flood the Maldives ASIA EUROPE

“Climate change threatens the very existence of our country.” —Mohamed Waheed, president, Maldives INDIA

AFRICA

Maldives

“If we can’t save the Maldives today, we can’t save London, New York, or Hong Kong tomorrow.” —Mohamed Nasheed, former president, Maldives

Indian Ocean

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SOS from the front line: Climate change is happening and it threatens the rights and security of everyone on Earth. With less than one degree of global warming, the glaciers are melting, the ice sheets collapsing, and low-lying areas are in danger of being swamped. We must unite in a global effort to halt further temperature rises, by slashing carbon dioxide emissions to a safe level of 350 parts per million.

The underwater cabinet meeting was part of a campaign to draw global attention to the impacts of climate change. Nasheed followed this with a high-profile role at international climate talks in Copenhagen, where he pleaded with the United States, China, India, and other major polluting nations to unite in efforts to reduce emissions of gases that warm the atmosphere. Back home in the Maldives, Nasheed announced a plan to make his nation carbon-neutral by 2020. But already residents had to be evacuated from several of the lowest-lying islands, and Nasheed arranged to begin buying land in mainland nations in case his people one day need to abandon their homeland. Then in 2012, Nasheed—the nation’s first democratically elected president—was forced from power at gunpoint, and the vice-president was installed in his place. Nasheed’s supporters called it a coup d’etat. His detractors said he had abused power by illegally imprisoning the nation’s chief judge. They put him on trial, which many viewed as simply an attempt to keep him out of the 2013 presidential election. Despite the political turmoil, the people of the Maldives remain united in their concern over climate change. The new president, Mohamed Waheed, proposed to continue the

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With sun-drenched beaches, colorful coral reefs, and a spectacular tropical setting, the Maldives seems a paradise to the many tourists who visit. For its 370,000 residents, this island nation in the Indian Ocean is home. But residents and tourists alike now fear that the Maldives could soon be submerged by the rising seas brought by global climate change. For a nation of 1200 islands whose highest point is just 2.4 m (8 ft) above sea level, rising seas are a matter of life or death. Four-fifths of the Maldives’ land area lies less than 1 m (39 in.) above sea level. The world’s oceans rose 10–20 cm (4–8 in.) during the 20th century as warming temperatures expanded ocean water and as melting polar ice discharged water into the ocean. According to current projections, sea level will rise another 18–59 cm (7–23 in.) by the year 2100. Higher seas are expected to flood large areas of the Maldives and cause salt water to contaminate drinking water supplies. Scientists expect storms intensified by warmer water to erode beaches and damage the coral reefs that are vital to the nation’s tourism and fishing industries. “If things go business as usual,” former president Mohamed Nasheed has said, “our country will not exist.” Although small island nations like the Maldives are responsible for very few of the carbon emissions that drive global climate change, these nations are the ones bearing the earliest consequences. The Maldives’ political leaders have made sure the world knows this. In 2009, President Nasheed donned scuba gear and dove into the blue waters of Girifushi Island lagoon, followed by his entire cabinet. These officials held the world’s first underwater cabinet meeting. Sitting at a table beneath the waves, they signed a declaration reading:

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plan for carbon-neutrality through a voluntary tax on tourists that could fund carbon offsets and investment in renewable energy. Residents of the Maldives are not alone in their predicament. Other island nations, from the Galápagos to Fiji to the Seychelles, also face a future of encroaching seawater. These island nations have organized themselves to make their concern over climate change known to the world through AOSIS, the Alliance of Small Island States. Mainland coastal areas across the world will face similar challenges from sea level rise—from the hurricane-battered coasts of Florida, Louisiana, Texas, and the Carolinas to coastal

Our Dynamic Climate Climate influences virtually everything around us, from the day’s weather to major storms, from crop success to human health, and from national security to the ecosystems that support our economies. If you are a student in your teens or twenties, the accelerating change in our climate today may well be the major event of your lifetime and the phenomenon that most shapes your future. Climate change is also the fastest-developing area of environmental science. New scientific studies that refine our understanding of climate are published every week, and policymakers and businesspeople make decisions and announcements just as quickly. By the time you read this chapter, some of its information will already be out of date. We urge you to explore further, with your instructor and on your own, the most recent information on climate change and the impacts it will have on your future.

What is climate change?

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Climate describes an area’s long-term atmospheric conditions, including temperature, precipitation, wind, humidity, barometric pressure, solar radiation, and other characteristics. Climate differs from weather (p. 471) in that weather specifies conditions at localized sites over hours or days, whereas climate describes conditions across broader regions over years, decades, or centuries. Global climate change encompasses an array of changes in aspects of Earth’s climate, such as temperature, precipitation, and storm frequency and intensity. People often use the term global warming synonymously in casual conversation, but global warming refers specifically to an increase in Earth’s average surface temperature. Global warming is only one aspect of global climate change, but warming does in turn drive other components of climate change. Over the long term, our planet’s climate varies naturally. However, today’s climatic changes are unfolding at an exceedingly rapid rate, and they are creating conditions humanity has never experienced. Scientists agree that human activities, notably fossil fuel combustion and deforestation, are largely responsible. Understanding how and why today’s climate is changing requires understanding how our planet’s climate functions. Thus, we first will examine Earth’s climate system—a complex and finely tuned system that has nurtured life for billions of years.

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cities such as San Francisco and New York City. Superstorm Sandy in 2012 was a wake-up call for the eastern United States. The lost lives and billions of dollars of damage brought by this massive hurricane and its storm surge in New York, New Jersey, and other states made clear that the costs of rising seas could be enormous. Storm damage from rising seas is just one of the many imminent consequences of global climate change. In one way or another, climate change will affect each and every one of us for the remainder of our lifetimes. Putting solutions into action stands as a central challenge for our society right now and for the foreseeable future.

Three factors influence climate Three natural factors exert the most influence on Earth’s climate. The first is the sun. Without it, Earth would be dark and frozen. The second is the atmosphere. Without it, Earth would be as much as 33°C (59°F) colder on average, and temperature differences between night and day would be far greater than they are. The third is the oceans, which store and transport heat and moisture. The sun supplies most of our planet’s energy. Earth’s atmosphere, clouds, land, ice, and water together absorb about 70% of incoming solar radiation and reflect the remaining 30% back into space (Figure 18.1). The 70% that is absorbed powers many of Earth’s processes, from winds to waves to evaporation to photosynthesis. We will assess how each major factor influences climate, focusing first on the atmosphere.

Greenhouse gases warm the lower atmosphere As Earth’s surface absorbs solar radiation, the surface increases in temperature and emits infrared radiation (p. 49), radiation with wavelengths longer than those of visible light. Atmospheric gases having three or more atoms in their molecules tend to absorb infrared radiation. These include water vapor, ozone (O3), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4), as well as halocarbons, a diverse group of mostly human-made gases that includes chlorofluorocarbons (CFCs; p. 487). Such gases are known as greenhouse gases. After absorbing radiation emitted from the surface, greenhouse gases subsequently re-emit infrared radiation. Some of this re-emitted energy is lost to space, but some travels back downward, warming the lower atmosphere (specifically the troposphere; p. 469) and the surface in a phenomenon known as the greenhouse effect. Greenhouse gases differ in their ability to warm the troposphere and surface. Global warming potential refers to the relative ability of one molecule of a given greenhouse gas to contribute to warming. Table 18.1 shows global warming potentials for several greenhouse gases. Values are expressed in relation to carbon dioxide, which is assigned a value of 1. Thus, a molecule of methane is 25 times more potent than a

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Incoming solar radiation 342

Units are in watts per square meter

Outgoing longwave radiation 235

Reflected solar radiation 107

Emitted by Emitted by atmosphere surface and passing and clouds through atmosphere 195 40

Reflected by clouds, aerosols, and atmosphere 77

Absorbed by atmosphere 67

Shorterwavelength UV and visible light passes through atmosphere

Thermals 24

Greenhouse gases in atmosphere

Evapotranspiration 78

Reflected by surface 30

Radiation emitted by surface 390 Longer-wavelength infrared radiation is absorbed and re-emitted by atmosphere, creating the greenhouse effect

Absorbed by surface 168

Back radiation 324 Absorbed by surface 324

Figure 18.1 Our planet receives 342 watts of energy per square meter from the sun, and it naturally reflects and emits this same amount. Earth absorbs nearly 70% of the solar radiation it receives, and reflects the rest back into space (yellow arrows). The radiation absorbed is then re-emitted (orange arrows) as infrared radiation, which has longer wavelengths. Greenhouse gases in the atmosphere absorb a portion of this long-wavelength radiation and then re-emit it, sending some back downward to warm the atmosphere and the surface by the greenhouse effect. Data from Kiehl, J.T., and K.E. Trenberth, 1997. Earth’s annual global mean energy budget. Bulletin of the American Meteorological Society 78: 197–208. © American Meteorological Society (AMS). By permission.

Table 18.1 Global Warming Potentials of Four Greenhouse Gases GREENHOUSE GAS Carbon dioxide Methane Nitrous oxide Hydrochlorofluorocarbon HFC-23

RELATIVE HEAT-TRAPPING ABILITY (IN CO2 EQUIVALENTS) 1 25 298 14,800

Data are for a 100-year time horizon, from IPCC, 2007. Fourth assessment report. Climate change 2007: The physical science basis.

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activity consist mostly of carbon dioxide. And CO2 has a much longer residence time (pp. 475–476) in the atmosphere than methane, so methane’s impact is greater in the short term than in the long term. According to the latest data, CO2 is causing nearly six times more warming than methane, nitrous oxide, and halocarbons combined.

FAQ

The greenhouse effect works just like a greenhouse, right?

Actually, not quite. A greenhouse helps plants grow because its glass walls trap heat. In contrast, greenhouse gas molecules in our atmosphere absorb particular wavelengths of light reflected up from the surface, then re-emit radiation at different wavelengths. Some of this radiation travels back toward the surface, keeping the surface and lower atmosphere warmer than they would otherwise be. This phenomenon differs from what happens in a greenhouse, but it was called the “greenhouse effect” in the past, and the name has stuck.

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molecule of carbon dioxide, and a molecule of nitrous oxide is 298 times more potent than a CO2 molecule. Although carbon dioxide is less potent on a per-molecule basis than methane or nitrous oxide, it is far more abundant in the atmosphere, so it contributes more to the greenhouse effect. Moreover, greenhouse gas emissions from human

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2000

Carbon dioxide (CO2) Methane (CH4) Nitrous oxide (N2O)

350

1800 1600 1400 1200

300

CH4 (ppb)

CO2 (ppm), N2O (ppb)

400

1000 800

250

600 0

500

1000 Year

1500

2000

Figure 18.2 Since the start of the industrial revolution, global atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased markedly. Data from Intergovernmental Panel on Climate Change (IPCC), 2007. Fourth assessment report. FAQ 2.1, Fig 1, in The physical science basis: Contribution of Working Group I.

By about what percentage has atmospheric carbon dioxide concentration increased since 1750?

Greenhouse gas concentrations are rising fast The greenhouse effect is a natural phenomenon, and greenhouse gases have been present in our atmosphere for all of Earth’s history. It’s a good thing, too. Without the natural greenhouse effect, our planet would be too cold to support life as we know it. Thus, it is not the natural greenhouse effect that concerns scientists today, but rather the anthropogenic (human-generated) intensification of the greenhouse effect. By adding novel greenhouse gases (certain halocarbons) to the atmosphere, and by increasing the concentrations of several natural greenhouse gases over the past 250 years (Figure 18.2), we are intensifying our planet’s greenhouse effect beyond what our species has ever experienced. We have boosted Earth’s atmospheric concentration of carbon dioxide from 280 parts per million (ppm) in the late 1700s to 396 ppm in 2013 (see Figure 18.2). Today’s atmospheric

CO2 concentration is at its highest level by far in over 800,000 years, and likely the highest in the last 20 million years. Why have atmospheric carbon dioxide levels risen so rapidly? Most carbon is stored for long periods in the upper layers of the lithosphere (p. 140). The deposition, partial decay, and compression of organic matter (mostly plants and phytoplankton) that grew in wetland or marine areas hundreds of millions of years ago led to the formation of coal, oil, and natural gas in buried sediments. In the absence of human activity, these carbon reservoirs would remain buried for many millions more years. However, over the past two centuries we have extracted these fossil fuels from the ground and burned them in our homes, factories, and automobiles, transferring large amounts of carbon from one reservoir (the underground deposits that stored the carbon for millions of years) to another (the atmosphere). This sudden flux of carbon from lithospheric reservoirs into the atmosphere is the main reason atmospheric carbon dioxide concentrations have increased so dramatically. At the same time, people have cleared and burned forests to make room for crops, pastures, villages, and cities. Forests serve as a reservoir for carbon as plants conduct photosynthesis (p. 50) and store carbon in their tissues. Thus, when we clear forests it reduces the biosphere’s ability to remove carbon dioxide from the atmosphere. In this way, deforestation (pp. 329–332) contributes to rising atmospheric CO2 concentrations. Figure 18.3 summarizes scientists’ current understanding of the fluxes (both natural and anthropogenic) of carbon dioxide between the atmosphere and reservoirs on Earth’s surface. Methane concentrations are also rising—2.5-fold since 1750 (see Figure 18.2)—and today’s atmospheric concentration is the highest by far in over 800,000 years. We release methane by tapping into fossil fuel deposits, raising livestock that emit methane as a metabolic waste product, disposing of organic matter in landfills, and growing crops such as rice. Human activities have also enhanced atmospheric concentrations of nitrous oxide. This greenhouse gas, a by-product of feedlots, chemical manufacturing plants, auto emissions, and synthetic nitrogen fertilizers, has risen by nearly 20% since 1750 (see Figure 18.2).

Natural fluxes Anthropogenic fluxes Units are in billions of metric tons of CO2 per year

504

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Land

Ocean

=

Net accumulation

Absorption 80

70

Release

260

260

Release

0.7

~15 Absorption

Weathering

0.3

Volcanoes

10

6 Changing land use

Increased uptake by plants

440

Industry

440

26

Respiration

Photosynthesis

Atmosphere

Figure 18.3 Human activities are sending more carbon dioxide from Earth’s surface to its atmosphere than is moving from the atmosphere to the surface. Shown are all current fluxes of CO2, with arrows sized according to mass. Green arrows indicate natural fluxes, and red arrows indicate anthropogenic fluxes. Adapted from IPCC, 2007. Fourth assessment report.

For every metric ton of carbon dioxide we emit due to changing land use (e.g. deforestation), how much do we emit from industry?

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2 Tropospheric Radiative forcing (watts/m2)

1

Soot on snow

0

Stratospheric –1

Radiative forcing expresses change in energy input

Feedback complicates our predictions As tropospheric temperatures increase, Earth’s water bodies should transfer more water vapor into the atmosphere, but scientists aren’t yet sure how this will affect our climate. On one hand, more atmospheric water vapor could lead to more warming,

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o ed alb ud Clo

Ae

ros o

ls

o ed alb rfa ce

Su

iox ide nd

rbo

Figure 18.4 Radiative forcing measures the degree of influence that aerosols, greenhouse gases, and other factors exert over Earth’s energy balance. In this graph, radiative forcing is expressed as the warming or cooling effect that each factor has on temperature today relative to 1750, in watts/m2. Red bars indicate positive forcing (warming), and blue bars indicate negative forcing (cooling). Albedo (p. 516) refers to the reflectivity of a surface. A number of more minor influences are not shown. Data from IPCC, 2007. Fourth assessment report.

which could lead to more evaporation and water vapor, in a positive feedback loop (pp. 124–125) that would amplify the greenhouse effect. On the other hand, more water vapor could enhance cloudiness, which might, in a negative feedback loop (pp. 124–125), slow global warming by reflecting more solar radiation back into space. In this second scenario, depending on whether low- or high-elevation clouds result, they might either shade and cool Earth (negative feedback) or else contribute to warming and accelerate evaporation and further cloud formation (positive feedback). We simply don’t yet know which effect might outweigh the other. Because of feedback loops, minor modifications of components of the atmosphere can potentially lead to major effects on climate. This poses challenges for making accurate predictions of future climate change.

Climate varies naturally for several reasons Besides atmospheric composition, our climate is influenced by cyclic changes in Earth’s rotation and orbit, variation in energy released by the sun, absorption of carbon dioxide by the oceans, and ocean circulation patterns.

Milankovitch cycles   In the 1920s, Serbian mathematician Milutin Milankovitch described three types of periodic changes in Earth’s rotation and orbit around the sun. Over thousands of years, our planet wobbles on its axis, varies in the tilt of its axis, and experiences change in the shape of its orbit, all in regular long-term cycles of different lengths.

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To measure the degree of impact that a given factor exerts on Earth’s temperature, scientists calculate its radiative forcing, the amount of change in thermal energy that the factor causes. Positive forcing warms the surface, whereas negative forcing cools it. Figure 18.4 shows researchers’ best calculations of the radiative forcing that our planet is experiencing today. When scientists sum up the effects of all factors, they find that Earth is now experiencing overall radiative forcing of about 1.6 watts/m2. This means that today’s planet is receiving and retaining 1.6 watts/m2 more thermal energy than it is emitting into space. (By contrast, the pre-industrial Earth of 1750 was in balance, emitting as much radiation as it was receiving.) This extra amount is equivalent to the power converted into heat and light by 140 incandescent lightbulbs (or 650 CFLs) over a football field. For context, look back at Figure 18.1 and note that Earth is estimated naturally to receive and give off 342 watts/m2 of energy. Although 1.6 may seem like a small proportion of 342, over time it is actually enough to alter climate significantly.

–2

Ca

Whereas greenhouse gases exert a warming effect on the atmosphere, aerosols (p. 475), microscopic droplets and particles, can have either a warming or a cooling effect. Soot particles, or “black carbon aerosols,” generally cause warming by absorbing solar energy, but most other tropospheric aerosols cool the atmosphere by reflecting the sun’s rays. Sulfate aerosols produced by fossil fuel combustion may slow global warming, at least in the short term. When sulfur dioxide enters the atmosphere, it undergoes various reactions, some of which lead to acid precipitation (pp. 491–493). These reactions can form a sulfur-rich aerosol haze in the upper atmosphere that blocks sunlight. For this reason, aerosols released by major volcanic eruptions can exert cooling effects on Earth’s climate for up to several years. This occurred in 1991 with the eruption of Mount Pinatubo in the Philippines (p. 475).

CH 4 ha + N loc 2 O arb + on s

Most aerosols exert a cooling effect

e

Land use

Oz on

Among other greenhouse gases, ozone concentrations in the troposphere have risen roughly 36% since 1750 because of photochemical smog (p. 483). The contribution of halocarbon gases to global warming has begun to slow because of the Montreal Protocol and subsequent controls on their production and use (p. 490). Water vapor is the most abundant greenhouse gas in our atmosphere and contributes most to the natural greenhouse effect. Its concentrations vary locally, but its global concentration has not changed over recent centuries. Because its concentration has not changed, it is not thought to have driven industrial-age climate change.

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25˚ 22˚ Equator

Orbital plane

(a) Axial wobble

(b) Variation of tilt

Earth Sun

Earth

(c) Variation of orbit

Figure 18.5 There are three types of Milankovitch cycles: (a) an axial wobble that occurs on a 19,000- to 23,000-year cycle; (b) a 3-degree shift in the tilt of Earth’s axis that occurs on a 41,000-year cycle; and (c) a variation in Earth’s orbit from almost circular to more elliptical, which repeats every 100,000 years.

These variations, known as Milankovitch cycles, alter the way solar radiation is distributed over Earth’s surface (Figure 18.5). By modifying patterns of atmospheric heating, these cycles trigger long-term climate variation. This includes periodic episodes of glaciation during which global surface temperatures drop and ice sheets advance from the poles toward the midlatitudes, as well as intervening warm interglacial periods.

Solar output   The sun varies in the amount of radiation it emits, over both short and long timescales. However, scientists are concluding that the variation in solar energy reaching our planet in recent centuries has simply not been great enough to drive significant temperature change on Earth’s surface. Estimates place the radiative forcing of natural changes in solar output at only about 0.12 watts/m2—less than any of the anthropogenic causes shown in Figure 18.4. Moreover, solar radiation has been decreasing since the 1970s, not increasing, so it clearly cannot explain Earth’s recent warming trend. Ocean absorption   The oceans hold 50 times more carbon

506

than the atmosphere holds. They absorb carbon dioxide from the atmosphere when this gas dissolves directly in water and when marine phytoplankton use it for photosynthesis. However, the oceans are absorbing less CO2 than we are adding to the atmosphere (see Figure 5.17, p. 140). Thus, carbon absorption by the oceans is slowing global warming but is not preventing it. Moreover, recent evidence indicates that the rate of absorption is decreasing. As ocean water warms, it absorbs less CO2 because gases are less soluble in warmer water—a positive feedback effect (pp. 124–125) that accelerates warming of the atmosphere.

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Ocean circulation  Ocean water exchanges heat with the atmosphere, and ocean currents move energy from place to place. In equatorial regions, such as the area around the Maldives, the oceans receive more heat from the sun and atmosphere than they emit. Near the poles, the oceans emit more heat than they receive. Because cooler water is denser than warmer water, the cooler water at the poles tends to sink, and the warmer surface water from the equator moves to take its place. This is one principle underlying global ocean circulation patterns (p. 442). The oceans’ thermohaline circulation system has influential regional effects (p. 443). For example, it moves warm tropical water northward toward Europe, providing the European continent a far milder climate than it would otherwise have. Scientists are studying whether freshwater input from Greenland’s melting ice sheet might shut down this warm-water flow (p. 443). Such an occurrence would plunge Europe into much colder conditions. Multiyear climate variability results from the El Niño– Southern Oscillation (pp. 443–444), which involves systematic shifts in atmospheric pressure, sea surface temperature, and ocean circulation in the tropical Pacific Ocean. These shifts overlie longer-term variability from a phenomenon known as the Pacific Decadal Oscillation. El Niño and La Niña events alter weather patterns from region to region in diverse ways, often leading to rainstorms and floods in dry areas and drought and fire in moist areas. This leads to impacts on wildlife, agriculture, and fisheries.

FAQ

The climate changes naturally, so why worry about climate change?

Earth’s climate does indeed change naturally across very long periods of time. However, no known natural factors can account for the rapid speed of the change we are experiencing today. Moreover, our civilization has never before experienced the sheer amount of change predicted during this century. The quantity by which the world’s temperature is forecast to rise is greater than the amount of cooling needed to bring on an ice age. Greenhouse gas concentrations are already higher than they’ve been in over 800,000 years, and are still rising. Our entire civilization arose only in the last few thousand years during an exceptionally stable period in Earth’s climate history. Unless we reduce our emissions, we will soon be challenged by climatic conditions the human species has never lived through before.

Studying Climate Change To comprehend any phenomenon that is changing, we must study its past, present, and future. Scientists monitor presentday climate, but they also have devised clever means of inferring past change as well as sophisticated methods to predict future conditions.

Proxy indicators tell us about the past Evidence about paleoclimate, climate in the ancient past, is vital for giving us a baseline against which we can measure

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changes happening in our climate today. To understand paleoclimate, scientists have developed ingenious methods to decipher clues from thousands or millions of years ago by taking advantage of the record-keeping capacity of the natural world. Proxy indicators are types of indirect evidence that serve as proxies, or substitutes, for direct measurement and that shed light on past climate. For example, Earth’s ice caps, ice sheets, and glaciers hold clues to climate history. In frigid areas over the poles and atop high mountains, snow falling year after year for millennia compresses into ice. Over the ages, this ice accumulates to great depths, preserving within its layers tiny bubbles of the ancient atmosphere (Figure 18.6). Scientists can examine the trapped air bubbles by drilling into the ice and extracting long columns, or cores. The layered ice, accumulating season after season over thousands of years, provides a timescale. By studying the chemistry of the ice and the bubbles in each layer in these ice cores, scientists can determine atmospheric

Direct measurements tell us about the present

(b) Micrograph of ice core

Figure 18.6 Scientists drill deep into ancient ice sheets and remove cores of ice. Dr. Gerald Holdsworth of the University of Calgary (a) extracts information about past climates from an ice core. Bubbles trapped in the ice (b) contain small samples of the ancient atmosphere.

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Today we measure temperature with thermometers, rainfall with rain gauges, wind speed with anemometers, and air pressure with barometers, using computer programs to integrate and analyze this information in real time. With these technologies and more, we document in detail the fluctuations in weather day-by-day and hour-by-hour across the globe. As a result, we have gained an understanding of present-day climate conditions in every region of our planet. We also measure the chemistry of the atmosphere and the oceans. Direct measurements of carbon dioxide concentrations in the atmosphere reach back to 1958, when scientist Charles Keeling began analyzing hourly air samples from a monitoring station at Hawaii’s Mauna Loa Observatory. Here, unpolluted, well-mixed air from over vast stretches of ocean blows across the top of Earth’s most massive

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(a) Ice core

composition, greenhouse gas concentrations, temperature trends, snowfall, solar activity, and even (from trapped soot particles) frequency of forest fires and volcanic eruptions during each time period. By extracting ice cores from Antarctica, scientists have now been able to go back in time 800,000 years, reading Earth’s history across eight glacial cycles (see The Science behind the Story, pp. 508–509.) Researchers also drill cores into beds of sediment beneath bodies of water. Sediments often preserve pollen grains and other remnants from plants that grew in the past (as we saw with the study of Easter Island; pp. 24–25). Because climate influences the types of plants that grow in an area, knowing what plants were present can tell us a great deal about the climate at that place and time. Tree rings provide another proxy indicator. The width of each ring of a tree trunk cut in cross-section reveals how much the tree grew in a particular growing season. A wide ring means more growth, generally indicating a wetter year. Long-lived trees such as bristlecone pines can provide records of precipitation and drought going back several thousand years. Tree rings are also used to study fire history, since a charred ring indicates that a fire took place in the region in that year. In arid regions such as the U.S. Southwest, packrat middens are a valuable source of climate data. Packrats are rodents that carry seeds and plant parts back to their middens, or dens, in caves and rock crevices sheltered from rain. In arid locations, plant parts may be preserved for centuries, allowing researchers to study the past flora of the region. Researchers gather data on past ocean conditions from coral reefs (pp. 449–450). Living corals take in trace elements and isotope ratios (p. 42) from ocean water as they grow, and they incorporate these chemical clues, layer by layer, into growth bands in the reefs they build. Proxy indicators often tell us information about local or regional areas. To get a global perspective, scientists need to combine multiple records from various areas. Because the number of available indicators decreases the further back in time we go, estimates of global climate conditions for the recent past tend to be more reliable than those for the distant past.

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The SCIENCE BEHIND THE STORY Reading History in the World’s Longest Ice Core In the most frigid reaches of our planet, snow falling year after year for millennia compresses into ice and stacks up into immense sheets that scientists can mine for clues to Earth’s climate history. The ice sheets of Antarctica and Greenland trap tiny air bubbles, dust particles, and other proxy indicators (p. 507) of past conditions. By drilling boreholes and extracting ice cores, researchers can tap into these valuable archives. Recently, researchers drilled and analyzed the deepest core ever. At a remote and pristine site in Antarctica named Dome C, they drilled down 3270 m (10,728 ft) to bedrock and pulled out more than 800,000 years’ worth of ice. The longest previous ice core (from Antarctica’s Vostok station) had gone back “only” 420,000 years. Ice near the top of these cores was laid down most recently, and ice at the bottom is oldest, so by analyzing ice at intervals along the core’s length, researchers can generate a timeline of environmental change. To date layers of the ice core, researchers first analyze deuterium isotopes (p. 43) to determine the rate of ice accumulation, referencing studies and models of how ice compacts over time. They then calibrate the timeline by matching recent events in the chronology (for example, major volcanic eruptions) with independent data sets from previous cores, tree rings, and other sources.

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An EPICA researcher prepares a Dome C ice core sample for analysis.

Dome C, a high summit of the Antarctic ice sheet, is one of the coldest spots on the planet, with an annual mean temperature of –54.5°C (–98.1°F). The Dome C ice core was drilled by the European Project for Ice Coring in Antarctica (EPICA), a consortium of researchers from 10 European nations. In 2004, this team of 56 researchers published a paper in the journal Nature, reporting data across 740,000 years. The researchers obtained data on surface air temperature by measuring the ratio of deuterium isotopes to normal hydrogen in the ice, because this ratio is temperature-dependent. From 2005 to 2008, five followup papers in the journals Science and Nature reported analyses of greenhouse gas concentrations from the EPICA ice core and extended the gas and temperature data back to

mountain. These data show that atmospheric CO2 concentrations have increased from 315 ppm in 1958 to 396 ppm in 2013 (Figure 18.7). Direct measurements of climate variables such as temperature and precipitation extend back in time somewhat further. Precise and reliable thermometer measurements cover more than a century. Scientists can also infer past climate conditions from historical records of economic activities affected by climate. Fishers have recorded the timing of sea ice formation, and winemakers have kept meticulous records of precipitation and the length of the growing season.

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cover all 800,000 years. By analyzing air bubbles trapped in the ice, the researchers quantified atmospheric concentrations of carbon dioxide and methane (red line and green line, respectively, in Figure 1). These data show that by emitting these greenhouse gases since the industrial revolution, we have brought their atmospheric concentrations well above the highest levels they reached naturally any time in the last 800,000 years. Today’s carbon dioxide spike is too recent to show up in the ice core, but its concentration (of 396 ppm in 2013) is far above previous maximum values (of ~300 ppm) shown in the red line of the figure. These data reveal that we as a society have brought ourselves deep into uncharted territory. The EPICA results also confirm that temperature swings in the past

Accurate records of all these types extend back, at most, a few hundred years.

Models help us predict the future To understand how climate systems function and to predict future climate change, scientists simulate climate processes with sophisticated computer programs. Climate models are programs that combine what is known about atmospheric circulation, ocean circulation, atmosphere–ocean interactions, and feedback cycles to simulate climate processes

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Figure 1 Data from the EPICA ice core reveal changes across 800,000 years. Shown are surface temperature (black line), atmospheric methane concentration (green line), and atmospheric carbon dioxide concentration (red line). Concentrations of CO2 and methane rise and fall in tight correlation with temperature. Today’s current values are included at the top right of the graph, for comparison. Adapted by permission of Macmillan Publishers Ltd: Brook, E. 2008. Paleoclimate: Windows on the greenhouse. Nature 453: 291-292, Fig 1a. www.nature.com.

cycles (pp. 505–506). The complex interplay of the Milankovitch cycles produces periodic temperature fluctuations on Earth resulting in periods of glaciation (when temperate regions of the planet are covered in ice) and in warm interglacial periods. The Dome C ice core spans eight glacial cycles. Other findings from the ice core are not easily explained. Intriguingly, the

(see THE SCIENCE BEHIND THE STORY, pp. 512–513). This requires manipulating vast amounts of data with complex mathematical equations—a task not possible until the advent of modern computers. Climate modelers essentially provide starting information to the model, set up rules for the simulation, and then let it run. Researchers strive for accuracy by building in as much information as they can from what is understood about how the climate system functions. They then test the efficacy of a model by entering past climate data and running the model toward the present. If a model accurately reconstructs current

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climate, based on well-established data from the past, then we have reason to believe that it simulates climate mechanisms realistically and that it may accurately predict future climate. Plenty of challenges remain for climate modelers, because Earth’s climate system is so complex and because many uncertainties remain in our understanding of feedback processes. Yet as scientific knowledge of climate improves, as computing power intensifies, and as we glean enhanced data from proxy indicators, climate models are improving in resolution and are predicting climate change region by region across the world.

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were tightly correlated with concentrations of greenhouse gases (compare the top two datasets in Figure 1 with the temperature dataset at bottom). This finding bolsters the scientific consensus that greenhouse gas emissions are causing our planet to warm today. Also clear from the data is that temperature has varied with swings in solar radiation due to Milankovitch

early glacial cycles differ from the recent cycles (see the black line in Figure 1). In the recent cycles, glacial periods are long, whereas interglacial periods are brief, with a rapid rise and fall of temperature. Interglacials thus appear on the graph as tall thin spikes. In older glacial cycles, the glacial and interglacial periods are of more equal duration, and the interglacials are not as warm. This change in the nature of glacial cycles had been noted before by researchers working with oxygen isotope data from the fossils of marine organisms. But why cycles should differ before and after the 450,000-year mark, no one knows. Today polar scientists are searching for a site that might provide an ice core stretching back more than 1 million years. At that time, data from marine isotopes tell us that glacial cycles switched from a periodicity of roughly 41,000 years (conforming to the influence of planetary tilt) to intervals of about 100,000 years (more similar to orbital changes). An ice core that captures cycles on both sides of the 1-million-year divide might help clarify the influence of Milankovitch cycles or perhaps offer other explanations. The intriguing patterns revealed by the Dome C ice core show that we still have plenty to learn about our complex climate history. However, the clear relationship between greenhouse gases and temperature evident in the EPICA data suggest that if we want to prevent sudden global warming, we will need to reduce our society’s greenhouse emissions.

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Atmospheric concentration of CO2 (ppm)

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Figure 18.7 Atmospheric concentrations of carbon dioxide are rising steeply. Direct long-term measurements began in 1958, when Charles Keeling started collecting these data at Hawaii’s Mauna Loa Observatory. The jaggedness of the trend reflects seasonal variation: the Northern Hemisphere has more land area and vegetation than the Southern Hemisphere, so more CO2 is absorbed during the northern summer, when plants in the north are photosynthetically active. Data from National Oceanic and Atmospheric Administration, Earth System Research Laboratory, Global Monitoring Division, 2013.

Current and Future Trends and Impacts It seems that virtually everyone is noticing changes in the climate these days. Maldives fishermen note the seas encroaching on their home island. Texas ranchers suffer a multiyear drought. Florida homeowners find it difficult to obtain insurance against hurricanes and storm surges. New Yorkers, Bostonians, Chicagoans, and Los Angelenos face one unprecedented weather event after another. Extreme weather events are indeed part of a real pattern backed by a tremendous volume of scientific evidence. Climate change has already had numerous impacts on the physical properties of our planet, on organisms and ecosystems, and on human well-being. If we continue to emit greenhouse gases into the atmosphere, the consequences of climate change will grow more severe.

researchers to study. As a result, the scientific literature today is replete with independent published studies, and we have gained a rigorous and reliable understanding of most aspects of climate change. To make this vast and growing research knowledge accessible to policymakers and the public, various bodies have taken up the task of reviewing and summarizing it. For instance, the U.S. Global Change Research Program publishes periodic assessments of climate change’s impacts in the United States (p. 522). For the world as a whole, the I­ ntergovernmental Panel on Climate Change (IPCC) plays this role. This international panel consists of many hundreds of scientists and governmental representatives. Established in 1988 by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO), the IPCC was awarded the Nobel Peace Prize in 2007 for its work in informing the world of the trends and impacts of climate change. In that year the IPCC released its Fourth Assessment Report. This report summarized many thousands of scientific studies, and it documented observed trends in surface temperature, precipitation patterns, snow and ice cover, sea levels, storm intensity, and other factors. It also predicted future changes in these phenomena after considering a range of potential scenarios for future greenhouse gas emissions. The report addressed impacts of current and future climate change on wildlife, ecosystems, and society. Finally, it discussed strategies we might pursue in response to climate change. Table 18.2 summarizes some of the IPCC report’s major observed and predicted trends and impacts. Like all science, the IPCC’s reports deal in uncertainties, so their authors take great care to assign statistical probabilities to conclusions and predictions. Moreover, the IPCC’s estimates regarding impacts on society are conservative, because its scientific conclusions need to be approved by representatives of the world’s national governments, some of which are reluctant to move away from a fossil-fuel-based economy. Since the publication of the Fourth Assessment Report, many aspects of climate change have grown more severe faster than predicted. It appears that the report underestimated many changes, while overestimating very few. As scientists around the world continue to monitor and model our changing climate, new research is being completed faster than ever. The IPCC’s Fifth Assessment Report is due out in a series of four documents from late 2013 through late 2014. You and your instructor may wish to download these new reports (they will be publicly accessible online) and explore their coverage of the latest research findings.

Scientific evidence for climate change is extensive

Temperatures continue to rise

For years, scientists have studied the many aspects of climate change in enormous breadth, depth, and detail. Labs and government agencies have been continuously monitoring climate variables with everything from thermometers to satellites, building up detailed long-term databases for

Average surface temperatures on Earth have risen by about 0.9°C (1.6°F) in the past 100 years (Figure 18.8). These include increases both in air temperature over land and in sea surface temperature. Most of this century’s increase has occurred recently, just since 1975. The numbers of

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Table 18.2 Observed and Predicted Trends and Impacts of Climate Change, from IPCC Fourth Assessment Report GLOBAL PHYSICAL INDICATORS Average surface temperature increased 0.74°C (1.33°F) in the past 100 years, and will rise 1.8–4.0°C (3.2–7.2°F) in the 21st century. Oceans absorbed >80% of heat added to the climate system and warmed to depths of at least 3000 m (9800 ft). Glaciers, snow cover, ice caps, ice sheets, and sea ice are melting and will continue, contributing to sea level rise.

extremely hot days and heat waves have increased globally, whereas the number of cold days has decreased. According to the WMO, the 18 warmest years on record since global measurements began 150 years ago have all been since 1990. The decade from 2001–2010 was the hottest ever recorded, and since the 1960s each decade has been warmer than the last. In fact, consider this: If you were born after 1985, you have never in your life lived through a month with average global temperatures lower than the 20th-century average.

Ocean water became more acidic by about 0.1 pH unit and will decrease in pH by 0.14–0.35 units more by century’s end. Storm surges increased, and will increase further. Carbon uptake by terrestrial ecosystems will peak by mid-century, then weaken or reverse, amplifying climate change. REGIONAL PHYSICAL INDICATORS Arctic areas warmed fastest. Future warming will be greatest in the Arctic and greater over land than over water. Summer Arctic sea ice thinned by 7.4% per decade since 1978. Precipitation will increase at high latitudes and decrease at subtropical latitudes, making wet areas wetter and dry ones drier.

Average global temperature (°F)

Sea level rose by an average of 17 cm (7 in.) in the 20th century and will rise 18–59 cm (7–23 in.) in the 21st century.

58.0

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Droughts became longer, more intense, and more widespread since the 1970s, especially in the tropics and subtropics. Droughts and flooding will increase, leading to agricultural losses.

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Hurricanes have intensified in the North Atlantic since 19701 and will continue to intensify.

Farmers and foresters have had to adapt to altered growing seasons and disturbance regimes. Temperate-zone crop yields will rise until 3°C (5.4°F) warming. In dry tropics and subtropics, crop productivity will fall. Impacts on biodiversity will cause losses of food, water, and other ecosystem goods and services. Sea level rise will displace people from islands and coasts. Economic costs will outweigh benefits. Costs could average 1–5% of GDP globally for 4°C (7.2°F) of warming.

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Poorer nations and communities are suffering more. Human health will suffer as increased warm-weather health hazards outweigh decreased cold-weather health hazards. BIOLOGICAL INDICATORS Species ranges are shifting toward the poles and upward in elevation, and they will continue to shift. The timing of seasonal phenomena (such as migration and breeding) is shifting and will continue to shift. About 20–30% of species studied so far could face extinction. Corals will suffer further bleaching and ocean acidification. Observed phenomena are in plain text. Predicted future phenomena are in italicized text. This table expresses mean estimates only. (The IPCC report provides ranges and statistical probabilities as well.) Data from IPCC, 2007. Fourth assessment report.

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(b) Northern Hemisphere temperature over the past 1000 years

Figure 18.8 Global temperatures have risen sharply in the past century. Data from thermometers (a) show changes in Earth’s average surface temperature since 1880. Since 1976, every single year has been warmer than average. In (b), proxy indicators (blue line) and thermometer data (red line) together show average temperatures in the Northern Hemisphere over the past 1000 years. The gray-shaded zone represents the 95% confidence range. Data from (a) NOAA National Climatic Data Center as presented

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Melting of mountain glaciers will reduce water supplies to millions.

Departures in temperature (°C) from the 1961–1990 average

SOCIAL INDICATORS

in U.S. Global Change Research Program, 2013. National climate assessment. Draft for public review; and (b) IPCC, 2001. Third assessment report.

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The SCIENCE BEHIND THE STORY How Do Climate Models Work?

A researcher manipulates a 3D cloud simulator to help in modeling the climatic influence of clouds.

to make them behave realistically in space and time. In the real climate system, time is continuous and spatial effects reach down to the level of molecules interacting with one another. But the virtual reality of climate models cannot be so deep and precise—there is simply not enough computer power available. Instead, modelers approximate reality by dividing time up into periods (called time steps) and by dividing the Earth’s surface up into cells or boxes according to a grid (called grid boxes) (Figure 2). Each grid box contains land, ocean, or atmosphere, much like a digital photograph is comprised of discrete pixels of certain colors. The grid boxes are arrayed in a three-dimensional layer by latitude and longitude, or in equalsized polygons.

Outgoing Incoming heat solar energy Transition from solid to vapor Evaporative and heat exchanges

Cumulus clouds

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Ocean currents, temperature, and salinity

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Climate models are indispensable for modern climate science—and they are increasingly vital for our society as they allow us to make informed predictions about what conditions will confront us in the future. Yet to most of us, a climate model is a mysterious black box. So how exactly do scientists go about creating a climate model? The output we often see from climate models are colorful maps or data-rich graphs and charts, but the scientist puts into the model a long series of mathematical equations. These equations describe how various components of Earth’s systems function. Some equations are derived from physical laws such as those on the conservation of mass, energy, and momentum (p. 41). Others are derived from observational and experimental data on the physical, chemical, and biological aspects of our planet. Converted into computing language, these equations are integrated with information about Earth’s landforms, hydrology, vegetation, and atmosphere (Figure 1). All these types of information are the building blocks of a climate model. The number of these building blocks determines the complexity of the model. Earth’s climate system is mind-bogglingly complex, and modelers will never capture all the factors that influence climate. Yet as computers become more powerful and

models more sophisticated, they are incorporating more and more of the factors—major and minor, direct and indirect—that affect climate. To handle the complexity, generally a model is composed of multiple submodels. Essentially, submodels for components of the Earth system—ocean waters, sea ice, glaciers, forests, deserts, troposphere, stratosphere—are each built and are then combined into a global model. Years ago when models first coupled atmosphere and ocean components together, they were called “coupled” models. This is standard in today’s far more complex general circulation models, or global climate models (which share the acronym GCM). For a model to function, all the building blocks must be given equations

Upwelling and downwelling

Figure 1 Climate models incorporate a diversity of natural factors and processes. Anthropogenic factors can then be added in.

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1.0 Global temperature change (°C)

The finer-scale the grid, the greater resolution the model will have, and the better it will be able to predict results region by region. However, more resolution means more computing power is needed, and climate models already strain the most powerful supercomputing networks. The best climate models today feature dozens of grid boxes piled up from the bottom of the ocean to the top of the atmosphere, with each grid box measuring a few dozen miles wide, and time measured in periods of just minutes. Once the grid is established, the processes that drive climate are assigned to each grid box, with their rates parceled out among the time steps. The model lets the grid boxes interact through time by means of the flux of materials and energy into and out of each grid box. Once modelers have input all this information, learned from our study of Earth and the climate system, they let the model run through time and simulate climate, from the past through the present and into the future. If the computer simulation accurately reconstructs past and present climate, then that gives us confidence that it

Figure 3 Models that incorporate both natural and anthropogenic factors predict observed climate trends best.

Observed data All factors Anthropogenic factors Natural factors

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may predict future climate accurately as well. A number of studies have compared model runs that include only natural processes, model runs that include only human-generated processes, and model runs that combine both. Repeatedly these studies have found that the model runs that incorporate both human and natural processes are the ones that fit the real-world climate

Arnold J., 2010. Global climate change: Convergence of disciplines. Sinauer Associates, Sunderland, Mass.

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Figure 2 Climate models divide Earth’s surface into a layered grid. Each grid box represents land, air, or water, and interacts with adjacent grid boxes via the flux of materials and energy. Adapted from Bloom,

observations the best (Figure 3). This supports the idea that human activities are influencing our climate. The major human influence on climate is our emission of greenhouse gases, and modelers need to select values to enter for future emissions if they want to predict future climate. Generally they will run their simulations multiple times, each time with a different emission amount according to a specified scenario. Differences between the results from such scenarios tell us what influence these different actions would have. You can see results from such a comparison in Figure 18.24 (p. 525). Throughout this chapter, you will see figures that show results of various models. In crafting its assessment reports, the IPCC consults nearly two dozen major models, considers the strengths and weaknesses of each, and presents the best summary its authors can muster. Researchers are constantly testing and evaluating their climate models. They continually improve them by incorporating what is learned from new research and by taking advantage of what increasingly powerful computing technologies will allow. As their work proceeds, we can expect better and better predictions about what climate conditions we will encounter in the future.

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Precipitation is changing, too

Change (ºF) >1.5 1.0 to 1.5 0.5 to 1.0 0.0 to 0.5

-0.5 to 0.0 -1.0 to -0.5 -1.5 to -1.0 20% decrease 10–20% decrease 5–10% decrease 5% decrease to 5% increase 5–10% increase 10–20% increase >20% increase

(June–Aug.) is projected to change for the decade 2090–2099, relative to 1980–1999. Browner shades indicate less precipitation, and bluer shades indicate more. White indicates areas where models did not agree. This map was generated using an intermediate emissions scenario involving an average global temperature rise of 2.8°C (5.0°F) by 2100. Data from IPCC, 2007. Fourth assessment report. Climate Change 2007: Synthesis Report, Fig 3.3.

Cool weather

Typ ica l je Warm t st rea weather m Weather systems move west to east at normal rate

ms tuck in

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Weather systems are held in place, creating prolonged bouts of extreme weather

(b) Jet stream in March 2012

Figure 18.12 Changes in the jet stream can cause extreme weather events. When Arctic warming slows the jet stream, it departs from its normal configuration (a) and goes into a blocking pattern (b) that stalls weather systems in place, leading to extreme weather events. The blocking pattern shown here brought recordbreaking heat to the eastern United States in March 2012.

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Persistent cold weather

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(a) Normal jet stream

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became stuck in place (see Figure 18.12b). Atmospheric blocking patterns also were associated with the 2011 drought in Texas, the 2012 wildfires in Colorado, both floods and heat waves in Europe, and various other extreme weather events. Additional independent research has supported Francis and Vavrus’s jet stream hypothesis, and if it continues to be strengthened by further data, it would provide a valuable explanatory mechanism for how climate change brings extreme weather to North America and Europe.

Lo

Moreover, a 2011 study by climate scientist James Hansen and others revealed that summer temperatures since the 1950s have become not only warmer, but also more variable. As a result, extreme summers (some of them unusually cool, more of them unusually warm) have occurred more and more frequently. Scientists are not the only ones to notice the increase in extreme weather events. The insurance industry is finely attuned to such patterns, since insurers are the ones paying out money each time a major storm, drought, or flood hits. The major German insurer Munich Re calculated that from 1980 to 2011, extreme weather events causing losses increased fully 5 times in North America. They rose by 4 times in Asia, 2.5 in Africa, 2 in Europe, and 1.5 in South America. And this was not even counting the events of 2012. Researchers have long conservatively stated that although climate trends influence the probability of what the weather may be like on any given day, no single particular weather event can reliably be attributed to climate change. However, as we gain a better understanding of what causes extreme weather events, it is starting to become possible to link certain weather events to climate change. In 2012, a research paper by Jennifer Francis of Rutgers University and Stephen Vavrus of the University of Wisconsin outlined a mechanism that may explain how global warming may commonly lead to more extreme weather. Their analysis indicated that because warming has been greater in the Arctic than at lower latitudes, this has weakened the intensity of the Northern Hemisphere’s polar jet stream. This jet stream is a high-altitude air current that blows west-to-east and meanders north and south, influencing much of the weather from day to day across North America and Eurasia. As the jet stream slows down, its meandering loops become longer. These long lazy loops move west to east more slowly, and may get stuck in a north–south orientation for long periods of time. This is what meteorologists call an atmospheric blocking pattern, because it can block the eastward movement of weather systems and hold them in place (Figure 18.12). When this happens, a rainy system that would normally move past a city in a day or two might instead be held in place for several days, resulting in flooding. Or dry conditions over a farming region might last two weeks instead of two days, causing a drought. Cold spells last longer, and hot spells last longer, too. Indeed, the record-breaking heat wave that roasted the eastern United States in March 2012 resulted after the jet stream

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Melting ice has far-reaching effects

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As the world warms, mountaintop glaciers are disappearing (Figure 18.13). Between 1980 and 2011, the World Glacier Monitoring Service estimates that the world’s glaciers on average have each lost mass equivalent to 15 m (49 ft) vertical thickness of water. Many glaciers on tropical mountaintops have disappeared already. In Glacier National Park in Montana, only 25 of 150 glaciers present at the park’s inception remain, and scientists estimate that by 2030 even these will be gone. Mountains accumulate snow in the winter and release meltwater gradually during the summer. Over one-sixth of the world’s people live in regions that depend on mountain meltwater. As warming temperatures diminish mountain glaciers, this will reduce summertime water supplies to millions of people, likely forcing whole communities to look elsewhere for water, or to move. Warming temperatures are also melting vast amounts of ice in the Arctic. Recent research reveals that the immense ice sheet that covers Greenland is melting faster and faster. At the other end of the world, in Antarctica, coastal ice shelves the size of Rhode Island have disintegrated as a result of contact with warmer ocean water. At the same time, increased precipitation is supplying Antarctica’s interior with extra snow, making its ice sheet thicker even as it loses ice around its edges. One reason warming is accelerating in the Arctic is that as snow and ice melt, darker, less reflective surfaces (such as bare ground and pools of meltwater) are exposed, and Earth’s albedo, or capacity to reflect light, decreases. As a result, more of the sun’s rays are absorbed at the surface, fewer reflect back into space, and the surface warms. In a process of positive feedback, this warming causes more ice and snow to melt, which in turn causes more absorption of radiation and more warming (see Figure 5.1b, p. 124). Scientists predict that snow cover, ice sheets, and sea ice will continue to diminish near the poles. As Arctic sea ice disappears, new shipping lanes are opening up for commerce, and governments and companies are rushing to exploit newly accessible underwater oil and mineral reserves. Already, Russia, Canada, the United States, and other nations are jockeying for position, using new survey data to try to lay claim to regions of the Arctic as the ice melts. Warmer temperatures in the Arctic are also causing permafrost (permanently frozen ground) to thaw. As ice crystals within permafrost melt, the thawing soil settles, destabilizing buildings, pipelines, and other infrastructure. When permafrost thaws, it also can release methane that has been stored

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(b) Jackson Glacier in 2009 Mean cumulative mass of ice (water equivalent) lost, in meters

(a) Jackson Glacier in 1911

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(c) The world’s major glaciers are losing mass

Figure 18.13 Glaciers are melting rapidly as global warming proceeds. The Jackson Glacier in Glacier National Park, Montana, retreated substantially between (a) 1911 and (b) 2009. The graph (c) shows average declines in mass in 37 of the world’s major glaciers monitored since 1980. Data from World Glacier Monitoring Service.

for thousands of years. Because methane is a potent greenhouse gas, its release acts as a positive feedback mechanism that intensifies climate change. No one knows how much methane lies beneath Arctic permafrost, but it is a very large amount, and some researchers worry that its release could drive climate change beyond our control.

Rising sea levels may affect hundreds of millions of people As glaciers and ice sheets melt, increased runoff into the oceans causes sea levels to rise. Sea levels also are rising because ocean water is warming, and water expands in volume as its temperature increases. In fact, recent sea level rise has resulted primarily from the thermal expansion of seawater. Worldwide, average sea levels have risen 21 cm (8.3 in.) in the past 130 years (Figure 18.14). Studies indicate that seas rose by 1.8 mm/year from 1961 to 2003 and 2.9–3.4 mm/year from 1993 to 2010. These numbers represent vertical rises in water level, and on most coastlines a vertical rise of a few inches means many feet of horizontal incursion inland. Higher sea levels lead to beach erosion, coastal flooding, intrusion of salt water into aquifers, and greater impacts from storm surges. A storm surge is a temporary and localized rise in sea level brought on by the high tides and winds associated with storms. The higher that sea level is to begin with, the further inland a storm surge can reach. In 1987, unusually high

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Sea level rise (mm)

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~57% ~28% ~15%

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Tide gauge data Satellite data Statistical uncertainty

0 –50 1870

2000

1950 Year

1900

Figure 18.14 Global average sea level has risen over 200 mm (7.9 in.) since 1870. Data from tide gauges and satellite observations each confirm the same trend. Thermal expansion of water accounts for most sea level rise. Data from Intergovernmental Panel on Climate Change, 2007. Fourth assessment report; and CSIRO.

Sea level rise (inches)

waves struck the Maldives and triggered a campaign to build a large seawall around Malé, the nation’s capital. “The Great Wall of Malé” is intended to protect buildings and roads by dissipating the energy of incoming waves during storm surges. On December 26, 2004, the Maldives was hit by a massive tsunami (pp. 60–61) that devastated coastal areas throughout the Indian Ocean. The tsunami was triggered by an earthquake, not by climate change—yet as sea level rises, the damage that such natural events can inflict increases con-

Figure 18.15 Climate change contributes to the power and reach of storms like Hurricane Sandy. Damage was extensive in the superstorm’s aftermath. The map shows areas in New York City flooded by the storm. The graph shows sea level rise in New York City in the past century. Map data from The New York Times as

10

adapted from federal agencies; graph data from New York City Panel on Climate Change 2010.

0 -6 1900

siderably. The tsunami killed 100 Maldives residents and left 20,000 homeless. Schools, boats, tourist resorts, hospitals, and transportation and communication infrastructure were damaged or destroyed. The World Bank estimated that direct damage in the Maldives totaled $470 million, an astounding 62% of the nation’s gross domestic product (GDP). Indirect damage from soil erosion, saltwater contamination of aquifers, and other impacts continues to cause further economic losses today. The Maldives has actually fared better against sea level rise than many other island nations. It has seen sea levels rise about 3 mm per year since 1990, but most Pacific islands are experiencing greater rises in sea level, some up to 9 mm/year. Regions experience differing amounts of sea level change because land may be rising or subsiding naturally, depending on local geological conditions. In the United States, Hurricane Sandy demonstrated the impact that storm surges can have even on highly developed metropolitan areas (Figure 18.15). This massive hurricane battered the eastern part of the nation in October 2012, causing over $60 billion in damage and leaving over 130 people dead and thousands homeless. New York City and the New Jersey coast bore the brunt of the storm. In New Jersey, thousands of beach houses were destroyed, iconic boardwalks were washed away, and whole coastal communities were inundated with salt water and tons of sand thrown up by the storm. In Manhattan, economic activity ground to a halt as tunnels and

1950 Year

2010

Area flooded Severe damage Completely destroyed

Bronx

Manhattan Hoboken Newark

Queens NEW YORK CITY

Elizabeth Staten Island

Brooklyn The Rockaways

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Jersey City

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subway stations flooded and countless vehicles and buildings suffered damage. A fire broke out amid flooded homes in Queens and destroyed an entire neighborhood. Hurricane Sandy was not directly and solely caused by global warming, but in a statistical sense it was certainly facilitated and strengthened by it. The warmer ocean water that has resulted from climate change increases the chances of large and powerful hurricanes. The warmer atmosphere retains more moisture that a hurricane can dump onto land. A blocking pattern in the jet stream contributed to Sandy’s energy. And higher sea levels magnify the damage caused by storm surges. In Sandy’s aftermath, an apt metaphor spread across the Internet: When a baseball player takes steroids and starts hitting more home runs, you can’t attribute any one particular home run to the steroids, but you can conclude that steroids were responsible for the increase in home runs. Our greenhouse gas emissions are like steroids that are supercharging our climate and making extreme weather events more likely. Seven years before Sandy, the United States was hit by an even more costly storm. Hurricane Katrina (followed by Hurricane Rita) slammed into New Orleans and the Gulf Coast in 2005, killing more than 1800 people and causing over $80 billion in damage. Outside New Orleans today, marshes of the Mississippi River delta are being lost rapidly as rising seas eat away at coastal vegetation (pp. 407–408). These coastal wetlands are also being lost because dams upriver hold back silt that once maintained the delta, because petroleum extraction has caused land to subside, and because salt water is encroaching up channelized waterways, killing freshwater plants. All told, more than 2.5 million ha (1 million acres) of Louisiana’s coastal wetlands have vanished since 1940. Continued wetland loss will deprive New Orleans (much of which is below sea level, safeguarded only by levees) of protection against future storm surges. Across the United States, 53% of the population lives in coastal counties, so a great many people are vulnerable to impacts from storm surges. Different stretches of coast are experiencing different degrees of sea level rise (Figure 18.16). In its 2007 assessment report, the IPCC predicted that mean sea level would rise 18–59 cm (7–23 in.) higher by the end of the 21st century, depending on our level of emissions. However, new research is finding that Greenland’s ice is melting at an accelerating rate. If polar melting continues to accelerate, then sea levels will rise more quickly. Indeed, in 2009 a European research team used a different approach to estimate future sea level rise by carefully examining the rates at which it has risen and fallen in the past. This team forecast that sea level would rise 0.9–1.3 meters by the year 2100. Some researchers are now using a figure of a 1-meter rise to assess risk. Jeremy Weiss of the University of Arizona and his colleagues have pointed out that 3.9 million Americans live within 1 vertical meter of the high tide line, and they estimate that a 1-m rise threatens 180 U.S. cities with losing an average of 9% of their land area. Miami, Tampa, New Orleans, and Virginia Beach were judged most at risk (Figure 18.17). Whether sea levels this century rise 18 cm or 1 m, hundreds of millions of people will be displaced or will need to

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Sea level trends mm/yr -3 to 0 0 to 3 3 to 6 6 to 9 9 to 12

Figure 18.16 Sea level is rising at different rates along stretches of the U.S. coast. Rates are highest where land is subsiding. Most vulnerable to future damage are the Gulf Coast and the central Atlantic Seaboard. Data from National Oceanic and Atmospheric Administration.

invest in costly efforts to protect against high tides and storm surges. Densely populated regions on low-lying river deltas, such as Bangladesh, would be most affected. So would storm-prone regions such as Florida, coastal cities such as Houston and Charleston, and areas where land is subsiding, such as the U.S. Gulf Coast. Many Pacific islands would need to be evacuated. Already some nations such as Tuvalu and the

FLORIDA Fort Lauderdale

Pembroke Pines Miramar

Hollywood

Hialeah Miami Beach MIAMI

10 km

Figure 18.17 Miami, Florida, is one of many U.S. cities vulnerable to sea level rise. Shown are areas of the Miami region that would be flooded by a 1-meter rise in sea level. Data from Jeremy Weiss, Environmental Studies Laboratory, Department of Geosciences, University of Arizona.

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Maldives fear for their very existence. In the meantime, island nations such as the Maldives are likely to suffer shortages of fresh water as rising seas bring salt water into aquifers. The contamination of groundwater and soils by seawater also threatens coastal areas such as Tampa, Florida, which depend on small lenses of fresh water that float atop saline groundwater.

Weighing the Issues Environmental Refugees The Pacific island nation of Tuvalu has been losing 9 cm (3.5 in.) of elevation per decade to rising seas. Appeals from Tuvalu’s 11,000 citizens were heard by New Zealand, which began accepting “environmental refugees” from Tuvalu in 2003. Do you think the rest of the world should grant such environmental refugees international status and assume some responsibility for taking care of them? Do you think a national culture can survive if its entire population is relocated? Think of the tens of thousands of refugees from Hurricane Katrina. How did their lives and culture fare in the wake of that tragedy?

modifying all manner of biological phenomena that are regulated by temperature. In the spring, plants are now leafing out earlier, insects are hatching earlier, birds are migrating earlier, and animals are breeding earlier. These shifts can create mismatches in seasonal timing with phenomena that are regulated by other factors. For example, European birds known as great tits had evolved to time their breeding so as to raise their young when caterpillars peak in abundance. Now caterpillars are peaking earlier, but the birds have been unable to adjust, and fewer young birds are surviving. Biologists are also recording spatial shifts in the ranges of organisms, as plants and animals move toward the poles or upward in elevation (i.e., toward cooler regions) as temperatures warm (Figure 18.18). As these trends continue, some organisms will not be able to cope, and the IPCC estimates that as many as 20–30% of all plant and animal

Center of Purple Finch range shifted 700 km north in 40 years

Climate change threatens coral reefs

Climate change affects organisms and ecosystems As the coral reef crisis shows, changes in Earth’s physical systems have consequences for living things. Organisms are adapted to their environments, so they are affected when we alter those environments. As global warming proceeds, it is

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(a) Birds are moving north

Pikas are disappearing from mountains after being forced upwards

(b) Pikas are being forced upslope

Figure 18.18 Animal populations are shifting toward the poles and upward in elevation. Fully 177 out of 305 North American bird species have shifted their winter ranges significantly northward in the past 40 years, according to a 2009 analysis of Christmas Bird Count data by National Audubon Society researchers. The purple finch (a) has shown the greatest shift; its center of abundance moved 697 km (433 mi) north. Montane animals such as the pika (b), a unique mammal that lives at high elevations in western North America, are being forced upslope (into more limited habitat) as temperatures warm. Many pika populations in the Great Basin have disappeared from mountains already.

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Maldives residents also worry about damage to their coral reefs (pp. 449–450), marine ecosystems that are critical for their economy. Coral reefs provide habitat for important fish that are consumed locally and exported. They offer snorkeling and scuba diving sites for tourism. Reefs also reduce wave intensity, protecting coastlines from erosion. Around the world, rising seas are eating away at the coral reefs, mangrove forests, and salt marshes that serve as barriers protecting our coasts (pp. 448–449). Climate change poses two additional threats to coral reefs. First, warmer waters contribute to coral bleaching (p. 449), which kills corals. Second, enhanced CO2 concentrations in the atmosphere alter ocean chemistry, leading to ocean acidification (pp. 444, 446–447). As ocean water absorbs atmospheric CO2, it becomes more acidic, and this impairs the ability of corals and other organisms to build exoskeletons of calcium carbonate. Indeed, ocean acidification and the potential loss of coral reefs worldwide (explained in The Science behind the Story, Chapter 16, pp. 446–447) threaten to become one of the most serious and far-reaching impacts of global climate change. The oceans have already decreased by 0.1 pH unit, and they are predicted to decline in pH by 0.14–0.35 more units over the next 100 years. This could easily be enough to destroy most of our planet’s living coral reefs. Such destruction could be catastrophic for marine biodiversity and fisheries, because so many organisms depend on living coral reefs for food and shelter.

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species could be threatened with extinction. Trees may not be able to shift their distributions fast enough. Rare species may be forced out of preserves and into developed areas where they cannot survive. Animals and plants adapted to mountainous environments may be forced uphill until there is nowhere left to go. Effects on plant communities comprise an important component of climate change, because by drawing in CO2 for photosynthesis, plants act as reservoirs for carbon. If higher CO2 concentrations enhance plant growth, then more CO2 might be removed from the air, helping to mitigate carbon emissions, in a process of negative feedback. However, if climate change decreases plant growth (through drought, fire, or disease, for instance), then carbon flux to the atmosphere could increase, in a process of positive feedback. Free-Air CO2 Enrichment (FACE) experiments are revealing complex answers, showing that extra carbon dioxide can bring both positive and negative results for plant growth (see The Science behind the Story, Chapter 5, pp. 142–143). In regions where precipitation and stream flow increase, erosion and flooding will pollute and alter aquatic systems. In regions where precipitation decreases, lakes, ponds, wetlands, and streams will shrink. The many impacts of climate change on ecological systems will diminish the ecosystem goods and services we receive from nature and that our societies depend on, from food to clean air to drinking water.

decrease crop yields. Withered corn fields like this one in Illinois were a common sight in 2012, when the U.S. government declared 1000 counties across 26 states to be disaster areas due to drought.

droughts brought about by a strong El Niño in 1997–1998 allowed immense forest fires to destroy vast areas of rainforest in Indonesia, Brazil, and Mexico. In North America, forest managers increasingly find themselves battling catastrophic fires, invasive species, and insect and disease outbreaks. Catastrophic fires are caused in part by decades of fire suppression (p. 339) but are also promoted by longer, warmer, drier fire seasons (see Figure 12.18a, p. 339). Milder winters and hotter, drier summers are promoting outbreaks of bark beetles that are destroying millions of acres of trees (see Figure 12.18b, p. 339).

Climate change affects society

Health  As climate change proceeds, we will face more

Drought, flooding, storm surges, and sea level rise have already taken a toll on the lives and livelihoods of millions of people. However, climate change will have still more consequences. These include impacts on agriculture, forestry, health, and economics.

heat waves—and heat stress can cause death, especially among older adults. A 1995 heat wave in Chicago killed at least 485 people, and a 2003 heat wave in Europe killed 35,000 people. A warmer climate also exposes us to other health problems:

Agriculture  For some crops in the temperate zones,

• Respiratory ailments from air pollution, as hotter temperatures promote formation of photochemical smog (p. 483) • Expansion of tropical diseases, such as dengue fever, into temperate regions as vectors of infectious disease (such as mosquitoes) move toward the poles • Disease and sanitation problems when floods overcome sewage treatment systems • Injuries and drowning if storms become more frequent or intense

moderate warming may slightly increase production because growing seasons become longer. The availability of additional carbon dioxide to plants for photosynthesis may also increase yields (although as mentioned above, elevated CO2 can have mixed results). However, some research shows that crops become less nutritious when supplied with more carbon dioxide. And if rainfall shifts in space and time, intensified droughts and floods will likely cut into agricultural productivity (Figure 18.19). Considering all factors together, the IPCC predicts global crop yields to increase somewhat, but beyond a rise of 3°C (5.4°F), it expects crop yields to decline. In seasonally dry tropical and subtropical regions, growing seasons may be shortened and harvests may be more susceptible to drought. Thus, scientists predict that crop production will fall in these regions even with minor warming. This would worsen hunger in many of the world’s developing nations.

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Figure 18.19 Drought induced by climate change will likely

Forestry   In the forests that provide our timber and paper products, enriched atmospheric CO2 may spur greater growth in the near term, but other climatic effects such as drought, fire, and disease may eliminate these gains. For example,

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Health hazards from cold weather will decrease, but most researchers feel that the increase in warm-weather hazards will more than offset these gains.

Economics  People will experience a variety of economic costs and benefits from the many impacts of climate change, but on the whole researchers predict that costs will outweigh benefits, especially as climate change grows more severe. Climate change is also expected to widen the gap between rich and poor, both within and among nations. Poorer people have less wealth and technology with which to adapt to climate change, and they rely more on resources

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ALASKA

2000 2002

RUSSIA

2010–2030

CANADA

2040–2060 2070–2090

GREENLAND

ICELAND

FINLAND

NORWAY SWEDEN

Figure 18.20 The Arctic has borne the brunt of climate change’s impacts so far. As Arctic sea ice melts, it recedes from large areas. The map shows the mean minimum summertime extent of sea ice for the recent past, present, and future. Inuit people find it difficult to hunt and travel in their traditional ways, and polar bears starve because they are less able to hunt seals. Structures are damaged as permafrost thaws beneath them: Buildings can lean, buckle, crack, and fall. Map data from National Center for Atmospheric Research and National Snow and Ice Data Center.

Impacts vary by region The impacts of climate change are subject to regional variation, so the way each of us experiences these impacts will depend on where we live. Temperature changes have been greatest in the Arctic (Figure 18.20). Here, ice sheets are melting, sea ice is thinning, storms are increasing, and altered

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conditions are posing challenges for people and wildlife. As sea ice melts earlier, freezes later, and recedes from shore, it becomes harder for Inuit people and for polar bears alike to hunt the seals they each rely on for food. Thin sea ice is dangerous for people to travel and hunt upon, and in recent years, polar bears have been dying of exhaustion and starvation as they try to swim long distances between ice floes. Permafrost is thawing in the Arctic, destabilizing countless buildings. The strong Arctic warming is melting ice caps and ice sheets, contributing to sea level rise.

Weighing the Issues Climate Change and Human Rights In 2005, a group representing North America’s Inuit people sent a legal petition to the Inter-American Commission on Human Rights, demanding that the United States restrict its greenhouse gas emissions, which the Inuit maintained were destroying their way of life in the Arctic. The Commission dismissed the petition. Do you think Arctic-living people deserve some sort of compensation from industrialized nations whose emissions have caused climate change that is disproportionately affecting the Arctic? What ethical or human rights issues, if any, do you think climate change presents? How could these best be resolved?

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(such as local food and water) that are sensitive to climatic conditions. From a variety of economic studies, the IPCC estimated that climate change will cost 1–5% of GDP on average globally, with poor nations losing proportionally more than rich nations. Economists trying to quantify damages from climate change by measuring its external costs (pp. 164, 183) have proposed costs of anywhere from $10 to $350 per ton of carbon. The highest-profile economic study to date has been the Stern Review commissioned by the British government (see The Science behind the Story, Chapter 6, pp. 166–167). This exhaustive review concluded that climate change could cost us roughly 5–20% of GDP by the year 2200, but that investing just 1% of GDP starting now could enable us to avoid these future costs. Regardless of the precise numbers, many economists and policymakers are concluding that spending money now to mitigate climate change will save us a great deal more money in the future.

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For the United States, potential impacts are analyzed and summarized by the U.S. Global Change Research Program, which Congress created in 1990 to coordinate federal climate research. In 2013, this program issued a comprehensive 1200-page report summarizing current research, present trends, and future impacts of climate change on the United States (Table 18.3). This report, the National Climate Assessment, was produced by 240 scientists overseen by a 60-person staff. Released in draft form online for public comment, it will be finalized and presented to Congress, the president, and the American people in 2014. The report makes clear that some impacts are being felt across the nation. Average temperatures across the United States have already increased by 0.8°C (1.5°F) since record keeping began in 1895, with over 80% of this rise occurring just since 1980. Temperatures are predicted to rise by another 2.1–6.2°C (4–11°F) by the end of this century (Figure 18.21). Extreme weather events have become more frequent and costly, and will continue to worsen, imposing escalating costs on farmers, city-dwellers, coastal communities, and taxpayers across the country. Most impacts vary by region, and each region of the United States will face its own challenges (Figure 18.22). For instance, winter and spring precipitation is projected to decrease across the South but increase across the North. Drought may strike in some regions and flooding in others. Sea level rise will likely

Reduced Emissions Scenario Projected Temperature Change (°F) End-of-Century (2071–2099 average)

Continued Emissions Scenario Projected Temperature Change (°F) End-of-Century (2071–2099 average)

Table 18.3 S ome Predicted Impacts of Climate Change in the United States

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•

 verage temperatures will rise 2.1–6.2°C (4–11°F) further by A the year 2100.

•

 roughts, flooding, and wildfire will worsen; dry areas will get D drier and wet areas wetter.

•

 xtreme weather events will become more frequent. The E costs they impose on society will grow.

•

Sea level will rise an additional 0.3–1.2 m (1–4 ft) by 2100.

•

 torm surges will continue to erode beaches and coastal S wetlands, destroy real estate, and damage infrastructure.

•

 ealth problems due to heat stress, disease, and pollution H will rise. Some tropical diseases will spread north.

•

Drought, fire, and pest outbreaks will continue to alter forests.

•

 arine ecosystems and fisheries will be affected by ocean M acidification.

•

Although enhanced CO2 and longer growing seasons favor crops, increased drought, heat stress, pests, and diseases will decrease most yields.

•

 nowpack will decrease in the West; water shortages will S worsen in many areas.

•

Alpine ecosystems and barrier islands will begin to vanish.

•

 ortheast forests will lose sugar maples; Southwest N ecosystems will turn more desertlike.

•

 elting permafrost will undermine Alaskan buildings and M roads.

Adapted from U.S. Global Change Research Program, 2013. National climate assessment. Draft for public review. http://ncadac .globalchange.gov.

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Degrees F 3

4

5

6

7

8

9

10 15

Figure 18.21 Average temperatures across the United States are predicted to rise by the end of this century. Even under a scenario of sharply reduced emissions (top), temperatures are predicted to rise by 3–4°F. Under a scenario of business-asusual emissions (bottom), temperatures are predicted to rise by 7–11°F. Data from U.S. Global Change Research Program, 2013. National climate assessment. Draft for public review.

affect the Atlantic and Gulf Coasts more than the West Coast. Agriculture, forests, wildlife, and human health may experience a wide array of impacts that will vary from one region to another. You may learn more about the scientific predictions for your own region by consulting this publicly accessible report online. All these impacts of climate change are projected consequences of the warming effect of our greenhouse gas emissions (Figure 18.23, see p. 524). We are bound to experience further consequences, but by addressing the root causes of anthropogenic climate change now, we may still be able to prevent the most severe future impacts.

Are we responsible for climate change? Scientists agree that most or all of today’s global warming is due to the well-documented recent increase in greenhouse gas concentrations in our atmosphere. They also agree that this rise in greenhouse gases results primarily

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Great Plains • Drought and heat are accelerating groundwater depletion. • Agriculture will be challenged by heat, drought, and flooding. • Dust storms may return. • Energy and water demands are intensifying.

Midwest • Heat waves are intensifying. • Floods will worsen. • Great Lakes fisheries, beaches, and water quality will suffer. • Crop yields could rise at first, but then would fall due to extreme weather.

Northwest • Wildfire and insect outbreaks are degrading forests. • Sea level rise will impact Seattle and other cities. • Ocean acidification will threaten shellfish industries and marine systems. • Early snowmelt will cause summer water shortages. Southwest • Drought is intensifying water shortages and conflicts. • California agriculture will face multiple challenges. • Wildfire, drought, floods, and invasive species are transforming the landscape. • Urban heat islands will affect health of 90% of population.

Northeast • Sea level rise and storm surges will worsen coastal flooding and damage urban infrastructure. • Heavy precipitation events are causing floods. • Summer heat waves will degrade air quality and health. • Forest composition is changing.

Southeast • Sea level rise is degrading coasts. • Hurricanes and storms are imposing rising costs. • Heat stress poses health risks. • Water supplies are declining amid rising population.

Hawaii and Pacific Islands • Ocean acidification threatens coral reefs and fisheries. • Sea level rise will damage coasts and contaminate aquifers. • Heat, disease, and invasive species are threatening endangered plants and animals. • People may need to evacuate low-lying areas.

Alaska • Melting permafrost is damaging infrastructure. • Loss of sea ice impacts wildlife and Native people. • Offshore petroleum development will increase as sea ice melts. • Fisheries will be altered by ocean changes.

Figure 18.22 Impacts of climate change will vary by region. Shown are a few of the most important impacts scientists expect for each region by the end of the century. Data from U.S. Global Change Research Program, 2013. National climate assessment. Draft for public review.

The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action [to reduce] global greenhouse gas emissions. . . . A lack of full scientific certainty about some aspects of climate change is not a reason for delaying an immediate response that will, at a reasonable cost, prevent dangerous anthropogenic interference with the climate system.

Such a clear consensus statement from the world’s scientists was virtually unprecedented, on any issue—and scientists’ concerns have only grown since that time.

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Yet despite the overwhelming evidence for climate change and its impacts, many people, especially in the United States, have long tried to deny that it is happening. Many of these naysayers now admit that the climate is changing but doubt that we are the cause. Indeed, while most of the world’s nations moved forward to confront climate change through international dialogue, in the United States public discussion of climate change remained mired in outdated debates over whether the phenomenon was real and whether humans were to blame. These debates have been fanned by spokespeople from think tanks and a handful of scientists, many funded by fossil fuel industries. These individuals, together with corporate interests, have aimed to cast doubt on the scientific consensus, and their views are amplified by the American news media, which seeks to present two sides to every issue, even when the sides’ arguments are not equally supported by evidence. For many Americans, former Vice President Al Gore’s 2006 film and book, An Inconvenient Truth, presented an eyeopening summary of the science of climate change and a compelling call to action. Awareness of climate change grew as the 2007 IPCC report was made publicly available on the Internet and was widely covered in the media, and later as Gore and

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from our combustion of fossil fuels for energy and secondarily from the loss of carbon-absorbing vegetation due to deforestation. A decade ago, many scientists had already become concerned enough about the consequences of climate change to put themselves on record urging governments to address the issue. In 2005, the national academies of science from 11 nations (Brazil, Canada, China, France, Germany, India, Italy, Japan, Russia, the United Kingdom, and the United States) issued a joint statement urging political leaders to take action. The statement read, in part:

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Causes

Consequences

Shift of organisms and ecological communities Shift of agricultural zones

Warming atmosphere

Spread of tropical diseases

Fossil fuel use

Human population growth Growth in per capita consumption

Anthropogenic climate change Greenhouse gas emissions

Loss of biodiversity and ecosystem services

• increased air temperatures

Glacier and icecap melting

Change in ocean currents

Regional climate change (e.g., cold Europe)

Sea level rise

• increased ocean temperatures • altered rainfall and ENSO patterns

Stronger hurricanes?

Storm surges and coastal erosion

Coral bleaching

Deforestation Droughts

Economic loss

Flooding

Health impacts

Crop failures

Social disruption

Figure 18.23 Human-induced global climate change stems from several causes (ovals on left) and results in a diversity of consequences (boxes on right) for ecological systems and human well-being. Arrows in this concept map lead from causes to consequences. Items grouped within outlined boxes do not necessarily share any special relationship; the outlined boxes are intended merely to streamline the figure.

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Solutions As you progress through this chapter, try to identify as many solutions to anthropogenic climate change as you can. What could you personally do to help address this issue? Consider how each action or solution might affect items in the concept map above.

the IPCC were jointly awarded the Nobel Peace Prize. At the same time, however, many Americans who disliked Gore’s politics also came to reject his message on climate change. In 2009, a hacker illegally broke into computers at the University of East Anglia, U.K., and made public several thousand documents, including over 1000 private emails among a handful of climate scientists. A few of these messages appeared to show questionable behavior in the use of data and the treatment of other researchers. Climate-change deniers named the incident “Climategate” and used it to accuse the entire scientific establishment of wrongdoing and conspiracy. The news media disseminated the story widely. However, subsequent investigations into the affair by six different independent panels all cleared the climate scientists, concluding that there was no evidence of wrongdoing. Each panel concluded that some individuals may have exercised poor taste or judgment and that some prac-

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tices could be improved, but they also found that many media accounts trumpeting the news had misrepresented the content of the emails. The panels agreed that the hacked messages among a few individuals in no way called into question the vast array of research results compiled by thousands of hard-working independent climate scientists over several decades. Questions were raised the same year about some of the IPCC report’s conclusions, and subsequent inquiry revealed that several statements were inadequately backed by evidence or otherwise misstated or misleading. It is hardly surprising in such a vast collaborative effort that a few statements out of thousands would be in error. Yet scientists wanted to ensure that the IPCC’s reputation for reliability not be tarnished, and so reforms were set in motion to strengthen the IPCC’s process during the preparation of its Fifth Assessment.

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Responding to Climate Change

We are developing solutions in electricity generation From cooking to heating to lighting, much of what we do each day depends on electricity. The generation of electricity produces the largest portion (40%) of U.S. carbon dioxide emissions. Fossil fuel combustion generates 70% of U.S. electricity, and coal accounts for most of the resulting emissions. There are two ways to reduce the amount of fossil fuels

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4.0 3.0 2.0 1.0 0

–1.0 1900

2000 Year

2100

Figure 18.24 The sooner we stabilize our emissions, the less climate change we will cause. The red line shows temperature change we could expect if we were to limit our yearly carbon emissions to the level they were in the year 2000. The blue, green, and yellow lines show the change expected under scenarios of rapid, medium, and slow control of emissions, respectively. The vertical bars show means and ranges of year-2100 temperatures for each scenario. Predictions are based on a large number of climate models. Data from IPCC, 2007. Fourth assessment report.

we burn to generate electricity: (1) encouraging conservation and efficiency (pp. 564–566) and (2) switching to cleaner and renewable energy sources (Chapters 20 and 21).

Conservation and efficiency  As individuals we all can make lifestyle choices to reduce electricity consumption. New energy-efficient technologies make it easier to conserve. Replacing standard light bulbs with compact fluorescent lights reduces energy use for lighting by 40%. The U.S. Environmental Protection Agency’s Energy Star Program rates household appliances, lights, windows, fans, office equipment, and heating and cooling systems by their energy efficiency. Replacing an old washing machine with an Energy Star washing machine can cut your CO2 emissions by 200 kg (440 lb) annually. Energy Star homes use highly efficient windows, ducts, insulation, and heating and cooling systems to reduce energy use and emissions by 30% or more. Such technological solutions also save consumers money by reducing utility bills. Manufacturers can make the same types of choices as consumers in their purchases, and can manufacture energyefficient products. Power producers can use approaches such as cogeneration (p. 564) to produce fewer emissions per unit of energy generated.

Sources of electricity   We can also reduce greenhouse gas emissions by switching to cleaner energy sources. Natural gas generates the same amount of energy as coal, with half the emissions. Cleaner still are alternatives to fossil fuels, including nuclear power (pp. 573–584), bioenergy, hydroelectric power, geothermal power, solar photovoltaic cells, wind power, and ocean sources. These energy sources give off no

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We can respond to climate change in two fundamental ways. One is to pursue actions that reduce greenhouse gas emissions, so as to lessen the severity of climate change. This strategy is called mitigation because the aim is to mitigate, or alleviate, the problem. Examples include improving energy efficiency, switching to clean and renewable energy sources, preventing deforestation, recovering landfill gas, and encouraging farm practices that protect soil quality. The second type of response is to pursue strategies to cushion ourselves from the impacts of climate change. This strategy is called adaptation because the goal is to adapt to change. Erecting a seawall, as Maldives residents did with the Great Wall of Malé, is an example of adaptation. Some people of Tuvalu also adapted, by leaving their island to make a new life in New Zealand (see Weighing the Issues, p. 519). Other examples of adaptation include restricting coastal development; adjusting farming practices to cope with drought; and modifying water management practices to deal with reduced river flows, glacial outburst floods, or salt contamination of groundwater. Both adaptation and mitigation are necessary. Adaptation is needed because even if we could halt all our emissions right now, the greenhouse gas pollution already in the atmosphere would continue driving global warming until the planet’s systems reach a new equilibrium, with temperature rising an estimated 0.6°C (1.0°F) more by the end of the century. Because we will face this change no matter what we do, it is wise to develop ways to minimize its impacts. We also need to pursue mitigation, because if we do nothing to diminish climate change, it will eventually overwhelm any efforts we might make to adapt. To leave a sustainable future for our civilization and to safeguard the living planet that we know, we will need to pursue mitigation. The sooner we begin reducing our emissions, the lower the level at which they will peak, and the less we will alter climate (Figure 18.24). We will spend the remainder of our chapter examining approaches for the mitigation of climate change.

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Today most of the world’s people recognize that our fossil fuel consumption is altering the planet that our children will inherit. From this point onward, our society will be focusing on how best to respond to the challenges of climate change. The good news is that everyone—not just leaders in government and business, but everyday people, and especially today’s youth— can play a part in this all-important search for solutions.

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net emissions during their use (but some in the production of their infrastructure). We will examine these clean and largely renewable energy sources in detail in Chapters 20 and 21. While our society begins to transition to clean and renewable alternatives, we are also trying to capture emissions before they leak to the atmosphere. Carbon capture refers to technologies or approaches that remove carbon dioxide from power plant emissions. Successful carbon capture would allow facilities to continue using fossil fuels while cutting greenhouse gas pollution. The next step is carbon sequestration, or carbon storage, in which the carbon is sequestered, or stored, underground under pressure in deep salt mines, depleted oil and gas deposits, or other underground reservoirs (see Figure 19.16, p. 556). However, we are still a long way from developing adequate technology and secure storage space to accomplish this without leakage. Moreover, it is questionable whether we will ever be able to sequester enough carbon to make a sizeable dent in our emissions. Carbon capture and storage is discussed in more detail in Chapter 19 (pp. 555–556).

Transportation solutions are at hand Can you imagine life without a car? Most Americans probably can’t—a reason why transportation is the second-largest source of U.S. greenhouse gas emissions. The average American family makes 10 trips by car each day, and U.S. taxpayers spend over $200 million per day on road construction and repairs for the nation’s 250 million registered automobiles.

Automotive technology  The typical automobile is highly inefficient. Over 85% of the fuel you pump into your gas tank does something other than move your car down the road (Figure 18.25). The technology exists to reduce these losses and make our vehicles far more fuel-efficient. Indeed, the vehicles of many nations are more fuel-efficient than those of the United States. More aerodynamic designs, increased engine efficiency, and improved tire design all can help. Recent government mandates are encouraging greater fuel efficiency in American-made vehicles (pp. 565–566), and as gasoline prices rise, consumer demand for more fuel-efficient automobiles will intensify. Advancing technology is also bringing us alternatives to the traditional combustion-engine automobile. These include hybrid vehicles that combine electric motors and gasoline-

Gas

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powered engines for greater efficiency (p. 565). They also include fully electric vehicles, alternative fuels such as compressed natural gas and biodiesel (pp. 588–590), and hydrogen fuel cells that use oxygen and hydrogen and produce only water as a waste product (pp. 621–622).

Transportation choices   We can make lifestyle choices that reduce our reliance on cars. Some people are choosing to live nearer to their workplaces. Others use mass transit such as buses, subway trains, and light rail. Still others bike or walk to work or on errands (Figure 18.26). Public transportation in the United States currently serves 3–4% of passenger trips, reducing gasoline use by 4.2 billion gallons each year and saving 37 million metric tons of CO2 emissions, the American Public Transportation Association estimates. If U.S. residents were to increase their use of mass transit to the levels of Canadians (7% of daily travel needs) or Europeans (10% of daily travel needs), the United States could cut its air pollution, its dependence on imported oil, and its contribution to climate change. Unfortunately, reliable and convenient public transit is not yet available in many U.S. communities. Making automobile-based cities and suburbs more friendly to pedestrian and bicycle traffic and improving people’s access to public transportation stand as central challenges for city and regional planners (pp. 363–365).

We will need to follow multiple strategies Advances in agriculture, forestry, and waste management can help us mitigate climate change. In agriculture, sustainable management of cropland and rangeland enables soil to store more carbon. New techniques reduce the emission of methane from rice cultivation and from cattle and their manure, and reduce nitrous oxide emissions from fertilizer. We can also grow renewable biofuel crops, although whether these decrease or increase emissions is an active area of research (pp. 587–591). In forest management, preserving existing forests, reforesting cleared areas, and pursuing sustainable forestry practices (p. 340) all help to absorb carbon from the air. Waste managers are doing their part to cut emissions by treating wastewater (pp. 432–434), generating energy from waste in incinerators (p. 634), and recovering methane seeping from landfills (p. 634). Individuals, communities, and waste haulers also help

14% Moving car

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5% Drive train friction and inefficiencies

2% Running accessories: water pump, stereo, etc.

Figure 18.25 Conventional automobiles are fuel-inefficient. Only about 13–14% of the energy from a tank of gas actually moves the typical car down the road. Nearly 85% of useful energy is lost, primarily as heat. Data from U.S. Department of Energy.

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What role should government play?

Figure 18.26 Commuting by bike or on foot greatly reduces one’s transportation-related greenhouse gas emissions.

reduce emissions when they encourage recycling, composting, and the reuse of materials and products (pp. 634–637). We should not expect to find a single “magic bullet” for mitigating climate change. Reducing emissions will require many steps by many people and institutions across many sectors of our economy. The good news is that most reductions can be achieved using current technology and that we can begin implementing these changes right away. Environmental scientists Stephen Pacala and Robert Socolow advise that we follow some age-old wisdom: When the job is big, break it into small parts. Pacala and Socolow have proposed that we adopt a portfolio of strategies that together can stabilize our CO2 emissions at current levels (Figure 18.27). They identify 15 strategies that could each eliminate 1 billion tons of carbon per year by 2050 if deployed at a large scale. Achieving just 7 of these 15 aims would stabilize our emissions. If we achieve more, then we reduce emissions.

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Figure 18.27 We can accomplish the large job of stabilizing emissions by breaking it into smaller steps. Environmental scientists Stephen Pacala and Robert Socolow began with a standard graph showing the doubling of CO2 emissions that scientists expect to occur from 2005 to 2055. They added a flat line to represent the trend if emissions were held constant and then separated the graph into emissions allowed (below the line) and emissions to be avoided (the triangular area above the line). They then divided this “stabilization triangle” into seven equal-sized portions. Each of these “stabilization wedges” represents 1 billion tons of CO2 emissions in 2055 to be avoided. Finally, they identified a series of strategies, each of which could take care of one wedge. If we accomplish just 7 of these strategies, we could halt our growth in emissions for the next halfcentury. Adapted from Pacala, S., and R. Socolow, 2004. Stabilization wedges: Solving the climate problem for the next 50 years with current technologies. Science 305: 968–972. Reprinted by permission of AAAS and the author.

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Carbon emitted (billions of tons per year)

7 Stabilization wedges

Even if people agree on strategies and technologies to reduce emissions, they may disagree on what role government should play in encouraging those strategies and technologies: Should it mandate change through laws and regulations? Should it impose no policies at all and hope that private enterprise will develop solutions on its own? Should it take the middle ground and design programs that give private entities financial incentives to reduce emissions? This debate has been vigorous in the United States and Canada, where many business leaders and politicians have opposed all government action to address climate change, fearing that emissions reductions will impose economic costs on industry and consumers. In 2007, the U.S. Supreme Court ruled that carbon dioxide was a pollutant that the Environmental Protection Agency (EPA) could regulate under the Clean Air Act (p. 476). When Barack Obama became president, he instead urged that Congress craft legislation to address emissions. In 2009, the Democratic-led House of Representatives passed legislation to create a capand-trade system (p. 201) in which industries and utilities would compete to reduce emissions for financial gain, and under which emissions were mandated to decrease 17% by 2020. However, similar legislation did not pass in the Senate. As a result, responsibility for addressing emissions passed to the EPA, which began developing regulations in 2011. The EPA aimed to phase in emissions limits on industry and utilities gradually over many years, hoping to spur energy efficiency retrofits and renewable energy use at a pace that will minimize economic impacts and political opposition.

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The Kyoto Protocol sought to limit emissions Climate change is a global problem, so global cooperation is needed to forge effective solutions. This is why the world’s policymakers have tried to tackle climate change with international treaties. In 1992 at the U.N. Conference on Environment and Development Earth Summit in Río de Janeiro, Brazil, most of the world’s nations signed the United Nations Framework Convention on Climate Change (FCCC).

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This agreement outlined a plan for reducing greenhouse gas emissions to 1990 levels by the year 2000 through a voluntary, nation-by-nation approach. Emissions kept rising, however, so nations came together to forge a binding treaty to require emissions reductions. An outgrowth of the FCCC drafted in 1997 in Kyoto, Japan, the Kyoto Protocol mandated signatory nations, by the period 2008–2012, to reduce emissions of six greenhouse gases to levels below those of 1990. The treaty took effect in 2005 after Russia became the 127th nation to ratify it. The United States was the only developed nation not to ratify the Kyoto Protocol. U.S. leaders who opposed the treaty called it unfair because it required industrialized nations to reduce emissions but did not require the same of rapidly industrializing nations such as China and India, whose greenhouse emissions were rising quickly. Proponents of the Kyoto Protocol countered that the differential requirements were justified because industrialized nations created the current problem and therefore should take the lead in resolving it. Because the United States was emitting fully one-fifth of the world’s greenhouse gases, its refusal to join international efforts to curb greenhouse emissions generated widespread resentment and undercut the effectiveness of global efforts. At a 2007 conference in Bali, Indonesia, where 190 nations strove to design a road map for future progress, the delegate from Papua New Guinea drew thunderous applause when he requested of the U.S. delegation, “If for some reason you are not willing to lead . . . please get out of the way.” As of 2010 (the most recent year with full international data), nations that signed the Kyoto Protocol had decreased their emissions by 8.9% from 1990 levels (Figure 18.28). However, much of this reduction was due to economic contraction in Russia and nations of the former Soviet Bloc following the breakup of the Soviet Union. When these nations are factored out, the remaining signatories showed a 4.9%

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In June 2013 President Obama gave a speech at Georgetown University announcing that, because of legislative gridlock, he would take steps to address climate change using his executive authority. His “climate action plan” urged the EPA to speed its regulation of new power plants and to begin regulating existing power plants. It also aimed to jumpstart renewable energy development, modernize the electric grid, finance clean coal and carbon storage efforts, improve automotive fuel economy, protect and restore forests, and encourage energy efficiency. At the same time, the president’s plan sought to prepare the nation to adapt to the impacts of climate change, and to better engage with other countries to address greenhouse gas emissions.

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Figure 18.28 The Kyoto Protocol has produced mixed results. Nations ratifying it decreased their emissions of six greenhouse gases by 8.9% by 2010 (a), but this was largely due to unrelated economic contraction in the former Soviet-Bloc countries. A selection of major nations (b) shows varied outcomes in reducing emissions. The United States did not ratify the Protocol, Australia joined it late, and Canada left early. Values do not include influences of land use and forest cover. Data from U.N. Framework Convention on Climate Change, 2013.

increase in emissions. Nations not parties to the accord, including China, India, and the United States, increased their emissions still more.

International climate negotiations seek a way forward In recent years, representatives of the world’s nations have met at a series of international conferences, trying to design a treaty to succeed the Kyoto Protocol. At their 2009 meeting in Copenhagen, Denmark, these climate negotiators failed to reach consensus (Figure 18.29). China promised steep emissions cuts but would not allow international monitoring to

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Figure 18.29 Activists have kept pressure on climate negotiators at each international conference. At Copenhagen, activists showed support for island nations such as Tuvalu and the Maldives and for bringing the atmospheric carbon dioxide level down to 350 parts per million.

Will emissions cuts hurt the economy? Many U.S. policymakers have opposed emissions reductions out of fear that they will dampen the national economy. China, India, and other large industrializing nations have so far resisted emissions cuts under the same assumption. This is understandable, given that our current economies depend so heavily on fossil fuels. Yet other nations have demonstrated that economic vitality does not require ever-growing emissions. For example, Germany has the third most technologically advanced economy in the world and is a leading producer of iron, steel, coal, chemicals, automobiles, machine tools, electronics, textiles, and other goods—yet it managed between 1990 and 2010 to reduce its greenhouse gas emissions by 25%. In the same period, the United Kingdom cut its emissions by 23%, and the European Union as a whole cut its emissions by 15% (see Figure 18.28). Today the citizens of many nations enjoy standards of living comparable to that of U.S. citizens, yet with far fewer emissions. In fact, on a per-person basis, wealthy nations from France to Denmark to New Zealand to Hong Kong to Switzerland to Sweden emit greenhouse gases at less than half of the U.S. rate. Because resource use and per capita emissions are high in the United States, policymakers and industries often assume the United States has more to lose economically from restrictions on emissions than developing nations do. However, industrialized nations are also the ones most likely to gain economically from major energy transitions, because they are best positioned to invent, develop, and market new technologies to power the world in a post-fossil-fuel era. Germany, Japan, and China have realized this and are now leading the world in production, deployment, and sales of solar energy technology (Figure 18.30). China recently surpassed the United States to become the world’s biggest greenhouse gas emitter (although it still emits far less per person than the United States). Yet China has also embarked on a number of initiatives to develop and sell renewable energy technologies on a scale beyond what any other nation has attempted. If the

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confirm them. U.S. President Obama favored emissions cuts but would not promise the international community more than the U.S. Congress would agree to. (The Senate had rejected climate legislation, and Senate approval is needed for U.S. ratification of any treaty.) On the final day of the conference, leaders of major nations put together an agreement, the Copenhagen Accord. However, it failed to win a unanimous vote, and the conference ended without specific targets or solid commitments. In a dramatic final session, several nations denounced the accord, so that the conference could not even formally adopt it by consensus and had to merely “take note” of it. Tuvalu and the Maldives took opposite sides in the debate. Tuvalu insisted on protesting the accord on principle, whereas the Maldives concluded that a weak accord was better than no accord. The process got back on track in Cancun, Mexico, in 2010, where nations fleshed out plans based on the Copenhagen Accord. Developed nations promised to pay developing nations to help with their mitigation and adaptation efforts—up to $100 billion per year by 2020—through a fund overseen by the World Bank. Nations broadly agreed upon a plan, nicknamed REDD (p. 332), to help tropical nations reduce forest loss. Developed nations agreed to transfer clean energy technology to developing nations. And rapidly industrializing nations such as China and India agreed in principle to emission targets and international monitoring. Moreover, nations shared how they seek to reduce greenhouse gas pollution; China would accelerate its renewable energy efforts, for example, and Brazil would limit deforestation and encourage no-till agriculture (pp. 244–246). In Durban, South Africa, in 2011, negotiators failed to design a new treaty but did succeed in getting all nations— including the top emitters China, the United States, and India— to agree to a “road map” toward a legally binding international deal in 2015, which would come into force only after 2020. This plan was reaffirmed at the 2012 conference in Doha, Qatar, where negotiators also extended the Kyoto Protocol until 2020. A number of nations backed out of the Kyoto extension, however, and this treaty now applies to only about 15% of the world’s emissions. Neither the $100 billion “Green Climate Fund” nor the REDD program made progress in Durban or Doha, because nations could not agree on how to finance them. Although the Durban and Doha conferences produced a plan that might bear fruit years down the road, most scientists reacted with disappointment and alarm, because waiting until 2020 for a meaningful agreement creates a “lost decade” during which climate change could grow far worse. The United Nations estimates there is now a gap of more than 6 billion metric tons of emissions between what the world has pledged to cut and the degree of cuts that science tells us is needed to limit climate change to 2°C of warming. Reaching consensus among 200 nations through the treaty process is a daunting challenge. As a result, experts now predict that most success in mitigating climate change will come from technological advances, economic incentives, and national, regional, and local initiatives. Business and industry are beginning to accelerate renewable energy and energyefficiency efforts, and policymakers are looking to create environments in which private-sector efforts can generate productive solutions.

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power plants. A similar effort, the Western Climate Initiative, involves British Columbia, California, Manitoba, Ontario, and Quebec. These emissions trading programs (pp. 201–202) show how government can engage the market economy to pursue public policy goals.

Market mechanisms are being used to address climate change

Figure 18.30 China is racing to develop renewable energy technology. It is on track to surpass the United States as a leader in green energy. Here, workers at a Chinese factory produce photovoltaic solar panels.

United States does not act quickly to develop energy technologies for the future, then the future could belong to nations like China, Germany, and Japan.

States and cities are advancing climate change policy

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In the absence of legislative action by the U.S. federal government to address climate change, state and local governments across the country are advancing policies to limit emissions. Mayors from over 1000 cities from all 50 U.S. states have signed on to the U.S. Mayors Climate Protection Agreement, initiated by former Seattle mayor Greg Nickels. Under this agreement, mayors commit their cities to pursue policies to “meet or beat” Kyoto Protocol guidelines. A number of U.S. states have enacted targets or mandates for renewable energy production, seeking to boost cleaner alternatives to fossil fuels. Many more states and cities have adopted plans for adapting to climate change’s impacts. New York City Mayor Michael Bloomberg launched the New York City Panel on Climate Change in 2008 as part of the PlaNYC sustainability plan (p. 372). Its deliberations and its 2010 report gave New York a head start in tackling the challenges posed by Superstorm Sandy and those that await it in the new era of sea level rise. At the state level, the boldest action so far has come in California. In 2006 that state’s legislature worked with Governor Arnold Schwarzenegger to pass the Global Warming Solutions Act, which aims to cut California’s greenhouse gas emissions 25% by the year 2020. This law was the first state legislation with penalties for noncompliance and followed earlier efforts in California to mandate higher fuel efficiency for automobiles. Among other approaches it has established a permit trading program for carbon emissions. Action is also being taken by nine northeastern states collaborating in the Regional Greenhouse Gas Initiative. In this effort, Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New York, Rhode Island, and Vermont run a joint cap-and-trade program for carbon emissions from

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Permit trading programs aim to harness the economic efficiency of market capitalism to achieve public policy goals while allowing business, industry, or utilities flexibility in how they meet those goals (p. 201). Supporters of permit trading programs argue that they provide the fairest, least expensive, and most-effective method of reducing emissions. Polluters choose how to cut their emissions and are given financial incentives for reducing emissions below the legally required amount (Figure 18.31). As an example of how a cap-and-trade emissions trading program for carbon emissions works, consider the approach of the Regional Greenhouse Gas Initiative: 1. Each state decided what polluting sources it would re 2. 3. 4. 5.

6.

quire to participate. Each state set a cap on the total CO2 emissions it would allow, equal to its 2009 levels. Each state distributed to each emissions source one permit for each ton it emits, up to the amount of the cap. Each state will lower its cap progressively—10% by 2018. Sources with too few permits to cover their pollution must reduce their emissions, buy permits from other sources, or pay for credits through a carbon offset project (p. 531). Sources with excess permits may sell them. Any source emitting more than its permitted amount faces penalties.

Once up and running, it is hoped that the system will be self-sustaining. The price of a permit is meant to fluctuate freely in the market, creating the same kinds of financial incentives as any other commodity that is bought and sold in our capitalist system. The world’s largest cap-and-trade program is the European Union Emission Trading Scheme. This market got off to a successful start in 2005—until investors discovered that national governments had allocated too many permits to their industries. The overallocation gave companies little incentive to reduce emissions, so permits lost their value and prices in the market took a nosedive. Europeans partly addressed these problems by making emitters pay for permits and setting emissions caps across the entire European Union while expanding the program to include more greenhouse gases, more emissions sources, and additional members. Similar difficulties have befallen the Regional Greenhouse Gas Initiative, as well as the world’s first emissions trading program for greenhouse gas reduction, the Chicago Climate Exchange, which operated from 2003 to 2010 and involved several hundred corporations, institutions, and municipalities. All these early experiments in carbon markets are providing

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Figure 18.31 A cap-and-trade emissions trading system harnesses the power of market capitalism to achieve the goal of reducing emissions. In such a system, 1 government first sets an overall cap on emissions. As polluting facilities respond, some will have better success reducing emissions than others. In this figure, 2 Plant A succeeds in cutting its emissions well below the cap, whereas 3 Plant B fails to cut its emissions at all. As a result, 4 Plant B pays money to Plant A to purchase allowances that Plant A is no longer using. Plant A profits from this sale, and the government cap is met, reducing pollution overall. Over time, the cap can be progressively lowered to achieve further emissions cuts.

lessons for how to set up effective and sustainable programs in the future. One lesson is that in the long run, permits will be valuable and the market will work only if government policies are in place to limit emissions.

Carbon taxes are another option

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Cap-and-Trade or a Carbon Tax?  What advantages and disadvantages do you see in using a cap-and-trade system to reduce greenhouse gas emissions? What pros and cons do you see in using carbon taxes to achieve this goal? What do you think of the idea of a “fee-and-dividend” program? If you were a U.S. senator, what type of policy would you support in order to address emissions in the United States, and why?

Carbon offsets are popular Emissions trading programs generally allow participants to buy carbon offsets, voluntary payments intended to enable another entity to help reduce the emissions that one is unable to reduce. The payment thus offsets one’s own emissions. For example, a coal-burning power plant could pay a reforestation project to plant trees that will soak up as much carbon dioxide as the coal plant emits. Or a university could fund the development of clean and renewable energy projects to make up for fossil fuel energy the university uses. Carbon offsets have fast become popular among utilities, businesses, universities, governments, and individuals trying to achieve carbon-neutrality, a condition in which no net carbon is emitted. In principle, carbon offsets seem a great idea, but rigorous oversight is needed to make sure that the offset money actually accomplishes what it is intended for. Offsets are effective only if they fund emissions reductions that would not occur otherwise. And because trees can soak up only so much carbon dioxide, at some point our ability to reduce emissions by funding reforestation could reach its limit. Efforts to create a transparent and enforceable system for verifying the effectiveness of offsets are ongoing. If these efforts succeed, then

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As the world’s carbon trading markets show mixed results early in their growth, some economists, scientists, and policymakers are saying that cap-and-trade systems are not effective enough, don’t work quickly enough, or leave too much to chance. Many of these critics would prefer that governments enact a carbon tax instead. In this approach, governments charge polluters a fee for each unit of greenhouse gases they emit. This gives polluters a financial incentive to reduce emissions. Such a tax can be implemented in various ways; it can be charged to energy producers, utilities, or motor vehicle users, and it can be scaled according to energy efficiency. Carbon taxes of various types have so far been introduced in roughly 20 nations. In the United States, Boulder, Colorado, implemented a tax on electricity consumption, and Montgomery County, Maryland, is taxing polluting power plants. The downside of a carbon tax is that most polluters simply pass the cost along to consumers by charging higher prices for the products or services they sell. Proponents of carbon taxes have responded by proposing an approach called feeand-dividend. In this approach, funds from the carbon tax, or “fee,” paid to government by polluters are transferred as a tax refund, or “dividend,” to taxpayers. This way, if polluters pass their costs along to consumers, those consumers will be reimbursed for those costs by the tax refund they receive. In theory, the system should provide polluters a financial incentive to reduce emissions while imposing no financial burden on taxpayers.

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carbon offsets could become an important means of mitigating climate change.

Place space mirrors in orbit

Corporations are going carbon-neutral Carbon offsets are a major route toward carbon-neutrality among businesses and corporations seeking to make their practices more sustainable (pp. 173–174), but corporations also can find ways to reduce their carbon footprints directly. An excellent example is Pearson Education, the publisher of your textbook! In 2009 Pearson achieved carbon-neutrality after a concerted two-year effort (p. 173). Pearson reduced its energy consumption and carbon footprint directly by 12% by upgrading buildings for energy efficiency, designing more efficient computer servers, reducing the number of vehicles in its fleets, increasing the proportion of hybrid vehicles, and cutting back on employee business travel while enhancing the use of video conferencing. Pearson eliminated a further 47% of its emissions by purchasing clean renewable energy instead of fossil fuel energy and by installing large solar panel arrays at two of its sites in New Jersey and a wind turbine at a Minnesota site. To offset the remaining 41% of its emissions, the company is funding a number of programs to preserve forest and replant trees in various areas of the world, from England to Costa Rica.

Should we engineer the climate?

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What if all our efforts to reduce emissions are not adequate to rein in climate change? As severe climate change begins looking more and more likely, some scientists and engineers are reluctantly considering drastic, assertive steps to alter Earth’s climate in a last-ditch attempt to reverse global warming—an approach called geoengineering (Figure 18.32). One geoengineering approach would be to suck carbon dioxide out of the air. For example, we might enhance photosynthesis in natural systems by planting trees or by fertilizing ocean phytoplankton with nutrients like iron. A more hightech method would be to design “artificial trees,” structures that chemically filter CO2 from the air. A second geoengineering approach would be to block sunlight before it reaches Earth, thus cooling the planet. We might deflect sunlight by injecting sulfates or other fine dust particles into the stratosphere, by seeding clouds with seawater, or by deploying fleets of reflecting mirrors on land, at sea, or in orbit in space. Scientists have long been reluctant even to discuss the notion of geoengineering. The potential methods are technically daunting and would take years or decades to develop, and some could pose unforeseen environmental risks. Moreover, blocking sunlight does not reduce greenhouse gas concentrations, so ocean acidification would continue. In addition, many experts are wary of promulgating hope for easy technological fixes, lest politicians lose incentive to develop policy to reduce emissions. However, as climate change intensifies, more scientists are becoming willing to contemplate geoengineering as a

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Inject sulfate aerosols into stratosphere Capture carbon with artificial trees

Restore forests

Seed clouds with seawater mist

Erect land-based mirrors Store carbon underground

Fertilize ocean with iron to spur plankton blooms

Figure 18.32 Geoengineering proposals seek to cool the climate by removing carbon dioxide from the air or reflecting sunlight away from Earth. However, most geoengineering ideas are untested, would take years to develop, may not work well, or might cause undesirable side effects. Thus, they are not a substitute for reducing emissions.

back-up plan. Respected researchers and scientific institutions are beginning to assess the risks and benefits of geoengineering options, so that we can be ready to take well-informed action if climate change becomes severe enough to justify it.

You can address climate change National policies, international treaties, emissions trading programs, corporate actions, and technological innovations—and perhaps even geoengineering—will all play roles in mitigating climate change. But in the end, the most influential factor may be the collective decisions of millions of regular people. Just as we each have an ecological footprint (pp. 22–23), we each have a carbon footprint that expresses the amount of carbon we are responsible for emitting. To help reduce emissions, each of us can take steps in our everyday lives—from turning off lights and choosing energy-efficient appliances, to eating a less meatoriented diet, to deciding where to live and how to get to work. College students are vital to driving the personal and societal changes needed to reduce carbon footprints and address climate change—both through everyday lifestyle choices and through lobbying and activism. Today a groundswell of interest is sweeping across campuses, and many students are pressing their administrations to seek carbon-neutrality or to divest from fossil fuel investments and promote renewable energy (pp. 34–36, 673–683). Campus action on climate

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change first made news on January 31, 2008, when over 1900 schools participated in the Focus the Nation teach-in on global warming. Young people have played a large part in subsequent grassroots events and organizations, including 350.org’s International Day of Climate Action on October 24, 2009. This event—kicked off by the Maldives’ underwater cabinet meeting—featured 5200 events in 181 nations and was called “the most widespread day of political action in the planet’s history.” Global climate change may be the biggest challenge we face, but halting it would be our biggest victory. With concerted action, there is still time to avert the most severe impacts and sustain a livable climate. Through outreach, education, innovation, and lifestyle choices, today’s youth have the power to turn the tables on climate change and help bring about a bright future for humanity and our planet.

Conclusion Many factors influence Earth’s climate, and human activities have come to play a major role. Climate change is well underway, and further greenhouse gas emissions will intensify global warming and cause increasingly severe and diverse impacts. Sea level rise and other consequences of global climate change will affect locations worldwide from the Maldives to Bangladesh to Alaska to New York to Florida. As scientists and policymakers come to better understand anthropogenic climate change and its environmental, economic, and social consequences, more and more of them are urging immediate action. Reducing greenhouse gas emissions and taking other steps to mitigate and adapt to climate change represent the foremost challenges for our society in the coming years.

Reviewing Objectives You should now be able to: Describe Earth’s climate system and explain the factors influencing global climate

• Earth’s climate changes naturally over time, but it is now changing rapidly because of human influence. (p. 502) • The sun provides most of Earth’s energy. Earth absorbs 70% of incoming solar radiation and reflects 30% back into space. (pp. 502–503) • Greenhouse gases such as carbon dioxide, methane, water vapor, nitrous oxide, ozone, and halocarbons warm the atmosphere by absorbing and re-emitting infrared radiation. (pp. 502–503) • Earth is experiencing radiative forcing of 1.6 watts/m2 of thermal energy above what it was experiencing 250 years ago. (p. 505)

Characterize human influences on the atmosphere and on climate

• Climate models serve to predict future changes in climate. (pp. 508–509, 512–513)

Outline current and future trends and impacts of global climate change

• Climate science is a huge body of research. The Intergovernmental Panel on Climate Change (IPCC) synthesizes current research, and its periodic reports represent the consensus of the scientific community. (pp. 510–511) • Temperatures on Earth have warmed by an average of 0.74°C (1.33°F) over the past century and are predicted to rise 1.8– 4.0°C (3.2–7.2°F) over the next century. (pp. 510–511, 514) • Changes in precipitation have varied by region. (pp. 514–515) • Extreme weather events are becoming more frequent, likely in part as a result of modification of the jet stream. (pp. 514–515) • Melting glaciers will diminish water supplies, and melting ice sheets are adding to sea level rise. (p. 516)

• By burning fossil fuels and clearing forests, people are increasing atmospheric concentrations of greenhouse gases. (p. 504)

• Sea level has risen an average of 21 cm (8.3 in.) over the past 130 years, and will rise by more in the coming century. (pp. 516–518)

• Increased greenhouse gas emissions enhance the greenhouse effect. (p. 504)

• Storm surges worsened by higher sea levels threaten the mainland United States, and not just oceanic islands. (pp. 516–519)

• Input of aerosols into the atmosphere exerts a variable but slight cooling effect. (p. 505)

• Ocean acidification may be one of the most far-reaching impacts of our greenhouse gas emissions. (p. 519)

Summarize how researchers study climate

• Proxy indicators—such as data from ice cores, sediment cores, tree rings, packrat middens, and coral reefs—reveal information about past climate. (pp. 506–509)

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• Climate change exerts impacts on organisms and ecosystems, as well as on agriculture, forestry, health, and economics. (pp. 519–521) • Climate change and its impacts vary regionally. (pp. 521–523)

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• Milankovitch cycles, solar radiation, ocean absorption, and ocean circulation all influence climate. (pp. 505–506)

• Direct measurements of temperature, precipitation, and other conditions tell us about current climate. (pp. 507–508, 510)

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• Despite some remaining uncertainties, the scientific community feels that evidence for humans’ role in influencing climate is strong enough to justify taking action to reduce emissions. (pp. 522–523) Suggest ways we may respond to climate change

fallen far short of what is needed to limit climate change. (pp. 528–529) • Developing renewable energy technologies presents economic opportunities. (pp. 529–530)

• Both adaptation and mitigation are necessary. (p. 525)

• Some U.S. states and cities are acting to address emissions. (p. 530)

• Conservation, energy efficiency, and new clean and renewable energy sources will help reduce greenhouse gas emissions. (pp. 525–526)

• Emissions trading programs provide a way to harness the free market and engage industry in reducing emissions. (pp. 530–531)

• New automotive technologies and investment in public transportation will help reduce emissions. (pp. 526–527)

• A carbon tax, specifically a fee-and-dividend approach, is another option. (p. 531)

• Addressing climate change will require multiple strategies. (p. 527)

• Individuals and corporations are increasingly exploring carbon offsets and other means of reducing personal carbon footprints. (pp. 531–533)

• The Kyoto Protocol provided a first step for nations to begin addressing climate change. (p. 528) • International efforts to design a treaty to follow the Kyoto Protocol have made some progress, but have

• Some scientists are so anxious about our lack of response to climate change that they are now studying potential geoengineering options. (p. 532)

Testing Your Comprehension 1. What happens to solar radiation after it reaches Earth?

6. Describe how rising sea levels, caused by global warm-

How do greenhouse gases warm the lower atmosphere? Why is carbon dioxide considered the main greenhouse gas? Why are carbon dioxide concentrations increasing in the atmosphere? How can scientists learn about climatic history? Has simulating climate change with computer programs been effective in helping us predict climate? Briefly describe how these programs work. List three major trends in climate that scientists have documented so far. Now list three future trends that they are predicting, along with their potential impacts.

ing, can create problems for people. How is climate change affecting marine ecosystems? 7. How might a warmer climate affect agriculture? How is it affecting distributions of plants and animals? How might it affect human health? 8. Briefly explain why water vapor may either contribute to or slow global warming. 9. What roles have international treaties played in addressing climate change? Give two specific examples. 10. How is a cap-and-trade emissions program different from enacting a carbon tax? Describe the pros and cons of the two approaches.

2.

3. 4.

5.

Seeking Solutions

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1. Some people argue that we need “more proof” or “better

2. Describe several ways in which we can reduce greenhouse

science” before we commit to substantial changes in our energy economy. How much certainty do you think we need before we should take action regarding climate change? How much certainty do you need in your own life before you make a major decision? Should nations and elected officials follow a different standard? Do you believe that the precautionary principle (pp. 283, 401) is an appropriate standard in the case of global climate change? Why or why not?

gas emissions from transportation. Which approach do you think is most realistic, which approach do you think is least realistic, and why? 3. Suppose that you would like to make your own lifestyle carbon-neutral and that you aim to begin by reducing the emissions you are responsible for by 25%. What three actions would you take first to achieve this reduction?

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4. Think about the many ways in which your campus might

6. THINK IT THROUGH You have just been elected gover-

reduce its greenhouse gas emissions. Come up with three concrete proposals for ways to reduce emissions on your campus that you feel would be effective and feasible. How would you present these proposals to your campus administration to get its support? 5. THINK IT THROUGH You have been appointed as the United States representative to an international conference to negotiate terms of the emissions reduction treaty to replace the Kyoto Protocol in 2020. The U.S. government has instructed you to take a leading role in designing the new treaty and to engage constructively with other nations’ representatives while protecting your nation’s economic and political interests. What type of agreement will you try to shape? Describe at least three components that you would propose or agree to, and at least one that you would oppose.

nor of a medium-sized U.S. state. Polls show that the public wants you to take bold action to reduce greenhouse gas emissions. However, polls also show that the public does not want prices of gasoline or electricity to rise. Carbon-emitting industries in your state are wary of emissions reductions being required of them but are willing to explore ideas with you. Your state legislature will support you in your efforts as long as you remain popular with voters. The state to your west has just passed ambitious legislation mandating steep greenhouse gas emissions reductions. The state to your east has just joined a new regional emissions trading consortium. What actions will you take in your first year as governor?

Calculating Ecological Footprints Global climate change is something to which we all contribute, because fossil fuel combustion plays such a large role in supporting the lifestyles we lead. Conversely, as individuals, each one of us can help to mitigate climate change through personal decisions and actions in how we live our lives.

 

Carbon footprint (tons per person per year)

World average U.S. average Your footprint Your footprint with three changes (see Question 3)

       

STUDENTS Go to MasteringEnvironmentalScience for assignments, the etext, and the Study Area with practice tests, videos, current events, and activities.

2. As you took the quiz and noted the impacts of various choices and activities, which one surprised you the most? 3. Think of three changes you could make in your lifestyle that would lower your carbon footprint. Now take the footprint quiz again, incorporating these three changes. Enter your resulting footprint in the table. By how much did you reduce your yearly emissions? 4. What do you think would be an admirable yet realistic goal for you to set as a target value for your own footprint? Would you choose to purchase carbon offsets to help reduce your impact? Why or why not?

INSTRUCTORS Go to MasteringEnvironmentalScience for automatically graded activities, current events, videos, and reading questions that you can assign to your students, plus Instructor Resources.

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1. How does your personal carbon footprint compare to that of the average U.S. resident? How does it compare to that of the average person in the world? Why do you think your footprint differs from these in the ways it does?

Several online calculators enable you to calculate your own personal carbon footprint, the amount of carbon emissions for which you are responsible. Go to http://www.nature.org/ greenliving/carboncalculator/, take the quiz, and enter the relevant data in the table.

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19

Extraction of oil sands at a mine in Alberta

Fossil Fuels, Their Impacts, and Energy Conservation Upon completing this chapter, you will be able to: Identify the energy sources we use Describe the origin and nature of major types of fossil fuels Explain how we extract and use fossil fuels Evaluate peak oil and the challenges it may pose Examine how we are reaching further for fossil fuels

Outline and assess environmental impacts of fossil fuel use, and explore solutions Evaluate political, social, and economic aspects of fossil fuel use Specify strategies for conserving energy and enhancing efficiency

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CEN T RA L C AS E S T U DY

Alberta’s Oil Sands and the Keystone XL Pipeline Fort McMurray

Oil sands

Alberta

Manitoba

Hardisty

“It’s good for our country, and it’s good for our economy, and it’s good for the American people, especially those who are looking for work.”

Saskatchewan

Montana Sandhills Existing Keystone pipeline Proposed Keystone XL extension

—House Speaker John Boehner (R-Ohio)

South Dakota

“It will be game over for the climate.”

Nebraska Steele City Kansas

Illinois

—Climate scientist James Hansen

Patoka Missouri

Cushing Oklahoma Texas Houston

Port Arthur

Everything about Canada’s oil sands is huge. These fossil fuel deposits cover a region the size of Illinois, within boreal forests that span the width of the continent. The open pit mines dug to extract the fuel are miles wide; the vehicles moving inside them like ants are million-pound haul trucks with 14-foot tires and shovels that are five stories high. The economic value of the extracted oil is astounding. Last but not least, burning all this fuel will alter the very climate of our planet. Oil sands, also called tar sands, are layers of sand or clay saturated with a viscous, tarry type of petroleum called bitumen. Huge areas of these wet blackish deposits underlie a thinly populated region of northern Alberta, and the implications of mining them for oil are momentous. To some people the oil sands represent wealth and security, a key to maintaining our fossil-fuel-based lifestyle far into the future. To others they are a source of appalling pollution and threaten to radically alter Earth’s climate. To extract oil from oil sands, companies clear the boreal forest and then strip-mine the land, peeling back layers of peat and creating open pits 215 m (400 ft) deep. The gooey deposits are mixed with hot water and chemicals to separate the bitumen from the sand, and the bitumen is removed and processed, while wastewater is dumped into toxic tailings lakes that are even larger than the mines. In locations where oil sands are more deeply buried, hot water is injected down deep shafts to liquefy, separate, and extract the bitumen in situ.

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Mining for oil sands began in Alberta in 1967, but for many years it was hard to make money extracting these low-quality deposits. Rising oil prices in recent years have now turned it into a profitable venture, and today dozens of companies are mining here. Canadian oil sands are producing 1.7 million barrels of oil per day, more than half of Canada’s petroleum production. Thanks to the oil sands, Canada boasts the world’s third-largest proven reserves of oil, after Saudi Arabia and Venezuela. Each truckload of oil sands that leaves a mine carries oil worth close to $20,000 at 2013 prices. Canada looked for buyers south of its border first, seeking to capitalize on the United States’ insatiable appetite for oil. TransCanada Corporation built the Keystone Pipeline to ship diluted bitumen into the United States. This pipeline system began operating in 2010, bringing oil from Alberta nearly 3500 km (2200 mi) to Illinois and Oklahoma. At the Oklahoma terminus in the town of Cushing, a bottleneck created a glut of oil that was unable to reach refineries on the Texas coast fast enough to meet demand. TransCanada proposed the Keystone XL extension, a two-part project consisting of (1) a southern leg to connect Cushing to the Texas refineries and (2) a northern leg that would cut across the Great Plains to shave off distance and add capacity to the existing line. The Keystone XL pipeline proposal soon met opposition from people living along the proposed route who were concerned about health, environmental protection, and property

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Ogallala Aquifer

North Dakota

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rights. It also faced nationwide opposition from advocates of action to address global climate change. Pipeline proponents feel the Keystone XL project will create jobs for workers in the U.S. heartland and will guarantee a dependable oil supply for decades to come. They stress that buying oil from Canada—a stable, friendly, democratic neighbor—could help end U.S. reliance on oil-producing nations such as Saudi Arabia and Venezuela that have had authoritarian governments and poor human rights records. Opponents of the pipeline extension express dismay at the destruction of boreal forest and anxiety about transporting oil over the continent’s largest aquifer, where spills could contaminate drinking water for millions of people and irrigation water for America’s breadbasket. They also seek to avoid extracting a vast new source of fossil fuels whose combustion would release immense amounts of greenhouse gases that will intensify climate change. By buying a source of oil that is energy-intensive to extract and that burns less cleanly than conventional fuels, they maintain, the United States would be prolonging fossil fuel dependence and worsening climate change when it should instead be transitioning to clean renewable energy. Under pressure from all sides, the administration of U.S. President Barack Obama walked a fine line. Because the northern leg of the Keystone XL extension crosses an international border, it requires a presidential permit from the U.S. Department of State—which TransCanada applied for in 2008. After three years of review, the State Department hesitated to approve the project because of concerns about damage to the ecologically sensitive Sandhills area of Nebraska and potential contamination of the Ogallala Aquifer. Facing street protests at the White House (FIGURE 19.1), Obama in November 2011 postponed the permit decision. Republicans in Congress reacted by demanding a decision in 60 days and attaching this mandate to legislation for a payroll tax cut. Obama responded by announcing that the application would be denied because of insufficient time to review the pipeline’s impact. However, Obama encouraged TransCanada to renew its application with a revised route avoiding the areas of concern in Nebraska and to proceed with the southern leg of the pipeline, which requires no permit. TransCanada did both. Meanwhile, Canadian officials grew irritated and began considering building a pipeline west to British Columbia and selling the oil to China instead. In March 2013 the State Department released a draft environmental impact statement for the new route. The draft EIS gave little indication that it would stand in the way of pipeline development. The State Department planned to issue a final

Sources of Energy

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Humanity has devised many ways to harness the renewable and nonrenewable forms of energy available on our planet (TABLE 19.1). We use these energy sources to heat and light our homes; power our machinery; fuel our vehicles; produce plastics, pharmaceuticals, and synthetic fibers; and provide the

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FIGURE 19.1 Many Americans have opposed the Keystone XL pipeline extension. Tens of thousands of activists protested in front of the U.S. White House in increasingly large rallies in 2011, 2012, and 2013.

EIS after receiving public comment, after which Obama would decide whether to approve the pipeline. Throughout 2013 the debate intensified. In February, tens of thousands of Americans protested against the pipeline in front of the White House. These protestors viewed the decision on Keystone XL as a test of Obama’s vow to deal with climate change, made in his inauguration speech a month earlier. Pipeline proponents countered that Canada would find a way to extract and sell its oil in any case, so the United States might as well take advantage of the trade benefits of buying it and reselling it on the world market. Later that year, Obama announced that he would approve the pipeline only if it “does not significantly exacerbate the problem of carbon pollution.” What this signaled was unclear, however: The draft EIS suggested the pipeline would not do so, but the Environmental Protection Agency had judged the EIS to be inadequate. As this book went to press, a decision to approve or deny the Keystone XL pipeline had not yet been made. We will leave it to you and your instructor to flesh out the rest of this story! The divergent views on Canada’s oil sands reflect our confounding relationship with fossil fuels. These energy sources power our civilization and have enabled our modern standard of living—yet as climate change worsens, we face the need to wean ourselves from them and shift to clean renewable energy sources. The way in which we handle this complex transition will determine a great deal about the quality of our lives and the future of our society and our planet.

comforts and conveniences to which we’ve grown accustomed in the industrial age.

Nature offers us a variety of energy sources Most of Earth’s energy comes from the sun. We can harness energy from the sun’s radiation directly by using solar

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TABLE 19.1  Energy Sources We Use ENERGY SOURCE

DESCRIPTION

TYPE OF ENERGY

Crude oil

Fossil fuel extracted from ground (liquid)

Nonrenewable

Natural gas

Fossil fuel extracted from ground (gas)

Nonrenewable

Coal

Fossil fuel extracted from ground (solid)

Nonrenewable

Nuclear energy

Energy from atomic nuclei of uranium

Nonrenewable

Biomass energy

Energy stored in plant matter from photosynthesis

Renewable

Hydropower

Energy from running water

Renewable

Solar energy

Energy from sunlight directly

Renewable

Wind energy

Energy from wind

Renewable

Geothermal energy

Earth’s internal heat rising from core

Renewable

Tidal and wave energy

Energy from tides and ocean waves

Renewable

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World fossil fuel consumption (billion tons of oil equivalent)

4 Oil 3 Coal 2 Natural gas 1

0 1950

1960

1970

1980 Year

1990

2000

2010

FIGURE 19.2 Annual global consumption of fossil fuels has risen greatly over the past half-century. Oil remains our leading energy source. Data from U.S. Energy Information Administration; International Energy Agency; and BP p.l.c., 2012, Statistical review of world energy 2012.

By roughly what percentage has the annual consumption of oil risen since the year you were born?

of years. At our accelerating rate of consumption, we will use up Earth’s easily accessible store of conventional fossil fuels in just decades. For this reason, and because fossil fuels exert severe environmental impacts, renewable energy sources increasingly are being developed as alternatives to fossil fuels (Chapters 20 and 21).

Fossil fuels dominate our energy use Since the industrial revolution, fossil fuels have replaced biomass as our society’s dominant source of energy. Global consumption of coal, oil, and natural gas has risen for years and is now at its highest level ever (FIGURE 19.2). The high energy content of fossil fuels makes them efficient to burn, ship, and store. We use these fuels for transportation, manufacturing, heating, and cooking and also to generate electricity, a secondary form of energy that is convenient to transfer over long distances and apply to a variety of uses. Each type of fuel has its own mix of uses, and each contributes in different ways to our economies and our daily needs. For instance, oil is used mostly for transportation, whereas coal is used mostly to generate electricity. Societies differ in how they use energy. Industrialized nations apportion roughly one-third of their energy to transportation, one-third to industry, and one-third to all other uses. In contrast, industrializing nations devote a greater proportion of energy to subsistence activities such as agriculture, food preparation, and home heating, and much less to transportation. Moreover, people in developing countries often rely on manual or animal energy sources instead of automated ones. For instance, most rice farmers in Southeast Asia plant rice by hand, but industrial rice growers in California use airplanes. Because industrialized nations rely more on equipment and technology, they use more fossil fuels. In the United States, oil, coal, and natural gas together supply 82% of energy demand (FIGURE 19.3).

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power technologies. Solar radiation also helps drive wind and the water cycle, enabling us to harness wind power and hydroelectric power. And of course, sunlight drives photosynthesis (p. 50) and the growth of plants, from which we take wood and other biomass as a fuel source. When plants and other organisms die and are buried in sediments under particular conditions, their stored chemical energy may eventually be transferred to fossil fuels, highly combustible substances formed from the remains of organisms from past geologic ages. Today we rely on three main fossil fuels, in the form of a solid (coal), liquid (oil), and gas (natural gas). In addition, a great deal of energy emanates from Earth’s core, making geothermal power available for our use. Energy also results from the gravitational pull of the moon and sun, and we are just beginning to harness power from the ocean tides that these forces generate. Finally, an immense amount of energy resides within the bonds among protons and neutrons in atoms, and this energy provides us with nuclear power. We explore all these energy sources as alternatives to fossil fuels in Chapters 20 and 21. Energy sources such as sunlight, geothermal energy, and tidal energy are considered perpetually renewable because they are readily replenished, so we can keep using them without depleting them (pp. 21–22). In contrast, energy sources such as coal, oil, and natural gas are considered nonrenewable. These nonrenewable fuels result from ongoing natural processes, but it takes so long for fossil fuels to form that, once depleted, they cannot be replaced within any time span useful to our civilization. It takes a thousand years for the biosphere to generate the amount of organic matter that must be buried to produce a single day’s worth of fossil fuels for our society. To replenish the fossil fuels we have depleted so far would take many millions

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Products and other uses

Imports Transportation Oil

Imports

Export Industrial

Natural gas

Export Export

Commercial

Coal Residential Imports

Nuclear

Renewables Electricity generation

Production and imports

Lost energy

Consumption

Losses

FIGURE 19.3 Total energy flow of the United States. Amounts are represented by the thickness of each bar. Domestic production and imports are shown on the left, and destinations of the energy are shown on the right. Portions of each energy source are used directly in the residential, commercial, industrial, and transportation sectors. Other portions are used to generate electricity, which in turn powers these sectors. The large amounts of energy lost as waste heat are shown on the right. Data are for 2012, from U.S. Energy Information Administration and Lawrence Livermore National Laboratory.

Energy sources and consumption are unevenly distributed

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A world map of per capita consumption rates shows that citizens of developed regions generally consume far more energy than do those of developing regions (FIGURE 19.4). Per person, the most industrialized nations use up to 100 times more energy than do the least industrialized nations. The United States has only 4.4% of the world’s population, but it consumes nearly 19% of the world’s energy. The origins of most energy sources also are unevenly distributed over Earth’s surface. Some regions have substantial

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reserves of oil, coal, or natural gas, whereas others have very few. Half the world’s proven reserves of crude oil lie in the Middle East. The Middle East is also rich in natural gas, but Russia holds more natural gas than any other country. Russia is also rich in coal, as is China, but the United States possesses the most coal of any nation (TABLE 19.2).

It takes energy to make energy We do not simply get energy for free. To harness, extract, process, and deliver the energy we use, we need to invest

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The average U.S. citizen uses 7.28 tons per year

Energy consumption per capita (metric tons oil equivalent) 0.0–1.5 1.5–3.0 3.0–4.5 4.5–6.0 over 6.0

The average person in the world uses 1.76 tons per year

FIGURE 19.4 People in wealthy industrialized nations tend to consume the most energy per person. This map combines all types of energy, standardized to metric tons of “oil equivalent,” that is, the amount of fuel needed to produce the energy gained from combusting one metric ton of crude oil. Data from BP p.l.c., 2012. Statistical review of world energy 2012.

How many times more energy does the average U.S. citizen use than the average person in the world?

Net energy 5 Energy returned 2 Energy invested

When assessing energy sources, it is useful to use a ratio often denoted as EROI—energy returned on investment. EROI ratios are calculated as follows: EROI 5 Energy returned/ Energy invested Higher EROI ratios mean that we receive more energy from each unit of energy that we invest. Fossil fuels are widely used because their EROI ratios have historically been high. However, EROI ratios can change over time. Ratios rise as the technology to extract and process fossil fuels improves, and they fall as resources are depleted and remaining resources become harder to extract. EROI ratios for producing conventional oil and natural gas in the United States declined from roughly 30:1 in the 1950s to about 20:1 in the 1970s, and today they hover around 11:1

TABLE 19.2 Nations with the Largest Proven Reserves of Fossil Fuels OIL (% world reserves)

NATURAL GAS (% world reserves)

COAL (% world reserves)

Venezuela*

17.9

Russia

21.4

United States

27.6

Saudi Arabia

16.1

Iran

15.9

Russia

18.2

Canada

10.6

13.3

Qatar

12.0

China

Iran

9.1

Turkmenistan

11.7

Australia

8.9

Iraq

8.7

United States

4.1

India

7.0

*

Most reserves in Venezuela and Canada consist of oil sands, which are included in these figures. Data from BP p.l.c., 2012. Statistical review of world energy 2012.

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substantial inputs of energy. For instance, mining oil sands in Alberta requires extensive use of powerful vehicles and heavy machinery, as well as construction of an immense infrastructure of roads, pipelines, waste ponds, storage tanks, water intakes, processing facilities, housing for workers, and more— all requiring the use of energy. Natural gas must be burned to heat the water that is used to separate the bitumen from the sand. Processing and piping the oil away from the extraction site, and then refining it into products we can use, requires further energy inputs. Thus, when evaluating an energy source, it is important to take energy inputs into consideration by subtracting costs in energy invested from the benefits in energy received. Net energy expresses the difference between energy returned and energy invested:

*

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70 60

EROI

50

30 20

1400

10

1200

0

1000 EROI

40

50 960 970 980 990 000 010 1 2 1 2 1 1 Year

19

800 600 400 200 0

10 920 930 940 950 960 970 980 990 000 010 2 1 1 1 1 2 1 1 1 1 Year

19

FIGURE 19.5 EROI values for discovering oil and gas in the United States have declined over the past century. Data from Guilford, M., et al., 2011. A new long term assessment of energy return on investment (EROI) for U.S. oil and gas discovery and production. Pp. 133–154 in Sustainability, Special Issue, 2011, eds. C. Hall and D. Hansen, New studies in EROI (Energy return on investment).

(FIGURE 19.5). This means that we used to be able to gain 30 units of energy for every unit of energy expended, but now we can gain only 11. EROI ratios for oil and gas declined because we extracted the easiest deposits first and now must work harder and harder to extract the remaining amounts. For the Alberta oil sands, EROI ratios are still lower, because oil sands are a lowquality fuel that requires a great deal of energy to extract and process. EROI estimates for oil sands from studies so far range from 1.5:1 to 9:1, with most estimates around 3:1 to 5:1.

Where will we turn in the future for energy?

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Throughout the 20th century, abundant and inexpensive coal, oil, and natural gas powered the astonishing advances of our civilization. These extraordinarily rich sources of energy helped to bring us a standard of living our ancestors could scarcely have imagined. We began by extracting the fossil fuel deposits that were readily located and accessed, and we took advantage of boundless energy at cheap prices. Yet because fossil fuel deposits are finite and nonrenewable, we gradually began depleting them. As easily accessible supplies of the three main fossil fuels became depleted, EROI ratios rose, and fuels became more expensive. In response, we have developed technology to reach deeper and farther, expending more money and energy in order to continue obtaining fossil fuel energy. We have returned to sites that were already extracted, bringing powerful new machinery and approaches to squeeze more fuels from known locations. We are now reaching into formerly inaccessible places by drilling deeper, moving further offshore,

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and exploring the seabed of the Arctic. We are also using more potent extraction methods, such as hydraulic fracturing (pp. 180–181), to free gas from rock layers. And we are pursuing new types of fossil fuels, including oil sands, shale oil, and methane hydrates. These fuels are more expensive and lower in quality, but they are increasingly being extracted as market prices of fossil fuels rise and make their extraction profitable. There is, however, another way we can respond to the depletion of conventional fossil fuel resources. This is to hasten the development of clean and renewable energy sources to replace them. By transitioning away from fossil fuels and toward renewable sources, we can gain energy that is sustainable in the long term while greatly reducing pollution, health impacts, and the emission of greenhouse gases that drive climate change (Chapters 18, 20, and 21). This transition has begun to occur, but it is apparent that we will continue to gain much of our future energy from fossil fuels. Alas, so far our ability to control pollution has lagged behind our capacity to consume energy. Many scientists now warn that if we do not immediately step up energy conservation and accelerate our shift to renewables, we will drive our planet’s climate into unprecedented territory, threatening impacts on our economy, our quality of life, and our society’s future.

Fossil Fuels and Their Extraction The three conventional fossil fuels on which our modern industrial society was built, and on which we rely today, are coal, natural gas, and oil. Additional fossil fuels we are beginning to extract or considering for the future include oil sands, shale oil, and methane hydrates. We will first consider how each of these fossil fuels is formed, how we locate deposits, how we extract these resources, and how our society puts them to use. We will then examine some of their environmental and social impacts.

Fossil fuels are formed from ancient organic matter The fossil fuels we burn today in our vehicles, homes, industries, and power plants were formed from the tissues of organisms that lived 100–500 million years ago. The energy these fuels contain came originally from the sun and was converted to chemical-bond energy by photosynthesis. The chemical energy in these organisms’ tissues then became concentrated as these tissues decomposed and their hydrocarbon compounds were altered and compressed (FIGURE 19.6). Most organisms, after death, do not end up as part of a coal, gas, or oil deposit. A tree that falls and decays as a rotting log on the forest floor undergoes mostly aerobic decomposition; in the presence of air, bacteria and other organisms that use oxygen break down plant and animal remains into simpler carbon molecules that are recycled through the ecosystem. Fossil fuels are produced only when organic material is broken down in an anaerobic environment, one that has little or no oxygen. Such environments include the bottoms of lakes, swamps, and shallow seas. Over millions of years, organic matter that accumulates at the bottoms of such water bodies may be converted into crude oil, natural gas, or coal, depending on (1) the

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Woody terrestrial vegetation dies and falls into swamp

Ancient swamp Ancient ocean Organic matter from woody land plants is partly decomposed by microbes under accumulating sediments; kerogen forms

Anaerobic conditions

Phytoplankton, zooplankton, and other marine organisms die and sink to seafloor

Organic matter from soft-bodied sea life is partly decomposed by microbes under accumulating sediments; some carbon bonds are broken; kerogen forms

Heat and pressure deep underground alter kerogen

Present day

Crude oil formed from kerogen

FIGURE 19.6 Fossil fuels begin to form when organisms die and end up in oxygen-poor conditions. This can occur when trees fall into lakes and are buried by sediment, or when phytoplankton and zooplankton drift to the seafloor and are buried (top diagram). Organic matter that undergoes slow anaerobic decomposition deep under sediments forms kerogen (middle diagram). Coal results when plant matter is compacted so tightly that there is little decomposition (bottom left diagram). The action of geothermal heating on kerogen may create crude oil and natural gas (bottom right diagram), which come to reside in porous rock layers beneath dense, impervious layers.

chemical composition of the material, (2) the temperatures and pressures to which it is subjected, (3) the presence or absence of anaerobic decomposers, and (4) the passage of time.

Coal   The world’s most abundant fossil fuel is coal, a hard blackish substance formed from organic matter (generally woody plant material) that was compressed under very high pressure, creating dense, solid carbon structures (FIGURE 19.7). Coal typically results when little decomposition takes place because the material cannot be digested or appropriate decomposers are not present. The proliferation 300–400 million years ago of swampy environments where organic material was buried has created coal deposits throughout the world.

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Oil and natural gas   The sludgelike liquid we know as oil, or crude oil, contains a mixture of hundreds of different types of hydrocarbon molecules (p. 46). Natural gas is a gas consisting primarily of methane (CH4) and including varying amounts of other volatile hydrocarbons. Oil is also known as petroleum, although this term is commonly used to refer to oil and natural gas collectively. Both oil and natural gas are formed from organic material (especially dead plankton) that drifted down through coastal marine waters millions of years ago and was buried in sediments on the ocean floor. As organic matter is buried more deeply, the pressure exerted by overlying sediments grows, and temperatures increase. Carbon bonds in the organic matter begin breaking, and the organic matter turns to a substance called kerogen, which acts as a source material for both natural gas and crude oil. Further heat and pressure act on the kerogen to degrade complex organic molecules into simpler hydrocarbon molecules. Oil tends to form under temperature and pressure conditions often found 1.5–3 km (1–2 mi) below the surface. At depths below 3 km (1.9 mi), the high temperatures and pressures tend to form natural gas. Natural gas that forms in this way from compression and heat deep underground is called thermogenic gas. Thermogenic gas may be formed directly, or from coal or oil that is altered by heating. Most gas extracted commercially is thermogenic and is found above deposits of crude oil or seams of coal, so its extraction often accompanies the extraction of those fossil fuels. Natural gas is also formed by a second process; biogenic gas is created at shallow depths by the anaerobic decomposition of organic matter by bacteria. An example is the “swamp gas” you may smell when stepping into the muck of a swamp. One source of biogenic natural gas is the decay process in landfills, and many landfill operators are now capturing this gas to sell as fuel (p. 634). Biogenic gas is nearly pure methane, whereas thermogenic gas contains small amounts of other gases as well as methane.

Oil sands   As we’ve seen, oil sands (also called tar sands) consist of moist sand and clay containing 1–20% bitumen, a thick and heavy form of petroleum that is rich in carbon and poor in hydrogen. Oil sands represent crude oil deposits that have been degraded and chemically altered by water erosion and bacterial decomposition. The leading scientific hypothesis to explain Alberta’s oil sands is that geological changes tens of millions of years ago as the Rocky Mountains were uplifted allowed crude oil deposits to migrate northeastward and upward until they saturated rock and soil in what is now

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Thermogenic natural gas formed from kerogen

Coal formed from kerogen

Coal varies from deposit to deposit in the amount of water, carbon, and potential energy it contains. Organic material that is broken down anaerobically but remains wet, near the surface, and not well compressed is called peat. As peat decomposes further, as it is buried under sediments, as heat and pressure increase, and as time passes, water is squeezed out and carbon compounds are packed more tightly together, forming coal. Scientists classify coal into four types (see Figure 19.7). The more coal is compressed, the greater is its carbon content and the greater is the energy content per unit volume.

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FIGURE 19.7 Coal forms as ancient plant matter turns to peat and then is compressed underground. Of the four classes of coal, lignite coal forms under the least pressure and heat and retains the most moisture. Anthracite coal is formed under the greatest pressure, where temperatures are high and moisture content is low. Anthracite coal has the densest carbon content and so contains the most potential energy.

Time

Ancient forest

Decreasing moisture Increasing heat and pressure

Peat

Lignite

Subbituminous

northeast Alberta. Microorganisms (which are abundant near the surface but absent at depth) began to consume the oil, particularly the lighter components, leaving degraded heavy bitumen.

Oil shale  Oil shale is sedimentary rock filled with kerogen that can be processed to produce a liquid form of petroleum called shale oil. Oil shale is formed by the same processes that form crude oil but occurs when kerogen was not buried deeply enough or subjected to enough heat and pressure to form oil.

Methane hydrate  Methane hydrate occurs in sediments in the Arctic and on the ocean floor. Also called methane clathrate or methane ice, this fossil fuel is an ice-like solid consisting of molecules of methane embedded in a crystal lattice of water molecules. Methane hydrate is stable at temperature and pressure conditions found in many sediments in the Arctic and on the seafloor. Most methane in these gas hydrates formed from bacterial decomposition in anaerobic environments, but some resulted from thermogenic formation deeper below the surface.

We mine and drill for fossil fuels

544

Because fossil fuels of each type form only under certain conditions, they occur in isolated deposits. For instance, oil and natural gas tend to rise upward through cracks and fissures in porous rock until meeting a dense impermeable rock layer that traps them. As a result, geologists search for fossil fuels by drilling cores and conducting ground, air, and seismic surveys to map underground rock formations. With knowledge of underground geology, they can predict where fossil fuel deposits might lie (see THE SCIENCE BEHIND THE STORY, pp. 548–549).

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Bituminous

Anthracite

Once geologists have identified a promising location for a deposit of oil or natural gas, a company will typically conduct exploratory drilling, drilling small holes that descend to great depths. If enough oil or gas is encountered, extraction begins. Just as you would squeeze a sponge to remove its liquid, pressure is required to extract oil from porous rock. Oil is typically already under pressure—from above by rock or trapped gas, from below by groundwater, and at times internally from natural gas dissolved in the oil. All these forces are held in check by surrounding rock until drilling reaches the deposit, whereupon oil will often rise to the surface of its own accord. Once pressure is relieved and some oil or gas has risen to the surface, however, the remainder becomes more difficult to extract and needs to be pumped out. Coal is a solid, and so we mine it rather than drilling for it. For coal deposits near the surface, we use strip mining, in which heavy machinery scrapes away huge amounts of earth to expose the coal. For deposits deep underground, we use subsurface mining, digging vertical shafts and blasting out networks of horizontal tunnels to follow seams, or layers, of coal. (Strip mining and subsurface mining are illustrated in Figure 23.6, p. 657.) We are also now mining coal on immense scales in the Appalachian Mountains, essentially scraping off entire mountaintops in a process called mountaintop removal mining (pp. 659–663). Oil from oil sands is extracted by two main methods. For deposits near the surface (FIGURE 19.8a), a process akin to strip mining for coal or open-pit mining for minerals (p. 658) is used. Shovel-trucks peel back layers of peat and soil and then dig out vast quantities of bitumen-soaked sand or clay. This is mixed with hot water and piped to an extraction facility, where sand sinks to the bottom of tanks while bitumen floats to the top. The bitumen is skimmed off, solvent is added, and the mixture is spun in a centrifuge to further purify the bitumen, which is then processed into crude oil. Three barrels of water are required to extract each barrel of oil, and the resulting toxic wastewater is discharged into vast tailings lakes.

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2 Material is poured into a crushing machine.

Storage silo Crusher

Rotary breaker

Separation Unit

Froth treatment

3 Hot water is added.

1 Deposits are strip-mined.

4 Bitumen rises

to top of slurry.

5 Bitumen is skimmed off, 6 Synthetic crude is

piped to a refinery.

mixed with solvents, and processed into synthetic crude oil.

Oil sands

1 Steam and solvents

are injected into underground deposits

2 Liquefied bitumen is pumped up to surface

(b) In-situ steam extraction

FIGURE 19.8 Oil sands are extracted by two processes. Near-surface deposits of oil sands (a) are stripmined. The deposits are first dug out 1 with gigantic shovels and trucks and then poured into a crushing machine 2 . The material is then mixed with hot water 3 , and the slurry is piped to a facility where the bitumen floats in a froth atop water in a tank 4 , while sand and clay settle out. The bitumen froth is skimmed off, mixed with chemical solvents, and processed into synthetic crude oil 5 ; it is then sent in a pipeline 6 to a refinery. Deeper deposits of oil sands (b) are extracted through well shafts. Pressurized steam is injected down the well 1 into the oil sand formation, liquefying the bitumen and allowing it to be pumped 2 to the surface.

Oil sands that are deeper underground (FIGURE 19.8b) are extracted by drilling shafts down to the deposit and injecting steam and solvents down to liquefy and isolate the bitumen in place, then pump it out. After extraction, the bitumen must be refined using chemical reactions that add hydrogen or remove carbon, thus upgrading it into more valuable synthetic crude oil (called syncrude). We mine oil shale using strip mines or subsurface mines. Once mined, oil shale can be burned directly like coal, or it can be baked in the presence of hydrogen and in the absence of air to extract liquid petroleum (a process called pyrolysis).

Economics determines how much will be extracted As we develop more powerful technologies for locating and extracting fossil fuels, the amounts of these fuels that are physically accessible to us—the “technically recoverable” amounts— tend to increase. However, whereas technology determines how much of a fossil fuel can be extracted, economics determines

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how much will be extracted. This is because extraction becomes increasingly costly as a resource is removed, so companies will not find it profitable to extract the entire amount. Instead, a company will consider the costs of extraction (and other expenses), and balance these against the income it expects from sale of the fuel. Because market prices of fuel fluctuate, the portion of fuel from a given deposit that is “economically recoverable” fluctuates as well. As market prices rise, economically recoverable amounts approach technically recoverable amounts. The amount of a fossil fuel that is technologically and economically feasible to remove under current conditions is termed its proven recoverable reserve. Proven reserves increase as extraction technology improves or as market prices of the fuel rise. Proven reserves decrease as fuel deposits are depleted by extraction or as market prices fall (making extraction uneconomical).

Refining produces a diversity of fuels Once we extract oil or gas, it must be processed and refined before we can use it. Let’s examine what happens when crude

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(a) Strip-mining method

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Distillation column Boiling temp. Less than 5ºC

20–180ºC

20–200ºC

Crude oil

180–260ºC

260–340ºC

300–370ºC

370–600ºC

Product Butane

Naphtha

Gasoline

Kerosene

Diesel

Lubricating oil

Fuel oil

(a) Distillation columns Boiler

Residue

(b) Distillation process Gasoline (48.5%)

Diesel fuel and heating oil (24.1%) Jet fuel (7.8%) Liquefied petroleum gases (3.3%) Heavy fuel oil (2.9%) Other (13.4%) (c) Typical composition of refined oil

FIGURE 19.9 The refining process produces a range of petroleum products. At oil refineries (a), crude oil is boiled, causing its many hydrocarbon constituents to volatilize and proceed upward (b) through a distillation column. Constituents that boil at the hottest temperatures and condense readily once the temperature cools will condense at low levels in the column. Constituents that volatilize at cooler temperatures will continue rising through the column and condense at higher levels, where temperatures are cooler. In this way, heavy oils (generally those with hydrocarbon molecules with long carbon chains) are separated from lighter oils (generally those with short-chain hydrocarbon molecules). Shown in (c) are percentages of each major category of product typically generated from a barrel of crude oil. Data (c) from U.S. Energy Information Administration, 2012. Annual energy review 2011.

oil is shipped to a refinery (FIGURE 19.9). Because crude oil is a complex mix of hydrocarbons, we can create many types of petroleum products by separating its various components. The many types of hydrocarbon molecules in crude oil have carbon chains of different lengths (p. 46). A chain’s length affects its chemical properties, and this has consequences for our use, such as whether a given fuel burns cleanly in a car engine. Through the process of refining, hydrocarbon molecules are separated into different size classes and are chemically transformed to create specialized fuels for heating, cooking, and transportation, and to create lubricating oils, asphalts, and the precursors of plastics and other petrochemical products.

Fossil fuels have many uses 546

As we saw in Figure 19.3, each major type of fossil fuel has its own mix of uses. Let’s survey how coal, oil, and natural gas each are used in our society today.

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Coal   People have burned coal to cook food, heat homes, and fire pottery for thousands of years and in many cultures, from ancient China to the Roman Empire to the Hopi Nation. Coal-fired steam engines helped drive the industrial revolution by powering factories, agriculture, trains, and ships, and by fueling the furnaces of the steel industry. Today we burn coal largely to generate electricity. In coal-fired power plants, coal combustion converts water to steam, which turns a turbine to create electricity (FIGURE 19.10). Coal provides 40% of the electrical generating capacity of the United States, and it powers China’s surging economy. China is now the world’s primary producer and consumer of coal (TABLE 19.3).

Natural gas  Versatile and clean-burning, natural gas emits just half as much carbon dioxide per unit of energy produced as coal and two-thirds as much as oil. We use natural gas to generate electricity in power plants, to heat and cook in our homes, and for much else. Converted to a liquid

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Turbine

Generator

Boiler

Cooling tower Cooling loop Condenser

Coal bunker

Pulverizing mill Filter Stack Furnace

Ash disposal

FIGURE 19.10 At a coal-fired power plant, coal is pulverized and blown into a high-temperature

TABLE 19.3 T op Producers and Consumers of Fossil Fuels PRODUCTION (% world production)

CONSUMPTION (% world consumption) COAL

China

49.5

United States

14.1

China

49.4

United States

13.5

Australia

5.8

India

7.9

India

5.6

Japan

3.2

Indonesia

5.1

South Africa

2.5

OIL Saudi Arabia

13.2

Russia

United States

20.5

12.8

China

11.4

United States

8.8

Japan

5.0

Iran

5.2

India

4.0

China

5.1

Russia

3.4

NATURAL GAS United States

20.0

United States

21.5

Russia

18.5

Russia

13.2

Canada

4.9

Iran

4.7

Iran

4.6

China

4.0

Qatar

4.5

Japan

3.3

Data from BP p.l.c., 2012. Statistical review of world energy 2012.

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at low temperatures (liquefied natural gas, or LNG), it can be shipped long distances in refrigerated tankers. When we replace coal with natural gas to generate electricity, this cuts carbon emissions in half. For this reason, many energy experts view natural gas as a “bridge fuel”—a bridge leading from today’s polluting fossil-fuel economy toward a clean renewable energy economy for the future. The United States and Russia lead the world in gas production and gas consumption (see Table 19.3).

Oil  The modern use of oil for energy began after 1859, when the world’s first oil well was drilled in Titusville, Pennsylvania. Over the next 40 years, Pennsylvania’s oil fields produced half the world’s oil supply and helped establish a fossil-fuel-based economy that would hold sway for decades to come. Today our global society produces and consumes nearly 750 L (200 gal) of oil each year for every man, woman, and child. The majority is used as fuel for vehicles, including gasoline for cars, diesel for trucks, and jet fuel for airplanes. Fewer homes burn oil for heating these days, but industry and manufacturing still account for a great deal of oil use. Over the past several decades, refining techniques and chemical manufacturing have greatly expanded our uses of petroleum to include a wide array of products and applications, from plastics to lubricants to fabrics to pharmaceuticals. In today’s world, petroleum-based products are all around us

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furnace. Heat from the combustion boils water, and the resulting steam turns a turbine, generating electricity by passing magnets past copper coils. The steam is then cooled and condensed in a cooling loop and returned to the furnace. “Clean coal” technologies (p. 555) help filter pollutants from the combustion process, and toxic ash residue is taken to hazardous waste disposal sites.

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THE SCIENCE BEHIND THE STORY Locating Fossil Fuel Deposits Underground Drilling for oil or gas is risky business: Most wells are unproductive, and a company that doesn’t pick its spots effectively could soon go bankrupt. So oil and gas companies turn to scientists to help them figure out where to drill. The industry employs petroleum geologists who study underground rock formations to predict where deposits of oil and natural gas might lie. Because the organic matter that gave rise to fossil fuels was buried in sediments, geologists know to look for sedimentary rock that may act as a source. They also know that oil and gas tends to seep upward through porous rock until being trapped by impermeable layers. To map subsurface rock layers, petroleum geologists first survey the landscape on the ground and from airplanes, studying rocks on the surface. Because rock layers often become tilted over geologic time, these strata may protrude at the surface, giving geologists an informative “side-on” view. But to really understand what’s deep beneath the surface, scientists need to conduct seismic surveys. In seismic surveying, a base station creates powerful vibrations at the surface by exploding dynamite, thumping the ground with a large weight, or using an electric vibrating machine (FIGURE 1). This sends seismic waves down and outward in all directions through the ground, just as ripples spread when a pebble is dropped into a pond. As they travel, the waves encounter layers of different types of rock. The waves travel more quickly through

548

Petroleum geologists study mapped seismic data to determine where oil or gas might be found.

Vibration source

Receivers

Less dense layer (sound travels more slowly)

More dense layer (sound travels more quickly) Reflection paths (red)

Refraction paths (blue)

FIGURE 1 Seismic surveying provides clues to the location and size of fossil fuel deposits. Powerful vibrations are created, and receivers measure how long it takes seismic waves to reach other locations. Waves travel more quickly through denser layers, and density differences cause waves to reflect or refract. Scientists interpret the patterns of wave reception to infer the densities, thicknesses, and locations of underlying rock layers.

in our everyday lives (FIGURE 19.11). The fact that petroleum is used to create so many items and materials we have come to rely on makes it vital that we take care to conserve our remaining oil reserves. The United States consumes one-fifth of the world’s oil, but rapidly industrializing populous nations such as China and India are increasingly driving world demand (see Table 19.3).

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denser rock. Each time a seismic wave encounters a new type of rock with a different density, some of the wave’s energy is reflected off the boundary, and the rest passes through the boundary into the new layer. Some wave energy may be refracted, or bent, along the edge of the layer, sending refraction waves upward. As reflected and refracted waves return to the surface, devices called seismometers (also used to measure earthquakes) record data on their strength and precise timing. Scientists collect data from seismometers at multiple surface locations and run the data through computer programs for analysis. By analyzing how long it takes all the reflected and refracted seismic waves to reach the various

We are gradually depleting fossil fuel reserves Because fossil fuels are nonrenewable, the total amount available on Earth declines as we use them. Many scientists and oil industry analysts calculate that we have already extracted half the world’s conventional oil reserves. So far we have used up about 1.1 trillion barrels of oil, and most estimates hold that

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National Petroleum Reserve - Alaska

ALASKA

Arctic National Wildlife Refuge

Trans-Alaska pipeline

CANADA

Anchorage Valdez

Total oil

FIGURE 2 Surveys have given us data on how much oil may underlie Alaska’s North Slope. Of the total oil scientists estimate to exist in the area of the Arctic NWR that may someday be opened to drilling, only some is technically recoverable, and less is economically recoverable. Data from U.S. Geological Survey.

the Arctic Refuge, the USGS calculated technically recoverable oil to total 4.3–11.8 billion barrels, with a mean estimate of 7.7 billion barrels (just over 1 year of U.S. consumption). The portion of this oil that is “economically recoverable” depends on the costs of extracting it and the price of oil on the world market. USGS scientists calculated that at a price of $40 per barrel, 3.4–10.8 billion barrels would be economically worthwhile to recover. At today’s much higher prices, the economically recoverable amount would be closer to the technically recoverable amount.

slightly more than 1 trillion barrels of proven reserves remain. Adding proven reserves of oil sands from Canada and Venezuela brings the total remaining to just over 1.6 trillion barrels. To estimate how long this remaining oil will last, analysts calculate the reserves-to-production ratio, or R/P ratio, by dividing the amount of total remaining reserves by the annual rate of production (i.e., extraction and processing). At current levels of production (30 billion barrels globally per year),

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Prudhoe Bay

Technically recoverable oil

Economically recoverable oil (at $40/barrel)

0 5 10 15 20 25 30 35 Billion barrels of oil, estimated

In 2002, the USGS conducted similar analyses for the National Petroleum Reserve–Alaska, a vast parcel of tundra to the west of the Arctic Refuge and Prudhoe Bay that the U.S. government set aside 90 years ago as an emergency reserve of petroleum. USGS scientists estimated that this region contained 9.3 billion barrels of technically recoverable oil. Across the world, petroleum geologists are using similar methods to try to determine how much oil remains to extract. Their work is of vital importance as the world’s nations struggle to pursue well-informed energy policies.

1.6 trillion barrels would last about 54 more years. Applying the R/P ratio to natural gas, we find that the world’s proven reserves of this resource would last 64 more years. For coal, the latest R/P ratio estimate is 112 years. The true number of years remaining for these fuels may be less than these figures suggest, however, because our demand and production have been increasing, not constant. Yet at the same time, the true number of years may be more

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receiving stations, and how strong the waves are at each site, researchers can triangulate and infer the densities, thicknesses, and locations of underlying geologic layers. Seismic surveying is similar to how we use sonar in water or how bats use echolocation as they fly. It is also used for finding coal deposits, salt and mineral deposits, and geothermal energy hotspots, as well as for studying faults, aquifers, and engineering sites. Still, even with good survey data, oil companies may have only a 10% success rate in finding oil or gas. They need to conduct exploratory drilling to confirm whether oil or gas actually exists in any given location. Using data from such techniques, geologists with the U.S. Geological Survey (USGS) in 1998 assessed the subsurface geology of the Arctic National Wildlife Refuge on Alaska’s North Slope to predict how much oil it may hold (FIGURE 2). Over three years, dozens of scientists conducted fieldwork and combined their results with a reanalysis of 2300 km (1400 mi) of seismic survey data that industry had collected in the 1980s. After studying their resulting subsurface maps, USGS scientists concluded, with 95% certainty, that between 11.6 and 31.5 billion barrels of oil lay underneath the region of the refuge that Congress has debated opening for drilling. The mean estimate of 20.7 billion barrels is enough to supply the United States for 3 years at its current rate of consumption. However, some portion of oil from any deposit is impossible to extract using current technology, so geologists estimate “technically recoverable” amounts of fuels. In its estimate for

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Cosmetics, Shower Nylon and Light switch Pesticides Tires, upholstery, Plastic Containers Nonstick coating medicines, curtain polyester and and automobile lampshade on cookware lotions, clothing fertilizers components Paraffin waxes and soap Shower Plastic picture Bicycle Plastic cups on fruit, candy, Toothbrush head Gasoline frame components Asphalt and dishware and other food

Plastic Shoes with Plastic storage Vinyl and plastic Home heating oil Blender and other Components of wastebasket synthetic soles box laminate furniture to heat house small appliances stove and other Detergents, Polypropylene CDs and DVDs Components Linoleum large appliances cleaning supplies Toilet seat coat in TV and stereo flooring

FIGURE 19.11 Petroleum products are everywhere in our daily lives. Besides the fuels we use for transportation and heating, petroleum is used to make many of the fabrics we wear, the materials we consume, and the plastics in countless items we use every day.

than these figures suggest, because proven reserves tend to increase as technology becomes more powerful and as market prices rise. Indeed, mining for oil sands and hydraulic fracturing for natural gas in recent years have increased the proven reserves of these fuels in North America substantially. In fact, advances in oil and gas extraction in the United States in the past several years have been so great that the International Energy Agency in 2012 predicted a resurgence would make the United States the world’s biggest oil producer into the 2020s. Regardless of how many years’ worth of a resource we might calculate to be left, a society dependent on that resource will face a crisis not when the last bit of it is extracted from the ground, but rather once the rate of its production comes to a peak and begins to decline. In general, production of a resource tends to decline once reserves are depleted halfway. Past this production peak, if demand for the resource holds steady or continues to increase while production declines, a shortage will result. Many scientists and economists have been anxious about this phenomenon with oil, and the scenario has come to be nicknamed peak oil. Because we have already used roughly half of Earth’s conventional oil reserves, many experts calculate that a peak oil crisis may well begin in the very near future.

Peak oil will pose challenges

550

To understand concerns about peak oil, we need to turn back the clock to 1956. In that year, Shell Oil geologist M. King Hubbert calculated that U.S. oil production would peak around 1970. His prediction was ridiculed at the time, but it proved to

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be accurate; U.S. production peaked in that very year and has fallen since then (FIGURE 19.12a). The peak in production came to be known as Hubbert’s peak. In 1974, Hubbert analyzed data on technology, economics, and geology, and predicted that global oil production would peak in 1995. It grew past 1995, but many scientists using newer data today predict that at some point in the coming decade, production will begin to decline (FIGURE 19.12b). Discoveries of new oil fields peaked 30 years ago, and since then we have been extracting and consuming more oil than we have been discovering.

FAQ

Why should I worry about “peak oil” if there are still years of oil left?

Bear in mind that the term peak oil doesn’t refer to running out of oil. It refers to the point at which our production of oil comes to a peak. Once we pass this peak and production begins to decline, the economics of supply and demand take over. Supply will fall, with some estimates putting the decline at 5% per year. Demand, meanwhile, is forecast to continue rising, especially as China, India, and other industrializing nations put millions of new vehicles on the road. The resulting divergence of supply and demand would drive up oil prices, causing substantial economic ripple effects. Although high oil prices will provide financial incentive to develop alternative energy sources and better conservation measures, we may be challenged in a depressed economy to find adequate time and resources to develop new renewable sources.

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Billions of barrels/year

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Hubbert’s prediction assuming 200 billion barrels of discoverable oil

Actual U.S. oil production

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Hubbert’s prediction assuming 150 billion barrels of discoverable oil

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(a) Hubbert’s prediction of peak in U.S. oil production, with actual data

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Natural gas liquids Polar oil Deep-water oil Heavy oil Middle East Other Russia Europe Lower 48 U.S. states

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(b) Modern prediction of peak in global oil production

FIGURE 19.12 Peak oil describes a peak in production. U.S. oil production peaked in 1970 (a), just as geologist M. King Hubbert had predicted. Since then, success in Alaska, in the Gulf of Mexico, and with secondary extraction has enhanced production during the decline. (Note that curves shift to the right and peaks increase in height as more oil is discovered.) Today U.S. oil production is spiking upward as deep offshore drilling and hydraulic fracturing make new deposits accessible. Still, some analysts believe global oil production will soon peak. Shown in (b) is one recent projection, from a 2011 analysis by scientists at the Association for the Study of Peak Oil. Data from (a) Hubbert, M.K., 1956. Nuclear energy and the fossil fuels. Shell Development Co. Publ. No. 95, Houston, TX; and U.S. Energy Information Administration; and (b) Campbell, C.J., and Association for the Study of Peak Oil. By permission of Dr. Colin Campbell.

Discovery or development of wholly new sources of oil can delay the peak by boosting our overall proven reserves. This is what is happening as we exploit Canada’s oil sands. People counting on a series of new sources in the future tend to believe we can continue relying on oil for a long time, and this may indeed turn out to be the case. However, at some point we will reach peak oil—and peak gas and peak coal. The question is when—and whether we will be prepared to deal with the resulting challenges. Predicting an exact date for peak oil is difficult. Many companies and governments do not reveal their true data on oil reserves, and estimates differ as to how much oil we can extract secondarily from existing deposits. Indeed, a recent

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U.S. Geological Survey report estimated 2 trillion barrels of conventional oil remaining in the world, rather than 1 trillion, and some estimates predict still greater amounts. A 2007 report by the U.S. General Accounting Office reviewed 21 studies and found that most estimates for the timing of the oil production peak ranged from now through 2040. Whenever it occurs, the divergence of supply and demand could have momentous economic, social, and political consequences that will profoundly affect our lives. One prophet of peak oil, writer James Howard Kunstler, has sketched a frightening scenario of our post-peak world during what he calls “the long emergency”: Lacking cheap oil with which to transport goods long distances, today’s globalized economy

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would collapse into a large number of isolated and intensely localized economies. Large cities would require urban agriculture to feed their residents, and with fewer petroleumbased fertilizers and pesticides we could feed only a fraction of the world’s 7 billion people. The American suburbs would be hit particularly hard because of their dependence on the automobile. More optimistic observers argue that as oil supplies dwindle, rising prices will create powerful incentives for businesses, governments, and individuals to conserve energy and to develop alternative energy sources (Chapters 20 and 21)—and that these developments will save us from major disruptions.

So, companies may return and conduct secondary extraction. In secondary extraction for oil, solvents are used or underground rocks are flushed with water or steam (FIGURE 19.13b). Even after secondary extraction, quite a bit of oil or gas can remain; we lack the technology to remove every last drop. Secondary extraction is more expensive than primary extraction, so many U.S. deposits did not undergo secondary extraction in the past because market prices of oil and gas were too low to make it economical. Once oil prices rose in the 1970s, companies reopened drilling sites for secondary extraction. More are being reopened today.

Or might we end up with “too much” fossil fuel energy? Today renewable energy sources are indeed being developed faster—but we are also reaching farther for fossil fuels. To stave off the day when production of oil, gas, and coal begin to decline, we are investing more and more money, energy, and technology into locating and extracting new fossil fuel deposits. We are reaching further for fossil fuels by pursuing several main approaches: • • • • •

552

Oil rig Oil well

Ocean floor Gas cap

Secondary extraction from existing wells Hydraulic fracturing for oil and shale gas Offshore drilling in increasingly deep waters Moving into ice-free waters of the Arctic Exploiting new “unconventional” fossil fuel sources

Oil in pores of rocks

Development of the Canadian oil sands will swell the amount of oil available to us and thereby extend the period during which we can rely on oil. And already the United States is seeing increased production from deep offshore drilling, hydraulic fracturing, and secondary extraction—so much so that energy experts now project that within a decade the United States may be exporting more oil than Saudi Arabia! As we extend our reach into less-accessible places to obtain fuel that is harder to extract, we expand our proven reserves and postpone the threat of peak production. However, we also reduce the EROI ratios of our fuels, drive up fuel prices for consumers, and intensify pollution and climate change. Indeed, the threat of climate change is serious enough that some scientists are beginning to wonder if we should plan to intentionally leave most oil, gas, and coal in the ground. In the long term, to achieve a sustainable society we will need to switch to renewable energy sources. Investments in energy efficiency and conservation (pp. 564–566) are vital because they extend the time we have to make this transition.

(a) Primary extraction of oil

Secondary extraction produces more fuel

(b) Secondary extraction of oil

One way we are reaching further for fossil fuels is by returning to sites where we have already removed easily accessible oil or gas and applying new technology or approaches to extract the remaining amounts. At a typical oil or gas well, as much as twothirds of a deposit may remain in the ground after primary extraction, the initial drilling and pumping of oil or gas (FIGURE 19.13a).

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Impermeable rock

Oil rig

Oil well Seawater injection

Gas injection Ocean floor Gas cap

Pressure

Impermeable rock Oil in pores of rocks

FIGURE 19.13 Secondary extraction removes oil not removed by primary extraction. In primary extraction (a), oil is drawn up through a well by keeping pressure at the top lower than pressure at the bottom. Once pressure in the deposit drops, however, material must be injected to increase the pressure. Secondary extraction (b) involves injecting seawater beneath the oil and/or injecting gases just above the oil to force more oil up and out of the deposit.

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Hydraulic fracturing expands our access to oil and gas

We are drilling farther and farther offshore Today we drill for oil and natural gas not only on land but also below the seafloor on the continental shelves. Offshore drilling platforms must withstand wind, waves, and ocean currents. Some are fixed, standing platforms built with unusual strength. Others are resilient floating platforms anchored in place above the drilling site. Roughly 35% of the oil and 10% of the natural gas extracted in the United States today comes from offshore sites, primarily in the Gulf of Mexico and secondarily off southern California. The Gulf today is home to 90 drilling rigs and 3500 production platforms. Geologists estimate that most U.S. gas and oil remaining to be extracted occurs offshore and that deepwater sites in the Gulf of Mexico alone may hold 59 billion barrels of oil. We have been drilling in shallow water for several decades, but as oil and gas are depleted at shallow-water sites and as drilling technology improves, the industry is moving into deeper and deeper water. This poses risks; the Deepwater Horizon oil spill of 2010 (pp. 454–455, 556–559) occurred at a deepwater site. In that event, faulty equipment allowed natural gas accompanying the oil deposit to shoot up the well shaft. It ignited atop the platform, killing 11 workers and leading to

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FIGURE 19.14 Hydraulic fracturing is expanding U.S. production of oil and natural gas, but it is sparking debates within communities where it is taking place. This drill rig is hydrofracking a shale formation on private land among homes in the rural Hopewell Township of Pennsylvania. Here, some residents support drilling and hope for financial benefits whereas others oppose drilling and fear contamination of their drinking water and damage to their quality of life.

the largest accidental oil spill in history. British Petroleum’s Macondo well, where the accident took place, lay beneath 1500 m (5000 ft) of water. The deepest wells in the Gulf of Mexico are now twice that depth. Globally, recent discoveries off the coasts of Brazil, Angola, Nigeria, and other nations suggest that a great deal of oil and gas could lie well offshore, and companies are racing one another to get there. Unfortunately, our ability to drill in deep water has outpaced our capacity to deal with accidents there. The fact that it took 86 days for BP to plug the leak at its Macondo well demonstrates the challenge of addressing an emergency situation a mile or more beneath the surface of the sea. Today all eyes are on the Arctic. As global climate change melts the sea ice that covers the Arctic Ocean (pp. 516, 521), new shipping lanes are opening and nations and companies are scrambling to lay claim to patches of ocean that could hold fossil fuels and other resources. The oil and gas industry plans to drill offshore in deep water—something that has environmental advocates very worried. The Arctic’s frigid temperatures, ice floes, winds, waves, and brutal storms make conditions harsh and challenging and make accidents more likely. In 2008, responding to rising gasoline prices and a desire to lessen dependence on foreign oil, the U.S. Congress lifted a long-standing moratorium on offshore drilling along much of the nation’s coastline. The Obama administration in 2010 followed through by designating vast areas open for drilling that had formerly been closed. These included most waters along the Atlantic coast from Delaware south to central Florida, a region of the eastern Gulf of Mexico, and most waters off Alaska’s North Slope. However, just weeks after this announcement, the Deepwater Horizon spill occurred. Public reaction forced the Obama administration to backtrack, canceling offshore drilling projects it had approved and

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For oil and for natural gas trapped tightly in impermeable shale deposits, we are now using hydraulic fracturing (see Figure 7.1, p. 181) to break into rock formations and pump the oil or gas to the surface. Hydraulic fracturing (also called hydrofracking, or fracking) is being used for secondary extraction and also to tap into new deposits. This technique involves pumping chemically treated water under high pressure into deep layers of shale to crack them. Sand or small glass beads are inserted to hold the cracks open as the water is withdrawn. Gas or oil then travels upward, with pressure and pumping, through the newly created system of fractures. Hydraulic fracturing allows us to extract gas and oil that is so dispersed through shale formations that it cannot be pumped out by standard drilling. By making formerly inaccessible deposits accessible, hydrofracking has raised proven reserves and has ignited a boom in natural gas extraction in the United States. Natural gas prices have fallen, and gas usage in the United States has risen. Fracking has engendered debate among people living in each area where it has occurred (FIGURE 19.14). For example, hydrofracking of the massive Marcellus Shale deposit is affecting the landscapes, economies, politics, and everyday lives of people in Pennsylvania, New York, and neighboring states (see Chapter 7). The choices people face between financial gain and impacts to their health, drinking water, and environment have been dramatized in popular films such as Promised Land and Gasland. As with Alberta’s oil sands, and like all energy booms before it, today’s natural gas rush brings jobs and money to small towns but can also spark social upheaval and leave communities with a legacy of pollution.

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We are exploiting new fossil fuel sources

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As sources of conventional fossil fuels decline and as prices rise, we will turn increasingly to newer alternatives. These include at least three further sources of fossil fuels that exist in large amounts: oil sands, oil shale, and methane hydrate. The oil sands of Alberta—and those in Venezuela, which likely hold even more oil—are already significantly increasing the amount of oil available to our society. Oil from shale is not yet economical to extract. Gas from methane hydrate is only now becoming technically feasible to extract. The world’s known deposits of oil shale may contain as much as 3 trillion barrels of oil (more than all the conventional crude oil in the world), but most of this will not easily be extracted. About 40% of global oil shale reserves are in the United States, mostly on federally owned land in Colorado, Wyoming, and Utah. Shale oil is costly to extract, and its EROI is very low, with the best estimates ranging from just 1.1:1 to 4:1. Historically, low prices for crude oil have kept investors away from shale oil, but every time crude oil prices rise, shale oil again attracts attention. As for methane hydrate, scientists believe there are immense amounts of this substance on Earth, holding perhaps twice as much carbon as all known deposits of oil, coal, and natural gas combined. Japan recently showed that it could extract methane hydrate from the seafloor by sending down a pipe and lowering pressure within it so that the methane turned to gas and rose to the surface. However, we do not yet know whether such extraction is safe and reliable. Destabilizing a methane hydrate deposit on the seafloor during extraction could lead to a catastrophic release of gas. This could cause a massive landslide and tsunami and would release huge amounts of methane, a potent greenhouse gas, into the atmosphere, worsening global climate change. Oil sands, oil shale, and methane hydrate are abundant, but they are no panacea for our energy challenges. For one thing, their net energy values are low, because they are expensive to extract and process. Thus, their EROI ratios are low. Moreover, these fuels exert severe environmental impacts. We will now turn to some of the impacts of our fossil fuel use— environmental, economic, social, and political—and examine potential solutions to these impacts.

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Addressing Impacts of Fossil Fuel Use Our society’s love affair with fossil fuels and the many petrochemical products we develop from them has helped to ease constraints on travel, lengthen our life spans, and boost our material standard of living beyond what our ancestors could have dreamed. However, it also causes harm to the environment and human health, and can lead to political and economic instability. Concern over these impacts is a prime reason many scientists, environmental advocates, businesspeople, and policymakers are increasingly looking toward clean and renewable sources of energy.

Fossil fuel emissions pollute air and drive climate change When we burn fossil fuels, we alter fluxes in Earth’s carbon cycle (pp. 139–141). We essentially take carbon that has been retired into a long-term reservoir underground and release it into the air. This occurs as carbon from the hydrocarbon molecules of fossil fuels unites with oxygen from the atmosphere during combustion, producing carbon dioxide (CO2). Carbon dioxide is a greenhouse gas (p. 502), and CO2 released from fossil fuel combustion warms our planet and drives changes in global climate (Chapter 18). Because global climate change is beginning to have diverse, severe, and widespread ecological and socioeconomic impacts, carbon dioxide pollution (FIGURE 19.15) is becoming recognized as the greatest environmental impact of fossil fuel use. Moreover, methane is a potent greenhouse gas that drives climate warming. Switching to new fossil fuel sources may 10 Billion metric tons of carbon/year

putting a hold on further approvals until new safety measures could be devised. In 2011, after weighing economic and environmental concerns, the administration issued a five-year plan that opened access to 75% of technically recoverable offshore oil and gas reserves while banning drilling offshore from states that did not want it. Drilling leases were expanded off Alaska and in the Gulf of Mexico, but areas along the East and West Coasts were not opened to drilling. The risks from expansion into Arctic waters were highlighted in 2012–2013, when Royal Dutch Shell’s Kulluk drilling rig ran aground while being towed south from Alaska during a winter storm. Damage to the rig and examination by public officials and the media raised fresh questions as to whether Arctic Ocean drilling can be conducted safely.

9 Total Coal Oil Natural gas

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FIGURE 19.15 Emissions from fossil fuel combustion have risen dramatically as nations have industrialized and as population and consumption have grown. Here, global emissions of carbon from carbon dioxide are subdivided by source (oil, coal, or natural gas). Data from Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, TN.

By what percentage have carbon emissions risen since the year your mother or father was born?

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Clean coal technologies aim to reduce air pollution from coal Burning coal emits a variety of pollutants unless effective pollution control measures are in place. The composition of emissions from coal combustion depends on chemical impurities in the coal, and coal deposits vary in the impurities they contain, including sulfur, mercury, arsenic, and other trace metals. Coal from the eastern United States tends to be high in sulfur because it was formed in marine sediments, and sulfur is present in seawater. Most coal in China is even more sulfur-rich. At coal-fired power plants, scientists and engineers are seeking ways to cleanse coal of sulfur, mercury, and other impurities. Clean coal technologies refer to an array of techniques, equipment, and approaches that aim to remove chemical contaminants during the process of generating electricity from coal. Among these technologies are various types of scrubbers, devices that chemically convert or physically remove pollutants (see Figure 17.16, p. 479). Some scrubbers use minerals such as magnesium, sodium, or calcium in reactions to remove sulfur dioxide (SO2) from smokestack emissions. Others use chemical reactions to strip away nitrogen oxides (NOX), breaking them down into elemental nitrogen and water. Multilayered filtering devices are used to capture tiny ash particles. Another clean coal approach is to dry coal that has high water content in order to make it cleaner-burning. We can

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also gain more power from coal with less pollution through a process called gasification, in which coal is converted into a cleaner synthesis gas, or syngas, by reacting it with oxygen and steam at a high temperature. In an “integrated gasification combined cycle” process, syngas from coal is used to turn a gas turbine and also to heat water to turn a steam turbine. The U.S. government and the coal industry have each invested billions of dollars in clean coal technologies for new power plants, and these have helped to reduce air pollution from sulfates, nitrogen oxides, mercury, and particulate matter (pp. 476–477). If these technologies were applied to the many older plants that still pollute our air, they could help even more. At the same time, the coal industry spends a great deal of money fighting regulations and mandates on its practices. As a result, many power plants are built with few clean coal technologies, and these plants will continue polluting our air for decades. Moreover, many energy analysts emphasize that these technologies may make for “cleaner” coal but will never result in energy production that is completely clean. Some argue that coal is an inherently dirty way of generating power and should be replaced outright with cleaner energy sources.

Can we capture and store carbon? Even if clean coal technologies were able to remove every last chemical contaminant from power plant emissions, coal combustion would still pump huge amounts of carbon dioxide (CO2) into the air, intensifying the greenhouse effect and worsening global climate change. This is why many current efforts focus on carbon capture followed by carbon storage or carbon sequestration (p. 526). This approach consists of capturing carbon dioxide emissions, converting the gas to a liquid form, and then sequestering (storing) it in the ocean or underground in a geologically stable rock formation (FIGURE 19.16). Carbon capture and storage (abbreviated as CCS) is being attempted at a variety of new and retrofitted facilities. The world’s first coal-fired power plant to approach zero emissions opened in 2008 in Germany. This Swedish-built plant removes its sulfate pollutants and captures its carbon dioxide, then compresses the CO2 into liquid form, trucks it 160 km (100 mi) away, and injects it 900 m (3000 ft) underground into a depleted natural gas field. In North Dakota, the Great Plains Synfuels Plant gasifies its coal, then sends half the CO2 through a pipeline into Canada, where a Canadian oil company buys the gas to inject into an oilfield to help it pump out the remaining oil. The North Dakota plant also captures, isolates, and sells seven other types of gases for various purposes. Currently the U.S. Department of Energy is teaming up with seven energy companies to build a prototype of a near-zero-emissions coal-fired power plant. The $1.3-billion FutureGen project aims to design, construct, and operate a power plant that burns coal, produces electricity, captures 90% of its carbon dioxide emissions, and sequesters the CO2 underground. The project, located in Meredosia, Illinois, will pump CO2 more than 1200 m (three-quarters of a mile) underground beneath layers of impermeable rock. If this showcase project succeeds, it could be a model for a new generation of power plants across the world.

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only make emissions worse; oil sands are estimated to generate 14–20% more greenhouse gas emissions than conventional oil, and shale oil is still more polluting. Besides modifying our climate, fossil fuel emissions affect human health. Combusting coal high in mercury content emits mercury that can bioaccumulate in organisms’ tissues, poisoning animals as it moves up food chains (pp. 391–392) and presenting health risks to people. Gasoline combustion in automobiles releases pollutants that irritate the nose, throat, and lungs. Some hydrocarbons, such as benzene and toluene, cause cancer in laboratory animals and likely in people. Gases such as hydrogen sulfide can evaporate from crude oil, irritate the eyes and throat, and cause asphyxiation. Crude oil also often contains trace amounts of known poisons such as lead and arsenic. As a result, workers at drilling operations, refineries, and in other jobs that entail frequent exposure to oil or its products can develop serious health problems, including cancer. The combustion of oil in our vehicles and coal in our power plants releases sulfur dioxide and nitrogen oxides, which contribute to industrial and photochemical smog (pp. 482–483) and to acid deposition (pp. 491–493). Fossil fuel pollution is intensifying in developing nations that are industrializing rapidly as they grow in population. In contrast, air pollution from fossil fuel combustion has been reduced in developed nations in recent decades as a result of laws such as the U.S. Clean Air Act and government regulations to protect public health (Chapter 17). In these nations, public policy has encouraged industry to develop and install technologies that reduce pollution, such as catalytic converters that cleanse vehicle exhaust (see Figure 17.15, p. 478). Wider adoption of such technologies in the developing world would reduce pollution there considerably.

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FIGURE 19.16 Carbon capture and Power plant (emitting CO2) Refinery CO2

storage schemes propose to inject liquefied carbon dioxide emissions underground. The CO2 may be injected into depleted fossil fuel deposits, deep saline aquifers, or oil or gas deposits undergoing secondary extraction.

CO2 CO2

CO2

Deep saline aquifer Abandoned coal seam Depleted oil or gas reservoir

At this point, however, carbon capture and storage is too unproven to be the central focus of a clean energy strategy. We do not know whether we can ensure that carbon dioxide will stay underground once injected there or whether these attempts might trigger earthquakes. Injection might in some cases contaminate groundwater supplies, and injecting carbon dioxide into the ocean would further acidify its waters (pp. 444, 446–447, 519). Moreover, CCS is energy-intensive and decreases the EROI of coal, adding to its cost and the amount we consume. Finally, many renewable energy advocates fear that the CCS approach takes the burden off emitters and prolongs our dependence on fossil fuels rather than facilitating a shift to renewables.

WEIGHING THE ISSUES CLEAN COAL AND CARBON CAPTURE  Do you think we should be spending billions of dollars to try to find ways to burn coal cleanly and to sequester carbon emissions from fossil fuels? Or is our money better spent on developing new clean and renewable energy sources that don’t yet have enough infrastructure to produce power at the scale that coal can? What pros and cons do you see in each approach?

shut-off systems had failed, and BP engineers tried one solution after another to stop the flow of oil and gas, which continued for three months, spilling roughly 4.9 million barrels (206 million gallons) of oil. The crisis proved difficult to control because we had never had to deal with a spill so deep underwater. It revealed that offshore drilling presents serious risks of environmental impact that may be difficult to address, even with our best engineering. As the oil spread through the Gulf of Mexico and washed ashore, the region suffered a wide array of impacts (FIGURE 19.18). Of the countless animals killed, most conspicuous were birds, which cannot regulate their body temperature once their feathers become coated with oil. However, the underwater nature of the BP spill meant that unknown numbers of fish, shrimp, corals, FIGURE 19.17 The explosion on BP’s Deepwater Horizon drilling platform in 2010 unleashed the world’s biggest-ever accidental oil spill. Here vessels try to put out the blaze.

Oil spills pollute oceans and coasts

556

Of the many ways that our fossil fuel use pollutes water, what comes to mind most readily for people is the pollution that occurs when oil from tanker ships or drilling platforms fouls coastal waters and beaches. In 2010, BP’s Deepwater Horizon offshore drilling platform exploded and sank off the coast of Louisiana (FIGURE 19.17). Eleven workers were killed, and oil gushed out of a broken pipe on the ocean floor a mile beneath the surface at a rate of 62,000 barrels per day. Emergency

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(a) Brown pelican coated in oil

(b) Beach cleanup

FIGURE 19.18 Impacts of the Deepwater Horizon spill were numerous and severe. This brown pelican, coated in oil (a), was one of countless animals killed. For months, volunteers and workers paid by BP labored (b) to clean oil from the Gulf’s beaches.

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Fortunately, pollution from large spills has decreased greatly in recent decades (pp. 454–455), thanks to government regulations (such as requirements for double-hulled ships) and improved spill response efforts. And although large catastrophic oil spills have significant impacts on the marine environment, it is important to recognize that most water pollution from oil results from countless small non-point sources (pp. 426–427) to which all of our actions contribute (see Figure 16.17b, p. 454). Oil from automobiles, homes, industries, gas stations, and businesses runs off roadways and enters rivers and wastewater facilities, being discharged eventually into the ocean. Oil can also contaminate groundwater supplies when pipelines rupture or when underground storage tanks (p. 431) containing petroleum products leak. In addition, atmospheric deposition of pollutants from the combustion of fossil fuels exerts many impacts on freshwater ecosystems. Water pollution from industrial point sources has been greatly reduced in the United States following the Clean Water Act (Chapter 15), and many solutions exist to address non-pointsource pollution.

Hydrofracking poses new concerns Extracting oil or natural gas by hydraulic fracturing (in which chemicals are mixed with the pressurized water and sand that is injected deep underground) presents risks of water pollution that are not yet completely understood. One risk is that the chemicals (often called fracking fluids) may leak out of the drilling shafts and into aquifers that people use for drinking water. Another concern is that methane may contaminate groundwater used for drinking if it travels up the fractures or leaks through the shaft (see The Science behind the Story, Chapter 7, pp. 184–185). Fracking sites also create air pollution as methane and volatile toxic components of fracking fluids seep up from drilling locations. In fact, some of the unhealthiest air pollution in

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and other marine animals were also killed, affecting coastal and ocean ecosystems in complex ways. Plants in coastal marshes died, and the resulting erosion of marshes put New Orleans and other coastal cities at greater risk from storm surges and flooding. Gulf Coast fisheries, which supply much of the nation’s seafood, were hit hard by the spill, with thousands of fishermen and shrimpers put out of work. Beach tourism suffered, and indirect economic and social impacts were expected to last for years. Throughout this process, scientists have been studying aspects of the spill and its impact on the region’s people and natural systems (see THE SCIENCE BEHIND THE STORY, pp. 558–559). The Deepwater Horizon spill was the largest accidental oil spill in world history, far eclipsing the spill from the Exxon Valdez tanker in 1989. In that event, oil from Alaska’s North Slope, piped to the port of Valdez through the trans-Alaska pipeline, caused long-term damage to ecosystems and economies in Alaska’s Prince William Sound when the tanker ran aground. Two-and-a-half decades later, a layer of oil remains just inches beneath the sand of the region’s beaches. Today as climate change melts sea ice in the Arctic, opening new shipping lanes, nations are jockeying for position, hoping to stake claim to oil and gas deposits that lie beneath the seafloor. Offshore drilling in Arctic waters, however, poses severe pollution risks, because if a spill were to occur, icebergs, pack ice, storms, cold temperatures, and wintertime darkness would hamper response efforts, while frigid water temperatures would slow the natural breakdown of oil. In U.S. Arctic waters that are now open to oil and gas leasing, some sites are 1000 miles away from the nearest Coast Guard station. The Obama administration approved these leases despite admitting that infrastructure to respond to a major spill there does not exist. Natural Resources Defense Council president Frances Beinecke, a member of the commission Obama set up to draw lessons from the BP spill, called such Arctic leases a “reckless gamble” and lamented that neither the administration, Congress, nor industry had improved safety measures in any meaningful way since the BP spill.

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THE SCIENCE BEHIND THE STORY Discovering Impacts of the Gulf Oil Spill President Barack Obama echoed the perceptions of many Americans when he called the Deepwater Horizon oil spill “the worst environmental disaster America has ever faced.” But what has scientific research told us about the actual impacts of the Gulf oil spill? We don’t yet have all the answers, because the deep waters affected by the spill have been difficult for scientists to study. A great deal will remain unknown. Yet the intense and focused scientific response to the spill demonstrates the dynamic way in which science can assist society. As the spill took place, government agencies called on scientists to help determine how much oil was leaking. Researchers eventually determined the rate reached 62,000 barrels per day. Using underwater imaging, aerial surveys, and shipboard water samples, researchers tracked the movement of oil up through the water column and across the Gulf. These data helped predict when and where oil might reach

shore, thereby helping to direct prevention and cleanup efforts. Meanwhile, as engineers struggled to seal off the well using remotely operated submersibles, researchers helped government agencies assess the fate of the oil (FIGURE 1). This data would help inform studies of the oil’s impacts on marine life and human communities. Tracking movement of the oil underwater was challenging. University of Georgia biochemist Mandy Joye, who had studied natural seeps in the Gulf for years, documented that the leaking wellhead was creating a plume of oil the size of Manhattan. She also found evidence of low oxygen concentrations, or hypoxia (pp. 123, 428), because some bacteria consume oil and gas, depleting oxygen from the water and making it uninhabitable for fish and other creatures. Joye and other researchers feared that the thinly dispersed oil might prove devastating to plankton (the base of the marine food chain) and to the tiny larvae of shrimp, fish, and oysters (the pillars of the fishing industry). Scientists taking water samples documented sharp drops in plankton during the spill, but it will take several years to

FIGURE 1 Scientists helped track oil from the Deepwater Horizon spill. The map (a) shows areas polluted by oil. The pie chart (b) gives a breakdown of the oil’s fate. Source (a): National Geographic and NOAA; (b) NOAA. MISSISSIPPI Lake Pontchartrain

ALABAMA

GEORGIA Tallahassee

FLORIDA

Residual oil remains in the water, on shore, or in sediments.

LOUISIANA

New Orleans

Residual* 23%

*Oil in these 3 categories degrades naturally

Direct recovery from wellhead 17% Burned 5%

Macondo Well (site of Deepwater Horizon blowout)

Skimmed 3%

Oil on shoreline Oil on water surface Very light 1–10 days Light 10–30 days Medium More than 30 days Heavy

Evaporated or dissolved 23%

(a) Extent of the spill

(b) Fate of the oil

Chemically dispersed* 16% Naturally dispersed* 13%

A scientist rescues an oiled Kemp’s ridley sea turtle.

learn whether the impact on larvae will diminish populations of adult fish and shellfish. Studies on the condition of living fish in the region are now being published, some of which show gill damage, tail rot, lesions, and reproductive problems at much higher levels than is typical. What was happening to life on the seafloor was a mystery, because there are only a handful of submersible vehicles in the world able to travel to the crushing pressures of the deep sea. Luckily, a team of researchers led by Charles Fisher of Penn State University was scheduled to embark on a regular survey of deepwater coral across the Gulf of Mexico in late 2010. Using the three-person submersible Alvin and the robotic vehicles Jason and Sentry, the team found healthy coral communities at sites far away from the Macondo well but found dying corals and brittlestars covered in a brown material at a site 11 km from the Macondo well. Eager to determine whether this community was contaminated by the BP oil spill, the research team added chemist Helen White of Haverford College and returned a month later, thanks to a National Science Foundation program that funds rapid response research. On this trip, chemical analysis of the brown material showed it to match oil from the BP spill, rather than from any other known source. Other questions revolve around impacts of the chemical dispersant that BP used to break up the oil, a compound called Corexit 9500. Work by biologist Philippe Bodin following

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SHORELINES • Air and ground surveys • Habitat assessment • Measurements of subsurface oil

WATER COLUMN AND SEDIMENTS • Water quality surveys • Sediment sampling • Transect surveys to detect oil • Oil plume modeling

AQUATIC VEGETATION • Air and coastal surveys

HUMAN USE • Air and ground surveys

Wellhead

FISH, SHELLFISH, AND CORALS • Population monitoring of adults and larvae • Surveys of food supply (plankton and invertebrates) • Tissue collection and sediment sampling • Testing for contaminants

BIRDS, TURTLES, MARINE MAMMALS • Air, land, and boat surveys • Radiotelemetry, satellite tagging, and acoustic monitoring • Tissue sampling • Habitat assessment

FIGURE 2 Thousands of researchers continue to help assess damage to natural resources from the Deepwater Horizon oil spill. They are surveying habitats, collecting samples and testing them in the lab, tracking wildlife, monitoring populations, and more.

work. The government tested fish and shellfish for contamination and reopened fishing once they were found to be safe, but consumers balked at buying Gulf seafood. Beach tourism remained low all summer as visitors avoided the region. Together, losses in fishing and tourism totaled billions of dollars. Scientists expect some impacts from the Gulf spill to be long-lasting. Oil from the similar Ixtoc blowout off Mexico’s coast in 1979 still lies in sediments near dead coral reefs, and fishermen there say it took 15–20 years for catches to return to normal. After the Amoco Cadiz spill, it took seven years for oysters and other marine species to recover. In Alaska, oil from the Exxon Valdez spill remains embedded in beach sand today. However, many researchers are hopeful about the Gulf of Mexico’s recovery from the Deepwater Horizon

spill. The Gulf’s warm waters and sunny climate speed the natural breakdown of oil. In hot sunlight, volatile components of oil evaporate from the surface and degrade in the water, so that fewer toxic compounds such as benzene, naphthalene, and toluene reach marine life. In addition, bacteria that consume hydrocarbons thrive in the Gulf because some oil has always seeped naturally from the seafloor and because leakage from platforms, tankers, and pipelines is common. These microbes give the region a natural self-cleaning capacity. Researchers continue to conduct a wide range of scientific studies (FIGURE 2). A consortium of federal and state agencies is coordinating research and restoration efforts in the largest ever Natural Resource Damage Assessment, a process mandated under the Oil Pollution Act of 1990. Answers to questions will come in gradually as long-term impacts become clear.

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the Amoco Cadiz oil spill in France in 1978 had found that Corexit 9500 appeared more toxic to marine life than the oil itself. BP threw an unprecedented amount of the chemical at the Deepwater Horizon spill, injecting a great deal directly into the path of the oil at the wellhead. This caused the oil to dissociate into trillions of tiny droplets that dispersed across large regions. Many scientists worried that this expanded the oil’s reach, affecting more plankton, larvae, and fish. Impacts of the oil on birds, sea turtles, and marine mammals were easier to assess. Officially confirmed deaths numbered 6104 birds, 605 turtles, and 97 mammals—and hundreds more animals were cleaned and saved by wildlife rescue teams—but a much larger, unknown, number succumbed to the oil. What impacts this mortality may have on populations in coming years is unclear. (After the Exxon Valdez spill in Alaska in 1989, populations of some species rebounded, but populations of others have never come back.) Researchers are following the movements of marine animals in the Gulf with radio transmitters to try to learn what effects the oil may have had. As images of oil-coated marshes saturated the media, researchers worried that widespread death of marsh grass would leave the shoreline vulnerable to severe erosion by waves. Louisiana has already lost many coastal wetlands to subsidence, dredging, sea level rise, and silt capture by dams on the Mississippi River (pp. 407–408). Fortunately, researchers found that oil did not penetrate to the roots of most plants and that oiled grasses were sending up new growth. Indeed, Louisiana State University researcher Eugene Turner said that loss of marshland from the oil “pales in comparison” with marshland lost each year due to other factors. The ecological impacts of the spill had measurable impacts on people. The region’s mighty fisheries were shut down, forcing thousands of fishermen out of

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the United States was found to be far away from the nearest city, in a little-populated region of Wyoming home to extensive fracking operations. Many residents of areas near hydraulic fracturing sites have experienced polluted air and fouled drinking water (pp. 180–182), but more research is needed to assess the extent of such pollution and to quantify the health risks. Hydrofracking also produces immense volumes of wastewater. Injected water often returns to the surface laced with salts, radioactive elements such as radium, and toxic chemicals such as benzene that come from deep underground. This wastewater is often sent to sewage treatment plants that are not designed to handle all the contaminants and that do not regularly test for radioactivity. This has caused concern in Pennsylvania, where a boom in natural gas extraction from the vast Marcellus Shale deposit continues to send millions of gallons of drilling waste to treatment plants, which then release their water into rivers that supply drinking water for people in Pittsburgh, Harrisburg, and other cities.

FIGURE 19.19 In mountaintop removal mining for coal, entire mountain peaks are leveled and fill is dumped into adjacent valleys, as shown here over many square miles in West Virginia. This can cause erosion and acid drainage into waterways that flow into surrounding valleys, affecting ecosystems and people over large areas.

Coal mining devastates natural systems Oil sands development pollutes water

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Similar concerns are being voiced about the extraction and transport of oil from oil sands. People living along the route of the Keystone XL pipeline worry that if oil were to spill from a leak in the pipeline, it would sink into the area’s porous ground and quickly reach the region’s shallow water table, contaminating the Ogallala Aquifer. This aquifer (p. 411) provides 2 million Americans with drinking water and irrigates a large portion of U.S. agriculture. The pipeline was originally slated to cross the Sandhills region of Nebraska, an ecologically valuable area that hosts most of the world’s Sandhill cranes as well as other migratory birds. At the behest of government regulators, TransCanada agreed to move the proposed route eastward to skirt around the edge of the Sandhills region and the Ogallala Aquifer. Pipeline leaks are a legitimate concern, as oil from oil sands is more corrosive than conventional crude oil. Recent leaks along the Kalamazoo River in Michigan, in a residential neighborhood of Mayflower, Arkansas, and in other locations have caused severe contamination. In Alberta where the oil sands are mined, the process uses immense amounts of water, and the polluted wastewater that results is left to sit in gigantic reservoirs. The Syncrude company’s massive tailings pond near Fort McMurray, Alberta, is so large that it is held back by the world’s second-largest dam. Migratory waterfowl land on water bodies like this and are killed as the oily water gums up their feathers and impairs their ability to insulate themselves. These water pollution impacts come on top of the deforestation required to mine the fuels in the first place. Industry representatives counter that the area deforested so far amounts to just 0.1% of Canada’s vast boreal forest. They also point out they are mandated to attempt restoration afterwards. However, effective reclamation has not yet been demonstrated, and regions denuded by the very first oil sand mine in Alberta 30 years ago have still not recovered.

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The mining of coal exerts substantial impacts on natural systems and human well-being (pp. 657–658). Strip mining destroys large swaths of habitat and causes extensive soil erosion. It also can cause chemical runoff into waterways through the process of acid drainage (pp. 657–658). This occurs when sulfide minerals in newly exposed rock surfaces react with oxygen and rainwater to produce sulfuric acid. As the sulfuric acid runs off, it leaches metals from the rocks, many of which are toxic. Acid drainage is a natural phenomenon, but mining greatly accelerates the rate at which it occurs by exposing many new rock surfaces at once. Regulations in the United States require mining companies to restore strip-mined land following mining, but complete restoration is impossible, and ecological modifications are severe and long-lasting (pp. 661, 664). Most other nations exercise less oversight. Mountaintop removal mining (FIGURE 19.19 and pp. 659– 663) has impacts that exceed even conventional strip mining. When countless tons of rock and soil are removed from the top of a mountain, material slides downhill, where immense areas of habitat can be degraded or destroyed and creek beds can be clogged and polluted. Loosening of U.S. government regulations in 2002 enabled mining companies to legally dump mountaintop rock and soil into valleys and rivers below, regardless of the consequences for ecosystems, wildlife, and local residents.

Oil and gas extraction modify the environment To drill for conventional oil or gas on land, road networks must be constructed and many sites may be explored in the course of prospecting. The extensive infrastructure needed to support a full-scale drilling operation typically includes housing for workers, access roads, transport pipelines, and waste piles for removed soil. Ponds may be constructed to collect the toxic sludge that remains after the useful components of oil have been removed. These activities can pollute the soil, air, and water, fragment habitats, and disturb wildlife. All

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these impacts have been documented on the tundra of Alaska’s North Slope, where policymakers continue to debate whether to open the Arctic National Wildlife Refuge to drilling. Fortunately, drilling technology is more environmentally sensitive than in the past. Directional drilling allows drillers to bore down vertically and then curve to drill horizontally. This enables extraction companies to follow the course of horizontal layered deposits to extract the most they can from them. It allows drilling to reach a large underground area (up to several thousand meters in radius) around a drill pad. As a result, fewer drill pads are needed, and the surface footprint of drilling is smaller.

We all pay external costs

Fossil fuel extraction has mixed consequences for local people Across the world today, people living in fossil-fuel-bearing regions must weigh the environmental, health, and social drawbacks of fossil fuel development against the financial benefits that they and their families may gain. Communities where fossil fuel extraction is taking place generally experience a flush of high-paying jobs and economic activity, and for many people these economic benefits far outweigh other concerns. Perceptions may change with time, however. Economic booms often prove temporary, and residents may be left with the legacy of a polluted environment for generations to come. Fort McMurray is the hub of Alberta’s oil sands boom. Fort McMurray’s population has skyrocketed from 2000 in the 1960s to over 100,000 today as people have flocked here looking for jobs. Most residents are men, averaging 32 years of age, and the city boasts the highest birthrate in Canada. Salaries are high, but so are rents and home prices. A well-disciplined worker can become wealthy, but others fall behind, victims of drug abuse, alcoholism, or gambling. Like all boomtowns, Fort McMurray is outgrowing its infrastructure, and it is likely to experience a bust when the price of its principal resource falls. Along the route the oil would take out of Alberta, the Keystone XL pipeline extension would create 20,000 “jobyears,” TransCanada estimates—6500 construction jobs for two years plus 7000 one-year jobs for manufacturers of supplies. For landowners, the pipeline project has mixed consequences. TransCanada has had to negotiate with thousands of landowners along the Keystone XL route, offering them money for the right to

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Dependence on foreign energy affects the economies of nations Putting all your eggs in one basket is always a risky strategy. Because virtually all our modern technologies and

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The costs of alleviating the many health and environmental impacts of fossil fuel extraction and use are generally not internalized in the market prices of fossil fuels. Instead, we all pay these external costs (pp. 164, 183) through medical expenses, costs of environmental cleanup, and impacts on our quality of life. Moreover, the prices we pay at the gas pump or on our monthly utility bill do not even cover the financial costs of fossil fuel production. Rather, fossil fuel prices have been kept inexpensive as a result of government subsidies to extraction companies. The profitable and well-established fossil fuel industries still receive far more financial support from taxpayers than do the young and struggling renewable energy sources (Figure 7.14, p. 200; Figure 21.6, p. 603). Thus, we all pay extra for our fossil fuel energy through our taxes, generally without even realizing it.

install the pipeline across their land. Many were happy to accept payments, but landowners who declined TransCanada’s offers found their land rights taken away by eminent domain—the policy by which courts set aside private property rights to make way for projects judged to be for the public good. Following a 2005 U.S. Supreme Court ruling, even private companies can usurp land rights. The landowner is paid an amount determined by a court to be fair and cannot appeal the decision. As John Harter, a South Dakota rancher along the pipeline route, put it, “I found out that they have more rights to my property than I do. It makes me very angry when I paid for it . . . and take care of it.” In Alaska, to gain support for oil drilling among state residents, the oil industry pays the Alaskan government a portion of its revenues. Since the 1970s, the state of Alaska has received over $65 billion in oil revenues. Alaska’s state constitution requires that one-quarter of state oil revenues be placed in the Permanent Fund, which pays yearly dividends to all residents. Since 1982, each Alaska resident has received annual payouts ranging from $331 to $2069. Such distribution of revenue among citizens is unusual; in most parts of the world where fossil fuels are extracted, local residents suffer pollution without compensation. Even when multinational gas or oil corporations pay developing nations for access to extract oil or gas, the money generally does not trickle down from the government to the people who live where the extraction takes place. Moreover, oil-rich developing nations such as Ecuador, Venezuela, and Nigeria tend to have few environmental regulations, and governments may not enforce regulations if there is risk of losing the large sums of money associated with oil development. In Nigeria, the Shell Oil Company extracted $30 billion of oil from land of the native Ogoni people, yet the Ogoni still live in poverty, with no running water or electricity. Profits from the oil extraction went to Shell and to the military dictatorships of Nigeria. The development resulted in oil spills, noise, and constantly burning gas flares—all of which caused illness among people living nearby. Starting in 1962, Ogoni activist and leader Ken Saro-Wiwa worked for fair compensation to the Ogoni. After years of persecution by the Nigerian government, SaroWiwa was arrested in 1994, given a trial universally regarded as a sham, and put to death by military tribunal. Wherever in the world fossil fuel extraction comes to communities, people seem to find themselves divided over whether the short-term economic benefits are worth the longterm health and environmental impacts. Today this debate is occurring in North Dakota and parts of the West in response to oil and gas drilling, and in Pennsylvania, New York, and other states above the Marcellus Shale where the petroleum industry is hydrofracking for gas (Chapter 7). The debate has gone on for years in Appalachia over mountaintop removal mining. There are no easy answers, but impacts would be lessened if extraction industries were to put more health and environmental safeguards in place for workers and residents.

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140 Production Consumption

15

10

5

0

i y n an ed ud an Ira nit tes Sa bia Jap rm U e a a G St Ar FIGURE 19.20 Japan, Germany, and the United States are among nations that consume far more oil than they produce. Iran and Saudi Arabia produce more oil than they consume and are able to export oil to high-consumption countries. Data from BP p.l.c., 2012. Statistical review of world energy 2012.

For every barrel of oil produced in the United States, how many barrels are consumed in the United States?

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services depend in some way on fossil fuels, we are vulnerable to supplies becoming costly or unavailable. Nations that lack adequate fossil fuel reserves of their own are especially vulnerable. For instance, Germany, France, South Korea, and Japan consume far more energy than they produce and thus rely almost entirely on imports (FIGURE 19.20). Since its 1970 oil production peak, the United States has relied more on foreign energy, and today imports nearly half of its oil. Such reliance means that seller nations can control energy prices, forcing buyer nations to pay more as supplies dwindle. This became clear in 1973, when the Organization of Petroleum Exporting Countries (OPEC) resolved to stop selling oil to the United States. The predominantly Arab nations of OPEC opposed U.S. support of Israel in the Arab–Israeli Yom Kippur War and sought to raise prices by restricting supply. The embargo created panic in the West and caused oil prices to skyrocket (FIGURE 19.21), spurring inflation. Fear of oil shortages drove American consumers to wait in long lines at gas pumps. A similar supply shock followed in 1979 in response to the Iranian revolution. With the majority of world oil reserves located in the politically volatile Middle East, crises in this region are a constant concern for U.S. policymakers. The democratic street uprisings of the “Arab Spring” that began in 2011 in Tunisia and Egypt and spread elsewhere in the region put leaders of the United States and other Western nations in an awkward position, because they had long supported many of the region’s autocratic rulers. These rulers had facilitated Western access to oil, even as they suppressed democracy in their own societies. The Arab Spring uprisings were only the most recent in a long history of events that have affected oil prices and global access to oil, stretching back through the U.S.–led wars in Iraq and the Iran–Iraq war of the 1980s to the 1973 OPEC embargo. From this perspective, turning to Canada’s oil sands as a primary source of oil represents a perfect solution for the United States. Canada is a stable, friendly, democratic neighboring country that is already the United States’ biggest

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Dollar value of the day Dollar value in 2012

130 Crude oil prices (U.S. dollars per barrel)

Million barrels of oil per day

20

120

Arab Spring

Iranian revolution

110 100

Hurricanes Katrina & Rita

90 OPEC oil embargo

80 70

Gulf U.S. War invades Iraq

60 50 40 30 20

Recession

10 0 1950

1960

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1980 Year

1990

2000

2010

FIGURE 19.21 World oil prices have gyrated over the decades. Often this has resulted from political and economic events in oilproducing countries, particularly in the Middle East. Data from U.S. Energy Information Administration and BP p.l.c., 2012, Statistical review of world energy 2012.

trading partner. Trading with Canada for petroleum from the oil sands would lessen U.S. reliance on Middle Eastern oil, and this is a major reason that many American policymakers and citizens favor building the Keystone XL pipeline. Indeed, in recent years the United States has already diversified its sources of imported petroleum considerably and now receives most from non–Middle Eastern nations, including Canada, Mexico, Venezuela, and Nigeria (FIGURE 19.22). Diversifying sources of foreign oil was one way in which the U.S. government responded to the 1973 embargo. The United States also enacted conservation measures, capped the price that domestic producers could charge for oil, funded research into renewable energy sources, and urged oil companies to pursue secondary extraction at old wells. It established an emergency

Other non-OPEC nations 20.2%

Other OPEC nations

Canada 23.8%

9.8%

Mexico 10.6%

4.0% 5.5%

Iraq

10.5% 7.2%

8.3%

Russia Nigeria

Venezuela

Saudi Arabia OPEC nations Non-OPEC nations

FIGURE 19.22 The United States now imports most oil from non-OPEC nations and from non-Middle-Eastern nations. Data from U.S. Energy Information Administration, 2012. Annual energy review 2011.

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stockpile (which today stores one month of oil) deep underground in salt caverns in Louisiana, called the Strategic Petroleum Reserve. And it called for developing additional domestic sources, including offshore oil from the Gulf of Mexico. Since then, the desire to reduce reliance on foreign oil by boosting domestic production has driven the expansion of offshore drilling into deeper and deeper water. It has repeatedly driven a proposal to open the Arctic National Wildlife Refuge on Alaska’s North Slope to oil extraction, despite critics’ charges that drilling there would spoil America’s last true wilderness while adding little to the nation’s oil supply. Today it is driving the push to drill for oil offshore in the waters of the Arctic, despite the environmental risks. As domestic U.S. production of oil and gas increase due to enhanced drilling

WEIGHING THE ISSUES DRILL, BABY, DRILL?  Do you think the United States should open more of its offshore waters to oil and gas extraction? Would the benefits exceed the potential costs? What factors should the government consider when deciding which areas to lease for drilling? How strongly should government regulate oil and gas extraction once drilling begins? Give reasons for your answers.

How will we convert to renewable energy? Fossil fuels are limited in supply, and their use has health, environmental, political, and socioeconomic consequences (FIGURE 19.23). For these reasons, many scientists, environmental advocates, businesspeople, and policymakers have concluded that fossil fuels are not a sustainable long-term solution to our energy needs. They further conclude that we need to shift to clean and renewable sources of energy that exert less impact on natural systems and human health. Many nations are moving far faster than the United States. France relies on nuclear power for its energy needs, Germany is investing in solar power (pp. 599–600), and China is forging ahead and developing multiple renewable energy technologies. As we make the transition to renewable energy sources, it will benefit us to extend the availability of fossil fuels. We can prolong our access to fossil fuels by instituting measures to

Consequences

Low prices

Government subsidies

Pollution of air, water, soil

Reliance on fossil fuels

Extraction impacts

Failure to develop other energy sources Depletion of fossil fuels

More uses (plastics, etc.)

Human population growth

Growth in per capita consumption

Degradation of ecosystems

Economic and political vulnerability

Attempt to shift quickly to renewable energy sources Limited nonrenewable supplies

Poor fuel efficiency in autos

FIGURE 19.23 Our reliance on and depletion of fossil fuels have many causes (ovals on left) and consequences (boxes on right). Arrows in this concept map lead from causes to consequences. Note that items grouped within outlined boxes do not necessarily share any special relationship; the outlined boxes are merely intended to streamline the figure.

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Global climate change

Greenhouse gas emissions

More powerful extraction technologies

if this fails, then...

End to globalization; societies become localized

Economic loss Economic depression

Health impacts Social disruption

Solutions As you progress through this chapter, try to identify as many solutions to our reliance on and depletion of fossil fuels as you can. What could you personally do to help address this issue? Consider how each action or solution might affect items in the concept map above.

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Causes

efforts, the United States becomes freer to make geopolitical decisions without being hamstrung by dependence on foreign energy imports. As pressure for increased drilling intensifies in coming years, our society will be debating the complex mix of social, political, economic, and environmental costs and benefits.

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conserve energy through lifestyle changes that reduce energy use, and through technological advances that improve efficiency.

Energy Efficiency and Conservation Until our society makes the transition to renewable energy sources, we will need to find ways to minimize and extend the use of our precious fossil fuel resources. Energy efficiency describes the ability to obtain a given result or amount of output while using less energy input. Energy conservation describes the practice of reducing wasteful or unnecessary energy use. In general, efficiency results from technological improvements, whereas conservation stems from behavioral choices. Because greater efficiency allows us to reduce energy use, efficiency is one primary means of conservation. Efficiency and conservation allow us to be less wasteful and to reduce our environmental impact. Moreover, by enabling us to extend the lifetimes of our nonrenewable energy supplies, efficiency and conservation help to alleviate many of the difficult individual choices and divisive societal debates related to fossil fuels, from oil sands development and the Keystone XL pipeline to Arctic drilling to hydraulic fracturing. The United States burns through twice as much energy per dollar of Gross Domestic Product (GDP) as do most other industrialized nations. However, there is good news: Per-person energy consumption has declined slightly in the United States over the past four decades. During this time the United States has reduced its energy use per dollar of GDP by about 50% (FIGURE 19.24). Americans have achieved tremendous gains in efficiency already, and should be able to make still-greater progress in the future.

Personal choice and efficient technologies are two routes to conservation As individuals, we can make conscious choices to reduce our own energy consumption by driving less, turning off lights when rooms are not being used, dialing down thermostats, and

Energy consumed (1000 BTU) per dollar of GDP

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FIGURE 19.24 The United States has been producing more

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economic output per energy input. This graph shows how energy consumption per inflation-adjusted dollar of GDP has fallen. Data from U.S. Energy Information Administration, 2012. Annual energy review 2011.

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FIGURE 19.25 A thermogram reveals heat loss from buildings by recording energy in the infrared portion of the electromagnetic spectrum (p. 49). In this image, one house is uninsulated; its red color signifies warm temperatures where heat is escaping, whereas green shades signify cool temperatures where heat is being conserved. Also note that in all houses, more heat is escaping from windows than from walls.

cutting back on the use of energy-intensive machines and appliances. Many European nations use far less energy per capita than the United States yet enjoy equivalent standards of living. This indicates that Americans could reduce their energy consumption considerably without diminishing their quality of life. Moreover, for any given individual or business, reducing energy consumption saves money while helping to conserve resources. As a society, we can conserve energy by developing technologies and strategies to make our energy-consuming devices and processes more efficient. Currently, more than two-thirds of the fossil fuel energy we use is simply lost, as waste heat, in automobiles and power plants (see Figure 19.3). We can improve the efficiency of our power plants through cogeneration, in which excess heat produced during the generation of electricity is captured and used to heat nearby workplaces and homes and to produce other kinds of power. Cogeneration can almost double the efficiency of a power plant. The same is true of coal gasification and combined cycle generation (p. 555). In this process, coal is treated to create hot gases that turn a gas turbine, while the hot exhaust of this turbine heats water to drive a conventional steam turbine. In homes, offices, and public buildings, a significant amount of heat is needlessly lost in winter and gained in summer because of poor design and inadequate insulation (FIGURE 19.25). Improvements in design can reduce the energy required to heat and cool buildings. Such improvements may involve passive solar design (p. 606), better insulation, a building’s location, the vegetation around it, and even the color of its roof (lighter colors keep buildings cooler by reflecting the sun’s rays). Many consumer products, from lightbulbs to appliances, have been reengineered through the years to enhance efficiency. Energy-efficient lighting, for example, can reduce energy use by 80%. Compact fluorescent bulbs are much more efficient than incandescent light bulbs, and many governments are phasing out incandescent bulbs for this reason; the U.S. phaseout is scheduled to be complete in 2014.

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FIGURE 19.26 Hybrid cars have high fuel efficiencies. The Toyota Prius diagrammed here uses a small, clean, and efficient gasoline-powered engine 1 to produce power that the generator 2 can convert to electricity to drive the electric motor 3 . The power split device 4 integrates the engine, generator, and motor, serving as a continuously variable transmission. The car automatically switches among all-electrical power, all-gas power, and a mix of the two, depending on the demands being placed on the engine. Typically, the motor provides power for low-speed city driving and adds extra power on hills. The motor and generator charge a pack of nickel-metal-hydride batteries 5 , which can in turn supply power to the motor. Energy for the engine comes from gasoline carried in a typical fuel tank 6 .

1 Gasolinepowered engine

2 Generator 4 Power split device

5 Batteries

Automobile fuel efficiency is a key to conservation Among the measures enacted by the U.S. government in response to the OPEC embargo of 1973–1974 were a mandated increase in the mile-per-gallon (mpg) fuel efficiency of automobiles and a reduction in the national speed limit to 55 miles per hour. These measures notably reduced U.S. dependence on Middle Eastern oil and held down greenhouse gas emissions. Over the next three decades, however, many of the conservation initiatives of this time were abandoned. Without high market prices and an immediate threat of shortages, people lacked economic motivation to conserve. Government funding for research into alternative energy

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6 Fuel tank

sources dwindled, speed limits rose, and U.S. policymakers repeatedly failed to raise the corporate average fuel efficiency (CAFE) standards, which set benchmarks for auto manufacturers to meet. The average fuel efficiency of new vehicles fell from 22.0 mpg in 1987 to 19.3 mpg in 2004, as sales of sport-utility vehicles increased relative to sales of cars. Since then, fuel economy climbed to 22.8 mpg in 2011 (FIGURE 19.27) after Congress passed legislation in 2007 mandating that automakers raise average fuel efficiency to 35 mpg by the year 2020. This was a substantial advance, yet even after this boost, American automobiles would still have lagged well behind the efficiency of the vehicles of most other developed nations. As a result, when automakers required a government bailout during the recent recession, President Obama negotiated with them, forcing a series of agreements that ended with automakers agreeing to boost average fuel economies to

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FIGURE 19.27 Automotive fuel efficiencies have responded to public policy. Fuel efficiency for automobiles in the United States rose dramatically in the late 1970s as a result of legislative mandates but then stagnated once no further laws were enacted to improve fuel economy. Recent legislation is now improving it again. Data from U.S. Environmental Protection Agency, 2012. Light-duty automotive technology, carbon dioxide emissions, and fuel economy trends: 1975 through 2011.

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Federal standards for energy-efficient appliances have already reduced per-person home electricity use below what it was in the 1970s. The Energy Star program (p. 525) labels refrigerators, dishwashers, and other appliances for their energy efficiency, enabling consumers to take energy use into account when shopping for these items. For the consumer, studies show that the slightly higher cost of buying energy-efficient washing machines is rapidly offset by savings on water and electricity bills. The U.S. Environmental Protection Agency (EPA) estimates that if all U.S. households purchased energy-efficient appliances, the national annual energy expenditure would be reduced by $200 billion. Automotive technology represents perhaps our best opportunity to conserve large amounts of fossil fuels fairly easily. We can accomplish this with alternative-technology vehicles such as electric cars, electric/gasoline hybrids (FIGURE 19.26), or vehicles that use hydrogen fuel cells (pp. 620–622). Among electric/gasoline hybrids, current U.S. models of the Toyota Prius and the Chevrolet Volt average fuel-economy ratings of 50 miles per gallon (mpg) and 60 mpg, respectively—two to three times better than the average American car. Even without alternative vehicles, we already possess the means to enhance fuel efficiency for gasoline-powered vehicles by using lightweight materials, continuously variable transmissions, and more efficient gasoline engines.

Average fuel efficiency (miles per gallon)

3 Electric motor

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54.5 mpg by 2025. If this strong improvement comes to pass, it will enable a huge reduction in oil use. New technologies will add over $2000 to the average price of a car, but drivers will save perhaps $6000 in fuel costs over the car’s lifetime. In 2009, Congress and the Obama administration took another major step to improve automobile fuel efficiency while stimulating economic activity and saving jobs during a severe recession. The popular “Cash for Clunkers” program—formally named the Consumer Assistance to Recycle and Save (CARS) Act—paid Americans $3500 or $4500 each to turn in old vehicles and purchase newer, more fuel-efficient ones. The $3-billion program subsidized the sale or lease of 678,000 vehicles averaging 24.9 mpg that replaced vehicles averaging 15.8 mpg. It is estimated that 824 million gallons of gasoline will be saved as a result, preventing 9 million metric tons of greenhouse gas emissions and creating social benefits worth $278 million. U.S. policymakers could do still more to encourage oil conservation. So far the United States has kept its taxes on gasoline extremely low, relative to most other nations. Americans pay two to three times less per gallon of gas than drivers in many European countries. In fact, gasoline in the United States is sold more cheaply than bottled water! As a result, U.S. gasoline prices do not account for the substantial external costs (pp. 164, 183) that oil production and consumption impose on society. Some experts have estimated that if all costs to society were taken into account, the price of gasoline would exceed $13/gallon. Instead, our artificially low gas prices diminish our economic incentives to conserve.

WEIGHING THE ISSUES MORE MILES, LESS GAS If you drive an automobile, what gas mileage does it get? How does it compare to the vehicle averages in Figure 19.27? If your vehicle’s fuel efficiency were 10 mpg greater, and if you drove the same amount, how many gallons of gasoline would you no longer need to purchase each year? How much money would you save? Do you think the U.S. government should mandate further increases in the CAFE standards? Should the government raise taxes on gasoline sales as an incentive for consumers to conserve energy? What effects (on economics, on health, and on environmental quality, for instance) might each of these steps have?

The rebound effect cuts into efficiency gains Energy efficiency is a vital pursuit, but it may not always save as much energy as we expect. This is because gains in efficiency from better technology can be partly offset if people engage in more energy-consuming behavior as a result. For instance, a person who buys a fuel-efficient car may choose to

drive more because he or she feels it’s okay to do so now that less gas is being used per mile. This phenomenon is called the rebound effect, and studies indicate that it is widespread and significant. In some instances, the rebound effect may completely erase efficiency gains, and attempts at energy efficiency may end up actually causing greater energy consumption! As our society pursues energy efficiency in more and more ways, this will be an important factor to consider.

We need both conservation and renewable energy Despite concerns over the rebound effect, energy efficiency and conservation efforts are vital to creating a sustainable future for our society. It is often said that reducing our energy use is equivalent to finding a new oil reserve. Some estimates hold that effective energy conservation and efficiency in the United States could save 6 million barrels of oil a day—nearly the amount gained from all offshore drilling, and considerably more than would be gained from Canada’s oil sands. In fact, conserving energy is better than finding a new reserve because it alleviates health and environmental impacts while at the same time extending our future access to fossil fuels. Yet regardless of how effectively we conserve, we will still need energy to power our civilization, and it will need to come from somewhere. Most energy experts feel that the only sustainable way of guaranteeing ourselves a reliable long-term supply of energy is to ensure sufficiently rapid development of renewable energy sources (Chapters 20 and 21).

Conclusion Over the past two centuries, fossil fuels have helped us build the complex industrialized societies we enjoy today. Yet sometime soon our production of conventional fossil fuels will begin to decline. We can respond to this challenge by seeking out new sources of fossil fuels and continuing our way of life but paying ever-higher economic, health, and environmental costs. Or, we can encourage conservation and efficiency while aggressively developing alternative clean and renewable energy sources. The path we choose will have far-reaching consequences for human health and well-being, for Earth’s climate, and for the stability and progress of our civilization. The debate over the Canadian oil sands and the Keystone XL pipeline is a microcosm of this debate over our energy future. Fortunately, we are not caught in a simple trade-off between fossil fuels’ economic benefits and their impacts on the environment, climate, and health. Instead, as renewable energy sources become increasingly feasible and economical, it becomes easier to envision freeing ourselves from a reliance on fossil fuels and charting a bright future for humanity and the planet with renewable energy.

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Reviewing Objectives You should now be able to: Identify the energy sources we use

• Many renewable and nonrenewable energy sources are available to us. (pp. 538–539) • Since the industrial revolution, nonrenewable fossil fuels— including coal, natural gas, and oil—have become our primary sources of energy. (p. 539)

• Coal is used today principally to generate electricity. (pp. 546–547) • Natural gas is cleaner-burning than coal or oil. (pp. 546–547) • Oil powers transportation and also is used to create a diversity of petroleum-based products that are everywhere in our daily lives. (pp. 547, 550) Evaluate peak oil and the challenges it may pose

• Energy sources and energy consumption are each unevenly distributed across the world. (pp. 540–541)

• R/P ratios help indicate how long a resource may last, but they tell only part of the story. (pp. 549–550)

• The concepts of net energy and EROI allow us to compare the amount of energy obtained from a source with the amount invested in its extraction and production. (pp. 540–542)

• Any nonrenewable resource can be depleted, and we have depleted nearly half the world’s conventional oil. (pp. 548–551)

• We face a choice in whether to pursue new low-quality fossil fuel sources such as oil sands or whether to develop alternative sources of clean renewable energy. (p. 542) Describe the origin and nature of major types of fossil fuels

• Coal, our most abundant fossil fuel, results from organic matter that undergoes compression but little decomposition. (pp. 543–544) • Crude oil is a thick, liquid mixture of hydrocarbons that is formed underground under high temperature and pressure. (p. 543) • Natural gas consists mostly of methane and can be formed in two ways. (p. 543) • Oil sands contain bitumen, a tarry substance formed from oil that was degraded by bacteria. This can be processed into synthetic crude oil. (p. 543) • Shale oil and methane hydrate are fossil fuel sources with potential for future use (p. 544) Explain how we extract and use fossil fuels

• Scientists locate fossil fuel deposits by analyzing subterranean geology. We then estimate the technically and economically recoverable portions of those reserves. (pp. 544–545, 548–549) • Coal is mined underground and strip-mined from the land surface, whereas we drill wells to pump out oil and gas. Oil sands may be strip-mined or dissolved underground and extracted through well shafts. (pp. 544–545) • Components of crude oil are separated in refineries to produce a wide variety of fuel types. (pp. 545–546)

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Examine how we are reaching further for fossil fuels

• Primary extraction may be followed by secondary extraction, in which gas or liquid is injected into the ground to help force up additional oil or gas. (p. 552) • Hydraulic fracturing is producing natural gas from shale deposits. (p. 553) • We are drilling for oil and gas further offshore, in deeper water, and are moving into the Arctic. (pp. 553–554) • New types of fossil fuels we may exploit include oil sands, shale oil, and methane hydrate (p. 554) Outline and assess environmental impacts of fossil fuel use, and explore solutions

• Emissions from fossil fuel combustion pollute air, pose human health risks, and drive global climate change. (pp. 554–555) • Public policy and advances in pollution control technology have reduced many of these emissions, but much more remains to be done. (p. 555) • Clean coal technologies aim to reduce pollution from coal combustion. (p. 555) • If we could safely and effectively capture carbon dioxide and sequester it underground, this would mitigate a primary drawback of fossil fuels. Carbon capture and storage remain unproven so far, however. (pp. 555–556) • Oil is a major contributor to water pollution. (pp. 556–557) • Hydrofracking poses pollution concerns. (pp. 557, 560) • Oil sands mining and transport cause deforestation, water pollution, and other impacts. (p. 560) • Coal mining can devastate ecosystems and pollute waterways. (p. 560)

C H A P T E R 1 9 • F O S S I L F U E L S , T H E I R I M P A C T S , A N D E N E R G Y C O N S E R VAT I O N

• Fossil fuels are formed very slowly as buried organic matter is chemically transformed by heat, pressure, and/or anaerobic decomposition. (pp. 542–543)

• Once we pass the peak of oil production, the gap between rising demand and falling supply may pose immense economic and social challenges for our society. (pp. 550–552)

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• Oil and gas extraction exert various impacts, but directional drilling has eased them. (pp. 560–561) Evaluate political, social, and economic aspects of fossil fuel use

• Fossil fuels impose external costs. (p. 561) • Fossil fuel extraction creates jobs but leaves pollution. People living in areas of fossil fuel extraction experience a range of consequences. (p. 561) • Today’s societies are so reliant on fossil fuel energy that sudden restrictions in oil supplies can have major economic consequences. (pp. 561–563) • Nations that consume far more fossil fuels than they produce are especially vulnerable to supply restrictions. (p. 562)

Specify strategies for conserving energy and enhancing efficiency

• Energy conservation involves both personal choices and efficient technologies. (p. 564) • Efficiency in power plant combustion, lighting, and consumer appliances, as well as changes in public policy, can help us conserve. (pp. 564–565) • Automotive fuel efficiency plays a key role in conserving energy. (pp. 565–566) • The rebound effect can partly negate our conservation efforts. (p. 566) • Conservation lengthens our access to fossil fuels and reduces environmental impact, but to build a sustainable society we will also need to shift to renewable energy sources. (p. 566)

Testing Your Comprehension 1. Why are fossil fuels our most prevalent source of energy

6. How do we create petroleum products? Provide examples

today? Why are they considered nonrenewable sources of energy? Describe how net energy differs from energy returned on investment (EROI). Why are these concepts important in the evaluation of energy sources? How are fossil fuels formed? How do environmental conditions determine which type of fossil fuel is formed in a given location? Why are fossil fuels often concentrated in localized deposits? How do geologists find oil and gas deposits and estimate amounts of oil or gas available? How do “technically recoverable” and “economically recoverable” amounts of a resource differ? Describe how coal is used to generate electricity.

of several of these products. 7. What is meant by peak oil? Why do many experts think we are about to pass the global production peak for conventional oil? What consequences could there be for our society? 8. Describe three environmental impacts of fossil fuel production and consumption. Compare contrasting views regarding the impacts of extracting oil from Alberta’s oil sands and shipping it by pipeline to the U.S. Gulf Coast. 9. Give an example of a clean coal technology. Now describe how carbon capture and storage is intended to work. 10. Describe one specific example of how technological advances can improve energy efficiency. Now describe one specific action you could take to conserve energy.

2.

3.

4.

5.

Seeking Solutions 1. Summarize the main arguments for and against the

3. Compare the health and environmental effects of coal

Keystone XL pipeline extension. What problems might it help solve? What problems might it create? Do you personally think Canada should continue to develop Alberta’s oil sands? Should the United States have approved construction of the Keystone XL pipeline extension? Give reasons for your answers.

extraction and consumption with those of oil and gas extraction and consumption. What steps could governments, industries, and individuals take to alleviate some of these impacts? 4. Contrast the experiences of the Ogoni people of Nigeria with those of the citizens of Alaska. How have they been similar and different? Do you think businesses or governments should take steps to ensure that local people benefit from oil drilling operations? How could they do so? 5. THINK IT THROUGH You have been elected governor of the state of Florida as the federal government is debating opening new waters to offshore drilling for oil and

2. What impacts might you expect on your lifestyle once our

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society arrives at peak oil? What lessons do you think we can take from the conservation methods adopted by the United States in response to the “energy crisis” of 1973–1974? What steps do you think we should take to avoid energy shortages in a post-peak-oil future?

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natural gas. Drilling in Florida waters would create jobs for Florida citizens as well as revenue for the state in the form of royalty payments from oil and gas companies. However, there is always the risk of a catastrophic oil spill, with its ecological, social, and economic impacts. Would you support or oppose offshore drilling off the Florida coastline? Why? What, if any, regulations would you insist be imposed on such development? What questions would you ask of scientists before making your decision? What factors would you consider in making your decision? 6. THINK IT THROUGH You are the mayor of a rural Nebraska town along the route of the proposed Keystone XL pipeline extension. Some of your town’s residents are eager to have jobs they believe the pipeline will

bring. Others are fearful that oil leaks from the pipeline could contaminate the water supply. Some of your town’s landowners are looking forward to receiving payments from TransCanada for use of their land, whereas others dread the prospect of noise, pollution, and trees being cut on their property. If the company receives too much local opposition it says it may move the pipeline route away from your town. What information would you seek from TransCanada, from your state regulators, and from scientists and engineers before deciding whether support for the pipeline is in the best interest of your town? How would you make your decision? How might you try to address the diverse preferences of your town’s residents?

Calculating Ecological Footprints

 

Hectares of land for fuel production

You

1703

Your class

 

Your state

 

United States

 

Assume that you are an average American who burns about 6.3 metric tons of oil-equivalent in fossil fuels each year and that average terrestrial net primary productivity (p. 129) can be expressed as 0.0037 metric tons/ha/year. Calculate how many hectares of land it would take to supply our fuel use by presentday photosynthetic production.

2. Earth’s total land area is approximately 15 billion

hectares. Compare this to the hectares of land for fuel production from the table. 3. In the absence of stored energy from fossil fuels, how large a human population could Earth support at the level of consumption of the average American, if all of Earth’s area were devoted to fuel production? Do you consider this realistic? Provide two reasons why or why not.

1. Compare the energy component of your ecological foot-

print calculated in this way with the 4.9 ha calculated using the method of the Global Footprint Network. Explain why results from the two methods may differ.

STUDENTS Go to MasteringEnvironmentalScience for assignments, the etext, and the Study Area with practice tests, videos, current events, and activities.

INSTRUCTORS Go to MasteringEnvironmentalScience for automatically graded activities, current events, videos, and reading questions that you can assign to your students, plus Instructor Resources.

C H A P T E R 1 9 • F O S S I L F U E L S , T H E I R I M P A C T S , A N D E N E R G Y C O N S E R VAT I O N

Scientists at the Global Footprint Network calculate the energy component of our ecological footprint by estimating the amount of ecologically productive land and sea required to absorb the carbon released from fossil fuel combustion. This translates into 4.9 ha of the average American’s 7.2-ha ecological footprint. Another way to think about our footprint, however, is to estimate how much land would be needed to grow biomass with an energy content equal to that of the fossil fuel we burn.

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20

Barsebäck nuclear power plant, Sweden

Conventional Energy Alternatives Upon completing this chapter, you will be able to: Discuss the reasons for seeking energy alternatives to fossil fuels Summarize the contributions to world energy supplies of conventional alternatives to fossil fuels Describe nuclear energy and how it is harnessed

Outline the societal debate over nuclear power Describe the major sources, scale, and impacts of bioenergy Describe the scale, methods, and impacts of hydroelectric power

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CEN T RA L C AS E S T U DY

Sweden’s Search for Alternative Energy SWEDEN RUSSIA EUROPE

Fukushima

“Nowhere has the public debate over nuclear power plants been more severely contested than ­Sweden.”

JAPAN

—Writer and analyst Michael Valenti

Chernobyl

UKRAINE

“If [Sweden] phases out nuclear power, then it will be virtually ­impossible for the country to keep its climate-change commitments.” —Yale University economist William Nordhaus

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But trying to phase out nuclear power proved difficult. Aware of the environmental impacts of fossil fuels, Sweden’s government and citizens did not want to increase their use of coal, oil, and gas. Sweden has been one of the few nations to decrease use of fossil fuels since the 1970s. But it did so largely by replacing them with nuclear power. As 2010 drew nearer, Sweden was still relying on 10 nuclear reactors for over 30% of its energy supply and over 40% of its electricity. If nuclear plants were to be shut down as planned, then the nation would need to boost its investment in alternative energy sources dramatically. Sweden, therefore, promoted research and ­development of renewable energy sources. Hydroelectric power was already supplying most of the rest of the nation’s electricity and could not be expanded much more. Instead, the government hoped that energy from biomass sources and wind power could fill the gap. Sweden boosted wind and b ­ ioenergy by applying a carbon tax (p. 531) to fossil fuels and by subsidizing renewable energy through a certificate program in which producers and users of fossil-fuel electricity were mandated to buy certificates from producers and users of renewable electricity. In these ways the government used market forces to make fossil fuels more expensive and renewable energy more affordable. Sweden soon made itself an international leader in renewable energy alternatives, and today gets nearly half its energy from renewable sources. Still, renewables were taking longer to develop than hoped, so policymakers repeatedly postponed the nuclear phaseout. Then in 2009, the government announced that it was reversing its policy and would not phase out nuclear power after all. Instead, new power plants would be built as existing ones needed replacing.

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Flashback to 1986: On the morning of April 28, workers at a nuclear power plant in Sweden detected unusually high radiation levels. The increased radioactivity was not coming from within the plant, but had spread through the atmosphere from the direction of the Soviet Union. They had discovered the outside world’s first evidence of the disaster at Chernobyl, more than 1200 km (750 mi) away in what is now the nation of Ukraine. Chernobyl’s nuclear reactor had exploded two days earlier, but the Soviet government had not yet admitted it. Fast-forward to 2011: On March 11, seismometers in Sweden and throughout the world recorded vibrations from the shaking of the massive Tohoku Earthquake off the coast of Japan. Soon thereafter, a tsunami inundated the Japanese coast, destroying entire towns, killing 20,000 people, and disabling nuclear reactors at the Fukushima Daiichi power plant. For the next several weeks, the world would stand on edge as Japanese authorities made frantic efforts to control the leakage of deadly radiation and avert further catastrophe. The events at both Chernobyl and Fukushima had broad and long-lasting repercussions. Each altered the course of the world’s use of nuclear energy, one of our main alternatives to fossil fuels. People in Ukraine and Japan will continue to struggle with the legacies of these events for years to come, but the global debate over nuclear power affects all of us. In Sweden in the days after Chernobyl, low levels of radioactive fallout rained down on the countryside, contaminating crops and cows’ milk. For many Swedes, this confirmed the decision they had made collectively six years earlier, in a 1980 referendum, to phase out their country’s nuclear power program, shutting down all nuclear plants by the year 2010.

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In announcing this decision, government leaders said it would be fiscally and socially irresponsible to dismantle the nation’s nuclear program without a ready replacement. Without an abundance of clean renewable power at hand, a nuclear phaseout would mean a return to fossil fuels, or else would require cutting down immense areas of forest to combust biomass. Policymakers also cited Sweden’s international obligations to hold down its carbon emissions under the Kyoto Protocol (p. 528). Nuclear power is free of atmospheric pollution and is an effective way to minimize greenhouse gas emissions. Then Fukushima occurred. As the drama played out in Japan, anti-nuclear protestors all over the world staged demonstrations. Many national governments reassessed their commitments to nuclear power, ran safety checks of existing plants, and halted plans for new plants. Germany responded most strongly. Just years before, the government of German Chancellor Angela Merkel—herself a physicist and a proponent of nuclear power—had postponed its own planned phaseout of nuclear power, much like Sweden had. But in the wake of Fukushima, hundreds of thousands of demonstrators took to the streets before state elections, and

Merkel’s government made a stunning U-turn. It reinstated the plan to phase out all nuclear plants by 2022 and immediately shut down its seven oldest plants. Sweden’s environment minister criticized Germany’s reaction, saying it would impede Germany’s ability to move away from fossil fuels. Meanwhile, the Swedish state–owned firm Vattenfall, a major contractor building German plants, sued the German government on the grounds that its phaseout, together with new taxes applied to the plants, breached its contract. The Swedish government’s shifting policies have reflected the tension in public sentiment between the benefits of fighting climate change by developing clean energy sources and the risk of supporting nuclear power while these new energy sources are being developed. Public opinion polls from 2003 onward showed substantial majorities of Swedish citizens in favor of maintaining or increasing their nation’s production of nuclear power. However, in 2012, a year after Fukushima, 44% of Swedes wanted to phase out nuclear power. Today, strong majorities of Swedish citizens continue to support boosting the development of renewable energy sources to keep their nation a world leader in the shift away from fossil fuels. New renewables (0.9%)

Alternatives to Fossil Fuels Fossil fuels helped to drive the industrial revolution and to create the unprecedented material prosperity we enjoy today. Our global economy is largely powered by fossil fuels; over 80% of our energy comes from oil, coal, and natural gas (FIGURE 20.1a). These three fuels also generate two-thirds of the world’s electricity (FIGURE 20.1b). However, these nonrenewable energy sources will not last forever. Easily extractable supplies of oil and natural gas are in decline, and we are expending more and more energy and

Hydropower (2.3%)

Oil (32.4%)

money to extract them (pp. 551–554). Moreover, use Nuclear the (5.7%) of coal, oil, and natural gas drives global climate change and entails many other health and environmental impacts (Chapters 17, 18, and 19). Bioenergy For these experts accept that we (10.0%) Coal reasons, most energy will need to shift from fossil fuels to energy sources that are (27.3%) less easily depleted andNatural gentler on our health and environgas ment. Developing alternatives to fossil fuels has the added (21.4%) benefit of helping to diversify an economy’s mix of energy, thus lessening price volatility and dependence on foreign fuel imports. (a) World energy production, by source

Bioenergy and new renewables (3.7%)

New renewables (0.9%) Hydropower (2.3%)

Oil (32.4%)

Coal (27.3%)

Nuclear (5.7%)

Nuclear (12.9%)

Bioenergy (10.0%) Natural gas (22.2%)

Natural gas (21.4%)

(a) World energy production, by source

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Oil (4.6%) Coal (40.6%)

Hydropower (16.0%)

(b) World electricity generation, by source

FIGURE 20.1 Fossil fuels dominate the global energy supply. Together, oil, coal, and natural gas account for 81%Bioenergy (a) of theand world’s energy production. Nuclear power and new renewables hydroelectric power contribute substantially to global electricity generation (b), but fossil fuels still power two(3.7%) thirds of our electricity. Data from International Energy Agency, 2012. Key world energy statistics 2012. Paris: IEA. Oil (4.6%) Coal (40.6%)

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We have developed a range of alternatives to fossil fuels (see Table 19.1, p. 539). Most of these energy sources are renewable, and most have less impact on health and the environment than oil, coal, or natural gas. At this time most remain more expensive than fossil fuels, at least in the short term and when external costs (pp. 164, 183) are not included in market prices. As technologies develop and as we invest in infrastructure to better transmit power from renewable sources, prices will come down further and help us transition toward these new energy sources.

Oil (36.5%)

Natural gas (27.3%)

New renewables (1.9%) Hydropower (2.8%) Nuclear (8.5%)

Bioenergy (4.5%)

Nuclear power, bioenergy, and hydropower are conventional alternatives

(a) U.S. energy consumption, by source Oil Coal Hydropower

40 Quadrillion BTU

Three alternative energy sources are currently the most developed and most widely used: nuclear power, hydroelectric power, and energy from biomass. Each of these well-established energy sources plays a substantial role in our energy and electricity budgets today. We can therefore call nuclear power, hydropower, and biomass energy (bioenergy) “conventional alternatives” to fossil fuels. Each of these three conventional energy alternatives are generally considered to exert less environmental impact than fossil fuels, but more impact than the “new renewable” alternatives (Chapter 21). Yet as we will see, they each involve a unique and complex mix of benefits and drawbacks. Nuclear power is commonly considered a nonrenewable energy source, and hydropower and bioenergy are generally described as renewable, but the reality is more complicated. Each of these energy sources is perhaps best viewed as an intermediate along a continuum of renewability.

Coal (18.3%)

Natural gas Nuclear power

Bioenergy

1980 Year

2000

30

20

10

0 1950

1960

1970

1990

2010

(b) U.S. energy consumption, 1949–2012

Fuelwood and other bioenergy sources provide 10% of the world’s energy, nuclear power provides about 6%, and hydropower provides about 2%. The less established renewable energy sources together account for less than 1% (see Figure 20.1a). Although their global contributions to our overall energy supply are minor, alternatives to fossil fuels do contribute greatly to our generation of electricity. Nuclear energy and hydropower together account for nearly 30% of the world’s electricity generation (see Figure 20.1b). Energy consumption patterns in the United States ­(FIGURE 20.2a) are similar to those globally, except that the United States relies less on fuelwood and slightly more on fossil fuels and nuclear power than most other countries. A graph showing trends in energy consumption in the United States over the past 60 years (FIGURE 20.2b) reveals two things. First, conventional alternatives play minor yet substantial roles in overall energy use. Second, use of conventional alternatives has been growing more slowly than use of fossil fuels. Sweden, however, has shown that it is possible for a wealthy and advanced economy to replace fossil fuels gradually with alternative sources while continuing to raise living standards for its citizens. Since 1970, Sweden has decreased its fossil fuel use from 81% to 38% of its national energy

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FIGURE 20.2 Fossil fuels predominate in the United States. Together, oil, natural gas, and coal account for 82% (a) of U.S. energy consumption. Over the past 60 years (b), U.S. consumption of fossil fuels has grown faster than that of bioenergy or hydropower. Nuclear power grew considerably between 1970 and 2000. Data from U.S. Energy Information Administration, 2013.

budget. Today nuclear power, bioenergy, and hydropower together provide Sweden with over 60% of its energy and virtually all of its electricity.

Nuclear Power Nuclear power occupies an odd and conflicted position in our modern debate over energy. It is free of the air pollution produced by fossil fuel combustion, so it has long been put forth as an environmentally friendly alternative to fossil fuels, and it remains one of our most influential solutions to climate change. Yet nuclear power’s great promise has been clouded by nuclear weaponry, the dilemma of radioactive waste disposal, and the long shadow of Chernobyl and now Fukushima. As such, public safety concerns and the costs of addressing them have constrained nuclear power’s spread.

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Conventional alternatives provide much of our electricity

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TABLE 20.1  Top Producers of Nuclear Power

NATION United States France Japan

Neutron

NUCLEAR POWER ­CAPACITY (GIGAWATTS)

NUMBER OF REACTORS

PERCENTAGE ELECTRICITY FROM NUCLEAR POWER

102.1

104

19.0

63.1

58

74.8

44.2

50

2.1

Russia

23.6

33

17.8

South Korea

20.7

23

30.4

Canada

14.1

20

15.3

Ukraine

13.1

15

46.2

China

12.9

17

2.0

Germany

12.1

9

16.1

United Kingdom

9.9

18

18.1

Sweden

9.4

10

38.1

2012 data, from the International Atomic Energy Agency, 2013.

First developed commercially in the 1950s, nuclear power experienced most of its growth during the 1970s and 1980s. The United States generates the most electricity from nuclear power—over a quarter of the world’s production— yet only 19% of U.S. electricity comes from nuclear power. A number of other nations rely more heavily on nuclear power (TABLE 20.1). France leads the list, receiving 75% of its electricity from nuclear power.

Fission releases nuclear energy in reactors to generate electricity

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Strictly defined, nuclear energy is the energy that holds together protons and neutrons (p. 42) within the nucleus of an atom. We harness this energy by converting it to thermal energy inside nuclear reactors, facilities contained within nuclear power plants. This thermal energy is then used to generate electricity. The reaction that drives the release of nuclear energy inside nuclear reactors is nuclear fission, the splitting apart of atomic nuclei (FIGURE 20.3). In fission, the nuclei of large, heavy atoms, such as uranium or plutonium, are bombarded with neutrons. Ordinarily neutrons move too quickly to split nuclei when they collide with them, but if neutrons are slowed down they can break apart nuclei. Each split nucleus emits energy in the form of heat, light, and radiation, and also releases multiple neutrons. These neutrons (two to three in the case of uranium-235) can in turn bombard other nearby uranium-235 (235U) atoms, resulting in a self-sustaining chain reaction. If not controlled, this chain reaction becomes a runaway process of positive feedback (pp. 124–125)—the process that creates the explosive power of a nuclear bomb. Inside a nuclear power plant, however, fission is controlled so that, on average, only one of the two or three neutrons emitted with each fission event goes on to induce another fission event. In this way, the chain reaction maintains a constant output of energy at a controlled rate.

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Fission fragment (krypton, for example) Energy Free neutrons Nucleus of

235Uranium

Neutron Proton

Fission fragment (barium, for example)

FIGURE 20.3 Nuclear fission drives modern nuclear power. In nuclear fission, the nucleus of an atom of uranium-235 is bombarded with a neutron. The collision splits the uranium atom into smaller atoms and releases two or three neutrons, along with energy in the form of heat, light, and radiation. The neutrons can continue to split uranium atoms and set in motion a runaway chain reaction, so engineers at nuclear plants must absorb excess ­neutrons with control rods to regulate the rate of the reaction.

For fission to begin in a nuclear reactor, the neutrons bombarding uranium are slowed down with a substance called a moderator, most often water or graphite. As fission proceeds, it becomes necessary to soak up the excess neutrons produced when uranium nuclei divide, so that on average only a single neutron from each nucleus goes on to split another nucleus. For this purpose, control rods, made of a metallic alloy that absorbs neutrons, are placed into the reactor among the water-bathed fuel rods. Engineers move these control rods into and out of the water to maintain the fission reaction at the desired rate. All this takes place within the reactor core and is the first step in the electricity-generating process of a nuclear power plant (FIGURE 20.4). The reactor core is housed within a reactor vessel, and the vessel, steam generator, and associated plumbing are often protected within a containment building. Containment buildings, with their meter-thick concrete and steel walls, are constructed to prevent leaks of radioactivity due to accidents or natural catastrophes such as earthquakes. Not all nations require containment buildings, which points out the key role that government regulation plays in protecting public safety.

Nuclear energy comes from processed and enriched uranium We use the element uranium for nuclear power because it is radioactive. Radioactive isotopes, or radioisotopes (p. 42), emit subatomic particles and high-energy radiation as they decay into lighter radioisotopes until they ultimately become stable isotopes. The isotope uranium-235 decays into a series of daughter isotopes, eventually forming lead-207. Each radioisotope decays at a rate determined by that isotope’s half-life (p. 42), the time it takes for half of the atoms to give off radiation and decay. The half-life of 235U is about 700 million years. We obtain uranium from various minerals in naturally occurring ore (ore is rock that contains minerals of economic

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2 Water heated by fission circulates

through the primary loop, which is pressurized to prevent boiling.

1 Fission occurs in

the reactor core, where fuel rods are submerged in water. The water slows neutrons in order to initiate a chain reaction in uranium-235 in the fuel rods, while control rods absorb excess neutrons to regulate that reaction.

Control Primary Secondary loop loop rod Moderator (water)

3 Water heated by fission in

the primary loop boils water in the secondary loop, creating steam.

4 The steam drives turbines, which generate electricity.

Steam Turbine

Generator Cooling tower

Cooling tower

Reactor core Reactor Nuclear fuel Steam vessel (uranium) generator

Condenser

Cooling loop

5 Cold water from the cooling tower circulates within the

Containment building

cooling loop, condensing steam in the secondary loop and converting it to liquid water, which then returns to be boiled by the heated pressurized water of the primary loop.

FIGURE 20.4 Nuclear reactors produce electricity. In a pressurized light water reactor (the most common type of nuclear reactor), uranium fuel rods are placed in water, which slows neutrons so that fission can occur 1 . Control rods are moved into and out of the reactor core, absorbing excess neutrons to regulate the chain reaction. Water heated by fission circulates through the primary loop 2 and warms water in the secondary loop, which turns to steam 3 . Steam drives turbines, which generate electricity 4 . The steam is then cooled in the cooling tower by water from an adjacent river or lake and returns to the containment building 5 , to be heated again by heat from the primary loop.

Nuclear power delivers energy more cleanly than fossil fuels Using fission, nuclear power plants generate electricity without creating air pollution from stack emissions. In contrast, combusting fossil fuels can emit sulfur dioxide, which ­contributes

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to acid deposition; particulate matter, which threatens human health; and carbon dioxide and other greenhouse gases, which drive global climate change. Even considering all the steps involved in building plants and generating power, researchers from the International Atomic Energy Agency (IAEA) have calculated that nuclear power releases 4–150 times fewer emissions than fossil fuel combustion. Scientists estimate that

FIGURE 20.5 Enriched uranium fuel is packaged into fuel rods. These rods are encased in metal and used to power fission inside the cores of nuclear reactors. In this photo, fuel rods are being loaded into a circular arrangement beneath a pool of water inside a nuclear reactor in Brazil.

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interest [p. 655]). Uranium-containing minerals are uncommon, and uranium ore is in finite supply, so nuclear power is generally considered a nonrenewable energy source. Over 99% of the uranium in nature occurs as the isotope uranium-238. Uranium-235 (with three fewer neutrons) makes up less than 1% of the total. Because 238U does not emit enough neutrons to maintain a chain reaction when fissioned, we use 235 U for commercial nuclear power. Therefore, we must process the ore we mine to enrich the concentration of 235U to at least 3%. The enriched uranium is formed into pellets of uranium dioxide (UO2), which are incorporated into metallic tubes called fuel rods (FIGURE 20.5) that are used in nuclear reactors. After several years in a reactor, enough uranium has decayed so that the fuel no longer generates adequate energy, and it must be replaced with new fuel. In some countries, the spent fuel is reprocessed to recover the remaining usable energy. However, this process is costly relative to the low prices of uranium on the world market in recent years, so most spent fuel is disposed of as radioactive waste (pp. 582–584).

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TABLE 20.2 Risks and Impacts of Coal-fired versus Nuclear Power Plants TYPE OF IMPACT

COAL

NUCLEAR

Land and ecosystem disturbance from mining

Extensive, on surface or underground

Less extensive

Greenhouse gas emissions

Considerable emissions

None from plant operation; much less than coal over the entire life cycle

Other air pollutants

Sulfur dioxide, nitrogen oxides, particulate matter, and other pollutants

No pollutant emissions

Radioactive emissions

No appreciable emissions

No appreciable emissions during normal operation; possibility of emissions during severe accident

Occupational health among workers

More known health problems and fatalities

Fewer known health problems and fatalities

Health impacts on nearby residents

Air pollution impairs health

No appreciable known health impacts under n ­ ormal operation

Effects of accident or sabotage

No widespread effects

Potentially catastrophic widespread effects

Solid waste

More generated

Less generated

Radioactive waste

None

Radioactive waste generated

Fuel supplies remaining

Should last several hundred more years

Uncertain; supplies could last longer or shorter than coal supplies

For each type of impact, the more severe impact is indicated in red.

nuclear power helps the United States avoid emitting 600 million metric tons of carbon dioxide each year, equivalent to the CO2 emissions of almost all passenger cars in the nation and 11% of total U.S. CO2 emissions. Worldwide, nuclear power avoids emissions of 2.5 billion metric tons of carbon dioxide per year, about 7% of global CO2 emissions. Nuclear power has additional advantages over fossil fuels—coal in particular. For residents living downwind from power plants, scientists calculate that nuclear power poses far fewer chronic health risks from pollution than does fossil fuel combustion. For instance, nuclear power prevents the emission of half a million tons of nitrogen oxide and 1.4 million tons of sulfur dioxide each year that might otherwise be generated by coal plants. And because uranium generates far more power than coal by weight or volume, less of it needs to be mined, so uranium mining causes less damage to landscapes and generates less solid waste than coal mining. Moreover, in the course of normal operation, nuclear power plants are safer for workers than are coal-fired plants. Nuclear power also has drawbacks. One is that the waste it produces is radioactive, and arranging for safe disposal of this waste is challenging. The second main drawback is that if an accident occurs at a power plant, or if a plant is sabotaged, the consequences can potentially be catastrophic. Given this mix of advantages and disadvantages (TABLE 20.2), most governments (although not necessarily most citizens) have judged the good to outweigh the bad, and today the world has 435 operating nuclear plants in 31 nations.

Fusion remains a dream For as long as scientists and engineers have generated power from nuclear fission, they have tried to figure out how to harness nuclear fusion instead. Nuclear fusion—the process that drives our sun’s vast output of energy, and the force behind hydrogen bombs (thermonuclear bombs)—involves forcing together the small nuclei of lightweight elements under extremely high temperature and pressure. The hydrogen isotopes deuterium and tritium can be fused together to create helium, releasing a neutron and a tremendous amount of energy (FIGURE 20.6). Overcoming the mutually repulsive forces of protons in a controlled manner is difficult, and fusion requires temperatures of many millions of degrees Celsius. Thus, researchers have not yet developed this process for commercial power generation. Despite billions of dollars of funding and decades of research, fusion experiments in the lab still require scientists to input more energy than they produce from the process. That is, they experience a loss in net energy (p. 541) and a ratio of energy returned on investment (EROI; pp. 541–542) lower than 1.

2Hydrogen (deuterium)

3Hydrogen

WEIGHING THE ISSUES

576

CHOOSE YOUR RISK  Examine Table 20.2. Given the choice of living next to a nuclear power plant or living next to a coal-fired power plant, which would you choose? What would concern you most about each option?

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Energy

4He

Neutron

(tritium)

FIGURE 20.6 Can we harness nuclear fusion? In nuclear fusion, two small atoms, such as the hydrogen isotopes deuterium and tritium, are fused together, releasing energy along with a helium nucleus and a free neutron. So far, scientists have not been able to fuse atoms without supplying far more energy than the reaction produces, so this process is not used commercially.

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The accident was brought under control within days, the damaged reactor was shut down, and multi-billion-dollar cleanup efforts stretched on for years. Three Mile Island is best regarded as a near-miss; the emergency could have been far worse had the meltdown proceeded through the entire stock of uranium fuel or had the containment building not contained the radiation. Although residents have shown no significant health impacts in the years since, the event raised safety concerns in the United States and abroad. It was Three Mile Island that inspired Sweden’s referendum in 1980 that resulted in its national vote for a phaseout of nuclear power.

FIGURE 20.7 The Three Mile Island nuclear power plant near Harrisburg, Pennsylvania, suffered a partial meltdown in 1979. This emergency was a “near-miss”—radiation was released but was mostly contained, and no health impacts were confirmed. The incident put the world on notice, however, that a major accident could potentially occur.

If we could find a way to control fusion in a reactor, the potential payoffs would be immense: We could produce vast amounts of energy using water as a fuel, and the process would create only low-level radioactive wastes, without pollutant emissions or the risk of dangerous accidents, sabotage, or weapons proliferation. A consortium of industrialized nations is collaborating to build a prototype fusion reactor called the International Thermonuclear Experimental Reactor (ITER) in southern France. It aims to achieve an EROI of 10:1. Even if this multi-billion-dollar effort succeeds, however, power from fusion seems likely to remain many years in the future.

Chernobyl  In 1986 an explosion at the Chernobyl plant in Ukraine (part of the Soviet Union at the time) caused the most severe nuclear power plant accident the world has yet seen (FIGURE 20.8A). Engineers had turned off safety systems to FIGURE 20.8 The world’s worst nuclear accident unfolded in 1986 at Chernobyl. The destroyed reactor (a) was later encased in a massive concrete sarcophagus to contain further radiation leakage. Technicians scoured the landscape (b), measuring radiation levels, removing soil, and scrubbing roads and buildings. (a) The destroyed reactor at Chernobyl

Although nuclear power delivers energy more cleanly than fossil fuels, the possibility of catastrophic accidents has spawned a great deal of public anxiety. Three events have been most influential in shaping public opinion about nuclear energy: Three Mile Island in the United States was a near-miss; Chernobyl, the world’s most severe accident, shocked the world; and most recently, Fukushima Daiichi followed the 2011 Japanese earthquake and tsunami.

Three Mile Island  At the Three Mile Island plant in Pennsylvania in 1979 (FIGURE 20.7), a combination of mechanical failure and human error caused coolant water to begin draining from the reactor vessel, temperatures to rise inside the reactor core, and metal surrounding the uranium fuel rods to start melting, releasing radiation. This process is termed a meltdown, and it proceeded through half of one reactor core at Three Mile Island. Residents of Harrisburg and nearby towns stood ready to be evacuated as the nation held its breath, but fortunately most radiation remained trapped inside the containment building.

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(b) Technicians measuring radiation

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Nuclear power poses small risks of large accidents

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c­ onduct tests, and human error, combined with unsafe ­reactor design, led to explosions that destroyed the ­reactor and sent clouds of radioactive debris billowing into the ­atmosphere. For 10 days radiation escaped from the plant while ­emergency crews risked their lives putting out fires (some later died from radiation exposure). Most residents of the surrounding countryside remained at home for these 10 days, exposed to radiation, before the Soviet ­government belatedly began evacuating more than 100,000 people. In the months and years afterwards, workers erected a gigantic concrete sarcophagus around the demolished reactor, scrubbed buildings and roads, and removed irradiated materials FIGURE 20.8b). However, the landscape for at least 30 km (19 mi) around the plant remains contaminated, the demolished reactor is still full of dangerous fuel and debris, and radioactivity leaks from the hastily built and quickly deteriorating sarcophagus. Today an international team is trying to build a larger sarcophagus around the original one to prevent a catastrophic re-release of radiation. The accident killed 31 people directly and sickened or caused cancer in thousands more. Exact numbers are uncertain because of inadequate data and the difficulty of determining long-term radiation effects (see THE SCIENCE BEHIND THE STORY, pp. 580–581). Health authorities estimate that most of the 6000-plus cases of thyroid cancer diagnosed in people who were children at the time resulted from radioactive iodine spread by the accident. Estimates for the total number of cancer cases attributable to Chernobyl, past and future, vary widely, but an international consensus effort 20 years after the event estimated that radiation may have raised the cancer rate among exposed people by as much as a few percentage points, possibly resulting in several thousand fatal cancer cases. Atmospheric currents carried radioactive fallout from Chernobyl across much of the Northern Hemisphere, particularly Ukraine, Belarus, and parts of Russia and Europe (FIGURE 20.9). Fallout was greatest where rainstorms brought radioisotopes

Highest High Medium Low

Norwegian Sea

9.0 earthquake struck eastern Japan and sent an immense tsunami roaring onshore (pp. 40–41). Over 20,000 people were killed, and many thousands of buildings were destroyed. This natural disaster affected the operation of several of Japan’s nuclear plants, most notably the Fukushima Daiichi nuclear power plant. Here, the earthquake shut down power and the tsunami flooded the plant’s emergency power generators. The plant was protected by a 5.7-m (19-ft) seawall, but the tsunami reached 14 m (46 ft) high, and the generators were located in the basement of the plant (FIGURE 22.10a). Without electricity, workers could not use moderators and control rods to cool the uranium fuel, and the fuel began to overheat as fission proceeded, uncontrolled. Amid the damage and chaos across the region, help was slow to arrive, and workers had to begin flooding the reactors with seawater in a desperate effort to prevent meltdowns. Several explosions and fires occurred over the next few days, and eventually three reactors experienced full meltdowns, while the plant’s other three reactors were seriously damaged. Parts of the plant remained inaccessible for months because of radioactive water, and it will likely require decades to fully clean up the site. Radioactivity was released during and after these events at levels about one-tenth of those from Chernobyl. Much of the radioactivity spread by air or water into the Pacific Ocean, and trace amounts were detected around the world (FIGURE 20.10b). Thousands of residents of areas near the plant were evacuated and screened for radiation effects (FIGURE 22.10c), and restrictions were placed on food and water from the region. Over two years after the event, minor releases of radioactivity continued, and TEPCO (Tokyo Electric Power Company)—the

White Sea

Finland

Norway Ireland

Fukushima Daiichi  On March 11, 2011, a magnitude

Barents Sea

Cesium-137 deposition

Atlantic Ocean

down from the radioactive cloud. Parts of Sweden received high amounts of fallout, and the accident reinforced the ­Swedish public’s fears about nuclear power. A poll taken after the event showed that nearly half of Swedish citizens now regretted their own nation’s investment in nuclear power.

North Sea

United Kingdom

Sweden Denmark

Baltic Sea

Estonia Latvia

Russia

Lithuania

Netherlands

Po

ian a

Se

tic

ria

a Se

M20_WITH7428_05_SE_C20.indd 578

sp

Ad

578

Ca

rtu

ga

l

Poland Belarus Belgium Germany Czech Chernobyl France Republic Ukraine Austria Slovakia Moldova Switzerland Hungary Romania Slovenia Spain No Italy data Black Sea available Mediterranean Tyrrhenian Greece Sea Sea Turkey Aegean Ionian Sea Northern Africa Sea

FIGURE 20.9 Radioactive fallout from Chernobyl was deposited across Europe in complex patterns. Patterns of cesium-137 deposition resulted from atmospheric currents and rainstorms in the days following the accident. Although Chernobyl produced 100 times more fallout than the U.S. bombs dropped on Hiroshima and Nagasaki in World War II, it was distributed over a much wider area. Thus, levels of contamination in any given place outside of Ukraine, Belarus, and western Russia were relatively low; during these several days, the average European received less than the amount of radiation a person receives naturally in a year. Data from chernobyl.info, Swiss Agency for Development and Cooperation, Bern, 2005.

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Sea of Japan Fukushima

Pacific Ocean

JAPAN

(a) The tsunami barrels toward the Fukushima reactors

Spread of radiation fallout outward from the damaged plant site 0.9–1 0.7–0.9 0.6–0.7

0.4–0.6 0.3–0.4 0.1–0.3

0.01–0.1 0.005–0.01 0.001–0.005

(b) Most radiation drifted eastward over the ocean

FIGURE 20.10 The Fukushima Daiichi crisis was unleashed after an earthquake generated a massive tsunami. The tsunami tore through a seawall (a) and inundated the plant’s nuclear reactors. About 80% of the radiation that escaped from the plant drifted over the ocean, as shown in this map (b) of cesium-137 isotopes in the 9 days following the accident. Children evacuated from the region (c) were screened for radiation exposure. Data in (b) from Yasunari, T.J., et al. 2011. Cesium-137 deposition and contamination of Japanese soils due to the Fukushima nuclear accident. Proc. Natl. Acad. Sci. 108: 19530–19534.

plant’s owner—continued to ascertain what precisely went wrong. Long-term health effects on the region’s people remain uncertain and debated (see The Science behind the Story, pp. 580–581). Amid the extraordinary challenges of responding to the earthquake, tsunami, and nuclear crisis, the J­apanese government and TEPCO were criticized for not sharing full and accurate information with the p­ ublic. This, combined with the fact that TEPCO had failed to respond to earlier warnings that the plant was vulnerable to a large tsunami, shook the Japanese ­people’s confidence in their leaders and in nuclear power. In the aftermath of the disaster, the government idled all 50 of the nation’s nuclear reactors and embarked on safety inspections. In 2012, the government restarted a number of plants, arguing that electricity from them was necessary to avoid summertime blackouts. In response, large crowds of people demonstrated in protest, and some urged a national referendum on phasing out nuclear power. Across the world, many nations reassessed their nuclear programs, and Germany, Belgium, and Spain proposed to phase out nuclear power.

We are managing risks from nuclear power and nuclear weapons with some success

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It is fortunate that we have not experienced more accidents on the scale of Fukushima or Chernobyl. Yet smaller-scale incidents have occurred. A 1999 accident at a plant in Tokaimura, Japan, killed two workers and exposed over 400 others to leaked radiation. And Sweden experienced a near-miss in 2006, when the Forsmark plant north of Stockholm narrowly avoided a meltdown after only two of four generators started up following a power outage. In 2011 and 2012, U.S. reactors had nine emergency shutdowns in response to tornadoes, hurricanes, earthquakes, and flooding. Thankfully, the designs of most modern reactors are safer than Chernobyl’s, and designs for future plants promise more safety features. And in most emergencies at reactors around the world, safety systems have functioned well. For instance, Japan’s Onagawa power plant was closer to the epicenter of the 2011 quake, yet its safety systems protected it from serious damage. However, as plants around the world age, they require more maintenance and become less safe. There is also the

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(c) A Japanese child is screened for radiation

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THE SCIENCE BEHIND THE STORY 3000

Girls Boys

2500 2000 1500

Chernobyl: 1986

1000 500

membrane damage, and weakening of the immune system. In total, 28 people died from ARS soon after the accident. Those who died had the greatest estimated exposure to radiation. The major health consequence of Chernobyl’s radiation, however, has been thyroid cancer in children. The thyroid gland is where our bodies concentrate iodine, and one of the most common radioactive isotopes released early in the disaster was iodine-131 (131I). Children have large and active thyroid glands, so they are especially vulnerable to thyroid cancer induced by radioisotopes. Predicting that thyroid cancer might be a problem, medical workers measured iodine activity in the thyroid glands of several hundred thousand people in Russia, Ukraine, and Belarus following the accident. They also measured food contamination and surveyed people on their food consumption. These data showed that drinking milk from cows that had grazed on contaminated grass was the main route of exposure to 131I, although fresh vegetables also contributed. As doctors had feared, rates of thyroid cancer rose among children in regions of highest exposure (FIGURE 1). Multiple studies found linear doseresponse relationships (p. 394) in data from Ukraine and Belarus. By 2006, medical professionals estimated the number of cases at 6000 and rising. Fortunately, treatment of thyroid cancer

05

00 20

01

–2 0

95

–2 0

19

96

–1 9

90 91

–1 9 19

86 19

82

Chernobyl-area boy and his mother after his surgery for thyroid cancer.

–1 9

85

0

19

In the wake of the meltdowns at Japan’s Fukushima Daiichi nuclear power plant in 2011, Japanese authorities tried to keep residents safe while medical scientists from around the world rushed to study how the release of radiation might affect human health. Both looked back to lessons learned from Chernobyl 25 years earlier. Determining long-term health impacts of radiation exposure is ­enormously difficult, and initial attempts to predict Fukushima’s health impacts have stirred vigorous debate. Most scientists expect that the reactor failures at Fukushima will have less severe health consequences than those at Chernobyl, because less radiation was emitted at Fukushima and because most of it drifted over the ocean away from populated areas (see Figure 20.10b and pp. 44–45). However, judging Fukushima’s impacts will be challenging and will require long-term study. Let’s turn first to Chernobyl. The hundreds of researchers who have tried to pin down Chernobyl’s health impacts have sometimes differed in their conclusions. In an effort to reach consensus, the World Health Organization (WHO) engaged 100 experts to review all studies through 2006 and issue a report summarizing what scientists had learned in the 20 years since the accident. In 2008, a United Nations committee issued a comprehensive report as well. The most severe effects were documented in emergency workers who battled to contain the incident in its initial days. Medical staff treated and recorded the progress of 134 workers hospitalized with acute radiation sickness (ARS). Radiation destroys cells in the body, and if the destruction outpaces the body’s abilities to repair the damage, the person will soon die. Symptoms of ARS include vomiting, fever, diarrhea, thermal burns, mucous

Number of cases of thyroid cancer

Health Impacts of Chernobyl and Fukushima

Year

FIGURE 1 The incidence of thyroid cancer in girls and boys below age 18 began rising in regions of Ukraine, Belarus, and Russia that experienced the heaviest fallout of radioactive iodine from Chernobyl. Data from U.N. Scientific Committee on the Effects of Atomic Radiation, 2008. Sources and effects of ionizing radiation, Vol. 2. New York, 2011.

has a high success rate, so as of that time, only 15 children had died from it. Studies addressing other health aspects of the accident have found limited impact. Some research has shown an increase in cataracts due to radiation, especially among emergency workers. But neither the WHO nor U.N. assessments found evidence that rates of leukemia or any other cancer (aside from thyroid cancer) had risen among people exposed to Chernobyl’s radiation. Still, some cancers may appear decades after exposure, so it is possible that many illnesses have yet to arise. Moreover, conducting epidemiological studies (pp. 393–394) with enough statistical power to detect minor increases in rare events requires observing huge numbers of people over many years. When the Fukushima crisis struck, Japanese authorities applied lessons from Chernobyl. They provided iodine tablets to young people evacuated from the region and they restricted agriculture near the plant, stopping contaminated food and milk from entering the market. These measures to prevent people’s uptake of iodine-131 apparently were

580

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(a) After 36 hours

(b) After 180 hours

(c) After 324 hours

(d) After 468 hours 100 101 102 103 104 105 Cesium-137 concentration (micro-Becquerels per m3)

106

FIGURE 2 Radiation from cesium-137 spread around the world from Fukushima following the accident. Atmospheric modeling shows how this radioisotope spread for three weeks after the accident. Data from Ten Hoeve, J., and M. Jacobson, 2012. Worldwide health effects of the Fukushima Daiichi nuclear accident. Energy & Environmental Science, DOI 10.1039/c2ee22019a.

deaths than in Japan, despite a much lower population density. To generate their estimates, Ten Hoeve and Jacobson used a dose-response curve (p. 395) that extrapolates effects from high to low doses in a linear manner. However, some researchers believe there could be a threshold below which radiation has no health effects. These researchers felt that Ten Hoeve and Jacobson’s cancer estimates were likely too high. Meanwhile, their Stanford colleague Burton Richter wrote to the journal that—far from suggesting that nuclear power is dangerous—the number of fatalities from Fukushima is far less than Japan would have experienced from air pollution had its electricity been produced by fossil fuels instead! Time will tell what health impacts the Fukushima crisis causes. It will prove difficult to measure statistically rare instances of cancer in a large population exposed to very low doses, but researchers will try. They will be assisted by Japan’s government, which budgeted $1.2 billion for coordinated research into long-term health effects of radiation. Questionnaires were sent to all 2 million residents of Fukushima Prefecture, asking where they were in the days after the accident, and what they ate and drank. Thyroid exams are being given to all 360,000 children and teens from the region, and 20,000 pregnant women and their babies will be closely monitored. All 200,000 people evacuated from the area will get exams, and mental health support will be offered. If the research program can extend for 30 years, as the government intends, it could provide valuable information on the health effects of low-dose radiation.

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effective. In late March 2011, 1000 evacuated children were tested for 131 I exposure, and none showed evidence of a high dose affecting the thyroid. As the crisis was gradually brought under control, some researchers began predicting what long-term health impacts might arise. Using data on cancer rates from studies on survivors of the atomic bombs dropped on Hiroshima and Nagasaki, researchers extrapolated to predict cancer rates at the lower radiation doses from Fukushima. Frank Von Hippel in a 2011 study calculated that about 1 million people were exposed to more than 1 curie per km2 of radiation from cesium-137, which should result in a 0.1% increase in cancer risk among them, or 1000 cancer cases. In 2012, John Ten Hoeve and Mark Jacobson of Stanford University used a global atmospheric model together with data on radiation, population dispersion, and weather in the days following the event to estimate radiation levels people received (FIGURE 2). In the journal Energy and Environmental ­Science, they predicted that Fukushima’s radiation would eventually produce 125 cancerrelated deaths and 178 non-fatal cancer cases. Large uncertainties attended both estimates; the projected number of total cases ranged from 39 to 2900. Ten Hoeve and Jacobson then used their methods to predict the consequences of a hypothetical Fukushima-scale event taking place in the United States. They simulated Fukushima’s radiation releases as though they had occurred at the Diablo Canyon Power Plant in California, which lies on a major earthquake fault. Their computer simulations indicated that because of different weather patterns, such an accident might cause 25% more

581

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concern that radioactive material could be stolen from plants and used in terrorist attacks. This possibility has been especially worrisome in the cash-strapped nations of the former Soviet Union, where hundreds of former nuclear sites have gone without adequate security for years. Finally, there is the ever-present concern that more nations may develop nuclear weapons. To address concerns about stolen fuel and to reduce the world’s nuclear weapons stockpiles, the United States and Russia embarked on a remarkably successful program called Megatons to Megawatts. In this cooperative international agreement, the United States has been buying up weapons-grade uranium and plutonium from Russia, letting Russia process it into lower-enriched fuel, and diverting it to peaceful use in power generation. In recent years, up to 10% of America’s electricity has been generated from fuel recycled from Russian warheads that used to be atop missiles pointed at American cities! In 2013 it is expected that the last of 500 metric tons of highly enriched uranium will be processed and transferred, after which Russia and the United States may negotiate some sort of continuation of the program.

(a) Wet storage

Waste disposal remains a challenge

582

Even if nuclear power generation could be made completely safe, and even if we could recycle all weapons-grade fuel into fuel for power plants, we still would be left with the conundrum of what to do with spent fuel rods and other radioactive waste. Recall that fission utilizes 235U as fuel, leaving as waste the 97% of uranium that is 238U. This 238U, as well as all irradiated material and equipment that is no longer being used, must be disposed of in a location from which radiation will not escape. Because the half-lives of uranium, plutonium, and many other radioisotopes are far longer than multiple human lifetimes, this waste will continue emitting radiation for thousands of years. Thus, radioactive waste must be placed in unusually stable and secure locations where radioactivity will not harm future generations. Currently, nuclear waste from power generation is being held in temporary storage at nuclear power plants across the world. Spent fuel rods are sunken in pools of cooling water to minimize radiation leakage (FIGURE 20.11a). However, most U.S. plants have no room left for this type of storage, so they are now storing waste in thick casks of steel, lead, and concrete (FIGURE 20.11b). In total, U.S. power plants are storing nearly 70,000 metric tons of high-level radioactive waste—enough to fill a football field to the depth of 7 m (21 ft)—as well as much more low-level radioactive waste. This waste is held at more than 120 sites spread across 39 states (FIGURE 20.12). A 2005 report from the National Academy of Sciences judged that most of these sites were vulnerable to terrorist attacks. Over 161 million U.S. citizens live within 125 km (75 mi) of temporarily stored waste. Because storing waste at many dispersed sites creates a large number of potential hazards, nuclear waste managers would prefer to send all waste to a central repository that can be heavily guarded. In Sweden, that nation’s nuclear industry

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(b) Dry storage

FIGURE 20.11 Nuclear waste is stored at nuclear power plants, because no central repository yet exists. Spent fuel rods are kept in “wet storage” in pools of water (a), which keep them cool and reduce r­ adiation release, or in “dry storage” (b) in thick-walled casks layered with lead, concrete, and steel.

conducted 20 years of research looking for a suitable location, and in 2009 selected the Forsmark power plant site as its single disposal location. If the site is approved by government agencies and constructed as planned, spent fuel rods and other high-level waste will be systematically buried in canisters about 500 m (1650 ft) underground within stable bedrock. In the United States, the multiyear search homed in on Yucca Mountain, a remote site in the desert of southern Nevada, 160 km (100 mi) from Las Vegas (FIGURE 20.13a). Choice of this site followed extensive study by government scientists (FIGURE 20.13b), and $13 billion was spent on its development, although most Nevadans were not happy about the choice. In 2010, as the site was awaiting approval from the Nuclear Regulatory Commission, President Barack Obama’s a­ dministration ended support for the project. ­Ironically this came just days after Obama had urged expanding nuclear power in his State of the Union address. Most political ­observers agree that the opposition of Senate

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FIGURE 20.12 High-level

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Nuclear Energy Institute.

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radioactive waste from civilian reactors is currently stored at over 120 sites in 39 states across the United States. In this map, dots indicate storage sites and colors indicate the amount of waste stored in each state. Data from

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electricity (see Figure 21.5). It may take 20 years or more for most homeowners to break even on an investment in PV arrays or solar collectors. The high costs are due to the fact that the technologies are young and developing. Moreover, they are competing against energy sources (fossil fuels and nuclear power) that have remained relatively cheap as a result of decades of taxpayer support and whose external costs (pp. 164, 183) are not included in market prices. As a result, market prices have given governments, businesses, and consumers ­little economic incentive to switch to solar energy thus far. However, declines in price and improvements in efficiency of solar technologies so far are encouraging, even in the absence of significant funding from government and industry. At their advent in the 1950s, solar technologies had efficiencies of around 6% while costing $600 per watt. Today, PV cells are showing up to 20% efficiency commercially and 40% efficiency in lab research, suggesting that future solar cells could be more efficient than any energy technologies we have today. Solar systems are becoming less expensive and now can sometimes pay for themselves in less than 10–20 years. After that time, they provide energy virtually for free as long as the equipment lasts.

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Wind Power As the sun heats air in the atmosphere, the movement of differentially heated air masses produces wind. We can harness wind power from air’s movement by using wind turbines, mechanical assemblies that convert wind’s kinetic energy (p. 48), or energy of motion, into electrical energy.

Wind turbines convert kinetic energy to electrical energy Today’s wind turbines have their roots in Europe, where wooden windmills were used for 800 years to grind grain and pump water. The first wind turbine built to generate electricity was constructed in the late 1800s in Cleveland, Ohio. However, it was not until after the 1973 oil embargo that governments and industry in North America and Europe began funding research and development for wind power. In a modern wind turbine, wind turns the blades of the rotor, which rotate machinery inside a compartment called a nacelle, which sits atop a tower (Figure 21.12). Inside the nacelle

Gearbox (increases rotational speed of blades) Blades

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Nacelle

Roughly how much more solar radiation does southern Arizona receive than Germany?

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Figure 21.12 A wind turbine converts wind’s energy of motion into electrical energy. Wind causes a turbine’s blades to spin, turning a shaft that extends into the nacelle. Inside the nacelle, a gearbox converts the rotational speed of the blades, which can be up to 20 revolutions per minute (rpm) or more, into much higher speeds (over 1500 rpm). This provides adequate motion for the generator to produce electricity.

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are a gearbox, a generator, and equipment to monitor and control the turbine’s activity. Today’s towers average 80 m (260 ft) in height, and the largest are taller than a football field is long. Higher is generally better, to minimize turbulence (and potential damage) while maximizing wind speed. Turbines are often erected in groups; such a development is called a wind farm. The world’s largest wind farms contain hundreds of turbines spread across the landscape. Engineers design turbines to yaw, or rotate back and forth in response to changes in wind direction, ensuring that the motor faces into the wind at all times. Some turbines are designed to generate low levels of electricity by turning in light breezes. Others are programmed to rotate only in strong winds, generating large amounts of electricity in short time periods. Slight differences in wind speed yield substantial differences in power output, for two reasons. First, the energy content of wind increases as the square of its velocity; thus if wind velocity doubles, energy quadruples. Second, an increase in wind speed causes more air molecules to pass through the wind turbine per unit time, making power output equal to wind velocity cubed. Thus a doubled wind velocity results in an eightfold increase in power output.

Wind power is growing fast

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Figure 21.13 Global production of wind power has been doubling every three years in recent years, and prices have fallen slightly. Data from Global Wind Energy Council; and U.S. Department

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(a) Percentage of global wind power in each nation Denmark Portugal Spain Ireland Germany

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wind report: Annual market update 2012. GWEC, Brussels, Belgium; and (b) U.S.

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of Energy, EERE, 2012. 2011 Wind technologies market report.

Germany (11.1%)

Figure 21.14 Several nations are leaders in wind power. Most of the world’s wind power capacity (a) is concentrated in a handful of nations led by China, the United States, and Germany. Yet tiny Denmark (b) obtains the highest percentage of its electricity needs from wind. Data from (a) Global Wind Energy Council, 2013. Global Global wind power capacity (gigawatts)

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Department of Energy, EERE, 2012. 2011 Wind technologies market report.

Denmark leads the world in obtaining the greatest percentage of its energy from wind power. In this small European nation, wind farms supply nearly 30% of Danish electricity needs (Figure 21.14b). Germany is fifth in this respect, and the United States is 13th. Texas generates the most wind power of all U.S. states, while Iowa and South Dakota each obtain nearly 25% of their electricity from wind. Wind power’s growth in the United States has been haphazard because Congress has not committed to a long-term federal tax credit for wind development, but instead has passed a series of short-term renewals, leaving the industry uncertain about how much to invest. However, experts agree that wind power’s growth will continue, because only a small portion of this resource is currently being tapped and because wind power at favorable locations already generates electricity at prices nearly as low as fossil fuels (see Figure 21.5). A 2008 report by a consortium of experts outlined how the United States could meet fully one-fifth of its electrical demands with wind power by 2030.

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Like solar energy, wind provides just a small proportion of the world’s power needs, but wind power is growing fast—doubling every three years (Figure 21.13). Five nations account for threequarters of the world’s wind power output (Figure 21.14a), but dozens of nations now produce wind power. Germany had long produced the most, but the United States overtook it in 2008, and China surpassed the United States two years later.

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Figure 21.15 More and more wind farms are being developed offshore. Offshore winds tend to be stronger yet less turbulent.

Offshore sites hold promise Wind speeds on average are 20% greater over water than over land, and air is less turbulent over water. For these reasons, offshore wind turbines are becoming popular (Figure 21.15). Costs to erect and maintain turbines in water are higher, but the stronger, less turbulent winds produce more power and make offshore wind potentially more profitable. Today’s offshore wind farms are limited to shallow water, where towers are sunk into sediments singly or using a tripod configuration. In the future, towers may also be placed in deep water on floating pads anchored to the seafloor. Denmark erected the first offshore wind farm in 1991, and soon more came into operation across northern Europe, where the North Sea and Baltic Sea offer strong winds. Once Germany raised its feed-in tariff rate for offshore wind from 9 cents to 15 cents per kilowatt-hour in 2009, many projects began construction and today several are operating. By 2013, over 1800 wind turbines were operating in 65 wind farms in the waters of 10 European nations. In the United States, no offshore wind farms have yet been constructed, but development of the first was approved in 2010 after nine years of debate. The Cape Wind offshore wind farm, if constructed, will feature 130 turbines rising from Nantucket Sound 8 km (5 mi) off the coast of Cape Cod in Massachusetts. In announcing the government’s approval, U.S. Interior Secretary Ken Salazar predicted that it would be “the first of many projects up and down the Atlantic coast.” Indeed, as of 2013, eight offshore wind developments were in the planning stages off the Northeast coast, one off the Texas coast, and one in Lake Erie.

Wind power has many benefits

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Like solar power, wind power produces no emissions once the equipment is manufactured and installed. As a replacement for fossil fuel combustion in the average U.S. power plant, running a 1-megawatt wind turbine for 1 year prevents the release of more than 1500 tons of carbon dioxide, 6.5 tons of sulfur dioxide, 3.2 tons of nitrogen oxides, and 60 lb of mercury,

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according to the U.S. Environmental Protection Agency. The amount of carbon pollution that all U.S. wind turbines together prevent from entering the atmosphere is equal to the emissions from nearly 10 million cars, or from combusting the cargo of a 750-car freight train of coal each and every day. Under optimal conditions, wind power appears efficient in its energy returned on investment (EROI; pp. 541–542, 590–591). Most studies find that wind turbines produce roughly 20 times more energy than they consume. This EROI value is better than that from most other energy sources. Wind farms also use less water than do conventional power plants. Wind turbine technology can be used on many scales, from a single tower for local use to farms of hundreds that supply large regions. Small-scale turbine development can help make local areas more self-sufficient, just as solar energy can. For instance, the Rosebud Sioux Tribe of Native Americans set up a single turbine on its reservation in South Dakota. The turbine has been producing electricity for 200 homes and brings the tribe $15,000 per year in revenue. The tribe has now developed a 30-megawatt wind farm nearby, and 20 more turbines are slated to be added soon. Another benefit of wind power is that farmers and ranchers can lease their land for wind development. A single large turbine can bring in $2000 to $4500 in annual royalties while occupying just a quarter-acre of land. Most of the land can still be used for agriculture. Royalties from the wind power company provide the farmer or rancher revenue while also increasing property tax income for their rural community. Wind power involves up-front expenses to erect turbines and to expand infrastructure to allow electricity distribution, but over the lifetime of a project it requires only maintenance costs. Unlike fossil-fuel power plants, wind turbines incur no ongoing fuel costs. Startup costs of wind farms generally are higher than those of fossil-fuel plants, but wind farms incur fewer expenses once they are up and running. Moreover, advancing technology is driving down the costs, per unit of electricity produced, of wind farm construction. Finally, just as solar energy creates job opportunities, so does wind power. Roughly 85,000 Americans and nearly 700,000 people globally are now employed in the wind industry. More than 100 colleges and universities now offer programs and degrees that train people in the skills needed for jobs in wind power and other renewable energy fields.

Wind power has some downsides Wind is an intermittent resource; we have no control over when it will occur. This is a major limitation in relying on wind as an electricity source, but it is lessened if wind is one of several sources contributing to a utility’s power generation. Pumped-storage hydropower (p. 592) can help to compensate during windless times, and batteries or hydrogen fuel (p. 621) can store energy generated by wind and release it later when needed. Just as wind varies from time to time, it varies from place to place; some areas are windier than others. Global wind patterns combine with local topography—mountains, hills, water bodies, forests, cities—to create local wind patterns.

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Resource planners and wind power companies study these patterns closely before planning a wind farm. Meteorological research has given us data with which to judge prime areas for locating wind farms. A map of average wind speeds across the United States (Figure 21.16a) reveals that mountainous regions are best, along with areas of the Great Plains. Based on such information, the wind power industry has located much of its generating capacity in states with high wind speeds (Figure 21.16b). Provided that wind farms are strategically erected in optimal locations, an estimated 15% of U.S. energy demand could be met using only 43,000 km2 (16,600 mi2) of land (with less than 5% of this land area actually occupied by turbines, equipment, and access roads).

However, most of North America’s people live near the coasts, far from the Great Plains and mountain regions that have the best wind resources. Thus, continent-wide transmission networks would need to be enhanced to send wind power’s electricity to these population centers. When wind farms are proposed near population centers, local residents often oppose them. Turbines are generally located in exposed, conspicuous sites, and some people object to wind farms for aesthetic reasons, feeling that the structures clutter the landscape. Although polls show wide public approval of existing wind projects and of the concept of wind power, newly proposed wind projects often elicit the not-in-my-backyard (NIMBY) syndrome among people living

Average wind speed at 80 m above ground (m/sec) 9.5–>10.5 8.5–9.5 7.5–8.5 6.5–7.5 5.5–6.5 4.5–5.5 0–4.5

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NH (171) VT (119) ME (431) WI (648)

NY MA (100) (1638) MI RI (9) IA (988) PA NE (5133) IL (1340) OH NJ (9) (459) (3568) IN (428) DE (2) KS (1543) MO MD (120) (2713) (459) OK TN (29) WV (583) (3134)

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(b) Wind generating capacity, 2013

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Figure 21.16 Wind speed varies from place to place. Maps of average wind speeds (a) help guide the placement of wind farms. Another map (b) shows megawatts of wind-power-generating capacity developed in each U.S. state through early 2013. Sources: (a) U.S. National Renewable Energy Laboratory; (b) American Wind Energy Association, 2013. 1st Quarter 2013 Market Report.

Compare parts (a) and (b). Which states or regions have high wind speeds but are not yet heavily developed with commercial wind power?

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nearby. For instance, the Cape Wind project has faced years of opposition from wealthy residents of Cape Cod, Nantucket, and Martha’s Vineyard, even though many of these residents consider themselves progressive environmentalists. Wind turbines also pose a threat to birds and bats, which are killed when they fly into the rotating blades. More research on wildlife impacts is urgently needed (see The Science behind the Story, pp. 610–611). One strategy for protecting birds and bats may be selecting sites that are not on migratory flyways or in the midst of prime habitat for species that are likely to fly into the blades.

Weighing The Issues Wind and NIMBY  If you could choose to get your electricity from a wind farm or a coal-fired power plant, which would you choose? How would you react if the electric utility proposed to build the wind farm that would generate your electricity atop a ridge running in back of your neighborhood, such that the turbines would be clearly visible from your living room window? Would you support or oppose the development? Why? If you would oppose it, where would you suggest the farm be located? Do you think anyone might oppose it in that location?

Geothermal Energy Geothermal energy is thermal energy that arises from beneath Earth’s surface. The radioactive decay of elements (p. 42) amid the extremely high pressures deep in the interior of our planet generates heat that rises to the surface through magma (molten rock, p. 52) and through cracks and fissures. Where this energy heats groundwater, natural spurts of heated water and steam are sent up from below and may erupt through the surface as terrestrial geysers (p. 51) or submarine hydrothermal vents (p. 51). Geothermal energy manifests itself at the surface in these ways only in certain areas, and regions vary in their geothermal resources (Figure 21.17). One geothermally rich area is in California near Napa Valley’s wine country. There, engineers have for years operated the world’s largest geothermal power plants, The Geysers. The nation of Iceland also has a wealth of geothermal energy resources because it is built from lava that extruded and cooled at the Mid-Atlantic Ridge (pp. 52–53), along the spreading boundary of two tectonic plates. Because of the geothermal heat in this region, volcanoes and geysers are numerous in Iceland.

We harness geothermal energy for heating and electricity

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Geothermal energy can be harnessed directly from geysers at the surface, but most often wells must be drilled down hundreds or thousands of meters toward heated groundwater. Hot groundwater can be used directly for heating homes, offices, and greenhouses; for driving industrial processes; and for drying crops. Iceland heats nearly 90% of its homes through direct heating with piped hot water. Direct use of naturally

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