The Work of Nature: How The Diversity Of Life Sustains Us

By Yvonne Baskin, Harold A. Mooney, Jane Lubchenco and 2 more

The lavish array of organisms known as "biodiversity" is an intricately linked web that makes the earth a uniquely habitable planet. Yet pressures from human activities are destroying biodiversity at an unprecedented rate. How many species can be lost before the ecological systems that nurture life begin to break down?

In The Work of Nature, noted science writer Yvonne Baskin examines the threats posed to humans by the loss of biodiversity. She summarizes and explains key findings from the ecological sciences, highlighting examples from around the world where shifts in species have affected the provision of clean air, pure water, fertile soils, lush landscapes, and stable natural communities.

As Baskin makes clear, biodiversity is much more than number of species -- it includes the complexity, richness, and abundance of nature at all levels, from the genes carried by local populations to the layout of communities and ecosystems across the landscape. Ecologists are increasingly aware that mankind's wanton destruction of living organisms -- the planet's work force -- threatens to erode our basic life support services. With uncommon grace and eloquence, Baskin demonstrates how and why that is so.

Distilling and bringing to life the work of the world's leading ecologists, The Work of Nature is the first book of its kind to clearly explain the practical consequences of declining biodiversity on ecosystem health and function.

• Language: English
• Publisher: Island Press
• Release date: Apr 10, 2013
• ISBN: 9781597268998

Book preview

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About Island Press

Island Press is the only nonprofit organization in the United States whose principal purpose is the publication of books on environmental issues and natural resource management. We provide solutions-oriented information to professionals, public officials, business and community leaders, and concerned citizens who are shaping responses to environmental problems.

In 1994, Island Press celebrated its tenth anniversary as the leading provider of timely and practical books that take a multidisciplinary approach to critical environmental concerns. Our growing list of titles reflects our commitment to bringing the best of an expanding body of literature to the environmental community throughout North America and the world.

Support for Island Press is provided by Apple Computer, Inc., The Bullitt Foundation, The Geraldine R. Dodge Foundation, The Energy Foundation, The Ford Foundation, The W. Alton Jones Foundation, The Lyndhurst Foundation, The John D. and Catherine T. MacArthur Foundation, The Andrew W. Mellon Foundation, The Joyce Mertz-Gilmore Foundation, The National Fish and Wildlife Foundation, The Pew Charitable Trusts, The Pew Global Stewardship Initiative, The Rockefeller Philanthropic Collaborative, Inc., and individual donors.

More than ever, our effect on the biological systems of the planet will rebound to affect us. A slash and burn approach to the biosphere is no longer viable. Indeed the planet already has a reduced capacity to support Man. We need a populace and politicians aware that all decisions have a biological component, and that biology is inextricably interwoven with sociology and economics. As the planet becomes simpler biologically, it becomes more expensive economically: fish are smaller and dearer; lumber is narrower, shorter and more expensive; dwindling natural resources fuel inflation. The planet also is more vulnerable to disaster, and the quality of life inevitably declines.

Conservation is sometimes perceived as stopping everything cold, as holding whooping cranes in higher esteem than people. It is up to science to spread the understanding that the choice is not between wild places or people. Rather it is between a rich or an impoverished existence for Man.

Thomas E. Lovejoy

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Copyright © 1997 by The Scientific Committee on Problems of the Environment (SCOPE).

Illustrations copyright © 1997 by Abigail Rorer.

First paperback edition published in 1998.

All rights reserved under International and Pan-American Copyright Conventions. No part of this book may be reproduced in any form or by any means without permission in writing from the publisher: Island Press, 1718 Connecticut Avenue, N.W., Suite 300, Washington, DC 20009.

ISLAND PRESS is a trademark of The Center for Resource Economics.

Library of Congress Cataloging-in-Publication Data

Baskin, Yvonne.

The work of nature: how the diversity of life sustains us/ Yvonne Baskin.

p. cm.

Includes bibliographical references and index.

9781597268998

1. Environmentalism. 2. Biological diversity. 3. Human ecology. 4. Conservation of natural resources. I. Title.

GE195.B36 1997

333.7’2—dc21

96-52051

CIP

Printed on recycled, acid-free paper e9781597268998_i0003.jpg

Manufactured in the United States of America

10 9 8 7 6 5 4 3

Table of Contents

About Island Press

Title Page

Copyright Page

Foreword - Of Keystone Complexes and Nature’s Services

Preface

Acknowledgements

CHAPTER ONE - This Web of Life

CHAPTER TWO - The "Keystone Club: Who’s Important

CHAPTER THREE - Community Ties

CHAPTER FOUR - Water: The Essence of Life

CHAPTER FIVE - The Vitality of the Soil

CHAPTER SIX - Of Plants and Productivity

CHAPTER SEVEN - The Power to Shape the Land

CHAPTER EIGHT - Climate and Atmosphere

CHAPTER NINE - Do We Still Need Nature?

Notes

Index

Foreword

Of Keystone Complexes and Nature’s Services

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Ecologists are well aware of the critical nature of the services supplied to humanity by natural ecosystems, but they sometimes are surprised at the subtlety and complexity of the interactions that can be involved in supplying them. For example, Tree Swallows and Violet-green Swallows help to provide an important ecosystem service in the vicinity of the Rocky Mountain Biological Laboratory (RMBL), where our group does summer research. That service is natural pest control; swallows snatch insects in mid-air, and thus greatly reduce the numbers of mosquitoes and other biting flies that otherwise make researchers’ lives miserable. They also generally help to prevent outbreaks of insect populations. Recent work by Gretchen Daily of Stanford University and her colleagues illuminates some of the unexpected ways in which the swallows’ role as pest-control agents depends on other species, including microbes.¹

Around RMBL the swallows must nest in old woodpecker holes, the vast majority of which were made by Red-naped Sapsuckers. Sapsuckers are among the few non-human animals that don’t simply consume resources, they work to mobilize them. Early in the season, sapsuckers drill holes in aspen and spruce trees, and then lap up the sugary sap that oozes from the holes, or wells. They also excavate nest holes in the aspens. But when the young sapsuckers hatch, the adults switch to a new, rich source of sap: willow shrubs. They cut rectangular wells in the willow bark and peck away at the upper edge of the well to encourage the flow of sap, which averages about 29 percent sugar. Not only do the adults feed on the sap themselves; they dip captured insects in the high-energy fluid before feeding them to their nestlings. When the young are fledged, they join their parents at the wells.

There is one other major living piece to the puzzle. The sapsuckers can only excavate nest holes in aspen trees whose trunks have first been softened by infection with a heart-rot fungus. Thus the presence of the swallows depends upon a keystone complex consisting of sapsuckers, aspens, willows, and a fungus.

Furthermore, many other organisms—including wasps, butterflies, warblers, hummingbirds, chipmunks, and squirrels—steal sap from the sapsucker wells. In some areas, in the absence of flowers as nectar sources, the spring range of hummingbirds is extended by the presence of sapsucker wells. The warblers, hummers, and wasps also contribute to the pest-control service.

There are myriad other ways in which the delivery of ecosystem services depends on biodiversity—Earth’s living wealth, the most important part of humanity’s stock of natural capital. Many are explained in The Work of Nature. It is a beautifully written volume, based on an extensive technical survey carried out by outstanding ecologists from all over the world. The book emphasizes that biodiversity is not simply an amenity, a luxury that humanity can do without. It explains that biodiversity is much more than simply the number of species that inhabits our planet, but that it includes critical genetic resources, a diversity of ecosystems and landscapes, and perhaps most crucial, a diversity of populations. The importance of the latter is demonstrated by a simple thought experiment. Suppose every species were reduced to just a single small population in a zoo, aquarium, botanic garden, or bucket of soil—the smallest population that would let that species persist for, say, one hundred years.² There would be no loss of species diversity, but all ecosystems, devoid of living organisms, would crash, and Homo sapiens would almost certainly go extinct.

The Work of Nature is an especially important book as the millennium approaches, when the American public is being bombarded with anti-environmental rhetoric and misinformation about biodiversity, denigrating the threat posed by the extinction crisis to the human enterprise.³ Consider the following anti-environmental or brownlash statement:

[East] of San Francisco [and] in all directions around Atlanta and Denver and Warsaw and Madrid, and in many similar locations worldwide, extensive tracts of habitat that have known only occasional human intervention abut centers of mechanistic human excess.⁴

But going east from San Francisco, one first finds highly modified and polluted San Francisco Bay, with the vast majority of its biodiversity-rich coastal marshes destroyed. Beyond the Bay are Oakland, Alameda, San Leandro, and other cities and suburbs, and then the completely agricultural Central Valley of California. In that area, usually bathed in a brown, human-created haze that can extend far into the Great Basin, virtually all natural habitat is gone. After the Central Valley come mountain ranges, where human intervention has exterminated the previously important top predator, the grizzly bear; completely changed the hydrological cycle; infested streams with giardia parasites; created vast damage by herding cattle and sheep, mining, timbering; and caused huge areas of the overgrazed intermountain valleys to be carpeted with introduced plants.

Beyond the vastly overpopulated front range of the Rockies, one reaches the Great Plains, where it is virtually impossible to find even small areas with a semblance of the original vegetation and minute remnants of the previously gigantic buffalo herds that once dominated them. Next come the intensively farmed prairies, where at best a few scraps of relatively unaltered grassland communities remain. In the eastern United States are farms and urban-suburban sprawl interspersed with fragmented and largely second-growth forests, often altered by acid rain and heavy-metal pollution. Wolves and cougars have been extirpated from the East, leaving a plague of deer and ticks that carry Lyme disease. Finally, one reaches the polluted and overfished Atlantic Ocean. Need I go on? In fact, as you will learn in the pages that follow, when human beings (perhaps aided by climate change) wiped out the Pleistocene megafauna, they altered the face of North America substantially and permanently. This was long before Europeans invaded the continent.

Contrary to the ill-informed assertion quoted above, the world is nearly devoid of habitats that have known only occasional human intervention. Not only has most of the terrestrial surface been directly modified by building, paving, plowing, grazing, drilling, mining, clearing, logging, draining, pumping, or damming; but all of it has been affected by poisoning. Moreover, human intervention has more or less permanently altered the oceans by depleting fish and whale stocks, destroying coral reefs and coastal marshes, and emitting toxic pollutants. Indeed, every cubic centimeter of the biosphere has been altered by human-induced changes in the climate and the chemical composition of the atmosphere.

Purveyors of anti-environmental rhetoric apparently fail to appreciate the stakes in the game they are playing. The very future of humanity is in the balance. The scale of the human enterprise—the numbers of people multiplied by the average environmental impact of each—is now roughly twenty times greater than it was in 1850,⁵ and as a consequence humanity has become a truly global force. Our species is altering the surface and atmosphere of Earth in ways unprecedented since the catastrophe that wiped out the dinosaurs 65 million years ago.

The most irreversible of human assaults on the environment is the one on biodiversity, for once extinct in the wild, populations usually can only be reestablished with great difficulty, and extinct species are gone forever. Humanity depends entirely on ecosystem services, and as this fine volume demonstrates, to a large degree those services depend on biodiversity. In essence, by killing off its only known living companions in the universe, Homo sapiens is destroying its own life support systems and catapulting itself toward ecological disaster. I hope The Work of Nature will help stop that process before it is too late.

Paul R. Ehrlich

Stanford University

Preface

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Commissioned by the Scientific Committee on Problems of the Environment (SCOPE), this book summarizes and also marks the culmination of an exciting and innovative scientific endeavor. The goal of that endeavor was to answer a single key question: What are the possible consequences of the accelerating losses in biodiversity? Until recently, major concerns regarding biological extinction have been mostly ethical ones involving questions about our responsibility for the earth’s biological heritage, and economic ones focusing on the potential loss of such economically valuable products as drugs, herbs, and foodstuffs.

The Work of Nature looks at biological diversity differently. Rather than examining ecosystems in terms of the goods (food, fiber, etc.) they provide, the book assesses biodiversity in terms of the earth’s ability to provide the ecological services, such as clean air and water, upon which humankind depends. Indeed, the major question of the book is, Are these services being impaired as we lose biological diversity?

The search for answers began in 1991, when SCOPE launched a program specifically to review and evaluate all scientific literature relevant to the subject of ecosystem functioning. We, as chair of the SCOPE Scientific Steering Committee responsible for the program and member of the Executive Committee, respectively, felt such a program was well suited to SCOPE’s overall agenda. Formed by the International Council of Scientific Unions and based in Paris, SCOPE is a nongovernmental body, which has thirty-eight member nations and access to some of the world’s best scientists. Indeed, SCOPE regularly calls on scientists from around the world, asking them to provide assessments of crucial global environmental problems. The organization then serves as a powerful vehicle for translating scientific knowledge into a format that is both accessible and timely. Among the issues SCOPE has tackled are the environmental consequences of nuclear conflict, climate warming, and altered global biogeochemical cycles.

The SCOPE Program on Ecosystem Functioning of Biodiversity mobilized hundreds of scientists around the world, specialists in the major ecosystems of the earth, including coral reefs, tropical forests, deserts, and tundra. Coming together initially in a series of ecosystem-specific workshops, these scientists reviewed existing data on the impact of diversity losses on ecosystem functioning. Thereafter, they met as a single group to compare results from their respective systems and assess similarities and differences. We are grateful to the John D. and Catherine T. MacArthur Foundation for supporting this phase of the study.

Subsequently, the United Nations Environment Program (UNEP) launched a Global Biodiversity Assessment, which incorporated and expanded the SCOPE project. Overall, the assessment was ground breaking because it represented the first time the significance of biodiversity loss on ecosystem functioning had ever been addressed.

By pushing ecological study in an entirely new direction, certain challenges were created, among them the need to evaluate evidence collected for other purposes. No direct experimental studies of the impact of biological loss on ecological services had ever been undertaken. Thus, much of the data that was needed to shed light on the question had to be drawn from interpretations of natural patterns and the ecological responses to both additions of species, resulting from invasions or introductions, and deletions of species, caused, for example, by selective harvesting. The SCOPE project relied on this data to draw the conclusions that form the foundation for this book.

Believing the topic to be both vitally important and timely, we encouraged the SCOPE Scientific Steering Committee to commission a book that would effectively deliver the project’s findings to a broad audience. The result is the book before you. Indeed, The Work of Nature represents an enormously successful effort to translate scientific documents into a form accessible to a general reader. Yvonne Baskin has carried out this translation in a very special way. In a relatively short time, she not only mastered the significance of vast amounts of highly technical information but she also sought out and talked with many of the key scientists involved in the research she describes. Her words explain with exceptional clarity and eloquence how scientists deeply involved with these crucial issues think about their subject. We thank you, Yvonne.

Harold A. Mooney

Paul S. Achilles Professor of

Environmental Biology, Stanford

University

Jane Lubchenco

Wayne and Gladys Valley Professor of

Marine Biology, Oregon State

University; Oregon State University

Distinguished Professor; and

President, American Association for

the Advancement of Science, 1996

Acknowledgements

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My first encounter with SCOPE and its project on ecosystem functioning and biodiversity took place in February 1994 when I was sent to Asilomar, California, to write a news article about the group’s findings for Science magazine. Those five days at a SCOPE workshop amid the Monterey pine groves on the Pacific coast provided me, a science journalist, with an entirely new perspective on the natural world and the vital roles species play in generating our ecological life-support systems. It was the beginning of a process of discovery that necessarily shifted into warp speed a year later when Harold A. (Hal) Mooney asked me to convert the group’s three-year effort into a book for general readers. First and foremost, then, I am fundamentally indebted to the hundreds of scientists around the world who took part in the SCOPE project. Without their syntheses, recently published in half a dozen technical volumes, this book could not have been written.

I was especially fortunate to have the guidance of the scientific advisory committee assembled for this project: Hal Mooney of Stanford University, Jane Lubchenco of Oregon State University, Anthony C. Janetos of NASA’s Mission to Planet Earth, Osvaldo E. Sala of the University of Buenos Aires, Rodolfo Dirzo of Universidad Nacional Autonoma de Mexico, and J. Hall Cushman of Sonoma State University. Their careful reading of the first draft of the manuscript provided me with invaluable criticisms and new insights that helped to improve the final version. I’m particularly grateful to Hal and Jane, who repeatedly and generously provided assistance, advice, encouragement, and enthusiasm during early fits and starts as the book took shape and who later conscientiously read and critiqued multiple drafts.

I also owe special thanks to a number of reviewers who read one or more chapters and offered helpful suggestions and tactful advice, including Edith B. Allen of the University of California, Riverside; Gary Allison at Oregon State University; Stephen Carpenter of the University of Wisconsin, Madison; John J. (Jack) Ewel of the Institute of Pacific Islands Forestry in Honolulu; Christopher Field of the Carnegie Institution of Washington; Diana Freckman of Colorado State University; Lawrence E. Gilbert of the University of Texas, Austin; Elaine Ingham of Oregon State University; Simon Levin of Princeton University; John Pastor of the University of Minnesota, Duluth; Louis F. Pitelka of the Appalachian Environmental Laboratory in Frostburg, Maryland; William Schlesinger of Duke University; David Tilman of the University of Minnesota, St. Paul; and Joy Zedler of San Diego State University. In addition, I’m deeply grateful to Nancy Huntly of Idaho State University, who read the entire manuscript and provided a very encouraging appraisal along with her detailed and thoughtful critique.

In the end, of course, it remains the author’s task to correct and revise the manuscript, and any errors or deficiencies that remain after so much good advice are her responsibility alone.

I want to express deep appreciation also to Laurie Burnham, editorial director of Shearwater Books at Island Press, who devoted an enormous amount of time, thought, and much-needed advice to this project, starting long before this book was officially her responsibility. My thanks also to SCOPE for providing financial support for this project, and particularly to SCOPE Executive Director Veronique Plocq-Fichelet, who handled the contractual details of getting the book into print.

Most of all, I’m thankful for the terrific personal and professional support of my husband, Mike Gilpin, who kept me on course, guided me out of deadends, and helped lighten my inevitable black moods when it seemed the book would never be finished. He was the first to see each chapter in its roughest form and always provided invaluable direction while helping to redeem my ecological naivete. All this while enduring an acute loss of attention and companionship for months on end. Finally, my parents, though far away, were always a steadying and supportive presence, in part because the love of nature and the outdoors they instilled in me made the inevitable pain of producing this book seem worthwhile.

CHAPTER ONE

This Web of Life

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Overleaf

Ecologists are starting to probe how plants and animals help to generate vital ecological services such as productivity and nutrient cycling.

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Our oldest faiths and deepest symbols reflect a primal connection to the natural world, to a living planet that long ago imprinted on the human consciousness a cyclic sense of death and decay, rebirth and renewal. We do not question that flesh and bone and leaf litter will decay to dust, that seeds will sprout season after season and find renewed nourishment in the soil, that rivers can flow endlessly without running dry, that we can breathe for a lifetime without depleting the air of oxygen. Despite our fascination with other worlds and our hopeful probing of outer space, we’ve found no other planet where any of these things are true. What humans have not fully appreciated until recently is that these services are the work of nature, performed by the rich diversity of microbes, plants, and animals on the earth.

It is this lavish array of organisms that we call biodiversity, an intricately linked web of living things whose activities work in concert to make the earth a uniquely habitable planet. But today, as never before, the species in this web are under siege, threatened by human activities that encroach on their habitats. At the same time, ecologists are increasingly aware that the impoverishment of species—the planet’s work force—threatens to erode the basic life-support services that render the earth hospitable for humanity. Indeed, we are approaching a crossroads in time, when the survival and extinction of other species may well delimit the future of Homo sapiens.

Consider what life has done and continues to do for the earth.

Some 4 billion years ago, the primordial atmosphere was a ghastly brew, devoid of oxygen and unable to shield the earth’s surface from the scorching, molecule-cleaving ultraviolet radiation of the young sun. Eventually life changed all that. Over billions of years, photosynthetic organisms in the sea released enough oxygen to create a protective ozone shield and a reservoir of free oxygen that allowed the first plants to venture onto the land. Through the alchemy of enzymes and solar energy, green plants from plankton to redwoods still carry on photosynthesis, turning water and carbon dioxide into free oxygen and also the carbon-based sugars needed to build all living tissues. These are the raw materials that underpin the earth’s food webs and generate the food, fiber, timber, and fuel that sustain human societies.

Together, plants, animals, and microbes perform an array of vital services. They generate and preserve fertile soils. They break down organic wastes, from leaf litter to feces and flesh, recycling the mineral nutrients, carbon, and nitrogen needed for new plant growth. They absorb and break down pollutants; help maintain a benign mix of gases in the atmosphere; regulate the amount of solar energy the earth absorbs; moderate regional weather and rainfall; modulate the water cycle, minimizing floods and drought and purifying waters; blunt the impact of the seas that batter the land margins; pollinate crops; and control the vast majority of potential crop pests and carriers of human disease.

In addition, this rich abundance of organisms serves as a genetic library, a catalog of solutions to the problems of living on the earth. This catalog is written in the language of DNA, and from it human societies have derived crops, livestock, medicines, and many other commodities.¹

On a larger scale, the earth’s various species form populations that are aligned into communities and ecological systems—ecosystems, for short—which deliver such subsidies as clean air, pure water, and lush landscapes. Ecosystems, flexibly defined, are living communities interacting with the physical environment in a specific geographical place. An ecosystem may be as small as a rotting log or a pond or as large as a spruce forest or a vast lake. Of course, species are the critical components, the cogs and wheels of functioning ecosystems. Lose too many species from a forest—the trees, the truffle-forming fungi on their roots, the insects that prey on tree-destroying pests, the beavers that create ponds and meadows amid the woods—and at some point the assemblage ceases to work like a forest.

One question increasingly on the minds of ecologists is, how many species can the earth’s communities lose before the ecological systems that nurture life begin to falter? To take the extreme, if nature had to run with a skeleton crew, what organisms would be absolutely vital to maintain the earth as a living planet? Probably the only truly indispensable groups of organisms are the plants that capture carbon and solar energy and the ranks of decomposers that release the nutrients and energy in dead plant litter for reuse.² But a conservation agenda based on this extreme would ignore the elaborate tangle of loops and flourishes in the food webs, the intricate array of consumers that eat plants and predators that eat consumers, the symbionts, parasites, and other hangers-on who have claimed places for themselves in the earth’s myriad communities. Such an agenda would overlook virtually all the charismatic creatures on today’s conservation hot lists: pandas, wolves, elephants, bald eagles. Unfortunately, that agenda would also sacrifice civilization, which is supported by many of those loops and flourishes in the web of life.

If we are realistic about our dreams for tomorrow, our goal is not really saving the planet in some minimalist form, but perpetuating its atmosphere, climate, landscapes, and living services in a state that allows human civilizations to prosper. For that to occur, we need to preserve natural systems that are rich, healthy, and resilient enough to continue to support human welfare and economic activity for the next decade, the next century, and beyond. Some twenty-five years ago, as the space-age metaphor of Spaceship Earth took hold, ecologists Eugene P. Odum of the University of Georgia and his brother, Howard T. Odum, of the University of Florida first used the engineering term life-support systems to describe the earth’s self-renewing, life-giving natural ecosystems. ³,⁴ It is these systems, not a mere skeleton crew, that human societies must seek to maintain.

Thus, the real questions facing ecologists today center on how much biological diversity any particular ecosystem needs to remain functional, self-sustaining, and life supporting. How many species must humanity protect, and which ones and where, to assure pure water supplies from an alpine watershed; to preserve the fertility of tropical soils; to prevent cactus and shrubs from taking over productive grasslands; to maintain local rainfall patterns; to nurture coastal shrimp and fish populations; or to assure the integrity of pristine wildlands we value for recreation, tourism, or cultural traditions?

Conservationists have long asserted that every species counts to some degree in keeping the earth’s life-support systems working. Some play crucial roles day to day; others step into the breach only in times of stress or disturbance. Until recently, however, researchers have made little concerted effort to define the functional roles played by specific plants, animals, or microbes. In truth, function itself is a human concept. Organisms were not designed by natural selection to fill slots on an assembly line; each organism strives to make a living and reproduce itself. But as it eats, grows, excretes waste, and moves about, disturbing the physical environment, it unwittingly plays a part in generating grander processes that alter the flow of water, the recycling of energy and materials, the renewal of the atmosphere.

An Emerging Science

It may seem surprising that scientists know so little about species’ roles in generating ecological services. Yet unraveling links between the feeding behavior of an animal or the nutrient-cycling traits of a plant and subsequent changes in the character of a landscape or the chemistry of the soil may require years of observations, experiments, and analysis. Sometimes this work spans professional lifetimes and thus extends well beyond the practical scope of graduate student projects and the longevity of most research grants.

The questions also cross the lines of professional disciplines. Until recently, there were specialists who studied ecosystems and others who studied species and populations, and there was minimal discourse between them. Ecologists concerned with ecosystem processes such as nutrient cycles and energy flows, for instance, have traditionally