insight review articles Consequences of changing biodiversity F.Stuart Chapin Ill,Erika S.Zavaleta,Valerie T.Eviners,Rosamond L.Naylor,Peter M.Vitousek, Heather L.Reynoldsll,David U.Hooper,Sandra Lavorel#,Osvaldo E.Sala,Sarah E.Hobbie, Michelle C.Mack*&Sandra Diaz *Institute of Arctic Biology,University of Alaska,Fairbanks,Alaska 99775,USA (e-mail:fschapin@lter.uaf.edu) +Department of Biological Sciences andInstitute for International Studies,Stanford University,Stanford,California 94305,USA $Department of Integrative Biology,University of California,Berkeley.California 94720,USA lDepartment of Biology,Kalamazoo College,Kalamazoo,Michigan 49006,USA Department of Biology,Western Washington University,Bellingham,Washington 98225,USA #Centre d'Ecologie Fonctionnelle et Evolutive,CNRS UPR 9056,34293 Montpellier Cedex 05,France Catedra de Ecologia and Instituto de Fisiologia y Ecologia Vinculadas a la Agricultura,Faculty of Agronomy,University of Buenos Aires,Ave San Martin 4453,Buenos Aires C1417DSE,Argentina Department of Ecology,Evolution,and Behavior,University of Minnesota,St Paul,Minnesota55108,USA Instituto Multidisciplinario de Biologia Vegetal,Universidad Nacional de Cordoba,FCEFyN,Casilla de Correo 495,5000 Cordoba,Argentina Human alteration of the global environment has triggered the sixth major extinction event in the history of life and caused widespread changes in the global distribution of organisms.These changes in biodiversity alter ecosystem processes and change the resilience of ecosystems to environmental change.This has profound consequences for services that humans derive from ecosystems.The large ecological and societal consequences of changing biodiversity should be minimized to preserve options for future solutions to global environmental problems. umans have extensively altered the global preserves,native species are often out-competed or con- environment, changing global sumed by organisms introduced from elsewhere.Extinction biogeochemical cycles,transforming land and is a natural process,but it is occurring at an unnaturally rapid enhancing the mobility of biota.Fossil-fuel rate as a consequence of human activities.Already we have combustion and deforestation have increased causedtheextinctionof5-20%ofthespecies in many groups the concentration of atmospheric carbon dioxide(CO,) oforganisms(Fig.2),and current rates ofextinction are esti- by 30%in the past three centuries(with more than half of mated to be 100-1,000 timesgreater than pre-humanrates5 this increase occurring in the past 40 years).We have In the absence of major changes in policy and human more than doubled the concentration of methane and behaviour,our effects on the environment will continue to increased concentrations of other gases that contribute to alter biodiversity.Land-use change is projected to have the climate warming.In the next century these greenhouse largest global impact on biodiversity by the year 2100, gases are likely to cause the most rapid climate change that followed by climate change,nitrogen deposition,species the Earth has experienced since the end of the last introductions and changing concentrations ofatmospheric glaciation 18,000 years ago and perhaps a much longer CO,(ref.6).Land-use change is expected to be of particular time.Industrial fixation of nitrogen for fertilizer and other importance in the tropics,climatic change is likely to be human activities has more than doubled the rates of important at high latitudes,and a multitude of interacting terrestrial fixation of gaseous nitrogen into biologically causeswillaffectother biomes(Fig.3).Whataretheecolog- available forms.Run off of nutrients from agricultural and ical and societal consequences of current and projected urban systems has increased several-fold in the developed effects of human activity on biological diversity? river basins of the Earth,causing major ecological changes in estuaries and coastal zones.Humans have transformed Ecosystem consequences of altered diversity 40-50%of the ice-free land surface,changing prairies, Diversity at all organizational levels,ranging from genetic forests and wetlands into agricultural and urban systems. diversity within populations to the diversity of ecosystems in We dominate(directly or indirectly)about one-third of landscapes,contributes to global biodiversity.Here we focus the net primary productivity on land and harvest fish that on species diversity,because the causes,patterns and conse- use 8%of ocean productivity.We use 54%of the available quences of changes in diversity at this level are relatively well fresh water,with use projected to increase to 70%by documented.Species diversity has functional consequences 2050.Finally,the mobility of people has transported because the number and kinds of species present determine organisms across geographical barriers that long kept the the organismal traits that influence ecosystem processes. biotic regions of the Earth separated,so that many of the Species traits may mediate energy and material fluxes direct- ecologically important plant and animal species of many ly or may alter abiotic conditions (for example,limiting areas have been introduced in historic time? resources,disturbance and climate)that regulate process Together these changes have altered the biological diver- rates.The components of species diversity that determine sity ofthe Earth(Fig.1).Many species have beeneliminated this expression of traits include the number of species from areas dominated by human influences.Even in present(species richness),their relativeabundances(species 234 2000 Macmillan Magazines Ltd NATURE|VOL 405|11 MAY 2000 www.nature.cominsight review articles 234 NATURE | VOL 405 | 11 MAY 2000 | www.nature.com Humans have extensively altered the global environment, changing global biogeochemical cycles, transforming land and enhancing the mobility of biota. Fossil-fuel combustion and deforestation have increased the concentration of atmospheric carbon dioxide (CO2) by 30% in the past three centuries (with more than half of this increase occurring in the past 40 years). We have more than doubled the concentration of methane and increased concentrations of other gases that contribute to climate warming. In the next century these greenhouse gases are likely to cause the most rapid climate change that the Earth has experienced since the end of the last glaciation 18,000 years ago and perhaps a much longer time. Industrial fixation of nitrogen for fertilizer and other human activities has more than doubled the rates of terrestrial fixation of gaseous nitrogen into biologically available forms. Run off of nutrients from agricultural and urban systems has increased several-fold in the developed river basins of the Earth, causing major ecological changes in estuaries and coastal zones. Humans have transformed 40–50% of the ice-free land surface, changing prairies, forests and wetlands into agricultural and urban systems. We dominate (directly or indirectly) about one-third of the net primary productivity on land and harvest fish that use 8% of ocean productivity. We use 54% of the available fresh water, with use projected to increase to 70% by 20501 . Finally, the mobility of people has transported organisms across geographical barriers that long kept the biotic regions of the Earth separated, so that many of the ecologically important plant and animal species of many areas have been introduced in historic time2,3. Together these changes have altered the biological diver￾sity of the Earth (Fig. 1). Many species have been eliminated from areas dominated by human influences. Even in preserves, native species are often out-competed or con￾sumed by organisms introduced from elsewhere. Extinction is a natural process, but it is occurring at an unnaturally rapid rate as a consequence of human activities. Already we have caused the extinction of 5–20% of the species in many groups of organisms (Fig. 2), and current rates of extinction are esti￾mated to be 100–1,000 times greater than pre-human rates4,5. In the absence of major changes in policy and human behaviour, our effects on the environment will continue to alter biodiversity. Land-use change is projected to have the largest global impact on biodiversity by the year 2100, followed by climate change, nitrogen deposition, species introductions and changing concentrations of atmospheric CO2 (ref. 6). Land-use change is expected to be of particular importance in the tropics, climatic change is likely to be important at high latitudes, and a multitude of interacting causes will affect other biomes (Fig. 3)6 . What are the ecolog￾ical and societal consequences of current and projected effects of human activity on biological diversity? Ecosystem consequences of altered diversity Diversity at all organizational levels, ranging from genetic diversity within populations to the diversity of ecosystems in landscapes, contributes to global biodiversity. Here we focus on species diversity, because the causes, patterns and conse￾quences of changes in diversity at this level are relatively well documented. Species diversity has functional consequences because the number and kinds of species present determine the organismal traits that influence ecosystem processes. Species traits may mediate energy and material fluxes direct￾ly or may alter abiotic conditions (for example, limiting resources, disturbance and climate) that regulate process rates. The components of species diversity that determine this expression of traits include the number of species present (species richness), their relative abundances (species Consequences of changing biodiversity F. Stuart Chapin III*, Erika S. Zavaleta†, Valerie T. Eviner§, Rosamond L. Naylor‡, Peter M. Vitousek†, Heather L. Reynolds||, David U. Hooper¶, Sandra Lavorel#, Osvaldo E. Sala✩, Sarah E. Hobbie**, Michelle C. Mack* & Sandra Díaz†† *Institute of Arctic Biology, University of Alaska, Fairbanks, Alaska 99775, USA (e-mail: fschapin@lter.uaf.edu) †Department of Biological Sciences and ‡Institute for International Studies, Stanford University, Stanford, California 94305, USA §Department of Integrative Biology, University of California, Berkeley, California 94720, USA ||Department of Biology, Kalamazoo College, Kalamazoo, Michigan 49006, USA ¶Department of Biology, Western Washington University, Bellingham, Washington 98225, USA #Centre d’Ecologie Fonctionnelle et Evolutive, CNRS UPR 9056, 34293 Montpellier Cedex 05, France ✩Cátedra de Ecología and Instituto de Fisiología y Ecología Vinculadas a la Agricultura, Faculty of Agronomy, University of Buenos Aires, Ave San Martín 4453, Buenos Aires C1417DSE, Argentina **Department of Ecology, Evolution, and Behavior, University of Minnesota, St Paul, Minnesota 55108, USA ††Instituto Multidisciplinario de Biología Vegetal, Universidad Nacional de Córdoba, FCEFyN, Casilla de Correo 495, 5000 Córdoba, Argentina Human alteration of the global environment has triggered the sixth major extinction event in the history of life and caused widespread changes in the global distribution of organisms. These changes in biodiversity alter ecosystem processes and change the resilience of ecosystems to environmental change. This has profound consequences for services that humans derive from ecosystems. The large ecological and societal consequences of changing biodiversity should be minimized to preserve options for future solutions to global environmental problems. © 2000 Macmillan Magazines Ltd