Stephen R. Carpenter

Land use has generally been considered a local environmental issue, but it is becoming a force of global importance. Worldwide changes to forests, farmlands, waterways, and air are being driven by the need to provide food, fiber, water, and shelter to more than six billion people. Global croplands, pastures, plantations, and urban areas have expanded in recent decades, accompanied by large increases in energy, water, and fertilizer consumption, along with considerable losses of biodiversity. Such changes in land use have enabled humans to appropriate an increasing share of the planet's resources, but they also potentially undermine the capacity of ecosystems to sustain food production, maintain freshwater and forest resources, regulate climate and air quality, and ameliorate infectious diseases. We face the challenge of managing trade-offs between immediate human needs and maintaining the capacity of the biosphere to provide goods and services in the long term.

The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries—climate change and biosphere integrity—have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.

In the coming years, continued population growth, rising incomes, increasing meat and dairy consumption and expanding biofuel use will place unprecedented demands on the world's agriculture and natural resources. Can we meet society's growing food needs while reducing agriculture's environmental harm? Here, an international team of environmental and agricultural scientists uses new geospatial data and models to identify four strategies that could double food production while reducing environmental impacts. First, halt agricultural expansion. Second, close 'yield gaps' on underperforming lands. Third, increase cropping efficiency. And finally, we need to change our diets and shift crop production away from livestock feed, bioenergy crops and other non-food applications. Increasing population and consumption are placing unprecedented demands on agriculture and natural resources. Today, approximately a billion people are chronically malnourished while our agricultural systems are concurrently degrading land, water, biodiversity and climate on a global scale. To meet the world’s future food security and sustainability needs, food production must grow substantially while, at the same time, agriculture’s environmental footprint must shrink dramatically. Here we analyse solutions to this dilemma, showing that tremendous progress could be made by halting agricultural expansion, closing ‘yield gaps’ on underperforming lands, increasing cropping efficiency, shifting diets and reducing waste. Together, these strategies could double food production while greatly reducing the environmental impacts of agriculture.

Walker, B., C. Holling, S. R. Carpenter and A. P. Kinzig 2004. Resilience, adaptability and transformability in social–ecological systems. Ecology and Society 9(2): 5. https://doi.org/10.5751/ES-00650-090205

Ecological ApplicationsVolume 8, Issue 3 p. 559-568 Article NONPOINT POLLUTION OF SURFACE WATERS WITH PHOSPHORUS AND NITROGEN S. R. Carpenter, S. R. Carpenter Center for Limnology, 680 North Park Street, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorN. F. Caraco, N. F. Caraco Institute of Ecosystem Studies, Box AB Route 44A, Millbrook, New York 12545 USASearch for more papers by this authorD. L. Correll, D. L. Correll Smithsonian Environmental Research Center, P.O. Box 28, Edgewater Maryland 21037 USASearch for more papers by this authorR. W. Howarth, R. W. Howarth Section of Ecology and Systematics, Cornell University, Ithaca, New York 14853 USASearch for more papers by this authorA. N. Sharpley, A. N. Sharpley USDA-ARS, Pasture Systems and Watershed Management Research Laboratory, Curtin Road, University Park, Pennsylvania 16802 USASearch for more papers by this authorV. H. Smith, V. H. Smith Department of Systematics and Ecology, 6007 Haworth Hall, University of Kansas, Lawrence, Kansas 66045 USASearch for more papers by this author S. R. Carpenter, S. R. Carpenter Center for Limnology, 680 North Park Street, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorN. F. Caraco, N. F. Caraco Institute of Ecosystem Studies, Box AB Route 44A, Millbrook, New York 12545 USASearch for more papers by this authorD. L. Correll, D. L. Correll Smithsonian Environmental Research Center, P.O. Box 28, Edgewater Maryland 21037 USASearch for more papers by this authorR. W. Howarth, R. W. Howarth Section of Ecology and Systematics, Cornell University, Ithaca, New York 14853 USASearch for more papers by this authorA. N. Sharpley, A. N. Sharpley USDA-ARS, Pasture Systems and Watershed Management Research Laboratory, Curtin Road, University Park, Pennsylvania 16802 USASearch for more papers by this authorV. H. Smith, V. H. Smith Department of Systematics and Ecology, 6007 Haworth Hall, University of Kansas, Lawrence, Kansas 66045 USASearch for more papers by this author First published: 01 August 1998 https://doi.org/10.1890/1051-0761(1998)008[0559:NPOSWW]2.0.CO;2Citations: 3,460 Reprints of this 10-page report are available for $1.50 each. Prepayment is required. Order reprints from the Ecological Society of America. Attention: Reprint Department, 2010 Massachusetts Avenue, NW, Suite 400, Washington, D.C. 20036. Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Agriculture and urban activities are major sources of phosphorus and nitrogen to aquatic ecosystems. Atmospheric deposition further contributes as a source of N. These nonpoint inputs of nutrients are difficult to measure and regulate because they derive from activities dispersed over wide areas of land and are variable in time due to effects of weather. In aquatic ecosystems, these nutrients cause diverse problems such as toxic algal blooms, loss of oxygen, fish kills, loss of biodiversity (including species important for commerce and recreation), loss of aquatic plant beds and coral reefs, and other problems. Nutrient enrichment seriously degrades aquatic ecosystems and impairs the use of water for drinking, industry, agriculture, recreation, and other purposes. Based on our review of the scientific literature, we are certain that (1) eutrophication is a widespread problem in rivers, lakes, estuaries, and coastal oceans, caused by overenrichment with P and N; (2) nonpoint pollution, a major source of P and N to surface waters of the United States, results primarily from agriculture and urban activity, including industry; (3) inputs of P and N to agriculture in the form of fertilizers exceed outputs in produce in the United States and many other nations; (4) nutrient flows to aquatic ecosystems are directly related to animal stocking densities, and under high livestock densities, manure production exceeds the needs of crops to which the manure is applied; (5) excess fertilization and manure production cause a P surplus to accumulate in soil, some of which is transported to aquatic ecosystems; and (6) excess fertilization and manure production on agricultural lands create surplus N, which is mobile in many soils and often leaches to downstream aquatic ecosystems, and which can also volatilize to the atmosphere, redepositing elsewhere and eventually reaching aquatic ecosystems. If current practices continue, nonpoint pollution of surface waters is virtually certain to increase in the future. Such an outcome is not inevitable, however, because a number of technologies, land use practices, and conservation measures are capable of decreasing the flow of nonpoint P and N into surface waters. From our review of the available scientific information, we are confident that: (1) nonpoint pollution of surface waters with P and N could be reduced by reducing surplus nutrient flows in agricultural systems and processes, reducing agricultural and urban runoff by diverse methods, and reducing N emissions from fossil fuel burning; and (2) eutrophication can be reversed by decreasing input rates of P and N to aquatic ecosystems, but rates of recovery are highly variable among water bodies. Often, the eutrophic state is persistent, and recovery is slow. Citing Literature Volume8, Issue3August 1998Pages 559-568 This article also appears in:Centennial Special: Notable Papers in ESA History RelatedInformation

Many complex systems, ranging from ecosystems to financial markets and the climate, can have critical thresholds or tipping points where a sudden shift from one stable state to a contrasting regime may occur. Predicting such critical points before they are reached is extremely difficult, but work in different fields of science is now suggesting the existence of generic early warning signals that may indicate for a wide class of systems if a critical threshold is approaching. Scheffer et al. conclude their review of this work optimistically: in situations where the existence of a critical transition is suspected, the generic character of the warning signs suggests that they may provide valuable information on whether the probability of a major event is increasing. Complex dynamical systems, ranging from ecosystems to financial markets and the climate, can have tipping points at which a sudden shift to a contrasting dynamical regime may occur. Although predicting such critical points before they are reached is extremely difficult, work in different scientific fields is now suggesting the existence of generic early-warning signals that may indicate for a wide class of systems if a critical threshold is approaching.

Until recently, large apex consumers were ubiquitous across the globe and had been for millions of years. The loss of these animals may be humankind’s most pervasive influence on nature. Although such losses are widely viewed as an ethical and aesthetic problem, recent research reveals extensive cascading effects of their disappearance in marine, terrestrial, and freshwater ecosystems worldwide. This empirical work supports long-standing theory about the role of top-down forcing in ecosystems but also highlights the unanticipated impacts of trophic cascades on processes as diverse as the dynamics of disease, wildfire, carbon sequestration, invasive species, and biogeochemical cycles. These findings emphasize the urgent need for interdisciplinary research to forecast the effects of trophic downgrading on process, function, and resilience in global ecosystems.

Integrated studies of coupled human and natural systems reveal new and complex patterns and processes not evident when studied by social or natural scientists separately. Synthesis of six case studies from around the world shows that couplings between human and natural systems vary across space, time, and organizational units. They also exhibit nonlinear dynamics with thresholds, reciprocal feedback loops, time lags, resilience, heterogeneity, and surprises. Furthermore, past couplings have legacy effects on present conditions and future possibilities.

Resilience thinking addresses the dynamics and development of complex social-ecological systems (SES).Three aspects are central: resilience, adaptability and transformability.These aspects interrelate across multiple scales.Resilience in this context is the capacity of a SES to continually change and adapt yet remain within critical thresholds.Adaptability is part of resilience.It represents the capacity to adjust responses to changing external drivers and internal processes and thereby allow for development along the current trajectory (stability domain).Transformability is the capacity to cross thresholds into new development trajectories.Transformational change at smaller scales enables resilience at larger scales.The capacity to transform at smaller scales draws on resilience from multiple scales, making use of crises as windows of opportunity for novelty and innovation, and recombining sources of experience and knowledge to navigate social-ecological transitions.Society must seriously consider ways to foster resilience of smaller more manageable SESs that contribute to Earth System resilience and to explore options for deliberate transformation of SESs that threaten Earth System resilience.

Journal Article Cascading Trophic Interactions and Lake Productivity: Fish predation and herbivory can regulate lake ecosystems Get access Stephen R. Carpenter, Stephen R. Carpenter Search for other works by this author on: Oxford Academic Google Scholar James F. Kitchell, James F. Kitchell Search for other works by this author on: Oxford Academic Google Scholar James R. Hodgson James R. Hodgson Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 35, Issue 10, November 1985, Pages 634–639, https://doi.org/10.2307/1309989 Published: 01 November 1985

<h2>Abstract</h2> Occasionally, surprisingly large shifts occur in ecosystems. Theory suggests that such shifts can be attributed to alternative stable states. Verifying this diagnosis is important because it implies a radically different view on management options, and on the potential effects of global change on such ecosystems. For instance, it implies that gradual changes in temperature or other factors might have little effect until a threshold is reached at which a large shift occurs that might be difficult to reverse. Strategies to assess whether alternative stable states are present are now converging in fields as disparate as desertification, limnology, oceanography and climatology. Here, we review emerging ways to link theory to observation, and conclude that although, field observations can provide hints of alternative stable states, experiments and models are essential for a good diagnosis.

Social and ecological vulnerability to disasters and outcomes of any particular extreme event are influenced by buildup or erosion of resilience both before and after disasters occur. Resilient social-ecological systems incorporate diverse mechanisms for living with, and learning from, change and unexpected shocks. Disaster management requires multilevel governance systems that can enhance the capacity to cope with uncertainty and surprise by mobilizing diverse sources of resilience.

The Millennium Ecosystem Assessment (MA) introduced a new framework for analyzing social–ecological systems that has had wide influence in the policy and scientific communities. Studies after the MA are taking up new challenges in the basic science needed to assess, project, and manage flows of ecosystem services and effects on human well-being. Yet, our ability to draw general conclusions remains limited by focus on discipline-bound sectors of the full social–ecological system. At the same time, some polices and practices intended to improve ecosystem services and human well-being are based on untested assumptions and sparse information. The people who are affected and those who provide resources are increasingly asking for evidence that interventions improve ecosystem services and human well-being. New research is needed that considers the full ensemble of processes and feedbacks, for a range of biophysical and social systems, to better understand and manage the dynamics of the relationship between humans and the ecosystems on which they rely. Such research will expand the capacity to address fundamental questions about complex social–ecological systems while evaluating assumptions of policies and practices intended to advance human well-being through improved ecosystem services.

All Change Research on early warning signals for critical transitions in complex systems such as ecosystems, climate, and global finance systems recently has been gathering pace. At the same time, studies on complex networks are starting to reveal which architecture may cause systems to be vulnerable to systemic collapse. Scheffer et al. (p. 344 ) review how previously isolated lines of work can be connected, conclude that many critical transitions (such as escape from the poverty trap) can have positive outcomes, and highlight how the new approaches to sensing fragility can help to detect both risks and opportunities for desired change.

New studies are documenting trophic cascades in theoretically unlikely systems such as tropical forests and the open ocean. Together with increasing evidence of cascades, there is a deepening understanding of the conditions that promote and inhibit the transmission of predatory effects. These conditions include the relative productivity of ecosystems, presence of refuges and the potential for compensation. However, trophic cascades are also altered by humans. Analyses of the extirpation of large animals reveal loss of cascades, and the potential of conservation to restore not only predator populations but also the ecosystem-level effects that ramify from their presence.

Understanding the relationship between diversity and stability requires a knowledge of how species interact with each other and how each is affected by the environment. The relationship is also complex, because the concept of stability is multifaceted; different types of stability describing different properties of ecosystems lead to multiple diversity-stability relationships. A growing number of empirical studies demonstrate positive diversity-stability relationships. These studies, however, have emphasized only a few types of stability, and they rarely uncover the mechanisms responsible for stability. Because anthropogenic changes often affect stability and diversity simultaneously, diversity-stability relationships cannot be understood outside the context of the environmental drivers affecting both. This shifts attention away from diversity-stability relationships toward the multiple factors, including diversity, that dictate the stability of ecosystems.

Approaches to natural resource management are often based on a presumed ability to predict probabilistic responses to management and external drivers such as climate.They also tend to assume that the manager is outside the system being managed.However, where the objectives include long-term sustainability, linked social-ecological systems (SESs) behave as complex adaptive systems, with the managers as integral components of the system.Moreover, uncertainties are large and it may be difficult to reduce them as fast as the system changes.Sustainability involves maintaining the functionality of a system when it is perturbed, or maintaining the elements needed to renew or reorganize if a large perturbation radically alters structure and function.The ability to do this is termed "resilience."This paper presents an evolving approach to analyzing resilience in SESs, as a basis for managing resilience.We propose a framework with four steps, involving close involvement of SES stakeholders.It begins with a stakeholder-led development of a conceptual model of the system, including its historical profile (how it got to be what it is) and preliminary assessments of the drivers of the supply of key ecosystem goods and services.Step 2 deals with identifying the range of unpredictable and uncontrollable drivers, stakeholder visions for the future, and contrasting possible future policies, weaving these three factors into a limited set of future scenarios.Step 3 uses the outputs from steps 1 and 2 to explore the SES for resilience in an iterative way.It generally includes the development of simple models of the system's dynamics for exploring attributes that affect resilience.Step 4 is a stakeholder evaluation of the process and outcomes in terms of policy and management implications.This approach to resilience analysis is illustrated using two stylized examples.

Abstract: Conservation decisions about how, when, and where to act are typically based on our expectations for the future. When the world is highly unpredictable and we are working from a limited range of expectations, however, our expectations will frequently be proved wrong. Scenario planning offers a framework for developing more resilient conservation policies when faced with uncontrollable, irreducible uncertainty. A scenario in this context is an account of a plausible future. Scenario planning consists of using a few contrasting scenarios to explore the uncertainty surrounding the future consequences of a decision. Ideally, scenarios should be constructed by a diverse group of people for a single, stated purpose. Scenario planning can incorporate a variety of quantitative and qualitative information in the decision‐making process. Often, consideration of this diverse information in a systemic way leads to better decisions. Furthermore, the participation of a diverse group of people in a systemic process of collecting, discussing, and analyzing scenarios builds shared understanding. The robustness provided by the consideration of multiple possible futures has served several groups well; we present examples from business, government, and conservation planning that illustrate the value of scenario planning. For conservation, major benefits of using scenario planning are ( 1 ) increased understanding of key uncertainties, ( 2 ) incorporation of alternative perspectives into conservation planning, and ( 3 ) greater resilience of decisions to surprise.

Both natural and managed ecosystems experience large fluctuations in submersed macrophyte biomass. These fluctuations have important consequences for ecosystem processes because of the effects of macrophytes on the physical/chemical environment and littoral biota. The first part of this paper reviews the effects of submersed macrophytes on the physical environment (light extinction, temperature, hydrodynamics, substrate), chemical environment (oxygen, inorganic and organic carbon, nutrients) and the biota (epiphytes, grazers, detritivores, fishes). This extensive literature suggests that variations in macrophyte biomass could have major effects on aquatic ecosystems. The second part of this paper considers the ecosystem consequence of several common changes in submersed macrophytes: replacement of vascular macrophytes by bryophytes during lake acidification; short-term biomass changes caused by invasions of adventive species, cultural eutrophication or macrophyte management; and changes in littoral grazers. These scenarios illustrate the importance of macrophytes in ecosystems, but raise any questions which cannot be answered at present. Controlled, whole-lake macrophyte experiments are needed to resolve these open questions.

We performed whole-lake manipulations of fish populations to test the hypothesis that higher trophic levels regulate zooplankton and phytoplankton community structure, biomass, and primary productivity. The study involved three lakes and spanned 2 yr. Results demonstrated hierarchical control of primary production by abiotic factors and a trophic cascade involving fish predation. In Paul Lake, the reference lake, productivity varied from year to year, illustrating the effects of climatic factors and the natural dynamics of unmanipulated food web interactions. In Tuesday Lake, piscivore addition and planktivore reduction caused an increase in zooplankton biomass, a compositional shift from a copepod/rotifer assemblage to a cladoceran assemblage, a reduction in algal biomass, and a continuous reduction in primary productivity. In Peter Lake, piscivore reduction and planktivore addition decreased zooplanktivory, because potential planktivores remained in littoral refugia to escape from remaining piscivores. Both zooplankton biomass and the dominance of large cladocerans increased. Algal biomass and primary production increased because of increased concentrations of gelatinous colonial green algae. Food web effects and abiotic factors were equally potent regulators of primary production in these experiments. Some of the unexplained variance in primary productivity of the world's lakes may be attributed to variability in fish populations and its effects on lower trophic levels.

Ecological ApplicationsVolume 11, Issue 4 p. 1027-1045 Issues in Ecology — Technical Report WATER IN A CHANGING WORLD Robert B. Jackson, Robert B. Jackson Department of Biology and Nicholas School of the Environment, Duke University, Durham, North Carolina 27708 USA Address for correspondence: Department of Biology, Phytotron Building, Duke University, Durham, North Carolina 27708 USA. E-mail: [email protected]Search for more papers by this authorStephen R. Carpenter, Stephen R. Carpenter Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorClifford N. Dahm, Clifford N. Dahm Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131 USASearch for more papers by this authorDiane M. McKnight, Diane M. McKnight Institute for Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80309 USASearch for more papers by this authorRobert J. Naiman, Robert J. Naiman School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington 98195 USASearch for more papers by this authorSandra L. Postel, Sandra L. Postel Center for Global Water Policy, 107 Larkspur Drive, Amherst, Massachusetts 01002 USASearch for more papers by this authorSteven W. Running, Steven W. Running School of Forestry, University of Montana, Missoula, Montana 59812 USASearch for more papers by this author Robert B. Jackson, Robert B. Jackson Department of Biology and Nicholas School of the Environment, Duke University, Durham, North Carolina 27708 USA Address for correspondence: Department of Biology, Phytotron Building, Duke University, Durham, North Carolina 27708 USA. E-mail: [email protected]Search for more papers by this authorStephen R. Carpenter, Stephen R. Carpenter Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorClifford N. Dahm, Clifford N. Dahm Department of Biology, University of New Mexico, Albuquerque, New Mexico 87131 USASearch for more papers by this authorDiane M. McKnight, Diane M. McKnight Institute for Arctic and Alpine Research, University of Colorado, Boulder, Colorado 80309 USASearch for more papers by this authorRobert J. Naiman, Robert J. Naiman School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington 98195 USASearch for more papers by this authorSandra L. Postel, Sandra L. Postel Center for Global Water Policy, 107 Larkspur Drive, Amherst, Massachusetts 01002 USASearch for more papers by this authorSteven W. Running, Steven W. Running School of Forestry, University of Montana, Missoula, Montana 59812 USASearch for more papers by this author First published: 01 August 2001 https://doi.org/10.1890/1051-0761(2001)011[1027:WIACW]2.0.CO;2Citations: 594 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract Renewable fresh water comprises a tiny fraction of the global water pool but is the foundation for life in terrestrial and freshwater ecosystems. The benefits to humans of renewable fresh water include water for drinking, irrigation, and industrial uses, for production of fish and waterfowl, and for such instream uses as recreation, transportation, and waste disposal. In the coming century, climate change and a growing imbalance among freshwater supply, consumption, and population will alter the water cycle dramatically. Many regions of the world are already limited by the amount and quality of available water. In the next 30 yr alone, accessible runoff is unlikely to increase more than 10%, but the earth's population is projected to rise by approximately one-third. Unless the efficiency of water use rises, this imbalance will reduce freshwater ecosystem services, increase the number of aquatic species facing extinction, and further fragment wetlands, rivers, deltas, and estuaries. Based on the scientific evidence currently available, we conclude that: (1) over half of accessible freshwater runoff globally is already appropriated for human use; (2) more than 1 × 109 people currently lack access to clean drinking water and almost 3 × 109 people lack basic sanitation services; (3) because the human population will grow faster than increases in the amount of accessible fresh water, per capita availability of fresh water will decrease in the coming century; (4) climate change will cause a general intensification of the earth's hydrological cycle in the next 100 yr, with generally increased precipitation, evapotranspiration, and occurrence of storms, and significant changes in biogeochemical processes influencing water quality; (5) at least 90% of total water discharge from U.S. rivers is strongly affected by channel fragmentation from dams, reservoirs, interbasin diversions, and irrigation; and (6) globally, 20% of freshwater fish species are threatened or extinct, and freshwater species make up 47% of all animals federally endangered in the United States. The growing demands on freshwater resources create an urgent need to link research with improved water management. Better monitoring, assessment, and forecasting of water resources will help to allocate water more efficiently among competing needs. Currently in the United States, at least six federal departments and 20 agencies share responsibilities for various aspects of the hydrologic cycle. Coordination by a single panel with members drawn from each department, or by a central agency, would acknowledge the diverse pressures on freshwater systems and could lead to the development of a well-coordinated national plan. Literature Cited Allan, R. J., and M. R. Haylock . 1993. Circulation features associated with the winter rainfall decrease in southwestern Australia. Journal of Climate 6: 1356–1367. 10.1175/1520-0442(1993)006<1356:CFAWTW>2.0.CO;2 Web of Science®Google Scholar Anonymous. 1990. Natural resources management strategy for the Murray-Darling Basin. Murray-Darling Ministerial Council, Canberra, Australia. Google Scholar Bakun, A. 1990. Global climate change and intensification of coastal ocean upwelling. Science 247: 198–201. 10.1126/science.247.4939.198 CASPubMedWeb of Science®Google Scholar Band, L. E. 1993. Effect of land surface parameterization on forest water and carbon budgets. Journal of Hydrology 150: 749–772. 10.1016/0022-1694(93)90134-U Web of Science®Google Scholar Baron, J. S., M. D. Hartman, T. G. F. Kittel, L. E. Band, D. S. Ojima, and R. B. Lammers . 1998. Effects of land cover, water redistribution, and temperature on ecosystem processes in the South Platte Basin. Ecological Applications 8: 1037–1051. 10.1890/1051-0761(1998)008[1037:EOLCWR]2.0.CO;2 Web of Science®Google Scholar Benson, N. G. 1953. The importance of groundwater to trout populations in the Pigeon River, Michigan. Transactions of the North American Wildlife Conference 18: 260–281. Google Scholar Bertoldi, G. L. 1992. Subsidence and consolidation in alluvial aquifer systems. Pages 62–74 in Proceedings of the 18th Biennial Conference on Groundwater. U.S. Geological Survey, Washington, D.C., USA. Google Scholar Blackmore, D. J. 1999. The Murray-Darling Basin cap on diversions—policy and practice for the new millennium. National Water (June) 1–12. Web of Science®Google Scholar Born, S. M., K. D. Genskow, T. L. Filbert, N. Hernandez-Mora, M. L. Keefer, and K. A. White . 1998. Socioeconomic and institutional dimensions of dam removals: the Wisconsin experience. Environmental Management 22: 359–370. 10.1007/s002679900111 CASPubMedWeb of Science®Google Scholar Bosch, J. M., and J. D. Hewlett . 1982. A review of catchment experiments to determine the effect of vegetation change on water yield and evapotranspiration. Journal of Hydrology 55: 3–23. 10.1016/0022-1694(82)90117-2 Web of Science®Google Scholar Bowles, D. E., and T. L. Arsuffi . 1993. Karst aquatic ecosystems of the Edwards Plateau region of central Texas, USA: a consideration of their importance, threats to their existence, and efforts for their conservation. Aquatic Conservation: Marine and Freshwater Ecosystems 3: 317–329. 10.1002/aqc.3270030406 Web of Science®Google Scholar Bradley, R. S., H. F. Diaz, J. K. Eischeid, P. D. Jones, P. M. Kelly, and C. M. Goodness . 1987. Precipitation fluctuations over northern hemisphere land areas since the mid-19th century. Science 237: 171–175. 10.1126/science.237.4811.171 CASPubMedWeb of Science®Google Scholar Brown, D. S., B. L. Petri, and G. M. Nalley . 1992. Compilation of hydrologic data for the Edwards Aquifer, San Antonio area, Texas, 1991, with 1934–1991 summary. Bulletin 51, Edwards Underground Water District, San Antonio, Texas, USA. Google Scholar Brunke, M., and T. Gonser . 1997. The ecological significance of exchange processes between rivers and groundwater. Freshwater Biology 37: 1–33. 10.1046/j.1365-2427.1997.00143.x Web of Science®Google Scholar Carpenter, S. R., N. F. Caraco, D. L. Correll, R. W. Howarth, A. N. Sharpley, and V. H. Smith . 1998. Nonpoint pollution of surface waters with phosphorus and nitrogen. Ecological Applications 8: 559–568. 10.1890/1051-0761(1998)008[0559:NPOSWW]2.0.CO;2 Web of Science®Google Scholar Chahine, M. T. 1992. The hydrological cycle and its influence on climate. Nature 359: 373–380. 10.1038/359373a0 Web of Science®Google Scholar Chase, T. N., R. A. Pielke Sr., T. G. F. Kittel, J. S. Baron, and T. J. Stohlgren . 1999. Potential impacts on Colorado Rocky Mountain weather due to land use changes on the adjacent Great Plains. Journal of Geophysical Research 104: 16673–16690. 10.1029/1999JD900118 Web of Science®Google Scholar Chen, X., and Y. Zong . 1999. Major impacts of sea-level rise on agriculture in the Yangtze delta area around Shanghai. Applied Geography 19: 69–84. 10.1016/S0143-6228(98)00035-6 Web of Science®Google Scholar Chichilnisky, G., and G. Heal . 1998. Economic returns from the biosphere. Nature 391: 629–630. 10.1038/35481 CASWeb of Science®Google Scholar Christensen, N. L. et al. 1996. The report of the Ecological Society of America Committee on the Scientific Basis for Ecosystem Management. Ecological Applications 6: 665–691. 10.2307/2269460 Web of Science®Google Scholar Covich, A. 1993. Water and ecosystems. Pages 40–55 in P. H. Gleick, editor. Water in crisis. Oxford University Press, New York, New York, USA. Google Scholar Coyle, K. J. 1993. The new advocacy for aquatic species conservation. Journal of the North American Benthological Society 12: 185–188. 10.2307/1467349 Web of Science®Google Scholar Crawford, C. S., A. C. Culley, R. Leutheuser, M. S. Sifuentes, L. H. White, and J. P. Wilber . 1993. Middle Rio Grande Ecosystem: Bosque Biological Management Plan. U.S. Fish and Wildlife Service, District 2, Albuquerque, New Mexico, USA. Google Scholar Crowley, T. J. 2000. Causes of climate change over the past 1000 years. Science 287: 270–277. 10.1126/science.289.5477.270 Web of Science®Google Scholar Czaya, E. 1981. Rivers of the world. Van Nostrand Reinhold, New York, New York, USA. Google Scholar Dahm, C. N., K. W. Cummins, H. M. Valett, and R. L. Coleman . 1995. An ecosystem view of the restoration of the Kissimmee River. Restoration Ecology 3: 225–238. 10.1111/j.1526-100X.1995.tb00172.x Web of Science®Google Scholar Dahm, C. N., N. B. Grimm, P. Marmonier, H. M. Valett, and P. Vervier . 1998. Nutrient dynamics at the interface between surface waters and groundwaters. Freshwater Biology 40: 427–451. 10.1046/j.1365-2427.1998.00367.x Web of Science®Google Scholar Dellapenna, J. W. 1999. Adapting the law of water management to global climate change and other hydropolitical stresses. Journal of the American Water Resources Association 35: 1301–1326. 10.1111/j.1752-1688.1999.tb04217.x Web of Science®Google Scholar Dickinson, R. E. 1991. Global change and terrestrial hydrology—a review. Tellus A 43: 176–181. 10.1034/j.1600-0889.1991.t01-1-00015.x Web of Science®Google Scholar Dobson, A. P., J. P. Rodriguez, W. M. Roberts, and D. S. Wilcove . 1997. Geographic distribution of endangered species in the United States. Science 275: 550–553. 10.1126/science.275.5299.550 CASPubMedWeb of Science®Google Scholar Doney, S. 1999. Major challenges confronting marine biogeochemical modeling. Global Biogeochemical Cycles 13: 705–714. 10.1029/1999GB900039 CASWeb of Science®Google Scholar Dudgeon, D. 2000. Large-scale hydrological changes in tropical Asia: prospects for riverine biodiversity. BioScience 50: 793–806. 10.1641/0006-3568(2000)050[0793:LSHCIT]2.0.CO;2 Web of Science®Google Scholar Dynesius, M., and C. Nilsson . 1994. Fragmentation and flow regulation of river systems in the northern third of the world. Science 266: 753–762. 10.1126/science.266.5186.753 CASPubMedWeb of Science®Google Scholar Field, C. B., R. B. Jackson, and H. A. Mooney . 1995. Stomatal responses to increased CO2: implications from the plant to the global scale. Plant Cell Environment 18: 1214–1225. 10.1111/j.1365-3040.1995.tb00630.x Web of Science®Google Scholar Firth, P. L. 1998. Fresh water: perspectives on the integration of research, education, and decision making. Ecological Applications 8: 601–609. 10.1890/1051-0761(1998)008[0601:FWPOTI]2.0.CO;2 Web of Science®Google Scholar Flather, C. H., M. S. Knowles, and I. A. Kendall . 1998. Threatened and endangered species geography. BioScience 48: 365–376. 10.2307/1313375 Web of Science®Google Scholar Ford, D. C., and P. W. Williams . 1989. Karst geomorphology and hydrology. Unwin Hyman, London, UK. Google Scholar Gates, D. M. 1993. Climate change and its biological consequences. Sinauer Associates, Sunderland, Massachusetts, USA. Google Scholar Gleick, P. H. 1998a. Water in crisis: paths to sustainable water use. Ecological Applications 8: 571–579. 10.1890/1051-0761(1998)008[0571:WICPTS]2.0.CO;2 Web of Science®Google Scholar Gleick, P. H. 1998b. The world's water 1998–1999. Island Press, Washington, D. C., USA. Google Scholar Gleick, P. H. 2000. The world's water 2000–2001. Island Press, Washington, D. C., USA. Google Scholar Gornitz, V. 1995. Sea-level rise: a review of recent past and near-future trends. Earth Surface Processes and Landforms 20: 7–20. 10.1002/esp.3290200103 Web of Science®Google Scholar Greenwood, E. A. N. 1992. Deforestation, revegetation, water balance, and climate: an optimistic path through the plausible, impracticable, and the controversial. Advances in Bioclimatology 1: 89–154. 10.1007/978-3-642-58136-6_4 Google Scholar Groisman, P. Y., V. V. Koknaeva, T. A. Belokrylova, and T. R. Karl . 1991. Overcoming biases of precipitation measurement: a history of the USSR experience. Bulletin of the American Meteorological Society 72: 1725–1733. 10.1175/1520-0477(1991)072<1725:OBOPMA>2.0.CO;2 Web of Science®Google Scholar Guildford, S. J., and R. E. Hecky . 2000. Total nitrogen, total phosphorus, and nutrient limitation in lakes and oceans: Is there a common relationship? Limnology and Oceanography 45: 1213–1223. 10.4319/lo.2000.45.6.1213 CASWeb of Science®Google Scholar Hartman, M. D., J. S. Baron, R. B. Lammers, D. W. Cline, L. E. Band, G. E. Liston, and C. Tague . 1999. Simulations of snow distribution and hydrology in a mountain basin. Water Resources Research 35: 1587–1603. 10.1029/1998WR900096 Web of Science®Google Scholar Harwell, M. A. 1998. Science and environmental decision making in south Florida. Ecological Applications 8: 580–590. 10.1890/1051-0761(1998)008[0580:SAEDMI]2.0.CO;2 Web of Science®Google Scholar Hibbert, A. R. 1983. Water yield improvement potential by vegetation management on western rangelands. Water Resources Bulletin 19: 375–381. 10.1111/j.1752-1688.1983.tb04594.x Web of Science®Google Scholar Hilborn, R., and C. Walters . 1992. Quantitative fisheries stock assessment. Chapman and Hall, London, UK. Google Scholar Hoffmann, W. A., and R. B. Jackson . 2000. Vegetation–climate feedbacks in the conversion of tropical savanna to grassland. Journal of Climate 13: 1593–1602. 10.1175/1520-0442(2000)013<1593:VCFITC>2.0.CO;2 Web of Science®Google Scholar Holmes, R. M. 2000. The importance of ground water to stream ecosystem function. Pages 137–148 in J. B. Jones and P. J. Mulholland, editors. Streams and ground water. Academic Press, San Diego, California, USA. Google Scholar Hornberger, G. M., J. P. Raffensperger, P. L. Wiberg, and K. N. Eshleman . 1998. Elements of physical hydrology. Johns Hopkins Press, Baltimore, Maryland, USA. Google Scholar Hornberger, G. M. et al. (Water Cycle Study Group) 2001. A plan for a new science initiative on the global water cycle. Report of the U.S. Global Change Research Program, UCAR, Boulder, Colorado, USA. In press. Google Scholar Intergovernmental Panel on Climate Change (IPCC). 1996. Climate change 1995: The science of climate change. Cambridge University Press, Cambridge, UK. Google Scholar Jackson, R. B. et al. 2000. Belowground consequences of vegetation change and their treatment in models. Ecological Applications 10: 470–483. 10.1890/1051-0761(2000)010[0470:BCOVCA]2.0.CO;2 Web of Science®Google Scholar Johnson, B. L. 1999. Introduction to the special feature: adaptive management—scientifically sound, socially challenged? Conservation Ecology 3 1 10 [Online: 〈http://www.consecol.org/vol3/iss1/art10〉]. 10.5751/ES-00094-030110 Google Scholar Jones, J. B., and P. J. Mulholland . editors. 2000. Streams and ground waters. Academic Press, San Diego, California, USA. Google Scholar Kim, H., J. F. Hemond, L. R. Krumholz, and B. A. Cohen . 1995. In-situ biodegradation of toluene in a contaminated stream. 1. Field studies. Environmental Science and Technology 29: 108–116. 10.1021/es00001a014 CASPubMedWeb of Science®Google Scholar Kindler, J. 1998. Linking ecological and development objectives: trade-offs and imperatives. Ecological Applications 8: 591–600. 10.1890/1051-0761(1998)008[0591:LEADOT]2.0.CO;2 Web of Science®Google Scholar Klein, R. J. T., and R. J. Nicholls . 1999. Assessment of coastal vulnerability to climate change. Ambio 28: 182–187. Web of Science®Google Scholar Knox, J. C. 1993. Large increases in flood magnitude in response to modest changes in climate. Nature 361: 430–432. 10.1038/361430a0 Web of Science®Google Scholar Koebel, J. W. Jr. 1995. An historical perspective on the Kissimmee River restoration project. Restoration Ecology 3: 149–159. 10.1111/j.1526-100X.1995.tb00167.x Web of Science®Google Scholar Kolar, C. S., and D. M. Lodge . 2000. Freshwater nonindigenous species: interactions with other global changes. Pages 3–30 in H. H. Mooney and R. Hobbs, editors. Invasive species in a changing world. Island Press, Washington, D.C., USA. Google Scholar Kromm, D. E., and S. E. White . 1990. Adoption of water-saving practices by irrigators in the high plains. Water Resources Bulletin 26: 999–1012. 10.1111/j.1752-1688.1990.tb01435.x Web of Science®Google Scholar Lathrop, R. C., S. R. Carpenter, C. A. Stow, P. A. Soranno, and J. C. Panuska . 1998. Phosphorus loading reductions needed to control blue-green algae blooms in Lake Mendota. Canadian Journal of Fisheries and Aquatic Sciences 55: 1169–1178. 10.1139/f97-317 CASWeb of Science®Google Scholar Laws, E. A. 1993. Aquatic pollution: an introductory text. Second edition. Wiley, New York, New York, USA. Google Scholar Lean, J., and D. A. Warrilow . 1989. Simulation of the regional climatic impact of Amazon deforestation. Nature 342: 411–413. 10.1038/342411a0 Web of Science®Google Scholar Lettenmaier, D., E. F. Wood, and J. R. Wallis . 1994. Hydroclimatological trends in the continental United States, 1948–1988. Journal of Climate 7: 586–607. 10.1175/1520-0442(1994)007<0586:HCTITC>2.0.CO;2 Web of Science®Google Scholar Lins, H. F., and P. J. Michaels . 1994. Increasing streamflow in the United States. EOS 75: 281–286. 10.1029/94EO00947 Google Scholar Lipson, D. A., S. K. Schmidt, and R. K. Monson . 1999. Seasonal dynamics in the utilization of organic nitrogen by soil microorganisms in the alpine ecosystem. Ecology 80: 1623–1631. 10.1890/0012-9658(1999)080[1623:LBMPDA]2.0.CO;2 Web of Science®Google Scholar Loaiciga, H. A., J. B. Valdes, R. Vogel, J. Garvey, and H. Schwarz . 1996. Global warming and the hydrologic cycle. Journal of Hydrology 174: 83–127. 10.1016/0022-1694(95)02753-X Web of Science®Google Scholar Lubchenco, J. 1998. Entering the century of the environment: a new social contract for science. Science 279: 491–497. 10.1126/science.279.5350.491 CASWeb of Science®Google Scholar L'Vovich, M. I. 1973. The global water balance. EOS 54: 28–42. 10.1029/EO054i001p00028 Google Scholar L'Vovich, M. I., G. F. White, A. V. Belyaev, J. Kindler, N. I. Koronkevic, T. R. Lee, and G. V. Voropaev . 1990. Use and transformation of terrestrial water systems. Pages 235–252 in B. L. Turner II, W. C. Clark, R. W. Kates, J. F. Richards, J. T. Mathews, and W. B. Meyer, editors. The earth as transformed by human action. Cambridge University Press, Cambridge, UK. Google Scholar McCully, P. 1996. Silenced rivers: the ecology and politics of large dams. Zed Books, London, UK. Google Scholar Meyer, J. L., M. J. Sale, P. J. Mulholland, and N. L. Poff . 1999. Impacts of climate change on aquatic ecosystem functioning and health. Journal of the American Water Resources Association 35: 1373–1386. 10.1111/j.1752-1688.1999.tb04222.x Web of Science®Google Scholar Michener, W. K., E. R. Blood, K. L. Bildstein, M. M. Brinson, and L. R. Gardner . 1997. Climate change, hurricanes and tropical storms, and rising sea level in coastal wetlands. Ecological Applications 7: 770–801. 10.1890/1051-0761(1997)007[0770:CCHATS]2.0.CO;2 Web of Science®Google Scholar Middle Rio Grande Water Assembly. 1999. Middle Rio Grande water budget (where water comes from, and goes, and how much): averages for 1972–1997. Middle Rio Grande Council of Governments of New Mexico, Albuquerque, New Mexico, USA. Google Scholar Miles, E. L., A. K. Snover, A. F. Hamlet, B. Callahan, and D. Fluharty . 2000. Pacific Northwest regional assessment: the impacts of climate variability and climate change on the water resources of the Columbia River Basin. Journal of the American Water Resources Association 36: 399–420. 10.1111/j.1752-1688.2000.tb04277.x Web of Science®Google Scholar Miller, J. R., and G. L. Russell . 1992. The impact of global warming on river runoff. Journal of Geophysical Research 97: 2757–2764. 10.1029/91JD01700 Web of Science®Google Scholar Mitchell, J. F. B. 1989. The greenhouse effect and climate. Reviews of Geophysics 27: 115–139. 10.1029/RG027i001p00115 Web of Science®Google Scholar Molles, M. C. Jr., C. S. Crawford, L. M. Ellis, H. M. Valett, and C. N. Dahm . 1998. Managed flooding for riparian ecosystem restoration. BioScience 48: 749–756. 10.2307/1313337 Web of Science®Google Scholar Moyle, P. B., and R. A. Leidy . 1992. Loss of biodiversity in aquatic ecosystems: evidence from fish faunas. Pages 128– 169 in P. L. Fielder and S. A. Jain, editors. Conservation biology: the theory and practice of nature conservation, preservation and management. Chapman and Hall, New York, New York, USA. Google Scholar Moyle, P. B., and R. M. Yoshiyama . 1994. Protection of aquatic biodiversity in California: a 5-tiered approach. Fisheries 19: 6–18. 10.1577/1548-8446(1994)019<0006:POABIC>2.0.CO;2 Web of Science®Google Scholar Mulholland, P. J., G. R. Best, C. C. Coutant, G. M. Hornberger, J. L. Meyer, P. J. Robinson, J. R. Stenberg, R. E. Turner, F. VeraHerrera, and R. G. Wetzel . 1997. Effects of climate change on freshwater ecosystems of the south-eastern United States and the Gulf Coast of Mexico. Hydrological Processes 11: 949–970. 10.1002/(SICI)1099-1085(19970630)11:8<949::AID-HYP513>3.0.CO;2-G Web of Science®Google Scholar Mulrennan, M. E., and C. D. Woodroffe . 1998. Saltwater intrusion into the coastal plains of the Lower Mary River, Northern Territory, Australia. Journal of Environmental Management 54: 169–188. 10.1006/jema.1998.0229 Web of Science®Google Scholar Murdoch, P. S., J. S. Baron, and T. L. Miller . 2000. Potential effects of climate change on surface-water quality in North America. Journal of the American Water Resources Association 36: 347–366. 10.1111/j.1752-1688.2000.tb04273.x CASWeb of Science®Google Scholar Naiman, R. J., J. J. Magnuson, and P. L. Firth . 1998. Integrating cultural, economic, and environmental requirements for fresh water. Ecological Applications 8: 569–570. 10.1890/1051-0761(1998)008[0569:ICEAER]2.0.CO;2 Web of Science®Google Scholar Naiman, R. J., J. J. Magnuson, D. M. McKnight, and J. A. Stanford . editors. 1995. The freshwater imperative: a research agenda. Island Press, Washington, D.C., USA. Google Scholar Naiman, R. J., and M. G. Turner . 2000. A future perspective on North America's freshwater ecosystems: trends, consequences, challenges, and opportunities. Ecological Applications 10: 958–970. 10.1890/1051-0761(2000)010[0958:AFPONA]2.0.CO;2 Web of Science®Google Scholar National Environmental Engineering Research Institute. 1997. Water resources management in India: present status and solution paradigm. Unpublished document of the National Environmental Engineering Research Institute. Nagpur, India. Google Scholar National Research Council. 2000a. Clean coastal waters: understanding and reducing the effects of nutrient pollution. National Academy Press, Washington, D.C., USA. Google Scholar National Research Council. 2000b. Grand challenges in environmental sciences. National Academy Press, Washington, D.C., USA. Google Scholar National Resource Council. 1999. New strategies for America's watersheds. National Academy Press, Washington, D.C., USA. Google Scholar Neilson, R. P., and D. Marks . 1994. A global perspective of regional vegetation and hydrologic sensitivities from climatic change. Journal of Vegetation Science 5: 715–730. 10.2307/3235885 Web of Science®Google Scholar Nicholson, S. E. 1994. Recent rainfall fluctuations in Africa and their relationship to past conditions. Holocene 4: 121–131. 10.1177/095968369400400202 Google Scholar Office of Technology Assessment, U.S. Congress. 1993. Preparing for an uncertain climate. Volume I. OTA-O-567, Washington, D.C., USA. Google Scholar Oud, E., and T. Muir . 1997. Engineering and economic aspects of planning, design, construction and operation of large dam projects. In T. Dorcey, editor. Large dams: learning from the past, looking at the future. The World Conservation Union, Gland, Switzerland, and the World Bank, Washington, D.C., USA. Google Scholar Peterjohn, W. T., and D. L. Correll . 1984. Nutrient dynamics in an agricultural watershed: observations on the role of a riparian forest. Ecology 64: 1249–1265. Google Scholar Pielke, R. S. Sr., R. Avissar, M. Raupach, A. J. Dolman, X. Zeng, and A. S. Denning . 1998. Interactions between the atmosphere and terrestrial ecosystems: influence on weather and climate. Global Change Biology 4: 461–475. 10.1046/j.1365-2486.1998.t01-1-00176.x Web of Science®Google Scholar Postel, S. 1999. Pillar of sand: Can the irrigation miracle last? W. W. Norton, New York, New York, USA. Google Scholar Postel, S. 2000. Entering an era of water scarcity: the challenges ahead. Ecological Applications 10: 941–948. 10.1890/1051-0761(2000)010[0941:EAEOWS]2.0.CO;2 Web of Science®Google Scholar Postel, S., and S. Carpenter . 1997

Human actions—mining phosphorus (P) and transporting it in fertilizers, animal feeds, agricultural crops, and other products—are altering the global P cycle, causing P to accumulate in some of the world’s soil. Increasing P levels in the soil elevate the potential P runoff to aquatic ecosystems (Fluck et al. 1992, NRC 1993, USEPA 1996). Using a global budget approach, we estimate the increase in net P storage in terrestrial and freshwater ecosystems to be at least 75% greater than preindustrial levels of storage. We calculated an agricultural mass balance (budget), which indicated that a large portion of this P accumulation occurs in agricultural soils. Separate P budgets of the agricultural areas of developing and developed countries show that the rate of P accumulation is decreasing in developed nations but increasing in developing nations.

Ecosystem stewardship is an action-oriented framework intended to foster the social-ecological sustainability of a rapidly changing planet. Recent developments identify three strategies that make optimal use of current understanding in an environment of inevitable uncertainty and abrupt change: reducing the magnitude of, and exposure and sensitivity to, known stresses; focusing on proactive policies that shape change; and avoiding or escaping unsustainable social-ecological traps. As we discuss here, all social-ecological systems are vulnerable to recent and projected changes but have sources of adaptive capacity and resilience that can sustain ecosystem services and human well-being through active ecosystem stewardship.

As human populations increase and land-use intensifies, toxic and unsightly nuisance blooms of algae are becoming larger and more frequent in freshwater lakes. In most cases, the blooms are predominantly blue-green algae (Cyanobacteria), which are favored by low ratios of nitrogen to phosphorus. In the past half century, aquatic scientists have devoted much effort to understanding the causes of such blooms and how they can be prevented or reduced. Here we review the evidence, finding that numerous long-term studies of lake ecosystems in Europe and North America show that controlling algal blooms and other symptoms of eutrophication depends on reducing inputs of a single nutrient: phosphorus. In contrast, small-scale experiments of short duration, where nutrients are added rather than removed, often give spurious and confusing results that bear little relevance to solving the problem of cyanobacteria blooms in lakes.

Catastrophic ecological regime shifts may be announced in advance by statistical early warning signals such as slowing return rates from perturbation and rising variance. The theoretical background for these indicators is rich, but real-world tests are rare, especially for whole ecosystems. We tested the hypothesis that these statistics would be early warning signals for an experimentally induced regime shift in an aquatic food web. We gradually added top predators to a lake over 3 years to destabilize its food web. An adjacent lake was monitored simultaneously as a reference ecosystem. Warning signals of a regime shift were evident in the manipulated lake during reorganization of the food web more than a year before the food web transition was complete, corroborating theory for leading indicators of ecological regime shifts.

Surface freshwaters—lakes, reservoirs, and rivers—are among the most extensively altered ecosystems on Earth. Transformations include changes in the morphology of rivers and lakes, hydrology, biogeochemistry of nutrients and toxic substances, ecosystem metabolism and the storage of carbon (C), loss of native species, expansion of invasive species, and disease emergence. Drivers are climate change, hydrologic flow modification, land-use change, chemical inputs, aquatic invasive species, and harvest. Drivers and responses interact, and their relationships must be disentangled to understand the causes and consequences of change as well as the correctives for adverse change in any given watershed. Beyond its importance in terms of drinking water, freshwater supports human well-being in many ways related to food and fiber production, hydration of other ecosystems used by humans, dilution and degradation of pollutants, and cultural values. A natural capital framework can be used to assess freshwater ecosystem services, competing uses for freshwaters, and the processes that underpin the long-term maintenance of freshwaters. Upper limits for human consumption of freshwaters have been proposed, and consumptive use may approach these limits by the mid-century.

Abstract Regime shifts are substantial, long‐lasting reorganizations of complex systems, such as ecosystems. Large ecosystem changes such as eutrophication, shifts among vegetation types, degradation of coral reefs and regional climate change often come as surprises because we lack leading indicators for regime shifts. Increases in variability of ecosystems have been suggested to foreshadow ecological regime shifts. However, it may be difficult to discern variability due to impending regime shift from that of exogenous drivers that affect the ecosystem. We addressed this problem using a model of lake eutrophication. Lakes are subject to fluctuations in recycling associated with regime shifts, as well as fluctuating nutrient inputs. Despite the complications of noisy inputs, increasing variability of lake‐water phosphorus was discernible prior to the shift to eutrophic conditions. Simulations show that rising standard deviation (SD) could signal impending shifts about a decade in advance. The rising SD was detected by studying variability around predictions of a simple time‐series model, and did not depend on detailed knowledge of the actual ecosystem dynamics.

Research practice, funding agencies and global science organizations suggest that research aimed at addressing sustainability challenges is most effective when ‘co-produced’ by academics and non-academics. Co-production promises to address the complex nature of contemporary sustainability challenges better than more traditional scientific approaches. But definitions of knowledge co-production are diverse and often contradictory. We propose a set of four general principles that underlie high-quality knowledge co-production for sustainability research. Using these principles, we offer practical guidance on how to engage in meaningful co-productive practices, and how to evaluate their quality and success. Research addressing sustainability issues is more effective if ‘co-produced’ by academics and non-academics, but definitions of co-production vary. This Perspective presents four knowledge co-production principles for sustainability research and guides on how to engage in co-productive practices.

Eutrophication (the overenrichment of aquatic ecosystems with nutrients leading to algal blooms and anoxic events) is a persistent condition of surface waters and a widespread environmental problem. Some lakes have recovered after sources of nutrients were reduced. In others, recycling of phosphorus from sediments enriched by years of high nutrient inputs causes lakes to remain eutrophic even after external inputs of phosphorus are decreased. Slow flux of phosphorus from overfertilized soils may be even more important for maintaining eutrophication of lakes in agricultural regions. This type of eutrophication is not reversible unless there are substantial changes in soil management. Technologies for rapidly reducing phosphorus content of overenriched soils, or reducing erosion rates, are needed to improve water quality.

Many dynamical systems, including lakes, organisms, ocean circulation patterns, or financial markets, are now thought to have tipping points where critical transitions to a contrasting state can happen. Because critical transitions can occur unexpectedly and are difficult to manage, there is a need for methods that can be used to identify when a critical transition is approaching. Recent theory shows that we can identify the proximity of a system to a critical transition using a variety of so-called 'early warning signals', and successful empirical examples suggest a potential for practical applicability. However, while the range of proposed methods for predicting critical transitions is rapidly expanding, opinions on their practical use differ widely, and there is no comparative study that tests the limitations of the different methods to identify approaching critical transitions using time-series data. Here, we summarize a range of currently available early warning methods and apply them to two simulated time series that are typical of systems undergoing a critical transition. In addition to a methodological guide, our work offers a practical toolbox that may be used in a wide range of fields to help detect early warning signals of critical transitions in time series data.

EcologyVolume 72, Issue 2 p. 371-412 Article The Sustainable Biosphere Initiative: An Ecological Research Agenda: A Report from the Ecological Society of America Jane Lubchenco, Jane LubchencoSearch for more papers by this authorAnnette M. Olson, Annette M. OlsonSearch for more papers by this authorLinda B. Brubaker, Linda B. BrubakerSearch for more papers by this authorStephen R. Carpenter, Stephen R. CarpenterSearch for more papers by this authorMarjorie M. Holland, Marjorie M. HollandSearch for more papers by this authorStephen P. Hubbell, Stephen P. HubbellSearch for more papers by this authorSimon A. Levin, Simon A. LevinSearch for more papers by this authorJames A. MacMahon, James A. MacMahonSearch for more papers by this authorPamela A. Matson, Pamela A. MatsonSearch for more papers by this authorJerry M. Melillo, Jerry M. MelilloSearch for more papers by this authorHarold A. Mooney, Harold A. MooneySearch for more papers by this authorCharles H. Peterson, Charles H. PetersonSearch for more papers by this authorH. Ronald Pulliam, H. Ronald PulliamSearch for more papers by this authorLeslie A. Real, Leslie A. RealSearch for more papers by this authorPhilip J. Regal, Philip J. RegalSearch for more papers by this authorPaul G. Risser, Paul G. RisserSearch for more papers by this author Jane Lubchenco, Jane LubchencoSearch for more papers by this authorAnnette M. Olson, Annette M. OlsonSearch for more papers by this authorLinda B. Brubaker, Linda B. BrubakerSearch for more papers by this authorStephen R. Carpenter, Stephen R. CarpenterSearch for more papers by this authorMarjorie M. Holland, Marjorie M. HollandSearch for more papers by this authorStephen P. Hubbell, Stephen P. HubbellSearch for more papers by this authorSimon A. Levin, Simon A. LevinSearch for more papers by this authorJames A. MacMahon, James A. MacMahonSearch for more papers by this authorPamela A. Matson, Pamela A. MatsonSearch for more papers by this authorJerry M. Melillo, Jerry M. MelilloSearch for more papers by this authorHarold A. Mooney, Harold A. MooneySearch for more papers by this authorCharles H. Peterson, Charles H. PetersonSearch for more papers by this authorH. Ronald Pulliam, H. Ronald PulliamSearch for more papers by this authorLeslie A. Real, Leslie A. RealSearch for more papers by this authorPhilip J. Regal, Philip J. RegalSearch for more papers by this authorPaul G. Risser, Paul G. RisserSearch for more papers by this author First published: 01 April 1991 https://doi.org/10.2307/2937183Citations: 447AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume72, Issue2April 1991Pages 371-412 RelatedInformation

Ecological regime shifts are large, abrupt, long-lasting changes in ecosystems that often have considerable impacts on human economies and societies. Avoiding unintentional regime shifts is widely regarded as desirable, but prediction of ecological regime shifts is notoriously difficult. Recent research indicates that changes in ecological time series (e.g., increased variability and autocorrelation) could potentially serve as early warning indicators of impending shifts. A critical question, however, is whether such indicators provide sufficient warning to adapt management to avert regime shifts. We examine this question using a fisheries model, with regime shifts driven by angling (amenable to rapid reduction) or shoreline development (only gradual restoration is possible). The model represents key features of a broad class of ecological regime shifts. We find that if drivers can only be manipulated gradually management action is needed substantially before a regime shift to avert it; if drivers can be rapidly altered aversive action may be delayed until a shift is underway. Large increases in the indicators only occur once a regime shift is initiated, often too late for management to avert a shift. To improve usefulness in averting regime shifts, we suggest that research focus on defining critical indicator levels rather than detecting change in the indicators. Ideally, critical indicator levels should be related to switches in ecosystem attractors; we present a new spectral density ratio indicator to this end. Averting ecological regime shifts is also dependent on developing policy processes that enable society to respond more rapidly to information about impending regime shifts.

It has been suggested that differences in body size between consumer and resource species may have important implications for interaction strengths, population dynamics, and eventually food web structure, function, and evolution. Still, the general distribution of consumer-'resource body-size ratios in real ecosystems, and whether they vary systematically among habitats or broad taxonomic groups, is poorly understood. Using a unique global database on consumer and resource body sizes, we show that the mean body-size ratios of aquatic herbivorous and detritivorous consumers are several orders of magnitude larger than those of carnivorous predators. Carnivorous predator-prey body-size ratios vary across different habitats and predator and prey types (invertebrates, ectotherm, and endotherm vertebrates). Predator-prey body-size ratios are on average significantly higher (1) in freshwater habitats than in marine or terrestrial habitats, (2) for vertebrate than for invertebrate predators, and (3) for invertebrate than for ectotherm vertebrate prey. If recent studies that relate body-size ratios to interaction strengths are general, our results suggest that mean consumer-resource interaction strengths may vary systematically across different habitat categories and consumer types.

The Midwest floods of 2008 added more than just water to the region's lakes, reservoirs, and rivers. Runoff from farms and towns carries a heavy load of silt, nutrients, and other pollutants. The nutrients trigger blooms of algae, which taint drinking water. Death and decay of the algae depletes oxygen, kills fish and bottom-dwelling animals, and thereby creates “dead zones” in the body of water. The syndrome of excessive nutrients, noxious algae, foul water, and dead zones—which ecologists call eutrophication—is depressingly familiar to those who depend on water from rich agricultural regions.

EcologyVolume 77, Issue 3 p. 677-680 Article Microcosm Experiments have Limited Relevance for Community and Ecosystem Ecology Stephen R. Carpenter, Stephen R. CarpenterSearch for more papers by this author Stephen R. Carpenter, Stephen R. CarpenterSearch for more papers by this author First published: 01 April 1996 https://doi.org/10.2307/2265490Citations: 464AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume77, Issue3April 1996Pages 677-680 RelatedInformation

Measuring the numerical abundance and average body size of individuals of each species in an ecological community's food web reveals new patterns and illuminates old ones. This approach is illustrated using data from the pelagic community of a small lake: Tuesday Lake, Michigan, United States. Body mass varies almost 12 orders of magnitude. Numerical abundance varies almost 10 orders of magnitude. Biomass abundance (average body mass times numerical abundance) varies only 5 orders of magnitude. A new food web graph, which plots species and trophic links in the plane spanned by body mass and numerical abundance, illustrates the nearly inverse relationship between body mass and numerical abundance, as well as the pattern of energy flow in the community. Species with small average body mass occur low in the food web of Tuesday Lake and are numerically abundant. Larger-bodied species occur higher in the food web and are numerically rarer. Average body size explains more of the variation in numerical abundance than does trophic height. The trivariate description of an ecological community by using the food web, average body sizes, and numerical abundance includes many well studied bivariate and univariate relationships based on subsets of these three variables. We are not aware of any single community for which all of these relationships have been analyzed simultaneously. Our approach demonstrates the connectedness of ecological patterns traditionally treated as independent. Moreover, knowing the food web gives new insight into the disputed form of the allometric relationship between body mass and abundance.

We review and synthesize information available in the literature on sediment interactions with submersed macrophyte growth and community dynamics. Sources of particular nutrients for uptake by submersed macrophytes are critically evaluated. Sediment physical and chemical properties are considered as a product of macrophyte growth as well as potential delimiters of growth. Aspects of macrophyte nutrition that influence littoral nutrient dynamics and macrophyte community composition are highlighted, with attention to factors affecting sediment nutrient availability. Interactive effects of sediment nutrient depletion, sedimentation, bioturbation, and microbial activity on macrophyte growth are emphasized. Major linkages and feedbacks between aquatic macrophytes and sediment properties are considered in terms of elemental exchanges and responses at the ecosystem level. Changes in macrophyte community composition during lake aging, or over relatively shorter time periods, are suggested to occur partially in response to altered sediment properties.

The global reach of human activities affects all natural ecosystems, so that the environment is best viewed as a social–ecological system. Consequently, a more integrative approach to environmental science, one that bridges the biophysical and social domains, is sorely needed. Although models and frameworks for social–ecological systems exist, few are explicitly designed to guide a long‐term interdisciplinary research program. Here, we present an iterative framework, “Press–Pulse Dynamics” (PPD), that integrates the biophysical and social sciences through an understanding of how human behaviors affect “press” and “pulse” dynamics and ecosystem processes. Such dynamics and processes, in turn, influence ecosystem services –thereby altering human behaviors and initiating feedbacks that impact the original dynamics and processes. We believe that research guided by the PPD framework will lead to a more thorough understanding of social–ecological systems and generate the knowledge needed to address pervasive environmental problems.

Policies may influence large-scale behavioral tipping

The research community needs to develop analytical tools for projecting future trends and evaluating the success of interventions as well as indicators to monitor biological, physical, and social changes.

Ecological MonographsVolume 71, Issue 2 p. 163-186 Article TROPHIC CASCADES, NUTRIENTS, AND LAKE PRODUCTIVITY: WHOLE-LAKE EXPERIMENTS Stephen R. Carpenter, Stephen R. Carpenter Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USA Corresponding author. E-mail: [email protected]Search for more papers by this authorJonathan J. Cole, Jonathan J. Cole Institute of Ecosystem Studies, Millbrook, New York 12545 USASearch for more papers by this authorJames R. Hodgson, James R. Hodgson Department of Biology, Saint Norbert College, DePere, Wisconsin 54115 USASearch for more papers by this authorJames F. Kitchell, James F. Kitchell Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorMichael L. Pace, Michael L. Pace Institute of Ecosystem Studies, Millbrook, New York 12545 USASearch for more papers by this authorDarren Bade, Darren Bade Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorKathryn L. Cottingham, Kathryn L. Cottingham Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755 USASearch for more papers by this authorTimothy E. Essington, Timothy E. Essington Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorJeffrey N. Houser, Jeffrey N. Houser Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorDaniel E. Schindler, Daniel E. Schindler Department of Zoology, University of Washington, Seattle, Washington 98195 USASearch for more papers by this author Stephen R. Carpenter, Stephen R. Carpenter Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USA Corresponding author. E-mail: [email protected]Search for more papers by this authorJonathan J. Cole, Jonathan J. Cole Institute of Ecosystem Studies, Millbrook, New York 12545 USASearch for more papers by this authorJames R. Hodgson, James R. Hodgson Department of Biology, Saint Norbert College, DePere, Wisconsin 54115 USASearch for more papers by this authorJames F. Kitchell, James F. Kitchell Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorMichael L. Pace, Michael L. Pace Institute of Ecosystem Studies, Millbrook, New York 12545 USASearch for more papers by this authorDarren Bade, Darren Bade Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorKathryn L. Cottingham, Kathryn L. Cottingham Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755 USASearch for more papers by this authorTimothy E. Essington, Timothy E. Essington Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorJeffrey N. Houser, Jeffrey N. Houser Center for Limnology, University of Wisconsin, Madison, Wisconsin 53706 USASearch for more papers by this authorDaniel E. Schindler, Daniel E. Schindler Department of Zoology, University of Washington, Seattle, Washington 98195 USASearch for more papers by this author First published: 01 May 2001 https://doi.org/10.1890/0012-9615(2001)071[0163:TCNALP]2.0.CO;2Citations: 366 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinkedInRedditWechat Abstract Responses of zooplankton, pelagic primary producers, planktonic bacteria, and CO2 exchange with the atmosphere were measured in four lakes with contrasting food webs under a range of nutrient enrichments during a seven-year period. Prior to enrichment, food webs were manipulated to create contrasts between piscivore dominance and planktivore dominance. Nutrient enrichments of inorganic nitrogen and phosphorus exhibited ratios of N:P > 17:1, by atoms, to maintain P limitation. An unmanipulated reference lake, Paul Lake, revealed baseline variability but showed no trends that could confound the interpretation of changes in the nearby manipulated lakes. Herbivorous zooplankton of West Long Lake (piscivorous fishes) were large-bodied Daphnia spp., in contrast to the small-bodied grazers that predominated in Peter Lake (planktivorous fishes). At comparable levels of nutrient enrichment, Peter Lake's areal chlorophyll and areal primary production rates exceeded those of West Long Lake by factors of approximately three and six, respectively. Grazers suppressed pelagic primary producers in West Long Lake, relative to Peter Lake, even when nutrient input rates were so high that soluble reactive phosphorus accumulated in the epilimnions of both lakes during summer. Peter Lake also had higher bacterial production (but not biomass) than West Long Lake. Hydrologic changes that accompanied manipulation of East Long Lake caused concentrations of colored dissolved organic carbon to increase, leading to considerable variability in fish and zooplankton populations. Both trophic cascades and water color appeared to inhibit the response of primary producers to nutrients in East Long Lake. Carbon dioxide was discharged to the atmosphere by Paul Lake in all years and by the other lakes prior to nutrient addition. During nutrient addition, only Peter Lake consistently absorbed CO2 from the atmosphere, due to high rates of carbon fixation by primary producers. In contrast, CO2 concentrations of West Long Lake shifted to near-atmospheric levels, and net fluxes were near zero, while East Long Lake continued to discharge CO2 to the atmosphere. Literature Cited Aiken, L. S., and S. G. West . 1991. Multiple regression: testing and interpreting interactions. Sage Publications, Newbury Park, California, USA. Bade, D., J. Houser, and S. Scanga . 1998. Methods of the Cascading Trophic Interactions Project. Fifth edition. Center for Limnology, University of Wisconsin–Madison, Wisconsin, USA. Benndorf, J. 1987. Food web manipulation without nutrient control: a useful strategy in lake restoration? Schweizerische Zeitschrift für Hydrologie 49: 237–248. Benndorf, J. 1995. Possibilities and limits for controlling eutrophication by biomanipulation. Internationale Revue der gesampten Hydrobiologie 80: 519–534. Box, G. E. P., W. G. Hunter, and J. S. Hunter . 1978. Statistics for experimenters. Wiley, New York, New York, USA. Brooks, J. L., and S. I. Dodson . 1965. Body size and composition of plankton. Science 150: 28–35. Carpenter, S. R. 1988. Transmission of variance through lake food webs. Pages 119–138 in S. R. Carpenter, editor. Complex interactions in lake communities. Springer-Verlag, New York, New York, USA. Carpenter, S. R. 1999. Role of microcosm experiments in aquatic ecology: reply. Ecology 80: 1085–1088. Carpenter, S. R., D. L. Christensen, J. J. Cole, K. L. Cottingham, X. He, J. R. Hodgson, J. F. Kitchell, S. E. Knight, M. L. Pace, D. M. Post, D. E. Schindler, and N. Voichick . 1995. Biological control of eutrophication in lakes. Environmental Science and Technology 29: 784–786. Carpenter, S. R., J. J. Cole, T. E. Essington, J. R. Hodgson, J. N. Houser, J. F. Kitchell, and M. L. Pace . 1998a. Evaluating alternative explanations in ecosystem experiments. Ecosystems 1: 335–344. Carpenter, S. R., J. J. Cole, J. F. Kitchell, and M. L. Pace . 1998b. Impact of dissolved organic carbon, phosphorus and grazing on phytoplankton biomass and production in experimental lakes. Limnology and Oceanography 43: 73–80. Carpenter, S. R., T. M. Frost, J. F. Kitchell, T. K. Kratz, D. W. Schindler, J. Shearer, W. G. Sprules, M. J. Vanni, and A. P. Zimmerman . 1991. Patterns of primary production and herbivory in 25 North American lake ecosystems. Pages 67–96 in J. Cole, G. Lovett, and S. Findlay, editors. Comparative analyses of ecosystems. Springer-Verlag, New York, New York, USA. Carpenter, S. R., and J. F. Kitchell . 1988. Consumer control of lake productivity. BioScience 38: 764–769. Carpenter, S. R., and J. F. Kitchell . 1993. The trophic cascade in lakes. Cambridge University Press, Cambridge, UK. Carpenter, S. R., J. F. Kitchell, J. J. Cole, and M. L. Pace . 1999. Predicting responses of chlorophyll and primary production to changes in phosphorus, grazing and dissolved organic carbon. Limnology and Oceanography 44: 1179–1182. Carpenter, S. R., J. F. Kitchell, K. L. Cottingham, D. E. Schindler, D. L. Christensen, D. M. Post, and N. Voichick . 1996. Chlorophyll variability, nutrient input and grazing: evidence from whole-lake experiments. Ecology 77: 725–735. Carpenter, S. R., J. F. Kitchell, J. R. Hodgson, P. A. Cochran, J. J. Elser, M. M. Elser, D. M. Lodge, D. Kretchmer, X. He, and C. N. von Ende . 1987. Regulation of lake primary productivity by food web structure. Ecology 68: 1863–1876. Christensen, D. L., S. R. Carpenter, K. L. Cottingham, S. E. Knight, J. P. LeBouton, D. E. Schindler, N. Voichick, J. J. Cole, and M. L. Pace . 1996. Pelagic responses to changes in dissolved organic carbon following division of a seepage lake. Limnology and Oceanography 41: 553–559. Cole, J. J., and N. F. Caraco . 1998. Atmospheric exchange of carbon dioxide in a low-wind oligotrophic lake measured by the addition of SF6. Limnology and Oceanography 43: 647–656. Cole, J. J., N. F. Caraco, G. W. Kling, and T. K. Kratz . 1994. Carbon dioxide supersaturation in the surface waters of lakes. Science 265: 1568–1570. Cole, J. J., S. Findlay, and M. L. Pace . 1988. Bacterial production in fresh and saltwater ecosystems: a cross-system overview. Marine Ecology Progress Series 43: 1–10. Cole, J. J., and M. L. Pace . 1998. Hydrologic variability of small, northern Michigan lakes measured by the addition of tracers. Ecosystems 1: 310–320. Cottingham, K. L. 1999. Nutrients and zooplankton as multiple stressors of phytoplankton communities: evidence from size structure. Limnology and Oceanography 44: 810–827. Cottingham, K. L., and S. R. Carpenter . 1998. Population, community, and ecosystem variates as ecological indicators: phytoplankton responses to whole-lake enrichment. Ecological Applications 8: 508–530. Cottingham, K. L., S. R. Carpenter, and A. L. St. Amand . 1998. Responses of epilimnetic phytoplankton to experimental nutrient enrichment in three small seepage lakes. Journal of Plankton Research 20: 1889–1914. Currie, D. J., P. Dilworth-Christie, and F. Chapleau . 1999. Assessing the strength of top-down influences on plankton abundance in unmanipulated lakes. Canadian Journal of Fisheries and Aquatic Sciences 56: 427–436. Downing, J., and F. H. Rigler . 1984. Secondary productivity in fresh waters. Blackwell, New York, New York, USA. Elser, J. J., T. H. Chrzanowski, R. W. Sterner, and K. H. Mills . 1998. Stoichiometric constraints on food-web dynamics: a whole-lake experiment on the Canadian shield. Ecosystems 1: 120–136. Elser, J. J., D. R. Dobberfuhl, N. A. MacKay, and J. H. Schampel . 1996. Organism size, life history, and N:P stoichiometry. BioScience 46: 674–684. Essington, T. E., and J. F. Kitchell . 1999. New perspectives in the analysis of fish distributions: a case study on the spatial distribution of largemouth bass. Canadian Journal of Fisheries and Aquatic Sciences 56: (Supplement 1) 52–60. Gulati, R. D., and W. R. DeMott . 1997. The role of food quality for zooplankton: remarks on the state of the art, perspectives and priorities. Freshwater Biology 38: 753–768. Hambright, K. D. 1994. Morphological constraints on the piscivore–planktivore interaction—implications for the trophic cascade hypothesis. Limnology and Oceanography 39: 897–912. Hansson, L. A., H. Annadotter, E. Bergman, S. F. Hamrin, E. Jeppesen, T. Kairesalo, E. Luokkanen, P. A. Nilsson, M. Søndergaard, and J. Strand . 1998. Biomanipulation as an application of food-chain theory: constraints, synthesis, and recommendations for temperate lakes. Ecosystems 1: 558–574. He, X., J. R. Hodgson, J. F. Kitchell, and R. A. Wright . 1994. Growth and diet composition of largemouth bass in four experimental lakes. Internationale Vereinigung fur Theoreticsche und Angewandte Limnologie 25: 766–772. Hobbie, J. E., R. J. Daley, and S. Jasper . 1977. Use of nuclepore filters for counting bacteria by fluorescent microscopy. Applied and Environmental Microbiology 33: 1225–1228. Hodgson, J. R., X. He, D. E. Schindler, and J. F. Kitchell . 1997. Diet overlap in a piscivore community. Ecology of Freshwater Fish 6: 144–149. Hodgson, J. Y., and J. R. Hodgson . 2001. Exploring optimal foraging by largemouth bass (Micropterus salmoides) from three experimental lakes. Internationale Vereinigung fur Theoreticsche und Angewandte Limnologie, In press. Hoover, T. E., and D. C. Berkshire . 1969. Effects of hydration on carbon dioxide exchange across an air–water interface. Journal of Geophysical Research 74: 456–464. Houser, J. N., S. R. Carpenter, and J. J. Cole . 2000. Food web structure and nutrient enrichment: effects on sediment phosphorus retention in whole-lake experiments. Canadian Journal of Fisheries and Aquatic Sciences 57: 1524–1533. Hrbácek, J. M., V. Dvoraková, V. Korinek, and L. Procházková . 1961. Demonstration of the effect of the fish stock on the species composition of zooplankton and the intensity of the metabolism of the whole plankton association. Internationale Vereinigung für Theoretische und Angewandte Limnologie 14: 192–195. Hurlbert, S. H., J. Zedler, and D. Fairbanks . 1972. Ecosystem alteration by mosquitofish (Gambusia affinis) predation. Science 175: 639–641. Jeppesen, E., Ma. Søndergaard, Mo. Søndergaard, and K. Christoffersen . editors 1998. The structuring role of submerged macrophytes in lakes. Springer-Verlag, Berlin, Germany. Kitchell, J. F., E. A. Eby, X. He, D. E. Schindler, and R. A. Wright . 1994. Predator–prey dynamics in an ecosystem context. Journal of Fish Biology 45: 1–18. Kling, G. W., G. W. Kipphut, and M. C. Miller . 1991. Arctic lakes and streams as gas conduits to the atmosphere—implications for tundra carbon budgets. Science 251: 298–301. Lodge, D. M., S. C. Blumenshine, and Y. Vadeboncoeur . 1998. Insights and applications of large scale, long term ecological observations and experiments. Pages 202–235 in W. R. Resetarits and J. Bernardo, editors. Experimental ecology: issues and perspectives. Oxford University Press, Cambridge, UK. Marker, A. F. H., C. A. Crowther, and R. J. M. Gunn . 1980. Methanol and acetone as solvents for estimating chlorophyll and pheopigments by spectrophotometry. Ergebnisse der Limnologie 14: 52–69. Mazumder, A. 1994. Phosphorus–chlorophyll relationships under contrasting herbivory and thermal stratification: predictions and patterns. Canadian Journal of Fisheries and Aquatic Sciences 51: 401–407. Meijer, M.-L., I. De Boos, M. Scheffer, R. Portielje, and H. Hosper . 1999. Biomanipulation in shallow lakes in the Netherlands: an evaluation of 18 case studies. Hydrobiologia 408/409: 13–30. Meijer, M.-L., E. Jeppesen, E. van Donk, B. Moss, M. Scheffer, E. Lammens, E. van Nes, J. A. van Berkum, G. J. de Jong, B. A. Faafeng, and J. P. Jensen . 1994. Long-term responses to fish-stock reduction in small shallow lakes: interpretation of five-year results of four biomanipulation cases in The Netherlands and Denmark. Hydrobiologia 275/276: 457–466. Micheli, F. 1999. Eutrophication, fisheries and consumer–resource dynamics in marine pelagic ecosystems. Science 285: 1396–1398. Mills, E. L., and A. Schiavone . 1982. Evaluation of fish communities through assessment of zooplankton populations and measures of lake productivities. North American Journal of Fisheries Management 2: 14–27. Mittelbach, G. G., A. M. Turner, D. J. Hall, J. E. Rettig, and C. W. Osenberg . 1995. Perturbation and resilience in an aquatic community: a long-term study of the extinction and reintroduction of a top predator. Ecology 76: 2347–2360. Murdoch, W. W., R. M. Nisbet, E. McCauley, A. M. de Roos, and W. S. C. Gurney . 1998. Plankton abundance and dynamics across nutrient levels: tests of hypotheses. Ecology 79: 1339–1356. Nürnberg, G. K. 1999. Determining trophic state in experimental lakes. Limnology and Oceanography 44: 1176–1179. Pace, M. L. 1984. Zooplankton community structure, but not biomass, influences the phosphorus–chlorophyll a relationship. Canadian Journal of Fisheries and Aquatic Sciences 41: 1089–1096. Pace, M. L. 2001. Getting it right and wrong: extrapolations across experimental scales. Pages 161–181 in R. Gardner, M. Kemp, V. Kennedy, and J. Peterson, editors. Scaling relations in experimental ecology. Columbia University Press, New York, New York, USA. Pace, M. L., and J. J. Cole . 1994. Primary and bacterial production: are they coupled over depth? Journal of Plankton Research 16: 661–672. Pace, M. L., and J. J. Cole . 1996. Regulation of bacterial by resources and predation tested in whole-lake experiments. Limnology and Oceanography 41: 1448–1460. Pace, M. L., J. J. Cole, and S. R. Carpenter . 1998. Trophic cascades and compensation: differential responses of microzooplankton in whole-lake experiments. Ecology 79: 138–152. Pace, M. L., J. J. Cole, S. R. Carpenter, and J. F. Kitchell . 1999. Trophic cascades revealed in diverse ecosystems. Trends in Ecology and Evolution 14: 483–488. Paine, R. T. 1980. Food webs: linkage, interaction strength and community infrastructure. Journal of Animal Ecology 49: 667–685. Persson, L. 1999. Trophic cascades: abiding heterogeneity and the trophic level concept at the end of the road. Oikos 85: 385–397. Persson, L., S. Diehl, L. Johansson, G. Andersson, and S. F. Hamrin . 1992. Trophic interactions in temperate lake ecosystems: a test of food chain theory. The American Naturalist 140: 59–84. Peters, R. H., and J. Downing . 1984. Empirical analysis of zooplankton filtering and feeding rates. Limnology and Oceanography 29: 763–784. Polis, G. A. 1999. Why are parts of the world green? Multiple factors control productivity and the distribution of biomass. Oikos 86: 3–15. Post, D. M., S. R. Carpenter, D. L. Christensen, K. L. Cottingham, J. R. Hodgson, J. F. Kitchell, and D. E. Schindler . 1997. Seasonal effects of variable recruitment of a dominant piscivore on pelagic food web structure. Limnology and Oceanography 42: 722–729. Quiros, R. 1990a. Empirical relationships between nutrients, phyto- and zooplankton and relative fish biomass in lakes and reservoirs of Argentina. Internationale Vereinigung fur theoretische und angewandte Limnologie 24: 1198–1206. Quiros, R. 1990b. Factors related to variance of residuals in chlorophyll–total phosphorus regressions in lakes and reservoirs of Argentina. Hydrobiologia 200/201: 343–355. Quiros, R. 1998. Fish effects on trophic relationships in the pelagic zone of lakes. Hydrobiologia 361: 101–111. Reynolds, C. S. 1994. The ecological basis for the successful biomanipulation of aquatic communities. Archiv für Hydrobiologie 130: 1–33. Sarnelle, O. 1992. Nutrient enrichment and grazer effects on phytoplankton in lakes. Ecology 73: 551–560. Scheffer, M. 1997. Ecology of shallow lakes. Chapman and Hall, New York, New York, USA. Schindler, D. E., S. R. Carpenter, J. J. Cole, J. F. Kitchell, and M. L. Pace . 1997a. Food web structure alters carbon exchange between lakes and the atmosphere. Science 277: 248–251. Schindler, D. E., J. R. Hodgson, and J. F. Kitchell . 1997b. Density-dependent changes in individual foraging specialization of largemouth bass. Oecologia 110: 592–600. Schindler, D. E., J. F. Kitchell, X. He, S. R. Carpenter, J. R. Hodgson, and K. L. Cottingham . 1993. Food web structure and phosphorus cycling in lakes. Transactions of the American Fisheries Society 122: 756–772. Schindler, D. W. 1998. Replication versus realism: the necessity for ecosystem-scale experiments, replicated or not. Ecosystems 1: 323–334. Schindler, D. W., E. J. Fee, and T. Ruszczynski . 1978. Phosphorus input and its consequences for phytoplankton standing crop and production in the Experimental Lakes Area and in similar lakes. Journal of the Fisheries Research Board of Canada 35: 190–196. Shapiro, J. 1990. Biomanipulation: the next phase—making it stable. Hydrobiologia 200/201: 13–27. Shapiro, J., V. Lamarra, and M. Lynch . 1975. Biomanipulation: an ecosystem approach to lake restoration. Pages 85–96 in P. L. Brezonik and J. L. Fox, editors. Water quality management through biological control. University of Florida, Gainesville, Florida, USA. Shiomoto, A., K. Tadokoro, K. Nagasawa, and Y. Ishida . 1997. Trophic relations in the subarctic North Pacific ecosystem: possible feeding effect from pink salmon. Marine Ecology Progress Series 150: 75–85. Stainton, M. P. 1973. A syringe gas-stripping procedure for gas-chromatographic determination of dissolved inorganic and organic carbon in freshwater and carbonates in sediments. Journal of the Fisheries Research Board of Canada 30: 1441–1445. Strong, D. R. 1992. Are trophic cascades all wet? Differentiation and donor-control in speciose ecosystems. Ecology 73: 747–754. Vadeboncoeur, Y., D. M. Lodge, and S. R. Carpenter . 2001. Whole-lake fertilization effects on distribution of primary production between benthic and pelagic habitats. Ecology 82: 1065–1077. Vollenweider, R. A. 1976. Advances in defining critical loading levels for P in lake eutrophication. Memorie dell'Istituto Italiano di Idrobiologia 33: 53–83. Walters, C. J. 1986. Adaptive management of renewable resources. MacMillan, New York, New York, USA. Weiss, R. F. 1974. Carbon dioxide in water and seawater: the solubility of a non-ideal gas. Marine Chemistry 2: 203–215. White, P. A., J. Kalff, J. B. Rasmussen, and J. M. Gasol . 1991. The effect of temperature and algal biomass on bacterial production and specific growth rate in freshwater and marine habitats. Microbial Ecology 21: 99–118. Citing Literature Volume71, Issue2May 2001Pages 163-186 ReferencesRelatedInformation

Net ecosystem production (NEP) is the difference between gross primary production (GPP) and community respiration (R). We estimated in situ NEP using three independent approaches (net CO 2 gas flux, net O 2 gas flux, and continuous diel O 2 measurements) over a 4–7 yr period in a series of small lakes in which food webs were manipulated and nutrient loadings were experimentally varied. In the absence of manipulation, these lakes were net heterotrophic according to all three approaches. NEP (NEP = GPP‐R) was consistently negative and averaged −35.5 ± 3.7 (standard error) mmol C m −2 d −1 . Nutrient enrichment, in the absence of strong planktivory, tended to cause increases in estimates of both GPP and R (estimated from the continuous O 2 data) but resulted in little change in the GPP/R ratio, which remained &lt;1, or NEP, which remained negative. When planktivorous fish dominated the food web, large zooplankton were rare and nutrient enrichment produced positive values of NEP by all three methods. Among lakes and years, daily values of NEP ranged from −241 to +175 mmol m −2 d −1 ; mean seasonal NEP was positive only under a combination of high nutrient loading and a planktivore‐dominated food web. Community R is significantly subsidized by allochthonous sources of organic matter in these lakes. Combining all lakes and years, we estimate that ~26 mmol C m −2 d −1 of allochthonous origin is respired on average. This respiration of allochthonous organic matter represents 13 to 43% of total R, and this fraction declines with increasing GPP.

Humanity has emerged as a major force in the operation of the biosphere, with a significant imprint on the Earth System, challenging social-ecological resilience. This new situation calls for a fundamental shift in perspectives, world views, and institutions. Human development and progress must be reconnected to the capacity of the biosphere and essential ecosystem services to be sustained. Governance challenges include a highly interconnected and faster world, cascading social-ecological interactions and planetary boundaries that create vulnerabilities but also opportunities for social-ecological change and transformation. Tipping points and thresholds highlight the importance of understanding and managing resilience. New modes of flexible governance are emerging. A central challenge is to reconnect these efforts to the changing preconditions for societal development as active stewards of the Earth System. We suggest that the Millennium Development Goals need to be reframed in such a planetary stewardship context combined with a call for a new social contract on global sustainability. The ongoing mind shift in human relations with Earth and its boundaries provides exciting opportunities for societal development in collaboration with the biosphere--a global sustainability agenda for humanity.

Global change issues are complex and the consequences of decisions are often highly uncertain. The large spatial and temporal scales and stakes involved make it important to take account of present and potential consequences in decision-making. Standard approaches to decision-making under uncertainty require information about the likelihood of alternative states, how states and actions combine to form outcomes and the net benefits of different outcomes. For global change issues, however, the set of potential states is often unknown, much less the probabilities, effect of actions or their net benefits. Decision theory, thresholds, scenarios and resilience thinking can expand awareness of the potential states and outcomes, as well as of the probabilities and consequences of outcomes under alternative decisions.

The scale, rate, and intensity of humans’ environmental impact has engendered broad discussion about how to find plausible pathways of development that hold the most promise for fostering a better future in the Anthropocene. However, the dominance of dystopian visions of irreversible environmental degradation and societal collapse, along with overly optimistic utopias and business‐as‐usual scenarios that lack insight and innovation, frustrate progress. Here, we present a novel approach to thinking about the future that builds on experiences drawn from a diversity of practices, worldviews, values, and regions that could accelerate the adoption of pathways to transformative change (change that goes beyond incremental improvements). Using an analysis of 100 initiatives, or “seeds of a good Anthropocene”, we find that emphasizing hopeful elements of existing practice offers the opportunity to: (1) understand the values and features that constitute a good Anthropocene, (2) determine the processes that lead to the emergence and growth of initiatives that fundamentally change human–environmental relationships, and (3) generate creative, bottom‐up scenarios that feature well‐articulated pathways toward a more positive future.

Species distribution models (SDMs) are numerical tools that combine observations of species occurrence or abundance with environmental estimates. They are used to gain ecological and evolutionary insights and to predict distributions across landscapes, ...Read More

Journal Article Consumer Control of Lake Productivity: Large-scale experimental manipulations reveal complex interactions among lake organisms Get access Stephen R. Carpenter, Stephen R. Carpenter Search for other works by this author on: Oxford Academic Google Scholar James F. Kitchell James F. Kitchell Search for other works by this author on: Oxford Academic Google Scholar BioScience, Volume 38, Issue 11, December 1988, Pages 764–769, https://doi.org/10.2307/1310785 Published: 01 December 1988

Whole-lake additions of dissolved inorganic 13C were used to measure allochthony (the terrestrial contribution of organic carbon to aquatic consumers) in two unproductive lakes (Paul and Peter Lakes in 2001), a nutrient-enriched lake (Peter Lake in 2002), and a dystrophic lake (Tuesday Lake in 2002). Three kinds of dynamic models were used to estimate allochthony: a process-rich, dual-isotope flow model based on mass balances of two carbon isotopes in 12 carbon pools; simple univariate time-series models driven by observed time courses of δ13CO2; and multivariate autoregression models that combined information from time series of δ13C in several interacting carbon pools. All three models gave similar estimates of allochthony. In the three experiments without nutrient enrichment, flows of terrestrial carbon to dissolved and particulate organic carbon, zooplankton, Chaoborus, and fishes were substantial. For example, terrestrial sources accounted for more than half the carbon flow to juvenile and adult largemouth bass, pumpkinseed sunfish, golden shiners, brook sticklebacks, and fathead minnows in the unenriched experiments. Allochthony was highest in the dystrophic lake and lowest in the nutrient-enriched lake. Nutrient enrichment of Peter Lake decreased allochthony of zooplankton from 0.34–0.48 to 0–0.12, and of fishes from 0.51–0.80 to 0.25–0.55. These experiments show that lake ecosystem carbon cycles, including carbon flows to consumers, are heavily subsidized by organic carbon from the surrounding landscape.

In the vicinity of tipping points—or more precisely bifurcation points—ecosystems recover slowly from small perturbations. Such slowness may be interpreted as a sign of low resilience in the sense that the ecosystem could easily be tipped through a critical transition into a contrasting state. Indicators of this phenomenon of ‘critical slowing down (CSD)’ include a rise in temporal correlation and variance. Such indicators of CSD can provide an early warning signal of a nearby tipping point. Or, they may offer a possibility to rank reefs, lakes or other ecosystems according to their resilience. The fact that CSD may happen across a wide range of complex ecosystems close to tipping points implies a powerful generality. However, indicators of CSD are not manifested in all cases where regime shifts occur. This is because not all regime shifts are associated with tipping points. Here, we review the exploding literature about this issue to provide guidance on what to expect and what not to expect when it comes to the CSD-based early warning signals for critical transitions.

Despite growing recognition of the importance of ecosystem services and the economic and ecological harm caused by invasive species, linkages between invasions, changes in ecosystem functioning, and in turn, provisioning of ecosystem services remain poorly documented and poorly understood. We evaluate the economic impacts of an invasion that cascaded through a food web to cause substantial declines in water clarity, a valued ecosystem service. The predatory zooplankton, the spiny water flea (Bythotrephes longimanus), invaded the Laurentian Great Lakes in the 1980s and has subsequently undergone secondary spread to inland lakes, including Lake Mendota (Wisconsin), in 2009. In Lake Mendota, Bythotrephes has reached unparalleled densities compared with in other lakes, decreasing biomass of the grazer Daphnia pulicaria and causing a decline in water clarity of nearly 1 m. Time series modeling revealed that the loss in water clarity, valued at US$140 million (US$640 per household), could be reversed by a 71% reduction in phosphorus loading. A phosphorus reduction of this magnitude is estimated to cost between US$86.5 million and US$163 million (US$430-US$810 per household). Estimates of the economic effects of Great Lakes invasive species may increase considerably if cases of secondary invasions into inland lakes, such as Lake Mendota, are included. Furthermore, such extreme cases of economic damages call for increased investment in the prevention and control of invasive species to better maximize the economic benefits of such programs. Our results highlight the need to more fully incorporate ecosystem services into our analysis of invasive species impacts, management, and public policy.

Adaptive capacity is the ability of a living system, such as a social-ecological system, to adjust responses to changing internal demands and external drivers. Although adaptive capacity is a frequent topic of study in the resilience literature, there are few formal models. This paper introduces such a model and uses it to explore adaptive capacity by contrast with the opposite condition, or traps. In a social- ecological rigidity trap, strong self-reinforcing controls prevent the flexibility needed for adaptation. In the model, too much control erodes adaptive capacity and thereby increases the risk of catastrophic breakdown. In a social-ecological poverty trap, loose connections prevent the mobilization of ideas and resources to solve problems. In the model, too little control impedes the focus needed for adaptation. Fluctuations of internal demand or external shocks generate pulses of adaptive capacity, which may gain traction and pull the system out of the poverty trap. The model suggests some general properties of traps in social-ecological systems. It is general and flexible, so it can be used as a building block in more specific and detailed models of adaptive capacity for a particular region.

Ecological resilience is the ability of a system to persist in the face of perturbations. Although resilience has been a highly influential concept, its interpretation has remained largely qualitative. Here we describe an emerging family of methods for quantifying resilience on the basis of observations. A first set of methods is based on the phenomenon of critical slowing down, which implies that recovery upon small perturbations becomes slower as a system approaches a tipping point. Such slowing down can be measured experimentally but may also be indirectly inferred from changes in natural fluctuations and spatial patterns. A second group of methods aims to characterize the resilience of alternative states in probabilistic terms based on large numbers of observations as in long time series or satellite images. These generic approaches to measuring resilience complement the system-specific knowledge needed to infer the effects of environmental change on the resilience of complex systems.

Recent literature has suggested that for many lakes and rivers, the respiratory breakdown of organic matter (R) exceeds production of organic matter by photosynthesis (gross primary production [GPP]) within the water body. This metabolic balance (GPP &gt; R; “heterotrophy”) implies that allochthonous organic matter supports a portion of the aquatic ecosystem's respiration. Evidence that many lakes are heterotrophic comes from diverse approaches, and debate remains over the circumstances in which heterotrophy exists. The methods used to estimate GPP and R and the limited extent of lake types studied, especially with respect to dissolved organic carbon (DOC) and total phosphorus (TP) concentrations, are two reasons for differing conclusions. We deployed O 2 and CO 2 sondes to measure diel gas dynamics in the surface waters of 25 lakes. From these data, we calculated GPP, R, and net ecosystem production (NEP = GPP − R). Over the broad range in TP and DOC among the lakes, diel CO 2 and O 2 changed on a near 1 : 1 molar ratio. Metabolism estimates from the two gases were comparable, except at high pH. Most lakes in our data set had negative NEP, but GPP and R appeared to be controlled by different factors. TP correlated strongly with GPP, whereas DOC correlated with R. At low DOC concentrations, GPP and R were nearly equal, but, at higher DOC, GPP and R uncoupled and lakes had negative NEP. Strong correlations between lake metabolism and landscape related variables suggest that allochthonous carbon influences lake metabolism.

Phosphorus (P) is a critical factor for food production, yet surface freshwaters and some coastal waters are highly sensitive to eutrophication by excess P. A planetary boundary, or upper tolerable limit, for P discharge to the oceans is thought to be ten times the pre-industrial rate, or more than three times the current rate. However this boundary does not take account of freshwater eutrophication. We analyzed the global P cycle to estimate planetary boundaries for freshwater eutrophication. Planetary boundaries were computed for the input of P to freshwaters, the input of P to terrestrial soil, and the mass of P in soil. Each boundary was computed for two water quality targets, 24 mg P m − 3, a typical target for lakes and reservoirs, and 160 mg m − 3, the approximate pre-industrial P concentration in the world's rivers. Planetary boundaries were also computed using three published estimates of current P flow to the sea. Current conditions exceed all planetary boundaries for P. Substantial differences between current conditions and planetary boundaries demonstrate the contrast between large amounts of P needed for food production and the high sensitivity of freshwaters to pollution by P runoff. At the same time, some regions of the world are P-deficient, and there are some indications that a global P shortage is possible in coming decades. More efficient recycling and retention of P within agricultural ecosystems could maintain or increase food production while reducing P pollution and improving water quality. Spatial heterogeneity in the global P cycle suggests that recycling of P in regions of excess and transfer of P to regions of deficiency could mitigate eutrophication, increase agricultural yield, and delay or avoid global P shortage.

Abstract Organic carbon inputs from outside of ecosystem boundaries potentially subsidize recipient food webs. Four whole‐lake additions of dissolved inorganic 13 C were made to reveal the pathways of subsidies to lakes from terrestrial dissolved organic carbon (t‐DOC), terrestrial particulate organic carbon (t‐POC) and terrestrial prey items. Terrestrial DOC, the largest input, was a major subsidy of pelagic bacterial respiration, but little of this bacterial C was passed up the food web. Zooplankton received &lt;2% of their C from the t‐DOC to bacteria pathway. Terrestrial POC significantly subsidized the production of both zooplankton and benthic invertebrates, and was passed up the food web to Chaoborus and fishes. This route supplied 33–73% of carbon flow to zooplankton and 20–50% to fishes in non‐fertilized lakes. Terrestrial prey, by far the smallest input, provided some fishes with &gt;20% of their carbon. The results show that impacts of cross‐ecosystem subsidies depend on characteristics of the imported material, the route of entry into the food web, the types of consumers present, and the productivity of the recipient system.

Navigating global changes requires a coevolving set of collaborative, global institutions.

A number of ecosystems can exhibit abrupt shifts between alternative stable states. Because of their important ecological and economic consequences, recent research has focused on devising early warning signals for anticipating such abrupt ecological transitions. In particular, theoretical studies show that changes in spatial characteristics of the system could provide early warnings of approaching transitions. However, the empirical validation of these indicators lag behind their theoretical developments. Here, we summarize a range of currently available spatial early warning signals, suggest potential null models to interpret their trends, and apply them to three simulated spatial data sets of systems undergoing an abrupt transition. In addition to providing a step-by-step methodology for applying these signals to spatial data sets, we propose a statistical toolbox that may be used to help detect approaching transitions in a wide range of spatial data. We hope that our methodology together with the computer codes will stimulate the application and testing of spatial early warning signals on real spatial data.

The widespread emergence of human and wildlife diseases has challenged ecologists to understand how large-scale agents of environmental change affect host-pathogen interactions. Accelerated eutrophication of aquatic ecosystems owing to nitrogen and phosphorus enrichment is a pervasive form of environmental change that has been implicated in the emergence of diseases through direct and indirect pathways. We provide experimental evidence linking eutrophication and disease in a multihost parasite system. The trematode parasite Ribeiroia ondatrae sequentially infects birds, snails, and amphibian larvae, frequently causing severe limb deformities and mortality. Eutrophication has been implicated in the emergence of this parasite, but definitive evidence, as well as a mechanistic understanding, have been lacking until now. We show that the effects of eutrophication cascade through the parasite life cycle to promote algal production, the density of snail hosts, and, ultimately, the intensity of infection in amphibians. Infection also negatively affected the survival of developing amphibians. Mechanistically, eutrophication promoted amphibian disease through two distinctive pathways: by increasing the density of infected snail hosts and by enhancing per-snail production of infectious parasites. Given forecasted increases in global eutrophication, amphibian extinctions, and similarities between Ribeiroia and important human and wildlife pathogens, our results have broad epidemiological and ecological significance.

The Millennium Ecosystem Assessment (MA) scenarios address changes in ecosystem services and their implications for human well-being. Ecological changes pose special challenges for longterm thinking, because of the possibility of regime shifts that occur rapidly yet alter the availability of ecosystem services for generations. Moreover, ecological feedbacks can intensify human modification of ecosystems, creating a spiral of poverty and ecosystem degradation. Such complex dynamics were evaluated by a mixture of qualitative and quantitative analyses in the MA scenarios. Collectively, the scenarios explore problems such as the connections of poverty reduction and ecosystem services, and trade-offs among ecosystem services. Several promising approaches are considered by the scenarios, including uses of biodiversity to build resilience of ecosystem services, actively adaptive management, and green technology. Although the scenarios do not prescribe an optimal path, they illuminate the consequences of different policies toward ecosystem services.

Limitation of algal growth by nitrogen and phosphorus was assessed in three north‐temperate lakes with physiological bioassays and nutrient enrichment experiments. In addition, mesocosm experiments were performed in the three lakes to examine the effects of nutrient enrichment and zooplankton biomass and size on algal nutrient status. In situ indicators of N and P availability were inversely related in magnitude and transitions between N and P limitation were abrupt. Physiological bioassay results did not indicate simultaneous limitation by N and P. However, limited responses to single‐nutrient enrichment and pronounced responses to simultaneous N and P addition in enrichment experiments suggested that potential limitation by the secondary nutrient was usually in close proximity to limitation by the primary nutrient. Transitions between N and P limitation closely accompanied major shifts in the zooplankton community. The importance of the zooplankton community in regulating the relative degree of N or P limitation was confirmed by the mesocosm experiments, which demonstrated that transitions between algal N or P limitation could be induced by manipulations of zooplankton biomass or size. This result supports a hierarchical view of the function of planktonic systems, in which biotic interactions structure the response of the algal community to a given nutrient load.

Cross-ecosystem subsidies to food webs can alter metabolic balances in the receiving (subsidized) system and free the food web, or particular consumers, from the energetic constraints of local primary production. Although cross-ecosystem subsidies between terrestrial and aquatic systems have been well recognized for benthic organisms in streams, rivers, and the littoral zones of lakes, terrestrial subsidies to pelagic consumers are more difficult to demonstrate and remain controversial. Here, we adopt a unique approach by using stable isotopes of H, C, and N to estimate terrestrial support to zooplankton in two contrasting lakes. Zooplankton (Holopedium, Daphnia, and Leptodiaptomus) are comprised of ≈ 20-40% of organic material of terrestrial origin. These estimates are as high as, or higher than, prior measures obtained by experimentally manipulating the inorganic (13)C content of these lakes to augment the small, natural contrast in (13)C between terrestrial and algal photosynthesis. Our study gives credence to a growing literature, which we review here, suggesting that significant terrestrial support of pelagic crustaceans (zooplankton) is widespread.

The COVID-19 pandemic has exposed an interconnected and tightly coupled globalized world in rapid change. This article sets the scientific stage for understanding and responding to such change for global sustainability and resilient societies. We provide a systemic overview of the current situation where people and nature are dynamically intertwined and embedded in the biosphere, placing shocks and extreme events as part of this dynamic; humanity has become the major force in shaping the future of the Earth system as a whole; and the scale and pace of the human dimension have caused climate change, rapid loss of biodiversity, growing inequalities, and loss of resilience to deal with uncertainty and surprise. Taken together, human actions are challenging the biosphere foundation for a prosperous development of civilizations. The Anthropocene reality-of rising system-wide turbulence-calls for transformative change towards sustainable futures. Emerging technologies, social innovations, broader shifts in cultural repertoires, as well as a diverse portfolio of active stewardship of human actions in support of a resilient biosphere are highlighted as essential parts of such transformations.

Expanding croplands to meet the needs of a growing population, changing diets, and biofuel production comes at the cost of reduced carbon stocks in natural vegetation and soils. Here, we present a spatially explicit global analysis of tradeoffs between carbon stocks and current crop yields. The difference among regions is striking. For example, for each unit of land cleared, the tropics lose nearly two times as much carbon (∼120 tons·ha −1 vs. ∼63 tons·ha −1 ) and produce less than one-half the annual crop yield compared with temperate regions (1.71 tons·ha −1 ·y −1 vs. 3.84 tons·ha −1 ·y −1 ). Therefore, newly cleared land in the tropics releases nearly 3 tons of carbon for every 1 ton of annual crop yield compared with a similar area cleared in the temperate zone. By factoring crop yield into the analysis, we specify the tradeoff between carbon stocks and crops for all areas where crops are currently grown and thereby, substantially enhance the spatial resolution relative to previous regional estimates. Particularly in the tropics, emphasis should be placed on increasing yields on existing croplands rather than clearing new lands. Our high-resolution approach can be used to determine the net effect of local land use decisions.

Resilience to specified kinds of disasters is an active area of research and practice. However, rare or unprecedented disturbances that are unusually intense or extensive require a more broad-spectrum type of resilience. General resilience is the capacity of social-ecological systems to adapt or transform in response to unfamiliar, unexpected and extreme shocks. Conditions that enable general resilience include diversity, modularity, openness, reserves, feedbacks, nestedness, monitoring, leadership, and trust. Processes for building general resilience are an emerging and crucially important area of research.

The concept of social–ecological systems is useful for understanding the interlinked dynamics of environmental and societal change. The concept has helped facilitate: (1) increased recognition of the dependence of humanity on ecosystems; (2) improved collaboration across disciplines, and between science and society; (3) increased methodological pluralism leading to improved systems understanding; and (4) major policy frameworks considering social–ecological interactions. Despite these advances, the potential of a social–ecological systems perspective to improve sustainability outcomes has not been fully realized. Key priorities are to: (1) better understand and govern social–ecological interactions between regions; (2) pay greater attention to long-term drivers; (3) better understand the interactions among power relations, justice, and ecosystem stewardship; and (4) develop a stronger science–society interface.

Life on Earth has repeatedly displayed abrupt and massive changes in the past, and there is no reason to expect that comparable planetary-scale regime shifts will not continue in the future. Different lines of evidence indicate that regime shifts occur when the climate or biosphere transgresses a tipping point. Whether human activities will trigger such a global event in the near future is uncertain, due to critical knowledge gaps. In particular, we lack understanding of how regime shifts propagate across scales, and whether local or regional tipping points can lead to global transitions. The ongoing disruption of ecosystems and climate, combined with unprecedented breakdown of isolation by human migration and trade, highlights the need to operate within safe planetary boundaries.

Biggs, R., F. R. Westley, and S. R. Carpenter. 2010. Navigating the back loop: fostering social innovation and transformation in ecosystem management. Ecology and Society 15(2): 9. https://doi.org/10.5751/ES-03411-150209

The planetary boundary framework presents a ‘planetary dashboard’ of humanity’s globally aggregated performance on a set of environmental issues that endanger the Earth system’s capacity to support humanity. While this framework has been highly influential, a critical shortcoming for its application in sustainability governance is that it currently fails to represent how impacts related to one of the planetary boundaries affect the status of other planetary boundaries. Here, we surveyed and provisionally quantified interactions between the Earth system processes represented by the planetary boundaries and investigated their consequences for sustainability governance. We identified a dense network of interactions between the planetary boundaries. The resulting cascades and feedbacks predominantly amplify human impacts on the Earth system and thereby shrink the safe operating space for future human impacts on the Earth system. Our results show that an integrated understanding of Earth system dynamics is critical to navigating towards a sustainable future. The cascading effects and feedbacks of interactions between planetary boundaries shrink the safe operating space originally identified by analysing each boundary separately.

Much of the Earth’s biosphere has been appropriated for the production of harvestable biomass in the form of food, fuel and fibre. Here we show that the simplification and intensification of these systems and their growing connection to international markets has yielded a global production ecosystem that is homogenous, highly connected and characterized by weakened internal feedbacks. We argue that these features converge to yield high and predictable supplies of biomass in the short term, but create conditions for novel and pervasive risks to emerge and interact in the longer term. Steering the global production ecosystem towards a sustainable trajectory will require the redirection of finance, increased transparency and traceability in supply chains, and the participation of a multitude of players, including integrated ‘keystone actors’ such as multinational corporations. This Perspective examines the global production ecosystem through the lenses of connectivity, diversity and feedback, and proposes measures that will increase its stability and sustainability.

Manage local stressors to promote resilience to global change

Sustainability within planetary boundaries requires concerted action by individuals, governments, civil society and private actors. For the private sector, there is concern that the power exercised by transnational corporations generates, and is even central to, global environmental change. Here, we ask under which conditions transnational corporations could either hinder or promote a global shift towards sustainability. We show that a handful of transnational corporations have become a major force shaping the global intertwined system of people and planet. Transnational corporations in agriculture, forestry, seafood, cement, minerals and fossil energy cause environmental impacts and possess the ability to influence critical functions of the biosphere. We review evidence of current practices and identify six observed features of change towards 'corporate biosphere stewardship', with significant potential for upscaling. Actions by transnational corporations, if combined with effective public policies and improved governmental regulations, could substantially accelerate sustainability efforts.

Abrupt ecological changes occur rapidly relative to typical rates of ecosystem change and are increasingly observed in ecosystems worldwide, thereby challenging adaptive capacities. Abrupt ecological changes can arise from many processes, only some of which are transitions between alternative states. Focusing solely on the mean values for drivers and states is insufficient for diagnosing abrupt changes, because abrupt changes can be produced by changes in the variability of drivers and disturbance regimes. Diagnosing the likely causes of abrupt state changes in real-world systems remains difficult. Long-term data and experimental manipulations of drivers remains essential. Multiple changing drivers can interact to increase the likelihood of abrupt changes. Identifying interventions that decrease the risk of undesirable abrupt changes is an urgent priority. Abrupt ecological changes are, by definition, those that occur over short periods of time relative to typical rates of change for a given ecosystem. The potential for such changes is growing due to anthropogenic pressures, which challenges the resilience of societies and ecosystems. Abrupt ecological changes are difficult to diagnose because they can arise from a variety of circumstances, including rapid changes in external drivers (e.g., climate, or resource extraction), nonlinear responses to gradual changes in drivers, and interactions among multiple drivers and disturbances. We synthesize strategies for identifying causes of abrupt ecological change and highlight instances where abrupt changes are likely. Diagnosing abrupt changes and inferring causation are increasingly important as society seek to adapt to rapid, multifaceted environmental changes. Abrupt ecological changes are, by definition, those that occur over short periods of time relative to typical rates of change for a given ecosystem. The potential for such changes is growing due to anthropogenic pressures, which challenges the resilience of societies and ecosystems. Abrupt ecological changes are difficult to diagnose because they can arise from a variety of circumstances, including rapid changes in external drivers (e.g., climate, or resource extraction), nonlinear responses to gradual changes in drivers, and interactions among multiple drivers and disturbances. We synthesize strategies for identifying causes of abrupt ecological change and highlight instances where abrupt changes are likely. Diagnosing abrupt changes and inferring causation are increasingly important as society seek to adapt to rapid, multifaceted environmental changes. substantial changes in the mean or variability of a system that occur in a short period of time relative to typical rates of change. two or more states at which an ecosystem can persist, within the same range of driver variables. The alternative states of stochastic processes are characterized by different means, variances, and other statistical moments. Alternative stable state is the term often used in reference to deterministic processes, whereas work focused on stochastic processes often favors terms such as alternative attractor. Often used synonymously with multiple stable states, multiple equilibria, and basins of attraction. transitions that occur when a threshold is passed, causing the disappearance or appearance of alternative states. Often used synonymously with bifurcations. a process that has no random component and is, therefore, theoretically predictable. For instance, at a given combination of a drivers and state variables, a deterministic process consistently repeats the same behaviors. relatively discrete event in time that alters the biotic and/or abiotic components of an ecosystem. the spatial and temporal patterns of disturbances over a long period of time. A disturbance regime is characterized by multiple factors including frequency, return interval, size, intensity, and severity. we use ‘driver’ to refer to external factors that influence the dynamics of a system without themselves being affected by the system. Often synonymous with external forcing or extrinsic processes. ecosystems characterized by two or more alternative states, critical transitions between states, and sensitivity to initial conditions. In hysteretic ecosystems, the conditions required to change state in one direction differ from the conditions required to change back to the original state. an observed large change in an ecosystem. Regime shifts can be gradual or fast, can be produced by many processes, and can involve multiple external drivers and/or internal feedbacks. All abrupt ecological changes are regime shifts, but not all regime shifts are abrupt. A regime shift can or can not be a transition to an alternative state. Often synonymous with state transitions and phase shifts. (i) degree to which an ecosystem can tolerate changing driver variables and/or disturbance without shifting to a qualitatively different state. (ii) The rate of return of the system to its stable state or stationary distribution. Despite having two different definitions since the 1970s, the term resilience is often used imprecisely. All uses of resilience in this paper relate to the first definition. the combinations of states, driver variable values, and disturbance characteristics for which a system is not likely to undergo a regime shift. The boundary of a safe operating space is not a threshold; it is placed a safe distance inside any known or potential thresholds. Safe operating spaces are intended to maintain the resilience of the ecosystem, with resilience given by the first definition above. the characteristics used to describe the status of an ecosystem at a particular domain in space and time. For deterministic systems, the state is the values of variables used to describe the system, and for stochastic systems it could refer to as either the probability distribution of these state variables or realized values of the state variables. In practice, definitions of system state include both the mean and variability of systems. a process that through time generates a random variable characterized by a mean, variance, and higher statistical moments of the state variables of a system (e.g., skewness). Used to contrast deterministic processes that do not involve random variables.

Walker, B. H., S. R. Carpenter, J. Rockstrom, A.-S. Crépin, and G. D. Peterson. 2012. Drivers, "slow" variables, "fast" variables, shocks, and resilience. Ecology and Society 17(3): 30. https://doi.org/10.5751/ES-05063-170330

Fisheries provide food. In industrialized nations, the overwhelming portion of seafood comes from a small number of commercial fishers and increasingly aquaculture (1). Fisheries also contribute to leisure and recreation. In developed nations, 1 in 10 people fishes for pleasure, amounting to at least 220 million recreational fishers worldwide (2, 3)—more than 5 times the number of commercial capture fishers (1). This means that the vast majority of people fishing today do so recreationally (Fig. 1). For too long, the considerable importance and impacts of recreational fisheries have been ignored. Image credit: Florian Mollers (photographer). And yet, for too long, the considerable importance and impacts of recreational fisheries have been ignored. Policymakers and managers need to acknowledge and address the recreational fisheries sector, rethink management objectives and schemes, involve recreational fishers in decision-making processes, incentivize sustainable angler behavior, and improve data collection and monitoring. Recreational fisheries deserve to be considered on equal footing with commercial fisheries, particularly in mixed coastal fisheries. Although commercial capture fisheries globally harvest about 8 times the fish biomass caught by recreational fisheries (4), in many localities recreational landings now rival or even exceed the biomass removals by commercial fisheries. In inland waters in the temperate zone, recreational anglers are now the predominant users of wild fish stocks (5), and recreational fishers have become prevalent in many coastal and marine fisheries (6, 7). Globally, recreational fishers catch about 47 billion individual fish per year, of which more than half are released alive (4), either because of harvest regulations or in response to personal ethics (8). Despite high release rates, fishing for food is a strong motive and justification for recreational fisheries (9). Beyond nutritional benefits, recreational fisheries provide a range of psychological, social, educational, and economic benefits to fishers and society that are … [↵][1]2To whom correspondence should be addressed. Email: arlinghaus{at}igb-berlin.de. [1]: #xref-corresp-1-1

Ecologists have long studied patterns, directions and tempos of change, but there is a pressing need to extend current understanding to empirical observations of abrupt changes as climate warming accelerates. Abrupt changes in ecological systems (ACES)—changes that are fast in time or fast relative to their drivers—are ubiquitous and increasing in frequency. Powerful theoretical frameworks exist, yet applications in real-world landscapes to detect, explain and anticipate ACES have lagged. We highlight five insights emerging from empirical studies of ACES across diverse ecosystems: (i) ecological systems show ACES in some dimensions but not others; (ii) climate extremes may be more important than mean climate in generating ACES; (iii) interactions among multiple drivers often produce ACES; (iv) contingencies, such as ecological memory, frequency and sequence of disturbances, and spatial context are important; and (v) tipping points are often (but not always) associated with ACES. We suggest research priorities to advance understanding of ACES in the face of climate change. Progress in understanding ACES requires strong integration of scientific approaches (theory, observations, experiments and process-based models) and high-quality empirical data drawn from a diverse array of ecosystems. This article is part of the theme issue ‘Climate change and ecosystems: threats, opportunities and solutions’

The environmental sciences have documented large and worrisome changes in earth systems, from climate change and loss of biodiversity, to changes in hydrological and nutrient cycles and depletion of natural resources (1⇓⇓⇓⇓⇓⇓⇓⇓⇓⇓–12). These global environmental changes have potentially large negative consequences for future human well-being, and raise questions about whether global civilization is on a sustainable path or is “consuming too much” by depleting vital natural capital (13). The increased scale of economic activity and the consequent increasing impacts on a finite Earth arises from both major demographic changes—including population growth, shifts in age structure, urbanization, and spatial redistributions through migration (14⇓⇓⇓–18)—and rising per capita income and shifts in consumption patterns, such as increases in meat consumption with rising income (19, 20). At the same time, many people are consuming too little. In 2015, ∼10% of the world’s population (736 million) lived in extreme poverty with incomes of less than $1.90 per day (21). In 2017, 821 million people were malnourished, an increase in the number reported malnourished compared with 2016 (22). There is an urgent need for further economic development to lift people out of poverty. In addition, rising inequality resulting in increasing polarization of society is itself a threat to achieving sustainable development. Eliminating poverty (goal 1) and hunger (goal 2), achieving gender equality (goal 6), and reducing inequality (goal 10) feature prominently in the United Nation’s Sustainable Development Goals (23). A recent special issue in PNAS on natural capital framed the challenge of sustainable development as one of developing “economic, social, and governance systems capable of ending poverty and achieving sustainable levels of population and consumption while securing the life-support systems underpinning current and future human well-being” (24 … [↵][1]1To whom correspondence should be addressed. Email: polasky{at}umn.edu. [1]: #xref-corresp-1-1

Top predators and nutrient loading in lakes were manipulated to assess the influence of food web structure on carbon flux between lakes and the atmosphere. Nutrient enrichment increased primary production, causing lakes to become net sinks for atmospheric carbon (C atm ). Changes in top predators caused shifts in grazers. At identical nutrient loading, C atm invasion was greater to a lake with low grazing than to one with high grazing. Carbon stable-isotope distributions corroborated the drawdown of lake carbon dioxide and traced C atm transfer from algae to top predators. Thus, top predators altered ecosystem carbon fixation and linkages to the atmosphere.

1. Cascading trophic interactions 2. Experimental lakes, manipulations and measurements 3. Statistical analysis of the ecosystem experiments 4. The fish populations 5. Fish behavioral and community responses to manipulation 6. Roles of fish predation: piscivory and planktivory 7. Dynamics of the phantom midge: implications for zooplankton 8. Zooplankton community dynamics 9. Effects of predators and food supply and diel vertical migration of Daphnia 10. Zooplankton biomass and body size 11. Phytoplankton community dynamics 12. Metalimnetic phytoplankton 13. Primary production and its interactions with nutrients and light transmission 14. Heterotrophic microbial processes 15. Annual fossil record of food-web manipulation 16. Simulation models of the trophic cascade: predictions and evaluations 17. Synthesis and new directions Index.

Phytoplankton biomass and production in lakes tend to be increased by phosphorus input and decreased by grazing or high levels of colored, dissolved organic carbon (DOC). We estimated and compared the effects of these three factors by using data from three lakes that were manipulated during 1991–1995, and data from a reference lake. Multivariate probability distributions of chlorophyll or primary production, as predicted by P input rate, DOC, and grazer length, were fit to the data. All three factors had substantial effects on chlorophyll, primary production, and their variability. Comparable reductions in the mean and variance of chlorophyll and primary production were achieved by reducing P input rate from 5 to 0.5 mg m 2 d −l , increasing DOC from 5 to 17 mg C liter −l , or increasing mean crustacean length from 0.2 to 0.85 mm. The negative effect of mean crustacean length (an index of size‐selective predation) results from grazing by herbivorous zooplankton. The negative effect of DOC on primary producers could be explained by shading. The results suggest that natural variation in colored DOC concentrations is a major cause of variation in primary production.

Modeling nonpoint‐source phosphorus (P) loading from land to surface waters can be both complex and data intensive. Our goal was to develop a simple model that would account for spatial pattern in topography and land use using geographic information system (GIS) databases. We estimated areas of the watershed that strongly contributed to P loading by approximating overland flow, and modeled annual P loading by fitting three parameters to data obtained by stream monitoring. We calibrated the model using P loading data from two years of contrasting annual precipitation for Lake Mendota, a Wisconsin eutrophic lake in a watershed dominated by agriculture and urban lands. Land‐use scenarios were developed to estimate annual P loading from pre‐settlement and future land uses. As much as half of the Lake Mendota watershed did not contribute significantly to annual P loading. The greatest contribution to loading came from a heterogeneous riparian corridor that varied in width from 0.1 km to ≈ 6 km depending on topography and runoff conditions. We estimate that loading from pre‐settlement land use was one‐sixth of the loading from present land use. A future scenario, representing an 80% increase in existing urban land (from 9 to 16% of total watershed area, which would be reached in 30 yr with current land‐use trends), showed only modest increases in annual P loading but possible significant effects on water quality. If the watershed were to become entirely urbanized, P loading to the lake would double and potential effects on water quality would be severe. Changes in P loading were strongest with conversions of undisturbed vegetated lands, especially riparian areas, to either urban or agricultural uses. Variability in total annual rainfall leads to variability in the riparian area that affects P loading, with implications for policies intended to control nonpoint nutrient inputs.

Randomized intervention analysis (RIA) is used to detect changes in a manipulated ecosystem relative to an undisturbed reference system. It requires paired time series of data from both ecosystems before and after manipulation. RIA is not affected by non—normal errors in data. Monte Carlo simulation indicated that, even when serial autocorrelation was substantial, the true P value (i.e., from nonoautocorrelated data) was &lt;.05 when the P value from autocorrelated data was &lt;.01. We applied RIA to data from 12 lakes (3 manipulated and 9 reference ecosystems) over 3 yr. RIA consistently indicated changes after major manipulations and only rarely indicated changes in ecosystems that were not manipulated. Less than 3% of the data sets we analyzed had equivocal results because of serial autocorrelation. RIA appears to be a reliable method for determining whether a nonrandom change has occurred in a manipulated ecosystem. Ecological arguments must be combined with statistical evidence to determine whether the changes demonstrated by RIA can be attributed to a specific ecosystem manipulation.

The role of ecological expertise in policymaking is evolving. In fields such as engineering or medicine, longestablished professional standards guide the application of expertise in public decisionmaking. Professional ecologists, however, participate in decisionmaking in variable and changing ways. Some function as technicians, providing factual information used by decisionmakers; others as detectives, drawing attention to some previously unrecognized problem; and still others as advocates, adducing information designed to support a particular position.

Coarse woody debris (CWD) is a critical input from forested watersheds into aquatic ecosystems. Human activities often reduce the abundance of CWD in fluvial systems, but little is known about human impacts on CWD in lakes. We surveyed 16 north temperate lakes to assess relationships among CWD, riparian vegetation, and shoreline residential development. We found strong positive correlation between CWD density and riparian tree density (r 2 = 0.78), and strong negative correlation between CWD density and shoreline cabin density (r 2 = 0.71) at the whole‐lake scale. At finer spatial scales (e.g., between sampling plots), correlations between CWD and riparian vegetation were weaker. The strength of relationships between CWD and riparian vegetation was also negatively influenced by the extent of cabin development. Overall, there was significantly more CWD in undeveloped lakes (mean of 555 logs/km of shoreline) than in developed lakes. Within developed lakes, CWD density differed between forested sites (mean of 379 logs/km of shoreline) and cabin‐occupied sites (mean of 57 logs/km of shoreline). These losses of CWD will affect littoral communities in developed north temperate lakes for about two centuries. Because CWD is important littoral habitat for many aquatic organisms, zoning and lake management should aim to minimize further reductions of aquatic CWD and woody vegetation from lakeshore residences.

Term Ecological Research (LTER) program has now grown to 24 projects involving more than 1100 scientists.This article describes why the program exists and what it does.But the success of a scientific program cannot be measured by the number of sites or scientists involved in a project.Instead, the question must be, What have the LTER program and its longterm data sets contributed to the intellectual progress of ecological and environmental sciences?This special section takes direct aim at this question in six articles focusing on accomplishments of the LTER program in discrete areas of ecological research.The goal of each article is to highlight LTER contributions, not to provide an extensive review of an ecological topic.Readers should keep in mind that LTER projects make many other contributions than those described here.This article introduces the justification for long-term studies in ecology and describes the history of these studies, from Rothamsted in the 1840s through the International Biological Program of the 1970s to today's Hubbard Brook ecosystem study and LTER and other intensive research sites.Longterm projects make use of their year-to-century life span to identify the nonequilibrium and nonlinear characteristics of ecosystems and processes through monitoring and through experiments that may last decades.Much of this article is devoted to the LTER program today-its mission (box1), databases, cross-site synthesis activities, and cooperative research with government agencies-as well as the International LTER (ILTER) effort and LTER involvement with societal issues, including

EcologyVolume 82, Issue 4 p. 1065-1077 Article WHOLE-LAKE FERTILIZATION EFFECTS ON DISTRIBUTION OF PRIMARY PRODUCTION BETWEEN BENTHIC AND PELAGIC HABITATS Yvonne Vadeboncoeur, Yvonne Vadeboncoeur Department of Biological Sciences, University of Notre Dame, P.O. Box 369, Notre Dame, Indiana 46556 USA Present address: Department of Biology, McGill University, 1205 Avenue Docteur Penfield, Montreal, Quebec, Canada H3A 1B1. E-mail: [email protected]Search for more papers by this authorDavid M. Lodge, David M. Lodge Department of Biological Sciences, University of Notre Dame, P.O. Box 369, Notre Dame, Indiana 46556 USASearch for more papers by this authorStephen R. Carpenter, Stephen R. Carpenter Center for Limnology, University of Wisconsin, 680 N. Park Street, Madison, Wisconsin 53706 USASearch for more papers by this author Yvonne Vadeboncoeur, Yvonne Vadeboncoeur Department of Biological Sciences, University of Notre Dame, P.O. Box 369, Notre Dame, Indiana 46556 USA Present address: Department of Biology, McGill University, 1205 Avenue Docteur Penfield, Montreal, Quebec, Canada H3A 1B1. E-mail: [email protected]Search for more papers by this authorDavid M. Lodge, David M. Lodge Department of Biological Sciences, University of Notre Dame, P.O. Box 369, Notre Dame, Indiana 46556 USASearch for more papers by this authorStephen R. Carpenter, Stephen R. Carpenter Center for Limnology, University of Wisconsin, 680 N. Park Street, Madison, Wisconsin 53706 USASearch for more papers by this author First published: 01 April 2001 https://doi.org/10.1890/0012-9658(2001)082[1065:WLFEOD]2.0.CO;2Citations: 187 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract The perception that primary production in lakes is positively related to phosphorus loading is based almost entirely on studies of phytoplankton. This is partly because benthic and pelagic habitats in lakes are often treated as separate ecosystems, the processes of which can be evaluated independently. However, light and nutrients often limit primary producers in both benthic and pelagic habitats. We tested the hypothesis that reductions in light associated with increases in phytoplankton could cause compensatory decreases in benthic algal (periphyton) primary production. We monitored production of periphyton on sediments (epipelon), periphyton on wood (epixylon), and phytoplankton in four lakes in upper Michigan, USA, from 1991 to 1995. During the summers of 1993–1995, we stimulated phytoplankton production in three of the lakes by fertilizing with nitrogen and phosphorus (N:P ≥ 25 by atoms) at rates between 0.3 and 2.0 mg P·m−3·d−1. The response of periphyton to fertilization was substratum specific: epixylon increased with fertilization, but epipelon decreased. However, when area-specific production was extrapolated to the whole-lake scale, epixylon never constituted >4% of benthic primary production. Thus, the decline in epipelic production dominated the benthic response to fertilization. We also estimated whole-lake (epipelon + phytoplankton) primary production. Epipelic algae constituted 50–80% of whole-lake primary production at ambient nutrient levels. However, only 10–40% of primary production was benthic at the highest fertilization rates. The increase in whole-lake primary production caused by water column fertilization was greatly overestimated when we did not include the compensatory decline in epipelic algae as they were shaded by increases in phytoplankton concentrations. Citing Literature Volume82, Issue4April 2001Pages 1065-1077 RelatedInformation

Experimental manipulations of entire ecosystems have been conducted in lakes, catchments, streams, and open terrestrial and marine environments. Experiments have addressed applied problems of ecosystem management and complex responses of communities and ecosystems to perturbations. In the course of some experiments, environmental indicators and models have been developed and tested. Surprising results with implications for ecological understanding and management are common.

In many small aquatic ecosystems, watershed loading of organic C exceeds autochthonous primary production. Although this allochthonous organic C has long been thought of as refractory, multiple lines of evidence indicate that substantial portions are respired in the receiving aquatic ecosystem. To what extent does this terrestrial C support secondary production of invertebrates and fish? Do current models adequately trace the pathways of allochthonous and autochthonous C through the food web? We evaluated the roles of allochthonous and autochthonous organic C by manipulating 13 C content of dissolved inorganic C in a small, softwater, humic lake, thereby labeling autochthonous primary production for about 20 d. To ensure rapid and sufficient uptake of inorganic 13 C, we enriched the lake with modest amounts of N and P. We constructed a carbon flow model based on the ambient and manipulated levels of 13 C in C compartments in the lake, along with information on key rate processes. Despite the short nature of this experiment, several results emerged. (1) Fractionation of photosynthetically assimilated 13 C‐CO 2 by phytoplankton (ɛ) is lower (~6‰) than physiologic models would estimate (~20‰). (2) Bacteria respire, but do not assimilate, a large amount of terrestrially derived dissolved organic C (DOC) and pass little of this C to higher trophic levels. (3) The oxidation of terrestrial DOC is the major source of dissolved inorganic C in the lake. (4) Zooplankton production, a major food of young‐of‐year fishes, is predominantly derived from current autochthonous carbon sources under the conditions of this experiment.

The annual record of fossil pigments and zooplankton was compared with detailed contemporaneous records from two manipulated lakes from 1940 to 1986. Annually resolved sedimentary records accurately monitored known changes inplankton communities, identified periods of trophic change, and proved a powerful tool for examining long‐term, complex interactions. Both Paul and Peter Lakes underwent the same three complete changes in their fish assemblages (trout, cyprinid, bass), and Peter Lake received repeated inputs of lime. Alterations in fish community composition produced long‐lived changes in zooplankton communities that cascaded to the microbial level of the food web. Liming, in concert with trophic changes, caused distinctive phytoplankton dynamics in Peter Lake. Paleolimnological data recorded all major plankton dynamics known from coeval limnological data. Specifically, the sediment record showed transitions in cladoceran size structure and species composition, changes in water clarity resulting from both food web and chemical manipulations that affected vertical zonation of primary producers, and changes in absolute abundance of all algal divisions except dinoflagellates. Undegraded Chl a indicated deep blooms and, in conjunction with Chl c , fucoxanthin and β ‐carotene, indicated metalimnetic chrysophytes. Transient (2–3 yr) nonselective increases in sedimentation corresponded with increases in grazing rates. Isorenieratene indicated overlap of photic and anoxic zones, revealing changes in transparency and conditions for pigment preservation.

Ecology has a key role in our understanding of the benefits that humans obtain from ecosystems (i.e. ecosystem services). Ecology can also contribute to developing environmentally sound technologies, markets for ecosystem services and approaches to decision-making that account for the changing relationship between humans and ecosystems. These contributions involve basic ecological research on, for example, the resilience of ecosystem services or relationships of ecosystem change to natural disasters. Much of the necessary work involves interdisciplinary collaboration among ecologists, social scientists and decision makers. As we discuss here, ecology should help formulate positive, plausible visions for relationships of society and ecosystems that can potentially sustain ecosystem services for long periods of time.

Larvae of Aedes triseriatus mosquitoes feed on microbes that decompose leaf litter in tree—hole ecosystems. Scanning electron micrographs indicate that browsing by mosquitoes substantially reduces microbial abundance on decaying leaves. Experiments using laboratory microcosms demonstrate that increased larval density decreases larval survivorship, pupation rates, pupal biomass, and total yield. Rapidly decomposing leaf litter (sugar maple) supports more mosquito growth than slowly decomposing litter (beech and black oak). In our experiments, mosquito yield was apparently regulated by larval density and detrital dynamics.

The purpose of this paper is to provide ecologists and resource managers with a sense of where the economic science of ecosystem valuation has come from and where it might go in the future. To accomplish this, the paper provides a comprehensive synthesis of peer-reviewed economic data on surface freshwater ecosystems in the United States and examines major accomplishments and gaps in the literature. Economic value has been assigned to nonmarket goods and services provided by surface freshwater systems in the United States by 30 published, refereed articles in the scientific literature from 1971 to 1997. These studies have used variations of three approaches for a quantitative assessment of economic value: travel cost methods, hedonic pricing methods, and contingent valuation methods. To determine the economic value of nonmarket ecosystem goods and services, each method focuses on a different aspect of social benefit associated with lakes, streams, rivers, and wetlands. Valuation methodologies work from different underlying assumptions while possessing unique limitations and uncertainties. Dollar benefit estimates derived for nonmarket freshwater ecosystem goods and services from these studies tend to be specific to a particular method, ecosystem, and socioeconomic circumstance. Creative interdisciplinary research is needed on the quantitative measurement of surface freshwater ecosystem goods and service values, the relation of these values to key limnological variates, and communication of limnological insights to the public and social scientists in ways that facilitate and improve future management and research.