Ecosystem service

This report summarizes the results of a two-year study of the economic value of New Jersey's natural capital. Natural capital consists of those components of the natural environment that provide aa long-term stream of benefits to individual people and to society as a whole; the value of natural capital is defined in this report as the present value of that benefit stream. Many of the benefits provided by natural capital come from ecological systems ("ecosystems"); an ecosystem is a dynamic complex of plant, animal, and microorganism communities and their nonliving environment, all interacting as a functional unit.

Human societies derive many essential goods from natural ecosystems, including seafood, game animals, fodder, fuelwood, timber, and pharmaceutical products. These goods represent important and familiar parts of the economy. What has been less appreciated until recently is that natural ecosystems also perform fundamental life-support services without which human civilizations would cease to thrive. These include the purification of air and water, detoxification and decomposition of wastes, regulation of climate, regeneration of soil fertility, and production and maintenance of biodiversity, from which key ingredients of our agricultural, pharmaceutical, and industrial enterprises are derived. This array of services is generated by a complex interplay of natural cycles powered by solar energy and operating across a wide range of space and time scales. The process of waste disposal, for example, involves the life cycles of bacteria as well as the planet-wide cycles of major chemical elements such as carbon and nitrogen. Such processes are worth many trillions of dollars annually. Yet because most of these benefits are not traded in economic markets, they carry no price tags that could alert society to changes in their supply or deterioration of underlying ecological systems that generate them. Because threats to these systems are increasing, there is a critical need for identification and monitoring of ecosystem services both locally and globally, and for the incorporation of their value into decision-making processes.

An increasing amount of information is being collected on the ecological and socio-economic value of goods and services provided by natural and semi-natural ecosystems. However, much of this information appears scattered throughout a disciplinary academic literature, unpublished government agency reports, and across the World Wide Web. In addition, data on ecosystem goods and services often appears at incompatible scales of analysis and is classified differently by different authors. In order to make comparative ecological economic analysis possible, a standardized framework for the comprehensive assessment of ecosystem functions, goods and services is needed. In response to this challenge, this paper presents a conceptual framework and typology for describing, classifying and valuing ecosystem functions, goods and services in a clear and consistent manner. In the following analysis, a classification is given for the fullest possible range of 23 ecosystem functions that provide a much larger number of goods and services. In the second part of the paper, a checklist and matrix is provided, linking these ecosystem functions to the main ecological, socio-cultural and economic valuation methods. : S 0 9 2 1 -8 0 0 9 ( 0 2 ) 0 0 0 8 9 -7

Mesophotic coral reefs, reefs at depths of 30 m to 150 m, are receiving renewed interest from coral reef scientists and managers because they are linked physically and biologically to their shallow water counterparts, have the potential to be refugia for shallow coral reef taxa such as coral and sponges, and can be a source of larvae that could contribute to the resiliency of shallow water reefs. Here we review what is currently known about how mesophotic reef communities are structured and identify critical areas where new information is needed. The review covers two primary taxa, coral and sponges, where a majority of the ecological work on mesophotic coral reefs has been done, and physical processes (e.g., the attenuation of visible irradiance and internal waves) that exert significant abiotic control on the structure of these deep fore reef communities. Understanding the ecology of mesophotic coral reefs, and the connectivity between them and their shallow water counterparts, should be a primary focus of future reef studies as the worldwide degradation of shallow coral reefs, and the ecosystem services they provide, continues.

Payments for Ecosystem Services (PES) economically reward resource managers for the provision of ecosystem services and are thus characterised by (i) an ecological function subject to trade; (ii) the establishment of a standard unit of exchange; (iii) and supply, demand and intermediation flows between those who sell and buy ecosystem services. This paper departs from the term commodity fetishism, broadly understood as the masking of the social relationships underlying the process of production, to illuminate three invisibilities in the commodification of ecosystem services. Firstly, we argue that narrowing down the complexity of ecosystems to a single service has serious technical difficulties and ethical implications on the way we relate to and perceive nature. Secondly, the commodification of ecosystem services denies the multiplicity of values which can be attributed to these services, since it requires that a single exchange-value is adopted for trading. Finally, we suggest that the process of production, exchange and consumption of ecosystem services is characterised by power asymmetries which may contribute to reproducing rather than addressing existing inequalities in the access to natural resources and services.

Invertebrates play significant, but largely ignored, roles in the delivery of ecosystem services by soils at plot and landscape scales. They participate actively in the interactions that develop in soil among physical, chemical and biological processes. We show that soils have all the attributes of self-organized systems as proposed by Perry (Trends Ecol. Evol. 10 (1995) 241) and detail the scales at which invertebrates operate and the different kinds of ecosystem engineering that they develop. This comprehensive analysis of invertebrate activities shows that they may be the best possible indicators of soil quality. They should also be considered as a resource that needs to be properly managed to enhance ecosystem services provided by agro-ecosystems.

During the last 50 years, agricultural intensification has caused many wild plant and animal species to go extinct regionally or nationally and has profoundly changed the functioning of agro-ecosystems. Agricultural intensification has many components, such as loss of landscape elements, enlarged farm and field sizes and larger inputs of fertilizer and pesticides. However, very little is known about the relative contribution of these variables to the large-scale negative effects on biodiversity. In this study, we disentangled the impacts of various components of agricultural intensification on species diversity of wild plants, carabids and ground-nesting farmland birds and on the biological control of aphids.

Among the main effects of human activities on the environment are land use and resulting land cover changes. Such changes impact the capacity of ecosystems to provide goods and services to the human society. This supply of multiple goods and services by nature should match the demands of the society, if self-sustaining human-environmental systems and a sustainable utilization of natural capital are to be achieved. To describe respective states and dynamics, appropriate indicators and data for their quantification, including quantitative and qualitative assessments, are needed. By linking land cover information from, e.g. remote sensing, land survey and GIS with data from monitoring, statistics, modeling or interviews, ecosystem service supply and demand can be assessed and transferred to different spatial and temporal scales. The results reveal patterns of human activities over time and space as well as the capacities of different ecosystems to provide ecosystem services under changing land use. Also the locations of respective demands for these services can be determined. As maps are powerful tools, they hold high potentials for visualization of complex phenomena. We present an easy-to-apply concept based on a matrix linking spatially explicit biophysical landscape units to ecological integrity, ecosystem service supply and demand. An exemplary application for energy supply and demand in a central German case study region and respective maps for the years 1990 and 2007 are presented. Based on these data, the concept for an appropriate quantification and related spatial visualization of ecosystem service supply and demand is elaborated and discussed.

Experiments suggest that biomass-derived black carbon (biochar) affects microbial populations and soil biogeochemistry. Both biochar and mycorrhizal associations, ubiquitous symbioses in terrestrial ecosystems, are potentially important in various ecosystem services provided by soils, contributing to sustainable plant production, ecosystem restoration, and soil carbon sequestration and hence mitigation of global climate change. As both biochar and mycorrhizal associations are subject to management, understanding and exploiting interactions between them could be advantageous. Here we focus on biochar effects on mycorrhizal associations. After reviewing the experimental evidence for such effects, we critically examine hypotheses pertaining to four mechanisms by which biochar could influence mycorrhizal abundance and/or functioning. These mechanisms are (in decreasing order of currently available evidence supporting them): (a) alteration of soil physico-chemical properties; (b) indirect effects on mycorrhizae through effects on other soil microbes; (c) plant-fungus signaling interference and detoxification of allelochemicals on biochar; and (d) provision of refugia from fungal grazers. We provide a roadmap for research aimed at testing these mechanistic hypotheses.

Agroforestry, the purposeful growing of trees and crops in interacting combinations, began to attain prominence in the late 1970s, when the international scientific community embraced its potentials in the tropics and recognized it as a practice in search of science. During the 1990s, the relevance of agroforestry for solving problems related to deterioration of family farms, increased soil erosion, surface and ground water pollution, and decreased biodiversity was recognized in the industrialized nations too. Thus, agroforestry is now receiving increasing attention as a sustainable land-management option the world over because of its ecological, economic, and social attributes. Consequently, the knowledge-base of agroforestry is being expanded at a rapid rate as illustrated by the increasing number and quality of scientific publications of various forms on different aspects of agroforestry.

Greenspace is an important part of complex urban ecosystems and provides significant ecosystem services. It benefits urban communities environmentally, esthetically, recreationally and economically. Beijing Province is in north of China, and has a total area of 16,807.8 km 2 and a population of about 13.8 million. This paper aims to develop a comprehensive conceptual framework for urban greening of Beijing Province based on landscape ecological principles. It attempts to answer how to establish an urban greening plan at the regional, city and neighborhood levels to achieve long-term sustainability. At the regional level, a big natural and semi-natural forest area in the northwest and an ecological buffer belt in the southeast are planned to protect the environmental quality of Beijing and provide habitats for wildlife. At the city level, a green network system of green wedges, parks and green corridors has been proposed. This green network helps to limit future urban expansion, improve urban environmental quality and serve as habitats and migration routes for wildlife. At the neighborhood level, green extensions and connections of riverside greenway, road greenway, parks and vertical greening permeate into the built-up areas. They provide open space close to residential areas and offer places for recreation. This three-level green system constitutes an integrated ecological network for urban sustainable development of Beijing. For future development of Beijing, urban parks, forestry, agriculture, water and infrastructure should be planned and designed in an integrated way. After this greenspace plan is legislated and completely realized, Beijing will develop an interconnected and integrated network of urban greenspaces. It has the prospect of achieving the aim of "Green Olympic City 2008" and the long-term goal of developing Beijing towards an "Eco-City".

The purpose of this special issue is to elucidate concepts of value and methods of valuation that will assist in guiding human decisions vis-à-vis ecosystems. The concept of ecosystem service value can be a useful guide when distinguishing and measuring where trade-offs between society and the rest of nature are possible and where they can be made to enhance human welfare in a sustainable manner. While win-win opportunities for human activities within the environment may exist, they also appear to be increasingly scarce in a 'full' global ecological-economic system. This makes valuation all the more essential for guiding future human activity. This paper provides some history, background, and context for many of the issues addressed by the remaining papers in this special issue. Its purpose is to place both economic and ecological meanings of value, and their respective valuation methods, in a comparative context, highlighting strengths, weakness and addressing questions that arise from their integration.

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Microclimatic design requires knowledge of the climate conditions, understanding of the ways that landscape elements affect microclimate and methods of applying this knowledge through landscape design to create microclimates that are comfortable for people and minimize the energy use of buildings. In this article it will be introduced the most important components and characteristics of microclimatic landscape design. Green roof ecosystem services in urban areas will be also introduced and future research needs will be mentioned.

Background / Purpose: The declining health of marine ecosystems around the world suggests that the current structure of sectoral governance is inadequate to successfully sustain human uses of the ocean and support healthy coastal and ocean ecosystems. One possible solution to this problem is ecosystem-based marine spatial planning (EB-MSP), which aims to maintain sustainable uses, healthy ecosystems, and the delivery of ecosystem services. In order to achieve these goals, EB-MSP must be based on specific, measureable ecological principles that articulate scientifically recognized attributes of healthy, functioning ecosystems that can be incorporated into a decision-making framework. Main conclusion: We present recommendations based on a synthesis of previously suggested principles, along with recommendations generated by a group of twenty marine scientists with diverse backgrounds and perspectives on MSP. The four ecological principles – maintaining or restoring (1) native species d...

Given the extent of land use and land cover change by humans on a global scale, conservation efforts have increasingly focused on restoring degraded ecosystems to provide ecosystem services and biodiversity. Many examples in the tropics and elsewhere, however, show that some ecosystems recover rapidly without human intervention which begs the question of in which cases and to what extent humans should actively work to facilitate ecosystem recovery. We recommend that all land managers consider a suite of ecological and human factors before selecting a restoration approach. Land managers should first consider what the likely outcome of a passive restoration (natural regeneration) approach would be based on the natural ecosystem resilience, past land-use history, and the surrounding landscape matrix. They should also identify the specific goals of the project and assess the resources available. Conducting these analyses prior to selecting restoration approaches should result in a more efficient use of restoration resources both within and among projects and should maximize the success of restoration efforts.

Short-term movements of fishes and decapods can lead to regular changes in biomass, diversity, mortality, predation, and flux of energy between adjacent ecosystems. At low latitudes the day-night cycle is relatively stable and uniformly affects activity rhythms of marine organism at all longitudes. In contrast, tidal ranges and tidal types differ significantly between coasts and regions. On coasts with weak tides, twilight migrations connect adjacent habitats. On tidal coasts, migrations are tightly coupled to the interactive effect of the diel and tidal cycles which results in complex but predictable patterns of change within and between ecosystems. Diel and tidal migrations share several similarities (connection of resting and feeding sites, sequence of species and size groups, site fidelity, homing, constant pathways). The spring-neap tide cycle and its interaction with the diel cycle is a key factor influencing regular short-term variations on tidal coasts. The home range of a species on a macrotidal coast may be an order of magnitude greater than that of conspecifics from a microtidal coast, suggesting a need for larger marine parks on macrotidal coasts. Regional comparisons, e.g., between the Caribbean and the Indo-West Pacific, often disregard the significant tidal differences inherent to the ecosystems. It is suggested here that broad-scale comparisons must be redefined; regional comparisons should focus on geographical regions with similar tidal regimes, or on systems with different tidal regimes but with similar species communities.

The concept of ecosystem services is increasingly being used by scientists and policy makers. However, most studies in this area have focussed on factors that regulate ecosystem functions (i.e. the potential to deliver ecosystem services) or the supply of ecosystem services. In contrast, demand for ecosystem services (i.e. the needs of beneficiaries) or understanding of the concept and the relative ranking of different ecosystem services by beneficiaries has received limited attention. The aim of this study was to identify in three European mountain regions the ecosystem services of grassland that different stakeholders identify (which ecosystem services for whom), the relative rankings of these ecosystem services, and how stakeholders perceive the provision of these ecosystem services to be related to agricultural activities. We found differences:

ABSTRACT Managing urban green space as part of an ongoing social-ecological transformation poses novel governance issues, particularly in post-industrial settings. Urban green spaces operate as small-scale nodes in larger networks of ecological reserves that provide and maintain key ecosystem services such as pollination, water retention and infiltration, and sustainable food production. In an urban mosaic, a myriad of social and ecological components factor into aggregating and managing land to maintain or increase the flow of ecosystem services associated with green spaces. Vacant lots (a form of urban green space) are being repurposed for multiple functions, such as habitat for biodiversity, including arthropods that provide pollination services to other green areas; to capture urban runoff that eases the burden on ageing wastewater systems and other civic infrastructure; and to reduce urban heat island effects. Because of the uncertainty and complexities of managing for ecosystem services in urban settings, we advocate for a governance approach that is adaptive and iterative in nature—adaptive governance—to address the ever changing social order underlying postindustrial cities and offer the rise of land banks as an example of governance innovation.

We present a GIS method to interpret qualitatively expressed socio-economic scenarios in quantitative map-based terms. (i) We built scenarios using local stakeholders and experts to define how major land cover classes may change under different sets of drivers; (ii) we formalised these as spatially explicit rules, for example agriculture can only occur on certain soil types; (iii) we created a future land cover map which can then be used to model ecosystem services. We illustrate this for carbon storage in the Eastern Arc Mountains of Tanzania using two scenarios: the first based on sustainable development, the second based on 'business as usual' with continued forestewoodland degradation and poor protection of existing forest reserves. Between 2000 and 2025 4% of carbon stocks were lost under the first scenario compared to a loss of 41% of carbon stocks under the second scenario. Quantifying the impacts of differing future scenarios using the method we document here will be important if payments for ecosystem services are to be used to change policy in order to maintain critical ecosystem services.

Conservation should benefit ecosystems, nonhuman organisms, and current and future human beings. Nevertheless, tension among these goals engenders potential ethical conflicts: conservationists' true motivations may differ from the justifications they offer for their activities, and conservation projects have the potential to disempower and oppress people. We reviewed the promise and deficiencies of integrating social, economic, and biological concerns into conservation, focusing on research in ecosystem services and efforts in community-based conservation. Despite much progress, neither paradigm provides a silver bullet for conservation's most pressing problems, and both require additional thought and modification to become maximally effective. We conclude that the following strategies are needed to make conservation more effective in our human-dominated world. (1) Conservation research needs to integrate with social scholarship in a more sophisticated manner. (2) Conservation must be informed by a detailed understanding of the spatial, temporal, and social distributions of costs and benefits of conservation efforts. Strategies should reflect this understanding, particularly by equitably distributing conservation's costs. (3) We must better acknowledge the social concerns that accompany biodiversity conservation; accordingly, sometimes we must argue for conservation for biodiversity's sake, not for its direct human benefits.

There is a growing body of evidence to suggest that the simplification of land uses associated with a strong dependence on agrochemical inputs is decreasing environmental quality, threatening biodiversity, and increasing the likelihood of pest outbreaks. The development of farming systems with greater reliance on ecosystem services, such as biological control of insect pests, should increase the sustainability of agroecosystems. However, the factors responsible for the maintenance or enhancement of natural pest control remain unclear. The goal of this review is, therefore, to expose which elements, from the field to the landscape scale, influence natural enemy populations and pest regulation. We present here the principal effects of seminatural habitats, farming systems, and crop management on the abundance of insect pests and their biological control, with a view to evaluating their relative importance and identifying key elements that regulate natural pest control interactions. Because of the range of spatial and temporal scales experienced by these organisms, we advocate, in studies investigating trophic relations and biological pest control, a clear description of cropping systems and an explicit consideration of seminatural habitats and more generally of the surrounding landscape. Through this review, we also indicate gaps in knowledge and demonstrate the interest of linking agronomy and landscape ecology to understand trophic interactions, maximize natural pest control, and limit pesticide applications. Quantifying the relative importance of both local and landscape scales is a fundamental step in the design and assessment of ecologically sound integrated pest management strategies for farmers.

A literature survey identified 403 primary research publications that investigated the ecological effects of invasive alien insects and/or the mechanisms underlying these effects. The majority of these studies were published in the last 8 years and nearly two-thirds were carried out in North America. These publications concerned 72 invasive insect species, of which two ant species, Solenopsis invicta and Linepithema humile, accounted for 18% and 14% of the studies, respectively. Most publications investigated effects on native biodiversity at population or community level. Genetic effects and, to a lesser extent, effects on ecosystem services and processes were rarely explored. We review the effects caused by different insect invaders according to: their ecosystem roles, i.e. herbivores, predators, parasites, parasitoids and pollinators; the level of biological organisation at which they occur; and the direct and indirect mechanisms underlying these effects. The best documented effects occur in invasive ants, Eurasian forest herbivores invasive in North America, and honeybees. Impacts may occur through simple trophic interactions such as herbivory, predation or parasitism. Alien species may also affect native species and communities through more complex mechanisms such as competition for resources, disease transmission, apparent competition, or pollination disruption, among others. Finally, some invasive insects, particularly forest herbivores and ants, are known to affect ecosystem processes through cascading effects. We identify biases and gaps in our knowledge of ecological effects of invasive insects and suggest further opportunities for research.

Ever increasing and diverse use of the marine environment is leading to human-induced changes in marine life, habitats and landscapes, making necessary the development of marine policy that considers all members of the user community and addresses current, multiple, interacting uses. Taking a systems approach incorporating an understanding of The Ecosystem Approach, we integrate the DPSIR framework with ecosystem services and societal benefits, and the focus this gives allows us to create a specific framework for supporting decision making in the marine environment. Based on a linking of these three concepts, we present a set of basic postulates for the management of the marine environment and emphasise that these postulates should hold for marine management to be achieved. We illustrate these concepts using two case studies: the management of marine aggregates extraction in UK waters and the management of marine biodiversity at Flamborough Head, UK. the management of the marine environment which integrate the concepts, and (3) to provide a specific framework for supporting decision making in the marine environment.

Cultural norms for landscape appearance may affect preferences for and adoption of ecological design in exurban residential landscapes, a rapidly growing land use that covers a larger area than all other urban land uses in America combined. We conducted an image-based web survey of 494 southeast Michigan exurban homeowners to investigate the influence of implicit neighborhood norms as well as broader cultural norms on individual preferences for six alternative front yard designs ranging from conventional yards dominated by mown turf to mature native woodlands and native prairie garden designs. Respondents were randomly assigned to see images of one of three types of nearby neighbors' yards: all conventional, all ecologically innovative, or a mix. They rated front yard design alternatives in one of these three neighborhood contexts. Both broad cultural norms for conventional front yards and neighborhood norms significantly affected homeowners' preference for their own yards. However, neighborhood norms most dramatically affected preference: the rank of the most conventional and most ecologically beneficial front yard designs was reversed depending upon the design of nearby neighbors' yards. We conclude that efforts to introduce ecologically innovative designs to metropolitan residential landscapes should approach change at the neighborhood scale in order to enhance initial success and long term cultural sustainability. We also note that individuals who innovate on their own properties may want to enlist nearby neighbors in similar innovations to create a threshold of cultural sustainability.

Habitat destruction and fragmentation are the root causes of many conservation problems. We conducted a literature survey and canvassed the ecological community to identify experimental studies of terrestrial habitat fragmentation and to determine whether consistent themes were emerging from these studies. Our survey revealed 20 fragmentation experiments worldwide. Most studies focused on effects of fragmentation on species richness or on the abundance(s) of particular species. Other important themes were the effect of fragmentation in interspecific interactions, the role of corridors and landscape connectivity in individual movements and species richness, and the influences of edge effects on ecosystem services. Our comparisons showed a remarkable lack of consistency in results across studies, especially with regard to species richness and abundance relative to fragment size. Experiments with arthropods showed the best fit with theoretical expectations of greater species richness on larger fragments. Highly mobile taxa such as birds and mammals, early-successional plant species, long-lived species, and generalist predators did not respond in the "expected" manner. Reasons for these discrepancies included edge effects, competitive release in the habitat fragments, and the spatial scale of the experiments. One of the more consistently supported hypotheses was that movement and species richness are positively affected by corridors and connectivity, respectively. Transient effects dominated many systems; for example, crowding of individuals on fragments commonly was observed after fragmentation, followed by a relaxation toward lower abundance in subsequent years. The three long-term studies ( у 14 years) revealed strong patterns that would have been missed in short-term investigations. Our results emphasize the wide range of species-specific responses to fragmentation, the need for elucidation of behavioral mechanisms affecting these responses, and the potential for changing responses to fragmentation over time.

1 Pesticides are considered a threat to pollinators but little is known about the potential impacts of their widespread use on pollinators. Less still is known about the impacts on pollination, comprising the ecosystem service that pollinators provide to wildflowers and crops. 2 The present study measured flower visitation and pollination in an agricultural landscape, by placing potted flowering plants (Petunia sp.) in vine fields sprayed with a highly toxic insecticide (fenitrothion). During two sampling rounds, insect visitors to the petunias were observed and measures of pollination were recorded by counting and weighing seeds. 3 In the earlier sampling round, a lower species richness of insect visitors was observed in fields that had received an early application of insecticide. No negative impacts were found from later applications. The results obtained suggest a greater potential harm to insect pollinators and flower visitation as a result of insecticide application early in the season. 4 No reduction in pollination was found in fields that received an early insecticide application. Pollination was greater with two insecticide applications between sampling rounds rather than one application. 5 In the present study system, insecticide application had a negative effect on pollinators but a possible positive effect on pollination services. In some cases, it may be that actions for conserving biodiversity will not benefit pollination services to all plants.

NATURE CLIMATE CHANGE | VOL 1 | NOVEMBER 2011 | www.nature.com/natureclimatechange 401 C limate change is a serious threat to Earth's ecosystems. Increased greenhouse gases and the associated rise in temperature have been implicated in melting glaciers, rising sea levels, acidification of marine and freshwater systems, increased ultraviolet-B radiation and increased fire frequency. The past century has seen a nearly 1 °C rise in global average temperature 1 , with up to 7 °C of warming predicted by 2100 (ref. 2). Global warming has already led to significant shifts in the distribution, phenology and behaviour of organisms 3-5 . Of 1,700 plant, insect, amphibian and bird species examined in a review by Parmesan and Yohe 5 , 80% had a poleward range shift of 6.1 km per decade, and 87% had an advancement in the timing of phenological events, such as breeding or flowering, of 2.3 days per decade. Such changes in distribution and phenology in response to climate change have received much attention in the literature, but only recently have studies begun to address the effects of climate change on development and growth. For many organisms, development and growth, and thus organism size, are affected by temperature and water availability 6-8 . The increased temperatures and variability of precipitation associated with climate change are likely to influence the size of organisms, from primary producers to top predators 9-11 . However, as we discuss below, the degree to which organism size is affected by temperature or precipitation variability is likely to vary within and between taxa, which could disrupt ecosystem functioning. Here, we briefly summarize the changes in organism size that are most likely a result of climate change and increased carbon dioxide levels, and theorize on reasons for the observed patterns of size declines. We present evidence from fossil records, experimental and geographic comparisons, and recent studies implicating current climate change in the shrinking size of organisms. We discuss the mechanisms that are most likely to be contributing to the observed patterns, exceptions to these trends and implications for biodiversity. Ultimately, our opinion is that this effect will become much more pervasive, and that research should focus on quantifying size trends more broadly, and identifying proximate and ultimate drivers of size declines.

In Spring 1991, the U.S. Environmental Protection Agency convened an expert group of ecologists, economists and other social scientists for the purpose of advancing the state of the art of ecosystem valuation methods. This Ecosystem Valuation Forum was organized as a dialogue because it has been clear from the outset that agreement even on the meaning of the term "ecosystem valuation" could not be taken for granted. Individuals from diverse disciplines, and from industry, environmental groups and government agencies disagree about what information about ecosystem services is needed, how it should be used and, therefore, what would constitute an advance in the methods that analysts should employ. The Forum discussed the varied ways in which experts from different disciplines approach valuation, what ecosystem attributes or services are important to value, and the factors that complicate the task of assigning values to ecosystem attributes. The Forum placed particular importance on approaching the problem of ecosystem valuation from the perspective of decision makers. Therefore, members discussed the variety of decision makers who might need valuation information, the controversy over where balancing decisions about costs and benefits should be made, and the implications for what information is needed * Corresponding author. 1 Current address: Louis Berger, Inc., Washington, DC, USA. 0921-8009/95/$09.50 © 1995 Elsevier Science B.V. All rights reserved SSDI 0921-8009(95)00021-6 74 G. Bingham et aL / Ecological Economics 14 (1995) [73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90] within different institutional constraints. In addition, agency decision makers operate under real time and resource constraints. Thus, the Forum discussed the need to develop protocols that would guide analysts in a search for decisive information. The Forum concluded that the time is ripe for making new progress in solving some of these problems, while acknowledging that it may not be possible to develop a single unifying definition of value. Instead, the goal would be to understand how various concepts of value are structured, how they relate to each other, and how they can guide us toward a more integrated valuation process. The Forum recommended that next steps in addressing these issues be organized around case studies, particularly those that would enable researchers to improve linkages between ecological and economic methods and to develop improved protocols for valuation studies.