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2 Ecosystems and Their Services

2 Ecosystems and Their ServicesEXECUTIVE SUMMARY An ecosystem is a dynamic complex of plant, animal, and microorganism com-munities and the nonliving environment, interacting as a functional unit. Hu-mans are an integral part of Ecosystems . A well-defined ecosystem has strong interactions among its components andweak interactions across its boundaries. A useful ecosystem boundary is theplace where a number of discontinuities coincide, for instance in the distribu-tion of organisms, soil types, drainage basins, or depth in a water body. At alarger scale, regional and even globally distributed Ecosystems can be evalu-ated based on a commonality of basic structural units. Ecosystem Services are the benefits people obtain from Ecosystems .

2 Ecosystems and Their Services EXECUTIVE SUMMARY An ecosystem is a dynamic complex of plant, animal, and microorganism com- munities and the nonliving environment, interacting as a functional unit. Hu-mans are an integral part of ecosystems. A well-defined ecosystem has strong interactions among its components and weak interactions across its boundaries.

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Transcription of 2 Ecosystems and Their Services

1 2 Ecosystems and Their ServicesEXECUTIVE SUMMARY An ecosystem is a dynamic complex of plant, animal, and microorganism com-munities and the nonliving environment, interacting as a functional unit. Hu-mans are an integral part of Ecosystems . A well-defined ecosystem has strong interactions among its components andweak interactions across its boundaries. A useful ecosystem boundary is theplace where a number of discontinuities coincide, for instance in the distribu-tion of organisms, soil types, drainage basins, or depth in a water body. At alarger scale, regional and even globally distributed Ecosystems can be evalu-ated based on a commonality of basic structural units. Ecosystem Services are the benefits people obtain from Ecosystems .

2 Theseinclude provisioning Services such as food and water; regulating Services suchas flood and disease control; cultural Services such as spiritual, recreational,and cultural benefits; and supporting Services , such as nutrient cycling, thatmaintain the conditions for life on Earth. Biodiversity is the variability among living organisms. It includes diversity withinand among species and diversity within and among Ecosystems . Biodiversity isthe source of many ecosystem goods, such as food and genetic resources, andchanges in biodiversity can influence the supply of ecosystem Services . People seek many Services from Ecosystems and thus perceive the conditionof an ecosystem in relation to its ability to provide desired Services .

3 The abilityof Ecosystems to deliver Services can be assessed by a variety of qualitativeand quantitative methods. An assessment of the condition of Ecosystems , the provision of Services , andtheir relation to human well-being requires an integrated approach. This en-ables a decision process to determine which service or set of Services is val-ued most highly and how to develop approaches to maintain Services bymanaging the system of species populate Earth. The vast majority gain energy to sup-port Their metabolism either directly from the sun, in the case of plants,or, in the case of animals and microbes, from other organisms throughfeeding on plants, predation, parasitism, or decomposition.

4 In the pursuitof life and through Their capacity to reproduce, organisms use energy, , 6:19 AM4950 Ecosystems and Human Well-being: A Framework for Assessmentter, and nutrients. Terrestrial plants obtain water principally from soil,while animals get it mainly from free-standing water in the environmentor from Their food. Plants obtain most of Their nutrients from the soil orwater, while animals tend to derive Their nutrients from other are the most versatile, obtaining nutrients from soil, wa-ter, Their food, or other organisms. Organisms interact with one anotherin many ways, including competitive, predatory, parasitic, and facilitativeways, such as pollination, seed dispersal, and the provision of fundamental linkages among organisms and Their physical andbiological environment constitute an interacting and ever-changing sys-tem that is known as an ecosystem.

5 Humans are a component of theseecosystems. Indeed, in many regions they are the dominant dominant or not, however, humans depend on ecosystem prop-erties and on the network of interactions among organisms and withinand among Ecosystems for sustenance, just like all other organisms interact with each other and Their physical environment,they produce, acquire, or decompose biomass and the carbon-based or or-ganic compounds associated with it. They also move minerals from the wa-ter, sediment, and soil into and among organisms, and back again into thephysical environment. Terrestrial plants also transport water from the soilinto the atmosphere. In performing these functions, they provide materialsto humans in the form of food, fiber, and building materials and they con-tribute to the regulation of soil, air, and water relationships sound simple in general outline, but they are infact enormously complex, since each species has unique requirements forlife and each species interacts with both the physical and the biologicalenvironment.

6 Recent perturbations, driven principally by human activi-ties, have added even greater complexity by changing, to a large degree,the nature of those Boundaries and CategoriesAlthough the notion of an ecosystem is ancient, Ecosystems first became aunit of study less than a century ago, when Arthur Tansley provided aninitial scientific conceptualization in 1935 (Tansley 1935) and RaymondLindeman did the first quantitative study in an ecosystem context in theearly 1940s (Lindeman 1942). The first textbook built on the ecosystemconcept, written by Eugene Odum, was published in 1953 (Odum 1953).Thus the ecosystem concept, so central to understanding the nature of lifeon Earth, is actually a relatively new research and management , 6:19 AM50 Ecosystems and Their Services 51 Tansley s formulation of an ecosystem included not only the organ-ism-complex, but also the whole complex of physical factors forming whatwe call the environment (Tansley 1935:299).

7 He noted that Ecosystems are of the most varied kinds and sizes. The main identifying feature of anecosystem is that it is indeed a system; its location or size is important, Tansley and subsequent developments, we chose to use thedefinition of an ecosystem adopted by the Convention on Biological Di-versity (CBD): a dynamic complex of plant, animal and micro-organismcommunities and Their nonliving environment interacting as a functionalunit (United Nations 1992:Article 2).Biodiversity and Ecosystems are closely related concepts. Biodiversityis defined by the CBD as the variability among living organisms from allsources including, inter alia, terrestrial, marine and other aquatic ecosys-tems and the ecological complexes of which they are part; this includesdiversity within species, between species and of Ecosystems (United Na-tions 1992:Article 2).

8 Diversity thus is a structural feature of Ecosystems ,and the variability among Ecosystems is an element of biodiversity. Theparties to the convention have endorsed the ecosystem approach as theirprimary framework for action. (See Box )For analysis and assessment, it is important to adopt a pragmatic view ofecosystem boundaries, depending on the questions being asked. In one sense,the entire biosphere of Earth is an ecosystem since the elements interact. Ata smaller scale, the guiding principle is that a well-defined ecosystem hasstrong interactions among its components and weak interactions across itsboundaries. (See also Chapter 5.) A practical approach to the spatial de-limitation of an ecosystem is to build up a series of overlays of significantfactors, mapping the location of discontinuities, such as in the distributionof organisms, the biophysical environment (soil types, drainage basins, depthin a water body), and spatial interactions (home ranges, migration patterns,fluxes of matter).

9 A useful ecosystem boundary is the place where a numberof these relative discontinuities coincide. At a larger scale, regional andeven globally distributed Ecosystems can be evaluated based on the com-monality of basic structural units. We use such a framework in the MA forthe global analysis of ecosystem properties and global assessment being undertaken by the MA is based on 10categories: marine, coastal, inland water, forest, dryland, island, moun-tain, polar, cultivated, and urban. (See Box ) These categories are notecosystems themselves, but each contains a number of Ecosystems . TheMA reporting categories are not mutually exclusive: Their boundaries , 6:19 AM5152 Ecosystems and Human Well-being: A Framework for AssessmentBOX The Ecosystem Approach: A Bridge Between the Environment andHuman Well-beingThe concept of an ecosystem provides a valuable framework for analyzing and act-ing on the linkages between people and Their environment.

10 For that reason, theecosystem approach has been endorsed by the Convention on Biological Diversity(CBD) and the Millennium Ecosystem Assessment (MA) conceptual framework isentirely consistent with this approach. The CBD defines the ecosystem approach asfollows:The Ecosystem Approach is a strategy for the integrated management ofland, water and living resources that promotes conservation and sustain-able use in an equitable way. Thus, the application of the ecosystemapproach will help to reach a balance of the three objectives of the Con-vention: conservation; sustainable use; and the fair and equitable sharingof the benefits arising out of the utilization of genetic resources. An eco-system approach is based on the application of appropriate scientific meth-odologies focused on levels of biological organization, which encompassthe essential structure, processes, functions and interactions among or-ganisms and Their environment.


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