VI.1 Ecosystem Services: Issues of Scale and Trade-Offs
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VI.1 Ecosystem Services: Issues of Scale and Trade-Offs R. J. Scholes OUTLINE 1. Local, regional, and global services 2. Matching the scales of process, analysis, and management 3. Cross-scale interactions 4. Trade-offs among ecosystem services The quantity of each individual service that a particular ecosystem delivers varies over time and place, to some degree independently of other services. It is therefore essential to specify the period and the included area when quantifying or valuing a service. It is important to match, as far as possible, the time and space scales at which the ecosystem and its services are assessed and managed to the scales at which the underlying ecological processes that deliver the services operate. It follows that ecosystem service assessments must also pay thoughtful attention to the period that the assessment covers and the location of the boundaries of the assessed area. Because each service differs somewhat in the time and space distribution of its important ecological and social processes, some compromises are necessary in practice. Very frequently the factors that control ecosystem services (the drivers) operate at scales that may only partially overlap those at which the service is used. It is also commonly found that the governance systems that determine who may use what services and in what amount operate at one or more political or economic scales, often disconnected from either the scales of the ecosystem process or management activities. These cross-scale interactions have the consequence that there is seldom a single, perfect scale for studying or managing ecosystem services: multiscale assessments and management institutions are needed. Use of one ecosystem service typically has consequences for the quantity of other services that can be used. This is known as a trade-off or, if the interaction leads to a net increase in one or more services, a synergy. Determining the appropriate mix of services to be used from a given ecosystem is a complex process for which there is no simple or perfect solution; furthermore, the appropriate mix and accompanying solutions themselves change over time. Reaching an equitable and sustainable set of trade-offs is especially difficult if the people who benefit from the services are different from the people on whose actions the continued supply of the service depends. This situation commonly arises as a result of spatial separation (e.g., between highland farmers and lowland water users), temporal separation (use of a service now versus leaving it for later generations), or differences in the jurisdiction or power of various social groups or institutions . GLOSSARY domain. The range of characteristic scales in time and space at which a particular process (such as the delivery of an ecosystem service) operates resolution. The spatial or temporal interval between observations scale. The physical dimensions, in either time or space, of a phenomenon or observation synergy. A special case of trade-off (also known as a ‘‘positive trade-off’’) where the use of one service enhances the production of another trade-off. The relationship between the quantity of one ecosystem service that is used and the quantity of one or more other ecosystem services that can be used 1. LOCAL, REGIONAL, AND GLOBAL SERVICES Some ecosystem services are available only in a particular area or at a particular time. An example is the fruit of a wild tree species—it has a season and location of availability. Other services are effectively delivered all over the world, continuously. An example is the regulation of the global climate: because ocean currents and wind systems transport matter and energy between the equator and the poles within a few years, effects on the climate system at one location (e.g., uptake of carbon dioxide by a forest) have climate benefits throughout the world. Ecosystem services can be delivered over the full range of scales between these two extreme examples. The general observation is that ecosystem services are patchy (i.e., inhomogeneous) in both space and time. Throughout this chapter, the broad issues that apply to space often also apply to time. For the sake of brevity, usually only the space dimension is explicitly mentioned, but the time dimension is implied as well. The notions of scale and resolution must not be confused. Scale is the total dimension (distance or area or years) over which a phenomenon occurs or is studied; resolution is the dimension at which individual observations are made, and specifically the interval between adjacent observations: it is the smallest detail that can...