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and human needs. But concerns with biodiversity extend beyond those boundaries. Although a manager's actions are local and immediate, the management perspective must be broad enough to recognize a range of values and the implications of decisions for survival of larger ecosystems. A series of decisions that individually do not have major effects can have major cumulative effects.
This report differs from many recent ones that have focused solely on measures of the economic value of biodiversity in that it seeks to embrace the range of values that legitimately can be used to determine the merits of alternative courses of action regarding biodiversity. Recognizing that improved methods for assigning value can enhance the process of decision-making, we also provide a summary of state-of-the-art methods for establishing value. But we focus even greater attention on methods of weighing input from stakeholders who have different systems for determining the value of different actions so as to yield sound resource-management decisions.
The intent of this report is to provide perspectives on biodiversity that resource managers can consider in making decisions. The different approaches to valuing biodiversity are discussed throughout the report. Case studies are used to show that no single list of tools can be used for management decisions on biodiversity. We suggest that managers consider in their deliberations a broad range of information on biodiversity, including differing views and values of biodiversity. We believe that managers can benefit from such information. The committee reviewed the relevant scientific literature on biodiversity, its values, concerns about its status, and its treatment in analyses of its value.
Understanding the technical meaning of biodiversity and its implications is necessary if the values of conserving biodiversity are to be incorporated appropriately into resource-management decisions. The approach to providing such understanding used in this report is three-fold.
First, we develop the basis for understanding the importance of the components of biodiversity and some of the ways in which biodiversity is measured. Recognition that diverse biological systems are essential for life on the planet is, obviously, important in managing resources. But such management requires a fuller understanding of biodiversity and its components. In chapter 2, we attempt to define these components and to describe some of the ways to measure them. Biodiversity includes not only the world's species with their unique evolutionary histories, but also genetic variability within and among populations of species and the distribution of species across local habitats, ecosystems, landscapes, and whole continents or oceans. Because biodiversity is such a broad concept, methods for its quantification are necessarily broad. Nonetheless, the available data indicate that a greater species diversity in an ecosystem tends to increase the likelihood that particular ecosystem services will be maintained in the face of changing ecological or climatic conditions. The committee concludes that, given the variation in missions of agencies, managers must consider both the mainte-