which in turn, directs further analysis as the basis for additional deliberation. Thus, science, in the form of analysis, is brought into full play in the deliberation process, which also informs the science.

The Problems Facing Managers

Scientific Uncertainty

Managing ecosystems to preserve or enhance biodiversity is a complex task. Complexity is added when a manager must consider competing goals, such as recreation or resource extraction. The basic science, while providing essential guidance to ecosystem managers, usually provides results that include some uncertainty. And, the research needed to provide contextual data that allow the application of general scientific principles to local situations is generally weak. As a result, managers must proceed with a limited and uncertain scientific basis for their decisions. In practical terms, although the accessible science can give managers some understanding of the likely consequences of alternative policies and management regimes, they will also be aware that the consequences are not known with certainty. Indeed, managers are often faced with "meta-uncertainty" (Dietz and others 1993) in that they do not know how much uncertainty exists—they are uncertain about the extent of the uncertainty.

Uncertainty about the biological and physical consequences of management alternatives affects benefit-cost analysis (BCA) and other policy-analysis tools. The results of those analyses are at least as uncertain as the ecological analyses on which they are based. Because BCA and related tools are still developing and because the amount of context-specific information is sparse for most decisions, uncertainty is added. As noted in chapter 5, there is still some controversy about the use of methods intended to estimate the nonmarket value of biodiversity, which increases uncertainty still further. In the face of scientific uncertainty, BCA and related valuation tools can sometimes eliminate some options as unrealistic or inferior. But rarely will there be enough information to pick a course of action that is unambiguously superior to all other options.

The limited amount of information needed for such analyses constitutes one measure of the need for research. For example, improvements in the techniques of contingent valuation (CV) in recent years have occurred as a result of research. Additional research on CV techniques, as well as on BCA, are likely to improve future estimates of the values of natural systems.

Value Complexity and Uncertainty

Even if the science involved no uncertainty, there would be value-based sources of conflict. Different members of the public assign different values to biodiversity, to the benefits to be gained when biodiversity is preserved or lost,

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