Chapter Synthesis

Conservation biology has rightly sought to distance itself from the single-species management approaches that characterized applied resource management sciences in the past, an approach that led to entire communities and ecosystems being managed for the benefit of one or a few species. However, conservation biology must not confuse single-species management with species-specific conservation, an approach that should be valued and practiced if conservation biologists have any hopes of seeing the recovery of threatened and endangered populations. Populations are the primary currency and concern of conservation biology, but the need persists to define populations more rigorously in order to avoid misunderstanding and mismanagement. This is particularly critical at a time when more and more populations are threatened with extinction, and when many species have been reduced to only a small number of disjunct populations with relatively few individuals.

Conservation biologists have increasingly focused on the question, "What is the minimum number of individuals that are needed for a population to persist through time?" Not surprisingly, the precise estimator of the answer (the minimum viable population) and the analytical tool that estimates it (population viability analysis) have become essential to the practice of conservation biology. However, conservation biologists must mature in their recognition of PVA as an analytical technique rather than a diagnostic tool, and thus better appreciate its limitations. The estimate of an MVP should not be made solely through PVA, but should include a detailed assessment of the ecology of the species at risk, and conservation biologists should incorporate risk analysis and adaptive management procedures into assessments of PVA before determining final management strategies to restore small populations to viable numbers.

Confusion about what constitutes a metapopulation leads to misunderstandings and misjudgments about the nature of spatially disjunct population units. Empirical evidence suggests that classical metapopulations may be relatively rare in nature, and conservation biologists must be careful not to call all patchy populations, dispersed populations, or fragmented, nonequilbrium populations "metapopulations." Doing so could lead to management solutions that are inappropriate to actual population problems.

The dreadful urgency of attempting to save many small and declining populations from imminent extinction compels conservation biologists to implement management strategies quickly. However, this combination of concern and rapid response must not tempt conservation biologists to be careless in their systematic analysis of the causes of a population's decline. Each assessment of cause must be framed as a carefully constructed hypothesis that leads to specific predictions, a clear and practical management strategy, and a measurable way to test consequences that determine its veracity.

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