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WWRC 93-19
Population Viability Analysis: Adaptive Management for Threatened and Endangered Species


Population viability analysis (PVA) is the process of estimating the probability of persistence of a population for some arbitrary time into the future (Soule 1987, Boyce 1992). PVA has its origins in the conservation biology movement; indeed, it is one of the keystone ideas of conservation biology (Wagner 1989). Performing a PVA entails compiling available biological data on a species and using these data as the basis for a simulation model for the population. The model then can be used to project future population trajectories from which one may estimate the probability that it will persist, for say 100 years, or other related estimates such as the probability of extinction or expected time extinction (Dennis etal. 1991).

The probability of extinction emerging from PVA would appear fundamental to establishing priorities for conservation based on guidelines that have been proposed for the categorization of species by International Union for Conservation of Nature and Natural Resources (IUCN) (Mace and Lande 1991). In other applications, attempts are made to determine the minimum viable population (MVP) necessary to meet conservation objectives. Unfortunately, such applications are premature because we cannot reliably estimate the extinction probability for any species (Lebreton and Clobert 1991, Boyce 1992).

Yet, I believe that PVA can be enormously valuable if viewed in the context of adaptive management. The process of pulling together all available data and building a simulation model constitutes a synthesis of our current understanding of the population. Simulation models can be used to generate hypotheses of how we expect the system to respond to perturbations or management manipulations (Boyce 1991b). If this is followed by monitoring the consequence of management actions, PVA clearly is within the framework of adaptive management (Walters 1986).

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