Population viability analyses in conservation planning: An overview

Population viability analysis (PVA) is a collection of methods for evaluating the threats faced by populations of species, their risks of extinction or decline, and their chances for recovery, based on species-specific data and models. Compared to other alternatives for making conservation decisions, PVA provides a rigorous methodology that can use different types of data, a way to incorporate uncertainties and natural variabilities, and products or predictions that are relevant to conservation goals. The disadvantages of PVA include its single-species focus and requirements for data that may not be available for many species. PVAs are most useful when they address a specific question involving a focal (e.g., threatened, indicator, sensitive, or umbrella) species, when their level of detail is consistent with the available data, and when they focus on relative (i.e., comparative) rather than absolute results, and risks of decline rather than extinction. This overview provides guidelines for choosing a PVA model among three categories, from data-intensive individual-based population models to simple occupancy metapopulation models.