Expected minimum population size as a measure of threat

Abstract

Risks of population decline are studied extensively in conservation biology, but are difficult to estimate because they change abruptly over a relatively narrow range of parameters. We propose that risks of decline may be usefully summarized by the expected minimum population size. This is the smallest population size that is expected to occur within a particular time period. Analytical solutions for the expected minimum population size are obtained for a stochastic population model of exponential growth. In more complex models that are analyzed by Monte Carlo simulation, the expected minimum population size may be determined by recording the smallest population size obtained in each iterati..