Model assessments of the optimal design of nature reserves for maximizing species longevity

Using a computational model for the population growth and dispersal of a mo del species in a fluctuating environment, we test three nature reserve geom etries tone large, many small, and a self-similar distribution of reserve s izes) to determine which geometry maximizes species longevity. The self-sim ilar distribution is a close approximation to the distribution of managed a reas in the conterminous United States. We consider models with and without migration from or between reserve fragments and both short- and long-range dispersal mechanisms. The optimal geometry depends on the type of dispersa l and on the relative probability of survival in protected and non-protecte d areas. When no migration is allowed from or between reserve fragments of the three geometries, many small equally sized reserves are the optimal geo metry. When migration is allowed, the optimal geometry is a single large re serve when the survivability in non-protected areas is low and a self-simil ar distribution when the survivability is high. (C) 2000 Academic Press.