A Common Framework for Conservation Planning: Linking Individual and Metapopulation Models

Many populations exhibit pronounced spatial structure: dispersed areas of high population density embedded in areas of low density, with population centers connected through dispersal. This recognition has led many conservation biologists to embrace the metapopulation concept (Levins 1970) as the appropriate paradigm for reserve design structures (reviewed in Hanski 1991 and Harrison 1994). This concept seems appropriate for those species that have patchy distributions because the critical resources on which they depend are distributed in this fashion. This paradigm may be less applicable, however, to species that historically have had a more or less uniform distribution of individuals across the landscape. If such species are faced with threats to their persistence, is a metapopulation reserve structure appropriate for their conservation? Or is the tailoring of reserve design to a single paradigm similar to attempting to force a square peg into a round hole? As a species, spotted owls are widely distributed, show extensive geographic variation in their habitat relationships, and, at a landscape scale, have a territory distribution that is spatially variable. Because of threats to their long-term persistence, conservation strategies for all three subspecies of spotted owl have recently been proposed (Thomas et al. 1990; Verner et al. 1992; USDI 1991). Despite striking similarities in the ecologies of these three subspecies and similar threats to their population viability, their conservation strategies appear quite distinct, suggesting that contrasting sets of ecological principles may have been applied in the planning process. Despite appearances, a common hypothesis-testing framework justified the process of conservation planning and a common set of population dynamics principles underlies each conservation strategy (Noon and Murphy 1994).