Spatial distribution of species populations,relative economic values,and the optimal size and number of reserves

We examine the tradeoff between the number and average size of nature reserves. When the costs of enforcing reserve boundaries are negligible, we find analytically that the relative price of biodiversity has a positive impact on the optimal total reserved area but an ambiguous impact on the optimal number of reserves. Simulation modeling of floral diversity in a tropical timber concession reveals that the resolution of this ambiguity depends on spatial distributions of the populations of tree species: whether or not they are spatially aggregated (clumped). The impact of biodiversity price on optimal reserve number remains analytically ambiguous when enforcement costs are not negligible. Multiple reserves being economically superior to a single reserve now requires, in addition to aggregation, a biodiversity price that is sufficiently high to offset the effects of enforcement costs. Most of our simulation scenarios generate threshold biodiversity prices that do not exceed a leading estimate of the marginal value of a higher plant species in the bioprospecting literature. Several smaller reserves evidently can be economically superior to a single larger one even in the presence of enforcement costs.