Reconsidering environmental diversity (ED) as a biodiversity surrogacy strategy

Environmental Diversity (ED) has been proposed as a potential biodiversity surrogate for use in spatial biodiversity planning. The concept is based on the premise that differences in species composition between areas are correlated with differences in environmental conditions. If this is true then sites selected to represent the full range of environmental conditions in an area should provide good coverage of species diversity. This is potentially significant for conservation planning because environmental data are more easily available while species distribution data are often incomplete, but empirical tests of ED have been inconclusive. We explored the value of ED as a biodiversity surrogate using species distribution data from South Africa, focusing on how implementation affects its performance. We used empirical distribution datasets for birds, butterflies, frogs, and reptiles as well as artificial species distributions and modeled distributions for butterflies. Our results show that the form of the underlying optimization model and the number of environmental variables have a significant effect on the performance of ED while the choice of heuristic procedures for selecting sites has no significant effect. We conclude that ED can perform well as a biodiversity surrogacy strategy if it is implemented correctly.