Biological diversity: where is it?

To preserve biological diversity, wealthy nations usually save the large and cuddly species that excite the public’s imagination1. This is not necessarily a bad strategy. The relatively large size of these species means that their population densities are low. Consequently, the minimal numbers required for persistence inhabit large areas and many other less charismatic species are protected under their umbrella. Furthermore, large species are often top predators and thus play crucial, so-called keystone roles in the community’s dynamics. Yet such a species-biased approach is not necessarily appropriate for the great majority of animal species that are not furred and feathered, or for plants, or, indeed, for all organisms in species-rich tropical nations deciding on how to allocate land for national parks. The obvious strategy protects areas of greatest diversity. Two recent papers on mammals by Mares in this issue and Pagel et al.2 illustrate the complex biological issues involved in predicting what diversity might remain after future planners have taken a cookie cutter to their wilderness.