Species richness as criterion for global conservation area placement leads to large losses in coverage of biodiversity

Aim: To quantify and compare species coverage in priority areas for conservation identified using species richness as opposed to approaches that use individual species range maps. Location: Global. Methods: We compare the coverage of species when global priority areas for conservation are identified based on (1) twelve species richness maps of all and small-range amphibians, birds and mammals and all and small-range threatened (i.e., vulnerable, endangered and critically endangered) species; (2) weighted range size rarity, a richness measure corrected for range size; and (3) a complementarity-based analysis including species range maps for 21,075 terrestrial vertebrate species listed by the International Union for the Conservation of Nature. We also assessed whether any combination of small-range and/or threatened species richness could be a suitable surrogate for a complementarity-based analysis by assessing species coverage in priority areas located using (1) richness of small-range species only; (2) richness of all threatened species only; and (3) richness of small-range and threatened species. Results: Our results show clear differences in the spatial pattern of priority areas for conservation among the prioritizations based on species richness, weighted range size rarity and species range maps, with the species richness-based priority areas being highly aggregated in the tropics and the species range map priority areas being more evenly spread among the global terrestrial area. We also find that identifying priority areas for conservation using species richness produces a lower coverage of species than priority areas based on complementarity methods and identified using species range maps, where just one species was left without any protection. Main Conclusions: As methods and software currently exist for processing large numbers of individual species distribution maps in spatial prioritization, the use of species richness appears to be an unnecessary simplification of biodiversity pattern.