Threatened primates experience high human densities: adding an index of threat to the IUCN Red List criteria Original Research Article

IUCN Red List conservation status is apparently judged mainly by assessment of speciesʹ susceptibility to threat. However, risk must often depend also on the threat itself. Therefore, we investigate the value of adding to IUCNʹs current criteria a separate index of threat, human density. Human density in the geographic range of Threatened primate species is significantly higher than in the range of Lower Risk species. Thus, Threatened species are both susceptible, and experience more threat. However, the match is far from perfect. Given abundant other evidence of adverse effects of high human density, the mismatch emphasizes the potential benefit of adding an index of threat to the current criteria. A main advantage might be improved assessment, given the amount of up-to-date data on threats compared with the paucity on reactions to threat. The simplest means of incorporation might be to increase the status of species that experience higher than a certain threshold human density.