The greatest threats to species

Abstract The growing human population is responsible for a massive decline in species, biodiversity, and ecosystems across the globe. If we are to significantly slow these losses, the attention and resources devoted to individual causes should be commensurate with the magnitude of their contribution to the problem. The purpose of this study was to determine the relative magnitude of five major threats to species identified by the International Union for Conservation of Nature (IUCN) as threatened with extinction. Specifically, we analyzed the entire IUCN Red List database to determine the percentage of threatened species affected by overexploitation, climate change, pollution, habitat destruction, and invasive species, diseases, and genes. We also randomly sampled a portion of the database to estimate the percentage of species for which each threat was the dominant threat placing them at risk of extinction. Of the 20,784 species for which data were available, 88.3% were impacted by habitat destruction, 26.6% by overexploitation, 25% by invasives, 18.2% by pollution, and 16.8% by climate change and weather. Focusing on dominant threats, the percentage of species for which a given threat was the main factor pushing them toward extinction was as follows: habitat destruction 71.3%, overexploitation 7.4%, invasives 6.8%, pollution 4.7%, climate change, and weather 1.8%. Regardless of how percentages are calculated, habitat destruction threatens more species than all other categories combined, climate change the fewest. From the perspective of species and biodiversity conservation, these data suggest that a significant change in global environmental priorities is needed. Habitat destruction should become a greater focus of global environmental efforts and receive the attention and resources appropriate to the extraordinary magnitude of its impact. Moreover, while it is important to address all environmental problems, given the disproportionate impact habitat destruction has on species, care should be taken to avoid solutions to other problems that exacerbate this destruction.