Comparing multiple species distribution proxies and different quantifications of the human footprint map, implications for conservation

Anthropogenic threats drive species to extinction and are the focus of extinction risk analyses and conservation planning. Threats are often quantified through higher level proxies, such as the human footprint (HF). We tested the effects that multiple methods of representing species' distribution and different quantifications of a HF map have on threat measurement, and how these influence conservation decisions. We quantified the magnitude of HF for 901 Southeast Asian mammals according to several methods. We ranked the species according to the measured HF value, and produced priority lists of top-impacted species. The different representations of species' distribution caused significant disagreement in HF calculations. HF values were on average lower when calculated in species' suitable habitat or occurrence points in comparison to the whole geographic range. Biases were non-linear and dependent on distal factors, such as the proportion of suitable habitat within species' range and species' habitat specialism. Using different HF quantifications also yielded disagreement, with 2-56% difference observed in species membership among priority lists. Threatened species were best predicted, and significantly placed in the top-ranking, when measuring their proportion of range exposed to high levels of HF. We thus show that the HF extent, not only its average value, determines species extinction risk. A well-framed global conservation strategy must address the quantification of human impact on biodiversity. The selection of quantification methods has implications for how such impact is evaluated. Improving techniques to quantify biodiversity threats will enhance the effectiveness of extinction risk analyses and conservation decisions