Have human impacts exceeded climate in shaping mammalian distributions?

Xin Chen, Luis José Aguirre, Xiao Feng

Human impacts are increasingly recognized as drivers of biogeographic patterns, yet it remains unclear whether they surpass climate in shaping species distributions. Here we aim to investigate the relative importance of anthropogenic vs. climatic factors in determining mammalian distributions. We modeled the relationship between the geographic distributions of 331 mammal species and 12 representative anthropogenic and climatic factors, and quantified variable importance with ecological niche models and explainable artificial intelligence in both environmental and geographic space. We also constructed the response curve of human impact index (HII) for each species, and investigated the association between the response curves and species' biological traits. We found that anthropogenic factors were ranked as top contributors for nearly half of the species examined, and the effect of human impact index has exceeded that of average and seasonal climatic conditions across spatial scales. While limiting effects of anthropogenic factors were consistent across the landscape, the climatic factors often show spatial clusters at different sub-sections of species’ ranges. Species’ response to human impacts displayed diverse patterns, and the positive responses were associated with traits of reduced conflicts with humans, faster reproduction, and greater mobility. The extent of human impacts has exceeded that of climate in shaping mammalian biogeography patterns. The heterogeneous responses of mammal species to human impacts highlight the need to broadly consider anthropogenic factors, in addition to climate, in studying biodiversity in the Anthropocene.