Human Impacts, Climate, and Trait-Mediated Responses in Contemporary Mammal Distributions

Abstract

Aim

Human impacts are increasingly recognized as drivers of biogeographic patterns, yet it remains unclear whether they match or potentially surpass climate in shaping species distributions. Here we aim to investigate the relative importance of anthropogenic versus climatic factors in determining mammalian distributions.

Location

North America.

Taxon

Mammal.

Methods

We modelled the relationship between the contemporary (1990–2020) distributions of 219 mammal species and 12 representative anthropogenic and climatic factors, and quantified variable importance with ecological niche models and explainable artificial intelligence (i.e., SHapley Additive exPlanations or SHAP) at range-wide and local scales. 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.

Results

We found that anthropogenic factors were ranked as top contributors for more than half of the species examined, and HII showed permutation importance comparable to, and in many cases greater than, individual or principal components of bioclimatic variables. The SHAP maps showed that the dominating effects of HII were widespread across the continent, and the effects of other factors often showed spatial clusters at different subsections 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.

Main Conclusions

These results suggest that contemporary mammal distributions are co-determined by anthropogenic and climatic factors, with anthropogenic effects varying across space and among species. The extent of human impacts is comparable to and, in some cases, exceeds that of climate in shaping contemporary mammalian biogeography patterns. This highlights the need to broadly consider anthropogenic factors alongside climate when studying biogeography and biodiversity patterns in the Anthropocene.