Direct and indirect impacts of climate change and land use change over biodiversity: a case of study with the brown bear in Europe

When we explore global changes effects over biodiversity it is usually explored the direct effects, while ignoring the indirect effects (biotic), driving to erroneous predictions of how global change impacts biodiversity. Here, we focus on the brown bear (Ursus arctos) to understand how direct and indirect impacts of climate and land use change would affect the future distribution and vulnerability of different populations across Europe. We first conducted a literature search, compiling information on ~100 species consumed by brown bears. We downloaded occurrence data for all species consumed by the brown bear from GBIF. We built species distribution models for all these species, using biomod2 in R, in function of current climate and land use data. We interpolated the spatial variation of energy of each species in the diet, and it was combined with the distribution model resulting in the potential energy for each species. Using different scenarios for climate and land use change, we projected the future distributions of the brown bear diet species. Finally, we calculated the potential current and future suitable habitats of brown bear in function of the potential energy of diet, climate and land use. The range dynamic of the brown bear was best explained by considering both direct and indirect impacts. Accounting for energy (indirect effect) buffered the direct impact of climate and land use change. Our results highlight the importance of taking a food-web ecosystem approach to evaluate the impact of global changes and predict modifications in the distribution and vulnerability of species.