Humans and climate change drove the Holocene decline of the brown bear

The current debate about megafaunal extinctions during the Quaternary focuses on the extent to which they were driven by humans, climate change, or both. These two factors may have interacted in a complex and unexpected manner, leaving the exact pathways to prehistoric extinctions unresolved. Here we quantify, with unprecedented detail, the contribution of humans and climate change to the Holocene decline of the largest living terrestrial carnivore, the brown bear (Ursus arctos), on a continental scale. We inform a spatially explicit metapopulation model for the species by combining life-history data and an extensive archaeofaunal record from excavations across Europe with reconstructed climate and land-use data reaching back 12,000 years. The model reveals that, despite the broad climatic niche of the brown bear, increasing winter temperatures contributed substantially to its Holocene decline - both directly by reducing the species' reproductive rate and indirectly by facilitating human land use. The first local extinctions occurred during the Mid-Holocene warming period, but the rise of the Roman Empire 2,000 years ago marked the onset of large-scale extinctions, followed by increasingly rapid range loss and fragmentation. These findings strongly support the hypothesis that complex interactions between climate and humans may have accelerated megafaunal extinctions.