A systematic review of climate change effects on black and brown bears

Katherine A. Kurthᵃ, Katherine C. Malpeliᵇ, Joseph D. Clarkᶜ, Heather E. Johnsonᵈ, Frank T. van Manenᵉ

ᵃU.S. Geological Survey, National Climate Adaptation Science Center, Oak Ridge Institute for Science and Education
ᵇU.S. Geological Survey, National Climate Adaptation Science Center
ᶜU.S. Geological Survey, Northern Rocky Mountain Science Center, Southern Appalachian Research Branch
ᵈU.S. Geological Survey, Alaska Science Center
ᵉU.S. Geological Survey, Northern Rocky Mountain Science Center, Interagency Grizzly Bear Study Team

Climate change poses a pervasive threat to humans and wildlife through altering resource availability, increasing co-occurrence, and directly or indirectly influencing human-wildlife conflict. For many wildlife agencies in North America, managing bears (Ursus spp.) and human-bear conflict is a priority, yet the direct and indirect effects of climate change are exacerbating
management challenges. Understanding the underlying ecological drivers of bear responses to climate variability and change, and the implications for conflict, will be critical for maintaining human-bear coexistence in North America. We synthesized 120 articles that identified direct and indirect mechanisms by which climate variability and change affect brown bears (Ursus arctos) and American black bears (Ursus americanus) in North America. The literature focused on examining climate impacts on bear diet, body size, habitat selection, space use, activity, denning chronology, and population demographics and dynamics. Across these categories, we
summarized the documented and projected bear responses and resulting implications for human-bear conflict. Climate-driven changes in natural food availability were frequently implicated in influencing bear behavior and demography, and creating conditions under which conflicts with humans are likely to increase. Bears in North America may face increased challenges as habitat and natural food availability continue to be altered by climate change. Our review provides a foundation upon which to identify climate drivers of bear ecology, conditions conducive to human-bear conflict, and adaptive management strategies. Given substantial evidence of climate impacts to bears, incorporating climate considerations into bear management can help managers strategically allocate resources and promote human-bear coexistence.