Climate Change Implications for Grizzly Bears (Ursus arctos) in the North Cascades Ecosystem


Ransom, J. I., M. Krosby, and A. L. Lyons. 2018. Climate change implications for grizzly bears (Ursus arctos) in the North Cascades Ecosystem. Natural Resource Report NPS/NOCA/NRR—2018/1814. National Park Service, Fort Collins, Colorado.


The North Cascades Ecosystem of north-central Washington State and southern British Columbia, Canada, is one of six designated recovery zones for grizzly bears (Ursus arctos) in the conterminous United States. The National Park Service and US Fish and Wildlife Service evaluated a range of alternatives for restoring grizzly bears in the Cascades, and carrying capacity models estimated the
ecosystem could support approximately 250–300 bears under current habitat conditions. However, as climate change shapes the North Cascade Ecosystem, there is considerable uncertainty as to how grizzly bear habitat may change through time.

This report aims to synthesize the scientific literature and develop the conceptual basis for understanding potential climate impacts on grizzly bear habitat quality in the North Cascades Ecosystem. We find that the complex relationship between changes in climate, natural processes, and natural and anthropogenic features will expose grizzly bears to a range of changing resource conditions, but the species’ low sensitivity to changing climate and high adaptive capacity may lead to positive long-term outcomes if a successful founding population can be re-established. It is expected that the outcome of this effort will be used to inform modeling efforts for estimating grizzly bear carrying capacity under future climate change scenarios.