Conserving Nature’s Stage: Mapping Omnidirectional Connectivity for Resilient Terrestrial Landscapes in the Pacific Northwest

This report completes a larger project to identify and map sites that contribute to climate change resilience in the Pacific Northwest, all funded by the Doris Duke Charitable Foundation. Previous work (reported in Buttrick et al. 2015) focused on mapping sites likely to be resilient to climate change based on local permeability and topoclimate diversity. Those sites that were more locally intact and topoclimatically diverse were considered more resilient to climate change because they would have higher potential to allow organisms to access climatically suitable areas by moving short distances. The previous analyses purposefully considered the local scale, not looking beyond a 3-km window when measuring terrestrial resilience characteristics. Results were stratified by ecoregion and by geophysical setting (“land facets”) to identify portions of land facets more likely to be resilient to climate change. The broad-scale landscape connectivity analysis reported here complements these previous analyses by identifying areas likely to facilitate ecological flow—particularly movement, dispersal, gene flow, and distributional range shifts for terrestrial plants and animals—over large distances and long time periods. Similar to the local permeability analyses (Buttrick et al. 2015), this analysis is not species-specific. Rather, it focuses on structural connectivity of natural lands, with resistance to movement modeled as a function of landscape naturalness. This analysis shifts the focus to identifying areas important for longer-distance movements – up to 50 km – complementing the local permeability analyses which identified areas well-connected within a 3-km radius. This effort does not incorporate projections of future climates, nor does it address connectivity for aquatic species. The results identify broad, intact areas where movement of terrestrial organisms is largely unrestricted by human modifications to the landscape, as well as constricted areas where fragmentation has reduced movement options and further habitat loss could isolate remaining natural lands. We provide guidance on how these results can be combined with the resilient sites analyses of Buttrick et al. (2015), as well as other conservation priorities. Our project area covers 97.3 million hectares (240.4 million acres) of the Pacific Northwest and northern California. This includes 92 million hectares (227 million acres) analyzed in Buttrick et al. (2015) — namely, the California North Coast, Klamath Mountains, Sierra Nevada, West Cascades, East Cascades/Modoc Plateau, Columbia Plateau, and Middle Rockies/Blue Mountains ecoregions as well as the U.S. portion of the Pacific Northwest Coast, Willamette Valley/Puget Trough, North Cascades and Canadian Rockies ecoregions. This connectivity study also encompasses an additional 5.3 million hectares (13.4 million acres) comprising the U.S extent of the Okanagan ecoregion and the extent within Idaho of the Utah-Wyoming Rocky Mountains ecoregion (Map 1).