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Using weighted distance and least-cost corridor analysis to evaluate regional-scale large carnivore habitat connectivity in Washington


Population fragmentation and isolation are primary concerns for conservation of large carnivores. Highways are often important landscape features contributing to regional-scale habitat fragmentation for these species. We used GIS weighted distance and least-cost corridor techniques to map relative landscape permeability and landscape linkages for large carnivores in Washington and adjacent portions of Idaho and British Columbia. Landscape permeability was modeled based on land cover, road density, human population density, and topography. We identified six concentrations of large carnivore habitat, including the British Columbia Coast Range, the North Cascades, the South Cascades, the Kettle-Monashee Ranges, the Selkirk-Columbia Ranges, and the Olympic Mountains. The model highlighted four landscape linkage areas of potential importance for large carnivores including the Fraser River area (B.C.), Snoqualmie Pass (Wa), the Okanogan Valley (Wa. and B.C.), and the Upper Columbia River area (Wa. and B.C.). We also modeled landscape linkages in southwestern Washington, between the South Cascades and Olympics, however the resistance to movement in this landscape was extremely high. We expect that southwestern Washington is impermeable to long-distance movements for our focal species. GIS overlays of the Washington state highway network on our landscape permeability and linkage maps indicated that, in the vicinity of the Cascades and northeastern Washington, 497 miles (800 km) of state highway passed through areas accessible to large carnivore intra-territorial movement, and 234 miles (377 km) of state highway passed through landscape linkage areas that may be important for inter-territorial movement. [Funding for this project was provided by the Washington State Department of Transportation, and the USDA Forest Service, PNW Research Station under the Northwest Forest Plan.]

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