Effective corridor width: linking the spatial ecology of wildlife with land use policy

Wildlife corridors are a policy tool to maintain or restore connectivity through human-modified landscapes. While corridors have been an important concept in wildlife conservation for decades, there is little evidence to guide their design. Specifically, width is one of the most contentious dimensions of corridors because it often limits industrial, residential, or recreational expansion. Building on concepts that describe how wildlife avoid infrastructure or people—zone of influence and the flight initiation distance—we present a conceptual approach to design and assess the management effectiveness of wildlife corridors through a concept we define as effective corridor width. The effective corridor width is the minimum spatial dimension needed to abate human influence on animal movement through the corridor. We searched for case studies documenting the zone of influence and the flight initiation distance from recreational trails and residential development for four species of carnivore: black bears, grizzly (brown) bears, gray wolves, and cougars. From these studies, we synthesized information on the effective corridor width, which varied from 3000 to 6000 m for residential areas and 400 to 1000 m for trails, depending on the species. We examined the effective corridor width in a case study from Alberta, Canada, where debate over the appropriate width of designated wildlife corridors has been ongoing for decades. Our analysis is a step towards developing robust, empirically derived guidelines for designing and managing wildlife corridors.