Conservation priorities for peripheral species: the example of British Columbia

Most jurisdictions must assign conservation priorities to peripheral species. British Columbia hosts more than 1300 peripheral taxa, about 900 of which appear on the Red and Blue Lists prepared by the province to guide conservation actions. Conversely, fewer than half of the endemic taxa, or taxa for which the province has major global stewardship responsibility, appear on provincial Red and Blue Lists. We examine why we conserve and list species, concluding that the primary scientific or practical reason is to sustain genetic variability. We consider two broad kinds of peripheral species: disjunct (geographically marginal) populations and continuous peripheral populations that straggle irregularly across provincial boundaries. Populations of both groups may be ecologically marginal, with (lambda) < 1. We document the degree to which each group enters provincial Red and Blue Lists. Factors used to modify rankings of risk are correlated in a fashion that artificially biases continuous peripheral populations toward rankings of higher risk. Federal initiatives in recovery plans for most continuous peripheral species appear doomed to failure for sound biological reasons. We note alternative approaches to ranking species for conservation action and recommend that conservation efforts for peripheral species be focused on disjunct peripheral populations, rather than continuous peripheral populations.