Focal species and landscape naturalness corridor models offer complementary approaches for connectivity conservation planning

The dual threats of habitat fragmentation and climate change have led to a proliferation of approaches for connectivity conservation planning. Corridor analyses have traditionally taken a focal species approach, but the landscape naturalness approach of modeling connectivity among areas of low human modification has gained popularity as a less analytically intensive alternative. We compared focal species and naturalness-based corridor networks to ask whether they identify similar areas, whether a naturalness-based approach is in fact more analytically efficient, and whether agreement between the two approaches varies with focal species vagility. We compared focal-species and naturalness-based connectivity models at two nested spatial extents: greater Washington State, USA, and, within it, the Columbia Plateau ecoregion. We assessed complementarity between the two approaches by examining the spatial overlap of predicted corridors, and regressing organism traits against the amount of modeled corridor overlap. A single naturalness-based corridor network represented connectivity for a large (> 10) number of focal species as effectively as a group of between 3 and 4 randomly selected focal species. The naturalness-based approach showed only moderate spatial agreement with composite corridor networks for large numbers of focal species, and better agreed with corridor networks of large-bodied, far-dispersing species in the larger scale analysis. Naturalness-based corridor models may offer an efficient proxy for focal species models, but a multi-focal species approach may better represent the movement needs of diverse taxa. Consideration of trade-offs between the two approaches may enhance the effectiveness of their application to connectivity conservation planning.