Incorporating asymmetric connectivity into spatial decision making for conservation

Real patterns of ecological connectivity are seldom explicitly or systematically accounted for systematic conservation planning, in part because commonly used decision support systems can only capture simplistic notions of connectivity. Conventionally, the surrogates used to represent connectivity in conservation plans have assumed the connection between two sites to be symmetric in strength. In reality, ecological linkages between sites are rarely symmetric and often strongly asymmetric. Here, we develop a novel formulation that enabled us to incorporate asymmetric connectivity into the conservation decision support system Marxan. We illustrate this approach using hypothetical examples of a river catchment and a group of reefs, and then apply it to case studies in the Snowy River catchment and Great Barrier Reef, Australia. We show that incorporating asymmetric ecological connectivity in systematic reserve design leads to solutions that more effectively capture connectivity patterns, relative to either ignoring connectivity or assuming symmetric connectivity.