A reliability-theory approach to corridor design

Natural habitats are small islands in the sea of human environment. Area loss and fragmentation affect seriously the survival of species, for small, isolated populations are exposed to several risks. As the area of suitable habitats decreases, one way to escape local extinction is to migrate between habitats through ecological corridors, and utilize the whole metapopulation landscape. Thus, natural and designed corridors can be key elements for survival. Here, we present a method to study corridor pattern from a reliability-theory viewpoint. We analyze the probability of successful migration in a metapopulation landscape network of habitats, stepping stones and corridors. We examine the situation when individuals of a local population must migrate from a disturbed, critical habitat to others. In the landscape graph, points represent habitats and stepping stones, while edges represent corridors. If corridors can be destroyed, migration probability depends on the pattern of permeable corridors. Engineered corridors can enhance the reliability of migration, depending on their position in the network. We present some general rules for designing reliable landscape patterns (e.g. ‘necklace’ arrangement is less reliable for migration than ‘loop’). Then, we illustrate our viewpoint by presenting two hypothetical landscape networks and comparing the possibilities for designing reliable corridor topologies by creating one engineered corridor. Further, we determine the preferred topology for the engineered corridor. Our hope is that this reliability-theory analysis will stimulate further development of the method and in the fieldwork.