Graph theory and least-cost path: how their combination improves habitat network connectivity analysis and helps prioritize conservation measures

International audience; The green and blue infrastructure in France is based on the conservation and restoration of ecological continuity of habitats in relation to species’ biological requirements. Recent development in landscape ecology based on graph theory and species movement modelling using least-cost paths offer promising applications in terms of landscape management and biodiversity conservation. First, we present the model of potential connectivity based on graph theory and explain why it overcomes previous approaches. Then, we illustrate with an example of connectivity analysis in the region PACA for the Red Squirrel, a forest generalist species. The models identify the landscape areas that are connected or isolated from the rest of habitat network and prioritize the importance of patches and corridors for the maintaining of global network connectivity; they also analyse how connectivity varies according to species dispersal distance. They highlight the key habitat patches and corridors that must be protected to maintain habitat network connectivity for the species. These examples clearly show that these original methods can form valuable decision support tools for the implementation of green infrastructures at different spatial scales, and also help to locate further finerscale studies.