Assessing habitat connectivity for land-use planning: a method integrating landscape graphs and Delphi survey

Increasing fragmentation is occurring in most valley floors in Alpine regions, where urbanization and infrastructure development are reducing connectivity among remnant natural areas. This undermines the conservation of alpine biodiversity. Using a landscape graph-based approach, we visualized and assessed the dispersal opportunities for three target species (Rana synk. esculenta, Erinaceus europaeus, Moscardinus avellanarius) on a municipal scale. We considered the barrier effect caused by landscape objects, such as linear infrastructures and artificial land covers. Species-specific barrier effects were estimated through a Delphi survey involving 25 experts. The information collected was then used to draw a landscape graph of local connections and to estimate the functioning of the networks of habitat patches in terms of their capability of sustaining local populations of target species. The methodology was applied in an alpine valley floor in Trentino, northern Italy, and resulted in the mapping of all possible and remnant linkages between habitat patches in its current state. The approach may provide a better qualitative understanding of the impacts of proposed land-use changes, and was found to be particularly helpful in contexts where availability of data is limited.