Résumé
Urbanization is a major threat on biodiversity due to the direct destruction of natural and semi-natural habitats and to the indirect impacts caused by urban areas beyond their limits. In this study, we proposed a methodological framework to assess the potential impacts of current and future urbanization on high diversity sites and their associated species across the entire French Mediterranean region. Using a 100 m grid cell, we adapted a land-use change (LUC) model to project future urbanization over a 20 years period. We developed a multi-level approach based on three impacts of urban development: the direct consumption of high diversity sites, the indirect urban effects on the surrounding area over a scale of 2 km and a scale of 50 km. Our model predicts that 35% of the total number of sites can potentially be impacted by urbanization (i.e. at least 1 ha predicted to be built between 2006 and 2030). 3.2% of the total number of sites may lose 10% or more of their surface area to urbanization. We found that the impacts of urban area and urban growth differ among the three different pressure indicators in terms of surface area and localization of sites, number and nature of species impacted and variation of these patterns between the two dates. In general, most of the sites under pressure are located in the coastal part of the study region and are of smaller surface area than average.