Extensive green roofs in Mediterranean regions: can they be designed for biodiversity?

From pilot projects in Switzerland, biodiverse green roofs are now mainstream worldwide. However, how to best adapt the biodiversity design approach from Temperate to Mediterranean climate, is still merely theoretical. The reasons are multiple. First, the major green roofs norms, standards and guidelines neglect biogeographic regions and plant-soil (substrate) relationships. Second, even if the habitat template approach developed by ecologists and applied in the Mediterranean contest proved to be effective, it encountered the reluctance of designers and landscape architects. Third, the species selection and assemblage is still driven by aesthetic reasons.