The Mediterranean Dune–Beach–Banquette Ecosystem, Its Pivotal Role in Land–Sea Coupling and the Functioning of Coastal Systems, and Some Related Management Issues

In the Mediterranean, the dune–beach ecosystem is characterized by the presence of thick deposits of dead leaves of the endemic seagrass Posidonia oceanica, called banquettes (Dune–Beach–Banquette ecosystem—DBB). This ecosystem plays an important role in the coupling between sea and land. The banquettes provide important ecosystem services: protection of beaches against erosion, contribution to the building of the dune, and a source of nitrogen for coastal vegetation. They are home to a rich and diverse invertebrate fauna that are consumed by other predatory invertebrates and seabirds. A conceptual model of the functioning of the DBB ecosystem and its relation with adjacent ecosystems has been outlined. When dead P. oceanica leaves return to the sea, which is the fate of most of the banquette, they constitute an important source of carbon and nutrients for coastal ecosystems and fisheries. Beach management, with the removal of banquettes and driftwood to meet the supposed requirements of beach users and tourists, is an ecological disaster, in addition to being an economic burden for coastal municipalities. Beach management methods that respect the interactions between the marine and terrestrial realms, which preserve the beaches from erosion and allow the return of the banquettes to the sea, and which take into account the real perceptions of beach users are feasible in the framework of the concept of the ‘ecological beach’.