The high patrimonial value of the Mediterranean beaches, with a special attention to the Posidonia oceanica ‘banquettes’: a review
banquettes of drift seagrass leaves, beaches, crustaceans, dunes, ecosystem services, heritage value, insects, Mediterranean Sea, Posidonia oceanica.
Sandy beaches, together with the foredune and the dune, form a morphological, functional and ecological complex, the beach-dune complex. This complex provides ecosystem services which have by far the highest value in the coastal areas, both marine and terrestrial habitats considered; it requires an overall management approach. Sandy beaches are often wrongly perceived by the public at large and by stakeholders as ‘ecological deserts’, the value of which is mainly economic. In fact, beaches harbour an extraordinary range of biological diversity, with dozens of species, plant and animal, which are specific to them. This biological diversity is sometimes not very visible, due to the small size of the individuals, the fact that they live hidden in the sand and their rarity on beaches artificialized by inappropriate management. Mediterranean beaches are unique worldwide by virtue of the permanent, or not, presence of accumulations of dead leaves of the endemic seagrass Posidonia oceanica. These accumulations, up to 2.5 m in thickness, are called banquettes. They play a prominent role in protecting beaches from erosion. In addition, they contribute to the construction of the dune. Eventually, sooner or later, dead leaves from the banquette will return to the sea, where they constitute a major source of organic matter and nutrients, for the benefit of coastal ecosystems and artisanal fisheries. The Mediterranean coastal regions welcome much of the world’s tourism. This tourism is to a large extent seaside beach-based tourism. In the 1980s, after a century of Posidonia-compatible seaside tourism, tourism operators and mayors of coastal cities began to ‘sell’ Posidonia-free beaches and accustom tourists to unnatural, groomed, ‘clean’ beaches. Clean beaches were now free of human-made detritus, which is a positive factor, but also of naturally beach-cast P. oceanica dead leaves, seaweed, driftwood and even shells. It is not clear whether the concept of Posidonia-free beaches actually corresponds to tourists’ requirements, or to the tour-operators’ and mayors’ own perceptions. Experiments involving maintaining in place the Posidonia banquettes, with information boards explaining the ecological and management issues, seem to indicate the latter. In any case, removing banquettes, driftwood, etc., results in a dramatic impoverishment of the beach biota: until recently, beaches were anything but deserts, but that is what they are becoming now! In addition, the Posidonia-free beach doctrine has resulted in catastrophic economic losses. Beaches, the cornerstone of seaside tourism, now unprotected, are washed away by storms and costly sand replenishment accelerates their erosion in a kind of vicious circle. This represents a paradigm example of mismanagement and of its costly consequences. It is probably time to promote the spread of ‘ecological beaches’, i.e. Posidonia-compatible beaches, in order to save the seaside tourism industry, the financial resources of local authorities and, of course, Mediterranean biodiversity. Well-managed beaches are a typical example of what is now referred to as a socio-ecosystem: an ecosystem of which man is a part. This of course means that they must be managed in a sustainable way, retaining their natural characteristics, or most of them, their long-term durability, and finally their value as a symbol of the Mediterranean identity, a vital asset for 21st century tourism.