The Site covers one of the main areas of coastal marshes and tidal bays on the French Atlantic coast. Behind the muddy, sandy or rocky foreshore lie extensive salt meadows, brackish flooded grasslands, dune wetlands and ponds. The area is part of a chain of coastal wetlands that are essential for the conservation of salt-tolerant (halophytic) habitats and species, and include 16 habitats of community interest listed in Annex I of the European Union Habitats Directive. The duration of flooding and the degree of salinity play major roles in the composition of the different plant communities. The Site is a biodiversity hotspot, as it supports over 60,000 waterbirds and is an important nesting site for several bird species. It supports critical stages in the life cycle of a number of fish species, including the critically endangered European eel Anguilla anguilla. The Site is essential for the livelihoods of the local fishermen and salt producers. It is also a popular tourist destination and has appropriate regulations to limit their environmental impact. The area also provides important fresh water resources and plays a major role in flood control and mitigation, coastal stabilization and water purification.