The Site is France’s largest natural lowland lake, with a surface that in winter reaches 6,300 hectares, when its meadows and other flood-prone areas are flooded, while in summer it shrinks to less than 3,000 ha during the low-water period. The Site hosts more than 1% of the global populations of northern shoveler (Anas clypeata), gadwall (Anas strepera), purple heron (Ardea purpurea), common pochard (Aythya ferina), whiskered tern (Chlidonias hybrida) and black-crowned night heron (Nycticorax nycticorax). It also supports almost 500 important plant species, including many that are nationally or regionally threatened or protected. Human activities include fishing, hunting and tourism, and also education and scientific studies. It is also important for its archaeological, historical and ethnographic values. Some alien invasive animal species might pose a threat to the ecosystem.