Lake Bourget and the Chautagne marshes were designated as a Ramsar Site in 2003, mainly for their capacity to host birdlife. The Site was extended by 1,449 hectares in 2024 to include the Lavours marsh, creating an ecologically coherent network of wetlands within the water table of the River Rhône. The extended Site boasts a rare wealth and diversity of species and natural habitats, and its wetlands together offer an essential staging and nesting site for birds migrating on the Rhône corridor between Central Europe, the Mediterranean and Africa. The Site hosts large populations of wintering and nesting common pochard (Aythya ferina) and red-crested pochard (Netta rufina). The vulnerable velvet scoter (Melanitta fusca) and horned grebe (Podiceps auratus) are also found. Fifteen globally, regionally or nationally threatened plant species are present in the Site, as well as various species of globally threatened mollusks, fish, mammals and insects. The Site is used for tourism activities as well as scientific and educational purposes. The Lavours and Chautagne marshes play a significant role in carbon absorption and storage, while Lake Bourget, the largest deep natural freshwater reserve in France, plays an essential role in mitigating the risk and severity of floods.