 The southernmost part of the country lies in the West Sudanian Savanna ecoregion.Wetlands are important and the two main protected areas are the Banc d'Arguin National Park which protects rich, shallow coastal and marine ecosystems which integrates with the arid Sahara desert and the Diawling National Park which forms the northern part of the delta of the Senegal River.Elsewhere in Mauritania wetlands are normally ephemeral and rely on the seasonal rainfall and may be very important for migratory birds.