One of the freshwater ecoregions in Mauritania is the Dry Sahel. Many freshwater habitats characterize this ecoregion, from oases, streams to seasonal and permanent pools. This ecoregion occupies the transition zone between the Savanna ecoregion and the Sahara Desert. The region has a hot and tropical climate and receives an annual average rainfall of 30-50 mm. This ecoregion is particularly rich in avifauna, from crustaceans, mollusks to fish species and amphibians. The region is also a significant stopping point for migratory birds including the white pelican and red knot. Among the region’s environmental threats are agricultural expansion and over-grazing which have led to desertification.