This site consists of a string of permanent freshwater lakes and additional temporarily wet depressions (niayes) lying along a line running north-east from the outskirts of Dakar to around 60 km south-west of St Louis. The lakes lie behind the ridge of coastal sandy dunes, in shallow depressions at 1–4 m above sea-level, over a distance of c.150 km. They are replenished both by rainfall and from the underlying water-table, which lies close to the surface. The wetlands cover 40 km² at low water; at high water, all the lakes can increase their surface area five-fold. The largest lakes lie at the southern end and include Nhiarhol Pool and the lakes Mbao, Mbeubeussé, Retba, Tanma, Youyi (or Malika) and Ourouaye. Lake Retba is the largest, with an open water surface of 5 km by 1.7 km wide at low water. Niaye Hann Mariste consists of a depression covering a surface area of about 30 ha (1.3 km by 200 m), but this dried out completely in 1997 due to evaporation, compounded by abstraction of water for agriculture and building construction. The surrounding vegetation is subjected to seasonal inundation and the area is characterized by the oil-palm Elaeis guineensis. There are also elements of vegetation more typical of the Sudan–Guinea Savanna biome and Guinea–Congo Forests biome (e.g. Prosopis africana and Ficus capensis). These are able to flourish here due to the high moisture content of the soils, which results from the water-table lying close to the surface and the moisture-bearing Alizé winds blowing in from the Atlantic. The whole site is very important in terms of human use, for cattle-grazing, fishing, vegetable, fruit and rice-growing and market gardening (estimated at 90% of national production). Many of the individual lakes also have religious and cultural significance.
See Box for key species. The lakes were included for the first time in the African Waterbird Census in 1997, when nearly 4,000 birds were counted. The niayes have also been the subject of a number of recent more detailed studies (notably by Pierre Reynaud and colleagues at the Institut de recherche pour le développement, IRD), which reveal them to be some of the most ornithologically diverse and most threatened sites along the whole coast of Senegal. In Niaye Hann Mariste alone, Reynaud has recorded 147 bird species, including 51 breeding. The niayes as a whole are particularly important for a wide variety of breeding and wintering waterbirds and also raptors. Up to 500 Phoenicopterus minor were recorded at Lac Tanma in 1990, Falco naumanni is reported in small numbers from the site and there are huge roosts of Milvus migrans.
Non-bird biodiversity: None known to BirdLife International.
BirdLife International (2020) Important Bird Areas factsheet: Niayes (from Dakar to St Louis). Downloaded from http://www.birdlife.org on 28/02/2020.