Celebrating 25 Years of Action for Biodiversity

Mauritania has one of the world’s richest maritime facades in fish resources and boasts six types of marine turtle [ ] 154 The rehabilitation of the estuary of the Senegal River mouth in Diawling National Park The lower basin of the Senegal River used to be a complex natural estu- ary where the salinity level varied according to the seasons. During the rainy season, when the rainwater flooded the area, it was almost cool, while during the dry season, when the water level dropped and seawater entered the delta, it became brackish. With the construction of the Diama dam, the pseudo-ecosystem of the delta suddenly became divided into a permanent freshwater ecosys- tem upstream of the dam, while the downstream area became deprived of freshwater for most of the year. It thus turned into a hyper-saline habitat. However, efforts have been made to restore pre-dam conditions in a part of the area currently known as the Diawling National Park, on the Mauritanian side of the river. Eighteen years later, the results have been impressive. The area has once again been transformed into a wetland where vegetation and fish are re-emerging, mangroves are thriving, and notably where water birds are returning. The importance of the area for marine biodiversity is not very well known. However, it is recognized as the breeding and nursery ground for nearly 100 marine, estuarine and freshwater species of commercial interest. It is especially the place for the spawning and growth of mullet and many species of shrimp. The mangroves of the southernmost part of this humid coastal area are much more diverse and dense than the mangroves of the Arguin Park. Rhizophora racemosa and Avicennia germinas are among the principal tree species. The Diawling National Park is also a very important site for the migration of tropical palearctic and Afro-tropical migratory birds. The biological diversity of this site is related to the estuarine nature of the site with an artificial water supply. The flooding process of the area is a system in which most nutrients are stored in the biomass. Large breed- ing colonies of herons, egrets and cormorants nest at the level of the Tamarix stands adjoining the coastal dune. The massive decomposition of the biomass during floods provides trophic resources for the various bird species. It is followed by a period of production (vegetation, fauna, micro-organisms, fish) and repro- duction. The birdlife adjusts to this cyclical process. Afro-tropical species breed in a cycle and the arrival of Palearctic migrants coincides with the decline of the waters and the abundance of food. S ituated in north-west Africa, the Islamic Republic of Mauritania spans 1,030,000 km 2 . This arid country can be divided into two regions: the Saharan that makes up 75 per cent of the territory and is composed of grass and shrub steppes, with a low amount of biogenetic resources; and the Sahelian, that contains plant formations such as shrubs and trees. Two azonal domains can be superimposed on this distinction, with the coastal sector in the west, bordering the Atlantic Ocean, and the valley of the Senegal River in the south. Amatlich, Mauritania John Spooner Mauritania