Senegal River Ecosystem

Category: Inland Aquatic Biomes.

Geographic Location: Africa.

Summary: Traversing four countries, this river and its wetlands support a wide array of animal and plant life; habitats are threatened by poor resource management and widespread poverty.

Located in West Africa, and flowing through four countries—Guinea, Mali, Mauritania, and Senegal—the Senegal River is more than 1,000 miles (1,609 kilometers) long. It is formed in the southwestern section of Mali by the confluence of the Bafing and Bakoy rivers, which flow from Guinea’s Fouta Djallon highlands. Like other West African rivers such as the Niger, Volta, and Gambia, the Senegal takes a meandering course that traverses a variety of climates with a contrast of dry and rainy seasons. The Senegal River runs generally northwest in its upper reaches; it forms the border of Senegal and Mauritania, crosses the Talari Gorges, the Gouina Falls, and then tidal marshes as it nears the coastal city of Saint-Louis in northwest Senegal, where it pushes around a large, built-up sand spit, Langue de Barbarie, and flows into the North Atlantic Ocean.

The Senegal’s chief tributary is the Falémé River, which flows along Senegal’s border with Mali. The Karakoro and Gorgol rivers also are major tributaries. Geological changes over time have created a vast patchwork of channels, floodplains, and islands that dot the delta of the Senegal River. Some of the islands of the delta are topped by inland dunes, the largest of which are the Zairé and the Birette.

Upstream, the Senegal is tidal for about 300 miles (483 kilometers). During the rainy season, when the waters are swollen, travel to Mali by water is possible. On both the Senegalese and Mauritanian sides of the river, much of the population makes its living from subsistence farming and fishing; the floodplain is also an ideal place for growing rice.

Biodiversity

The Senegal River region is home to numerous seabirds and waterbirds; Delta de Saloum National Park and Iles de Madeleine National Park are two important bird sanctuaries. Some of the birds found in these preserves are the greater and lesser flamingo (Phoenicopterus ruber and P. minor), pink-backed pelican (Pelecanus rufescens), cormorant (Phalacrocoracidae), reed cormorant (Microcarbo africanus), red-billed tropicbird or boatswain bird (Phaethon aethereus), slender-billed tern, common tern (Numenius tenuirostris), little tern (Sternula albifrons), and a variety of parrots. The slender-billed tern and royal tern are considered to be of international significance. Many of the parrots, and some other species here, are part of one the largest pet-bird export industries in the world.

Senegal’s Djoudj National Park, a United Nations Educational, Scientific, and Cultural Organization (UNESCO) site, hosts 366 bird species, including garganey (Anas querquedula), shoveler (A. clypeata), pintail (A. acuta), black-tailed godwit (Limosa limosa), great white pelican (Pelecanus onocrotalus), and avocet (Recurvirostra avosetta). Approximately 3 million migratory birds fly through the protected areas in the Senegal River each year.

Mangroves provide important habitat for some bird species; the ecoregion contains some of the most northern mangroves on the African continent. This habitat area forms the northern limit for the west African dwarf crocodile (Osteaoaemus tetraspis) and west African manatee (Trichechus senegalensis). Mammals in the river basin include the warthog (Phacochoerus africanus). Several species of crocodile and gazelle have been successfully reintroduced into the area.

More than 800 plant species have been identified within the Senegal River basin in the area formed by Lac de Guiers and the lower Senegal River. It is a biodiverse wetland, and 33 of the species are endemic, that is, found nowhere else. Vegetation along the river’s banks ranges from semi-desert Sahelian grassland and shrubland in the north, to progressively moister Guinea savanna in the south. In the wetter parts, seasonally inundated swamp forests line the rivers. Floodplain vegetation includes perennial grasses and sedges, and reed mace (Typha domingensis) in the main channels.

Due to damming of the river, aquatic plants such as Typha australis, Pistia startioles, and Salvinia molesta have proliferated in the river’s distributaries and in the irrigation canals. Their growth reduces flow velocities and encourages insects and disease that displace other species, reduce fish production, and impede fishing as a commercial enterprise.

Environmental Threats

Various habitats in the Senegal River biome have been threatened by dam construction, depletion of native biota due to irrigation, overgrazing, and some areas of desertification. The Senegal River lies within the Sahelian zone of Africa, a wide band where the effects of climate change are apparent in drought-impacted areas, extensive of deforestation and desertification. The entire region has been beset by high population growth, rapid and uncontrolled urbanization, pervasive and widespread poverty, lack of sustainable development, and ethnic tensions. All these problems make it extremely important to engage in responsible management of the river’s resources.

The country of Senegal has traditionally joined with Guinea, Mali, and Mauritania to manage the Senegal River watershed, but not without difficulty. In 1972, the Organization to Enhance the Senegal River (Organisation pour la Mise en Valeur du Flueve Sénégal or OMVS) replaced the Organization of Senegal River States, but Guinea refused to accept the agreement. Guinean officials finally came on board in 2005.

The Manantali Dam, which serves as a reservoir, is located in Mali. A second dam, Maka-Diama, is situated along Senegal’s border with Mauritania; its purpose is to prevent saltwater from flowing into upstream waters. While the benefits from the dams have been extensive to the human population, changing the natural flow into other waterways has created problems for various ecosystems. Efforts have been undertaken to control invasive plants such as typha; for example, an effort begun in 2022 seeks to involve local communities in the Tocc Tocc Community Nature Reserve, a Ramsar site, in making ecological construction blocks of the weed combined with soil. Other uses include animal feed and biofuel for cookstoves.

Despite the need to cooperate over shared resources, tension has been particularly high in areas that were affected by the building of dams. A glaring example is Lac de Guiers, a shallow, brackish body of water that is one of the most important lakes in Senegal. Before the Diama Dam was built, low-saline water flowed into the lake, but that flow has been stabilized. Because the lake is used for fishing, supplying drinking water for humans and animals, and for crop irrigation, that shift had a serious effect on the local population as well as on the lake’s ecosystems. As saltwater was prevented from following its normal course, parasitic growth became a major health problem, resulting in the spread of several bacterial diseases. Also since the dam was built, malaria has become a year-round problem in the Senegal River area. On the other hand, incidences of waterborne diseases that contribute to malnutrition have decreased because of the more controllable hydraulic conditions in the upper basin.

Although the use of chemical fertilizers was minimal in the past, the Senegal River is now being contaminated by heavy metals and pesticides, including discharge from sugar plantations and dissolved solids that contaminate the waters during the rainy season, as well as from runoff from hydropower plants. Gold panners in the Faleme River, a tributary, also contribute to pollution of the Selegal River. Raw sewage, petroleum, mercury, cyanide, and oil as well as turbidity from digging and sifting for gold are main pollutants in this region. All remain ongoing threats that are being addressed throughout the river basin community. Working with funding from international organizations, OMVS has created an environmental impact program to study and implement ways to mitigate negative effects on this environment.

Bibliography

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N’Diaye, El Hadji Malick et al. “Dam Construction in the Senegal River Valley and the Long-Term Socioeconomic Effects.” Knowledge, Technology, and Policy 19, no. 4 (2007).

Park, Thomas K., ed. Risk and Tenure in Arid Lands: The Political Ecology of Development in the Senegal River Basin. Tucson: University of Arizona Press, 1993.

Sarr, Jacques Ngor. "The Main Tributary of the Senegal River, the Faleme, Is In a Vast Environmental Crisis." Center for Collaborative Investigative Journalism, 7 Oct. 2020, ccij.io/article/senegal-environmental-crisis/. Accessed 31 Aug. 2022.

Stuart, Simon N., et al. Biodiversity in Sub-Saharan Africa and Its Islands: Conservation, Management, and Sustainable Use. Gland, Switzerland: International Union for Conservation of Nature (IUCN), 1990.

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