Inner Niger Delta flooded savanna

• Category: Inland Aquatic Biomes.
• Geographic Location: Africa.
• Summary: This biome, located in the impoverished nation of Mali, is home to a wide range of animal and plant life, but threatened by poor local governance and climate change.

The Inner Niger Delta comprises an expanse of lakes and floodplains in the otherwise semiarid Sahel-Sahara Desert area of the West African country Mali. The region has been of socioecological importance in the twenty-first century because of the discovery and exploitation of crude oil and the effect these activities have had on the region’s plant and animal life.

The 54-mile- (87-kilometer-) wide lush delta extends for 264 miles (425 kilometers), tapering into a braided river near Timbouctou, where the Niger River curves to the east. The Niger is the main flood source of the savanna, and its main tributary is the Bani River in Côte d’Ivoire and Burkina Faso; smaller streams flow down from the Dogonland Plateau. The Niger originates on the Fouta Djallon highlands of Guinea and extends 2,548 miles (4,100 kilometers) before flowing into the Atlantic Ocean on the coast of Nigeria.

The surface level of the flooded savanna drops only 26 feet (8 meters) from beginning to end. It consists of a vast network of river channels with levees separated by low, clay-based floodplains that expand to cover 7,722 square miles (20,000 square kilometers) during the four-month rainy season of June to September; it then shrinks to 1,506 square miles (3,900 square kilometers) during the dry season.

The delta’s climate is tropical. Most of the year, the region is hot and dry with temperatures rising to 104 F (40 C) and hot winds blowing in from the Sahara Desert. Precipitation varies across the region. In the south, the rainy season of July to October records annual rainfall of 29 inches (750 millimeters), and in the north, the slightly shorter rainy season of July to September provides a mean annual precipitation of approximately 10 inches (250 millimeters).

Biodiversity

The southern portion of the delta is a low-lying floodplain filled with such grasses as Acroceras amplectens, Echinochloa pyramidalis, E. stagnina, and Eragrostis atroviriens. In the areas used for animal grazing, gamba grass (Andropogon gayanus), Bermuda grass (Cynodon dactylon), and yellow thatching grass (Hyperthelia dissoluta) dominate. Along the water areas, Mimosa asperata and Salix chevalieri grow above an understory of Cyperus maculatus. In the south, the tree types include Diospyros spp. and Kigelia africana, while in the north the delta features emergent sand ridges and Hyphaene thebaica and Borassus aethiopum palms, plus Acacia nilotica, Guarea senegalensis, Mimosa asperata, and Ziziphus mauritiana in elevated areas.

The Inner Niger Delta Flooded Savanna biome provides essential habitat for numerous wetland birds. Wintering in the delta are approximately 500,000 garganey (Spatula querquedula) and up to 200,000 pintail (A. acuta), plus ferruginous duck (Aythya nyroca), white-winged tern (Chlidonias leucopterus), ruff (Calidris pugnax), black-tailed godwit (Limosa limosa), and more. The delta provides important breeding locations for African spoonbills (Platalea alba) and purple swamp-hens (Porphyrio porphyrio).

Other birds in the delta include cormorant, heron, spoonbill, ibis, and black crowned crane (Balearica pavonina pavonina).

Approximately 110 fish species are found in the inner delta, but few of them are endemic (found only here). Among those are the Mochokidae catfish (Syndodontis gobroni) and Gobiocichla wonderi. There are twenty endemic freshwater species from five families: Denticipidae, Pantodontidae, Phractolaemidae, Hepsetidae, and Gymnarchidae.

Although most large mammals no longer use the delta—having been removed by humans—the African manatee (Trichechus senegalensis), also known as sea cow, lives in the rivers and feeds on underwater plants. Other aquatic mammals include the hippopotamus (Hippopotamus amphibius) and the endangered pygmy hippopotamus (Hexaprotodon liberiensis), semi-aquatic sitatunga (Tragelaphus spekii), marsh mongoose (Atilax Paludinosus), and the spotted-necked otter (Hydrictis maculicollis). Hunters and poachers have severely reduced the populations of the hippo.

Shore mammals include: Libyan striped weasel (Ictonyx libyca), African civet (Civetticutus civetta), caracal (Felis caracal), serval (F. serval), striped hyena (Hyaena hyaena), patas monkey (Erythrocebus patas), sand fox (Vulpes pallida), and African wild cat (Felis silvestris). Scientists believe that small populations of roan antelope (Hippotragus equinus), red-fronted gazelle (Gazella rufifrons), dorcas gazelle (G. dorcas), and dama gazelle (G. dama) still exist.

Human Activity and Climate Change

The ecosystem in the Inner Niger Delta is essential to human life in the Sahel region. Climate change and human activities have led to a significant decrease in the region's water quantity and quality. Limited rains, poor governance, the construction of upstream dams, increasing human population—over one million people depend on the Inner Niger Delta wetland for survival—and land-use changes have amplified pressure on the delta. Extreme grazing and severe droughts have resulted in land degradation and pasture loss. Deforestation, erosion, and governmental negligence have contributed to habitat deterioration.

Several attempts have been made to salvage the area, but the impact has been minimal. In 1987, Lac Horo, Lac Débo (also called Walado Debo), and the Séri floodplain complex were named individual Ramsar sites. In 2004, the whole Inner Niger Delta region was named a Ramsar Wetland of International Importance under the name Delta Intérieur du Niger. However, the delta region is largely unprotected. Researchers advocate for holistic regional assessments of the floodplain in terms of environmental flows, the timing and volume of flows or water levels to meet the needs of the ecosystems, and floodplain management.

Climate change continues to stress the already hot environment, with rising temperatures that could increase drought frequency, accelerate biodiversity loss, and increase crop pest infestation. Human health, safety, and sustainability are at risk as the region's water supply becomes more polluted and scarce. The delta is critical for cultivating rice, livestock, fishing, and other agricultural practices. As water resources decrease, competition may increase in the region, leading to tension and potential violence between groups.

Bibliography

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Dodman, T., H. Y., et al. African Waterbird Census 1998. Wetlands International, 1999.

Dungan, Patrick J. "Wetland Conservation: A Review of Current Issues and Required Action." International Union for Conservation of Nature and Natural Resources, 1990, portals.iucn.org/library/sites/library/files/documents/1990-011-En.pdf. Accessed 19 Dec. 2024.

Frenken, Karen, et al. "Irrigation Potential in Africa: A Basin Approach." Food and Agriculture Organization of the United Nations, 1997, openknowledge.fao.org/items/57be9ea9-4aa6-4419-a910-196fb28788d2. Accessed 19 Dec. 2024.

Martin, Emma, and Neil Burgess. "Inner Niger Delta Flooded Savanna." One Earth, 23 Sept. 2020, www.oneearth.org/ecoregions/inner-niger-delta-flooded-savanna. Accessed 19 Dec. 2024.

O'Brien, Gordon C., et al. "Sustainable Floodplains: Linking E-Flows to Floodplain Management, Ecosystems, and Livelihoods in the Sahel of North Africa." Sustainability, vol. 12, no. 24, 2020, doi.org/10.3390/su122410578. Accessed 19 Dec. 2024.

Ticheler, H. Fish Biodiversity in West African Wetlands. Wetlands International, 2000.