The humid savannas and forest fragments of the Guinean Highlands provide a stark contrast to the arid Sahelian landscapes of the northern parts of the basin. The ecology, land use and ecosystem services provided by the Niger River and its tributaries vary accordingly. Near the origin of the river annual rainfall measures over 1,200 mm, which sustains ecosystems that are typical of the humid savannas of West Africa, with open grasslands interspersed by dense woodlands and gallery forests bording the rivers. In this zone, rainfall is sufficiently high to sustain rain-fed rice production and a variety of other water-demanding crops.
Going in northeastern direction, the landscape changes as it becomes progressively drier. Tree cover declines, savanna woodlands become more open and species like Faidherbia albida, Parkia biglobosa and other dry savanna species become characteristic features of the landscape. As rainfall gets lower, people depend more on the river for their water requirements. In central Mali the Niger and Bani Rivers enter the Sahel, a semi-arid belt with erratic rainfall which can be considered a transition zone between the savanna zone and the Sahara. Here both rivers spread out into the Inner Niger Delta, one of the largest wetlands on the African continent.
The Inner Niger Delta (IND) is a dynamic and productive ecosystem that supports more than 1.5 million inhabitants and has exceptional ecological value. It is a wetland of major international importance, which is characterised by the seasonal flood pulse that inundates vast areas after the rainy season. People use the incoming water for agriculture and fishing, cattle graze on the floodplains and floating bourgou fields, and millions of birds use the delta as a wintering site or to breed. The annual flood cycle of the IND was little affected by human activities until the 1950s. However, during the latter half of the century, the area has been strongly affected by the combined impacts of climate change, water extraction for industrial agriculture and the construction of upstream hydraulic infrastructure.
This section of the Observatoire provides data and information on the ecology and biodiversity of both sub-basins. More information on protected areas, ecosystems and vegetation, vulnerable species and ecological hotspots in the basin can be found under the different subthemes.