The 1975, 2000, and 2013 West Africa land use and land cover maps tell a complex story of change— a story that we are only now able to visualize for the first time. While we cannot do justice here to everything that the multi-period maps show, we can point out some of the main trends at the regional level.
Large areas of northern Mauritania, Mali, Niger, and Chad fall within the Sahara Desert. In this arid landscape, land cover and vegetation are quite stable over time. For this reason, only the southern parts of these countries were mapped.
In 1975, natural habitats of the Sahelian and Sudanian Regions such as steppe, sahelian short grass savanna, and sudanian savanna were still the dominant land cover classes across West Africa, representing 18.5, 15, and 32.2 percent of the mapped area, respectively. From north to south, vegetation of the semiarid regions gradually transitions into the more forested landscape of the Upper Guinean countries (from Guinea to Togo) and southern Nigeria. In the 1970s, the extent of West African forest was about 131,000 sq km (2.7 percent of the mapped area), often interspersed with tracts of degraded forest totaling an additional 168,000 sq km (3.4 percent of the mapped area). Cropland was seen widely scattered among the natural landscapes, covering 10.7 percent of the area. Two agricultural regions stood out, the Peanut Basin of Senegal and the Grain Belt of northern Nigeria, whose landscapes were almost totally devoted to cropland.
Fueled by high demographic growth — population grew from 120,000,000 to 334,500,000 inhabitants in 38 years — and a growing demand for food, agricultural expansion accounts for the most spectacular form of landscape change (see Agriculture Expansion) . Cropland expanded rapidly, initially along the country’s main transportation routes, now pervading the whole region. The fastest average annual rates of cropland expansion over the 38-year period were found in Togo, Benin, Chad, Mauritania, and Burkina Faso. Between 1975 and 2013, the area covered by crops doubled in West Africa, reaching a total of 1,100,000 sq km, or 22.4 percent, of the land surface. In every country, agriculture is exerting pressure on the natural landscapes, replacing and fragmenting savannas, woodlands, and forests. Only scattered protected areas are spared from the tide of change and stand out against the agricultural landscape. These protected areas are particularly visible in Burkina Faso, Ghana, Togo, Benin, and Nigeria. Chad and Liberia still maintain great expanses of unbroken wilderness. But change has begun here too.
Another important land cover change in West Africa is the loss of forest (see The Deforestation of the Upper Guinean Forest). The forests of the southern tier countries have become fragmented and degraded where they occur outside of protected areas. Between 1975 and 2013, forest cover was reduced by 37 percent. Today, Liberia has the greatest extent of forest of any country, covering about 37 percent of the national area. To the east, Côte d’Ivoire lost 60 percent (22,000 sq km) of its forest in 38 years, Ghana lost 24 percent (4,000 sq km), and Nigeria lost 45 percent (9,570 sq km). In Guinea, Sierra Leone, and Togo, little remains of the once-extensive forests.
In addition to the changes of large geographic extent, changes among some of the smaller area land cover types are also significant due to their environmental importance. In Mauritania, Mali, Niger, and northern Sahel, the droughts of the 1970s and 1980s degraded or reduced some of the savannas and steppes, removing protective cover and destabilizing the sandy soils. This resulted in a 47 percent increase in sandy areas, or 49,000 sq km. Moreover, driven by population growth, the area devoted to human settlements increased by 140 percent in West Africa (see Settlements Growth) . Most of this urbanization occurred in the coastal region.
West African countries have lost — and are still losing — large extents of their natural land cover classes, replaced by a heavily human-influenced landscape dominated by agriculture.