Land and Water Resources

Sources

Ancient Origins. West Africa was once part of the ancient continent of Gondwana, a single landmass that included Africa, North and South America, southern Asia, and Australia. That continent gradually moved and broke into its separate modern divisions. Africa sits on an extremely old land platform of fold-and-basin structures eroded and leveled by large variations in temperature and humid to arid climates. This environmental dynamic created unevenly distributed sedimentary formations of rough, sandy soil, vast low-lying plains, deserts, huge rift valleys and scattered but spectacular mountains created by volcanic activity. In West Africa, Mount Cameroon is 4,100 meters tall and is the only sizeable mountain in the region. In the western part of the region the primarily sandstone soils and river basins were produced as sedimentary formations.

The Sahara. At the northern edge of the region, the Sahara Desert has consistently challenged the inhabitants of West Africa. This relentlessly expanding region now covers more than fifteen degrees of geographical latitude on the continent. The Sahara has tremendously influenced the history of West Africa—not only as an obstacle to be overcome but also as a filter to limit overwhelming numbers of immigrants—but it has never been an impenetrable barrier to travel, trade, or communications.

The Sahel. One of the two principle vegetation zones in West Africa, the Sahel, or “Desert Shore,” is on the southern edge of the Sahara Desert. It is a belt of semi-arid land that extends for more than 2,500 kilometers (approximately 1,750 miles) from near the Atlantic coast eastward beyond Lake Chad. In modern Africa, the Sahel extends from Senegal in the west, through the countries of Mauritania, Burkina Faso, Niger, and Chad. The largest flat surface on Earth, it has no distinctive mountains. Annual floodwaters and winds redeposit sand, silt, and dust in a dynamic, volatile, and relatively unpredictable pattern. Since at least the beginning of the first millennium, migrating groups of West Africans, especially the Maude speakers, have tried to cope with the environmental rhythms and nuances of the Sahel. This area of persistent hot temperatures, short and drought-resistant grasses (usually less than five feet tall), Thomy shrubs, a few scattered acacia trees (the source of gum arabic), and oases is subject to periodic droughts, sandstorms, and quick bursts of heavy downpours. The annual rains, which have allowed agricultural subsistence and even surpluses for more than two thousand years, generally fall during only three to four months of the year (June through September) and deposit from ten to thirty inches of moisture onto the soil.

Sahel Water Sources. Farmers in this region have been almost totally dependent on this annual rainfall, except in the three parts of the Sahel that include the Senegal River basin in the extreme west, the Niger River bend basin in the middle of the Sahel, and the Lake Chad basin in the east. There, water for irrigation, drinking, fishing, waste removal, and other uses is a combination of rainwater and river or lake water, although evaporation regularly claims around 80 percent of river and lake water, especially during the long dry season, October to May. Except for the drought years, populations in the Sahel have been able to farm on land watered almost solely from the heavy rains that fall during the wet season, sometimes supplemented with well or swamp water. Throughout the 500-1590 period, settlers in the Sahel were able to live on agricultural grain production, livestock herding, and regional and longdistance trade, though the environment challenged them on an almost daily basis.

The Sudanic Grasslands. The second major vegetation zone is a savanna, or grassland, that stretches in a band below the Sahel near the Atlantic coast just south of the Gambia River and extends eastward through the Biu Plateau and the Jos Plateau just south of Lake Chad in the east. The Arabs called West Africa Bilad al-Sudan (Land of the Blacks), which was shortened to “Sudan.” Today, that name is applied generally to the whole region, and the savanna is usually called the Sudanic grasslands. This savanna has gotten smaller in some areas because of desert and steppe desiccation resulting from man-made landscapes and natural processes, but it has spread in other areas because of frequent rain-forest burning. Thus, its exact location has changed since the 500-1590 period. Today it traverses Senegal, the Gambia, the middle of Burkino Faso, and Nigeria, through Chad. The Sudanic grasslands are broad humid plains that cover 75 percent of all of West Africa. They have been central to the evolution of food production, metallurgy, and civilization in the region. The Biu Plateau and the Jos Plateau, both between two thousand and four thousand feet, are the only highland elevations, and they were home to little, if any, early development in the area. Rainfall in the Sudanic grasslands averages approximately twenty to forty inches during a wet season of four to five months, and the grasses there regularly grow from five to ten feet high. These grasses are interspersed with both single, tall, woodland trees and clumps of fire-resistant trees, some growing as high as twenty to thirty feet. Thriving in an area where forest woodlands cannot, the grasses grow on savanna alluvial sediments with high erosion, poor drainage, and little moisture. On the Sahel and the Sudanic grasslands, pearl millet, sorghum, cowpeas, bambara groundnuts, calabash, and cotton were all developed indigenously, while on the savanna the ready availability of timber for firewood and metal smithing, wild fruits, and grassland and tree fowl provided other advantages.

Climate. Africa is considered the most consistently and uniformly hot of all the continents, particularly in the Maghrib region of northwestern Africa and the part of West Africa situated above the Equator. Here, the living conditions are influenced not by temperature alone but also by the amount of rainfall. The Sahara and West Africa are also affected annually by strong anticyclonic winds, which blow northeasterly, and harmattan winds, which blow hot, dry, sand-laden gusts over the entirety of the Sahel and most of the savannas westward from Lake Chad to Senegal.

Global Warming. Modern archaeologists have discovered that during the years 300-1550, particularly between 1100 and 1550, the world went through the Medieval Warm Period, during which global warming created increased precipitation and humidity in Europe and severe dry spells in the Amazon River basin of South America and the American Southwest. They have also connected this weather phenomenon to the major pandemic of bubonic and pneumonic plague (the Black Death) that began in China in the 1330s and swept westward across Asia, Europe, and North Africa until about 1350, recurring in 1361-1363, 1369-1371, 1374-1375, 1390, and 1400. In the Western Sudan during this period, abrupt, shifting patterns of hot winds and increased humidity brought much more rain in some areas while imposing severe, sustained drought conditions on other, once fertile regions. Lake Chad and the Niger fluctuated at record low levels, and the Sahara expanded, overwhelming hundreds of Sahelian

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communities and forcing their inhabitants to migrate in search of arable land and reliable water supplies.

Soil Conditions. Throughout the Western Sudan, the action of differing amounts of water and heat on sediment rocks has formed relatively shallow, tropical soils rich in iron oxide. Generally sandy or hardened clay, the soil is vulnerable to wind and water erosion. In part of the region the hardened, caked surface soil—sometimes called bowe soil—is of little agricultural value. In the savanna and part of the Sahel the structured, brown, and moist soils, protected from erosion by various grass and plant covers, produced the bulk of the food for virtually all the states of the Western Sudan during the 500-1590 period.

Lake Chad. In the eastern Sudan, the major water resource for Kanem-Bornu was Lake Chad, the seventh-largest

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lake in the world and the fourth-largest lake and basin in Africa. Lake Chad annually goes through rather extreme increases and decreases in size, as determined principally by the length and intensity of Sahelian dry-season heat and by the amount of southern highlands rainfall. Typically, the lake may go from a shallow low of ten thousand kilometers to a high of more than thirty thousand kilometers. It is fed from the southeast by the Chari and Logone Rivers, both of which originate in the Central African Republic and the Cameroonian highlands. The Chari River contributes the most water by volume to Lake Chad, an estimated 95 percent of its annual water supply. The Chari is approximately 1,200 kilometers in length and is fed by its tributaries: the Bahr Salamat, the Bahr Aouk, and the Bahr Sara Rivers. The Longone River, which meets the Chari in Chad, near the city of N’Djamena (which is around 1,200 kilometers, or 720 miles, northeast of the Atlantic Ocean), flows approximately 960 kilometers (570 miles).

Major Rivers. The western part of the region has the Senegal, Benue, Volta, Gambia, Faleme, and Niger Rivers. The Niger, at 4,184 kilometers (2,600 miles) in length, is the third-longest river on the continent and flows through virtually every environmental zone in the Western Sudan. The Senegal and Faleme were important in the origin and development of the early Takrur Empire, which rivaled the Empire of Ghana by the tenth and eleventh centuries. These rivers were both adjacent to Bambuk (in the western part of present-day Mali), the first major source of Sudanic gold. The Benue feeds the Niger River, and the Volta was instrumental in the rise of the Niani people of Mali. The Gambia was the western boundary of the Sudanic savanna zone. Though the Senegal, Benue, and Faleme lacked the overabundance of rapids and waterfalls that hindered navigation on most of the significant African rivers, these rivers were never recognized as major transportation assets to the population of the Western Sudan, principally because of delta swamps, large extremes in their annual flows, and river-blocking sandbars at their mouths.

The Niger River Basin. The Niger River and Lake Chad valleys are two of the six largest basins in the continent. In terms of hydrology, one of the biggest geographical influences on the history of the Western Sudan has been the Niger River and its delta system. The Niger basin extends from five to sixteen degrees north latitude. The river rises in the coastal mountains of Guinea, just 150 miles inland from the Atlantic Ocean; it flows northeast toward the Sahara Desert, entering Mali; after it reaches Timbuktu, it turns eastward for about 250 miles; then it loops in a southeasterly direction, flowing through the city of Gao into Niger and forming part of its border with Benin. The river ends in Nigeria, finally reaching the Gulf of Guinea, where it forms a huge delta system of spider-like outlets flowing through mangrove and sand. Bolstered by annual rainy-season flooding, the middle Niger flows through part of the Sahel and the semidesert region around Timbuktu. It is fed by the Benue River downstream. The middle Niger, which is also called the Niger Bend area, has attracted large residential populations throughout its history and figured prominently in every one of the ancient African kingdoms.

Sources

S. Diarra, “Historical Geography: Physical Aspects,” in Methodology and African Prehistory, edited by J. Ki-Zerbo, volume 1 of General History of Africa (London: Heinemann / Berkeley: University of California Press / Paris: UNESCO, 1981), pp. 316-332.

A. T. Grove, The Changing Geography of Africa (Oxford: Oxford University Press, 1989).

Akin L. Mabogunje, “The Land and Peoples of West Africa,” in History of West Africa, edited by J. F. A. Ajayi and Michael Crowder, second edition, volume 1 (London: Longman, 1976), pp. 1-32.

Marijke van der Veen, ed., The Exploitation of Plant Resources in Ancient Africa (New York & London: Kluwer Academic / Plenum, 1999).