Western Africa is made up of two eco-geographical areas: first, the Sahel countries, including Burkina Faso, Cape Verde, Gambia, Guinea-Bissau, Mali, Mauritania, Niger and Senegal, which make up the dry region of West Africa, and, second, the countries of the Gulf of Guinea, including Benin, Côte d’Ivoire, Ghana, Guinea, Liberia, Nigeria, Sierra Leone and Togo, which make up the humid region of Western Africa.

Figure 19: Average cumulative rainfall (mm) in Western Africa 1968–1998 The climatic characteristics of the sub-region are discussed in Chapter 2: Atmosphere. It is subject to tropical climatic variations, resulting in high annual temperatures and heavy rainfall which steadily decline towards the Sahara Desert. Rainfall is of vital importance in determining climate in tropical areas in general, and in Western Africa in particular, because it varies so widely from area to area and season to season it represents a limiting factor for rain-fed agriculture, which provides the economic base of the countries. In the Sahel region, there is one rainy season, lasting between two and five months, while the Gulf of Guinea countries have two rainy seasons. Western Africa is characterized by four types of climate (GRAIN 2002):

  • Sahelian climate: the rainy season lasts no longer than three months; rainfall is irregular and does not exceed 500 mm;
  • Sudanian climate: rainfall does not exceed 800 mm in northern Nigeria, and is no more than 1 000 mm in southern Mali; and
  • Humid tropical climate: distinguished by a bimodal rainfall pattern, with average annual rainfall of 1 500 mm;
  • Equatorial climate: localized essentially along the Gulf of Guinea, where rainfall can exceed 2 000 mm.

Market Forces scenario

In this scenario, agricultural production prevails over the other sectors. This results in a market economy that does not take environmental matters into account and undermines government initiatives. Growing trade, driven by the forces of globalization, results in more extensive farming and an increase in the area of cultivated land. Food production levels rise at the cost of environmental considerations. Where necessary, technology is brought into play to meet international trade demands and production requirements. As a consequence, soil erosion due to overproduction worsens, and this situation is exacerbated because of the increasing incidence of droughts.

Deforestation associated with high levels of GHG emissions could cause acid rain, further contributing to soil erosion. These changes have implications for food security in Western Africa, particularly in the most vulnerable region of the Sahel. Increasing concentrations of GHG emissions in the atmosphere affect climate variability, including shorter rainy seasons, and lead in the long term to climate change.

Locust invasions increase due to climate change continue to cause food deficits as no action is being taken to reverse this. Consequently, the food situation worsens in certain areas of Burkina Faso, Chad, Mali, Mauritania, Niger and northern Senegal. The invasion of the desert by locusts is a consequence of climate variability. The unexpected rains provoke a proliferation of locusts, which are normally in a state of dormancy (FAO 2004). The changing climate (in this case an upsurge in rainfall) cause the disruption of this dormant state. Damage to millet crops and grazing land attributable to such agro-climatic conditions has been recorded throughout Cape Verde and on a more localized scale in Burkina Faso, Mali, Mauritania, Niger and Senegal (FAO 2005a). This trend is likely to worsen.

Accordingly, the overall production of cereals (millet and sorghum), the largest food crops of this part of Africa, declines, increasing food insecurity and affecting prices for consumers. Even the coastal countries (Gulf of Guinea, humid Western Africa), which have until now enjoyed a certain measure of climate security (abundant rainfall), see their resources dwindle under the influence of environmental degradation and they too become vulnerable. Decreased rainfall and increased evaporation linked to high temperatures leads to water shortages and deterioration in water resources. Hydrological imbalances cause the collapse of certain economic activities. Reduced river flows have a negative impact on hydroelectric production. And, hydroelectric energy production is affected in Benin, Côte d’Ivoire, Ghana and Togo. This is a replica of the events of February 1998, when Ghana faced an energy crisis caused by a drop in the water level of Lake Volta (Niasse and others 2004). Successive years of drought continue to reduce the size of humid zones in many regions. Despite some patchy rains, the general decline in rainfall continues. Sporadic droughts affect river systems, agricultural production, supplies of drinking water and hydroelectric production.