The Sahel zone is an approximately 400 km wide transition area between the Sahara and the thorn savannah to the humid savannah regions of Sudan in Africa. Its east-west extension is 5000 km. It extends from the Atlantic coast in the west to the Nile in the east. Seven states have a share in the Sahel zone. Around 30 million people live here.
This zone is extremely vulnerable to drought, as demonstrated by frequent periods of drought with famine. The low amounts of precipitation per year or the lack of it make life and economy in the area difficult. Grass pastures wither and only acacias and thorn bushes survive due to their deep roots. The sparse vegetation allows almost only nomadic livestock farming. The hikes of the nomads determine the search for food and water. The creation of deep wells led to a changed way of life. Only part of the family moved with the herd, the others could settle down and do chopping. Increased animal husbandry and overuse result in soil leaching and drying out. Together with the wind blowing, this leads to an expansion of the desert.
Desertification is a global problem. 400,000 people are affected in the Sahel. Long-term aid programs for those affected by famine and countermeasures to desertification are created by development aid experts around the world.
Sahel is an Arabic word and means “shore”.
The Sahel is an endangered habitat and is characterized by major economic and survival risks.
The states of Senegal, Mauritania, Mali, Burkina Faso, Niger, Nigeria, Chad, Republic of Sudan, Eritrea, Djibouti and Somalia have a share in the Sahel (Fig. 1).
Climate and vegetation
The Sahel is an area at risk from drought. The drought disasters are devastating. Many people and animals fall victim to them.
Temperatures are high all year round. Only 150 to 500 mm of precipitation fall annually. The rainy seasons are determined by the northward migration of the intertropical convergence (ITC) triggered. It follows the highest levels of the sun between the tropics with a one to two month gap. The rainy season is between May / June and September / October. In the Sahel in the north there are regions with only one rainy season in July / August. The rainfall is extremely irregular. The migration of the rain fronts is subject to great fluctuations. There are periods when there is no rain at all. The precipitation values are therefore only long-term averages.
The vegetation is extremely sparse. It adapts to the eight to ten month dry season. The characteristic vegetation in the core area is the thorn and shrub savannah. It is characterized by poor grasses, shrubs and thorn bushes. To the north it turns into semi-desert, to the south into dry savannah. This is characterized by high grass corridors and sparse trees.
Continuous rivers cannot arise due to the low rainfall. The major rivers Senegal, Niger and Nile have their source in more humid tropical areas. When crossing the Sahel zone, they lose a lot of water through evaporation. Lakes, river beds and depressions dry out during periods of drought. After the rainy season they carry water again for some time. Groundwater escapes near the surface in the dry season. Fossil groundwater resources from past earth ages have been found in the depths.
Economic use of the Sahel zone
In the northern part of the Sahel zone, low rainfall and sparse vegetation allow almost only extensive nomadic livestock farming.
The grass stocks develop differently according to the annual rainfall. Sheep, goats and cattle must be grazed wherever fodder is available. The size of the herds is limited by feed and water scarcity. In dry periods, the nomads move to the more southerly, more humid dry savannah. This creates conflicts with the local farmers. By creating deep wells, the herds could be enlarged and their walking distance reduced. From a depth of over 100 m, water is pumped to the surface with the help of motor pumps. These measures also led to a change in the social behavior of the nomads. Only part of the family moved with the herd, the rest were able to settle down. As a result of the improved living conditions, the proportion of the population of nomads increased and at the same time the need for food. Today around 20 million nomads live in the Sahel.
Where at least 400 mm of precipitation falls, the land can also be used for arable farming in depressions and valleys. Hacking is carried out in the southern part of the Sahel zone. The hoe farmers clear and burn trees, bushes and grass. The ashes are used as fertilizer. Becomes self-sufficient Millet is grown, but corn and vegetables are also planted. Since the yield is very low, cattle is also farmed. After three to six years the ground is exhausted. The hoe farmers give up their fields and look for new ones.
Due to the growing population and the resulting need for food, the period of natural recovery of the soil had to be shortened. Although it has been possible to expand arable farming further north through chemical fertilization, the excessive use of the soil has far-reaching negative consequences.
The desert expands as a result of soil leaching with subsequent soil drying and the formation of wind and dunes in places protected from the wind.
The crop yields are no longer sufficient to feed the population. Another reason for the destruction of the soil is the large-scale logging as firewood. Today there are already up to 100 km² of tree and bushless areas in the Sahel and they are constantly increasing.
Nomads and hoe farmers have so disrupted the ecological balance of nature that the effects of periods of drought are intensified. If there is no precipitation for several years, as is typical for the Sahel zone, the situation leads to famineas most recently 1969–1973, 1983–1985 and 1989/90. In the drought of 1969–1973, 25 million head of cattle starved to death and more than 100,000 people died.
Desertification and international aid
Desertification comes from the Latin word desertificare = to devastate. The increasing expansion of the world’s deserts into arid and semi-arid areas (Fig. 3) due to excessive use of the desert fringes by humans and animals is a global problem. Population growth, increased livestock farming and land use lead to the destruction of natural vegetation, overexploitation of the soil and water reserves. Every year agricultural land the size of Baden-Württemberg is lost through desertification in the arid regions of the world. Desertification affects 400 million people in the Sahel region of Africa.
Measures are being taken around the world to combat desertification. The aim of the UN Convention on the Protection of the Global Environment is to adapt land use to natural restrictions. For the people in the Sahel at risk of starvation, short-term emergency aid is necessary, such as food deliveries, medicines, doctors and development workers.
Long-term aid can improve people’s living conditions in the long term. They are financed by development aid from industrialized countries. Proposals to prevent soil erosion and thus the spread of the desert have been made by experts:
In the regions of the hacking farmers, the rapid drainage of rainwater is to be prevented by building small dams.
Pasture farming in the drought-prone areas must be maintained as an adapted form of farming.
It is necessary to plan the pasture hike and deep wells may only be used in dry periods.
Plans for targeted reforestation must be drawn up, but it must also be possible to cut wood in the future.
The use of solar energy z. B. for cooking would be useful. However, the systems are currently still too expensive. The daily rhythm of the locals also requires the main meal to be taken in the evening. The ecological balance of the Sahel must be restored in the long term.