The Sahel region, a semiarid area spanning the entire African Sahara from the Atlantic Ocean to the Red Sea, suffered from several devastating droughts and famines between the late 1960s and the early 1990s with rainfall levels steadily declining from the 1950s to the 80s. According a U.N. report, the outlook for the people in the Sahel looked bleak.
However in sharp contrast to this gloomy outlook, it looks like global warming has had a positive effect on the Sahara and the Sahel.
The Sahara is actually receding, with vegetation arising on land where there was nothing but sand and rocks before. The southern border of the Sahara has been gradually retreating since the early 1980s, making farming viable again in what were some of the most desolate parts of Africa.
There has been a spectacular regeneration of vegetation in northern Burkina Faso, which was devastated by drought and advancing deserts 20 years ago. It is now growing so much greener that families who fled to wetter coastal regions are starting to come back. There are now more trees, more grassland for livestock and a 70% increase in yields of local cereals such sorghum and millet in recent years.
Vegetation has also increased significantly in the past 15 years in southern Mauritania, north-western Niger, central Chad, much of Sudan and parts of Eritrea. In Burkina Faso and Mali, production of millet rose by 55% and 35% respectively, since 1980. Satellite photos, taken between 1982 and 2002, revealed the extensive re-greening throughout the Sahel. Aerial photographs and interviews with local people have confirmed the increase in vegetation.
Causes of the greening
The greening cannot be explained solely by the increase in rainfall. There were vegetation increases in areas where rainfall was decreasing, suggesting another factor was responsible for the greening in these areas.
This other factor might have been the rise of atmospheric CO2 levels. The aerial fertilization effect of the ongoing rise in the air’s CO2 concentration increases greatly the productivity of plants. The more CO2 there is in the air, the better plants grow. Rising atmospheric CO2 levels also have an anti-transpiration effect, which enhances the water-use efficiency of plants and enables them to grow in areas that were once too dry for them.
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