The Sahel region in Africa, in place of drought, famine, and political crisisis, is the one of interesting place of the globe because of a dynamic ecosystem by climatic variability and human exploitation of biospheric resources. While the scientific debate about the climatology of the droughts in Sahel is still ongoing, results from analysis of different types of satellite- and ground-based data has been generated long term series measurements of vegetation that can be used as proxies for understating the dynamics of variability of the Sahel's environment. A number of studies using these and other data have shown the close coupling among rainfall, land use and primary production in the Sahel.
Potential causes of the greening of the Sahel are ;
1. The increase of greenness in some areas can be explained by increasing rainfall.
2. Human activities such as agricultural or migration are possible factor.
Olsson also answered the question "Is the observed greening a recovery from droughts?".
"Several factors make it impossible to claim that the greening of the Sahel may signal some sort of recovery. “Recovery” implies a return to conditions that existed at some assumed equilibrium point in the past. Regaining comparable greenness after a drought may not mean comparable conditions in terms of vegetation or human well-being. During times of drought, vegetation cover declines which may be accompanied with changes in species composition. Often, these changes are accompanied by changes in soil properties and a new equilibrium point may be established. As a result, when rains return, there is no reason to expect conditions to revert to their original state. Thus, increasing greenness may mean more vegetation, but not necessarily a recovery."
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