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The African Sahel and many of the people it has tenuously supported are retreating southward, giving way to the inhospitable Sahara Desert. Why is the Sahara spreading? Is unsustainable land use or climate change to blame? And, if climate change is a factor, how much of that change is natural and how much results from all the greenhouse gases people have pumped into the atmosphere? Before an effective attempt can be made to stop desertification, its causes-and particularly any self-reinforcing cycles-must be understood.
Hulme et al. (Sun,) studied this question.