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| Tunisia. Nefzaoua. Kebili Oasis. Kebili is the principal oasis of Nefzaoua, in southern Tunisia. Surrounded by sand, this fertile zone is irrigated, like all Oases, by an outpouring of the ground water which gives birth to many springs. Motor pumps used to exploit ground water enabled farmers to expand and multiply irrigated areas, transforming the pre-desert steppe into a modern agricultural space. But the shallow ground water supplies quickly ran dry, and when deeper layers were drilled, they in turn also ran dry. The dash ahead, or rather down, will soon come to an end. What has been overlooked is that some water supplies are nonrenewable. It is not so much a matter of the desert advancing as the steppe being degraded by human activity. The abandoned areas are invaded by small sand dunes driven by the wind. Gradually the dunes link up, like moth-holes in a garment, until there is nothing left but desert. Natural and human causes thus join together in advancing the Sahara; in the Sahel, to the south, similar activities are taking place with similar effects. |
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