The desert

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désert climat monde irrigaation danger

It seems paradoxical to evoke desertification in a world where precipitation is going to increase, but it is not so. The scenarios are relatively vague about what will happen to semi-arid regions like the Sahel, Australia the Mediterranean Basin, the southwest of the United States, Southern Africa and the Brazilian sertão. However, those living in these fragile regions are at the mercy of environmental changes.

Desertification, defined as the degradation of soil that reduces its organic productivity, can even occur in regions that get enough rainfall. Collecting wood for cooking reduces the number of trees. Herds overgrazing, soil impoverishment and erosion and the overexploitation of non-renewable groundwater also degrade mankind’s living conditions.

What will global warming do to the Sahel? This 800 km strip of land is 7 000 km long, from Senegal to Sudan. It joins humid tropical Africa in the South to the Sahara in the North and is the world’s largest desert. If the African monsoon does not come, famine will strike farmers and breeders as it brings the only useful rain once a year, from July to September. The recurrent droughts in the 1970s and 1980s show this. Climatologists believe developing global warming could already have been part of the problem.

Climatologists are being careful about the 21st century but models show the African monsoon’s increased variability. Some models show that precipitation in the Sahel will increase by 20 to 30% towards the middle of the century. However, this temperature increase will also worsen evaporation.

This will have a major impact as animal husbandry and farming are key resources for African populations.


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