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Satellite observations suggest vegetation encourages rainfall in Africa.
More rain makes for more plant growth: that much is obvious. But now a statistical study of satellite images has added weight to the reverse notion: more plants also make for more rain.
The result adds to the impetus to preserve green spaces in dry regions, in order to help prevent deserts from growing and encroaching on agricultural land.
Greenery can have a number of effects on a local climate. Plants are thought to transfer moisture from the soil into the air by evaporation from their leaves, and hold water in the soil close to the surface, where it can also evaporate. What is more, the darker surfaces of plants compared to sandy deserts also absorb more solar radiation, which, along with their rough texture, can create convection and turbulence in the atmosphere. This might create more — or less — rainfall.
All of these effects have been incorporated into climate models. But there has been disagreement about which effects were dominant and why, and how much impact it all has.
The new work concludes that vegetation effects account for around 30% of annual rainfall variation in Africa's Sahel region. The results are reported in Geophysical Research Letters.
