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Tropical rainforest clearance threatens global crops

Logging in the Amazon Logging in the Amazon Dr Morley Read/Shutterstock
22 Dec
2014
When deforestation occurs in South America, Southeast Asia and Africa, the effects on crop production will be felt in areas as far away as the US Midwest, Europe and China, according to a new study published in Nature

‘Tropical deforestation delivers a double whammy to the climate – and to farmers,’ said Deborah Lawrence, Professor of Environmental Sciences at the University of Virginia, the study’s lead author.

The research presents evidence that tropical deforestation is affecting local and regional climates. In Thailand, the dry season sees even less rainfall than before due deforestation. Amazonian rainfall that was once predictable has also shifted, according to the research. Deforested areas experience rainfall two weeks later than usual.

‘Most people know that climate change is a dangerous global problem, and that it’s caused by pumping carbon into the atmosphere. But it turns out that removing forests alters moisture and air flow, leading to changes – from fluctuating rainfall patterns to rises in temperatures – that are just as hazardous, and that happen right away,’ says Lawrence.

Deforestation’s influence extends beyond the tropics. The United Kingdom and Hawaii could see an increase in rainfall while the US Midwest and Southern France could see a decline. The global connections between deforestation and climate are due to teleconnections. These ripples in the atmosphere are due to an increase in temperature in the tropics due to deforestation that generates upward moving air masses. The ripples can spread across the globe.

Complete deforestation in the Amazon Basin would reduce rainfall in the US Midwest, Northwest and some of the South during farming season. Deforestation in Central Africa would reduce rainfall in the Gulf of Mexico, but increase it on the Arabian Peninsula, according to models.

‘This does not change, no matter what you do. No matter what kind of model you use, temperature increases occur, whether it’s half a degree, a full degree or two degrees,’ said Lawrence.

Deforestation in a region would probably lead to a 10–15 per cent reduction in rainfall for that region, according to the research.

‘Farmers, so reliant on consistent and reliable growing conditions, could lose their bearings and even their incomes, when facing these ups and downs in temperature and rainfall,’ Lawrence said. ‘While farmers may ultimately adapt to shifts in the season, it’s difficult – if not impossible – for farmers to adapt to increased floods or parched soils.’

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