(Left) The change, in millimeters per day, in daily average precipitation after total Amazon deforestation compared to before deforestation. The pink to dark-pink range indicates a drop in precipitation of up 1.6 mm less per day once the Amazon is gone. Areas with statistically significant changes are hatched. (Right) The model indicated that the surface temperature in the Amazon region would increase by up to 2 degrees Celsius (darkest green) over a 14-year period following deforestation. The region of Amazon deforestation is boxed. Graphic: Medvigy, et al., 2013

By Rhett A. Butler
8 November 2013

(mongabay.com) – Complete deforestation of the Amazon rainforest could reduce rainfall in the Pacific Northwest by up to 20 percent and snowpack in the Sierra Nevada by up to 50 percent, suggests new research published in the Journal of Climate.

The study is based on high resolution computer modeling that stripped the Amazon of its forest cover and assessed the potential impact on wind and precipitation patterns. While the scenario is implausible, it reveals the global nature of the ecological services afforded by the world's largest rainforest.

"The big point is that Amazon deforestation will not only affect the Amazon — it will not be contained. It will hit the atmosphere and the atmosphere will carry those responses," said first author David Medvigy of Princeton University in a statement. "It just so happens that one of the locations feeling that response will be one we care about most agriculturally. If you change the snowpack in the Sierra Nevada, where most of the irrigation for California's Central Valley comes from, then by this study deforestation of the Amazon could have serious consequences for the food supply of the United States."

Reduced rainfall and snowpack could also increase regional vulnerability to fire and affect energy production since much of California and Washington's power comes from hydroelectric dams.

The model found that complete deforestation of the Amazon would create an area of dry air around the equator, pushing wetter and cooler air south. The effect would be similar to the pattern seen in El Niño years, but with a twist that leaves Southern California drier. The rain typically seen in California during el Niño would instead by dumped over the ocean. [more]

Amazon deforestation could cause droughts in California



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