Amazon Valley Drought Deforestation And Warming

During 2005 a severe drought spread through the Amazon Valley at the same time that satellite surveys indicated that damage from logging in the same area had been 60 to 120 percent more than previously reported. "We think this [additional logging] adds 25 percent more carbon dioxide to the atmosphere" from the Amazon than previously estimated, said Michael Keller, an ecologist with the U.S. Department of Agriculture's Forest Service and coauthor of an Amazon logging inventory published in Science (Asner et al., 2005, 480-481; Naik and Samor, 2005, A-12).

This new survey differed from others that measured only the clear-cutting of large forest areas. The study by Asner and colleagues included these measures of deforestation and added trees cut selectively, while much of surrounding forest was left standing in five Brazilian states (Mato Grosso, Para, Rondonia, Roraima, and Acre) which account for more than 90 percent of deforestation in the Brazilian Amazon (Asner et al., 2005, 480). In addition, the Amazon Valley's worst drought in about 40 years was causing several tributaries to evaporate, probably contributing even more carbon dioxide via wildfires.

In some areas of the Amazon Valley, the drought was the worst since record keeping began a century ago. Some scientists asserted that the drought was most likely a result, at least partially, of a rise in water temperatures in the tropical Atlantic Ocean that also played a role in spawning Hurricane Katrina and other devastating storms during the 2004 and 2005 hurricane seasons. If global warming is involved, this drought may only be an early indication of a new weather regime in the Amazon Valley, which holds nearly a quarter of the world's freshwater (Giles, 2006, 726). The Amazon Valley could be caught in a double vise as the world warms, as rising Atlantic Ocean temperatures combine with El Nino events to provoke more frequent droughts. El Nino events tend to reverse the air circulation over the Amazon from east-west to west-east, setting up drying, downslope winds.

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