WASHINGTONA new study has revealed widespread reductions in the greenness of Amazon forests caused by the last year's record-breaking drought.
"The greenness levels of Amazonian vegetation -- a measure of its health -- decreased dramatically over an area more than three and one-half times the size of Texas and did not recover to normal levels, even after the drought ended in late October 2010," says Liang Xu of Boston University and the study's lead author.
The drought sensitivity of Amazon rainforests is a subject of intense study. Computer models predict that in a changing climate with warmer temperatures and altered rainfall patterns, the ensuing moisture stress could cause some of the rainforests to be replaced by grasslands or woody savannas. This would release the carbon stored in the rotting wood into the atmosphere, and could accelerate global warming. The United Nations' Intergovernmental Panel on Climate Change has warned similar droughts could be more frequent in the Amazon region in the future.
The comprehensive study was prepared by an international team of scientists using more than a decade's worth of satellite data from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) and Tropical Rainfall Measuring Mission (TRMM).
Analysis of these data produced detailed maps of vegetation greenness declines from the 2010 drought. The study has been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.
The authors first developed maps of drought-affected areas using thresholds of below-average rainfall as a guide. Next, they identified affected vegetation using two different greenness indexes as surrogates for green leaf area and physiological functioning.
The maps show the 2010 drought reduced the greenness of approximately 2.5 million square kilometers (965,000 square miles) of vegetation in the Amazon -- more than four times the area affe
|Contact: AGU: Peter Weiss |
American Geophysical Union