Red and orange identify areas where satellite measurements indicated reduced greenness of the Amazon forest during the 2010 drought. (Green patches are areas of enhanced greenness.) The maps differ only in the method used for determining vegetation greenness from optical data. Click to enlarge.
A new study on its way to being published shows that the Amazon rainforest suffered greatly from last year's drought. Employing satellite data and supercomputing technology, researchers have found that the Amazon was likely hit harder by last year's drought than a recent severe drought from 2005. The droughts have supported predictions by the Intergovernmental Panel on Climate Change's (IPCC) that climate change, among other impacts, could push portions of the Amazon to grasslands, devastating the world's greatest rainforest.
"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," explains the study's lead author Liang Xu of Boston University.
According to the study, which will be published in Geophysical Research Letters, nearly a million square miles (2.5 million square kilometers) saw reduced greenness in 2010. This is more than four times the area impacted by the 2005.
According to Arindam Samanta, a co-lead author from Atmospheric and Environmental Research in Lexington, Massachusetts, satellite data taken from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS)] "suggest a more widespread, severe and long-lasting impact to Amazonian vegetation than what can be inferred based solely on rainfall data."
Samanta also studied the 2005 drought, including working on a paper that found little greenness difference in the Amazon between 2005 and non-drought years. However, the level of greenness is not the only line of evidence researchers look to in order to determine the impact of a drought. Other evidence includes tree mortality and the outbreak of fires in the rainforest.
While the prediction that around 40% of the Amazon could flip to grasslands due to climate change has faced criticism from climate skeptics—and become a part of the histrionic and rarely fact-based political fight over greenhouse gas emissions—the science behind the theory has remained strong.
"The main conclusion of the IPCC statement—that Amazonian forests are very susceptible to reductions in rainfall—remains our best understanding of the data available at the time of the IPCC report and also today," reads a letter from some of the world's most well-respected Amazon experts that attempted to clarify misinformation on the issue last year.
Around the same time, Thomas Lovejoy, biodiversity chair at the Washington DC-based Heinz Center for Science, Economics and the Environment, and chief biodiversity adviser to the president of the World Bank, pointed out that the Amazon rainforest did not exist in a laboratory, but faced multiple pressures on top of climate change. Citing a World Bank report that looks at the synergistic effects of deforestation, climate change, and fires, Lovejoy said that the "tipping point for the Amazon is 20 percent deforestation". Currently 17-18 percent of the Amazon has been lost, leading Lovejoy to tell Tierramerica that the Amazon rainforest was "very close to a tipping point".
Both the letter and Lovejoy's statements came prior to the 2010 drought.