At left, the extent of the 2005 drought in the western Amazon rainforests during the summer as measured by NASA satellites. The worst affected areas are in red and yellow. The circled area in the right panel shows the extent of the forests that experienced slow recovery from the 2005 drought. Image credit: NASA/JPL-Caltech/GSFC
An area of the Amazon rainforest three times the size of the United kingdom was strongly affected by a drought that began in 2005, says a NASA-led team that includes researchers from Oxford. The results, together with observed increases in rainfall variability and associated forest damage in southern and western Amazonia during the past decade, suggest these rainforests may be witnessing the first signs of potential large-scale degradation due to climate change. The researchers analysed more than a decade of satellite microwave radar data collected between 2000 and 2009 over Amazonia. The observations included measurements of rainfall from NASA's Tropical Rainfall Measuring Mission as well as the moisture content and volume, or biomass, of the forests. The scientists found that, beginning in 2005, more than 270,000 square miles (70 million hectares or three times the area of the UK) of pristine, old-growth forest in southwestern Amazonia experienced an extensive and severe drought. This drought caused widespread changes to the forest canopy that were detectable by satellite. These changes to the canopy suggest dieback of branches and tree falls, especially among the older, larger, more vulnerable 'canopy' trees that blanket the forest, say the researchers in a paper published in the journal Proceedings of the National Academy of Sciences .
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