An extensive drought in the Amazon rain forest last year spurred massive carbon dioxide emissions, British and Brazilian scientists said Thursday. They fear the devastating event may become a common occurrence, turning the world’s largest rain forest from an absorber of heat-trapping gases into a source of the harmful emissions.
Simon Lewis, an ecologist at the University of Leeds, and his team of researchers said in a study published Thursday that 2010′s crippling dry spell was worse than a “once-in-a-century” 2005 drought and may have caused more emissions than the United States does in a year.
Forests abundant in vegetation help diminish carbon dioxide in the atmosphere by soaking it up as they grow, but they release the heat-trapping gas when they die and biodegrade.
The 2010 drought was severe enough to leave major Amazonian rivers dry, stranding thousands who depend on boat transport. It followed the region’s dry spell in 2005, a drought so severe that scientists had dubbed it a “once-in-a-century” event at the time.
But last year’s drought was even more intense than the one five years before, scientists discovered. It caused rainfall shortages that affected a 1.16 million square-mile expanse of the Amazon, compared with the 734,000 square miles exposed to drought in 2005.
The 2010 dry spell also caused higher tree mortality and had three major epicenters, as opposed to the 2005 drought, which was mainly concentrated in one area in the southwestern Amazon.
The Amazon typically soaks up around 1.5 billion metric tons of carbon per year. According to the study, the forest will release 5 billion metric tons of greenhouse gases in 2010 and 2011 for a total impact of about 8 billion metric tons. That’s below the United States’ carbon dioxide emissions in 2009, which were approximately 5.4 billion metric tons.
“If events like this happen more often, the Amazon rain forest would reach a point where it shifts from being a valuable carbon sink slowing climate change to a major source of greenhouse gases that could speed it up,” Lewis said.
The study was published in Thursday’s edition of the journal Science.