From: David A Gabel, ENN
Published February 4, 2011 08:58 AM

The Alarming Amazon Droughts of 2005 and 2010

When thinking of the wettest place on land, most people think about rainforests such as the Amazon, which can get up to 78 inches of rain per year. All this precipitation supports the Amazon's rich plant life which helps moderate carbon dioxide levels in the atmosphere. It is then quite alarming to learn that the Amazon has suffered two devastating droughts in the last five years. Researchers fear a continuation of this disturbing trend.

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In 2005, the Amazon went through its worst drought in a century. Soon after, some scientists estimated that the Amazon could not survive three consecutive years of such a drought. Others predicted that the drought, coupled with deforestation's effects on climate, push the Amazon to a tipping point. After which, the rainforest would irreversibly start die and be replaced by a savannah or desert. This would have enormous impacts on global climate.

In 2010, the dry season proved to be even more severe than the one in 2005, which was claimed to be a one-in-100 year event. A team of British and Brazilian researchers found that the carbon impact of the 2010 drought may have caused the release of over 5 billion tons of CO2 (released from dead plant life). By way of comparison, the United States produced 5.4 billion tons of CO2 from fossil fuel burning.

In a normal year, the Amazon absorbs 1.5 billion tons from the atmosphere, moderating the rate of climate change. Scientists predict that a further 5 billion tons will be produced as the trees that were killed by the new drought begin to decompose.

According to Brazilian scientist, Dr. Paulo Brando, "We will not know exactly how many trees were killed until we can complete forest measurements on the ground. It could be that many of the drought susceptible trees were killed off in 2005, which would reduce the number killed last year. On the other hand, the first drought may have weakened a large number of trees so increasing the number dying in the 2010 dry season."

Dr. Simon Lewis of the University of Leeds in the UK stated, "Two unusual and extreme droughts occurring within a decade may largely offset the carbon absorbed by intact Amazon forests during that time. If events like this happen more often, the Amazon rainforest would reach a point where it shifts from being a valuable carbon sink slowing climate change, to a major source of greenhouse gasses that could speed it up. Considerable uncertainty remains surrounding the impacts of climate change on the Amazon. This new research adds to a body of evidence suggesting that severe droughts will become more frequent leading to important consequences for Amazonian forests."

The study was conducted by researchers from the University of Leeds, Sheffield, and the Instituto de Pesquisa Ambiental da Amazonia in Brazil. It was funded by the Royal Society, Gordon and Betty Moore Foundation, and the US National Science Foundation. The study was published in the journal Science.

Link to published article: http://www.sciencemag.org/content/331/6017/554.abstract

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