TULANE (US)—A single, violent storm that swept across the Amazon forest in 2005 killed half a billion trees, far more than previously suspected, according to the first study to produce an actual body count of the losses.

Amazon rainforests, which are thought to absorb a significant portion of carbon dioxide from the earth’s atmosphere, are an important bellwether for climate change researchers.

Tree loss in the Amazon is considered one of a number of potential “tipping points” related to issues of rapid climate change.

Previous research had attributed a peak in tree mortality in 2005 solely to a severe drought that affected parts of the forest.

The new study says that a single squall line of severe thunderstorms in January 2005 had an important role in the tree demise.

This type of storm might become more frequent in the future in the Amazon due to climate change, killing a higher number of trees and releasing more carbon to the atmosphere, according to the paper’s authors, Jeffrey Chambers, a forest ecologist at Tulane University and atmospheric scientist Robinson Negrón-Juárez.

The study is available online in the journal Geophysical Research Letters.

Researchers used a combination of satellite images, field-measured tree mortality, and modeling to determine the number of trees killed by the storm.

By linking satellite data to field observations, the researchers were able to take into account smaller tree blowdowns (down to 7-10 trees per event) that otherwise cannot be detected through satellite images.

Between 441 and 663 million trees were destroyed by the storms, representing a loss equivalent to 23 percent of the estimated mean annual carbon accumulation of the Amazon forest.

Previous studies on tree mortality in the Amazon have diligently collected dead-tree tolls, Chambers says, but information on exactly what killed the trees is often lacking, or not reported at all.

“It’s very important that when we collect data in the field we do forensics on tree mortality,” he says.

“Under a changing climate, some forecasts say that storms will increase in intensity. If we start seeing increases in tree mortality, we need to be able to say what’s killing the trees.”

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