![]() ![]() They eliminated pixels showing burned or deforested areas to calculate the carbon impact of drought on intact forests alone. The researchers developed a new method of analysis to convert these structural changes into changes in aboveground biomass and carbon. These data reveal changes in canopy structure, including leaf damage and gaps. The research team used high-resolution lidar maps derived from the Geoscience Laser Altimeter System aboard the Ice, Cloud, and land Elevation Satellite (ICESat). To do that, he and his colleagues turned to satellite data. "The detailed measurements in these sites are extremely important for understanding forest function, but we can never use them to say what this giant ecosystem is doing in a timely fashion," Saatchi said. ![]() There are only about hundred plots used for research and a few tower sites for long-term monitoring of the Amazon forests. They die from dehydration and eventually fall to the ground, leaving gaps in the forest canopy far overhead.īut any observer on the ground can monitor only a tiny part of the forest. Without adequate rainfall, these giants can't pump water more than 100 feet up from their roots to their leaves. Observers on the ground also notice that droughts tend to disproportionately kill tall trees first. So the loss of leaves is a strong indication the forest is stressed." Even if trees eventually survive defoliation, this damages their capacity to absorb carbon while under stress. "These are rainforests the trees almost always have leaves. "This is our new paradigm." Drought from the groundįor scientists on the ground in the Amazon, "The first thing we see during a drought is that the trees may lose their leaves," Saatchi said. "The ecosystem has become so vulnerable to these warming and episodic drought events that it can switch from sink to source depending on the severity and the extent," Saatchi said. "The old paradigm was that whatever carbon dioxide we put up in emissions, the Amazon would help absorb a major part of it," said Sassan Saatchi of NASA's JPL, who led the study.īut serious episodes of drought in 2005, 20 are causing researchers to rethink that idea. Scientists estimate that it absorbs as much as one-tenth of human fossil fuel emissions during photosynthesis. But starting with the drought year of 2005 and running through 2008 - the last year of available lidar data - the Amazon basin lost an average of 0.27 petagrams of carbon (270 million metric tons) per year, with no sign of regaining its function as a carbon sink.Īt about 2.3 million square miles (600 million hectares), the Amazon is the largest tropical forest on Earth. In years of normal weather, the undisturbed forest can be a natural carbon "sink," absorbing more carbon dioxide from the atmosphere than it puts back into it. This is the first study to quantify the long-term legacy of an Amazon drought.Ī research team from NASA's Jet Propulsion Laboratory in Pasadena, California, and other institutions used satellite lidar data to map tree damage and mortality caused by a severe drought in 2005. A single season of drought in the Amazon rainforest can reduce the forest's carbon dioxide absorption for years after the rains return, according to a new study published in the journal Nature. ![]()
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