Nature & Environment

Amazon Forest Draws in More Carbon Dioxide than it Emits, NASA Claims

Benita Matilda
First Posted: Mar 19, 2014 07:03 AM EDT

A seven-year study led NASA reveals that the forests in the Amazon absorb more carbon dioxide from the atmosphere than the amount they emit, in turn lowering the rate of global warming.

The new study by the space agency is an attempt to end the long-standing debate about the key component of the complete carbon balance of the Amazon basin, home to the most developed and largest rainforest in the world. The researchers found that the living tress in the Amazon suck in more carbon dioxide from the air as they grow compared to the greenhouse gas that is returned into the atmosphere by the decomposing dead trees.

This is one of the first studies to measure tree deaths that occur due to natural processes in the Amazon forest and also the remote regions where till date no data has been gathered.

The finding was made using new techniques developed by the team led by Fernando Espírito-Santo of NASA's Jet Propulsion Laboratory, Pasadena, Calif.. Using these novel techniques they analyzed satellite and other data. It was during the analysis that the team realized that the dead Amazonian trees emit nearly 1.9 billion tons of the greenhouse gas into the atmosphere.

This was compared with the amount of carbon dioxide taken in by the Amazonian trees, for this they used the censuses of forest growth and also various modeling scenarios linked with uncertainties.  They noticed that the absorption of carbon by the living trees outweighed the emission of carbon dioxide by the dead trees, hinting that the prevailing effect in the Amazon is absorption.

Till date the estimates of the carbon balance in Amazon were made with limited observations in small forest regions called plots.  The idea for the research on carbon balance came up  in the year 2006. Since then the team worked with five nations to measure the impact of carbon on tree deaths in the Amazon.  They used satellite images, airborne lidar data and 10-year sets of plot measurement.

By correlating the satellite data and airborne instrument data with ground observations they came up with a technique to spot dead trees in various types of remotely sensed images.

"We found that large natural disturbances -- the sort not captured by plots -- have only a tiny effect on carbon cycling throughout the Amazon," said Sassan Saatchi of JPL, also a co-author.

They found that every year two percent of the Amazon forest dies of natural causes and they also identified that 0.1 percent of the deaths are due to blowdowns.

The study was published in the Nature Communications.

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