Amazonian drought conditions add carbon dioxide to the atmosphere

This article originally appeared on the University of Colorado Boulder website.

As climates change, the lush tropical ecosystems of the Amazon Basin may release more of the greenhouse gas carbon dioxide into the atmosphere than they absorb, according to a new study published Feb. 6 in Nature.

Amazon "footprint"An international team of scientists found that the amount of yearly rainfall was the driving factor behind the amount of carbon dioxide (CO2) taken up and released from Amazonia in 2010 and 2011. During a wet year, the Amazon forests were roughly carbon-neutral: Forests “inhaled” more carbon dioxide than they “exhaled,” but biomass burning, which releases carbon dioxide, compensated for the difference. In contrast, during a very dry year forest growth stalled and biomass burning increased, resulting in the region “exhaling” substantial amounts of carbon dioxide to the atmosphere.

“Amazonia is changing: We are observing more very wet years and more very dry years,” said John Miller, one of three lead authors on the new paper, and a scientist with NOAA’s Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder.
NOAA is the National Oceanic and Atmospheric Administration.

“If these trends continue, the region may become a net source of carbon to the atmosphere, moving carbon embedded in ecosystems into the atmosphere as greenhouse gas, thus accelerating global warming.”

Until now, scientists have struggled to measure the carbon balance of Amazonia, which stores enormous amounts of carbon in its thick forests and masses of leaves. Scientists have been eager to understand how climate change could influence the regional balance of processes that send carbon dioxide into the atmosphere (fires, decomposition, respiration) and pull it out of the air (photosynthesis). Global observations cannot sense the “breath” of tropical continental regions, and ground studies cannot sample the vast Amazon Basin.

The scientists led by the three co-lead authors of the study – Miller, Emanuel Gloor from the University of Leeds in England, and Luciana Gatti from the Instituto de Pesquisas Energeticas e Nucleares in Sao Paulo, Brazil – used aircraft to collect air samples between the surface and 14,500 feet (4.4 kilometers) above four sites across Amazonia, every other week for two years. They then analyzed this air with high-precision carbon dioxide and carbon monoxide sensors. Carbon monoxide also is a product of biomass burning.

Read the entire article here.

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