Context:

• A single season of drought in the Amazon rainforest can reduce its capacity to absorb carbon dioxide for years after the rains return, a NASA study has found.

NASA’s Jet Propulsion Laboratory:

• Researchers from NASA’s Jet Propulsion Laboratory (JPL) in the US, and other institutions used satellite data to map tree damage and mortality caused by a severe drought in 2005. 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.
• However, starting with the drought year of 2005 and running through 2008 — the last year of available data — the Amazon basin lost an average of 270 million metric tonnes per year of carbon, with no sign of regaining its function as a carbon sink. Scientists estimate that it absorbs as much as one-tenth of human fossil fuel emissions during photosynthesis.

Vulnerable ecosystem:

• “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,” said Sassan Saatchi of JPL, who led the study.

ICESat:

• The research team used high-resolution maps derived from the Geoscience Laser Altimeter System aboard the Ice, Cloud, and land Elevation Satellite (ICESat). These data reveal changes in canopy structure, including leaf damage and gaps. The researchers found that following drought, fallen trees, defoliation and canopy damage produced a significant loss in canopy height. 

Source:TH