Drought-stricken regions of the Amazon forest grew particularly vigorously during the 2005 drought, according to new research.

The counterintuitive finding contradicts a prominent global climate model that predicts the Amazon forest would begin to “brown down” after just a month of drought and eventually collapse as the drought progressed.

“Instead of ‘hunkering down’ during a drought as you might expect, the forest responded positively to drought, at least in the short term,” said study author Scott R. Saleska of The University of Arizona. “It’s a very interesting and surprising response.”

UA co-author Kamel Didan added, “The forest showed signs of being more productive. That’s the big news.”

The 2005 drought reached its peak at the start of the Amazon’s annual dry season, from July through September. Although the double whammy of the parched conditions might be expected to slow growth of the forest’s leafy canopy, for many of the areas hit by drought, the canopy of the undisturbed forest became significantly greener—indicating increased photosynthetic activity.

Saleska, a UA assistant professor of ecology and evolutionary biology, and his colleagues at the UA and at the University of São Paulo in Brazil used data from two NASA satellites to figure out that undisturbed Amazon forest flourished as rainfall levels plummeted.

“No one had looked at the observations that are available from satellites,” said Didan, an associate research scientist in the UA’s department of soil, water and environmental science. “We took the opportunity of the most recent drought, the 2005 drought, to do so.”

“A big chunk of the Amazon forest, the southwest region where the drought was severest, reacted positively,” said Didan, a NASA-EOS MODIS associate science team member.
http://www.eurekalert.org/pub_releases/2007-09/uoa-afs092107.php