Several climate models have predicted that rising Earth temperatures will cause intense drought in the Amazon basin, eventually leading to the rainforest's collapse into grass-covered savannah, with only a sprinkling of trees.
Now, a new model that takes into account the widespread drought that hit the Amazon in 2005 has shown otherwise.
According to the model, a warming scenario would result in the forest being hit by drought. The trees would then respond by reducing both transpiration (the evaporation of water from parts of a plant, especially the leaves) and photosynthesis.
This reaction would exacerbate the drought by reducing the amount of water entering the atmosphere, which in turn would reduce precipitation.
Lead author Scott Saleska said these responses should be observable as changes in trees' leaf area and the amount of chlorophyll (both measures of the forest's "greenness") in the forest trees by satellite measurements even for short-term droughts.
She said the researchers found that the greenness of the forest had actually increased during the 2005 drought.
The researchers hypothesize this could be because the trees actually had more access to sunlight and could dig their roots deeper down in the soil to access water.
Saleska said, according to her test results, the Amazon won't be as directly vulnerable to drought as the climate models predict, but that it will still be vulnerable to deforestation and forest fires, which can increase during droughts.
The study appears in the Sept. 21 issue of the journal Science, reports LiveScience.