(May 9, 2011) The Amazon Forest – often called the lungs of the Earth – suffered a large drought in 2005 and an even larger one in 2010, devastating populations of river dolphins and other species and leading many climate scientists to fear the worst. “Having two events of this magnitude in such close succession is extremely unusual, but is unfortunately consistent with those climate models that project a grim future for Amazonia,” said Simon Lewis, from the University of Leeds, co-author of “The 2010 Amazon Drought,” a paper published in Science in February of this year.
Today, just three months after that dire outlook, the doom and gloom is lifting. The Amazon and its species have made a dramatic comeback, so much so that the river populations of dolphins now exceed pre-dought levels, even in one of the hardest hit drought areas.
A major concern involves the ability of the Amazon’s old-growth forest to survive the stress of low water levels. Will trees recover from the extreme shock of the drought, and continue to grow, or will the die off, releasing their great stores of carbon dioxide to the atmosphere, as many fear?
The answer may lie partly in a 2009 study of the 2005 drought conducted by 66 scientists at Leeds that found the Amazon’s trees, even at an advanced age, to be vigorous in growth and resilient to drought. What could possibly explain these twin capabilities?
The unusually rich concentration of carbon dioxide in the atmosphere, say scientists who have studied the Amazon for decades. Carbon dioxide reduces the rate at which trees respire, letting them survive low water conditions. And carbon dioxide provides the carbon that trees need to take in and grow.
As put by Oliver Phillips in The changing Amazon forest, published by the Royal Society, “While there have been widespread changes in the physical, chemical and biological environment of tropical trees, the only change for which there is unambiguous evidence that the driver has widely changed and that such a change should accelerate forest growth is the increase in atmospheric CO2. The undisputed long-term increase in concentrations, the key role of CO2 in photosynthesis, and the demonstrated effects of CO2 fertilization on plant growth rates make this the primary candidate.”
The short version: It’s CO2 to the rescue. The more of it in the atmosphere, the better the Amazon’s chance of survival.