Eintime Conversion for education and research 04-08-2008 @ 12:48:33|
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Scientists puzzle over Amazon's role in warming world
By Michael Astor, Associated Press
MANAUS, Brazil Julio Tota stood atop a 195-foot steel tower in the heart of the Amazon rain forest, watching "rivers of air" flowing over an unbroken green canopy that stretched as far as the eye could see.
These billows of fog showed researcher Tota how greenhouse gases emitted by decaying organic material on the forest floor don't rise straight into the atmosphere, as scientists had supposed.
Instead, they hover and drift confounding scientific efforts to unlock the secrets of the world's largest remaining tropical wilderness.
"What we've learned is, the Amazon rain forest is much more fragile and much more complex than we had first imagined," Tota said. "My research is pretty specific. It's aimed at showing why all our measurements are probably off."
Tota is part of the Large Scale Biosphere-Atmosphere Experiment, a decade-old endeavor involving hundreds of scientists, led by Brazilians and with funding from NASA and the European Union. Their open-air "laboratories" are 15 such observation posts spread over an area of rain forest larger than Europe.
The project's goal is to make the best scientific arguments for why this vast rain forest along with other endangered forests in Africa, southeast Asia and elsewhere is essential to combating global climate change.
But as the first phase of the $100 million experiment draws to a close, its researchers acknowledge that the data have raised more questions than answers.
Scientists can now say with certainty that the Amazon is neither the lungs of the Earth, nor the planet's air conditioner. Paradoxically, the forest's cooling vapors also trap heat, by reflecting it back toward Earth in much the same way greenhouse gases do.
But a key question remains unanswered: Does the Amazon work as a net carbon "sink," absorbing carbon dioxide, or is it adding more CO2 to the atmosphere than it is subtracting, because of burning and other deforestation that have claimed an average 8,000 square miles an area the size of Israel or New Jersey each year of the past decade?
Scientists also can't predict every way in which continued destruction of the Amazon for timber, for cattle ranching, for soybean farming might affect global climate. But it will almost certainly lead to drier conditions over a wide area, since ground moisture taken up and evaporated through trees is recycled as rainfall.
Some computer simulations suggest deforestation could cause droughts as far afield as the U.S. grain belt, apparently because chain reactions in the atmosphere would shift the Polar Jet Stream and the precipitation it brings.
These questions take on new urgency as global warming's effects become ever more apparent, and as forests fall at a non-stop pace. In one sign of growing concern, Brazil's national leadership met in emergency session on Jan. 24 to deal with a sudden surge in deforestation after a three-year slowdown.
New studies suggest the Amazon may be approaching a tipping point, at which the drier conditions caused by deforestation will reduce rainfall enough to transform the humid tropical forest into a giant savanna.
If preserving the 80% of the Amazon still standing would help offset some greenhouse emissions, destroying it would almost certainly accelerate global warming, by releasing perhaps 100 billion tons of carbon into the atmosphere equal to some 10 years' worth of total global emissions.
"If you cut down all the tropical forests in the world you may increase CO2 concentrations by 25%," said Brazilian climatologist Carlos Alberto Nobre. "It's important to keep the forests intact because we are in a global warming crisis and it's important not to reach a tipping point from which we can't come back."
Deforestation both the burning and rotting of wood in the Amazon already releases an estimated 400 million tons of carbon dioxide into the atmosphere every year, accounting for up to 80% of Brazil's greenhouse gases, boosting this country to sixth place or higher among emitter nations.
By contrast, each acre of rain forest that remains intact takes somewhere between 80 and 480 pounds of carbon out of the atmosphere each year through the process of photosynthesis.
The uncertainty in that range hints at the unknowns still puzzling researchers. In the next phase of the grand Amazon experiment, two airplanes will measure emissions higher in the atmosphere, to try to answer definitively whether the rain forest absorbs more carbon than it produces.
Viewed from above, the Amazon appears to be an almost uniform carpet of green, spreading over 2.7 million square miles and nine countries. But in truth it's home to a wide range of ecological systems and micro-climates.
That's why Biosphere-Atmosphere Experiment specialists are helping design development models for each region, from managed logging to fruit farming to the low-intensity harvesting of forest products such as rubber, cocoa, fruits and ingredients for cosmetics and pharmaceuticals.
"We're looking at what all this means for the prospect of sustainability of the Amazon and how we can best inform decision-makers about sustained productivity and land use," Diane Wickland, who manages NASA's Terrestrial Ecology Program, said from Washington.
The experiment has already yielded troubling conclusions, Wickland said. Refined satellite surveillance, for example, finds that selective logging affects about as much area as clear-cutting, adding significantly to carbon dioxide emissions and casting doubt on whether managed forestry can save the Amazon.
Brazilian physicist Paulo Artaxo, a veteran Amazon researcher, said it's essential that Brazil, home to almost 70% of the rain forest, sharply slow the destruction of its woodlands. "There is no cheaper way to reduce emissions than by controlling deforestation," he said.
Scientists estimate it would cost about $1 billion a year in lost income for Brazil to end the clearing of forest by loggers, ranchers and farmers, largely giant soybean-growing conglomerates.
At the Bali conference, the world's nations decided to explore possible plans for compensating rain-forest nations for rolling back their rates of deforestation.
That money could come as "carbon credits," in the trading system under the Kyoto Protocol climate pact whereby industrial nations that overshoot their greenhouse emissions quotas can get credit for emissions reductions at power plants or other projects in the developing world. By awarding credits to rain-forest states, richer nations would now also be financing protection of carbon sinks.
The negotiations over such a complex global plan promise to be long and difficult.
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