Deep in the Amazon Forest, Vast Questions About Global Climate Change

By LARRY ROHTER
Published: November 4, 2003

APAJ�S NATIONAL FOREST, Brazil - Viewed from the top of a tower 150 feet over an exuberant canopy of green, the vast Amazon jungle appears to be a neatly functioning organism. Trees in immeasurable numbers stretch away to the horizon here, their leaves open to the sun, eager to feed on the light that streams down from the sky and perforates the stifling tropical heat.

Down on the ground, however, the longstanding debate about the Amazon's role in global climate change is intensifying. The Amazon is the largest tropical forest in the world - bigger than all of Europe, with Brazil's section alone more than half the size of the continental United States. And it has always been assumed to be essential to inhibiting global warming by drawing in carbon dioxide during photosynthesis.

Carbon dioxide is one of the main gases that contribute to global warming and the much-dreaded greenhouse effect. But it has never been established whether the rain forest here is in fact functioning as a giant sink that "sequesters," or traps and absorbs, carbon.

Some scientists have suggested that indiscriminate deforestation has turned the Amazon into a net source of such gases, spewing huge amounts of carbon dioxide into the air.

Scientists have been investigating that question for a decade now, and the answer is sure to have important political and scientific ramifications both for Brazil and the rest of the world.

If in fact the Amazon is a net source of carbon gas emissions, or if the amounts of gas emitted and sequestered are in a rough permanent equilibrium, some of the fundamental assumptions of the 1998 Kyoto Protocol on climate change may have to be reconsidered. No one knows precisely the amount of greenhouse gases that Brazil is already pumping into the atmosphere. A national inventory of carbon emissions, due to have been announced four years ago, has still not been made public. And although the new left-wing government that took power in Bras�lia early this year was elected with the support of environmentalists, it has given no indication when it intends to publish those figures.

Scientists at the National Institute for Amazon Research in Manaus estimate that carbon emissions in Brazil may have risen by as much as 50 percent since 1990. By their calculations, what is euphemistically called "land use changes" now produce annual emissions of 400 million tons of greenhouse gases, dwarfing the 90 million tons generated annually by fossil fuel use in Brazil and making this country one of the 10 leading emitters of greenhouse gases in the world.

All across the Brazilian Amazon, the jungle is being razed for cattle pasture, crops, logging, highways and human settlements at an increasingly faster rate, contributing to fears that the climate balance here may soon be permanently tipped. Last year alone, the land that was deforested rose by 40 percent over 2001, to nearly 10,000 square miles, an area larger than New Jersey.

Brazilian scientists, in conjunction with American and European colleagues, are engaged in what is known as the "Large-Scale Bio-Atmosphere Experiment in the Amazon," or L.B.A. The goal is to resolve uncertainties about carbon emissions. Begun in the mid-1990's, the program gathers data at 15 sites, including two in this national forest about 50 miles south of the confluence of the Tapaj�s River and the Amazon.

At each location, a tower 195 feet high measures the jungle's emissions of carbon dioxide and other gases and also collects readings of wind velocity and direction. To get a picture as broad and accurate as possible, some measuring posts have been placed on flat land, some in sloping areas, others in virgin forest and others still in "disturbed forest," where logging has occurred and secondary growth is present.

"Right now we cannot provide a definitive answer to the question of whether the Amazon is source or sink," Dr. Flavio Luiz�o, president of the International Scientific Committee of the L.B.A., said in an interview in Manaus. "But in another three or four years, I think we will be able to reach a consensus."

To be cont'd