Professor uses satellites to protect Amazon forests, global climate

December 05, 2003

The Amazon is the world's largest rain forest and home to an untold number of species and natural resources. It also provides a vital means for removing an important greenhouse gas from the atmosphere. All of this is in danger, as the Amazon is rapidly shrinking.

Greg Asner, a faculty scientist with the Carnegie Institution at Stanford, is working with a multinational team to reverse this trend. Using both high-tech and low-tech tools, the researchers hope to safeguard the Amazon from one of its biggest threats - rampant logging by small operators who essentially poach timber. In Brazil, for example, loggers often take patches of trees without first obtaining permits from that country's environmental protection agency. While the practice, known as selective logging, may be sustainable, it has dire consequences. Asner will present his team's findings Dec. 10 and 11 at this year's San Francisco meeting of the American Geophysical Union, an international scientific society with more than 35,000 members dedicated to advancing the understanding of the Earth and its environment.

"[Selective logging] acts like a net - when you take down one tree, you end up taking five to 20 other trees around it," as the trees are often intertwined or connected by vines, said Asner, an assistant professor, by courtesy, in the Stanford Department of Geological and Environmental Sciences. Only a small portion of this felled wood becomes harvested timber; the rest turns to waste. Selective logging dominates current landscape use in Brazil and is also among the biggest threats to the global environment.

At the same time, people involved in the timbering process - clearing land and removing wood with tractors - further denude the landscape. That landscape of destruction attracts ranchers and farmers, who move into the newly opened space and frequently expand it, thereby accelerating the rate of deforestation. By burning forest to clear it, they release carbon into the atmosphere. These activities slow reforestation.

"For the first time, all of this is being observed by satellite," said Asner. He and his team - including a Brazilian nongovernmental organization, Brazil's environmental protection agency, NASA and the U.S. Forest Service - have spent five years developing a remote-sensing system for measuring timber harvests and deforestation. Satellite images focus on biophysical and biochemical changes in the forest canopy and provide a broad picture of how the Amazon is being thinned. The information is then shared with the environmental protection agency to help it better target illegal loggers. ''It provides extraordinary detail of the thinning of the Amazon basin,'' Asner said.

Asner and his team are working against time as the rate of the Amazon rain forest's disappearance quickens. Annually, roughly 15,000 square kilometers of forest are lost to clear cutting and cattle pasturing alone - an amount of territory the size of the state of Massachusetts. Another 7,000 to 15,000 square kilometers is lost to timber harvesting, resulting in up to 30,000 square kilometers of forest degradation each year. "This is much larger than previously thought," says Asner.

Forest isn't the only thing that's lost. The region's vast warehouse of natural resources is being stripped before it has been fully audited. So far, scientists estimate its trees and other plants provide between 20 to 50 percent of the world's oxygen as well as ingredients vital to the manufacture of medicine and other products. The Amazon is also home to almost one-third of the world's species. All of this is in danger, and in ways that could have global ramifications, Asner said.

Already, selective logging has substantially impeded the ability of forests to remove carbon dioxide from the atmosphere. The Amazon acts as a giant carbon sink, drawing carbon dioxide, required by plants for life, out of the atmosphere and into the forest. The biomass in the forest then absorbs and stores it, keeping a portion of global-warming gases out of the atmosphere. With the loss of the forest, this process is severely diminished.

Despite the best efforts of Asner and his team to detail the thinning of the forests, all of this likely will increase in the near future due to high timber demand and shrinking global supply. The world's other large source of tropical woods in Southeast Asia already has been largely depleted.

''It's an alarming process,'' Asner said. ''Deforestation and selective logging have an impact on the [Amazon's] regional climate systems. Other scientists are showing that rainfall has decreased in areas of heavy deforestation. And, overall, it's not entirely understood what the impact of logging and deforestation will be for the global climate system.''
This release was written by Hugh Biggar, a Stanford journalism graduate student. A photo of Asner is available at .

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Stanford Report (university newspaper):

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CONTACT: Dawn Levy, News Service: 650-725-1944,

COMMENT: Greg Asner, Geological and Environmental Sciences: 650-325-1521, ext. 245,

EDITORS: The American Geophysical Union will hold its annual fall meeting Dec. 8 to 12 at the Moscone Convention Center, 747 Howard St., San Francisco, CA 94103. Greg Asner will present his findings Wednesday, Dec. 10, and moderate discussions on Dec. 10 and Dec. 11, beginning both days at 8 a.m. PST in Moscone West, Room 3014. His co-convener will be Dr. Ruth Defries of the University of Maryland.

Relevant Web URLs:

Stanford University

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