A deforested portion of the Amazonian rain forest, seen here in April 2005 in the Anapu region, 600 km from Belem in the northern Brazil. Stealthy selective logging under the dense canopy of Brazil's Amazon rainforest has eft twice the amount of the fragile forest degraded by human activities as previously estimated, a US study said. (AFP/File/Antonio Scorza)
WASHINGTON (AFP) - Stealthy selective logging under the dense canopy of Brazil's Amazon rainforest has left twice the amount of the fragile forest degraded by human activities as previously estimated, a US study said.
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The worse-than-expected degradation of the Amazon, known as "the lungs of the world" for its ability to absorb greenhouse gases, means that more carbon is being released into the atmosphere than previously thought, the researchers said in an article in the October 21 edition of the journal Science.
Based on a new, high-resolution satellite data analysis, a team of researchers led by Gregory Asner of Carnegie Institution's Department of Global Ecology in Stanford, California said they found that "forest degradation in the Brazilian Amazon has been underestimated by half."
The Carnegie scientists developed the Carnegie Landsat Analysis System to measure satellite observations conducted between 1999 and 2002 and compare them with on-ground field studies.
"We discovered that annually an area about the size of Connecticut is disturbed this way. Selective logging negatively impacts many plants and animals and increases erosion and fires," Asner said in a Carnegie Institution statement that accompanied the article.
"Additionally, up to 25 percent more carbon dioxide is released to the atmosphere each year, above that from deforestation, from the decomposition of what the loggers leave behind. Timber harvests are much more widespread than previously thought."
Selective logging, in which people log trees one-by-one rather than clear cutting, has reduced annually the wooded surfaces of the Brazilian Amazon by between 4,685 square miles (12,135 square kilometers) and 7,973 square miles (20,651 square kilometers), the scientists said.
For several decades selective cutting of at least 35 varieties of high-value trees, such as mahogany, has been done under cover of the dense forest canopy, which made satellite observations difficult.
New optical technologies have allowed the satellites to penetrate the canopy and obtain very detailed images, the scientists said.
Nearly a third of the world's land creatures, from insects to jaguars, live in the Amazon forest. But studies show their numbers have been declining since the late 1970s after fires were deliberately set to clear the land for other uses, such as agriculture.
Seventeen percent of the Brazilian Amazon has been razed.
