Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: FRIDAY, March 16, 1990 TAG: 9003162316
SECTION: NATIONAL/INTERNATIONAL PAGE: A-3 EDITION: STATE
SOURCE: Associated Press
DATELINE: WASHINGTON LENGTH: Medium
"You will never be able to regenerate the forests once you have cut them," said Jagadish Shukla, a professor of meteorology at the University of Maryland, College Park.
In a paper in Friday's edition of the journal Science, Shukla said a computer model of the effects of deforestation along the Amazon River shows rainfall would decline by more than 26 percent, the average area temperature would rise and evaporated moisture in the Amazon basin atmosphere would decline by 30 percent.
He said clearing the forest affects the regional climate in three ways: Removing the trees causes sunlight to heat up the soil surface; loss of the trees significantly lowers the rate at which water is evaporated into the atmosphere; and loss of the trees disrupts the wind patterns that carry moist air over South America from the oceans.
Loss of the trees would not turn the area into a desert, Shukla noted.
The Amazon basin gets about 97 inches of rainfall a year. Killing the tropical forest, he said, would reduce the annual rainfall by about 25 inches. Once this new, drier pattern is established, the loss of the Amazon basin forest would be irreversible, Shukla said.
The Amazon River dumps huge amounts of fresh water into the Atlantic Ocean, which affects the delicate distribution of heat in the ocean and in the atmosphere.
By reducing the amount of rainfall over the Amazon Basin, Shukla said, the amount of water carried to the Atlantic also would be reduced.
About 14,000 square miles of the Amazon rain forest is cleared annually, and about 12 percent of the forest is gone. Most of the clearing is by slash-and-burn farmers who replace the trees with crops and pasture.
"If deforestation were to continue at this rate, most of the Amazonian tropical forests would disappear in 50 to 100 years," Shukla says in his study.
He said there weren't enough weather records in the area to determine if the climate has already been changed by the 12 percent of the trees that have been removed. However, studies have shown that soil temperatures increased in the cleared areas and that forest fires are more intense in periods of reduced rainfall.
The study was co-authored by Carlos Nobre and Piers Sellers, also of the University of Maryland, College Park.
"What is the critical size beyond which the climate changes and we can't recover the forest? We simply don't know," Shukla said.
by CNB