Aug. 9 (Bloomberg) -- Peru slowed the destruction of its rainforests by designating areas for legal logging and setting aside the rest for conservation, according to scientists who tracked developments through a satellite imaging system.

Peru designated 31 percent of its 255,000 square miles of rainforest as a protected area in 2001, and by 2005 had set aside about 16 percent of the total for long-term commercial timber production. Rainforest destruction was greater in neighboring Brazil, which lacked a national forest concession plan until last year, said Gregory Asner, the Stanford University scientist who led the study.

Environmentalists are looking to preserve the world's forests to combat global warming caused by the emission of carbon dioxide, which is consumed by forests. About 150,000 square kilometers (57,915 square miles) are destroyed every year by logging, ranching and other commercial activities, according to the Web site of The Rainforest Foundation, a London-based nonprofit.

``In Peru, we found that conservation lands successfully protect against deforestation,'' Asner said in an e-mailed statement. ``In Brazil, without forest concessions, there was no way to tell which parts of the forest were designated for timber extraction, which were designated for conservation, and in what areas timber extraction would be legal or illegal.''

The study, published today in the online edition of Science Express, found that clear-cutting rates in Peru averaged only 244 square miles a year between 1999 and 2005.

Researchers also found that in Peru, timber harvesters sometimes ventured illegally into protected territory, especially sections that border the concession areas, Asner said.

``This is what I call `leaky operations,''' he said. ``This is cause for concern.''

The satellite used an advanced signal processing system that Asner started developing as a graduate student, he said. The technology is sensitive enough to track both clear-cutting and selective logging, where loggers cut down one or two trees in a given area and leave the rest intact.