The researchers detected the selective logging, and then quantified the gaps in harvested forests, which covered 17,760 square miles, (46,000 sq km) across four Brazilian states. They tracked those logged forests over time, and found that the probability that logged areas will be clear-cut is highly dependent on their distance from major roads. Most of the selective logging is concentrated within 3 miles (5 km) of major roads. While there was no cause and effect relationship between selective logging and clear-cutting for forests within 3 miles of roads, between 3 and 15.5 miles (5-25 km) from roads there was a clear relationship: selective logging blazes the trail for deforestation. Areas with selective logging at these distances are 2 to 4 times more likely to be cleared than intact forests.

"The link between selective logging and clear-cutting is a one-two punch. Once a forest is selectively logged, it is likely on the path to destruction," said Asner. The researchers were surprised by such a tight relationship between the two land-use activities because different groups are involved--loggers versus ranchers and farmers--and those actors are treated differently by government regulators.

The remote sensing system has a spatial resolution of 98 feet by 98 feet. Through advanced computational methods, the scientists can determine the level of canopy damage and how long it takes to grow back, which they use to understand the severity and duration of ecological disruption. Foliage cover regulates such processes as the rate of photosynthesis, water balance, plant and animal population dynamics, and most critically, the probability of drought and fire.

The research depended on state-of-the-art digital deforestation maps provided by INPE for comparing deforested areas to logged forest. "The Brazilian PRODES program, a global gold-standard for deforestation monitoring, made our comparison possible," explained co-author Micha
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Contact: Greg Asner
gasner@globalecology.stanford.edu
650-380-2828
Carnegie Institution
31-Jul-2006