From sky sensors to forest floors.

• Author: Hardman, Chris
• Position: Deforestation

For more than twenty years, Brazil's Space Research Institute has documented the rate of deforestation in the Brazilian Amazon by analyzing satellite images, but due to technological limitations, scientists have only been able to guess at how much logging occurs in the rain forest. Now, with new technology created at the Carnegie Institution's Department of Global Ecology in Palo Alto, California, remote sensors are generating high-resolution satellite images that track logging activity in Brazil.

"The Amazon is so big that people don't know [what is going on]," explains Professor Greg Asner, the lead scientist on the project. "It's every logger for himself, and so no one has understood how it adds up across the region." The Carnegie Landsat Analysis System (CLAS) does what other satellite techniques cannot: It sees through the dense upper layers of the forest canopy down to the forest floor below.

Selective logging is different from deforestation, which involves clear cutting the forest in total and converting the land to farms or pastures. Selective logging removes only a few trees at a time, because loggers chop down the most commercially valuable trees and leave the rest. The result is a thinning of the forest that can't easily be detected by traditional satellite imagery. With the new Carnegie system, logging can be tracked by satellite photos that capture the "skid trail" etched onto the forest floor as the loggers drag felled trees to their trucks for transport. Using remote sensing data generated from 1999 to 2002, Asner and his colleagues determined that the amount of logging in the Amazon varied from 4,685 square miles to 7,973 square miles per year. "With the new Carnegie system, we can now see what's happening from the top of the forest all the way to the soil," says Asner's colleague Natalino Silva, of the Brazilian Agricnltural Research Corporation. "We have a whole new picture of the Amazon region and selective logging."

Brazilian authorities and agencies creating...