Satellites spy
DB: This is Earth and Sky, on using satellites to detect logging in the Amazon rain forest – previously hidden to scientists.
JB: Gregory Asner is a remote sensing expert at the Carnegie Institution of Washington. He said satellites used to lack the precision to see where people cut valuable individual trees – such as mahogany. Asner’s team found a way to refine the satellite images. Their images show that, each year in the rainforest, an area the size of Connecticut was being selectively logged.
Gregory Asner: And what it essentially tells us is that the area of disturbance in the Amazon is double now what we thought it was prior to our study.
DB: That disturbance can take the form of other trees pulled down by those selectively logged. There are also roads built to reach the trees. And selective logging lets more light reach the forest floor, drying out the understory and creating fuel for fire.
Gregory Asner: So when people ask, is selective logging as large a form of damage as deforestation, the answer is no, initially, not nearly the same level of damage. But over the long run, the fact that fire is introduced to a place that really hasn’t had fire, historically, is a cause of great concern to the scientists that work there.
_JB: More about the human footprint in Amazon rainforests at earthsky.org. Thanks today to NASA explore, discover, understand. We’re Block and Byrd for Earth and Sky.
Read Earth & Sky’s interview with Greg Asner.
Additional Teacher Resources
NASA: Small-Scale Logging Leads to Clear-Cutting in Brazilian Amazon
A NASA-funded study has discovered an important indicator of rain forest vulnerability to clear-cutting in Brazil. This five-year study is the first to quantify the relationship between selective logging, where loggers extract individual trees from the rain forest, and complete deforestation, or clear-cutting.
Carnegie Institution of Washington: New Satellite Study Doubles Forest Disturbance Estimates in Brazil-Impacts Widespread
Results from a new large-scale, high-resolution satellite data analysis indicate that forest degradation in the Brazilian Amazon has been underestimated by half. The study, conducted by lead author, Dr. Greg Asner, of the Carnegie Institution Department of Global Ecology and colleagues, is published in the October 21, 2005, issue of Science, and has far-reaching ecological impacts for the region and beyond.
