Using advanced remote-sensing techniques from a U-2 surveillance plane and field studies, scientists from the Carnegie Institution Department of Global Ecology have for the first time determined large-scale interactions between ecosystems and the climate during the process of desertification. The study is a milestone both for the new methods employed and for understanding what is happening as agricultural and grazing lands change into desert—a top environmental worry of the United Nations.

“Grazing is the major form of land use on the planet, with the dry, semi-arid, and sub-humid regions supporting most of it throughout the world,” explained Dr. Gregory Asner, lead author at Carnegie. “Some of these regions are turning into unusable desert so quickly that the United Nations has put the problem at the top of its environmental agenda. The challenge for science—to understand what is happening to ecosystems during desertification—has been enormous because the areas are so vast it is impossible to study the processes at the field level alone. Our five-year project in the Northern Chihuahua region of New Mexico has successfully shown how the NASA Airborne Visible and Infrared Imaging Spectrometer (AVIRIS), aboard a NASA U-2, can be used to analyze the vegetation and soil changes in response to rain variation over large areas. I believe that the technique could become a standard for future global desertification studies.”

Using the (AVIRIS), the scientists are able to analyze the physical structure of ecosystems including the live and dead plants. The data are viewed in 3-dimensions at very high resolution and can give a much broader picture of the processes at work than previous methods. They are able to discern carbon cycling and a variety of other chemical and biological activities.

“We found that a long-term decrease in litter cover is the most evident sign when an area begins to change to desert,” stated Asner. “More bare soil areas and changes in green vegetation are also apparent, but they are secondary. Up to now the scientific community has focused on bare soil much more than the loss of natural litter as dry areas become desert. We also noted how the different vegetation types changed in response to the variation in rain. As areas exhibited more desert-like vegetation, there was a shift in plant responses from summer to winter precipitation events,” he concluded. (For the complete story see http://www.carnegieinstitution.org/news_releases/news_041220.html.)