Declassified spy satellite images, combined with aerial photos, document an invasion of honey mesquite bushes into a former arid grassland that is now part of a long-term scientific study of the processes of desertification in southern New Mexico.
An interpretation of the 2-meter resolution overviews of desert terrain will be presented in a Thursday, Aug. 10 session of the Ecological Society of America's annual meeting in Snowbird, Utah.
By comparing 1937 and 1996 aerial photographs with military reconnaissance images made in the intervening years of 1966, 1976 and 1983, scientists with the Jornada Basin Long-Term Ecological Research Program near Las Cruces, N.M., were able to document "an increase in both shrub numbers and area," according to the scientists.
"Honey mesquite now dominates large areas of former desert grassland throughout the Southwest," their presentation says. "Despite its importance, not much is known about the dynamics of individual shrubs over long periods and large areas."
But covert overhead surveillance can help. Initial results "show that remote sensing imagery is an appropriate tool for examining shrub invasion in desert grasslands," according to the poster, which was prepared by five researchers in the National Science Foundation-funded desertification study -- Sarah Goslee, Kris Havstad, William Schlesinger, Debra Peters and Al Rango.
Goslee, of New Mexico State University, electronically processed the images in a way that highlights the increase in mesquite numbers. Schlesinger, a Duke University biology professor and a principal investigator of the Jornada project, helped get the satellite images declassified.
"The number of mesquite at the Jornada has increased continuously, not just during the drought of the 1950s," Schlesinger said in an interview. "And most of the shrubs arriving early on have held their ground to the present day."
Schlesinger is among a special group of scientists, called the Medea Committee, who have received security clearance to review spy satellite images that might be of benefit to research if declassified. The idea of declassifying images for science was originally championed by Vice President Al Gore when he was in the U.S. Senate.
In a 1996 article in the journal Global Change Biology, Schlesinger and a MITRE Corp. researcher also described how they used intelligence satellite images and aerial photography to show that several decades of drought in the Sudan had no impact on tree abundance there.
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