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Desert Laboratory for the WorldBy Don Comis
July 1, 2004
The fifth year of drought on the Agricultural Research Service's 193,000-acre Jornada Experimental Range at Las Cruces, N.M., has sped up the loss of grazing land to brush invasions. In 1912, the U.S. Department of Agriculture acquired the Jornada, located in the vast Chihuahuan Desert.
Jornada scientists led by Kris Havstad, an ARS rangeland scientist, analyzed USDA aerial photographs of the Jornada taken from the 1930s on and noticed that shrubs seemed better able to outcompete grass in dry times. The historical data showed that vegetation reaches a threshold beyond which a change--such as from grass to brush--is irreversible.
The scientists are investigating what drives this vegetation change. They are feeding historical and current data into computer models to help them predict, and avoid, the threshold.
The desert rangeland scientists' main concern is protecting the land's health while sustaining farming and ranching. They collaborate with numerous organizations. The National Science Foundation has a major presence at the Jornada, with its funding for the educational Chihuahuan Desert Nature Park and its inclusion of the Jornada in its Long-Term Ecological Research Network. The Jornada is one of 24 sites--including two in Antarctica--in the network, at which more than 1,100 scientists and students investigate various ecosystems.
The network's Jornada focus is on global warming, desert ecology, rangeland management and the worldwide threat of desertification. The ARS national program in rangeland management research melds well with this focus. Collaborative studies help infer causes and consequences of desertification.
Jornada researchers have about a century of historical data to rely on, in addition to new data being collected. They are finding ways to mine the past for clues to help rangeland managers around the world shape the landscape in desirable ways on the one-third of the Earth's land mass that is desert.
ARS is USDA's chief scientific research agency.