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Desert Diary
Ecology/Shrub Invasion


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Much of the northern Chihuahuan Desert that now is characterized by large numbers of shrubs and only scanty grass once was grassland with few shrubs. Drought and overgrazing allowed invasion of mesquite, creosotebush, and other shrubs. Honey mesquite is one of the more successful invaders, and there have been numerous attempts to eradicate it. Control measures generally have involved bulldozing or the use of herbicides. Both measures seem to work--but not for long.

Studies in southern New Mexico indicate that mesquite populations continue to expand and increase in density even in those areas where control measures undertaken in the past were thought to be successful. For example, bulldozing and herbicides in two areas in 1959 and 1960 eradicated nearly 100% of the mesquite. By 1988, however, the average density was some 150 plants per acre. People sometimes question when we talk about how fragile the desert is, but this shrub invasion is a case in point. Many of the desert grasslands have been so damaged that we presently don't know how to return them to their earlier state.
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Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.


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