AJO, AZ - MARCH 27: A rattlesnake tastes the air on the Cabeza Prieta National Wildlife Reserve on March 27, 2006 near Ajo, Arizona. Because of escalating environmental problems associated with the region?s massive illegal immigration and stepped up border enforcement efforts, the vast and desert wilderness in and around the Cabeza Prieta National Wildlife Reserve and Organ Pipe National Monument has been described as the nation?s most embattled wilderness by reserve officials. Immigrants crossing the desert are discarding tons of used water bottles, excess clothing and other trash as they elude the Border Patrol. Border agents trying to stop them, and vehicles that cross the border illegally, are accelerating widespread off-road vehicle damage on the fragile Sonoran Desert plain at an unprecedented rate. (Photo by David McNew/Getty Images)