When Webster defined a desert as a “dry, barren region, largely treeless and sandy” he was not thinking of the 50,000 square mile Great American Desert of the southwestern United States and northern Mexico. Most of it is usually dry and parts may be sandy, but as a whole, it is far from barren and treeless. Heavily vegetated with gray-green shrubs, small but robust trees, pygmy forests of grotesque cactuses and stiff-leaved yuccas, and myriads of herbaceous plants, the desert, following rainy periods, covers itself with a blanket of delicate, fragrant wildflowers.
Edmund C. Jaegar, author of several books on deserts, reports that the California deserts alone support more than 700 species of flowering plants.
The late Dr. Forrest Shreve, for many years Director of the Desert Laboratory of the Carnegie Institution near Tucson, Arizona, defined a desert as “a region of deficient and uncertain rainfall.” He divided the Great American Desert into four major sections: (1) Chihuahuan (chee-WAH-wahn), including the Mexican States of Chihuahua and Coahuila (coa-WHEE-lah), southwestern Texas, and south-central New Mexico; (2) Sonoran, including Baja California, southwestern Arizona, and northwestern Sonora; (3) Mojave (moh-HAH-vee), Colorado, including south-eastern California and extreme southern Nevada; (4) Great Basin, including Nevada, Utah, southwestern Idaho and southeastern Oregon.
Since the steppes and mesas of the Great Basin Desert have generally lower temperatures, higher elevations, and greater precipitation than the other three sections.