The Sonoran Desert
The Sonoran Desert includes the southwestern third of Arizona, a small area of southeastern California, most of Baja California, and the western half of Sonora, Mexico--in total, some 500,000 square miles in the U.S. and Mexico. The map shown here further divides the Sonoran Desert into six regions. These subdivisions are based on the plant life that is characteristic of each region and were described in 1957 by the prominent plant ecologist, Forrest Shreve, in Vegetation of the Sonoran Desert. A description of these subdivisions can be found in An Overview of the Sonoran Desert, an essay by William G. McGinnies that can be found on the Internet Archive.
Within these subdivisions are rich biotic communities that make the Sonoran Desert the most biologically diverse of north America's deserts. Habitats of the Sonoran Desert range from extremely hot, arid desert to semiarid tropical forests, from semidesert glassland to higher elevation coniferous forests, from chaparral to thornscrub. Visit the Arizona-Sonora Desert Museum's Center for Sonoran Desert Studies for more information about the biotic communities of the Sonoran Desert.