Overview: Sonoran Desert

Deserts know no political boundaries. The Sonoran Desert lies in parts of four states in two countries: Sonora and Baja California in Mexico, and southern Arizona and the southeastern corner of California in the United States. Due to fuzzy regional boundaries, the extent and borders of the Sonoran Desert vary depending on the source. For example, the Arizona-Sonoran Desert Museum description includes the San Francisco Peaks and Grand Canyon of Arizona, Baja California and the gulf of California, and the entire state of Sonora Mexico. In other research and writing on the Sonoran Desert, only the northeastern corner of Baja California is included as part of the region. Still, some see the Sonoran Desert as including the San Diego area of Southern California.

Researchers such as McGinnies (1981) and Turner, Bowers, and Burgess (1995), however, who define the region by vegetation type, present a more narrowly defined area. For them, boundaries are relatively clear in places of sharp changes in elevation, but less clear in rolling plains. The upper elevational limit for Sonoran Desert vegetation is approximately 3,100 feet but may be as high as 4,265 feet on warmer, drier south facing slopes. Based on vegetation types and early work by Shreve (1951), these researchers place the northern border at the Mogollon Rim in Arizona (excluding the northern highlands and San Franciso Peaks); the eastern boundary just east of Tucson but west of the Galiuro and Santa Rita Mountains of Arizona and west of the Sierra Madre in Sonora Mexico; and the western boundary approximately on a line from Needles to Indio in California thus including the Salton Sea, but excluding the area around San Diego. The Sonoran Desert extends south in Sonora almost to the Rio Mayo. Most, but not all of Baja California and Baja Califronia Sur as well as the Gulf Coast Islands are also included in the Sonoran Desert.

Estimates of the region's size range from approximately 55,000, 87,000, 100,000, to 120,000 square miles. Because this site includes material that uses Shreve's (1951) delineation of the Sonoran Desert, the largest area is used. In this case, the Sonoran Desert is defined as covering 120,000 square miles which includes the subregion "Foothills of Sonora".

Further overview of the Sonoran Desert