Warm Desert
The great American desert cuts a vast swath across the nation’s southwestern quarter. Through modern engineering marvels—dams, irrigation systems, and air conditioning—our society has defied the desert and built upon it a series of boomtowns (Las Vegas, Phoenix, Tucson).
Location
Southeastern California south and east through southern Arizona, northern Sonora, Baja California, southern New Mexico, and throughout northeastern Mexico.
Climate
Average annual temperature of 22ºC (71ºF) with annual precipitation averaging 58mm or about 2.25 inches.
Features
Basin and range physiography predominates these vast, ancient landscapes, with Pleistocene alluvial features forming bajadas among the mountain toeslopes. Extensive desert dunes occur in selected locations, occasionally stabilized by native grasses. Other areas of vast desert playas typically occur adjacent (upwind) to dune fields. This Division features different forms of desert scrub, from creosotebush to Joshua tree to palo verde & mixed cacti (including the emblematic saguaro cacti), to mesquite woodlands, extensive desert washes and cottonwood-willow riparian woodlands. Division includes portions of the Sierra Madre sky islands from southern-most Arizona and New Mexico, which features mixed oak and conifer oak woodlands – more characteristic of northern Mexico.
History and Trends
Always sparsely inhabited, ancient cultures developed irrigation in the Arizona desert. Most urban and agriculture developed recently with access to water from the Colorado River, making cities of Las Vegas, Phoenix, and Tucson possible. New invasive plant introductions (e.g., African bufflegrass) have profound impact in desert vegetation through introduction of fire that never occurred naturally.