thumb|250px|Colorado Desert landscape

The Colorado Desert is a part of the larger Sonoran Desert located in California, United States, and Baja California, Mexico. It encompasses approximately , including the heavily irrigated Coachella, Imperial and Mexicali valleys. It is home to many unique flora and fauna.

Geography and geology

thumb|The [[Algodones Dunes]]

The Colorado Desert is a subregion of the larger Sonoran Desert, covering about . The desert occupies Imperial County, parts of San Diego and Riverside counties, and a small part of San Bernardino County in California, United States, as well as the northern part of Mexicali Municipality in Baja California, Mexico.

Most of the Colorado Desert lies at a relatively low elevation, below , with the lowest point of the desert floor at below sea level, at the Salton Sea. Although the highest peaks of the Peninsular Ranges reach elevations of nearly , most of the region's mountains do not exceed .

In this region, the geology is dominated by the transition of the tectonic plate boundary from rift to fault. The southernmost strands of the San Andreas Fault connect to the northernmost extensions of the East Pacific Rise. Consequently, the region is subject to earthquakes, and the crust is being stretched, which will result in a sinking of the terrain over time.

Climate

The Colorado Desert's climate distinguishes it from other deserts. The region experiences greater summer daytime temperatures than higher-elevation deserts and almost never experiences frost. In addition, the Colorado Desert experiences two rainy seasons per year (in the winter and late summer), especially toward the southern portion of the region; the more northerly Mojave Desert usually has only winter rains.

The west coast Peninsular Ranges, or other west ranges, of Southern California–northern Baja California, block most eastern Pacific coastal air and rains, producing an arid climate.

In the Colorado Desert's arid environment, aquatic and wetland habitats are limited in extent but are critically important to wildlife. Runoff from seasonal rains and groundwater springs forms desert arroyos, desert fan palm oases, freshwater marshes, brine lakes, desert washes, ephemeral and perennial streams, and desert riparian vegetation communities dominated by cottonwood, willow, and non-native tamarisk. Two of the region's most significant aquatic systems are the Salton Sea and the Colorado River. While most desert wildlife depend on aquatic habitats as water sources, a number of species, such as the arroyo toad, desert pupfish, Yuma rail, and southwestern willow flycatcher, are restricted to these habitats. In some places, summer rains produce short-lived seasonal pools that host uncommon species like Couch's spadefoot toad.

thumb|[[Washingtonia filifera in Anza Borrego Desert State Park]]

Desert fan palm oases are rare ecological communities found only in the Colorado Desert. They occur only where permanent water sources are available, such as at springs or along fault lines, where groundwater is forced to the surface by the movement of hard impermeable rock, and can be found in the San Jacinto, Santa Rosa, and Little San Bernardino mountains, in the canyons of Anza-Borrego Desert State Park, and along the San Andreas Fault in the Coachella Valley.

Endemic flora

Some sub-regions of the Colorado Desert contain endemic flora. Along the Lower Colorado River Valley, in-flow side canyons, flatlands, or low-to-higher level elevations, at least one such plants occur: Salvia greatae (Orocopia sage).

National and State Parks

  • Joshua Tree National Park
  • Chuckwalla National Monument
  • Imperial NWR
  • Sonny Bono Salton Sea NWR
  • Indio Hills Palms
  • Anza-Borrego Desert State Park
  • Ocotillo Wells State Vehicular Recreation Area
  • Picacho State Recreation Area
  • Heber Dunes State Vehicular Recreation Area
  • Salton Sea State Recreation Area

Environmental issues

The Colorado Desert is one of the least-populous regions in California, but human activities have had substantial impacts on the region's habitats and wildlife. Many unique communities, particularly aquatic and dune systems, are limited in distribution and separated by vast expanses of inhospitable, arid desert terrain. Even limited human disturbances can have markedly deleterious effects on the endemic and sensitive species supported by these unique regional systems.