Sonoran Desert

Flora

thumb|The Sonoran Desert near [[Tucson, Arizona during winter]]

Many plants not only survive, but thrive in the harsh conditions of the Sonoran Desert. Many have evolved specialized adaptations to the desert climate. The Sonoran Desert's bi-seasonal rainfall pattern results in more plant species than any other desert in the world. Cholla (Cylindropuntia spp.), beavertail (Opuntia basilaris), hedgehog (Echinocereus spp.), fishhook (Ferocactus wislizeni), prickly pear (Opuntia spp.), nightblooming cereus (Peniocereus spp.), and organ pipe (Stenocereus thurberi) are other taxa of cacti found here. Cacti provide food and homes to many desert mammals and birds, with showy flowers in reds, pinks, yellows, and whites, blooming most commonly from late March through June, depending on the species and seasonal temperatures.

Creosote bush (Larrea tridentata) and bur sage (Ambrosia dumosa) dominate valley floors. Indigo bush (Psorothamnus fremontii) and Mormon tea are other shrubs that may be found. Wildflowers of the Sonoran Desert include desert sand verbena (Abronia villosa), desert sunflower (Geraea canescens), and evening primroses.

thumb|[[Prosopis velutina|Velvet mesquite (Prosopis velutina)]]

Ascending from the valley up bajadas, various subtrees such as velvet mesquite (Prosopis velutina), palo verde (Parkinsonia florida), desert ironwood (Olneya tesota), desert willow (Chilopsis linearis ssp. arcuata), and crucifixion thorn (Canotia holacantha) are common, as well as multi-stemmed ocotillo (Fouquieria splendens). Shrubs found at higher elevations include whitethorn acacia (Acacia constricta), fairy duster, and jojoba. In the desert subdivisions found on Baja California, cardon cactus, elephant tree, and boojum tree occur.

thumb|[[Washingtonia filifera, the desert fan palm, in Anza Borrego Desert State Park]]

The California fan palm (Washingtonia filifera) is the only palm species native to the western United States. Within the Sonoran Desert it is most characteristic of the Colorado Desert of southeastern California, where it forms groves around spring-fed oases such as those in Anza-Borrego Desert State Park and Joshua Tree National Park. Outside California, natural populations also occur in Arizona, including at Castle Creek in the Bradshaw Mountains, the Hassayampa River Preserve, and Kofa National Wildlife Refuge.

Fauna

The Sonoran Desert is home to a wide variety of fauna that have adapted and thrive in the hot, arid desert environment, such as the Gila monster, bobcat, mule deer, pronghorn antelope, jackrabbit, burrowing owl, greater roadrunner, western diamondback rattlesnake, and elf owl. There are 350 bird species, 20 amphibian species, over 100 reptile species, 30 native fish species, and over 1000 native bee species found in the Sonoran. The Sonoran Desert area southeast of Tucson and near the Mexican border is vital habitat for the only population of jaguars living within the United States. The Colorado River Delta was once an ecological hotspot within the Sonoran desert due to the Colorado river in this otherwise dry area, but the delta has been greatly reduced in extent due to damming and use of the river upstream. Species that have higher heat tolerance are able to thrive in the conditions of the Sonoran Desert. One such insect species that has evolved a means to thrive in this environment is Drosophila mettleri, a Sonoran Desert fly. This fly contains a specialized P450 detoxification system that enables it to nest in the cool region of exudate moistened soil. Thus, the fly is one of few that can tolerate the high desert temperatures and successfully reproduce.

Human population

The Sonoran Desert is home to the cultures of over 17 contemporary Native American tribes, with settlements at American Indian reservations in California and Arizona, as well as populations in Mexico.

The largest city in the Sonoran Desert is Phoenix, Arizona, with a 2017 metropolitan population of about 4.7 million. Located on the Salt River in central Arizona, it is one of the fastest-growing metropolitan areas in the United States. In 2007 in the Phoenix area, desert was losing ground to urban sprawl at a rate of approximately per hour.

The next largest cities are Tucson, in southern Arizona, with a metro area population of just over 1 million, and Mexicali, Baja California, with a similarly sized metropolitan population of around 1,000,000. The metropolitan area of Hermosillo, Sonora, has a population close to 900,000. Ciudad Obregón, Sonora, in the southern part of the desert, has a population of 375,800.

California

The Coachella Valley, located in the Colorado Desert section of the Sonoran Desert, has a population of 365,000. Several famous Southern California desert resort cities such as Palm Springs and Palm Desert are located here.

thumb|left|The entrance to [[Palm Springs, California via Highway 62]]

During the winter months, from November to April, the daytime temperatures in the Coachella Valley range from 70 °F (21 °C) to 90 °F (32 °C) and corresponding nighttime lows range from 46 °F (8 °C) to 68 °F (20 °C) making it a popular winter resort destination. Due to its warm year-round climate citrus and subtropical fruits such as mangoes, figs, and dates are grown in the Coachella Valley and adjacent Imperial Valley. The Imperial Valley has a total population of over 180,000 and has a similar climate to that of the Coachella Valley. Other cities include Borrego Springs, Indio, Coachella, Calexico, El Centro, Imperial, and Blythe.

United States–Mexico border region

Straddling the Mexico–United States border, the Sonoran desert is an important migration corridor for humans and animals. The harsh climate conditions and border militarism mean that the journey can be perilous, usually moving at night to minimize exposure to the heat.

Protected areas

thumb|upright|[[Mexican Gold Poppy|Mexican goldpoppies in the Sonoran Desert National Monument]]

There are many National Parks and Monuments; federal and state nature reserves and wildlife refuges; state, county, and city parks; and government or nonprofit group operated natural history museums, science research institutes, and botanical gardens and desert landscape gardens.

Index: Protected areas of the Sonoran Desert
Index: Protected areas of the Colorado Desert

;Sonoran Desert protected areas include:

Arizona–Sonora Desert Museum
Sonoran Desert National Monument
Boyce Thompson Arboretum State Park – Sonoran Desert flora arboretum
Anza–Borrego Desert State Park
Organ Pipe Cactus National Monument
Saguaro National Park
Joshua Tree National Park
Reserva de la Biosfera el Pinacate y Gran Desierto de Altar – Pinacate National Park, in Sonora, Mexico
Indio Hills Palms State Reserve
Coachella Valley National Wildlife Refuge
Cabeza Prieta National Wildlife Refuge
Kofa National Wildlife Refuge
South Mountain Park
Sonoran Arthropod Studies Institute
Skyline Regional Park

Notes

References

External links

Arizona–Sonora Desert Museum
Map of the Sonoran Desert Ecoregion
Sonoran Desert and its subdivisions – with photos.
Timeline of the Sonoran desert
An Overview of the Sonoran Desert, by William G. McGinnies
The Sonoran Desert Naturalist
Very short overview of Sonoran Desert Geology
Sonoran Desert images at bioimages.vanderbilt.edu (slow modem version)
International Sonoran Desert Alliance
Sounds of the Sonoran Desert)

Parks and recreation areas

Sonoran Desert National Monument: official website
Saguaro National Park: official website
Anza–Borrego Desert State: official website
Organ Pipe Cactus National Monument: official website
Joshua Tree National Park: official website
South Mountain Park – Preserve
Arizona State Parks: official website (desert plants)