The Sonoran Desert ( es, Desierto de Sonora) is a desert in North America and

ecoregion An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller than a biogeographic realm. Ecoregions cover relatively large areas o ...

that covers the northwestern Mexican states of

Sonora Sonora (), officially Estado Libre y Soberano de Sonora ( en, Free and Sovereign State of Sonora), is one of the 31 states which, along with Mexico City, comprise the Federal Entities of Mexico. The state is divided into 72 municipalities; the ...

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Mex ...

, and Baja California Sur, as well as part of the southwestern United States (in

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a U.S. state, state in the Southwestern United States. It is the list of U.S. states and territories by area, 6th largest and the list of U.S. states and territories by population, 14 ...

and

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

). It is the hottest desert in both Mexico and the United States. It has an area of . In phytogeography, the Sonoran Desert is within the Sonoran Floristic province of the Madrean Region of southwestern North America, part of the Holarctic realm of the northern Western Hemisphere. The desert contains a variety of unique

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

plant Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...

s and

animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

s, notably, the saguaro (''Carnegiea gigantea'') and

organ pipe cactus ''Stenocereus thurberi'', the organ pipe cactus, is a species of cactus native to Mexico and the United States. The species is found in rocky desert. Two subspecies are recognized based on their distribution and height. The Organ Pipe Cactus Nati ...

(''Stenocereus thurberi''). The Sonoran Desert is clearly distinct from nearby deserts (e.g., the Great Basin, Mojave, and

Chihuahuan desert The Chihuahuan Desert ( es, Desierto de Chihuahua, ) is a desert ecoregion designation covering parts of northern Mexico and the southwestern United States. It occupies much of far West Texas, the middle to lower Rio Grande Valley and the lowe ...

s) because it provides subtropical warmth in winter and two seasons of rainfall (in contrast, for example, to the Mojave's dry summers and cold winters). This creates an extreme contrast between aridity and moisture.

Location

The Sonoran desert wraps around the northern end of the Gulf of California, from Baja California Sur ( El Vizcaíno Biosphere Reserve in central and Pacific west coast, Central Gulf Coast subregion on east to southern tip), north through much of

, excluding the central northwest mountains and Pacific west coast, through southeastern California and southwestern and southern Arizona to western and central parts of

. It is bounded on the west by the Peninsular Ranges, which separate it from the California chaparral and woodlands (northwest) and Baja California Desert (Vizcaino subregion, central and southeast) ecoregions of the Pacific slope. The Gulf of California xeric scrub ecoregion lies south of the Sonoran desert on the Gulf of California slope of the Baja California Peninsula. To the north in California and northwest Arizona, the Sonoran Desert transitions to the colder-winter, higher-elevation Mojave, Great Basin, and Colorado Plateau deserts. The coniferous Arizona Mountains forests are to the northeast. The

Chihuahuan Desert The Chihuahuan Desert ( es, Desierto de Chihuahua, ) is a desert ecoregion designation covering parts of northern Mexico and the southwestern United States. It occupies much of far West Texas, the middle to lower Rio Grande Valley and the lowe ...

and

Sierra Madre Occidental pine–oak forests The Sierra Madre Occidental pine–oak forests ( es, Bosques de pino-roble de la Sierra Madre Occidental) are a Temperate broadleaf and mixed forests ecoregion of the Sierra Madre Occidental range from the southwest USA region to the western p ...

are at higher elevations to the east. To the south the Sonoran–Sinaloan transition subtropical dry forest is the transition zone from the Sonoran Desert to the tropical dry forests of the Mexican state of Sinaloa.

Sub-regions

The desert's sub-regions include the Colorado Desert of southeastern California; and the Yuma Desert east of the north-to-south section of the

Colorado River The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid watershed that encompasses parts of seven U.S. s ...

in southwest Arizona. In the 1957 publication ''Vegetation of the Sonoran Desert'', Forrest Shreve divided the Sonoran Desert into seven regions according to characteristic vegetation: Lower Colorado Valley, Arizona Upland, Plains of Sonora, Foothills of Sonora, Central Gulf Coast, Vizcaíno Region, and Magdalena Region. Many ecologists consider Shreve's Vizcaíno and Magdalena regions, which lie on the western side of the Baja California Peninsula, to be a separate

, the Baja California Desert. Within the southern Sonoran Desert in Mexico is found the Gran Desierto de Altar, with the

El Pinacate y Gran Desierto de Altar Biosphere Reserve El Pinacate y Gran Desierto de Altar Biosphere Reserve ( es, Reserva de la Biosfera El Pinacate y Gran Desierto de Altar) is a biosphere reserve and UNESCO World Heritage Site managed by the federal government of Mexico, specifically by Secreta ...

, extending of desert and mountainous regions. The biosphere reserve includes the only active erg dune region in North America. The nearest city to the biosphere reserve is Puerto Peñasco ('Rocky Point') in the state of

Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...

. ;Sub-regions Sonoran Desert sub-regions include: * Colorado Desert * Gran Desierto de Altar *

Lechuguilla Desert The Lechuguilla Desert is a small desert located in southwestern Arizona near the U.S.-Mexico border. It is considered to be part of the Lower Colorado Valley region of the Sonoran Desert. It lies in a north–south direction between the Gila Mo ...

Tonopah Desert The Tonopah Desert is a small desert plains region of the Sonoran Desert, located west of Phoenix, Arizona. It is adjacent north of Interstate 10 and lies at the southwest intersection of the Hassayampa River with the Gila River. The Tonopah Des ...

Yuha Desert The Yuha Desert is a section of the Sonoran Desert located in the Imperial Valley of California; south of Interstate 8, west of El Centro, and north of the international border. Unique aspects of the Yuha Desert include the Oyster Shell Beds, De An ...

* Yuma Desert

Climate

The Sonoran desert has an arid subtropical climate. In the lower-elevation portions of the desert, temperatures are warm year-round, and rainfall is infrequent and irregular, often less than 90 mm (approx. 3.5”) annually. The Arizona uplands are also warm year-round, but they receive 100–300 mm (approx. 4-12”) of average annual rainfall, which falls in a more regular bi-seasonal pattern.

Flora

Many plants not only survive, but thrive in the harsh conditions of the Sonoran Desert. Many have evolved to have 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. The Sonoran Desert includes plant genera and species from the agave family, palm family,

cactus A cactus (, or less commonly, cactus) is a member of the plant family Cactaceae, a family comprising about 127 genera with some 1750 known species of the order Caryophyllales. The word ''cactus'' derives, through Latin, from the Ancient Gre ...

family, legume family, and numerous others. The Sonoran is the only place in the world where the famous saguaro cactus (''Carnegiea gigantea'') grows in the wild. Cholla (''Cylindropuntia'' spp.), beavertail (''Opuntia basilaris''), hedgehog (''Echinocereus'' spp.), fishhook (''Ferocactus wislizeni''), prickly pear (''Opuntia'' spp.),

nightblooming cereus Night-blooming cereus is the common name referring to a large number of flowering ceroid cacti that bloom at night. The flowers are short lived, and some of these species, such as '' Selenicereus grandiflorus'', bloom only once a year, for a ...

(''Peniocereus'' spp.), and organ pipe (''Stenocereus thurberi'') are other taxa of cacti found here. Cactus provides 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 ''Ephedra'' is a genus of gymnosperm shrubs. The various species of ''Ephedra'' are widespread in many arid regions of the world, ranging across southwestern North America, southern Europe, northern Africa, southwest and central Asia, northern ...

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. Prosopis velutina Anza-Borrego

Ascending from the valley up bajadas, various subtrees such as

velvet mesquite ''Prosopis velutina'', commonly known as velvet mesquite, is a small to medium-sized tree. It is a legume adapted to a dry, desert climate. Though considered to be a noxious weed in states outside its natural range, it plays a vital role in the ...

(''Prosopis velutina''), palo verde (''Parkinsonia florida''),

desert ironwood ''Olneya tesota'' is a perennial flowering tree of the family Fabaceae, legumes (peas, beans, etc.), which is commonly known as ironwood, desert ironwood, or palo fierro in Spanish. It is the only species in the monotypic genus ''Olneya''. Th ...

(''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 ''Vachellia constricta'', also known commonly as the whitethorn acacia, is a shrub native to Mexico and the Southwestern United States, with a disjunct eastern population in Virginia and Maryland. Distribution In the Southwest ''V. constricta'' ...

(''Acacia constricta''), fairy duster, and jojoba. In the desert subdivisions found on Baja California, cardon cactus, elephant tree, and boojum tree occur. Washingtonia filifera Anza-Borrego

The California fan palm (''Washingtonia filifera'') is found in the Colorado Desert section of the Sonoran Desert, the only native palm in California, among many other introduced Arecaceae genera and species. It is found at spring-fed

oases In ecology, an oasis (; ) is a fertile area of a desert or semi-desert environmentAnza Borrego Desert State Park, Joshua Tree National Park, and the Kofa National Wildlife Refuge.

Fauna

The Sonoran Desert is home to a wide variety of animals, birds and other creatures. such as the Gila monster, bobcat, mule deer, antelope jackrabbit, burrowing owl, greater roadrunner, western diamondback rattlesnake, and elf owl. There are three hundred fifty bird species, 20 amphibian species, over 100 reptile species, 30 native fish species, over 1000 native bee species, and more than 2,000 native plant species found in the desert area. 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 the 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

, as well as populations in Mexico. The largest city in the Sonoran Desert is

Phoenix, Arizona Phoenix ( ; nv, Hoozdo; es, Fénix or , yuf-x-wal, Banyà:nyuwá) is the capital and most populous city of the U.S. state of Arizona, with 1,608,139 residents as of 2020. It is the fifth-most populous city in the United States, and the o ...

, 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 Urban sprawl (also known as suburban sprawl or urban encroachment) is defined as "the spreading of urban developments (such as houses and shopping centers) on undeveloped land near a city." Urban sprawl has been described as the unrestricted growt ...

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,Table 1: Annual Estimates of the Population of Metropolitan and Micropolitan Statistical Areas: April 1, 2000 to July 1, 2006 (CBSA-EST2006-01)
,

United States Census Bureau The United States Census Bureau (USCB), officially the Bureau of the Census, is a principal agency of the U.S. Federal Statistical System, responsible for producing data about the American people and economy An economy is an area of th ...

, 2007-04-05. Accessed 2007-09-11 and Mexicali,

, with a similarly sized metropolitan population of around 1,000,000. The metropolitan area of Hermosillo,

, has a population close to 900,000. Ciudad Obregón,

, in the southern part of the desert, has a population of 375,800.

California

The

Coachella Valley , map_image = Wpdms shdrlfi020l coachella valley.jpg , map_caption = Coachella Valley , location = California, United States , coordinates = , width = , boundaries = Salton Sea (southeast), Santa Rosa Mountains (southwest), San Jacin ...

, 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. Gateway to the Springs

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 ''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is nati ...

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 Coachella may refer to: * Coachella, California * Coachella Canal, in California * Coachella (festival), an annual music and arts festival in California * "Coachella – Woodstock in My Mind "Coachella – Woodstock In My Mind" is a song by Ame ...

, Calexico, El Centro,

Imperial Imperial is that which relates to an empire, emperor, or imperialism. Imperial or The Imperial may also refer to: Places United States * Imperial, California * Imperial, Missouri * Imperial, Nebraska * Imperial, Pennsylvania * Imperial, Texas ...

, and Blythe.

United States–Mexico border region

Straddling the US-Mexican border with low levels of human-installed security, the Sonoran desert is a route for unauthorized entry across the border. The harsh conditions mean that the 3-to-5-day march, usually moving at night to minimize exposure to the heat, sometimes results in death.

Protected areas

There are many National Parks and Monuments; federal and state

nature reserve A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, or features of geological or ...

s and

wildlife refuge A nature reserve (also known as a wildlife refuge, wildlife sanctuary, biosphere reserve or bioreserve, natural or nature preserve, or nature conservation area) is a protected area of importance for flora, fauna, or features of geological o ...

s; state, county, and city parks; and government or nonprofit group operated natural history museums, science research institutes, and

botanical garden A botanical garden or botanic gardenThe terms ''botanic'' and ''botanical'' and ''garden'' or ''gardens'' are used more-or-less interchangeably, although the word ''botanic'' is generally reserved for the earlier, more traditional gardens, an ...

s and desert landscape

garden A garden is a planned space, usually outdoors, set aside for the cultivation, display, and enjoyment of plants and other forms of nature. The single feature identifying even the wildest wild garden is ''control''. The garden can incorporate bot ...

s. * 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 The Sonoran Desert National Monument was created in 2001 in Arizona, to enhance protection of the unique resources of the Sonoran Desert, with .
:Reference
Sonoran Desert National Monument
, Bureau of Land Management, U. S. Department of the Interior. Accessed on line June 17, 2009. * 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 Coachella Valley National Wildlife Refuge is a protected area in Riverside County, California's Coachella Valley. It lies within the unincorporated community of Thousand Palms, just north of Palm Desert. The refuge contains the majority of cri ...

* Cabeza Prieta National Wildlife Refuge * Kofa National Wildlife Refuge * South Mountain Park * Sonoran Arthropod Studies Institute

References

Parks and recreation areas

Saguaro National Park: official website

Anza–Borrego Desert State: official website

Organ Pipe Cactus National Monument: official website

Arizona State Parks: official website (desert plants)
{{Authority control Basin and Range Province Deserts and xeric shrublands in the United States Deserts and xeric shrublands Deserts of Arizona Deserts of California Deserts of Mexico Deserts of North America Deserts of the Lower Colorado River Valley Ecoregions of Mexico Ecoregions of the United States Floristic provinces Geography of Southern California Geologic provinces of California Gulf of California Madrean Region Physiographic sections Physiographic regions of Mexico Physiographic regions of the United States Desert, Sonoran Nearctic ecoregions