The Sonoran Desert () is a hot desert and ecoregion in North America that covers the northwestern Mexican states of Sonora, Baja California, and Baja California Sur, as well as part of the Southwestern United States (in Arizona and California). It is the hottest desert in Mexico. 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 endemism and , notably, the saguaro ( Carnegiea gigantea) and organ pipe cactus ( Stenocereus thurberi).
The Sonoran Desert is clearly distinct from nearby deserts (e.g., the Great Basin, Mojave Desert, and Chihuahuan deserts) 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.
It is bounded on the west by the Peninsular Ranges, which separate it from the California chaparral and woodlands (northwest) and Baja California desert (Vizcaíno 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 Desert, Great Basin, and Colorado Plateau deserts.
The coniferous Arizona Mountains forests are to the northeast. The Chihuahuan Desert and Sierra Madre Occidental pine–oak forests 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.
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, encompassing 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 Sonora.
According to the Köppen climate classification system, the majority of the Sonoran Desert has a hot desert climate ( BWh). Hot semi-arid climate ( BSh) exists on some of the higher elevation mountains within the desert, as well as in a continuous swath on the eastern and northeastern fringes as elevations gradually rise toward the Madrean Sky Islands in the east and the Mogollon Rim in the northeast. There are also a few small areas of cold semi-arid climate ( BSk) and even hot-summer Mediterranean climate ("Csa") on only the highest mountain peaks within the region.
The Sonoran is the only place in the world where the famous saguaro cactus ( Carnegiea gigantea) grows in the wild. Cylindropuntia ( Cylindropuntia spp.), beavertail ( Opuntia basilaris), Echinocereus ( Echinocereus spp.), fishhook ( Ferocactus wislizeni), Opuntia ( Opuntia spp.), Peniocereus ( 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 Ambrosia dumosa ( 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 Abronia villosa ( Abronia villosa), Geraea canescens ( Geraea canescens), and .
Ascending from the valley up bajadas, various subtrees such as velvet mesquite ( Prosopis velutina), palo verde ( Parkinsonia florida), Olneya tesota ( 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.MacMahon, J. A. Deserts. 1986, 638 pages
The California fan palm ( Washingtonia filifera) is found in the Colorado Desert section of the Sonoran Desert, the only native plant palm in California, among many other introduced Arecaceae genera and species. It is found at spring-fed oasis, such as in Anza Borrego Desert State Park, Joshua Tree National Park, and the Kofa National Wildlife Refuge.Hogan, C. M. 2009. California Fan Palm: Washingtonia filifera, GlobalTwitcher.com, ed. N. Stromberg
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. Make No Small Plans, Adelheid Fischer, ASU Research magazine. Accessed on line October 15, 2007
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, 2007-04-05. Accessed 2007-09-11 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.
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.
Sub-regions
Sonoran Desert sub-regions include:
Climate
Flora
Fauna
Human population
California
United States–Mexico border region
Protected areas
:Reference: Sonoran Desert National Monument , Bureau of Land Management, U. S. Department of the Interior. Accessed on line June 17, 2009.
See also
External links
Parks and recreation areas
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