| Chihuahuan Desert | |
|---|---|
 Chihuahuan desert landscape inBig Bend National Park | |
 Location map of Chihuahuan Desert | |
| Ecology | |
| Realm | Nearctic |
| Biome | Deserts and xeric shrublands |
| Borders | |
| Geography | |
| Area | 501,896 km2 (193,783 sq mi) |
| Countries | |
| States | |
| Coordinates | 30°32′26″N103°50′14″W / 30.54056°N 103.83722°W /30.54056; -103.83722 |
| Oceans or seas | Non |
| Rivers | Rio Grande |
| Climate type | Hot desert (BWh) andhot semi-arid (BSh) |
| Conservation | |
| Conservation status | Vulnerable |
| Global 200 | Yes |
| Protected | 35,905 km2 (13,863 sq mi) (7%)[1] |
TheChihuahuan Desert (Spanish:Desierto de Chihuahua,Desierto Chihuahuense) is adesertecoregion designation covering parts ofnorthern Mexico and thesouthwestern United States. It occupies much of farWest Texas, the middle to lower Rio Grande Valley and the lower Pecos Valley inNew Mexico, and a portion of southeasternArizona, as well as the central and northern portions of theMexican Plateau. It is bordered on the west by theSonoran Desert, theColorado Plateau, and the extensiveSierra Madre Occidental range, along with northwestern lowlands of theSierra Madre Oriental range. Its largest, continual expanse is located in Mexico, covering a large portion of the state ofChihuahua, along with portions ofCoahuila, north-easternDurango, the extreme northern part ofZacatecas, and small western portions ofNuevo León. With an area of about 501,896 km2 (193,783 sq mi),[1] it is thelargest hot desert in North America.[2] The desert is fairly young, existing for only 8,000 years.[3]
There are several larger mountain ranges in the Chihuahuan Desert, including theSierra Madre, theSierra del Carmen, theOrgan Mountains, theFranklin Mountains, theSacramento Mountains, theChisos Mountains, theGuadalupe Mountains, and theDavis Mountains. These create "sky islands" of cooler, wetter,climates adjacent to, or within the desert, and such elevated areas have both coniferous and broadleaf woodlands, including forests along drainages and favored exposures. The lower elevations of theSandia–Manzano Mountains, the Magdalena–San Mateo Mountains, and theGila Region partly border the Chihuahuan Desert and partly border other ecoregions that are not deserts.
There are few urban areas within the desert: the largest isCiudad Juárez with almost two million inhabitants;Chihuahua,Saltillo, andTorreón; and the US cities ofEl Paso,Alamogordo,Alpine,Benson,Carlsbad,Carrizozo,Deming,Fort Stockton,Fort Sumner,Las Cruces,Marfa,Pecos,Roswell, andWillcox are among the other communities in this ecoregion. Safford and Benson in Arizona are located in low elevations of the western edges of the Chihuahuan Desert, but in anecotone with theSonoran Desert.
According to theWorld Wide Fund for Nature the Chihuahuan Desert may be the most biologically diverse desert in the world as measured by species richness or endemism. The region has been badly degraded, mainly due to grazing.[4] Many native grasses and other species have become dominated by woody native plants, including creosote bush and mesquite, due toovergrazing and other urbanization. TheMexican wolf, once abundant, was nearly extinct and remains on the endangered species list.[5]
The desert is mainly arain shadow desert because the two main mountain ranges which bound the desert, theSierra Madre Occidental to the west and theSierra Madre Oriental to the east, block most moisture from the Pacific Ocean and the Gulf of Mexico, respectively.[3] Climatically, the desert mostly has an arid, mesothermal climate with one rainy season in the late summer and smaller amounts of precipitation in early winter, the mean daily temperature of the coldest month warmer than 0 °C (32 °F).[3] The majority of rain falls between late June and early October during theNorth American Monsoon when moist air from the Gulf of Mexico and the Sea of Cortez penetrates into the region, or much less frequently, when a tropical cyclone moves inland and stalls.[3][6]
Owing to its inland position and higher elevation than theSonoran Desert to the west, mostly varying from 480 to 1,800 m (1,575 to 5,906 ft) in elevation,[7] the desert has a slightly milder climate in the summer (though usually daytime June temperatures are in the range of 32 to 40 °C or 90 to 104 °F), with mild to cool winters and occasional to frequent freezes.[6] The hottest temperatures in the desert occur in lower elevation areas and valleys, including near the Rio Grande from south of El Paso into the Big Bend, and the Bolson de Mapimi.[7] A subtropical temperature regime describes lower elevations in the Texas Big Bend region up to the Presidio and Candelaria areas, then southward into similar elevations, while a warm temperate temperature regime describes higher elevations and areas farther north. The average annual temperature in the desert varies from about 13 to 22 °C (55 to 72 °F), depending on elevation and latitude.
The mean annual precipitation for the Chihuahuan Desert is 235 mm (9.3 in) with a range of approximately 150–400 mm (6–16 in), although it receives more precipitation than most other warm desert ecoregions.[3] Nearly two-thirds of the arid zone stations have annual totals between 225 and 275 mm (8.9 and 10.8 in).[8] Snowfall is scant except at the higher elevation edges. Northern and eastern portions have more definite winters than southern and western portions, receiving a portion of winter precipitation as snowfall most winters.[6]
The creosote bush (Larrea tridentata) is the dominant plant species on gravelly and occasional sandy soils in valley areas within the Chihuahuan Desert. The other species found with creosote bush depend on factors including the soil type, elevation, and degree of slope. Viscid acacia (Vachellia vernicosa), fourwing saltbush (Atriplex canescens), and tarbush (Flourensia cernua) are common in the desert scrub communities of northern portions, while broom dalea (Psorothamnus scoparius) occurs on sandy soils in western portions.Yucca and numerousOpuntia species are abundant on slopes and uplands in most areas, while Arizona rainbow cactus (Echinocereus polyacanthus) and Mexican fire-barrel cactus (Ferocactus pilosus) inhabit portions near the US–Mexico border.
Trees are less common than in nearby mountainous regions or the Sonoran Desert, due to greater aridity and less favorable precipitation seasons, but there are several common species in arroyos, floodplains, and mountain edges or canyons. Trees are often smaller in stature than in wetter areas, but those most common in Chihuahuan Desert arroyos include desert willow or mimbre (Chilopsis linearis), honey mesquite (Prosopis torreyana), netleaf hackberry (Celtis reticulata), and whitethorn (Vachellia constricta). Riparian floodplains in the ecoregion include Rio Grande cottonwood (Populus deltoides ssp. wislizeni), western cottonwood (Populus fremontii), and velvet ash (Fraxinus velutina); tornillo or screwbean mesquite (Prosopis pubescens) is limited to a few major river drainages such as the Rio Grande, and mostly in the floodplains.
Herbaceous plants, such as bush muhly (Muhlenbergia porteri), blue grama (Bouteloua gracilis), gypsum grama (B. breviseta), and hairy grama (B. hirsuta), are dominant in desert grasslands and near the mountain edges including the Sierra Madre Occidental. Lechuguilla (Agave lechuguilla), honey mesquite (Prosopis glandulosa),Opuntia macrocentra andEchinocereus pectinatus are the dominant species in westernCoahuila. Ocotillo (Fouquieria splendens), lechuguilla, andYucca filifera are the most common species in the southeastern part of the desert. Candelilla (Euphorbia antisyphilitica),Mimosa zygophylla,Acacia glandulifera and lechuguilla are found in areas with well-draining, shallow soils. The shrubs found near the Sierra Madre Oriental are exclusively lechuguilla, guapilla (Hechtia glomerata), Queen Victoria's agave (Agave victoriae-reginae), sotol (Dasylirion spp.), and barreta (Heliettaparvifolia), while the well-developedherbaceous layer includes grasses,legumes, and cacti.
Desert or arid grasslands comprise 20% of this desert and are often mosaics of shrubs and grasses. They include purple three-awn (Aristida purpurea), black grama (Bouteloua eriopoda), and sideoats grama (Bouteloua curtipendula). Early Spanish explorers reported encountering grasses that were "belly high to a horse"; most likely big alkali sacaton (Sporobolus wrightii) and tobosa (Pleuraphis mutica) along floodplain or bottomland areas.[4]
The United Nations Environment Programme reported in 2006 that nearly half of the bird, mammal, and butterfly species in the Chihuahuan Desert are expected to be replaced by other species by 2055 due to climate change.[9]
A 2017 assessment found that 35,905 km2 (13,863 sq mi), or 7%, of the ecoregion is in protected areas.[1] Protected areas includeBuenos Aires National Wildlife Refuge in Arizona;Janos Biosphere Reserve,Médanos de Samalayuca Natural Protected Area andCañón de Santa Elena Flora and Fauna Protection Area in Chihuahua;Cuatro Ciénegas Basin,Ocampo Flora and Fauna Protection Area, and part ofMaderas del Carmen Biosphere Reserve in Coahuila;Mapimí Biosphere Reserve andCañón de Fernández State Park in Durango;Bitter Lake National Wildlife Refuge,Bosque del Apache National Wildlife Refuge,Carlsbad Caverns National Park,Carrizozo Malpais,Oliver Lee Memorial State Park,Organ Mountains–Desert Peaks National Monument,Petroglyph National Monument,Sevilleta National Wildlife Refuge, andWhite Sands National Park in New Mexico; andBig Bend National Park,Big Bend Ranch State Park, Black Gap Wildlife Management Area,Franklin Mountains State Park, and part ofGuadalupe Mountains National Park in Texas.
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