Rain-shadow ranges may hide Earth's most diverse desert
WWF ranks the Chihuahuan Desert among the world's most biologically diverse arid lands by species richness and endemism. Sierra Madre walls steal Pacific and Gulf moisture, leaving a high plateau of creosote flats, sky-island forests, and overgrazed grasslands from Mexico deep into Texas and New Mexico.
The ecoregion blankets arid north-central Mexico and reaches into western Texas, southern New Mexico, and a corner of Arizona along the Rio Grande and Pecos drainages. Westward it meets the Sonoran Desert, Colorado Plateau, and Sierra Madre Occidental; eastern and northwestern Sierra Madre Oriental flanks also bound it. Biggest continuous tracts lie in Mexico. Mountain "sky islands"—Organ, Franklin, Sacramento, Chisos, Guadalupe, Davis, Sierra del Carmen—lift cooler woodlands above desert floors.
Ciudad Juárez approaches two million people; Chihuahua, Saltillo, Torreón, El Paso, Albuquerque, Las Cruces and many smaller towns punctuate the dryness. Elevations mostly run 480–1,800 metres, yielding slightly milder summers than the lower Sonoran yet June days still often 32–40 °C, with winter freezes common. Mean yearly rain is about 235 millimetres (range roughly 150–400), mostly in the late-summer North American Monsoon, with a lesser early-winter pulse. Creosote bush dominates many valley soils; yuccas, Opuntia, mesquite, and lechuguilla structure uplands.
Grazing and urban pressure have pushed woody natives over former grass cover; the Mexican wolf, once common, remains endangered after near extinction. Desert willow, honey mesquite, and cottonwoods line arroyos and floodplains where water concentrates. Compared with many warm deserts the Chihuahuan is relatively wet—yet still arid enough that trees stay scarce outside drainages. A 2017 assessment counted about 7 percent of the ecoregion, 35,905 square kilometres, inside protected areas, and a 2006 UN Environment Programme report expected nearly half of its bird, mammal and butterfly species to be replaced by others by 2055 as the climate warms.
Source: Chihuahuan Desert
