Great Basin Desert

The Great Basin Desert is a temperate desert found in the western United States, lying between the Sierra Nevada and the Wasatch Range. It is one of North America's four biologically defined deserts, along with the Mojave, Sonoran, and Chihuahuan. The region is defined by basin and range topography: wide valleys flanked by parallel mountain ranges that generally run north to south. Over 33 peaks within the desert rise above 9,800 feet, while the valley floors themselves are high, typically above 3,900 feet in elevation. This desert covers much of Nevada and Utah, stretching into eastern California.

The desert's ecology shifts with altitude, moving from low, salty dry lakes up through rolling sagebrush valleys and into pinyon-juniper forests. The dramatic elevation changes between valleys and peaks create many distinct habitat niches, leading to small, isolated populations of genetically unique plants and animals. More than 600 vertebrate species live in the floristic Great Basin, which covers an area similar to the ecoregion. Of these, 63 species—such as the greater sage-grouse, kit fox, Ord's kangaroo rat, and desert horned lizard—are considered conservation concerns due to shrinking natural habitats.

Geography also shapes the desert's ecology. Its high elevation and position between mountain ranges drive the climate: the Sierra Nevada creates a rain shadow that blocks moisture from the Pacific, while the Rocky Mountains restrict moisture from the Gulf of Mexico. Precipitation varies across the desert depending on the strength of these shadows. The environment was also shaped by Pleistocene lakes—Lake Lahontan and Lake Bonneville—which dried up after the last ice age, leaving behind different levels of salinity and alkalinity.

The desert's boundaries are not sharply defined and depend on how scientists classify it. Some definitions rely on what is absent, such as J. Robert Macey's description of the "Great Basin scrub desert" as lacking creosote bush. This scrub desert includes several arid basins without *Larrea tridentata*, like the Chalfant, Hammil, Benton, and Queen valleys, and most of the Owens Valley except its southeast corner. In contrast, the Panamint, Saline, and Eureka valleys do have creosote bush, while Deep Springs Valley is part of the scrub desert. Ecoregion studies also help define the area. In 1987, J.M. Omernik mapped a desert ecoregion between the Sierra Nevada and Wasatch Range, calling it the "Northern Basin and Range." By 1999, the U.S. EPA had renamed this the "Central Basin and Range" and shifted the "Northern Basin and Range" label to a different area. The World Wildlife Fund adapted Omernik's ecoregions but removed a small high-altitude area containing Holocene refugia, renaming it the "Great Basin Shrub Steppe." Although the EPA refined the Central Basin and Range boundaries in 2003, USGS geographer Christopher Soulard's later reports used the 1999 boundary, which is essentially the same as the Great Basin Shrub Steppe. He notes that the Great Basin Desert is "encompassed within" that area. This article covers the general ecology of the region, including high-elevation areas, without focusing on minor differences in definitions.

The climate is extreme: hot, dry summers and cold, snowy winters, with frigid alpine ridges and warm, windy valleys. Days can exceed 90 °F, followed by nights near 40 °F. The Sierra Nevada, rising 14,000 feet, casts a strong rain shadow over the desert. Pacific weather systems lose most of their moisture as they are forced up and over the mountains, leaving little for the desert. This effect is strongest near the Sierra, with average yearly precipitation around 9 inches in the west and 12 inches in the east. Most moisture that does arrive falls as rain or snow at higher elevations, primarily over the long, parallel mountain ranges. Any precipitation that falls in the desert does not drain to the Atlantic or Pacific; instead, it flows to ephemeral or saline lakes, evaporates, or soaks into the soil. The Great Basin Desert is the coldest of North America's deserts. Weather varies widely from day to day due to the mountainous terrain, with temperatures depending heavily on elevation.