Mojave Desert ecosystem

• Category: Desert Biomes.
• Geographic Location: North America.
• Summary: As California’s largest desert, the Mojave is a scenic and biologically diverse ecoregion, threatened by urbanization.

The Mojave Desert landscape offers many dramatic geologic features, including peaks, dry washes, salt pans, cliffs, canyons, sand dunes, and alluvial fans. It is richly diverse in plant and animal species that have adapted to its extreme climate. The continued development of cities in southern California and Nevada in the twentieth and twenty-first centuries has had a significant effect on the ecology of the region. As a result, the US Bureau of Land Management, National Park Service, and other public agencies have moved to protect its biological diversity and to ensure sustainability of this uniquely scenic region.

Transitional Desert

The natural boundaries that define the wedge-shaped Mojave Desert can easily be identified in satellite photographs and on topographical maps. The Mojave is considered to be a transitional desert, lying between the cooler Great Basin Desert to the north and the hot Sonoran Desert to the south. To the east, the Mojave Desert stretches across four states: California, Nevada, Arizona, and Utah. On the west, it is bordered by the intersection of two major fault systems: the Garlock at the northern edge of the San Gabriel Mountains, and the San Andreas at the southern boundary of the Sierra Nevada range.

Known for its distinctive typography, the Mojave is part of a geologic area known as Basin and Range Province, caused by an expansion of the Earth’s crust 5 million to 23 million years ago. The result was a series of parallel mountain ranges punctuated by broad, flat valleys. At the point where the mountains and valleys meet, alluvial fans spread like giant feet onto the floor of the desert. Phreatophyte plants (those with deep roots constantly in touch with water) such as the creosote bush often grow here, extending their roots to water 50 feet (15 meters) or more below the surface.

Climate

The Mojave Desert rests in the rain shadow of three mountain ranges: the southern Sierra Nevada, and California’s Transverse and Peninsular ranges. It receives less than 13 inches (330 millimeters) of precipitation a year, most of it during the winter months and often in the form of snow, with an occasional summer thunderstorm. Most winters see less than 3 inches (76 millimeters) of rain; prevailing winds from the Pacific Ocean drop most of their moisture in the mountains; the rest often evaporates before ever hitting the desert floor.

Though its elevation generally ranges from 2,000 to 5,000 feet (610 to 1,524 meters), the Mojave Desert is guarded by the towering Telescope Peak in the Panamint Range, which features one of the steepest vertical ascents of any mountain in the contiguous United States. The peak rises 11,331 feet (3,454 meters) above the lowest point in North America, Badwater Basin in Death Valley, at 282 feet (86 meters) below sea level. Death Valley broke the record for the highest temperature ever recorded in the Western Hemisphere when Furnace Creek reported 134 degrees F (57 degrees C) on July 10, 1913.

In August 2020, what later became known as the Dome Fire burned more than 43,000 acres of Joshua Tree woodland near the Cima Dome in the eastern Mojave Desert. Following the fire, the National Park Service reported that an estimated 1.3 million Joshua trees were damaged or lost in the Dome Fire. Then, in July 2023, the York Fire, a wildfire that began on private land in the New York Mountains within the Mojave National Preserve in San Bernardino County, California, grew to more than 90,000 acres spread across both California and Nevada.

Biodiversity

With such extremes of elevation and temperature, it is not surprising that there is notable biological diversity among the plant and animal populations of the Mojave Desert. Telescope Peak, for example, supports a variety of trees, including single-leaf pinyon; limber pine; and, at the highest elevations, bristlecone pine (Pinus longaeva), believed to be one of the oldest living species on Earth. By contrast, Badwater Basin, onces an ancient lake, features a pool of brackish water that looks as though it could not support life at all. The pool is undrinkable by humans, leaching toxic salts from the surrounding area, but it does not deter pickleweed, aquatic insects, and badwater snails from thriving.

The climate of the Mojave Desert varies from west to east. The western desert is more typical of California’s mediterranean climate—with hot, dry summers and cool, wet winters—while the eastern Mojave has a more balanced pattern of summer and winter moisture. Utah agave, Spanish bayonet, Mojave yucca, and grasses such as galleta are found more often in the east, where summer rain falls, while winter flowers like desert coreopsis, goldfields, and California poppy are found in the western portion of the desert during the wet winter season. The Mojave’s dune systems also support unique plant and animal species such as Eureka dune grass and the Mojave fringe-toed lizard.

Some animals living in the Mojave have developed physical attributes that allow them to survive in the extreme desert climate. The Mojave ground squirrel and jackrabbit have light-colored coats that reflect the heat. The multicolored coat of the coyote allows it to stalk prey among rocks and in sandy washes. The venomous Mojave green rattlesnake has a neurotoxin that is considered to be ten times as strong as that of other North American rattlesnakes, allowing it to hunt quickly and efficiently. Most desert animals hunt or forage for food at dawn or after the sun goes down.

The desert tortoise has a domed brown shell that can easily be mistaken for a rock. It burrows 3 to 6 feet (1 to 2 meters) deep in the desert soil to escape the heat, and can live for years without water. Desert tortoises living in the Mojave Desert are federally listed as a threatened species. They are vulnerable to illegal collection by humans and to habitat disruption from urban expansion. Ravens have played a unique role in the dilemma of the desert tortoise. Ravens are both predators and scavengers. They love human trash, and at the same time, they prey on young tortoises, whose tender shells have not hardened. Attracted in artificially high numbers to areas where human activity has spiked, the ravens then turn on the young tortoises that are seeking new shelter. The human-raven-tortoise relationship provides a good example of how human activities can disrupt ecological balance.

Effects of Human Activity

The Mojave Indigenous peoples here centered their activities on the Colorado River, using its annual overflow to grow melon, corn, pumpkin, and bean crops. They used nets made from grasses to catch fish, and gathered seeds and pods to supplement their diet. The Chemehuevi, Cahuilla, and Serrano were Indigenous tribes who lived in this subsistence manner in and around the Mojave Desert.

During the Gold Rush period of 1848–54, it is estimated that more than 250,000 people crossed the Mojave to find their fortunes in the mountains and cities of California. The effect on desert ecosystems was minimal until the rapid urban expansion of Las Vegas, Nevada, and Lancaster and Barstow, California, more than a century later. Between 1990 and 2000, for example, Las Vegas showed an increase of more than 710,000 people.

As early as the 1970s, public and private agencies recognized the need to protect desert lands, but it was not until 1994 that Congress passed the California Desert Protection Act, designating large areas of the Mojave Desert as wilderness. About 80 percent of the Mojave in California became managed by federal agencies—not all of them focused on conservation. The Bureau of Land Management is the largest land manager of the region, overseeing 8 million acres (3 million hectares) of land. The National Park Service manages the Death Valley and Joshua Tree national parks, as well as the Mojave National Preserve. The Department of Defense manages several military bases throughout the region. State parks and fish and game agencies manage portions as well.

Even with extensive management, Mojave Desert plants and wildlife are still at risk. Urban sprawl, off-highway vehicle activity, overuse of water resources, and overgrazing of cattle and sheep have caused continued problems. In 2022, a 3,000-acre (1,214-hectare) solar farm threatened the desert's ecosystem. While the construction of the solar farm was intended to help combat climate change by reducing the need for fossil fuels, it entailed the destruction of more than 100,000 yucca plants. In preparation for the destruction, scientists in 2021 relocated more than 100 federally protected desert tortoises. Environmentalists contend that only with continued commitment and strategic conservation efforts will the extraordinary Mojave Desert ecoregion be restored, protected, and preserved for future generations.

Climate change as a result of human activity remains a threat in the Mojave Desert. Changes in weather patterns and an increased threat of fire due to unstable conditions plagues the region. The National Park Services reports that the Mojave receives 20 percent less precipitation now than in the early 20th century. For birds, this water shortage is making the area uninhabitable. Birds are pollinators, scavengers, and seed distributors, making a decline in their populations a threat to the region as a whole.

Bibliography

Abella, Scott R. “Disturbance and Plant Succession in the Mojave and Sonoran Deserts of the American Southwest.” International Journal of Environmental Research and Public Health, vol. 7, no. 4, 2010.

Aitchison, Stewart. Death Valley National Park: Splendid Desolation. ierra Press, 2002.

Bakker, Elna. An Island Called California: An Ecological Introduction to Its Natural Communities. U of California P, 1971.

Bernhard, Meg. "'Is This Really Green?' The Fight over Solar Farms in the Mojave Desert." The Los Angeles Times, 3 Nov. 2021, www.latimes.com/world-nation/story/2021-11-03/the-mojave-desert-is-prime-real-estate-for-solar-power. Accessed 7 Oct. 2024.

"Dome Fire." National Park Service, 14 Aug. 2023, www.nps.gov/moja/learn/nature/dome-fire.htm. Accessed 7 Oct. 2024.

Nevada Fish and Wildlife Office. “Threats to Desert Tortoises.” U.S. Fish and Wildlife Service. . Accessed 7 Oct. 2024.

Parker, Sophie S., et. al. "Conservation of the Mojave Desert Springs and Associated Biota: Status, Threats, and Policy Opportunities." Biodiversity and Conservation, vol. 30, pp. 311-27, 5 Dec. 2020, doi.org/10.1007/s10531-020-02090-7. Accessed 7 Oct. 2024.

Riddell, Eric A et al. “Cooling Requirements Fueled the Collapse of a Desert Bird Community From Climate Change.” Proceedings of the National Academy of Sciences of the United States of America, vol. 116, no. 43, 2019, pp. 21609-15, doi:10.1073/pnas.1908791116.

Schoenherr, Allan A. A Natural History of California. U of California P, 1992.

"2023 - York Fire." InciWeb, National Wildfire Coordinating Group, inciweb.nwcg.gov/incident-information/camnp-2023-york-fire. Accessed 7 Oct. 2024.