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© Jason Mohap

Mojave

Threats to Mojave

The many ways we use federally-managed land, as well as how we address resource conservation on adjacent private land, are the greatest threats to North America’s smallest desert.

Past uses of federally-managed lands on the Mojave Desert, including livestock grazing, mining, off-road vehicle use and military training exercises, have resulted in extensive wildlife habitat loss, degradation and fragmentation. On adjacent private lands, roadway construction, residential and agricultural development, water conveyance, flood control, livestock grazing as well as recreational use, have similarly resulted in wildlife habitat loss, degradation and fragmentation, as well as severe disruption of several desert ecosystems.

These impacts have not only lowered the resilience of many habitats to the continued impact of certain stressors, but have acted in a cumulative fashion to imperil several plant and animal species. The anticipated additional impacts associated with climate change, water use in a desert environment, continued human community growth, the spread of invasive species, increased wildfire occurrence, provisioning of scavengers and expanded renewable energy development have a strong potential to irreversibly harm the Mojave Desert’s flora and fauna.

Impacts to certain key species of the Mojave Desert, including many indicators of ecological health, have been well documented.  Plummeting populations of the threatened Agassiz’s desert tortoise and Mohave ground squirrel reflect deteriorating conditions of the most abundant desert plant community types; with little true recovery implementation accomplished to date. Yet expanded recreation and allowed uses which impact natural resources continue to be authorized.

The plight of the endangered Mojave tui chub and arroyo toad, both of which have largely been extirpated from their native Mojave River range, also indicate fundamental ecosystem disruption relative to water use and management. Similarly, several sensitive plant and wildlife species associated with desert springs, playas, moving sand and limestone-carbonate soils continue to be impacted by a variety of resource extraction and human use impacts. In addition, our extensive infrastructure of highways, railroads, aqueducts, transmission lines, pipelines, cities, towns and renewable energy development are increasingly fragmenting shrinking habitat linkages required by wide-ranging species such as American badgerpronghornmountain lionringtail and desert bighorn sheep.

Renewable Energy Development

BLM and individual county planning departments have authorized extensive large-scale wind and solar energy projects on a project-by-project basis throughout the Mojave Desert in the past decade. The cumulative impact of approved projects has already resulted in the elimination of approximately 50,000 acres of Agassiz’s desert tortoise habitat, largely in California.

Continued renewable energy development has a high potential to eliminate hundreds of thousands of acres of occupied and/or suitable Agassiz’s desert tortoise and Mohave ground squirrel habitat over the next several years. Unfortunately, considerable habitat supporting a number of imperiled wildlife species, have been specifically identified as renewable energy development focus areas. Fifteen renewable energy project applications have been filed with BLM in the California portion of the Mojave Desert; with an additional 20 applications filed in Nevada.

Dune systems and sand-transport corridors that support the Mohave fringe-toed lizard, as well as crucial migratory bird flight corridors, are also increasingly being impacted by solar energy development. Further, golden eaglesprairie falcons, burrowing owls, pallid bats and Townsend’s big-eared bats are being killed by both solar tower and wind energy generation facilities. While renewable energy projects can be built in a variety of places that minimize impacts to wildlife, sadly, this has not been the case with many renewable energy projects in the Mojave Desert.

Military Training

One of the largest land ownerships in the Mojave Desert is managed by the United States Military, with seven military installations (i.e., China Lake Naval Air Weapon Station [NAWS], Edwards Air Force Base [AFB], Fort Irwin National Training Center, Twentynine Palms Marine Corps Air Ground Combat Center [MCAGCC], NEBO Logistics Base, Nellis AFB, and Yermo Annex) situated throughout the Mojave Desert. One additional installation, George AFB, has been closed and renovated to support the commercial Southern California Logistics Air Base.

The congressionally-authorized expansion of the United States Army’s Fort Irwin National Training Center in 2001 constituted a significantly adverse impact on the Mojave Desert. This expansion of a national tank maneuver training ground onto public lands supporting high-density Agassiz’s desert tortoise and Mohave ground squirrel populations resulted in substantial critical habitat loss. Over 600 tortoises were also captured/translocated to lands outside active maneuver areas; with over half of these translocated tortoises subsequently perishing.

Additionally, the 2014 United States Defense Bill designated approximately 79,000 acres of primarily public lands for exclusive use by the Marine Corps adjacent to the MCAGCC, and 53,000 additional, adjacent acres shared between public use and the Marines. This expanded military training use occurs in a public land area formerly designated as the Johnson Valley Off-highway Vehicle Area; with a considerable amount of displaced use adversely affecting nearby critical habitat designated for  Agassiz’s desert tortoise. Approximately 1,100 tortoises were captured/translocated in this expansion area to lands outside of active maneuver areas; with survival rates currently unknown.      

These military base expansions were followed by the National Defense Authorization Act (2016), which resulted in a public land withdrawal of 26,479 acres to support military training/testing at the China Lake NAWS. Much of these withdrawn lands include a former conservation area designated for Agassiz’s desert tortoise and Mohave ground squirrel.

Off-road Vehicle Use

ORV use adversely impacts a number of imperiled wildlife species in a multitude of ways. Direct effects include running over individual animals and collapsing burrows sheltering animals; a reduction of spring annual plant forage; and removal of shrubs which provide cover habitat. Indirect ORV effects include disturbance of soils, extensive erosion and the destruction of shrubs. In the extremely arid Mojave Desert, the loss of appropriate shrub cover and sub-surface burrows can mean a removal of the only areas to escape heat and predators. The roads and trails created by such use also serve as dispersal corridors for non-native plants that often replace native vegetation; are frequently less nutritious than native plant species for our native wildlife; and commonly increase wildfire fuel loading, which can in turn increase subsequent wildfire frequency.

Ten ORV recreational use areas have been designated on public lands in the Mojave Desert-constituting over 500 km² of public land-with even more recreational vehicle use areas located to the south in the Colorado Desert portion of southern California. Additional recreational vehicle use areas have been designated on state and private lands in California. Extensive lawful vehicle routes have been designated on public lands which link these high recreational use areas. Even more unauthorized routes have been created on encompassed private lands.

Significant ORV impacts on natural resources within the Mojave Desert have been documented in use and limited use areas. Both the BLM and local communities have found enforcing recreational vehicle use rules on private and public lands next to impossible. In spite of this recreational management issue, the BLM in 2014 proposed a doubling of authorized recreational vehicle use routes in the western Mojave Desert; to total 10,428 miles outside of designated recreational use areas.  

Livestock Grazing

A number of domestic sheep and cattle livestock allotments have been designated throughout the Mojave Desert. This use has resulted in varying levels of soil and vegetation degradation/loss and adversely impacted a variety of wildlife habitats. Particularly hard-hit by this extractive use have been lands supporting wildlife waters and streamside vegetation, as well as rangelands supporting Agassiz’s desert tortoise and Mohave ground squirrel.

Cattle watering has posed additional impacts. Many artificially-created livestock trough waters have been found to provision common ravens and other human-subsidized wildlife, which can in turn prey on Agassiz’s desert tortoise. Some  artificial waters have even entrapped and killed animals.

These developed livestock waters, which generally result in elimination of native spring wetlands,  potentially also form a domestic animal-wildlife disease transmission pathway that could impact a variety of wildlife. In several instances where cattle have been removed from Mojave Desert lands, native plant communities have been observed to regain their former vigor and remnant desert bighorn sheep herds have been documented to expand dramatically.