Taking the Mojave's Pulse: What Park Scientists Monitor as the Desert Changes

The Mojave and Great Basin deserts of Nevada, Arizona and California are a land of extremes — Joshua trees, fossil beds, dark night skies and a long human history. They are changing fast.

Long-term monitoring gives park managers the information to respond and to limit the loss of habitat.

The network

The Mojave Desert Network is one of the Park Service's 32 Inventory and Monitoring networks. It tracks "vital signs" — key resources that indicate the health of a park — in seven units: Death Valley, Great Basin and Joshua Tree national parks, Lake Mead National Recreation Area, Manzanar National Historic Site, Mojave National Preserve and Grand Canyon-Parashant National Monument. It hasn't monitored long enough to detect trends yet, but it is documenting current conditions.

Field scientists monitoring springs, upland vegetation, a lake level, tree diameter and bats. NPS

Water

Desert bighorn sheep at Lake Mead National Recreation Area depend on desert springs. NPS / Andrew Cattoir

Desert springs are water sources and hotspots of biodiversity — more than 75% of Mojave and Great Basin wildlife, from pupfish to bighorn sheep to migrating birds, depends on the vegetation of springs and streams. The network surveys 245 springs in five parks, recording whether water is present, its temperature, conductivity, pH and dissolved oxygen, flow and length, plus disturbance, wildlife use, vegetation, invasive plants and repeat photographs. Threats include heat, groundwater pumping, diversions, recreation, livestock and invasive species.

Springs in Joshua Tree National Park by wetness — dry soil, wet soil, or lengths of flowing water — in 2006, 2017, 2020 and 2023. NPS / Jennifer Bailard

In Joshua Tree, far more springs were dry, or had only wet soil, in 2017 — at the end of California's exceptional 2014–2017 drought — than in the wetter 2005–2006 inventory. As the climate warms, dry years are expected to become more common, broken by very wet years like 2023.

Sparrow Spring, Joshua Tree National Park, January 15, 2006: surface water present. NPS Photo

Sparrow Spring, February 8, 2017: no surface water. NPS Photo

Selected large springs get more intensive monitoring of water quantity, chemistry and benthic macroinvertebrates — bottom-dwelling insects, snails, crustaceans and worms, good indicators because they live in the water and vary in how much pollution they tolerate. Some springs shelter endemics: two species of springsnail live in a single spring at Lake Mead, and the endangered Mohave tui chub, once found only in the Mojave River basin, now survives in isolated ponds near its end. A separate project tracks spring vegetation and invasive plants.

Collecting macroinvertebrates in a spring in Death Valley National Park. NPS / Jenette Jurado

Streams and lakes. With park staff, the network monitors nine streams and six subalpine lakes in Great Basin National Park — data the park used to choose where to reintroduce its one native fish, the Bonneville cutthroat trout. Warmer air means more rain and less snow, smaller snowpack, less runoff, lower lakes, weaker streams and warmer water. The network tracks water quality and chemistry, macroinvertebrates (streams) and the ice-free season (lakes).

Measuring water clarity from a float tube, Great Basin National Park. NPS / Jennifer Bailard

Trees

A monitoring plot with a bristlecone pine, Great Basin National Park. NPS / Joseph Ladd

White pines — limber pine and Great Basin bristlecone pine, long-lived trees of high, harsh places — regulate snowmelt and streamflow, shade other plants and feed wildlife. Threats include mountain pine beetles, warming, and white pine blister rust, a disease caused by a non-native pathogen. By 2020 the first round of plots was done, with no blister rust found in Great Basin National Park. But beetles are a concern: drought weakens the pines' pitch defenses, and warmth lets beetles move higher. A study found beetle-killed bristlecones at two Great Basin sites, including Death Valley. In 2023 the network found beetle-damaged limber pine in two plots, though not yet in its bristlecones.

Dead limber and bristlecone pines (gray) near Telescope Peak, Death Valley National Park, discovered in 2018 — bristlecones had not previously been known to die from beetles. USFS / Constance Millar

Quaking aspen, North America's most widespread deciduous tree, faces Sudden Aspen Decline, which drought and heat seem to worsen, along with insects; aspen also needs fire to spread. It is monitored in Great Basin and Parashant.

Measuring aspen in a Great Basin National Park plot. NPS

Bats

In six parks, the network monitors 11 bat species in winter and 30 in summer — by listening acoustically, and by capturing bats to check for white-nose syndrome, a disease caused by a non-native fungus that has killed millions of bats elsewhere. Drought and drying springs are shrinking bats' habitat and drinking spots; wind energy is another threat.

Shrublands and Joshua trees

Setting up a plot in sagebrush, Great Basin National Park. NPS / Joseph Ladd

Upland vegetation — one shrub community per park, such as Joshua tree, creosote bush or sagebrush — conserves soil, stores carbon and houses wildlife. Heat and drought may push plants uphill, reshuffling communities; air quality, water use, fire, grazing, development and non-native plants add pressure.

Assessing Joshua trees in Joshua Tree National Park. NPS / Joseph Ladd

Joshua trees are losing habitat to heat, drought, fire and invasive grasses. The 2020 Dome Fire killed an estimated 1.3 million in Mojave National Preserve; the 2023 York Fire burned more than 100,000 acres in and around it. They will likely never return there in the same numbers, and large areas of Joshua tree and pinyon-juniper may turn to grass and fire-adapted shrubs — but replanting and monitoring may help them hold on in parts of their range.

Weather

The Nevershine weather station, Parashant National Monument. NPS

Weather and climate data from stations in the parks help explain changes in the other vital signs; partner Desert Research Institute offers a data tool for near-real-time graphs.

How it helps

• Early detection of disease or decline — white-nose syndrome, blister rust — makes responses more effective and cheaper.
• Priorities: knowing which springs hold water through droughts and which are most fragile tells managers where restoration pays off most.
• Collaboration: white pine, aspen and bat monitoring use the same methods across many parks and agencies, so managers can solve problems together.

More: the Mojave Desert Network.

Sources

Based on "Monitoring Vital Signs in Times of Rapid Change," by Jeri Stoller, Scientist-in-Parks communication intern, edited by Linda Mutch and Lise Grace, National Park Service; a work of the United States government in the public domain. The article draws on the Fourth National Climate Assessment and studies by Riddell and others (2021), Bentz and others (2022), Piccioli Cappelli and others (2021) and Barrows and Murphy-Mariscal (2012). Photographs credited to the California Highway Patrol, the Great Basin Institute and an intern are left out; rewritten in hubnx's own words.