Conservation of Rare, Sensitive, and At-risk Desert Plant Species

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The Mojave Desert is among the hottest and driest of the North American drylands, but in spite of these extreme conditions, and in part because of them, a diverse flora exists. This diversity of rare, endemic, and endangered species is threatened by the complex interaction between fluctuating climate and human-mediated disturbances. USGS studies have identified rare species “hotspots” for planning public multi-use access, evaluated the impact of vehicle-generated dust emissions on endangered plant physiology and growth, and identified salinity tolerance for an endangered inland marsh endemic. Explore this webpage to learn about current projects that provide essential guidance for informing management actions. 

Measuring Evening Primrose
Growth and reproduction of Eureka Dunes evening primrose are monitored on three dune areas in Eureka Valley, California(Credit: Lesley DeFalco, USGS WERC. Public domain.)

Ecology of two contrasting endangered dune endemics at Death Valley National Park

Eureka Dunes is an ecologically distinct environment that supports several rare, endemic and endangered species, including Eureka Dunes evening primrose (Oenothera californica ssp. eurekensis) and Eureka Valley dune grass (Swallenia alexandrae). Censuses reveal dramatic declines in populations of these two species since 1976 population surveys. Potential causes include reduction in recruitment and survival associated with variability in regional climate. The dune grass and evening primrose represent contrasting strategies for plant population persistence, which may lead to different abilities to cope with expected changes in climate or levels of visitor use on the dunes. Our study complements the existing NPS long-term monitoring efforts and focuses specifically on the climate-mediated mechanisms driving population change for the two species. An understanding of the demography of these two contrasting sand dune endemics with relation to changing climate and visitor use is critical for their current protection and for determining future population stability and management.

USGS WERC Ecologist Sara Scoles-Sciulla monitoring precip, temp, soil moisture
Project lead and Ecologist Sara Scoles-Sciulla monitors precipitation, air and soil temperature, and soil moisture fluctuations down to 5 m depth and within the root zone of the two endangered species(Credit: Lesley DeFalco, USGS WERC. Public domain.)

Demography of the Joshua tree across five Mojave Desert National Parks

Desert national parks are losing stands of the iconic Joshua tree (Yucca brevifolia) due to wildfires and drought-related animal damage that is altering the demographic structure of this endemic Mojave Desert species for future decades. USGS works with National Park Service, US Forest Service, and Department of Energy to study how environmental variability influences key processes in establishment including reproduction and seed dispersal, seed longevity and conditions for seedling emergence, and survival of pre-reproductive Joshua trees, all of which are being used to create demographic models for this long-lived desert icon to identify vulnerability of different life stages with current and future threats.

Wildfires that impacted Joshua trees in the national park
Wildfires such as the one that impacted Joshua trees in the national park that bears its name can have lasting effects on the demography of the species(Credit: Todd Esque, USGS WERC. Public domain.)