Geologic Framework for Ecosystem Structure and Function
The Study of Desert Ecosystems
USGS scientists in the Earth Surface Dynamics program have been working to understand arid-land surface dynamics in the southwestern U.S. The researchers involved in this effort are studying landscape recoverability and vulnerability, geologic processes (such as weathering, erosion, and deposition), the influence of biotic processes, and the effects of climate variability, climate change, and human activities on these processes. One of the major goals is to interact with Federal, State, and local government agencies to address issues such as grazing, off-road vehicle use, mining, fire, waste disposal, species management, flood hazards, water erosion, invasive species such as cheat grass, dust-storm prediction, and dust-transport effects.
A map of the Southwestern United States with an outlined area of the Colorado Plateau and the Mojave Desert - two focus areas for USGS climate change and land use research.
The Mojave Desert Ecosystem encompasses six military bases, four national park units, and considerable BLM lands, as well as land managed by other Federal agencies. The desert is also home to active and abandoned mines, off-road recreation areas, and waste disposal sites. Land managers, organized in several formal groups, are asking for unbiased scientific input to help them balance competing demands, from locating utility corridors and waste disposal sites to managing habitat for endangered species.
A map depicting the complexity of the Mojave Desert Ecosystem.
An image of the Mojave Desert.
The BLM has set up a number of special habitats or Areas of Critical Environmental Concern (ACECs) for the desert tortoise, which is designated as a threatened and endangered species. USGS is conducting detailed mapping in plots established for monitoring the desert tortoise and other threatened vegetation. Surficial geologic maps are extremely powerful for preparing spatial GIS models for the ecosystem. These plots, which have extensive biologic field data, when combined with the geologic maps of the surface materials, provide a spatial database for modeling diverse ecological and management issues, from vegetation and animal populations to vulnerability to soil compaction and recovery of vegetation from soil compaction.
A visitor to the Mojave Desert riding an OHV.
The BLM recognizes that recreation is a major component within the Mojave Desert and has designated portions of the area for the use of off-highway recreational vehicles (OHVs). The USGS has developed an interagency agreement with the BLM to conduct surficial geologic mapping in desert OHV areas to help with managing the lands and monitoring changes.
Studies of the Mojave Desert by USGS scientists include earthquake monitoring and hazard assessment, evaluating minerals resources, and gathering baseline geophysical and geologic data. One of the activities directed toward ecosystem studies includes integrated studies of wind erosion, dust-storm prediction, vegetation change, desert soils, and ecosystem function.
Using a combination of ground-based geologic and biologic studies, remote sensing techniques, and weather monitoring, USGS scientists are developing new methods to:
- detect and track dust events from satellite and remote camera images,
- distinguish between mineral-dust haze and industrial/urban pollution,
- determine soil conditions leading to wind erosion and dust emission,
- detect Aeolian dust in soils and estimate past rates of deposition,
- characterize modern dust and calculate current rates of dust emission and deposition in ecologically sensitive areas,
- evaluate the roles of Aeolian dust in ecosystem function, including possible effects on exotic-species invasion, especially conditions of Cheatgrass invasion
- evaluate how wind erosion might affect human health, including the spread of infectious disease, such as Coccidiodomycosis (Valley Fever)
- model future dust emission and transport.
To capture various sized dust storms and document some of the sources and transport patterns, USGS researchers are using digital cameras in the field that are set up as stand-alone stations. The cameras are triggered automatically to collect digital photographs when the winds exceed a selected threshold.
A USGS digital camera station in the Mojave Desert.
A dust storm event captured by one of the USGS's digital camera stations.
Studies in the Mojave Desert aim to understand the processes responsible for initiation of Aeolian (wind-borne) sand movement, including controls from source-sediment availability, climate, vegetation, and land use. Sand movement, because of future climate change or land-use practices, could have serious consequences on human and animal populations, agriculture, grazing, and infrastructure.
