Drought

Dryland regions have been degraded by invasive species, wildfire, overgrazing, agricultural conversion, energy development, recreational activity, and urban growth. These disturbances and others are accelerated by one of the fastest growing human populations in the country and a pressing background of decreasing water availability due to drought and elevated temperatures that are projected to...

In the southwest US, monsoon precipitation increases sharply along a northwest to southeast gradient. Pleuraphis jamesii or galleta grass, is an important C4 grass species that spans across this large range in precipitation pattern. In this study we are assessing the ability of galleta grass to adapt to changes in the seasonality of rainfall (termed “plasticity”). In the fall of 2014, we...

Forests in the semiarid southwestern U.S. are expected to be highly vulnerable to increasing aridity anticipated with climate change. In particular, low elevation forests and the processes of tree regeneration and mortality are likely to be highly susceptible to climate change. This work seeks to characterize how, where and when forest ecosystems will change and identify management strategies to...

Drylands cover 40% of the global terrestrial surface and provide important ecosystem services. However, climate forecasts in most dryland regions, especially the southwest U.S., call for increasing aridity. Specifically, changing climate will alter soil water availability, which exerts dominant control over ecosystem structure and function in water-limited, dryland ecosystems. This research seeks...

Historic over-grazing of arid grasslands in the Intermountain West has led to widespread soil erosion, loss of plant diversity, and invasion by exotic species. Degraded grassland conditions can be very persistent, even after livestock use has ceased. For example, in national parks on the Colorado Plateau, livestock have been excluded for decades, but soil and native plants have not recovered on...

Land managers face tremendous challenges in the future as drought and climate change alter the abundance, distribution, and interactions of plant species. These challenges will be especially daunting in the southwestern US, which is already experiencing elevated temperatures and prolonged droughts, resulting in reduced soil moisture in an already water-limited environment. These changes will...

Dust emission caused by wind erosion has received considerable attention because of its far-reaching effects on ecosystems, including the loss of nutrients and water-holding capacity from source areas, changes to climate and global energy balance in areas where dust is entrained in the atmosphere, fertilization of terrestrial and marine ecosystems, in addition to decreases in snow albedo, causing...

Floodplain red gum forests are sites of high biodiversity in arid regions of south Australia. They depend on periodic floods from rivers, but dams and diversions have reduced flood frequencies, leading to deterioration of the trees. We determined the water requirements of red gum trees so environmental flows can be used to restore and maintain the forests. We used measurements of transpiration of...

The Restoration Assessment and Monitoring Program for the Southwest (RAMPS) seeks to assist U.S. Department of the Interior (DOI) and other land management agencies in developing successful techniques for improving land condition in dryland ecosystems of the southwestern United States. Invasion by non-native species, wildfire, drought, and other disturbances are growing rapidly in extent and...

Turtles are among the most recognizable and iconic of animals. Any animal with a shell and a backbone is a turtle whether they are called turtles, tortoises, or terrapins. In fact, terrapin is an Algonquian Native American name for turtle. Worldwide there are 356 turtle species on all continents except for Antarctica. The United States has more species than any other country with about 62...

Big sagebrush ecosystems are a major component of landscapes in the western U.S. and provide vital habitat to a wide array of wildlife species. However, big sagebrush ecosystems have been dramatically impacted by disturbances in the past several decades. This collaborative research between USGS and the University of Wyoming focuses on understanding how climatic and soil conditions influence big...

Agassiz’s desert tortoises ( Gopherus agassizii ) approach the southern edge of their mostly Mojave Desert range near Joshua Tree National Park. Modern desert tortoise research started in the Park in 1978 when the first tortoise population census was conducted on a one square mile area in the Pinto Basin known as the “Barrow Plot.” U.S. Geological Survey research began at the plot in 1997 and...