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April 11, 2022

Increasing summertime temperatures in the deserts of the southwest United States may be making it harder for lichens, an important member of the soil community, to survive.

Biocrust study site
Scientists surveying biocrust at a protected study site. Photo courtesy of USGS, Sept 2019.

Lichens, along with bacteria and moss, form a biological soil crust that acts as a protective barrier for desert ecosystems, helping prevent erosion, creating a nutrient-rich growing environment and increasing water retention.

Biocrust
Photo of biocrust taken at Birds of Prey NRCA near Boise, Idaho. 

The study, published today in the Proceedings of the National Academy of Sciences, examined the effects of a changing climate by exploring 24 years of continuous biological soil crust survey data. Trends in the data suggest an increasingly inhospitable growing environment for native organisms. The research was completed in a protected area of Canyonlands National Park in Utah that has never been grazed, removing the possibility that plant and soil life were previously destroyed by physical disturbance. The data collected was continuous from 1996-2020.

“This study is an early indicator that desert soil crusts may indeed be at a tipping point, losing their ability to protect against soil erosion and other benefits,” said Rebecca Finger-Higgens, U.S. Geological Survey research ecologist and lead author of the study. “This work supports the importance of continued research.”

Desert soils in the Colorado Plateau form biological soil crusts which help make life for various plant and animal species possible in these harsh environments. Soil crust lichens play an especially important role as they help fertilize the soil through nitrogen fixation, a process that converts nitrogen from the atmosphere into the soil for the benefit of plant life. However, climate change could cause a fundamental shift in these fragile dryland soil communities, leading to declines in biodiversity with a direct impact on a variety of plant and animal species found in the southwest United States.

For instance, in many dryland systems, when biological soil crusts are destroyed, these areas become much more prone to erosion, which can contribute to dangerous dust storms and mudslides. Additionally, disturbed sites and areas lacking stable soils can be more prone to the spread and proliferation of weedy, non-native, and even noxious plants which can outcompete and replace existing native vegetation and potentially be harmful to animals if consumed.

“Biocrusts are found worldwide in the earth’s dryland areas and few long-term observations of these fragile environments exist,” said Scott VanderKooi, Director of the USGS’s Southwest Biological Science Center. “The USGS and our partners continue to prioritize research around biocrust restoration to provide data for sound land-management decisions.” 

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