Warmer temperatures, more extreme droughts and wet years will directly impact the abundance of plants on rangelands, alter the mix of plant species found there and change plant species’ geographic boundaries, say Utah State University ecologists. All this will, in turn, impact soils and the animals that rely on rangeland habitat.

Peter Adler, associate professor in USU’s Department of Wildland Resources and Ecology Center, and his colleagues are working to understand how historical climate variations have altered plant communities and how that information may help forecast future changes. In addition, he and Quinney Fellow Aldo Compagnoni, a doctoral student in plant ecology, are looking specifically at how changing climate may give an advantage to cheatgrass — a persistent, invasive weed that is already overrunning the American West.

“Ecosystems are difficult to predict,” says Adler, a 2011 recipient of a Faculty Early Career Development “CAREER” Award from the National Science Foundation. “Even if climate scientists could tell us exactly how precipitation and temperature will change, we still have lots of hard questions about the ecological responses. There will always be a gap between what scientists can provide and what managers need.”

In research published in a recent issue of the journal Ecology, Adler and his colleagues found changes in the amount, timing and type of precipitation (snow vs. rain), as well as temperature, impact dominant plant species in sagebrush steppe ecosystems. Those changes in the plant community imply changes in forage available for wild and domestic grazing animals, prompting new management approaches.

Agencies and land managers are accustomed to plans — those that regulate grazing allotments, for example — that are consistent from year to year.

"They may use a conservative stocking rate and just leave it in place,” Adler says. “But with more variable precipitation expected, we need to ask, ‘How do you take advantage of good years and survive the bad years?’ and that may require a more dynamic response.”

Among the many factors land managers must consider is Utah and surrounding areas will experience a growing percentage of precipitation falling as rain and less as snow. The past several years of climate data already show a steady increase in rain and decrease in snowpack.