The rapid rise of temperatures across the western United States poses a threat to snow-adapted plants and animals living there, but a key question has not been well resolved by climate models: How long — and where — will mountain snows remain? 

A new, fine-scale modeling approach developed by NOAA and CIRES scientists now projects that there will still be enough high-elevation snow by the middle of the 21st Century to support — according to federal biologists — the denning habits of one iconic North American mountain-dweller, the wolverine. 

Results of the study were published today in the journal Earth’s Future.

The research was done between 2015 and 2019 at the request of the U.S. Fish and Wildlife Service (FWS), which is expected to issue a determination soon on whether wolverine in the lower 48 states deserve protection under the Endangered Species Act.

The study evaluated the future persistence of springtime snowpack at elevations of observed and potential denning for two study areas in the Rocky Mountains, Glacier National Park in Montana, and Rocky Mountain National Park in Colorado. It’s the first detailed projection of the strong influence exerted by elevation and topography on the depth and duration of snow through the spring months in the Rocky Mountain region.

Lead author Joe Barsugli, a CIRES scientist working with a team of colleagues at NOAA, said their findings indicate lack of snow at high elevations won’t likely be an impediment to wolverine conservation. 

“There’s been remarkably little work evaluating future snow persistence on north-facing versus south-facing slopes,” he said. “We’ve been able to develop more realistic snow projections than previous generations of models at a resolution that has applications for conservation planning.”  

Wolverine are large members of the weasel family which, in the lower 48 states, occupy huge territories of the most rugged mountainous terrain in very low densities, making it difficult to accurately estimate population size. Opportunistic carnivores and scavengers, they have a reputation for formidable strength, cunning and ferocity. Typically, breeding females will den in snow banks in late winter and spring. Like other large carnivores, the species was nearly eliminated from the contiguous US in the early 20th century, but has reoccupied some of its former range.

In 2014, the FWS determined that endangered species protections for the wolverine were not warranted, but a federal judge in Montana overturned the decision and remanded it back to the agency for additional evaluation of the likely persistence of springtime snowpack in the Rockies. FWS scientists then contacted researchers in NOAA’s Physical Sciences Laboratory to develop improved snow persistence projections for their species status assessment.

To produce their assessment, the scientists--including CIRES and CU Boulder scientists Ben Livneh, Aaron Heldmeyer, Candida Dewes, and Imtiaz Rangwala--used existing climate projections and applied sophisticated hydrology models at a 250-meter grid resolution, which represents much finer resolution and greater detail than in any previous assessment. They selected Glacier National Park in Montana, which currently hosts denning wolverine, and Rocky Mountain National Park in Colorado, which was recently occupied by wolverine, as proxies for how snow will respond to warming temperatures across the vast landscape of the Rocky Mountains. 

The researchers found that large declines are projected for the lower half of wolverine denning elevations. They also found that snowpack between 20 and 40 inches deep or greater, thresholds identified by federal biologists, is likely to persist into April and May through mid-century on north- and east-facing slopes in the upper half of current denning elevations in all but the warmest of five future climate scenarios.

NOAA scientist and co-author Andrea Ray said the team enjoyed working closely with wildlife biologists to design a study that would provide information most relevant for understanding future habitat conditions. She said that the high-resolution projections would allow wildlife biologists to use Geographic Information System frameworks to identify areas where snow conditions needed by wolverine would be expected to persist. 

“When you think about the complex topography of a mountain landscape, you quickly realize you can’t answer this by modeling average snow depth across large areas,” Ray said. “You’ve got to think about which parts of this rumpled landscape will hold enough snow long enough in spring to be suitable for wolverine dens.”  

The scientists said that this technique could be applied to other hydrologic questions as well. 

“This work advances the science of high-elevation snow,” Ray said. “Understanding snow futures will be relevant for other snow-adapted species, and potentially for answering questions about future water supply.”

This story was written by NOAA Communications.