As Glaciers Retreat, Mountain Biodiversity Persists

New study reveals specialized community of climate-adapted species in Glacier National Park’s high country

By Tristan Scott
Meltwater Lednian Stonefly larva. Courtesy USGS

As Glacier National Park’s namesake ice masses retreat, mirroring recessions occurring worldwide as a result of climate change, a suite of species occupying a rarefied alpine habitat appears to be persisting.

Scientists with the U.S. Geological Survey based in the northern Rockies have delivered these findings to the world through a study published May 18 in the Proceedings of the National Academy of Sciences, the world’s most cited and prestigious compendium of scientific research journals.

The study confronts predictions that widespread glacial recession will correspond directly with a reduction in biodiversity in mountain ecosystems through the loss of species that live in habitats influenced by glacier meltwater.

However, the new study shows that a specialized community of cold-water stream insects has unexpectedly persisted in the high-elevation streams of Glacier National Park, even in areas de-glaciated since the end of the Little Ice Age, nearly 170 years ago.

“Although the shrinking of glaciers poses a significant risk to species living in glacier meltwater, our results show these mountaintop species may be more resilient to glacier recession than previously thought,” Clint Muhlfeld, the study’s lead author and USGS research ecologist at Glacier National Park’s North Rocky Mountain Science Center.

“These habitat mosaics support diverse biological communities,” the study notes, focusing on two stoneflies that were recently listed under the federal Endangered Species Act (ESA) — Lednia tumana and Zapada glacier. These insects are confined to the highest reaches of aquatic alpine habitat, and are considered a “canary in the coal mine” for climate-induced biodiversity loss in mountain ecosystems.

The study was the first to examine how recent glacier loss affects the persistence of a large number of species across the mountainous region, including the stoneflies. Scientists measured the abundance and diversity of stream invertebrate communities across sites that varied in their amount of glacier loss.

Through that process, they identified a specialized suite of insects restricted to the highest elevation streams fed by not only melting glaciers, but also snowfields and groundwater springs.

The study projects a 70-80% decline in suitable habitat by the end of the century, but not necessarily a corresponding loss of this community, even with the complete disappearance of glaciers.

“Our results demonstrate that high-altitude streams and snow-fed water sources will continue to serve as refuges for mountain biodiversity as glaciers soon disappear,” Muhlfeld said. “These findings highlight the need to protect these important landscapes while addressing the root causes of climate warming at a global scale.”

The researchers note that climate change impacts on mountain biodiversity are complex and uncertain. They emphasize the urgent need to assess the widespread impacts of climate-induced glacier loss in high-elevation mountain ecosystems.

Other co-authors on the study are Joseph Giersch, Caitlin Florentine and Erich Peitzsch at the USGS Northern Rocky Mountain Science Center; Dean Jacobsen at the University of Copenhagen; and Scott Hotaling at Washington State University.

The glacier stoneflies that persist in the high alpine streams of Glacier National Park gained federal protection under the ESA last year, becoming the first listed species to face extinction solely due to climate change.

The U.S. Fish and Wildlife Service (FWS) announced the species warrant protection because the glaciers supplying their cold-water refuges are projected to disappear by 2030.

“These bugs are icons of climate change on a global scale,” Muhlfeld said. “They are the polar bears of Glacier National Park.”

Still, it’s uncertain what measures management agencies like FWS can or will take to preserve the insects, and the federal listing stopped short of designating critical habitat protections, reasoning that the species occupy areas already furnished with protection by the National Park Service and under the Wilderness Act.

However, given the close ties linking the future persistence of the stoneflies to their dependence on diminishing glaciers, resource managers said they could play a key educational role informing future climate-related policy.

“In terms of local management and conservation, there is very little if anything that local managers can do. This is a global phenomenon,” Muhlfeld said. “Ultimately, the most beneficial tool for conserving alpine stream biodiversity may rest in reducing human stressors such as global carbon emissions that contribute to global warming, glacial decline and the loss of alpine habitat.”

Giersch, the USGS researcher who co-authored the study, has ventured into Glacier Park’s remote alpine environs to study the insects for the past decade, and said additional research is needed to understand other cold-water dependent species occupying rarefied ecosystems.

“More research is urgently needed to assess the extent to which climate change threatens the persistence of [the western glacier stonefly] and other endemic mountaintop invertebrates and communities in Glacier National Park and worldwide,” Giersch said.

Muhlfeld agrees, adding: “What we are documenting here is really a call for action.”

Stay Connected with the Daily Roundup.

Sign up for our newsletter and get the best of the Beacon delivered every day to your inbox.