Study of glaciers in the Andes sheds light on future climate impact
image:
The Upper Santa Cruz Valley in Peru, showing darker ridges of moraines that were left behind as the glaciers receded.
view moreCredit: Aberystwyth University
Andean glaciers advanced during an acute period of climate change at the end of the last Ice Age, new research has found.
An international team of glaciologists, led by Aberystwyth University, made the discovery as part of a new project into tropical glaciers in Peru. The finding challenges long-held assumptions about glacier behaviour during this period.
The findings, published in Scientific Reports, shed new light on how glaciers respond to shifting climate patterns and may help improve predictions of future climate impacts.
The study focused on the Younger Dryas period, a time of sudden and dramatic climate change that occurred approximately 12,900 to 11,700 years ago. Contrary to previous theories, which suggest that glaciers in this area of Peru retreated during this time, the researchers found that those in the Santa Cruz Valley of Peru actually grew.
The glaciologists believe that this advance was driven by increased snowfall linked to seasonal shifts in the Intertropical Convergence Zone - a belt of low pressure that moves between the hemispheres and influences tropical weather patterns.
To reach their conclusions, the research team dated boulders transported and deposited by glaciers in the Santa Cruz Valley, Peru. Once deposited, these boulders serve as physical evidence of glacial movement over millennia and provide valuable insights into historical climate conditions.
Lead author Professor Neil Glasser from Aberystwyth University is a glacial geomorphologist who researches glacier change in southern South America. He said:
“Our study suggests that snowfall was a key factor driving glacier growth in the tropical Andes during the Younger Dryas. Unlike many other glaciers, the glaciers in this part of the Andes do not calve icebergs, where large sections of ice detach. They also lack heavy debris cover, making them especially well-suited for reconstructing past climate conditions. We were also able to date the timing of their advances more precisely than ever before.
“Our study shows that these glaciers are highly sensitive to climate shifts, particularly changes in precipitation patterns. Understanding the history of glacier advance and recession is really important because it helps us better anticipate how these glaciers will respond to future warming. This is especially important in Peru, where the glaciers are a source of fresh water for drinking, sanitation and irrigation of crops.”
The study was a collaborative effort involving researchers from the UK, Italy, Canada, and Peru.
Journal
Scientific Reports
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
Younger Dryas glacier advances in the tropical Andes driven by increased precipitation
Article Publication Date
22-Sep-2025
Climate change could erase 80% of whitebark pine’s current habitat across the Rockies and Northwest
What that means for bears, birds, farmers, and ranchers
University of Colorado Denver
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Using U.S. Forest Service and U.S. Fish and Wildlife Service data, CU Denver Professor Diana Tomback and her colleagues modeled how rising temperatures could shift the tree’s growth range across roughly 56 million acres in the U.S.
view moreCredit: University of Colorado Denver, Paul Wedlake
A new study, led by federal agencies in collaboration with the University of Colorado Denver, shows that the whitebark pine tree—an iconic, high-elevation tree that stretches from California’s Sierra Nevada through the Cascades and Rockies and into Canada—could lose as much as 80 percent of its habitat to climate change in the next 25 years.
The loss could have a cascade of effects, impacting wildlife and people.
The threatened whitebark pine tree is a crucial food source for squirrels and grizzly bears. It also acts as a natural snow fence, holding snowpack in place and releasing meltwater slowly throughout the summer. That runoff supports entire watersheds, which farmers and ranchers depend on. The nearest whitebark pine to us in Colorado is in the Greater Yellowstone Ecosystem in Wyoming.
“Whitebark pine supports biodiversity, and it helps people too,” said Diana Tomback, PhD, professor at the University of Colorado Denver. “The canopies act as a snow fence and slow snowmelt, enabling summer water flow, which farmers and ranchers depend on.”
The potential loss of whitebark pine habitat with climate warming is the focus of a study Tomback co-authored and which appeared earlier this month in the journal Environmental Research Letters.
A Shrinking Range
Using U.S. Forest Service and U.S. Fish and Wildlife Service data, Tomback and her colleagues modeled how rising temperatures could shift the tree’s growth range across roughly 56 million acres in the U.S.
“Even using a conservative model where the temperature increases 2 degrees, we’re looking at about an 80% loss of range,” Tomback said. “That means whole communities will lose their whitebark pine forests.”
The areas where whitebark pine is projected to survive are mostly in public lands, especially Wilderness Areas and national parks. While that shields them from development, it also limits the kinds of interventions allowed to help the species recover.
A Tree Under Attack
The whitebark pine is unlike any other tree on the threatened and endangered species list. It has the largest range and a unique partnership with the Clark’s nutcracker bird, which buries the tree’s seeds in soil—effectively planting the next generation. Without the bird, the seeds cannot spread.
Tomback discovered this relationship in the late 1970s and is now recognized as a national expert. But the tree species faces multiple threats: hotter temperatures, invasive blister rust disease, increasing wildfires, and mountain pine beetle outbreaks, which have killed many pine trees across the West.
Research and New Approaches to Conservation
To map the tree’s future, the research team used publicly available U.S. Forest Service plot data collected between 2007 and 2021 and climate variables from TopoTerra models. Their models produced detailed maps that can guide conservation efforts by pinpointing where the tree is most likely to persevere.
At the same time, CU Denver is also helping pioneer a minimally intrusive and cost-effective way to help restore trees in wilderness areas that mimics the Clark’s nutcracker method of burying a small number of whitebark pine seeds (caches) throughout an area. Tomback, and graduate student Abbigail King, have been working with the non-profit American Forests and the Bureau of Land Management to pilot a program in Idaho that aims to help with reforestation. If successful, the technique holds much promise because it is one of the few acceptable restoration techniques for designated wilderness areas, including some national parks.
American Forests’ collaborator on the project is CU Denver alum Elizabeth Pansing, who completed her PhD in Tomback’s lab working part on this problem.
“We’re still in the early stages of research to see if this technique will work,” King said. “I love that the field work I’m doing may be able to contribute to the regeneration of this tree and through that the other species that depend on it.”
The People Behind the Work
Other co-authors on the published study are: Sean A Parks, Kira L. Hefty, Jaclyn F. Rushing, Sara A. Goeking, Sharon M. Hood, J. Christopher Toney, Michèle R. Slaton, Benhamin S. Soderquist from the USDA Forest Service; Destin L. Harrell and James Lindstrom from the U.S. Fish & Wildlife Service; Cameron E. Naficy from the Department of Forest Ecosystems and Society at Oregon State University; and E.J. Taylor from the Laboratory of Tree-Ring Research at the University of Arizona, Tucson. Sean Parks is an ecological modeler with the USDA Forest Service Aldo Leopold Wilderness Institute in Missoula, MT,
Tomback joined CU Denver in 1981. She is a professor of integrative biology with expertise in evolutionary ecology, with application to forest ecology and conservation biology. She has a master’s degree in zoology from UCLA and a PhD in biological sciences from UC Santa Barbara. She has published more than 150 articles and presented at dozens of conferences. She is an AAAS fellow and her work with whitebark pine led to its inclusion as a threatened species in 2023, listed under the Endangered Species Act. Tomback together with several colleagues started the Whitebark Pine Ecosystem Foundation, a 501 (c)(3) non-profit based in Missoula, MT. The foundation is dedicated to the restoration of whitebark pine ecosystems and educating the public and resource management agencies about the importance of this pine. She has served as volunteer director of this organization for 17 years and now serves as Policy and Outreach Coordinator.
About the University of Colorado Denver
Millions of moments start at CU Denver, a place where innovation, research, and learning meet in the heart of a global city. We’re the state’s premier public urban research university with more than 100 in-demand, top ranked bachelor’s, master’s, and doctoral degree programs. We partner with diverse learners—at any stage of their life and career—for transformative educational experiences. Across seven schools and colleges, our leading faculty inspires and works alongside students to solve complex challenges and produce impactful creative work. As part of the state’s largest university system, CU Denver is a major contributor to the Colorado economy, with 2,000 employees and an annual economic impact of $800 million. To learn more about how CU Denver helps learners meet their moment, visit ucdenver.edu.
The whitebark pine is unlike any other tree on the threatened and endangered species list. It has the largest range and a unique partnership with the Clark’s nutcracker bird, which buries the tree’s seeds in soil—effectively planting the next generation. Without the bird, the seeds cannot spread.
Credit
Courtesy of Professor Diana Tomback.
Journal
Environmental Research
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
Whitebark pine in the United States projected to experience an 80% reduction in climatically suitable area by the mid-21st century
Article Publication Date
2-Sep-2025
COI Statement
No conflict. Disclosure: Co-author Diana Tomback started the Whitebark Pine Ecosystem Foundation, a 501 (c)(3) non-profit based in Missoula, MT. The foundation is dedicated to the restoration of whitebark pine ecosystems and educating the public and resource management agencies about the importance of this pine. She has served as volunteer director of this organization for 17 years and now serves as Policy and Outreach Coordinator.
