- A study published Sept. 2 in the journal Environmental Research Letters forecasts an 80% reduction in the area with suitable climates for whitebark pine by the mid-21st century.
- This long-lived, high-elevation tree plays a critical role in mountain ecosystems in western North America, providing food for wildlife and regulating water supplies.
- But a disease-causing fungus has ravaged whitebark and other pine species, compounded by other threats, such as wildfire, mountain pine beetles and climate change.
- The research, which identifies areas that will likely be climatically suitable for whitebark pine in the future, could help guide restoration efforts to save the species.
Hotter and drier conditions could whittle away 80% of land where whitebark pine grows by the middle of this century, according to a recent study.
Scattered across the highest parts of the Rocky Mountains, the Cascades and the Sierra Nevada in the western U.S. and southwestern Canada, the species is a linchpin of alpine ecosystems. But now, “It’s basically just being pushed off the mountain,” said Sean Parks, a research scientist and the paper’s lead author. “There’s nowhere for it to go.” The work was published in the journal Environmental Research Letters.
The research also projects that protected areas — places like Yellowstone, Mount Rainier and Yosemite national parks and the designated wilderness around them — will cover three-quarters of the territory best suited for whitebark pine. While such locations could help safeguard existing stands, rules and policies around human interventions in these spots could also snarl restoration efforts.
Whitebark pines (Pinus albicaulis) can tower to 18 meters (60 feet) or more, while others carve out a stunted existence known as krummholz — German for “crooked wood” — growing only about hip-high on the harshest, most windswept slopes.
Across its range, this pine shades and anchors snowpack, slowing its melt and stabilizing the precious provision of water throughout the summer for plants, animals and people. And the thick-scaled, purple-hued cones the tree produces offer valuable sustenance to wildlife as diverse as grizzly bears (Ursus arctos horribilis), wolverines (Gulo gulo) and, notably, Clark’s nutcracker (Nucifraga columbiana), a chattering bird on which whitebarks rely to disperse their seeds.
Catherine Airey, a research engineer at the University of Reims Champagne-Ardenne in France, calls this tree “charismatic megaflora,” riffing on a term usually reserved for animals.
“It’s beautiful, can live for centuries [and grows] in majestic mountainous settings,” Airey, who was not involved with the study, said in an email to Mongabay.
But scientists have long tracked — and worked to stem — the decline of the whitebark, which is listed as threatened under the U.S. Endangered Species Act. Most worrying is a fungus, Cronartium ribicola, that humans introduced to North America in the 1900s. It causes white pine blister rust, a devastating disease that chokes off water and nutrients to whitebark needles, branches and trunks and can kill entire stands.
Along with blister rust, climate change portends an uncertain future for the whitebark pine. The conditions it creates drive more intense and more frequent fires. And drought-stressed trees are more susceptible to fungal infections that result from outbreaks of native mountain pine beetles (Dendroctonus ponderosae), which in turn can live longer into warmer winters and thus do more.
For this study, Parks and his colleagues modeled changing climate conditions, using measurements of water availability, temperatures and transpiration — trees’ release of water vapor — in the species’ current range. The analysis revealed a drastic reduction in “climatically suitable” conditions for whitebark pine by the middle of the century, with maps showing constriction of lower-elevation habitat.
The maps also identified areas conducive to whitebark growth over that same period, providing a “really useful” management tool to help the species survive, said Airey, who called the work “a carefully planned out, statistically robust study.”
“With funds and personnel chronically limited, the more information management decision makers can have to help guide them, the better,” she added, “especially as restoration is a long-term project.”
Efforts to save the species have zeroed in on finding living trees that possess the genetic tools to withstand the challenges whitebark pine faces.
“The goal of restoration is to build resilient populations that can handle change in climate, but also more importantly, resistance to white pine blister rust,” said Diana Tomback, a professor of integrative biology at the University of Colorado Denver and a co-author of the study. She’s part of a group of government, tribal and nonprofit partners working on a concerted restoration plan for whitebark, which, she added, could be a model for similarly threatened tree species.
In the 1980s, Tomback uncovered the vital role that Clark’s nutcracker plays in the whitebark pine’s life cycle. The nutcracker, a relative of crows and jays, splits open whitebark cones and extracts their seeds, each stashing an average of more than 30,000 in the ground every year. The birds, not to mention pilfering rodents, will come back to feast on some of their caches. But they don’t return to all of them, leaving many seeds buried in the earth potentially to germinate and grow into trees.
Human-led restoration follows much the same playbook, Tomback said — albeit starting with seeds from blister rust-resistant trees. Teams harvest cones and may grow seedlings in greenhouses before bringing them back to the mountains. Or they might use direct seeding, Tomback said. “We put seeds in the ground, just like nutcrackers do.”
The majority of habitat likely to be viable for whitebark is designated as national parks and wilderness, which highlights the importance of protected landscapes for the future of this pine. “It makes public lands, number one, absolutely crucial,” Tomback said.
But this also poses challenges for saving the species, she added.
In the U.S., the Wilderness Act of 1964 called for designated areas to be “untrammeled” by humans and describes the essential character of wilderness as “affected primarily by the forces of nature, with the imprint of man’s work substantially unnoticeable.”
But many scientists believe that only human intervention will help whitebark pine (and other imperiled species) survive –– through managed relocation to areas with suitable growing conditions.
Airey said the task is “urgent.”
“Whitebark pine decline has been known about for decades,” she added, “and we haven’t been able to do enough to slow tree death and population decline.”
Accomplishing those goals may require reevaluating policies and practices dictating what can and can’t be done in designated wilderness. To Sean Parks, the impetus to act stems from a recognition of how humans have already impacted wild spaces, from injecting blister rust into ecosystems to altering fire regimes.
“We’ve done all these terrible things to whitebark pine and other species, too,” he said. “I feel like we almost have a moral imperative to try to right our wrong.”
Old forests, new fires, and a scientific standoff over active management
Banner image: A Clark’s nutcracker, pictured here in California. Image by LassenNPS via Wikimedia Commons (Public domain).
John Cannon is a staff features writer with Mongabay. Find him on Bluesky and LinkedIn.
Citations:
Parks, S. A., Hefty, K. L., Rushing, J. F., Goeking, S. A., Tomback, D. F., Hood, S. M., … Taylor, E. J. (2025). Whitebark pine in the United States projected to experience an 80% reduction in climatically suitable area by the mid-21st century. Environmental Research Letters, 20(10), 104012. doi:10.1088/1748-9326/adfcef
Tomback, D. F. (1982). Dispersal of whitebark pine seeds by Clark’s Nutcracker: A Mutualism Hypothesis. Journal of Animal Ecology, 51(2), 451–467. doi:10.2307/3976
Tomback, D. F., & Sprague, E. (2022). The National Whitebark Pine Restoration Plan: Restoration model for the high elevation five-needle white pines. Forest Ecology and Management, 521, 120204. doi:10.1016/j.foreco.2022.120204
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