Timeless Guardians: Ancient Trees Illuminate the Future of Greater Yellowstone Ecosystem

BILLINGS – For over 5,000 years, a cluster of whitebark pine trees in the Beartooth Mountains has been preserved in an ice patch.

During a warm prehistoric era, these trees flourished at an elevation exceeding 10,000 feet – approximately 600 feet higher than their current habitat. However, a series of cooler summers and volcanic activities in Iceland over the centuries gradually enlarged the ice patch, ultimately burying the trees.

With the rapid melting of high-altitude ice revealing the trees for the first time, researchers have undertaken an investigation to enhance understanding of how ongoing climate change may influence such habitats in the Greater Yellowstone Ecosystem moving forward.

New Research

Lead researcher Gregory Pederson, from the U.S. Geological Survey’s Northern Rocky Mountain Science Center in Bozeman, along with his team, recently released their results in the Proceedings of the National Academy of Sciences. The study is titled: “Dynamic treeline and cryosphere response to pronounced mid-Holocene climatic variability in the U.S. Rocky Mountains.”

Contributing authors include: Daniel Stahle, David McWethy, Matthew Toohey, Johann Jungclausd, Justin Martin, Mio Alt, Nickolas Kichasa, Nathan Chellman, Joseph McConnell, Craig Lee, and Cathy Whitlock.

“When colleagues from the Forest Service and I discovered this site in 2009, only a small amount of wood was visible,” wrote Lee, a professor at MSU’s Department of Sociology & Anthropology, in correspondence. “Much more was uncovered when we took the first samples of wood for analysis with Montana State University students in 2013.”

Whitlock, the director of Montana State University’s Paleoecology Lab, has dedicated decades to studying sediment cores from lakes in the GYE to gain a deeper understanding of past ecosystems. Pederson’s research contributes an additional dimension to this body of work, she remarked.

“Scientists (like myself) examine historical data for insights on how the Yellowstone ecosystem has reacted to warming phases,” Whitlock mentioned in her correspondence. “This remarkable discovery offers proof that the treeline is likely to shift to higher elevations with rising temperatures in the upcoming decades, provided that high altitudes maintain adequate moisture.”

Consequences

Pederson’s investigation of the ancient whitebark pine trees involved collecting samples from 30 “well-preserved large trees” characterized as “extraordinary quality,” estimated to be around 5,500 years old.

From the analysis of these trees, researchers determined that “at a minimum,” the forest existed from 5,940 years ago to 5,520 years ago. This positions the trees in the mid-Holocene – the latest interglacial era dating back 11,700 years.

“The structure, demographics, and growth record of the forest conserved in the ice patch likely signifies the conclusion of an extensive period (i.e., several centuries to millennia) of forest growth,” concluded the study. “This final account of forest growth at high altitudes on the Beartooth Plateau aligns with the swift development of the ice patches, although it is conceivable that small forest remnants endured for millennia post-establishment of the ice patches.”

As global temperatures rise, the study forecasted “rapid ice melting” and the potential for “treeline expansion across the Greater Yellowstone Ecosystem,” concluded Pederson and his collaborators.

“Conversely, if ongoing rapid warming leads to increased dryness (due to diminished precipitation and/or amplified evapotranspiration) and ecological disturbances (e.g., wildfires, insect infestation, disease), the treeline may descend in elevation as observed during the early Holocene,” the researchers stated.

Each possibility “has consequences for potential future high-altitude hydrologic conditions and water resources.”

The current temperature levels, according to the research, already “match or surpass the estimated mid-Holocene warm-season temperatures when the ice-patch forest was present and ice cover was significantly reduced.”

Lee remarked that the findings of the study are an excellent example of how “meticulous and remarkable” the analysis of ice patch materials can be.

“Essentially, these uniquely conserved samples provide an unprecedented glimpse into the climatic factors affecting one of our keystone species – whitebark pine – in our region 5,000 years ago,” he added. “Continuous yearly records, as well as decadal and even centennial records, are exceedingly crucial. They furnish comparative data points enabling us to contextualize our more detailed observations of the current climate we face today.”

This type of research takes years to complete, Lee noted, making mention of the “collaborative spirit” of previous Forest Service personnel for its achievements, including Jeff Dibenedetto, Halycon LaPoint, Mike Bergstrom, and Kyle Wright.

Related Research

The recent study expands on a similar investigation published in 2023 that “examined pollen, plant macrofossils, and charcoal” from a 10,400-year-old ice patch in the Beartooth Mountains and sediment from a 6,000-year-old wetland. Both sites were located approximately 3 miles from the preserved whitebark pine forest.

The 2023 research similarly studied the correlation between climate variability and changes in treeline elevation since the conclusion of the last Ice Age, revealing increases in tree pollen roughly 6,200 years ago and a subsequent cooler phase between 3,000 to 4,200 years ago.

This body of research can be traced back to 2008, when Lee took part in a study in the Colorado Rockies concerning Engelmann spruce trees that were found melting out of an ice patch. These trees dated back nearly 4,000 years and, similar to the recent study, documented a period when tree growth occurred at higher altitudes than it does presently.

Ice Discoveries

Melting ice patches have unveiled other remarkable discoveries in the Greater Yellowstone Ecosystem since 2010, when Lee uncovered a 10,000-year-old atlatl shaft.

“We didn’t understand until the early 2000s that there existed a potential for locating archaeological artifacts in conjunction with melting permanent snow and ice in various regions of the world,” Lee remarked at the time. “We’re not merely discussing major glaciers; we’re referring to the smaller, more kinetically stable snowbanks.”

Arguably, the most extraordinary ice field find occurred in 1991 when the remains of a 5,300-year-old man were found in the Tyrolean Alps. Ötzi, one of several designations he received by combining Yeti with his location in the Ötztal Range, met his demise when an arrow pierced his back, severing an artery.

Lisa Baril, a Wyoming-based author of “The Age of Melt: What Glaciers, Ice Mummies, and Ancient Artifacts Teach Us about Climate, Culture, and a Future Without Ice,” explored the Iceman museum for her book.

“I think climate change is one of those concepts that’s complex for individuals to fully comprehend in terms of its implications for their daily existence,” she shared with the Billings Gazette in September. “Archaeology serves as an excellent means to bridge that gap for many people.”

Regrettably, the astounding findings of ancient organic materials are under threat of being permanently lost as ice patches melt. According to NASA, the preceding decade has recorded the warmest temperatures ever.

“Recent warming across the western United States and worldwide has significantly altered mountain.

ecosystems due to reductions in snow and ice, heightened fire and insect disturbances, and modified species distributions,” Pederson’s research observed.

The warming climate of Earth is also a contributing factor that has resulted in the whitebark pine being designated as a threatened species under the Endangered Species Act. These slow-growing trees, some living to over 1,000 years, thrive at high altitudes in seven western states and two Canadian provinces where their seeds serve as a critical food supply for wildlife, such as grizzly bears. The trees also provide shade for snowpack, which helps to slow its thawing.

Knowledge foundation

The recent research expands upon an expanding foundation of understanding regarding climate change in the 22 million-acre GYE. This encompasses the 2021 release of the “Greater Yellowstone Climate Assessment,” which Whitlock was a co-author of.

A study examining GYE tree ring data, published in 2021, revealed a concerning pace of warming over a relatively brief period, as indicated by dendrochronologist Karen Heeter’s findings.

While Pederson’s study illustrates how vegetation at high elevations can transform during climate changes, it also highlighted another, possibly more troubling consequence: “the connected implications for water resources sourced from high elevations.”

In western regions such as Montana, snowmelt constitutes a vital source of drinking water for towns, in addition to supporting agricultural irrigation, fisheries, and water-related recreation.

The melting of ice patches also signals the conclusion of a thrilling epoch of high-elevation archaeological findings.

“These distinct alpine areas – effectively a repository for historical occurrences, whether they are the growth and decline of forests, or the usage of certain sites by animals as well as humans – are succumbing to melting,” Lee remarked. “A harsh and unwavering realization.”