An ancient forest is again seeing daylight after spending thousands of years hidden under ice in the Rocky Mountains. It comes as a team of scientists from Montana State University have been working with the U.S. Geological Survey and collaborating institutions to discover the ancient whitebark pine forest while on an archeological survey on the Beartooth plateau in Wyoming – which is only possible thanks to warming temperatures that melted the ice previously covering it.
“We were really surprised to find a forest was emerging from the margins of the ice…. It was amazing,” Cathy Whitlock, a Department of Earth Sciences professor at Montana State University, told As It Happens podcast host Nil KÓ§ksal last week. Whitlock’s team found 30 trees 3,000 metres above sea level, 180 metres higher than the current tree line. Their research, published in Proceedings of the National Academy of Sciences, is just as exciting as bittersweet: After all, the only reason they could make the find is due to the melting ice.
“I’m thrilled because it’s a window on the past. It tells us what this high-elevation environment was like 6,000 years ago,” Whitlock told the podcast. “But as a person who worries about the future and climate change and what these alpine areas will look like for my grandchildren, it makes me really sad. These ice patches are melting, and they probably won’t be there in a few more decades.”
Cathy Whitlock, a Department of Earth Sciences professor at Montana State University
Using carbon dating to determine the trees’ age, Whitlock’s team discovered that the trees ranged in age from 5,950 to 5,440 years ago, providing key information about the climate the trees would’ve lived in:
“It was a pretty well-developed forest. These were not the kind of scruffy trees that you see in treeline. These were tall-standing trees,” said Whitlock, adding that about 5,000 years ago, “the climate started to cool, and an ice patch developed. The ice would’ve killed the trees, leaving them buried under the developing ice patch.”
Speaking to Canadian-based CBC News, Professor Colin Laroque, a specialist in tree age estimation, said the research is a startling reminder of how quickly the climate is changing: “We see how rapid the warming we are experiencing now is happening. What took thousands of years to do in the past is taking decades to unravel today,” according to Laroque, a University of Saskatchewan professor who was not involved in the study.
This is not the first such discovery in North America.
In western British Columbia, melting ice has revealed old forests along the Coast Mountains. In Wyoming, Whitlock says there’s more work to do. Her team will continue examining the ice patch’s chemistry to learn how the climate changes: “There’s a lot that we don’t know about these high-elevation forests and how they’re going to respond in the future,” she said.
Whitlock says what they’ve learned so far shows the power of climate change and how easily the world can change as the temperature warms or cools.
“It makes me appreciate how sensitive these high-elevation environments are,” Whitlock said. “We can go from tundra to forest with just a small amount of warming. And so it’s very, very sensitive to climate change.”
She says that as the temperature warms, this forest may someday return, and the current treeline will likely move to a higher elevation. With it, the area will lose an important source of water:
“One thing that seems pretty clear is that we’re going to lose our snowpack at high elevations, and that’s simply because it’s warmer. There’s less snowfall. More of the precipitation falls as rain instead of snow, and it melts sooner,” said Whitlock. “As the climate changes, we’re going to lose that source of water and it’s going to just be part of the reason why the West is becoming drier and will continue to dry.”
To read more: G.T. Pederson, D. Stahle, D.B. McWethy, M. Toohey, J. Jungclaus, C. Lee, J. Martin, M. Alt, N. Kichas, N. Chellman, J.R. McConnell, C. Whitlock, Dynamic treeline and cryosphere response to pronounced mid-Holocene climatic variability in the US Rocky Mountains, Proc. Natl. Acad. Sci. U.S.A. 122 (2) e2412162121, https://doi.org/10.1073/pnas.2412162121 (2025).