Frozen Forest Reveals Climate Impacts On Alpine Ecosystems
The discovery of a spectacular old forest on the Beartooth Plateau that was kept under ice by researchers at Montana State University (MSU) offers a unique glimpse into how alpine ecosystems may change as a result of warmer climates.
Ice melting has revealed an ancient woodland:
About 5,500 years ago, a change in summer solar radiation and accompanying volcanic cooling trapped the forest under ice. It lasted for centuries before dropping temperatures pushed it to recede downslope.
“This is pretty dramatic evidence of ecosystem change due to temperature warming. It’s an amazing story of how dynamic these systems are,” said David McWethy, one of the study’s authors and an associate professor in MSU’s Department of Earth Sciences.
In contrast to glaciers, ice patches do not flow; instead, their frozen layers retain deposited elements including pollen, charcoal, and macrofossils. These circumstances made it possible for the forest to survive until the ice melted due to recent warming, revealing the old remains.
Collaborative effort to decode climate history:
Craig Lee, who is currently an assistant professor at MSU, made previous discoveries that inspired the idea to search the Beartooth Plateau for hints about the past environment. Lee discovered a 10,300-year-old atlatl piece in the area in 2007, indicating that extensive records of environmental and cultural history were preserved in the ice layers.
Most of our best long-term climate records come from Greenland and Antarctica. It’s not a small thing to find ice patches that persisted for that long a time period at lower latitudes in the interior continent, McWethy noted.
Building on this finding, McWethy, Lee, and U.S. Geological Survey paleoclimatologist Greg Pederson started studying the ice patches in 2016. By 2018, their group has broadened the initiative to include more alpine ice patches in the area.
This collaborative effort involved tribes, federal agencies, and multiple universities and focused on reconstructing the area’s long-term climate history and its influence on Indigenous peoples.
Reconstructing the ancient alpine ecosystem:
To piece together the story of the forest, the team examined multiple elements of this alpine ecosystem. Using ice cores, they analyzed water isotopes and organic material, while Pederson harvested cross-sections of ancient wood for radiocarbon dating.
The results demonstrated that tree lines moved upward during a time of moderate and humid weather, enabling whitebark pine forests to flourish for 500 years.
“The plateau seems to have been the perfect place to allow for ice patches to establish and persist for thousands of years, recording important information on past climate, human activity and environmental change,” Pederson said.
According to the study, tree lines may rise once more as the climate warms, turning parts of the alpine tundra into forests. Pederson issued a warning, though, that the number, distribution, and makeup of these possible new woods will be influenced by elements including wind, precipitation, and snowpack.
“Growing season temperatures are the primary control on tree line elevation and latitude, but other factors such as moisture, wind, snowpack and human disturbance may play an important role in dictating forest structure and elevational limits,” he explained.
Ramifications for alpine environments:
The ecosystem and resources of the area may be significantly impacted by these changes, the experts caution. High-altitude snowfall, a vital supply of water for hydroelectric generation and farming, may change as tree lines rise.
Additionally, if forests encroach on tundra areas, they could increase the risk of wildfires due to changing fuel conditions.
Cathy Whitlock, a climate expert and MSU Regents Professor Emerita, emphasized the broader implications. She noted that reduced snowpack could strain water supplies, while McWethy added that the establishment of forests in tundra areas might fundamentally alter the region’s fire dynamics.
A Final Thought:
“That’s the reason why studies of past ecological change are more than interesting pieces of science. They have much larger implications for the resources we all depend on,” Pederson said.
The ancient forest on the Beartooth Plateau provides a glimpse into the possible future of high-altitude habitats as well as a stark warning of the planet’s dynamic ecosystems as climate change picks up speed.