Ancient Forest Uncovered in Greater Yellowstone Ecosystem Reveals Climate Shifts

Thawing ice in the Rocky Mountains has unveiled remnants of a prehistoric forest in the Greater Yellowstone Ecosystem, providing insight into how the region’s environment has evolved over millennia, IFLScience reports.

Researchers from Montana State University (MSU) uncovered the remains of a whitebark pine forest on the Beartooth Plateau at an elevation of 3,091 meters (10,141 feet).

This discovery, situated 180 meters (590 feet) above today’s treeline, suggests that the region once experienced warmer conditions, allowing trees to thrive at higher elevations.

Treelines, the altitude beyond which trees cannot grow due to harsh conditions, are sensitive indicators of climate. Warmer temperatures can raise treelines, while cooling trends can force them downslope. The remains of the Beartooth Plateau forest, estimated to have flourished 6,000 years ago, indicate that the area’s mean warm-season temperatures (May to October) once hovered around 6.2 °C (43°F)—comparable to conditions observed in the mid-to-late 20th century.

The forest persisted for centuries before succumbing to a sharp cooling event approximately 5,500 years ago. This climate shift, likely driven by volcanic activity in the Northern Hemisphere, caused a substantial temperature drop, rendering the area inhospitable for the forest’s survival.

The remarkable preservation of this ancient forest is credited to its burial under an ice patch, as opposed to a glacier. Unlike glaciers, which move and churn over time, ice patches remain relatively stable, allowing organic material to stay intact for millennia.

“This is dramatic evidence of ecosystem change due to temperature warming. It’s an amazing story of how dynamic these systems are,” said David McWethy, co-author of the study and associate professor in MSU’s Department of Earth Sciences.

The discovery offers researchers a rare opportunity to study long-term climate records outside the polar regions.

“Most of our best long-term climate records come from Greenland and Antarctica,” McWethy noted. “It’s not a small thing to find ice patches that persisted for that long at lower latitudes in the interior continent.”