Scientists find ancient Wyoming forest took 100,000 years to recover from warming

A Wyoming forest lost about 60% of its canopy during a rapid warming event 56 million years ago and took more than 100,000 years to recover its former diversity and structure, according to new research.

The study examined tens of thousands of fossil leaves preserved in rocks from the Bighorn Basin in north-central Wyoming. The leaves accumulated in ancient rivers and floodplains, where fine mud and sand preserved impressions detailed enough to show their veins and edges.

Researchers used the fossils to reconstruct the forest before, during and after the Paleocene-Eocene Thermal Maximum, or PETM. The event pushed global temperatures up by several degrees in a geologically brief period. By identifying plant species and analysing traits such as leaf size, shape and margin type, scientists traced changes in species numbers, dominant plant types and canopy structure.

Before the warming event, the Wyoming forest was diverse and dense. It had a multilayered canopy of broadleaf trees and a rich understory, with many species suited to warm, wet conditions.

The findings show that the ecosystem did not quickly return to its earlier state after the climate changed. The long recovery, reported by Smithsonian Magazine, provides a detailed record of how an ancient forest responded to extreme warming and a comparison point for current climate change.