Wyoming Fossils Show Forests Took 100,000 Years to Recover from Ancient Warming

A new study published in the journal Science reveals that during the Paleocene-Eocene Thermal Maximum (PETM) 56 million years ago, forests in southern Wyoming lost 60% of their canopy and took over 100,000 years to recover. The research, led by Dr. Regan Dunn of the La Brea Tar Pits and University of Southern California, used fossil leaf cuticles to reconstruct forest canopy density. The study found that just before rapid warming, canopies were at their densest, but as temperatures rose by up to 11°F (6°C), heat and drought killed trees, thinning canopies. Ferns briefly flourished, then palms and warmth-loving plants spread northward. The loss of canopy altered water and sediment movement, changing the landscape. The study highlights that while higher CO2 can stimulate growth, beyond temperature and water limits, forests decline. Recovery took over 100,000 years, far longer than a human lifespan. The authors warn that current human-caused warming is faster than the PETM, and forests may face similar thresholds. The study was co-authored by Marieke Dechesne and Ellen Currano, who collected fossils in Wyoming. The research was originally published at The Conversation.