Ancient Wyoming forest lost 60% of canopy during rapid warming, took >100,000 years to recover

A new study published in Science reconstructed a Wyoming forest using a massive dataset of fossil leaves collected from the Bighorn Basin. By analyzing leaf size, shape and margin traits, scientists quantified how the forest responded to the Paleocene-Eocene Thermal Maximum, a rapid global warming episode 56 million years ago. The data indicate that canopy cover dropped by about 60% as many shade-loving species disappeared and heat-tolerant taxa became dominant.

Although global temperatures eventually declined, the forest’s species richness and structural complexity stayed low for more than a hundred thousand years, and some pre-event species never returned. The research provides a rare, high-resolution view of how ancient forests reacted to extreme warming and underscores that recovery can far outlast the warming itself. These findings offer a long-term perspective on the potential consequences of today’s accelerating climate change for modern forests.