Ancient Wyoming forests lost most of their canopy during a rapid warming event
A new study shows that during the Paleocene-Eocene Thermal Maximum, forests in what is now southern Wyoming shed about 60% of their canopy, taking more than 100,000 years to recover.
Paleobotanists used microscopic leaf cuticles preserved in ancient sediments to infer the leaf area index of forests that existed 56 million years ago in southern Wyoming. Their analysis revealed that the onset of the Paleocene-Eocene Thermal Maximum triggered a rapid loss of roughly 60% of the forest canopy as temperatures rose by as much as 11 °F (6 °C). The resulting heat and drought killed large numbers of trees, allowing more sunlight to reach the ground and altering water flow and soil composition.
Over the next 100,000 years, the forest remained markedly open before gradually rebuilding as weathering removed atmospheric carbon and the climate cooled. Eventually the canopy became denser than before, helping to stabilize soils, regulate water cycles, and draw down carbon. The findings illustrate how past rapid warming pushed forests beyond physiological limits, offering a cautionary parallel for today’s accelerating human-driven climate change.
Why it matters
The study shows how extreme warming can cripple forests for tens of thousands of years, warning that current climate change may exceed ecosystem thresholds.
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