Paleobotanical study shows carbon spikes cause forest collapse

A new study published in Science suggests that rapid increases in atmospheric carbon dioxide can lead to the collapse of forest canopies rather than a greening effect. By analyzing fossilized leaf fragments from the Paleocene-Eocene Thermal Maximum (PETM)—a period approximately 56 million years ago—researchers reconstructed how ancient forests responded to massive carbon releases.

Using a method that examines the microscopic cell shapes of fossilized leaves, scientists determined that as temperatures rose and rainfall declined during the PETM, forest canopies became significantly more open. The research indicates that roughly 60% of the biomass of standing vegetation was lost, causing forests to wither and landscapes to brown.

Lead author Dr. Regan Dunn, a paleobotanist at the Natural History Museum of Los Angeles County, noted that while the PETM provides a natural comparison, the current rate of human-driven carbon emissions is faster than any known natural process in Earth's history. The study utilized fossil material from Wyoming’s Hanna Basin to reach these conclusions.