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Updated: Aug 15, 2026

Reconstructing Terrestrial Paleoclimate and Paleoecology with Fossil Leaves Using Digital Leaf Physiognomy and Leaf Mass Per Area
Published on: October 25, 2024
Forest canopy decline under elevated CO2 during the Paleocene-Eocene Thermal Maximum
Regan E Dunn1,2, Marieke Dechesne3, Brady Z Foreman4
1Samuel Oschin Global Center for Ice Age Research, La Brea Tar Pits, Natural History Museum of Los Angeles County, Los Angeles, CA, USA.
Abstract:
Uncertainty remains regarding the impact of rapid anthropogenic warming on forest ecosystem structure, biodiversity, and function. As an analog, we reconstruct forest canopy density and compositional change in Wyoming, USA, through the Paleocene-Eocene Thermal Maximum (PETM), an interval of abrupt carbon increase and warming ~56 million years ago. We develop a proxy to quantify leaf area index and assess shifts in floral composition using palynomorphs. Forest canopies opened abruptly at onset of PETM warming, landscape erosion increased, and vegetation shifted from broad-leaved angiosperm to fern- and palm-dominated ecosystems. When combined with regional data, these patterns suggest that continental-scale changes in plant communities cause landscape destabilization. These shifts also have implications for multimillennial-scale hydrologic and carbon cycle feedbacks in the climate system.
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