Wyoming Forest Lost 60% of Its Canopy During Ancient Warming, Took 100,000 Years to Recover
Fossil leaves from Wyoming’s Bighorn Basin have allowed scientists to reconstruct how a subtropical forest responded to the Paleocene-Eocene Thermal Maximum about 56 million years ago. The forest lost roughly 60% of its canopy and suffered a major decline in plant diversity. Researchers found that recovery took more than 100,000 years, offering a long-term view of how forests can respond to rapid climate warming. Article:
A forest that existed in what is now Wyoming about 56 million years ago underwent a dramatic transformation during a period of rapid global warming, losing around 60% of its canopy and much of its plant diversity.
Researchers reconstructed the ancient ecosystem using tens of thousands of fossil leaves preserved in the Bighorn Basin of north-central Wyoming. Their findings, published in Science under the study titled Forest canopy decline under elevated CO2 during the Paleocene-Eocene Thermal Maximum, show that the forest took more than 100,000 years to regain much of its diversity and structural complexity.
The findings provide one of the detailed fossil records of how forest ecosystems responded to the Paleocene-Eocene Thermal Maximum, or PETM, a major warming event that occurred roughly 56 million years ago.
Fossil leaves reveal how the forest changed
The Bighorn Basin contains sedimentary rocks that preserve exceptionally detailed plant fossils. Leaves buried in ancient rivers and floodplains left impressions that retained features such as their edges and vein patterns.
Scientists used these remains to identify plant species and examine characteristics including leaf size, shape and margins. Such traits can provide clues about temperature, moisture and the amount of sunlight reaching different parts of a forest.
By comparing fossil leaves from periods before, during and after the PETM, researchers were able to track changes in the Wyoming forest as temperatures increased and later declined.
Before the warming event, the area supported a diverse, dense subtropical forest with multiple canopy layers and a substantial understory.
Ancient warming changed the forest structure
The fossil record changes sharply during the PETM.
The number of plant species fell, while large leaves associated with a dense, shaded canopy became less common. Plants better suited to hotter, drier and more open conditions became more dominant.
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