Evidence from Mongolian Paleontology Expedition Supports Biogenic Climate Change Causation for Late Devonian Mass Extinction

Members of a U.N.-sponsored research team with members from Appalachian State University’s Department of Geology have found evidence for catastrophic oceanographic events associated with climate change and a mass extinction 375 million years ago that devastated tropical marine ecosystems.

“The Late Devonian mass extinction was one of the five largest mass extinction events in the history of life,” said Professor Johnny Waters, who is a co-leader of the five-year, U.N. International Geoscience Programme project that began in 2011. The research team, which includes Assistant Professor Sarah Carmichael, is examining the relationship between climate change and changes in the ecosystems in the Devonian period, from 419 to 359 million years ago.

“This is the third most significant mass extinction and it was caused by plants,” Waters said. “Unlike the dinosaur mass extinction, which was related to an asteroid impact, this one was environmentally related.”

In the Devonian period, Waters explained, the world was experiencing super greenhouse climate conditions. This means that it was very warm, there probably were no ice caps, there was a lot carbon dioxide in the atmosphere (with estimates of 4,000 parts per million).

“As plant communities expanded onto land to form the first forests, they depleted the carbon dioxide (CO2) that was in the atmosphere,” Waters said. “CO2 levels dropped to 400 ppm toward the end of the Devonian. It got colder. There were glaciation events and the rapid change in the climate caused severe extinction in the tropics and the existing coral reefs became extinct.” By comparison, the world’s current CO2 level is very close to 400 ppm.

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