The Earth’s Devonian era, which occurred over 370 million years ago, was a time of diversity and abundant sea life. It witnessed the appearance of the first seed-bearing plants, spreading as vast forests across Gondwana and Laurussia.
Debate has long surrounded a mass extinction event near the end of this era. Some scientists attribute the Late Devonian mass extinction to large-scale volcanic eruptions, resulting in global cooling; others blame a mass deoxygenation event caused by the expansion of land plants.
Researchers at IUPUI have published a study in the journal Communications Earth and Environment that suggests both factors played a role in the mass extinction event, shedding light on the current environmental tipping points the planet faces.
The study’s conclusion offers much to contemplate, according to Filippelli and Gilhooly. The emergence of new biological outcomes on land during the Devonian era had detrimental effects on ocean life. Similarly, modern-day human activities, such as fertilizer runoff and fossil fuel combustion, are depleting oxygen levels in the oceans, resulting in catastrophic consequences, similar to those seen in the Late Devonian.
“Throughout Earth’s history, there have been biological innovations and geological events that have completely reshaped environmental conditions in the ocean and on land,” Gilhooly said. “These historical insights can help us think of strategies to avoid future tipping points driven by human activities.”
Additional contributors to the study were Kazumi Ozaki of the Tokyo Institute of Technology, Christopher Reinhard of the Georgia Institute of Technology, John Marshall of the University of Southampton, and Jessica Whiteside of San Diego State University.
The study, co-authored by School of Science at IUPUI faculty Gabriel Filippelli and William Gilhooly III, was led by Matthew Smart, an assistant professor of oceanography at the U.S. Naval Academy who was a graduate student in Filippelli’s lab at the time of the study.
The study effectively reconciles two competing Late Devonian extinction theories into a comprehensive cause-and-effect scenario. The researchers concluded that both events — mass volcanism and deoxygenation caused by land plants — were necessary for the mass extinction to occur.
“The key to resolving this puzzle was identifying and integrating the timing and magnitude of the geochemical signals we determined using a sophisticated global model,” Filippelli said. “This modeling effort revealed that the magnitude of nutrient events could drive substantial marine extinction events, but the duration of the events required both factors — tree root evolution and volcanism — to sustain the toxic marine conditions.”
With experts in sedimentology,