What Happened During the Earth's Very First Mass Extinction?

A new study published by a group of experts looks into the reason for the Late Ordovician mass extinction.

The dinosaurs perished in a cataclysmic extinction, as we all know. Did you know, though, that there have been other mass extinctions? The "big five" are the five most major mass extinctions, in which at least three-quarters of all species in existence throughout the whole Earth faced extinction within a particular geological epoch. Many scientists say we are now in the sixth epoch due to global warming and climate change tendencies.

Understanding the environmental conditions that led to the extinction of most species on Earth has long been a hot topic among scientists, as understanding the environmental needs that led to the extinction of most species in the past could potentially help prevent a similar event in the future.

Studying Mass Extinctions

A group of scientists from Syracuse University's Department of Earth and Environmental Sciences, the University of California, Berkeley and the University of California, Riverside, Université Bourgogne Franche-Comté, the University of New Mexico, the University of Ottawa, the University of Science and Technology of China, and Stanford University recently co-authored a paper on the Late Ordovician mass extinction (LOME), the first or oldest of the "big five" mass extinctions.

Alexandre Pohl (currently a postdoctoral research fellow at Université Bourgogne Franche-Comté in Dijon, France) and his co-authors looked at the ocean environment before, during, and after the extinction to see how it was brewed and triggered. Their research findings were published in the journal Nature Geoscience.

Changes in Diversity

According to Lu, a crucial conclusion from their research is that climate change can lead to decreasing oxygen levels in some sections of the ocean.

"The prevailing school of thinking in our area for decades has been that global warming causes seas to lose oxygen, affecting marine habitability and potentially upsetting the entire ecosystem," Lu explains. "In recent years, growing evidence has pointed to multiple periods in Earth's history when oxygen levels fell as temperatures cooled."

While the reasons for the Late Ordovician extinction are still unknown, the team's research eliminates changes in oxygenation as a single hypothesis for the extinction and provides additional evidence to support temperature change as the killing mechanism for LOME.

Pohl believes that if more climate data and powerful numerical models become available, they will provide a more reliable picture of the elements that may have contributed to the Late Ordovician mass extinction.

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