Geologists at Virginia Tech have discovered what triggered Earth’s first-ever mass extinction event, which occurred about 550 million years ago.
The study, titled “Environmental factors of the extinction of the first primate via the Ediacaran White Sea-Nama transition,” is published in Proceedings of the National Academy of Sciences, indicates that the decrease in global oxygen levels caused a mass extinction near the end of the Ediacaran period. The results show that about 80% of the animals died during this time.
Scott Evans, a postdoctoral researcher in the Department of Earth Sciences and lead of the research commented: “This included the loss of many different species of animals; however, those whose body plans and behaviors indicate that they depend on large amounts of oxygen appear to have been particularly affected. …this indicates that the extinction event was under ecological control, as with all other mass extinctions in the geological record.”
The discovery of the first mass extinction event in the world
Earth has experienced five mass extinction events that stand out in its animal history, including the Ordovician-Silurian Extinction (440 million years ago), the Late Devonian Extinction (370 million years ago), the Permian-Triassic Extinction (250 million years ago), and the Jurassic Triassic ( 200 million years ago), the Cretaceous and Paleogene extinction (65 million years ago).
Using new data collected by several researchers from the University of California Riverside’s Department of Earth and Planetary Sciences, researchers have discovered a new mass extinction event during the Ediacaran period, the oldest in history.
“Others have suggested that there may be an extinction at this time, but there has been a lot of speculation. So, we decided to put together everything we could to try and test those ideas,” Evans said.
The Ediacaran period spanned about 96 million years, sandwiched between the end of the Cryogenic period – 635 million years ago – and the beginning of the Cambrian period – 539 million years ago.
Track global oxygen levels
The team discovered from their data that reduced global oxygen availability was the main driver of this mass extinction.
Shuhai Xiao, professor in the Department of Earth Sciences and co-author of the study, explained: “Environmental changes, such as global warming and deoxygenation events, can lead to massive animal extinctions and profound disruption and ecosystem reorganization.
This has been demonstrated repeatedly in the study of Earth’s history, including this work on the first extinction documented in the fossil record. Thus, this study informs us of the long-term impact of current environmental changes on the biosphere.”
However, the reason for the low levels of oxygen on the planet remains a mystery.
“The short answer for how this happens is we don’t really know,” Evans said. “It could be any number and combination of volcanic eruptions, movement of tectonic plates, asteroid impact, etc., but what we’re seeing is that animals that are going extinct seem to respond to reduced global oxygen availability.”
Predict future extinction events
The team’s findings are pertinent, as Virginia Tech scientists recently found that hypoxia – the loss of oxygen availability – is affecting the world’s freshwater. They believe that rising temperatures are caused by climate change and runoff of excess pollutants from land use, affecting the water’s ability to retain oxygen. In addition, the decomposition of nutrients by freshwater microbes in the runoff consumes oxygen.
Evans concluded: “Our study shows that, as with all other mass extinctions in Earth’s past, this first new mass extinction of animals was caused by significant climate change – another in a long list of cautionary tales that illustrate the dangers of our current climate crisis from for animal life.