Scientists have found that, two billion years ago, 99.5 percent of life vanished from Earth due to rapid and mass depletion of oxygen in oceans.
The mass extinction during the Great Oxidation Event delineated a shift from “feast” to “famine” conditions on our planet for about another billion years, researchers from Florida State University said in their study published in the journal Geology.
The mass die-off referred to as the Lau/Kozlowskii extinction was triggered by the rapid and widespread depletion of oxygen in the global oceans, they said.
The study “resolves a longstanding paleoclimate mystery, and raises urgent concerns about the ruinous fate that could befall our modern oceans if well-established trends of deoxygenation persist and accelerate,” according to Science Daily.
That is because, unlike other famous mass extinctions, there was no “known, spectacularly destructive event responsible for the Lau/Kozlowskii extinction.”
"This makes it one of the few extinction events that is comparable to the large-scale declines in biodiversity currently happening today, and a valuable window into future climate scenarios," said study co-author Seth Young, an assistant professor in the Department of Earth, Ocean and Atmospheric Science.
The scientists examined rocks from Hudson Bay, Canada, that would have formed billions of years ago, in search of barite, a mineral that holds key to understanding how much oxygen was in the atmosphere at a given time.
“From these rocks, the team was able to show that there was a massive drop in the level of life on Earth 2.05 billion years ago,” Newsweek reported.
"We were very surprised," study author Peter Crockford, from Israel's Weizmann Institute of Science and Princeton University, told the publication. "We didn't expect to see such a large signal, nor did we expect to find it in this specific type of sample.
"Over the 100 to 200 million years before this die-off event there was a large amount of life on the planet, but after this event a huge portion died off. However, instead of recovering like more recent mass extinctions, the amount of life on the planet or size of the biosphere stayed small for the following billion years of Earth's history—about two billion to one billion years ago."
He continued: "From our estimates it could be anywhere between about 99.5 percent to 80 percent of life on the planet died off around two billion years ago."
That’s far worse than the mass extinction of dinosaurs which saw about three-quarters of life on Earth disappear or the Great Dying event that resulted in the loss of around 70 percent of terrestrial life and 96 percent of ocean dwellers.
Study co-author Jeremy Owens, an assistant professor in the Department of Earth, Ocean and Atmospheric Science, said that the discovery could provide important lessons.
"This work provides another line of evidence that initial deoxygenation in ancient oceans coincides with the start of extinction events," he said. "This is important as our observations of the modern ocean suggest there is significant widespread deoxygenation which may cause greater stresses on organisms that require oxygen, and may be the initial steps towards another marine mass extinction."