Climate change led to the extinction of 90% of life on Earth millions of years ago

A cataclysm has taken over our planet about 252 million years ago, wiping out more than 90% of all life on Earth.

Known as the Great Extinction the mass extinction that ended the Permian geological period was the worst of the five global catastrophic events in Earth’s history, more devastating than that caused by a giant asteroid that brought about the ruin of the dinosaurs.

The most credible explanation put forward so far has been that carbon dioxide released by volcanic activity in a region known as the Siberian Traps caused the planet to warm rapidly. Emissions across a vast area of ​​what is now Russia resulted in higher temperatures, acid rain and ocean acidification.

However, a mega El Niño effect — similar to, but more intense and prolonged than the way the climate phenomenon is experienced today — may have played a key role, according to new research published in the journal Science.

“What we’re showing is that this was a climate-driven extinction crisis. It wasn’t just the warming, it was how the climate responded,” said study co-author Paul Wignall, a professor of paleoenvironments at the University of Leeds in the United Kingdom.

“If conditions were bad but constant, life could have evolved to cope with that. But the fact is that it kept swinging from one extreme to the other over the decades,” he added.

The research team built a computer model of the global climate during the late Permian Period that suggested that as global temperatures rose, El Niño events — which originate in the Pacific Ocean but affect climate worldwide — increased in magnitude and duration.

The phenomenon raised temperatures and resulted in alternating periods of flooding and scorching droughts that would have triggered wildfires, devastating all types of species around the world over a period of about 100,000 years.

Large-scale El Niño events

Currently, an El Niño event, which affects wind patterns and ocean currents, typically lasts between 9 and 18 months and occurs every two to seven years.

Alex Farnsworth, a senior research associate at the University of Bristol in the UK and co-lead author of the study, said that during the warmest phases of the extinction event, an El Niño episode would have lasted 10 years.

The El Niño of 252 million years ago would have originated in the Panthalassic Ocean, a body of water much larger than the current Pacific and which could retain more heat, which in turn would have strengthened and sustained the effects of El Niño.

He added that volcanic activity remained an important factor, but was not enough on its own to explain the scale of the biological catastrophe that unfolded. The planet had experienced similar episodes before, but they did not trigger a mass extinction.

“Volcanism was the main culprit here, but it had a mechanism influencing ocean dynamics that led to the development of these much stronger El Niños and then (the two things) acted together,” Wignall said.

A prolonged and intense El Niño also explains why extinctions began on land before occurring in the ocean, the study said.

“Although the oceans were initially protected from rising temperatures, the mega El Niño caused temperatures on land to exceed the thermal tolerances of most species at such rapid rates that they were unable to adapt in time,” said co-lead author Yadong Sun, a researcher at the Chinese University of Geosciences in Wuhan, in a press release.

“Only species that could migrate quickly were able to survive, and there weren’t many plants or animals that could do that,” he added.

One of the main reasons the end-Permian extinction was so terrible was because mega El Niños created incredibly warm conditions in the tropics, which quickly spread to higher latitudes, resulting in the loss of most vegetation and its ability to remove carbon dioxide from the atmosphere.

“You lose all the trees at that time, which is amazing. Nothing would have grown above your knees in the early Triassic,” Wignall said, referring to the geological era that followed the extinction event, when the ecosystem began to recover.

Past changes in temperature can be determined in a variety of ways — from plant and animal fossils, sediment and ice cores, and, for more recent changes, tree rings and corals. This data can be used to build computer models that help scientists reconstruct and understand what past conditions and climate systems were like.

Farnsworth said the team’s climate model, which took months to run multiple simulations, was better than its predecessors at piecing together what happened because of new, detailed temperature data collected from fossils of small, eel-like creatures known as conodonts, and analyzed over a long period. That data showed how temperatures rose at different latitudes as the mass extinction unfolded.

The ratio of two different or variant oxygen isotopes in the fossilized dental material of conodonts, which were common in the ocean at that time, depended on temperature, he added.

Alfio Alessandro Chiarenza, a Royal Society Newton International Fellow in the department of earth sciences at University College London, said it would now be interesting to find evidence in the fossil record of how organisms — including trilobites, early amphibians, reptile-like mammalian ancestors and early crocodiles — were affected by the extinction and which aspects of their biology were most severely impacted by these climatic upheavals.

“This study provides yet another example of how complex and interconnected climate and environmental dynamics are and how such processes can radically affect ecological balance — a serious warning in light of our current ecological crisis,” said Chiarenza, who was not involved in the study.

Resonance with the current climate crisis

Some researchers now believe we are in the midst of a sixth mass extinction and that the end-Permian extinction may hold lessons for the current climate crisis.

Current El Niño events are known to cause coral bleaching and mass fish mortality, the study noted, but the ecological impact and future trajectory of El Niño events in a warmer climate are unknown.

However, Wignall said the world 252 million years ago was geographically a different place — home to a huge supercontinent called Pangaea and a massive ocean, which may have made it more sensitive to carbon dioxide spewed by supervolcanoes.

“The end-Permian is the biggest crisis in Earth’s history from the perspective of life, but I don’t think we’ll ever get anywhere near those conditions again because[Earth at that time]was a very strange planet, with a continent on one side and a gigantic ocean on the other,” he said. “The planet was really vulnerable at that time.”

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This content was originally published in Climate change led to the extinction of 90% of life on Earth millions of years ago on the CNN Brasil website.

Source: CNN Brasil