El Niño and mega ocean warming events were key in driving the largest extinction of life on planet Earth some 252 million years ago, according to new research
Over 250 million years ago, long before dinosaurs evolved, nine out every 10 plant and animal species were wiped out in the largest extinction of life on planet Earth.
New research has shed light on how ocean warming El Niño events were key in driving this mass extinction. The study, published in Science and co-led by the University of Bristol and China University of Geosciences (Wuhan), reveals why the effects of rapid climate change in the Permian-Triassic warming were so devastating for all forms of life in the sea and on land.
The reasons behind this mass extinction have long been attributed to vast volcanic eruptions in what is now Siberia. The resulting CO2 emissions rapidly accelerated climate warming, causing widespread stagnation and the collapse of marine and terrestrial ecosystems.
But what caused life on land, including plants and usually resilient insects, to suffer just as badly has remained a source of mystery.
“Increased weather and climate variability de it even more ‘wild’ and difficult for life to survive.”
Co-lead author Dr Alexander Farnsworth, Senior Research Associate at the University of Bristol, said: “Climate warming alone cannot drive such devastating extinctions because, as we are seeing today, when the tropics become too hot, species migrate to cooler, higher latitudes. Our research has revealed that increased greenhouse gases don’t just make the majority of the planet warmer, they also increased weather and climate variability making it even more ‘wild’ and difficult for life to survive.”
Unstable conditions
The Permian-Triassic catastrophe shows the problem of global warming as not just a matter of it becoming unbearably hot, but also a case of conditions swinging wildly over decades.
“Most life failed to adapt to these conditions, but thankfully a few things survived, without which we wouldn’t be here today,” said co-lead author Professor Yadong Sun at China University of Geosciences, Wuhan.
“It was nearly, but not quite, the end of the life on Earth”
Part of the study involved analysing oxygen isotopes in the fossilised tooth material of tiny extinct organisms called conodonts. By studying the temperature record of conodonts from around the world, the researchers were able to show a remarkable collapse of temperature gradients in the low and mid latitudes.
“Essentially, it got too hot everywhere," said Dr Farnsworth, who used pioneering climate modelling to evaluate the findings. "The changes responsible for the climate patterns identified were profound because there were much more intense and prolonged El Niño events than witnessed today. Species were simply not equipped to adapt or evolve quickly enough.”
Today's climate
In recent years El Niño events have caused major changes in rainfall patterns and temperature. For example, the weather extremes that caused the June 2024 North American heatwave when temperatures were around 15°C hotter than normal. 2023-2024 was also one of the hottest years on record globally due to a strong El Niño in the Pacific, which was further exacerbated by increased human-induced CO2 driving catastrophic drought and fires around the world.
“Mass extinctions, although rare, are integral to the Earth’s natural system”
“Fortunately such events so far have only lasted one to two years at a time. During the Permian-Triassic crisis, El Niño persisted for much longer resulting in a decade of widespread drought, followed by years of flooding. Basically, the climate was all over the place and that makes it very hard for any species to adapt,” co-author Paul Wignall, Professor of Palaeoenvironments at the University of Leeds.
Researchers observed that the scale of the Permian-Triassic extinction was so massive because these Mega-El Niños created positive feedback on the climate, which led to incredibly warm conditions starting in the tropics and then beyond. This resulted in the dieback of vegetation. Plants are essential for removing CO2 from the atmosphere, and if they die so does one of the Earth's mechanisms to stop CO2 building up in the atmosphere.
Death on land, followed by the oceans
“Whilst the oceans were initially shielded from the temperature rises, the mega-El Nino’s caused temperatures on land to exceed most species thermal tolerances at rates so rapid that they could not adapt in time,” explained Dr Sun.
“Only species that could migrate quickly could survive, and there weren’t many plants or animals that could do that.”
Mass extinctions, although rare, are integral to the Earth’s natural system, resetting life and evolution along different paths.
“The Permo-Triassic mass extinction, although devastating, would ultimately see the rise of dinosaurs becoming the dominant species thereafter as would the Cretaceous mass extinction lead to the rise of mammals, and humans,” Dr Farnsworth concluded.
Source: Press release from the University of Bristol https://www.bristol.ac.uk/news/2024/september/el-nino.html