A groundbreaking study published in Science, co-led by researchers from the University of Bristol and China University of Geosciences (Wuhan), has uncovered new insights into the causes of the most catastrophic mass extinction in Earth’s history: the Permian-Triassic extinction. This event, which took place around 252 million years ago, wiped out approximately 90% of marine species and 70% of land species. The study points to an abnormally long and intense series of El Niño events as a key factor in the devastation.

For years, scientists have attributed this mass extinction primarily to massive volcanic eruptions in what is now Siberia. These eruptions released vast amounts of carbon dioxide into the atmosphere, triggering rapid global warming. This led to widespread ecosystem collapse on both land and in the oceans. However, the question of why even hardy land species like plants and insects suffered has long puzzled scientists.

According to the study, the warming alone couldn’t account for the severity of the extinction. Lead researcher Dr. Alexander Farnsworth from the University of Bristol explains: Climate warming alone cannot cause such devastating extinctions because species can migrate to cooler latitudes when the tropics become too hot. He goes on to say that in this case, the escalation of greenhouse gases not only raised global temperatures but also increased climatic and meteorological variability, making conditions far too volatile for most species to survive.

The study found that intense El Niño events during this period played a critical role in amplifying the already harsh environmental conditions. El Niño is a natural climate phenomenon that disrupts typical weather patterns, causing extreme weather such as floods and droughts. Today, El Niño events last one to two years, but during the Permian-Triassic period, they persisted for much longer—devastating ecosystems across the globe.

Farnsworth and his colleagues examined oxygen isotopes in the fossilized teeth of tiny, extinct marine organisms known as conodonts. These isotopes helped reconstruct the global temperature record of the time, revealing that temperatures spiked dramatically, particularly in the lower latitudes. The researchers found that the intense El Niño-like patterns, combined with extreme volcanic activity, drove these temperature anomalies and created environmental chaos.

Surface temperature (°C) of the warmest month during peak-warmth for the Permian-Triassic mass extinction 252 million years ago.
Surface temperature (°C) of the warmest month during peak-warmth for the Permian-Triassic mass extinction 252 million years ago. Credit: University of Bristol / China University of Geosciences (Wuhan)

The long duration of these El Niño events led to prolonged droughts followed by years of intense flooding. This made it incredibly difficult for species to adapt, as they faced not only rising temperatures but also wildly fluctuating weather conditions. The climate was erratic and unpredictable, and species simply couldn’t evolve or adapt quickly enough, says Farnsworth.

The study also highlights the role of wildfires, which became rampant due to prolonged droughts. The Earth’s land surfaces burned frequently, while the oceans became stagnant, devoid of oxygen. This left no refuge for life to survive.

One of the most intriguing findings of the research is that these Mega-El Niño events created a positive feedback loop in the climate system. The warming started in the tropics and gradually spread beyond, leading to the collapse of vegetation. Since plants play a crucial role in removing carbon dioxide from the atmosphere, their extinction further accelerated the accumulation of CO2, exacerbating the warming.

This catastrophic climate feedback helps explain why the extinction on land occurred tens of thousands of years before the extinction in the oceans. While the oceans were initially insulated from the rising temperatures, the mega-El Niños pushed land temperatures beyond the thermal tolerance of most species, resulting in rapid extinction on land, explains Professor Yadong Sun, co-author of the study.

Although mass extinctions are rare, they are crucial to resetting Earth’s evolutionary clock, allowing new forms of life to dominate. In the aftermath of the Permian-Triassic extinction, the Earth saw the rise of dinosaurs, much like how mammals, and eventually humans, emerged after the extinction of the dinosaurs millions of years later.

SOURCES

University of Bristol

Yadong Sun et al., Mega El Niño instigated the end-Permian mass extinction. Science385, 1189-1195(2024). DOI:10.1126/science.ado2030

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