The research warns of parallels to modern climate change.
The Permian-Triassic mass extinction, which eradicated 96% of marine species 252 million years ago, has long baffled scientists. This created conditions that killed off species with slow metabolisms, such as brachiopods, while more active organisms like bivalves survived. The findings, published in the *Proceedings of the National Academy of Sciences*, not only solve a decades-old mystery but also sound an alarm for today’s climate crisis.
The Permian-Triassic Crisis: A World Similar to Today
The Great Dying began with a world eerily similar to today’s: a cool, oxygen-rich ocean. But a series of massive volcanic eruptions, likely from the Siberian Traps, released carbon dioxide that transformed the planet. “The biggest mass extinction of all time started from a world that is very similar to today,” Sperling said in a statement. The study, which combined experiments on modern and ancient marine species, reveals that warming oceans and oxygen loss were the primary killers. “Our findings show that, across different organism groups, extinctions happened at much higher rates for those more vulnerable to increases in water temperature and decreases in oxygen availability,” Marquez explained.
The research builds on a 2018 study that linked ocean warming and oxygen loss to the extinction, but this new work fills critical gaps by testing the physiology of Paleozoic fauna. “In our new study, we filled in this gap about the physiology of the Paleozoic fauna to see if we could explain not only the biogeography of the extinction but the taxonomic selectivity of the extinction,” Sperling said. By measuring oxygen use in brachiopods and modern bivalves under varying temperatures, the team found that ancient species could survive in low-oxygen conditions but failed when temperatures rose.
Metabolic Vulnerability: Why Some Species Died and Others Survived
During the Paleozoic era, marine life was dominated by slow-moving, filter-feeding animals like brachiopods, crinoids, and certain corals. These organisms had low metabolic rates, allowing them to thrive in oxygen-poor environments. However, when ocean temperatures spiked, their bodies couldn’t keep up. “The Paleozoic fauna can live in water with less oxygen, under conditions that would asphyxiate ocean animals from the modern groups. But when the temperature increases, the Paleozoic fauna’s slow metabolisms cannot keep pace and their oxygen needs increase much faster than modern fauna’s,” Sperling explained.
In contrast, modern marine species like bivalves, fish, and sea urchins have higher metabolic demands but more efficient respiratory systems. Brachiopods have almost no meat, Sperling said, comparing them to bivalves. This is why we eat clam chowder and we don’t eat brachiopod chowder. Before the extinction, brachiopods outnumbered bivalves. Sperling compared this dramatic ecological shift to the extinction of the non-avian dinosaurs 65 million years ago, “where mammals essentially took over and never gave up that niche to reptiles again.”
As temperatures rose, brachiopods struggled to meet their oxygen needs, while bivalves and fish adapted more effectively. “The modern advantage: Mobile, athletic animals like bivalves and fish require much more oxygen at a minimum.”
A Warning for Today’s Climate Crisis
Today’s oceans are already losing oxygen, and marine species are facing similar stressors as those 252 million years ago. “Understanding how Earth and Earth’s biota responded back then could inform us of what’s to come,” he said.
The researchers emphasize that while the Permian-Triassic extinction was triggered by natural volcanic activity, today’s crisis is driven by human actions. “Unlike during the Permian-Triassic extinction, we have direct control over the carbon emissions driving this crisis,” Sperling said. “The good news is, we’re still at the point where we can change things and do something about it,” he added.
The Broader Implications: From Ancient Oceans to Modern Ecosystems
The study also sheds light on the long-term reshaping of marine ecosystems. After the Great Dying, the dominance of slow-moving, filter-feeding organisms gave way to more active, mobile species. “Before the extinction, brachiopods greatly outnumbered bivalves.”
The research highlights the fragility of ecosystems under rapid environmental change. “This study is really the final nail in the coffin for what caused the Permian-Triassic mass extinction,” Sperling said. The findings underscore the importance of understanding how species respond to climate stressors. “The biggest mass extinction of all time started from a world that is very similar to today,” he added. “Understanding how Earth and Earth’s biota responded back then could inform us of what’s to come.”
As global temperatures continue to rise, the lessons from the Great Dying become increasingly urgent. The study provides a roadmap for predicting which marine species are most vulnerable to climate change. “Our findings show that, across different organism groups, extinctions happened at much higher rates for those more vulnerable to increases in water temperature and decreases in oxygen availability,” Marquez said. The research serves as both a historical account and a warning for the future.
For readers, the study offers a clear connection between ancient history and modern challenges. The Permian-Triassic extinction is not just a relic of the past—it is a cautionary tale. “The biggest mass extinction of all time started from a world that is very similar to today,” Sperling said. “Understanding how Earth and Earth’s biota responded back then could inform us of what’s to come.” As the planet warms, the lessons from the Great Dying may determine the fate of marine life.
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