Tropical greenery once blanketed the supercontinent of Pangea, recycling carbon and regulating climate. Then, 252 million years ago, those forests collapsed – and with them, Earth’s primary brake on rising CO2.
A new study led by researchers at the University of Leeds and China University of Geosciences shows that the disappearance of lush low-latitude vegetation after the Permian–Triassic Mass Extinction.
This collapse triggered a climate feedback so powerful that “super-greenhouse” conditions persisted for roughly five million years.
Scientists have long linked the “Great Dying” – in which more than 90 percent of marine species and around 70 percent of land vertebrates vanished – to colossal eruptions in Siberia.
Those outbursts released enough carbon dioxide to roast the planet. However, geologic evidence indicates that temperatures remained punishingly high long after the lava stopped flowing.
The missing piece, say the authors, is what happened to tropical forests once temperatures and acid rain soared.
“Critically, this is the only high-temperature event in Earth’s history in which the tropical forest biosphere collapses, which drove our initial hypothesis,” explained Zhen Xu from the University of Leeds, who led the project.
“Now, after years of fieldwork, analysis, and simulations, we finally have the data which supports it.”
Using detailed fossil plant records from dozens of Chinese rock sections – among the most complete archives of the Permian–Triassic transition – Xu and colleagues reconstructed how photosynthetic productivity waxed and waned.
Their analysis dovetailed with climate-carbon cycle models, revealing that once the forests disappeared, natural carbon sequestration plunged. Without vegetation to absorb CO2, volcanic emissions lingered, intensifying heat and delaying Earth’s recovery.
China’s rugged outcrops hold a near-continuous record of sediment laid down across the extinction interval. Three generations of Chinese geologists have cataloged that history.
Since 2016, Xu’s team has added thousands of new plant fossils and geochemical samples from across Earth. They trekked to sites reachable only by boat or horseback.
The resulting dataset captures a sharp, continent-wide shift from luxuriant, fern-rich swamp forests to sparse, shrubby landscapes within a geologic eye-blink.
Those observations fed into computer models developed at Leeds. By tweaking the fraction of global photosynthesis lost, Professor Benjamin Mills and Xu tested whether reduced carbon uptake alone could account for the five-million-year thermal plateau. The numbers lined up.
“There is a warning here about the importance of Earth’s present-day tropical forests,” Mills said.
“If rapid warming causes them to collapse in a similar manner, then we should not expect our climate to cool to pre-industrial levels even if we stop emitting CO2,” he said. “Indeed, warming could continue to accelerate in this case even if we reach zero human emissions.”
Because plants build their tissues out of atmospheric carbon, verdant ecosystems act as vast reservoirs, locking CO2 away in wood and soils. Destroy that biomass – through heat, drought, fire, or acid rain – and the storage vanishes.
The researchers argue the Permian event marks a clear instance of a climate–biosphere tipping point. Falling forest cover triggered carbon feedbacks that locked the planet into a hotter state until vegetation slowly returned.
That idea dovetails with modern concerns. Today’s Amazon and Congo basins absorb billions of tons of CO2 annually, yet warming, deforestation, and wildfires are eroding their capacity. The ancient past shows how abruptly the system can flip.
The study also illustrates how paleontology is evolving. Analyzing ancient crises now demands chemical tracers, numerical simulations, and high-resolution global mapping – tools far removed from the dusty image of fossil hunting.
“Paleontology needs to embrace new techniques – from numerical modeling to interdisciplinary collaboration – to decode the past and safeguard the future,” said co-author Hongfu Yin, a professor at the China University of Geosciences, who began collecting these Permian fossils decades ago.
“Let’s make sure our work transcends academia: it is a responsibility to all life on Earth, today and beyond. Earth’s story is still being written, and we all have a role in shaping its next chapter,” added co-author Jianxin Yu, a professor at the same university.
While humans are unlikely to unleash Siberian-scale lava floods, we are replicating the CO2 spike in real time. The Great Dying shows how ecosystem failure can prolong climatic damage far beyond the initial trigger.
In the Permian, recovery took millions of years; for modern civilization, even centuries of persistent warming would strain food supplies, economies, and biodiversity.
“The causes of such extreme warming during this event have been long discussed, as the level of warming is far beyond any other event,” Xu notes.
Her team’s evidence suggests that the planet’s thermostat can jam, and forests are a key component of the mechanism. Preserve them, and they buffer shocks. Lose them, and the heat may keep climbing long after emissions fall.
The ancient fossils of China thus deliver a double message: Earth has crossed tipping points before, and those thresholds hinge on living landscapes. Protecting today’s tropical forests might be the surest way to avoid replaying a five-million-year fever.
The study is published in the journal Nature Communications.
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