Wildfires may have been a key contributor to the total collapse of land ecosystems during Earth’s worst mass extinction event more than 250 million years ago.
This discovery by a paleontologist based at University College Cork (UCC), working in collaboration with scientists at the Swedish Museum of Natural History, was made by studying fossil plant and charcoal records in Australia and Antarctica.
Their findings also highlight how “today’s wetlands are also drying at an alarming rate, and wildfires have eliminated vast numbers of animals and plants” throughout Planet Earth.
In a paper published in PALAIOS on Thursday, the researchers ask if the planet is currently on the path to a similar mass extinction.
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They examined the “end-Permian mass extinction” that eliminated almost every species on Earth, with entire ecosystems collapsing, and discovered a sharp spike in wildfire activity from this most devastating of mass extinctions.
Promoted by rapid greenhouse gas emissions from volcanoes, extreme warming and drying led to wildfires across vast regions that were previously permanently wet, explained lead author Dr Chris Mays of UCC.
“Instead of capturing carbon from the atmosphere, these wetlands became major sources of atmospheric carbon, enhancing the sharp warming trend,” he added — not unlike a scenario unfolding today.
By studying fossil plant and charcoal records of the Sydney & Bowen Basins in eastern Australia and Lambert Graben in Antarctica, they discovered wetlands were regularly disturbed by fires leading up to the extinction event.
In response, plants had evolved a range of fire-coping mechanisms. However, the severe climate change and peak in fire activity during the extinction event seems to have pushed even these fire-adapted plants over a tipping point, from which the entire ecosystem could not recover for millions of years.
“Sifting through the fossil plant records of eastern Australia and Antarctica, we found high abundances of burnt, or charcoalified, plants throughout the late Permian Period. From this high baseline, charcoal abundances reached a prominent peak right at the top of the last Permian coal beds, indicating a major but short-lived increase in wildfires,” Dr Mays said.
This was followed by “low charcoal” for the next three million years of the Early Triassic Period, he noted. “It was an end-Permian burnout, followed by an Early Triassic depression.”
In today’s world, the researchers highlight “wildfires have caused shocking mass animal die-offs in several regions around the world” — notably in California during 2018 and 2020, and in Australia in 2019 and 2020.
Ireland currently has 45 sites designated as “wetlands of international importance” with a surface area of 67,000 hectares (670 km2), though much of its peatlands are in poor condition having being exploited for turf production, and in urgent need of rewetting so they can store carbon rather than emit it.
Our more recent warming global climate has led to prolonged droughts and increased wildfires in typically wet habitats, such as the peat forests of Indonesia and the vast Pantanal wetlands of South America.
These major “carbon sinks” ― regions of natural capture of carbon from the atmosphere ― are crucial in the fight against climate change. As the fossil record reveals, without these regions of carbon capture, the world can stay intolerably warm for hundreds of millennia, Dr Mays said.
The potential for wildfires as a direct extinction driver during “hyperthermal events, rather than a symptom of climatic changes” deserves further examination, he believed.
“Unlike the species that suffered the mass extinctions of the past, we have the opportunity to prevent the burning of the world’s carbon sinks and help avoid the worst effects of modern warming,” he underlined.
