In new research, paleontologists analyzed abundances of sunscreen-like chemicals in 800 fossil pollen grains from 250-million-year-old rocks in Tibet.
The impacts of ozone depletion and elevated UV-B levels on the terrestrial ecosystem. Image credit: Conor Haynes-Mannering, University of Nottingham.
The end-Permian mass extinction is the largest mass extinction event in Earth’s history.
Also known as the Permian-Triassic extinction event and the Great Dying, it occurred about 252 million years ago.
The end-Permian mass extinction killed off nearly 96% of all marine species and 70% of terrestrial vertebrate species on the planet over the course of thousands of years.
This catastrophic loss of biodiversity was a response to a paleoclimate emergency triggered by the emplacement of a continental-scale volcanic eruption that covers much of modern-day Siberia.
The volcanic activity drove the release of massive amounts of carbon that had been locked up in Earth’s interior into the atmosphere, generating large-scale greenhouse warming.
Accompanying this global warming event was a collapse in the Earth’s ozone layer.
Support for this theory comes from the abundant occurrence of malformed spores and pollen grains that testify to an influx of mutagenic UV irradiation.
“Plants require sunlight for photosynthesis but need to protect themselves and particularly their pollen against the harmful effects of UV-B radiation,” said University of Nottingham’s Professor Barry Lomax, co-author on the study.
“To do so, plants load the outer walls of pollen grains with compounds that function like sunscreen to protect the vulnerable cells to ensure successful reproduction.”
“We have developed a method to detect these phenolic compounds in fossil pollen grains recovered from Tibet, and detected much higher concentrations in those grains that were produced during the mass extinction and peak phase of volcanic activity,” said first author Professor Liu Feng, a researcher at the Nanjing Institute of Geology and Palaeontology.
“Volcanism on such a cataclysmic scale impacts on all aspects of the Earth system, from direct chemical changes in the atmosphere, through changes in carbon sequestration rates, to reducing volume of nutritious food sources available for animals,” said Oxford Brookes University’s Dr. Wes Fraser, co-author on the study.
The findings appear in the journal Science Advances.
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Feng Liu et al. 2023. Dying in the Sun: Direct evidence for elevated UV-B radiation at the end-Permian mass extinction. Science Advances 9 (1); doi: 10.1126/sciadv.abo6102
