A new study has found that plants produced compounds that function like sunscreen to protect themselves from harmful ultraviolet (UV-B) radiation during the end-Permian mass extinction event, which occurred 250 million years ago and resulted in the loss of approximately 80% of marine and terrestrial species.
An international team of researchers have discovered that pollen preserved in 250 million year old rocks contains compounds that act as sunscreen. These compounds are produced by plants to protect themselves from harmful ultraviolet (UV-B) radiation. The findings suggest that a surge of UV-B played a significant role in the end Permian mass extinction event, which resulted in the loss of around 80% of marine and terrestrial species.
The research, conducted by scientists from the University of Nottingham, China, Germany and the UK, was led by Professor Liu Feng from the Nanjing Institute of Geology and Palaeontology. The team developed a new method to detect plant sunscreen-like compounds in fossil pollen grains, and their findings were published in Science Advances.
The end-Permian mass extinction event occurred 250 million years ago and is considered the most severe of the five major mass extinction events. It was caused by a palaeoclimate emergency triggered by a massive volcanic eruption in Siberia, which released a large amount of carbon from Earth’s interior into the atmosphere and caused global warming. The event also resulted in a collapse of the Earth’s ozone layer. Evidence for this theory can be found in the abundance of malformed spores and pollen grains, which suggest an influx of mutagenic UV radiation.
Professor Barry Lomax from the University of Nottingham explained that plants need sunlight for photosynthesis, but they must also protect themselves and their pollen from the harmful effects of UV-B radiation. To do this, plants load the outer walls of pollen grains with compounds that act as sunscreen to protect the vulnerable cells and ensure successful reproduction. Professor Liu Feng added that their research showed higher concentrations of these phenolic compounds in fossil pollen grains recovered from Tibet that were produced during the mass extinction and peak phase of volcanic activity.
Elevated UV-B levels can have even further-reaching and longer-lasting impacts on the Earth system. Recent modeling studies have demonstrated that elevated UV-B stress reduces plant biomass and terrestrial carbon storage, which can exacerbate global warming. The increased concentration of phenolic compounds also makes plant tissue less digestible, making the environment even more challenging for herbivores.
Summarizing the group’s findings, Dr. Wes Fraser from Oxford Brookes University said that volcanism on such a catastrophic scale impacts all aspects of the Earth system, including changes in the atmosphere, carbon sequestration rates, and the availability of nutritious food sources for animals.