Newly-found chemicals in fossil plants reveal UV-B radiation caused Permian mass extinction

Longer-lasting impacts on the entire Earth System

Even more far-reaching and long-lasting effects on the entire Earth System may result from elevated UV-B levels. Increased UV-B exposure decreases plant biomass and land carbon storage, which would accelerate global warming, according to recent modeling studies. In addition to making plant tissue less easily digested due to the increased phenolic chemical concentration, this creates an even more unfriendly environment for herbivores.

“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 the volume of nutritious food sources available for animals,” co-study author Dr. Des Fraser said.

The study was published in Science Advances on January 6.

Study abstract:

Land plants can adjust the concentration of protective ultraviolet B (UV-B)–absorbing compounds (UACs) in the outer wall of their reproductive propagules in response to ambient UV-B flux. To infer changes in UV-B radiation flux at Earth’s surface during the end-Permian mass extinction, we analyze UAC abundances in ca. 800 pollen grains from an independently dated Permian-Triassic boundary section in Tibet. Our data reveal an excursion in UACs that coincide with a spike in mercury concentration and a negative carbon-isotope excursion in the latest Permian deposits, suggesting a close temporal link between large-scale volcanic eruptions, global carbon and mercury cycle perturbations, and ozone layer disruption. Because enhanced UV-B radiation can exacerbate the environmental deterioration induced by massive magmatism, ozone depletion is considered a compelling ecological driver for the terrestrial mass extinction.


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