The ozone layer was destroyed during the Permian mass extinction event

Fossils indicate that at the end of the Permian period, plants were producing higher levels of sunscreen chemicals to protect against higher levels of UV rays.

Along Michael Le Paige

It has long been suspected that the end-Permian mass extinction 250 million years ago destroyed much of the atmospheric ozone layer that protects life from ultraviolet radiation. Now we have the first direct evidence of that.

Phil Jardine and his colleagues at the University of Münster, Germany, have shown that pollen grains and spores from this period contain higher levels of “sunscreen” chemicals than those from earlier or later periods. rice field.

“This was only seen at one point in time, which is consistent with the end-Permian extinction,” says Jardine.

At the end of the Permian period, about 90% of marine life and 70% of terrestrial life became extinct. The mass extinction is believed to have been caused by a period of unusually high volcanic activity. The lava flow heated other rocks, including coal, and released large amounts of gases such as carbon dioxide. This caused ocean acidification and global warming, reducing ocean oxygen levels.

This explains why marine life was hit so hard, but it’s less clear why so many terrestrial animals went extinct. One possibility is that the halocarbons released by the eruption destroyed the ozone layer much like the chlorofluorocarbons (CFCs) used as refrigerants in the 20th century, leading to higher levels of harmful ultraviolet (UV) radiation. That’s what it means.

Previous studies have shown an increase in abnormally shaped pollen grains and spores at this time. This could be due to mutations caused by ultraviolet light. But these anomalies could also be the result of many other toxic substances released during the eruption, says Jardine. says.

So his team used a technique called Fourier transform infrared microspectroscopy to measure levels of UV-absorbing chemicals in fossilized pollen grains and spores from Tibetan rocks. The oldest rock layers were deposited hundreds of thousands of years before the extinction, and the youngest rock layers were deposited hundreds of thousands of years later, Jardine said.

Conservation levels of sunscreen chemicals should be similar throughout this rock sequence. So the increase during the mass extinction must be because plants were producing more of them, he says.

Higher UV levels have had a cascading effect on ecosystems as terrestrial plant growth has declined and herbivores and predators have starved. would have been smaller than

The same thing would have happened today had countries not agreed to phase out CFCs under the 1987 Montreal Protocol.

“Modeling studies suggest that by the 2060s, without the Montreal Protocol, there would be massive ozone depletion and decay,” says Jardine. “Hopefully we’ve avoided it. This kind of agreement and environmental protection is really important.”