Ozone Layer Depletion Caused Mass Extinction On Earth, Which May Repeat Say Scientists

Around 359 million years ago, there was a mass extinction of terrestrial life forms on Earth, and it all happened due to ozone layer depletion.

Much of the prevailing forest ecosystems and species of fish and tetrapods were killed during the last great mass extinction event.

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To date, the event was unexplained for its causes. Now scientists say that the mass extinction was caused by harmful UV-B radiation that entered the Earth due to a reduced ozone layer.

Researchers at the University of Southampton have found out that the mass extinction at the transition of Earth from Devonian to Carboniferous (geological time periods) was ¡°coincident with a major climatic warming.¡± The warming ended an intense Devonian glacial cycle but with it, caused the reduction of the ozone layer.

Scientists analysed the rocks dating back to the time to conclude that, unlike other mass extinctions, volcanic eruptions were not the reason for this mass extinction.

Such an extinction mechanism has been ¡°newly discovered¡± as per the scientists and has serious consequences for Earth in today¡¯s time, with global warming on the rise.

Ozone layer experiment

Researchers at the University of Southampton taking samples in Spitsbergen. (Image: Sarah Wallace-Johnson/ SciTechDaily)

The team collected rock samples from the ice-capped and steep mountains of East Greenland as well as from the Andean Mountains above Lake Titicaca in Bolivia.

While the former region was located in the southern hemisphere in the Devonian period, the latter was much closer to the Earth¡¯s south pole at the time.

The variation thus helped scientists judge what was happening at different locations at the time of the mass extinction.

The team then dissolved the rocks in hydrofluoric acid, thus releasing microscopic plant spores, preserved in the cold climate for hundreds of millions of years. When the scientists examined these samples under a microscope, they found bizarre spines on the surface of many of the spores.

This was concluded to be a sign of a damaged DNA because of exposure to UV radiation. Many spores had even developed dark pigmented walls as a protection from the high UV levels.

Ozone layer importance for life

Helicopter leaving the team on Rebild Bakker, East Greenland. (Image: John Marshall/ SciTechDaily)

The mass extinction was thus, not caused by any geological event on Earth but due to high UV radiations on the planet, indicating a collapse in the ozone layer for a brief period. In this period, a huge portion of the prevailing life on Earth died to due to exposure to harmful levels of UV radiation.

The study is significant in a crucial aspect. Scientists warn that this is a fundamental aspect of planet Earth. Whenever it becomes too hot, its ozone layer is considerably depleted, allowing harmful UV radiations to enter the Earth¡¯s atmosphere.

Now published in the journal Science Advances, the study concludes ¡°ozone loss during rapid warming is an inherent Earth system process with the unavoidable conclusion that we should be alert for such an eventuality in the future warming world.¡±