ETCHED IN FOSSIL

Prehistoric climate change damaged the ozone layer and led to a mass extinction

- JOHN MARSHALL

MASS EXTINCTIONS are very important to how life evolved on Earth. For example, when an asteroid hit the Earth 66 million years ago, the resulting dinosaur extinction led mammals to take their place. My colleagues and I have published new research on the mass extinction that took place 359 million years ago at the boundary between the Devonian and Carboniferous geological periods. There have been many previous speculations as to the cause of this event, including volcanic eruptions, asteroid impacts, climate change, sea level changes, wildfires and the rise of the first forests.

But we have shown that the extinctions on land at this time may have been caused by a catastrophic thinning of the ozone layer that let in damaging levels of ultraviolet radiation. Something similar contributed to the mass extinctions at the end of the Permian and Triassic periods, but these events were caused by volcanic eruptions. Our research suggests the Earth has a natural internal process triggered by a warming climate that can destroy the ozone layer, a serious warning for our own period of climate change.

The Late Devonian extinction played a significant role in the development of vertebrate life. It included the loss of the dominant group of armoured freshwater fish. The survivors were the sharks and the rather minor group of bony fish that subsequently spread out to dominate our younger oceans.