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Ozone layer erosion 360 million years ago led to a mass extinction event that wiped out much of the Earth's plants and freshwater animals - and scientists warn it could happen again

  • The team found evidence of the impact of ultraviolet radiation in rock samples 
  • They say that the Earth rapidly warmed up at the time of the ozone breakdown 
  • Authors say this could happen again as temperatures rise due to climate change

A mass extinction 360 million years ago that killed off many of the Earth's plants and freshwater animals was caused by ozone layer erosion and it could happen again.
Scientists from the University of Southampton found evidence that it was high levels of ultraviolet radiation that destroyed the ancient forest ecosystem.

This newly discovered extinction mechanism was caused by changes in the Earth's temperatures and climate cycle - this led to the deadly ozone breakdown. Study authors warn that we could face a similar scenario as we head towards similar global temperatures that existed 359 million years ago due to climate change.

They dissolved the rocks in hydrofluoric acid, releasing microscopic plant spores preserved for hundreds of millions of years. Many had bizarrely formed spines in response to UV radiation (right) when compared to normal spores (left 

Lead researcher Professor John Marshall said: 'Current estimates suggest we will reach similar global temperatures to those of 360 million years ago, with the possibility that a similar collapse of the ozone layer could occur again.'
He added that if this happens it would result in 'exposing surface and shallow sea life to deadly radiation.'
'This would move us from the current state of climate change, to a climate emergency.'

 Prof John Marshall (left), taking samples in Spitsbergen. Those samples helped them discover pores that were damaged by UV radiation

As part of the research Marshall and colleagues found that the ozone shield - that protects the Earth from harmful UV radiation - vanished for a short period of time.

He said when it vanished it coincided with a brief and quick warming of the Earth.

'Our ozone layer is naturally in a state of flux - constantly being created and lost - and we have shown this happened in the past too, without a catalyst such as a continental scale volcanic eruption.'

The scientists found evidence that high levels of UV radiation destroyed forest ecosystems and killed many species of fish and tetrapods.

This was at the end of the Devonian geological period, 359 million years ago.

Other types of mass extinctions include an asteroid hitting the Earth 66 million years ago causing dinosaur extinction and a huge scale continental volcanic eruption that destabilised the Earth's atmosphere and ocean 252 million years ago.

The team discovered that this damaging burst of UV radiation occurred as part of one of the Earth's climate cycles, rather than by a huge volcanic eruption.

They found that the ozone collapse occurred as the climate rapidly warmed following an intense ice age.

Study authors warned that the Earth could reach similar temperatures, triggering a possible extinction event on the same scale - if something isn't done to slow the pace of climate change.

The team collected rock samples from mountainous polar-regions in East Greenland, the lake was situated in the Earth's southern hemisphere 350 million years ago.

At the time the lake would have been similar in nature to modern day Lake Chad on the edge of the Sahara Desert.

Other rocks were collected from the Andean Mountains above Lake Titicaca in Bolivia - these South American samples were from the southern continent of Gondwana, which was closer to the Devonian South Pole.

They dissolved the rocks in hydrofluoric acid, releasing microscopic plant spores, like pollen, but from fern-like plants that didn't have seeds or flowers.

These spores have lain preserved in rocks for hundreds of millions of years.

The scientists found many of the spores had bizarrely formed spines on their surface - a response to UV radiation damaging their DNA.

Many spores had dark pigmented walls believed to be a 'protective tan' due to increased and damaging UV levels.

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