Scots team solve riddle of Great Dying extinction

An artists impression of what happened to one dinosaur 75 million years ago. Picture: PA

The Permian-Triassic Boundary – also known as the “Great Dying” – took place about 252 million years ago and wiped out more than 90 per cent of marine species and more than two-thirds of land animals.

The oceans absorbed huge amounts of carbon dioxide released by volcanic eruptions, making them highly acidic, researchers at the University of Edinburgh have said in the first study to identify the cause of the mass extinction.

They analysed rocks unearthed in the United Arab Emirates – which were on the ocean floor during the Great Dying – to develop a climate model working out what drove the extinction.

The rocks preserve a detailed record of changing oceanic conditions down the ages.

Increased temperatures and widespread loss of oxygen in the oceans had already put the environment under pressure. But it was ocean acidification that was the driving force behind the deadliest phase of the extinction, dealing a death blow to an already unstable ecosystem,

The amount of carbon added to the atmosphere triggering the mass extinction was probably greater than today’s fossil fuel reserves. This fast rate of release was a critical factor driving ocean acidification.

Oceans can absorb some carbon dioxide but the large volume released, at such a fast rate, changed their chemistry.

The mass extinction of both marine and land-based animals demonstrated that extreme change took place in all of Earth’s ecosystems.

The Permian-Triassic Boundary extinction took place over a 60,000-year period with acidification of the oceans lasting for about 10,000 years.

The findings are helping scientists understand the threat posed to marine life by modern-day ocean acidification linked to greenhouse gas emission.

Dr Matthew Clarkson, of the university’s school of geosciences, who co-ordinated the study published in the journal Science, said: “Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now.

“This is a worrying finding, considering that we can already see an increase in ocean acidity today that is the result of human carbon emissions.”

Professor Rachel Wood, also from the school of geosciences, said: “This work was highly collaborative and the results were only possible because we assembled a unique team of geochemists, geologists and modellers to tackle an important and long-standing problem.”

The study was carried out in collaboration with the universities of Exeter, Leeds, and Cambridge, Bremen and Graz.

Funding was provided by the International Centre for Carbonate Reservoirs, Natural Environment Research Council, the Leverhulme Trust, German Research Foundation and the Marsden Fund.