CO2 blamed for greatest extinction in Earth history

(ORDO NEWS) — The researchers first built a large-scale geochemical model, which has allowed to recover the events, preceding the Great Permian extinction 252 million years ago.

Scientists are still debating the events that led to some of the mass extinctions. Now geochemists have finally reconstructed the chain of events that led to the Great Permian Extinction.

There have been many mass extinctions in Earth’s history. But only five of them are considered to be the most ambitious. As a result of these events, more than half of the species of animals and other organisms that inhabited the planet died out. But even one of them stands out – the largest – mass extinction, which occurred about 252 million years ago and was named Permian, as it happened on the border between the Permian and Triassic geological periods.

The Permian extinction lasted 60 thousand years and as a result, 96% of marine and 70% of terrestrial species of living organisms died. Researchers from Germany, Italy and Canada published a new work in which they tried to reconstruct all the events that led to the death of such a huge number of species in a relatively short period of time.

As the main material for their work, scientists used the shells of fossil brachiopods – mollusc-like organisms that have lived on Earth for more than 500 million years. Researchers were able to analyze well-preserved brachiopod fossils from the Southern Alps, which carried information in their shells about environmental conditions shortly before and at the beginning of the extinction.

By measuring various isotopes of the element boron in fossil shells, the team was able to trace the change in values pH – acidity index – in the ocean 252 million years ago. In ocean water, this indicator is directly related to the dissolved carbon dioxide in it: the more CO 2 in the water, the lower the pH and the more acidic the environment. With an increase in the acidity of the environment, it becomes more difficult for organisms to live in it and ultimately they die out.

Using this technique, scientists were able not only to reconstruct changes in CO 2 concentrations in the atmosphere, but also to clearly trace their relationship with volcanic activity. Then the authors used a computer model that allowed them to recreate the geochemical processes that took place at that time.

Modeling results showed that ocean warming and acidification due to volcanic emissions of carbon dioxide into the atmosphere were already fatal and led to the extinction of marine calcifying organisms at the beginning of the extinction. However, this event increased the greenhouse effect and accelerated the flow of nutrients from land to the ocean. As a result, too much concentration of various compounds led to a decrease in the oxygen concentration in the ocean and an even greater increase in water temperature.

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