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How life before the dinosaurs could help us understand the consequences of global warming today

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How life before the dinosaurs could help us understand the consequences of global warming today

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A quarter of a billion years ago, long before dinosaurs or mammals evolved, global warming triggered by massive volcanic eruptions wiped out 96% of the world's species.

The huge volcanoes erupting in Siberia belched thousands of tonnes of carbon dioxide into the atmosphere, setting off a chain reaction that involved global warming, acid rain, and loss of oxygen from the sea bed.

Geologists had already shown that ocean temperatures rose by 10–15 degrees centigrade.

All life on Earth today is descended from the 4% of species that survived the Permian Mass Extinction - nicknamed 'The Great Dying.'

The event was complex, with at least two separate phases of extinction spread over millions of years.

Marine creatures were particularly badly affected and insects suffered the only mass extinction of their history.

How the end-Permian mass extinction, 252 million years ago affected life on land has been uncertain until now.

A new study by Dr Massimo Bernardi and Professor Mike Benton from the School of Earth Sciences at the University of Bristol show how early reptiles were expelled from the tropics.

Ten main lines of reptiles survived the crisis and re-populated the Earth in the subsequent Early Triassic time. 

However, they avoided the tropics, as did fish and other animals in the oceans. 

The tropical clear-out was understood to have lasted several million years, but the new work shows that was not the case:

"They went into the temperate areas and we were able to show they went back and forwards a few times as different phases of warming were happening during the crisis period," Co-author, Professor Benton told Euronews.

"So the crisis was actually strung out over something like 5 million years and there were a number of repeated warming events."

Up to now, only the skeletons of the early reptiles from before and after the crisis were used to study the period, but these are found only in Russia and South Africa, so it is impossible to document any latitudinal shifts.

To make the study as comprehensive as possible, Dr Bernardi and Professor Benton had been building a huge database integrating both skeletal and footprint data, allowing them to fill a lot of the gaps, over Europe and North America."

Co-author, Professor Benton, added: "Our analyses show that the land reptiles moved north by 10 or 15 degrees to escape the tropical heat.

Life on Earth took a while to recover and diversify, significantly longer than after any other extinction event, possibly up to 10 million years.

The following Triassic period was characterised by heat, vast deserts and warm seas, with lush forests growing even in polar regions.

However, along with the lack of other life, this opened up some evolutionary opportunities for the very first mammals and dinosaurs.

By digging deeper into the exact consequences of rapid global warming, the study provides some information that could be useful in the present day:

"The kinds of processes that were going on at the time, 250 million years ago, in terms of gloabl warming and acid rain, ocean acidification, these are familiar to us today." 

"They were on a much bigger scale at that time, but these kind of things can happen repeatedly on the Earth so we need to understand what is the impact on life." Professor Benton told Euronews

"So life eventually recovered, that's a good message. But the less good message is that it took 5 or 10 million years for ecosystems to get re established and for the Earth's climates to settle down, so life could recover in a satisfactory way."

"Whatever we do to the Earth, life in some form will recover,  but we are not likely to be part of it and its not likely to happen in anything like human timescales."

"Recover takes a million years, or in this case, which dug really deep, it takes 5-10 million years. That's longer than humans have been on the Earth."

"So yes, its positive but not in the sense that we will be able to witness any of that."