Climate change was killing Karoo inhabitants 250 million years ago


THE eerie Karoo landscape has once again opened up like a treasure trove to reveal some of the biggest and oldest secrets on — and about — the Earth.

WOMAN ON A MISSION: Pia Viglietti Picture: Wits University

Dr Pia Viglietti, of the Evolutionary Studies Institute at the University of the Witwatersrand, has discovered that long before a mass extinction event 250 million years ago, climate change was already erasing species.

This showed the devastating effect of “the runaway greenhouse effect”, Viglietti told TimesLIVE. But back then it was a natural event.

“It is in our hands to mitigate the damage we are causing [by filling the atmosphere with carbon dioxide], whereas the animals at that point couldn’t do anything about it,” she said.

The mass extinction event wiped out 96% of marine species and 70% of terrestrial vertebrate species, and the Karoo became a basin filled with fossils — including those of marine animals — in its vast amount of sediment.

Viglietti studied the sediments deposited during the creation and changes of the once grand Gondwanides, a mountain range so massive millions of years ago that it would have dwarfed the Andes in South America. Today’s mountains around Cape Town are remnants from that range.

Formed by the shifting of tectonic plates (slabs of rock that form earth’s hard and rigid shell), the looming mountain range then made its mark on the land, the climate and all living things.

“The Gondwanides not only influenced how and where rivers flowed [depositing sediment], it also had a significant effect on the climate, and thus the ancient fauna of the Karoo Basin,” said Viglietti.

“Within the last million years before this major biotic crisis, the animals had already started to react. I interpret this faunal change as resulting from climatic effects relating to the mass extinction event – only occurring much earlier than previously identified.”

Her groundbreaking research, published in Nature Scientific Reports, comes two years after researchers at the institute used Karoo rocks to shed light on the mass extinction event.

That project, led by Dr Michael Day, dispelled theories that land and sea animals died out at different times.

Said Viglietti: “The Karoo Basin takes up a huge portion of South Africa and most of us who drive through it do not think much of it. But if you know what you’re looking for, the Karoo represents a wealth of knowledge about the story of life on Earth.”

– TimesLIVE

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