Paratethys the largest lake in Earth’s history would have disappeared completely due to four catastrophic cycles linked to climate change. Paratethys, born as a branch of the Tethys ocean about 155 million years ago, extended, during the geological epoch of the Cretaceous, from the river basin to the Aral Sea. Yet about 6.8 million years ago, two new studies reveal, it nearly disappeared due to climate mutations, killing a significant number of species that lived within it and forcing a large migration of megafauna, the ancestors of giraffes and elephants of today, to Africa.
The paleo-geographer’s analysis revealed the troubled history of this mega-lake Dan Palcu of the University of São Paulo, which through the study of fossil finds, sedimentary deposits and the geology of the area around the Black Sea (in the center of where the megalago of Paratethys was located) has reconstructed the vicissitudes of this important transformation, identifying both the tectonic movements that contributed to its formation and the four main drops in the water level of Paratethys. The most serious was the last, which occurred between 7.65 million and 7.9 million years ago, during a dry period known as the Great Kherson Drying.
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During this episode, the water levels of Lake Paretide plummeted by as much as 250 meters, separating the megalago into mini lakes that are probably toxic to most aquatic life due to the high concentration of salt and other harmful sediments in high concentrations for the living species. Along the coasts a sudden desert emerged, born in a few thousand years from the remains of the sea of Paretetide, which could have lost up to 70% of its surface and up to a third of its volume.
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“It must have been a post-apocalyptic prehistoric world, an aquatic version of the Mad Max wastelands,” says the geologist. Wout Krijgsman of Utrecht University who took part in Dan Palcu’s study. The body of water in its moment of maximum expansion would have covered an area of about 2.8 million square kilometers, retaining more than 10 times the amount of fresh water found today in the lakes of the planet.
From the water to the prairies
Another study shows how the lowering of water levels around the Sea of Paratethys has transformed the previously submerged areas into grasslands, providing fertile ground for the evolution of many terrestrial mammals. According to evolutionary biologist Madelaine Böhme of the University of Tübingen, when water levels fell due to climate change, these grasslands became hot spots for evolution. The migrations of the new species, pushed by further periods of drought (to which they would gradually get used to), would have formed the basis of the biodiversity of the African savannah.
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Paleogeography, a branch of science that studies the earth’s conformation in past ages, is one of the sciences committed to making people understand how climate change can cause important terrestrial upheavals. “The wider impacts and implications of these hydrological crises, particularly beyond the Paratethys area, are still poorly understood,” writes Dan Palcu. But paleogeographic studies investigating the earth’s past can tell us a lot about the scenarios of water scarcity and terrestrial transformation caused by the fastest (man-made) climate change ever recorded by scientists in the last 800,000 years.
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