The Great Dying or the Permian-Triassic Extinction Event was the largest extinction in Earth's history. This cataclysmic mass slaughter, which occurred some 252 million years ago, wiped-out about 96 percent of all marine species worldwide.
In addition to annihilating marine life, The Great Dying also destroyed 70 percent of terrestrial vertebrate species. It is the only known event that led to the mass extinction of insects. It also caused 57 percent of all biological families and 83 percent of all genera to become extinct.
Scientists have long debated the exact cause or causes of this terrifying extinction. Among the hypothesis put forth are the high acidity of ocean water; a complete lack of oxygen; metal and sulfide poisoning and warmer temperatures.
Now, a new study concludes The Great Dying in the oceans was mainly caused by global warming. As a result, the oxygen-starved warmer waters asphyxiated to death almost all marine animals on Earth at the time.
Eye-opening new research from the University of Washington and Stanford University reveal that the Permian-Triassic Extinction Event in the oceans was indeed caused by global warming. Researchers combined models of ocean conditions and animal metabolism with published lab data and paleoceanographic records to reach this startling conclusion.
Research showed that as worldwide temperatures increased and the metabolism of marine animals sped-up, the warmer waters were unable to hold enough oxygen for marine animals to survive. This finding is eerily similar to the global ocean warming occurring today.
This is the first time we have made a mechanistic prediction about what caused the extinction that can be directly tested with the fossil record, said first author Justin Penn, a UW doctoral student in oceanography. In the future, this discovery allows researchers to make predictions about the causes of extinction.
Researchers ran a climate model with Earth's configuration during the Permian Period, when the land masses combined to form the supercontinent, Pangaea. Oceans had temperatures and oxygen levels similar to today's before ongoing volcanic eruptions in Siberia created a greenhouse-gas planet.
Researchers then raised greenhouse gases in the model to the level required to make tropical ocean temperatures at the surface some 10 degrees Celsius higher, matching conditions at that time.
As a result, oceans lost about 80 percent of their oxygen. Close to half the oceans' seafloor, mostly at deeper depths, were completely deprived of oxygen. The fossil record confirms species located farther from the Equator were almost completely annihilated during the event.
The signature of that kill mechanism, climate warming, and oxygen loss, is this geographic pattern that's predicted by the model and then discovered in the fossils, said Penn. This confluence indicates the mechanism of climate warming and oxygen loss was a primary cause of The Great Dying.
