How climate change choked ancient life to death — and why it could happen again

Permian-Triassic extinction

An artist’s conception shows the desolation caused by the Permian-Triassic extinction more than 250 million years ago. (LPI / USRA Illustration)

Scientists say rapidly warming oceans played a key role in the world’s biggest mass extinction, 252 million years ago, and could point to the risks that lie ahead in an era of similarly rapid climate change.

The latest analysis, published in this week’s issue of the journal Science, puts together computer modeling of ancient ocean conditions and a close look at species characteristics to fit new pieces into a longstanding puzzle: What were the factors behind the Permian-Triassic mass extinction, also known as the Great Dying?

The Permian-Triassic die-off dwarfed the extinction event that killed off the dinosaurs almost 190 million years later. About 70 percent of land-based species became extinct, but the toll was even greater in Earth’s seas. An estimated 96 percent of marine species were snuffed out.

One leading factor was a rash of volcanic eruptions in a region known as the Siberian Traps, which contributed to an increase in atmospheric greenhouse-gas levels. That contributed to a runaway warm-up in the oceans as well, probably fueled in part by a release of undersea methane.

To tease out the impact of warming oceans on ancient species, a team of researchers from the University of Washington and Stanford University ran computer models of ocean conditions and animal metabolism, and checked the results against the traits seen in ancient fossils as well as in modern-day species.

“This is the first time that we have made a mechanistic prediction about what caused the extinction that can be directly tested with the fossil record, which then allows us to make predictions about the causes of extinction in the future,” principal study author Justin Penn, a UW doctoral student in oceanography, said in a news release.

The computer modeling showed that the warmer oceans lost about 80 percent of their oxygen. About half of the ocean seafloor, mostly at deeper depths, became completely oxygen-free.

What effect would those conditions have had on marine species? Penn and his colleagues began by matching up the ancient conditions with the traits of 61 modern-day marine species that parallel creatures from the Permian era, ranging from corals to sharks.

They found that the effects of oxygen depletion would have dealt the gravest blow to species living far from the tropics. The species that had the best chance of survival were the ones …read more

Source:: GeekWire

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