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Study: Only Rapid Action Can Avert Worst Marine Extinction in 250 Million Years

Reversing greenhouse gas emissions trends would diminish extinction risks by more than 70 percent, researchers found.

In 2021, ocean temperatures were the highest ever recorded for the third consecutive year.

Research published Thursday in the journal Science warns that runaway global warming driven by carbon dioxide emissions has put marine life at risk of the most catastrophic mass extinction since the “Great Dying” 250 million years ago, when 90% of all ocean species were wiped out.

Using models of varying emissions scenarios, Princeton University scientists Curtis Deutsch and Justin Penn found that the continued burning of fossil fuels and “business-as-usual global temperature increases” are likely to result, by 2300, in mass extinctions of marine systems “on par with past great extinctions.”

“With accelerating greenhouse gas emissions, species losses from warming and oxygen depletion alone become comparable to current direct human impacts within a century and culminate in a mass extinction rivaling those in Earth’s past,” the researchers write. “Polar species are at highest risk of extinction, but local biological richness declines more in the tropics.”

While their findings are dire, Deutsch and Penn go out of their way to emphasize that the new research should be a catalyst for “rapid action,” not despair.

“Reversing greenhouse gas emissions trends would diminish extinction risks by more than 70%, preserving marine biodiversity accumulated over the past ~50 million years of evolutionary history,” they write.

Speaking to the New York Times, Deutsch and Penn explained that the decision to underscore the possibility of averting the most cataclysmic extinction scenario was an active one, leading to a last-minute change in the study’s pre-publication headline: “Marine Extinction Risk From Climate Warming.”

“We were about to send it in and I thought, ‘Gee, it sounds like a title that only has the dark side of the result,'” said Deutsch, a professor of geosciences. “Not the bright side.”

The headline they ultimately landed on — “Avoiding Ocean Mass Extinction From Climate Warming” — centers the element of choice: If humanity acts swiftly to bring carbon emissions into line with the limits set out by the Paris agreement, warming can be dramatically slowed and devastating marine life extinctions can be prevented.

“Our choices have huge impacts,” said Deutsch.

The barriers to the kind of sweeping, global climate action that the scientific evidence demands remain immense, however, as the rich countries most responsible for planet-warming emissions burn fossil fuels at a rate that spells disaster for the future.

In 2021, ocean temperatures were the highest ever recorded for the third consecutive year. Oceans have absorbed over 30% of the carbon dioxide emissions produced by human activity over the past two centuries and 90% of the excess heat.

The consequences for marine life are immense. One study published earlier this year warned that “by 2080, around 70% of the world’s oceans could be suffocating from a lack of oxygen as a result of climate change, potentially impacting marine ecosystems worldwide.”

At the COP26 climate summit in Glasgow late last year, nations adopted a pact stressing the “importance of protecting, conserving and restoring natures and ecosystems, including… marine ecosystems.”

But climate advocates were dismayed by how little concrete action the gathering spurred, given the enormous consequences of failing to slash carbon emissions worldwide.

Malin Pinsky, a Rutgers University biologist, told the Washington Post on Thursday that Deutsch and Penn’s research shows, “If we’re not careful, we’re headed for a future that I think to all of us right now would look quite hellish.”

“It’s a very important wake-up call,” Pinsky added.

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