Warming Oceans Threaten Dinosaur-Like Extinction of Marine Life -- but It's Avoidable
If we don't curb carbon emissions, starting today, marine life could be headed toward mass extinction, scientists say.
Monisha RavisettiFormer Science Writer
Monisha Ravisetti was a science writer at CNET. She covered climate change, space rockets, mathematical puzzles, dinosaur bones, black holes, supernovas, and sometimes, the drama of philosophical thought experiments.
Previously, she was a science reporter with a startup publication called The Academic Times, and before that, was an immunology researcher at Weill Cornell Medical Center in New York. She graduated from New York University in 2018 with a B.A. in philosophy, physics and chemistry.
When she's not at her desk, she's trying (and failing) to raise her online chess rating. Her favorite movies are Dunkirk and Marcel the Shell with Shoes On.
About 250 million years ago, global warming killed over 95% of the world's marine species in a tragedy now known as "The Great Dying." In many ways, though, this was an inevitable cataclysm. It was the result of natural volcanic eruptions that heated up oceans, disrupting underwater oxygen supply and suffocating sea dwellers.
On Thursday in the journal Science, researchers said that the current climate crisis could very well be pushing us toward yet another marine mass extinction – one that rivals even the eons-old Great Dying. But, they say, it's avoidable.
Volcanic eruptions aren't the ultimate driver of global warming this time. Human activity is.
The burning of fossil fuels, for instance, is a major contributor to the greenhouse gas emissions that exacerbate climate change – yet it's humanity's primary way of producing heat and electricity. And even though some energy companies are slowly trying to move toward non-fossil-fuel-burning, sustainable energy such as solar power, we still burn a significant amount of fossil fuels. In some countries, the trend even seems to be headed upward.
"If climate change is left unchecked, we could see the emergence of extreme extinctions that set back the diversity of marine life to a time not seen in almost 50 million years," said Justin Penn, a postdoctoral researcher at Princeton University and co-author of the study.
"However," Penn adds, "it is not too late to enact the rapid and aggressive greenhouse gas reductions needed to avoid such outcomes."
A grim, post-2300 Earth
In essence, the team's new study says that if humanity's current rate of greenhouse gas emissions continues as is, we'd see about 4 to 5 degrees Celsius of warming by the year 2100.
By 2300, we'd see upward of 10 degrees Celsius, and that's when, Penn says, we'd see extinctions on par with the "Big Five" mass extinctions in Earth's history. That includes the most recent one, which wiped out the dinosaurs 65 million years ago, and, most notably, the Great Dying that happened in Earth's Permian era.
In fact, Penn's previous research, on what's known as the end-Permian mass extinction, was the motivating factor for his new efforts.
"Similar environmental changes are occurring today as a result of human greenhouse gas emissions," he said. "And so, we wanted to know the implications for extinction risks in the modern ocean."
It's rather jarring to realize that our blue planet is exhibiting environmental conditions akin to the time prior to one of the world's most devastating events. In other words, we might be seeing history repeat itself.
As with the end-Permian calamity, marine species could lose their habitats, suffer from oxygen deprivation, be forced to migrate to places they aren't acquainted with – and therefore can't survive in – and undergo many other grim scenarios. Because of us.
And even though post-2300 will be when any such mass extinction could occur, per the paper, Penn offers a poignant perspective:
"If there is something that can be done to save the only place we call home, shouldn't we do everything we can to act on that?"
What can we do?
Next to their ominous scenario in which a giant percentage of marine creatures die within the next few centuries, Penn and fellow researcher Curtis Deutsch of the National Science Foundation offer a glimmer of hope – albeit one that requires immediate action by politicians, businesses and other people or organizations with enough power to combat the crisis.
As Penn puts it, it's the case where we "collectively get our acts together and reverse our emissions trends to keep global warming from continuing much further."
From 65 countries, 278 scientists banded together and figured out how humanity's carbon emissions can be halved by 2030. However, to keep in line with the Paris Agreement's goal of limiting global warming to 1.5 or 2 degrees Celsius, the IPCC says 2025 – at the latest – has to be when our emissions peak. All that means is that from then on, our level of carbon emissions must head downhill.
Further, individual scientists are also on a quest to learn how we can limit carbon emissions. One team's climate model released in the journal Nature, for instance, found a way to limit warming to below the 2-degree mark by 2100.
But remember, this is all theoretically possible. We still have to put these plans into action.
Though if, and perhaps only if, we can follow any of these pathways to climate change mitigation, drastic projections – like the new study's – could be removed from humanity's timeline. More specifically, the study explains that the projected marine extinction risk would likely be reduced by about 70%.
Meaning, no modern Great Dying.
Marine devastation from all directions
In a way, the new study's marine mass extinction projections are underestimations. Things could, in truth, be a lot worse, considering all the other factors that threaten the lives of our underwater friends. That includes human stressors like overfishing, pollution and seafloor mining, Penn says
"These effects would add to or even amplify the extinctions we studied from climate warming, but we currently don't have a good way to include them in our models," Penn said. "So, in that light, the extinctions we project from climate warming should be thought of as conservative."
"Efforts to reduce other impacts on ocean ecosystems, from overfishing and pollution, for example, are also critical, even if we stop climate change," Penn said, though stressing, "even more so if we don't."