“So they’re kind of like dark matter,” said paleontologist David Jablonski of the University of Chicago about the sanctuaries, the “refugia” that have never been found in the fossil record, but sheltered the shell-shocked and decimated species of Earth’s past mass extinctions until they were able to repopulate the planet in ensuing eons.
“Where Will the Sanctuaries Be?”
“We think they’re there because we can’t see them,” he told Peter Brannen, author of The Ends of the World, who asked that if the sixth major mass extinction of the Phanerozoic, the biological “perfect storm,” is coming, where will the refugia be? “There won’t be many,” Jablonski said glumly.
“The human footprint is truly pervasive, from McMurdo Station to the north coast of Greenland. From submarine habitats to the tops of mountains. You have metals deposited in remote lakes in the Andes, and of course, in the ocean, plastic is everywhere. So there won’t be any places to hide, really. The groups that are going to do the best are the ones that can actually coexist with people as opposed to the ones that can find the last few hidey-holes. But if society collapses, dogs will just go back to being wolves. The genus canis will be just fine in the long run.
“But things like ocean acidification are really going to matter,” Jablonski continued. “That’s the key, right? Because of course there’s been plenty of warming in the past. But how do clades deal with warming? They move around. But if you’ve built hotels, and sewage effluents, and you’re dynamiting reefs, you can’t move around anymore. And of course, if on top of that you then acidify the ocean, you’ve again removed potential refugia. And so that’s the real problem: we’re the perfect storm.”
“The Perfect Storm”
“We’re not just warming, we’re not just pollution, we’re not just overexploitation, we’re piling it all on simultaneously. That’s why it’s really inaccurate to argue that because there’s been warming in the past that doesn’t count now, because it’s part of the perfect storm. I think that all mass extinctions work that way. I think it’s going to turn out that that’s how all the Big Five work—that lots of things go wrong. Say the K-T wouldn’t have been as bad if you hadn’t had the Deccan Traps erupting, or the Deccan Traps wouldn’t have done that much damage if you hadn’t dropped a rock out of the sky. But you combine those. The Permian-Triassic is the same way. The Devonian is the same way. The End-Ordovician is the same way. The Triassic-Jurassic—it’s these combinatory things. You’ve got to get away from single-factor explanations. I suspect a lot of the major events in the history of life involve perfect storms. And we’re one of them.”
In a new landmark study, Hana Jurikova a research fellow at the University of St Andrews (her research primarily focuses on the co-evolution of climate, environment and life on Earth during the Phanerozoic Eon), mirrors Jablonski’s concern. The Phanerozoic is the current eon in the geologic time scale of multicellular life, covering 541 million years to the present.
A Cascading Catastrophe
“We are dealing with a cascading catastrophe in which the rise of CO2 in the atmosphere set off a chain of events that successively extinguished almost all life in the seas,” Jurikova observes, “Ancient volcanic eruptions of this kind are not directly comparable to anthropogenic carbon emissions, and in fact all modern fossil fuel reserves are far too insufficient to release as much CO2 over hundreds of years, let alone thousands of years as was released 252 million years ago. But it is astonishing that humanity’s CO2 emission rate is currently fourteen times higher than the annual emission rate at the time that marked the greatest biological catastrophe in Earth’s history”.
Earth’s history, Jurikova reports, knows catastrophes which are unimaginable for humans. For example, around 66 million years ago an asteroid impact marked the end of the dinosaur era. Long before however, 252 million years ago at the boundary between the Permian and Triassic epochs, Earth witnessed a far more extreme mass extinction event that extinguished about three-quarters of all species on land and some 95 percent of all species in the ocean. Volcanic activity on an enormous scale in today’s Siberia has long been debated as a likely trigger of the Permian-Triassic mass extinction, but the exact sequence of events that led to the extinction remained highly controversial.
Now, a team of researchers led by Jurikova from GEOMAR Helmholtz Centre for Ocean Research Kiel, in collaboration with the Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences and Italian and Canadian universities, provides for the first time a conclusive reconstruction of the key events that led to the mega-catastrophe. Their research also draws bleak lessons for the future.
The international team studied isotopes of the element boron in the calcareous shells of fossil brachiopods – clam-like organisms – and with it determined the rate of ocean acidification over the Permian-Triassic boundary. Because the ocean pH and atmospheric carbon dioxide (CO2) are closely coupled, the team was able to reconstruct changes in atmospheric CO2 at the onset of the extinction from boron and carbon isotopes. They then used an innovative geochemical model to study the impact of the CO2 injection on the environment.
“Siberian Traps” led to Vast De-oxygenation of the Ocean
Their findings showed that volcanic eruptions, from the then active flood basalt province “Siberian Traps”, released immense amounts of CO2 into the atmosphere. This large CO2 release lasted several millennia and led to a strong greenhouse effect on the late Permian world, causing extreme warming and acidification of the ocean. Dramatic changes in chemical weathering on land altered productivity and nutrient cycling in the ocean, and ultimately led to vast de-oxygenation of the ocean. The resulting multiple environmental stressors combined to wipe out a wide variety of animal and plant groups.
Long Vanished Oceans Preserved in Fossil Shells
A large part of the work was done by the researcher at GEOMAR Helmholtz Centre for Ocean Research in Kiel, but she later joined the GFZ in Potsdam, and the “icing on the cake” for her were the results from a collaboration with the SIMS laboratory led by Michael Wiedenbeck at the GFZ. Using the state-of-the-art large-geometry secondary ion mass spectrometer (SIMS), the isotopic composition of the shells could be measured directly on the specimens at the micrometer-scale. This made it possible to determine the boron isotopic composition even in the smallest fragments of brachiopod shells. Depending on the degree of acidification of the seas, the calcareous shells of the organisms living in them differ ever so slightly in their chemical composition. In this way, the pH value of long vanished oceans could be determined in the remains of the shells preserved as fossils in the rock record.
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