Scientists Discover How a Giant Release of Carbon Dioxide Triggered a Mass Extinction of Ancient Marine Organisms

It’s a parallel comparison to what’s happening to this world, what with the record levels of carbon dioxide being amassed today and all. I’ve understood for years that climate change was a significant threat, but as more is discovered, it’s turning out to be a far more significant problem than I ever imagined.

Global climate change, fueled by skyrocketing levels of atmospheric carbon dioxide, is siphoning oxygen from today’s oceans at an alarming pace — so fast that scientists aren’t entirely sure how the planet will respond.

Their only hint? Look to the past.

In a study to be published this week in the journal Proceedings of the National Academy of Sciences, researchers from Florida State University did just that — and what they found brings into stark relief the disastrous effects a deoxygenated ocean could have on marine life.

Millions of years ago, scientists discovered, powerful volcanoes pumped Earth’s atmosphere full of carbon dioxide, draining the oceans of oxygen and driving a mass extinction of marine organisms.

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“We wanted to reconstruct Early Jurassic ocean oxygen levels to better understand the mass extinction and the T-OAE,” said Theodore Them, a postdoctoral researcher at FSU who led the study. “We used to think of ocean temperature and acidification as a one-two punch, but more recently we’ve learned this third variable, oxygen change, is equally important.”

By analyzing the thallium isotope composition of ancient rocks from North America and Europe, the team found that ocean oxygen began to deplete well before the defined time interval traditionally ascribed to the T-OAE.

That initial deoxygenation, researchers say, was precipitated by massive episodes of volcanic activity — a process not altogether unlike the industrial emission of carbon dioxide we’re familiar with today.

“Over the past 50 years, we’ve seen that a significant amount of oxygen has been lost from our modern oceans,” Them said. “While the timescales are different, past volcanism and carbon dioxide increases could very well be an analog for present events.”

When the atmosphere is suffused with carbon dioxide, global temperatures climb, triggering a cascade of hydrological, biological and chemical events that conspire to sap the oceans of oxygen.

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“It’s extremely important to study these past events,” Them said. “It seems that no matter what event we observe in Earth’s history, when we see carbon dioxide concentrations increasing rapidly, the result tends to be very similar: a major or mass extinction event. This is another situation where we can unequivocally link widespread oceanic deoxygenation to a mass extinction.”

Steps can still be taken to curb oxygen loss in the modern oceans. For example, conserving important wetlands and estuaries — along with other environments that absorb and store large amounts of carbon dioxide — could help to blunt the effects of harmful industrial emissions.

Biodiversity Losses Increase Risks of Domino Effect of Further Extinctions

This phenomenon is referred to as an “extinction cascade.”

New research shows that the loss of biodiversity can increase the risk of “extinction cascades,” where an initial species loss leads to a domino effect of further extinctions.

The researchers, from the University of Exeter, showed there is a higher risk of extinction cascades when other species are not present to fill the “gap” created by the loss of a species.

Even if the loss of one species does not directly cause knock-on extinctions, the study shows that this leads to simpler ecological communities that are at greater risk of “run-away extinction cascades” with the potential loss of many species.

With extinction rates at their highest levels ever and numerous species under threat due to human activity, the findings are a further warning about the consequences of eroding biodiversity.

“Interactions between species are important for ecosystem (a community of interacting species) stability,” said Dr Dirk Sanders, of the Centre for Ecology and Conservation at the University of Exeter’s Penryn Campus in Cornwall. “And because species are interconnected through multiple interactions, an impact on one species can affect others as well.

“It has been predicted that more complex food webs will be less vulnerable to extinction cascades because there is a greater chance that other species can step in and buffer against the effects of species loss.

“In our experiment, we used communities of plants and insects to test this prediction.”

The researchers removed one species of wasp and found that it led to secondary extinctions of other, indirectly linked, species at the same level of the food web.

This effect was much stronger in simple communities than for the same species within a more complex food web.

Dr Sanders added: “Our results demonstrate that biodiversity loss can increase the vulnerability of ecosystems to secondary extinctions which, when they occur, can then lead to further simplification causing run-away extinction cascades.”

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The loss of a predator can initiate a cascade, such as in the case of wolves, where their extinction on one mountain can cause a large rise in the number of deer. This larger number of deer then eats more plant material than they would have before. This reduction in vegetation can cause extinctions in any species that also relies on the plants, but are potentially less competitive, such as rabbits or insects.

Add this research to one of the many reasons why rigorously addressing climate change — which can destabilize environments — is of paramount importance.