Scientists say humans who are alive today might have the all-too-real experience of witnessing the beginning of a mass extinction.
In a paper published Wednesday in the journal Science Advances, geophysicist Daniel Rothman illustrates how current rates of carbon emission increases could trigger a sixth mass extinction by the year 2100.
Prehistoric events like mass extinctions occur on such massive timescales that they can often be difficult to comprehend, but this could change soon. Since the Cambrian explosion that brought the beginning of early life forms 540 million years ago, there have been five mass extinctions, the most recent of which is the Cretaceous-Tertiary extinction that killed most of the dinosaurs 65.5 million years ago. Each of these extinctions killed more than 75 percent of marine animal species on Earth, and it could happen again.
Rothman, professor of geophysics in the Department of Earth, Atmospheric, and Planetary Sciences at Massachusetts Institute of Technology, explains that previous mass extinctions showed patterns in carbon cycle disruptions that are similar to those that scientists are seeing today.
“The carbon cycle today is essentially the same as in the past,” Rothman tells Inverse. “However the current disturbance of the carbon cycle is likely much faster than in the past, occurring at a time scale of centuries rather than tens of thousands to millions of years.” Centuries may sound like a long time, but it’s a blink of an eye in geological time.
In the new paper, Rothman calculates that in 2100, current trends in carbon emissions suggests that atmospheric and oceanic carbon will surpass a hypothetical threshold point. Past this threshold, life on Earth is not well-adapted to deal with the changes that would occur as a result of the massively accelerated input of carbon. And what’s more, this cycle may accelerate itself.
“After roughly 300 gigatons of carbon are added to the oceans, the marine carbon cycle may evolve in a way that amplifies that disturbance,” says Rothman. “That threshold would likely be passed sometime in the present century. The ensuing amplification (in technical terms, unstable evolution) would evolve slowly and reach its peak on the order of 10,000 years later.”
Rothman recognizes that, as evidenced by complicated combinations of factors contributing to past extinction events — volcanism, for example — it’s not totally clear how significant the role of the carbon cycle will be in the sixth mass extinction.
“Multiple causes may also be responsible for a ‘sixth extinction,’” he writes in the paper. “However, the anthropogenic disturbance of the carbon cycle merits its own appraisal.”
The beginning of the sixth mass extinction could begin during our lifetimes, but we likely wouldn’t see the end results. That doesn’t mean it’s inevitable, though.
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