Daniel Rothman talks about a sixth mass extinction that is possible on the basis of how things currently are.
He talks about how the carbon in the Earth’s atmosphere can push the seas past a threshold, which in turn can trigger a cascading catastrophe for ecosystems. These changes are not fully understood, yet.
The lithosphere bears the scars of climatic changes. Hurricanes are rampant, fires have ravaged forests, floods have drowned cities, and entire species are seen to simply disappear. If you can look beneath the surface, there lie things that are unfathomable and more severe than what we have observed.
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Daniel Rothman is a professor of geophysics at MIT and believes that humans might be creeping towards a calamity that can affect the entire world. A Sixth Mass Extinction event!!
Is The Sixth Mass Extinction Inevitable?
The massive amount of carbon that human beings are pumping into the atmosphere may soon cross the tipping point, which will then disrupt the Earth’s carbon cycle. It causes a cascade of such disruptions which we cannot fathom, as stated by Rothman.
We know for sure that such disruptions were always followed by mass extinctions in the 500 million years since the abundance of life on Earth. While the climate issues are framed in terms of years, decades, or centuries, mass extinctions play out over thousands of human years.
“Every time there has been a major event in the history of life, there has also been a major perturbation of the environment. These things tend to come together,” he said.
Disruptions like these are linked with the carbon cycle. We know that for sure by looking at the traces that are left in the carbon chemistry of ancient rocks.
Read: Entire Ecosystems Can Collapse Within A Decade If Global Warming Goes Unchecked
Rothman added that “The average person doesn’t really think about such long time scales, of course, they don’t, but that’s also geology’s gift to the world.”
Testing The Waters
Rothman stated that several disruptions in the carbon cycle were not followed by mass extinctions.
The carbon cycle is a complex system that centers on photosynthesis and respiration. In the cycle, carbon is exchanged between the atmosphere and the upper levels of the Earth’s ocean. Too much carbon can affect the ocean’s damping mechanism. It can lead to a series of events that can then disrupt the entire system.
Too much carbon can render the oceans acidic and uninhabitable for several forms of life.
Four of the five last mass extinctions were associated with an increased rate of carbon cycle change and it seems as if there is a unique rate of change that keeps acting as a threshold.
We can understand this phenomenon with the help of an analogy.
If water flows out of the bathtub faucet faster than it goes down the drain, eventually the room will flood.
Now imagine you open a firehose in the bathtub for a few seconds. Almost no water goes down the drain, and it may cause a flood so what matters is the amount of water you pour in during that short interval.
Rothman calculated that the critical threshold for carbon in the ocean is around 300 gigatons in a century, and we are on track to add up to 500 gigatons by 2100. He had published peer-reviewed papers on the same subject in 2017 and 2019.
The Threshold Or Tipping Point
Our past is quite murky and its details are incomplete. All we know is that mass extinctions occur on a continuum, where species die out even when the systems are viable.
Rothman spoke about the times of environmental stress, where we have a record of the carbon cycle’s behavior and find a clear link between the extinction and the change in the carbon cycle.
“You can blame mortgages but it’s a whole set of things. Once there’s a modest instigation, the whole thing goes crazy and it basically becomes unstable and you have this recession, so it’s catastrophic change,” he said. “To point your finger at any one thing, you might have been able to identify some kind of proximate cause, but identifying what the real cause is, the way things interact with each other is a different game.”
“There are what we call tipping points or positive feedbacks in the system, and we don’t really understand them,” he said. “This is really at the vanguard of scientific research in this area.”
Mass extinctions leave behind a terrestrial record as well as a marine record. The marine records are quite easy to interpret.
There is a great debate over whether we have already entered a mass extinction event, caused by us(the Holocene extinction). The rate of die-offs is already far higher than the natural extinction rate.
Rothman has also co-founded MIT’s Lorenz Center, which tries to predict and understand complex scientific challenges that we have faced as a species.
“We need to limit the ways we pollute the environment and we need to find ways of diminishing the amount of CO₂ we put in the atmosphere. Of course, we already knew that but this provides another kind of reason to do it,” he said. “There are things that could happen which essentially go beyond our ability to understand them.”
