New Delhi:
Our planet Earth may face a sixth mass extinction by about 2100 due to the rising carbon levels in the oceans, according to the prediction by scientists at Massachusetts Institute of Technology (MIT).
An analysis of data from the last 540 million years led to researchers at MIT predicts the sixth mass extinction. Significant changes in the carbon cycle over the last 540 million years, including the five mass extinction events, were noticed by the scientists.
“Thresholds of catastrophe” in the carbon cycle was identified and if it is exceeded, it would lead to an unstable environment, and ultimately, mass extinction.
Cretaceous-Tertiary extinction, the fifth mass extinction, took place about 66-million-years-ago, wiping out some three-quarters of Earth and the animal species on the planet.
According to researchers, mass extinction takes place when one of the two thresholds are crossed. They said that first the changes in the carbon cycle that take place over long timescales – extinction will occur if those changes happen at rates faster than global ecosystems can adapt.
Second, carbon perturbations that occur over shorter timescales – the pace of carbon-cycle changes won’t matter, instead the size or magnitude of the change will determine the likelihood of an extinction event, they said.
In the view of the recent increase in carbon dioxide emissions over a relatively short timescale, a sixth extinction will depend on whether a critical amount of carbon is added to the oceans, predict researchers.
A simple mathematical formula based on the physical principles that relate to critical rate and magnitude of change in the carbon cycle to the timescale that separates fast from slow change was derived by Professor Daniel Rothman from MIT.
He hypothesised that this formula should predict whether mass extinction or some other sort of global catastrophe, would occur.
At least 31 events in the last 542 million years in which a significant change occurred in Earth's carbon cycle were identified by Rotham.
For each event, including the five previous mass extinctions, Rothman noted the change in carbon, expressed in the geochemical record as a change in the relative abundance of two isotopes, carbon-12 and carbon-13. He also noted the duration of time over which the changes occurred.
He then devised a mathematical transformation to convert these quantities into the total mass of carbon that was added to the oceans during each event. Finally, he plotted both the mass and timescale of each event.
That amount, calculated, is about 310 gigatons, which the researchers estimate to be roughly equivalent to the amount of carbon that human activities will have added to the world's oceans by the year 2100.
(With inputs from PTI)
