Humanity has a huge impact on our planet but predicting the long-term effects of our actions is not exactly simple. An important question scientists have been asking is could our activities trigger a mass extinction?
According to Professor Daniel Rothman, a geophysicist at MIT, if 310 gigatons of carbon were added to the oceans this would first lead to an unstable environment, and then to a mass extinction. This amount is predicted to enter the world’s water reservoir by 2100. The research is published in Science Advances.
“This is not saying that disaster occurs the next day,” Rothman clarified in a statement. “It’s saying that, if left unchecked, the carbon cycle would move into a realm which would be no longer stable, and would behave in a way that would be difficult to predict. In the geologic past, this type of behavior is associated with mass extinction.”
The theory looked at changes in carbon over long and short timescales. Over long timescales, extinction could happen if carbon cycle changes occur faster than the planet can adapt to them. Over short timescales, however, extinction will depend on how big the change is. Rothman was capable of putting a “carbon threshold” on how much carbon the oceans can take in. According to the theory, it might take up to 10,000 years for the full disaster to play out, but Rothman thinks that by 2100 we will be reaching, or moving past, the carbon threshold for catastrophe.
There have been five mass extinctions throughout the history of our planet, and Rothman wanted to know if a sixth was likely based on the data we have today and what we have been doing since the industrial revolution.
“How can you really compare these great events in the geologic past, which occur over such vast timescales, to what’s going on today, which is centuries at the longest? So I sat down one summer day and tried to think about how one might go about this systematically,” Rothman added. “It became evident that there was a characteristic rate of change that the system basically didn’t like to go past. Then it became a question of figuring out what it meant.”
Once the limit is breached, the carbon cycle breaks. Plants can’t take the extra carbon dioxide in and carbon no longer sinks to the bottom of the ocean, where it normally gets buried over time. The best case scenario for 2100 sees humans adding 300 gigatons of carbon to the ocean with more than 500 gigatons being added in the worst.