Throughout history, the earth has gone through five mass extinctions. In the ocean, we are close to another one if climate change continues unabated, according to a new study, published in the journal Science by Princeton researchers Justin Penn and Curtis Deutsch.
The researchers predict that marine life could suffer a mass die-off in such a scale that hasn’t been seen in hundreds of millions of years, while arguing that the outcome is indeed in human hands.
Around a quarter of a billion years ago, the oceans faced a mass die-off due to rising temperatures, an event that has often been deemed the worst mass extinction event ever. On land, greenhouse gases were released by erupting volcanoes in Siberia, warming the planet and causing acid rain to fall. In the ocean, temperatures rose by around 10 degrees Celsius around the tropics, while deep-sea currents slowed down and starved the oceans of oxygen. During this period, that is often called the ‘Great Dying’, less than 5% of marine species survived.
“These environmental changes are also happening in the modern ocean today,” argues Penn, showing what humanity could face in the near future if climate change doesn’t get mitigated. The study argues that in an extreme future climate scenario which would see a five degrees Celsius warming by the end of the century, a similar mass extinction could be triggered within the next 300 years.
In this scenario, rising ocean temperatures would lead to less dissolved oxygen in the water, making many marine animals attempt to migrate toward the poles, while species in warmer areas would die off.
During the study, the researchers used a special model that analysed the behaviour of marine species in response to environmental change. While taking a closer look at one mild and one severe hypothetical future warming scenario, they found that extinction risks rise with the ocean’s temperatures.
On a brighter note, they also found that the risk of extinction could be significantly reduced by over 70% if humans act swiftly and global warming would be kept in check. Keeping warming below 2 degrees Celsius, while curbing pollution and putting a focus on implementing sustainable fishing practices, would avoid another ocean mass extinction.
In essence, the study shows that it is in human hands to decide where the future will fall between the study’s best- and worst-case scenarios.
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Photography courtesy of Ocean Image Bank / Matt Curnock & Gabriel Barathieu.