Global warming is causing such a drastic change in the world’s oceans that it risks a mass extinction event of marine species that rivals anything that has happened in Earth’s history in tens of millions of years, new research has warned.
According to the study, accelerating climate change is causing a “profound” impact on ocean ecosystems that “increasing the risk of extinction and reducing marine biological wealth than has been seen in Earth’s history over the past tens of millions of years” .
The seawater of the world is steadily rising in temperature due to the extra heat produced by burning fossil fuels, while the oxygen levels in the ocean are plummeting and the water is acidifying due to the absorption of carbon dioxide by the ‘atmosphere.
This means that the oceans are overheated, increasingly panting – the volume of completely oxygen-depleted ocean waters has quadrupled since the 1960s – and are becoming more hostile to life. Aquatic creatures such as clams, mussels and shrimps are unable to form shells properly due to acidification of the seawater.
All of this means that the planet could slide into a “mass extinction that rivals those of Earth’s past,” says the new research, published in Science. The pressures of increased heat and oxygen loss, the researchers said, are unpleasantly reminiscent of the mass extinction event that occurred at the end of the Permian period some 250 million years ago. This cataclysm, known as the “great dying man”, has resulted in the deaths of up to 96% of the planet’s marine animals.
“Even if the extent of species loss is not at the same level, the mechanism of species loss would be the same,” said Justin Penn, a climate scientist at Princeton University who is a co-author of the new research.
“The future of life in the oceans depends heavily on what we decide to do today with greenhouse gases. There are two very different oceans that we could see, one devoid of much life we see today, depending on what we see with the CO2 emissions going on. “
According to the research, truly catastrophic extinction levels could be reached if the world emitted gases that warm the planet in a rampant way, leading to an average warming of more than 4 ° C compared to pre-industrial times by the end of this century. This will trigger extinctions that would reshape ocean life for many more centuries as temperatures continue to soar.
But even in the best of scenarios, the world is still doomed to lose a significant chunk of its marine life. With 2 ° C of warming above the pre-industrial norm, which is also expected to be likely under current climate commitments by world governments, about 4% of the roughly two million species in the oceans will be wiped out.
Fish and marine mammals living in the polar regions are the most vulnerable, according to the study, as they will not be able to migrate to suitably cooler climates, unlike tropical species. “They will have nowhere to go,” Penn said.
The threat of climate change is amplifying the other major dangers facing aquatic life, such as overfishing and pollution. Between 10% and 15% of marine species are already at risk of extinction from these various threats, the study found, drawing on data from the International Union for Conservation of Nature.
John Bruno, a marine ecologist at the University of North Carolina who was not involved in the study, said the new research looked “healthy” but differed from previous studies on the subject that suggest the species will mainly disperse into new areas. rather than being completely shut down.
“It is very different from what most of the previous works developed. But that doesn’t mean they’re wrong, ”said Bruno. “I think this new work is challenging some of our current hypotheses about geographic patterns of impending extinction in the ocean.”
Bruno said that while mass extinctions are likely in the future due to extreme warming, the current impacts of climate change and other threats should be worrying enough for policy makers and the public.
“Personally, I am much more concerned about the ecosystem degradation that we are already seeing after less than 1 ° C of warming,” he said.
“We don’t need to look at a world so warmed by humanity that it has been wiped out: we are already losing unspeakable biodiversity and ecosystem functioning even with the relatively modest warming of the past 50 years.”