This story was first published by Guardian and is reproduced here as part of the Climate Desk collaboration.
Global heating is causing such a drastic change to the world’s oceans that it risks a mass extinction event of marine species that rivals anything that’s happened in the Earth’s history over tens of millions of years, new research has warned.
Accelerating climate change is causing a “profound” impact upon ocean ecosystems that is “driving extinction risk higher and marine biological richness lower than has been seen in Earth’s history for the past tens of millions of years,” according to the study.
The world’s seawater is Temperatures continue to rise due to the extra heat produced from the burning of fossil fuels, while oxygen levels in the ocean are plunging and the water is acidifying from the soaking up of carbon dioxide from the atmosphere.
This means that the oceans have become increasingly overheated. Gasping for breath—the volume of ocean waters completely depleted of oxygen has Since the 1960s, it has quadrupled—and becoming more hostile to life. The acidification of seawater results in aquatic animals such as shrimp, mussels, and crabs not being able to form shells.
All of this means the planet could slip into a “mass extinction rivaling those in Earth’s past,” states the new research, Published in Science. Researchers said that the pressures of rising heat, loss of oxygen, and rising heat are uncomfortably similar to the mass extinction event at the Permian end of the Permian period approximately 250m years ago. This cataclysm, known as the “great dying,” led to the demise of up to 96 percent of the planet’s marine animals.
“Even if the magnitude of species loss is not the same level as this, the mechanism of the species loss would be the same,” said Justin Penn, a climate scientist at Princeton University who co-authored the new research. “The future of life in the oceans rests strongly on what we decide to do with greenhouse gases today. There are two vastly different oceans we could be seeing, one devoid of a lot of life we see today, depending on what we see with CO2 emissions moving forward.”
The research revealed that if the world continues to emit planet-heating gases in an unrestrained manner, it could lead to more than 4C of global warming above preindustrial times by the end this century. This would lead to extinctions that could reshape the ocean for several more centuries, as temperatures continue to rise.
Even in the best of cases, the world could still lose a significant amount of its marine life. 2C of heating above pre-industrial norm is acceptable. Forecast as likely even under current climate pledges by the world’s governments, around 4 percent of the roughly two million species in the oceans will be wiped out.
The study found that marine mammals and fish living in polar regions are the most vulnerable. They won’t be able migrate to cooler climes like tropical species. “They will just have nowhere to go,” said Penn.
The threat of climate changes is increasing the other major threats facing aquatic life, including over-fishing as well as pollution. Based on data from the International Union for Conservation of Nature, the study found that between 10 and 15 percent of marine species are at risk of extinction due to these diverse threats.
John Bruno, a marine ecologist at the University of North Carolina who was not involved in the study, said the new research appeared “sound” but it differed from previous studies on the topic that suggest species will mainly disperse to new areas rather than be completely snuffed out.
“It’s very different from what most prior work has developed. But that doesn’t mean they are wrong,” Bruno said. “I think this new work is challenging some of our current assumptions about the geographic patterns of looming extinction in the ocean.”
Bruno stated that, while mass extinctions may be possible from extreme heating in future, the current effects of climate change should be alarming enough for policymakers to address.
“Personally, I’m a lot more worried about the ecosystem degradation we’re already seeing after less than 1C of warming,” he said. “We don’t need to look to a world so warmed over humanity has been wiped out—we’re already losing untold biodiversity and ecosystem functioning with even the relatively modest warming of the last 50 years.”