Global warming risks the most cataclysmic extinction of marine life in 250 million years | Climate crisis

Global warming is causing the world’s oceans to change so drastically that it risks leading to a mass extinction of marine species that rivals anything that has happened in Earth’s history over tens of millions of years, new research has warned.

Accelerating climate change is having a “profound” impact on ocean ecosystems that “increases extinction risk and reduces marine biological richness compared to what has been observed in Earth’s history over the past decades millions of years,” according to the study.

Global seawater temperatures are steadily rising due to extra heat produced by burning fossil fuels, while oxygen levels in the ocean are plunging and water is becoming acidic from the absorption of carbon dioxide from the atmosphere.

This means the oceans are overheated, gasping for air – the volume of completely oxygen-depleted ocean waters has quadrupled since the 1960s – and becoming more hostile to life. Aquatic creatures such as clams, mussels, and shrimp are unable to properly form shells due to acidification of seawater.

All of this means the planet could slide into a “mass extinction rivaling those of Earth’s past”, says the new research, published in Science. The pressures of increasing heat and oxygen loss are, researchers say, uncomfortably reminiscent of the mass extinction event that occurred at the end of the Permian period about 250 million years ago. years. This cataclysm, known as the “Great Death”, led to the disappearance of up to 96% of the planet’s marine animals.

“Even if the magnitude of species loss is not at the same level as this, the mechanism of species loss would be the same,” said Justin Penn, a climatologist at Princeton University, co- author of the new research.

“The future of life in the oceans is highly dependent on what we decide to do with greenhouse gases today. There are two very different oceans we could see, one devoid of much life that we see today, based on what we see with CO2 emissions in the future.

Truly catastrophic levels of extinction could be reached if the world were to emit rampant planetary-warming gases, resulting in an average warming of more than 4°C above pre-industrial times by the end of this century, according to research. This would trigger extinctions that would reshape ocean life for centuries as temperatures continue to climb.

But even in the best-case scenarios, the world is still expected to lose a significant portion of its marine life. At 2°C warming above the pre-industrial norm, which is projected as likely even under current climate commitments from world governments, about 4% of the roughly two million species in the oceans will be wiped out.

Fish and marine mammals that live in polar regions are the most vulnerable, according to the study, because they will not be able to migrate to cooler climates, unlike tropical species. “They won’t have anywhere to go,” Penn said.

The threat of climate change amplifies other major dangers facing aquatic life, such as overfishing and pollution. Between 10% and 15% of marine species are already at risk of extinction due to these various threats, according to the study, 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 seemed “sound”, but differed from previous studies on the subject which suggest that species will mostly disperse into new areas rather than being completely. muffled.

“It’s very different from what most previous work has developed. But that doesn’t mean they’re wrong,” Bruno said. “I think this new work challenges some of our current assumptions about geographic patterns of impending extinction in the ocean.”

Bruno said that while mass extinctions are likely due to extreme warming in the future, the current impacts of climate change and other threats should be of sufficient concern to policymakers and the public.

“Personally, I’m much more worried about the ecosystem degradation that we’re already seeing after less than 1°C of warming,” he said.

“We don’t need to look to a world so warmed that humanity has been wiped out – we are already losing untold biodiversity and functioning ecosystems, even with the relatively modest warming of the past 50 years.”

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