Global warming could lead to largest extinction of marine life
New research warns of growing heat and oxygen depletion, which are reminiscent of the "great dying" that occurred around 250 million years ago.
According to a recent study, global warming is generating such extreme changes in the world's seas that it risks a mass extinction catastrophe of marine species that matches anything that has happened in the Earth's history over tens of millions of years.
Global warming is having a "profound” impact on ocean ecosystems that are “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."
The temperature of the world's saltwater is constantly rising owing to the extra heat created by the combustion of fossil fuels, while oxygen levels in the ocean are falling and the water is acidifying due to the soaking up of carbon dioxide from the atmosphere.
This means the seas are overheating, short on-air (the amount of oxygen-depleted ocean waters has tripled since the 1960s), and becoming more unfriendly to life. Because of the acidity of saltwater, aquatic animals such as clams, mussels, and shrimp are unable to properly produce shells.
The great dying
The new research, published in Science, details how the globe could sink into "a mass extinction rivaling those in Earth’s past." According to researchers, the rising heat pressures and loss of oxygen are similar to a cataclysmic event that happened 250 million years ago during the Permian period, otherwise known as "the great dying" which killed off nearly 96% of marine animals on earth.
Justin Penn, a climate scientist at Princeton University who was co-author of the study, says “Even if the magnitude of species loss is not the same level as this, the mechanism of the species loss would be the same."
“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," he added.
The study discovered that if the globe continues to release planet-warming gases unrestrainedly, it would result in more than 4 degrees Celsius of average warming over pre-industrial levels by the end of the century. As temperatures continue to rise, this would cause extinctions that will change ocean life for numerous millennia.
Even under the best-case scenario, the planet will lose a major portion of its aquatic biodiversity. At 2 degrees Celsius over pre-industrial levels of warming, which is expected even with existing global climate promises, around 4% of the world's two million marine species will be wiped off.
According to the study, fish and marine animals living in polar areas are the most susceptible since, unlike tropical species, they would be unable to move to sufficiently colder climates.
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“They will just have nowhere to go,” stated Penn.
Climate change is exacerbating the other significant threats to aquatic life, such as overfishing and pollution. According to the report, between 10% and 15% of marine species are already at risk of extinction due to these multiple threats, based on statistics from the International Union for Conservation of Nature.
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The new research appeared "sound," according to John Bruno, a marine biologist at the University of North Carolina who was not involved in the study, but it contrasted with past studies on the issue that show species will primarily spread to other places rather than being fully wiped out.
According to Bruno, “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."