Most marine species will face extinction without limiting fossil fuels

A new study paints a shocking picture of the fate of marine life if the human contribution to climate change is not curbed. If greenhouse gases continue to be emitted at high rates, by the end of the century – just 78 years away – almost all marine species could face extinction, researchers have found.

The study, published in Nature Climate Change on Monday, analyzed how about 25,000 species would be able to cope with a variety of emissions scenarios depicted by the United Nations Intergovernmental Panel on Climate Change.

In a guest post for Carbon Briefs, Study authors Daniel Boyce and Derek Tittensor wrote that “climate change is rewiring marine ecosystems at an alarming rate” and that their work essentially created a “climate report card” for marine life.

“Just as a report card scores students in subjects like math and science, we used a data-driven approach to score individual species on 12 specific climate risk factors in all parts of the ocean where they live,” they said.

Under the highest emissions scenario, called SSP5-8.5, current carbon dioxide emissions will double by 2050.

The proportion of nearly 25,000 marine species at high or critical climate risk under SSP5-8.5 by 2100. Red shading indicates the most affected areas. / Credit: Boyce et al./Nature Climate Change

On that path, the world could expect to be up to 5.7ªC (more than 42ºF) warmer by the end of the century compared to the pre-industrial era – fueling more agricultural issues, devastating natural disasters and forced migration, they said Scientists. According to the study, this scenario would put about 90% of marine life in the upper 100 meters of the ocean at high or critical risk of extinction.

The species most threatened are the largest predators, particularly those hunted by humans for food, such as tuna and sharks. Endemic species, those found in a single geographic area, are also much more vulnerable.

“The findings also suggest serious implications for people who rely more on the ocean,” Boyce and Tittensor said.

Low-income countries that depend on fisheries and those that rely heavily on fish such as cod, anchovy and lobster for food and income will bear the brunt, the researchers said.

But on the other hand, if the world made severe cuts and reached net zero carbon emissions by 2050 and limited global warming to 2ªC, “almost all species” the researchers looked at would have a drastically reduced risk of extinction. It would also help stabilize ecosystems and could be monumentally beneficial for food nations, the researchers said.

“Overall, our results show that the climate risk to marine life is highly dependent on the magnitude of future emissions,” the researchers concluded.

This map shows how the extinction risk for species is changing as the world reduces global emissions.  Purple shading indicates reduced risk.  / Credit: D. Boyce, et al/Nature Climate Change

This map shows how the extinction risk for species is changing as the world reduces global emissions. Purple shading indicates reduced risk. / Credit: D. Boyce, et al/Nature Climate Change

President Biden recently signed the Inflation Reduction Act, which, among other things, provides $369 billion in funding for energy and climate projects aimed at 40% reduction in carbon emissions in 2030.

And while this has been heralded by climate experts as an important step in curbing emissions, it also comes on the heels of a Supreme Court decision to limit the Environmental Protection Agency’s ability to regulation of power plant emissions. It also comes just months after the United Nations released a report that only governments around the world have continued to invest in fossil fuel infrastructure and deforestation.

Boyce and Tittensor said that means mitigation is necessary. If countries do not drastically increase their efforts to reduce emissions, the planet will be up to 6.3ºF warmer within 80 years – and the worst-case scenario, SSP5-8.5, is possible.

But nations also need to focus on adaptation because even if emissions stop today, the world will continue to warm based on what it has already endured, Boyce and Tittensor said.

“The reality is that climate change is already affecting the oceans, and even with effective climate mitigation, they will continue to change,” they wrote in the guest blog post. “Therefore, adaptation to a warming climate is crucial to building resilience for both ocean species and humans.”

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