A new study has found that nearly 90% of assessed marine life will be at high or critical risk by the year 2100 if climate change accelerates along a high-emissions pathway, and that these species will face risks across 85% of their native ranges in the ocean.
“It’s a pretty bleak picture,” Alex Pigot, study co-author and biodiversity expert at University College London, told Mongabay. “When we’re talking about 90% of species at higher critical risk across most of their geographic distribution, we’re talking about enormous disruption to marine ecosystems.
“The projections for the kind of ocean that we would be leaving our children and grandchildren by the end of the century,” he added, “is really extremely concerning.”
While Pigot says that ultimately “nowhere on the planet will be unaffected by climate change,” the risks will be more concentrated in the tropics, while marine species at higher latitudes will face slightly fewer risks.
“I think those disparities in the impacts on potential risks of climate change to different countries are really stark,” he said. “As a general rule, we’re finding that countries that are at lower latitudes, countries that rely on marine resources more heavily for their economy and nutrition, and countries that are essentially least equipped to be able to deal with these impacts are the ones that are facing the highest risk. And of course, they’re also the ones that have contributed the least to historical greenhouse gas emissions, and are actually often doing the most now to mitigate their emissions.”
The paper also found that top predators like sharks would be more vulnerable than species lower down the food chain.
Published this week in Nature Climate Change, the study analyzed the climate change risk for nearly 25,000 species living in the upper 100 meters (330 feet) of the water column under two scenarios: a high-emissions track, as well as a pathway toward mitigation more aligned with the goals of the Paris Agreement. While carrying on with business as usual doesn’t bode well for the oceans, the study found that a reduction in emissions would reduce risk for “virtually all species” — more than 98%.
“The beneficial impact of following a high mitigation scenario — of transitioning society towards a more sustainable pathway — is huge,” Derek Tittensor, study co-author and marine ecologist at Dalhousie University in Canada, told Mongabay in an email. “The overwhelming positives of seriously tackling climate change are enormous both for people and for life in the oceans.”
Tittensor added that we need to reduce our emissions, mitigate our impacts and transition to renewable energies as quickly as possible to be able to forge a more sustainable future for our oceans.
“We already know the solution; we just need to put it into practice,” he said.
Another study published earlier this year in Nature found that global temperatures could be limited to 2° Celsius (3.6° Fahrenheit) above pre-industrial levels — slightly above the 1.5°C (2.7°F) target of the Paris Agreement — but only if countries are able to meet all of their climate pledges on time. To make this a reality, the authors of this study say that countries need to “urgently” administer policies and actions “to bring about steep emission reductions this decade, aligned with mid-century global net-zero CO2 emissions.”
Study co-author Katie Schleit, a senior fisheries adviser at Oceans North, a marine conservation group that helped fund the research published in Nature Climate Change, said the new study provides a climate vulnerability index that can be used by fisheries managers “to better adapt and make management plans that account for climate change.”
“Previously, we might have had information on broad-scale trends in terms of climate and their impact, but not necessarily at species-specific or management-specific resolutions,” Schleit told Mongabay. “This kind of an index can be used in those contexts, so we’re very excited about that.”
She added that a high-seas treaty currently being negotiated in New York — which aims to protect about 30% of international waters beyond any individual country’s jurisdiction by 2030 — could deliver much-needed protection to species most vulnerable to climate risks.
“There is currently no way to create protected areas and fully protect species across their high-seas ranges,” she said. “This is why the high-seas treaty for biodiversity beyond national jurisdiction is so important.”
Schleit added that the study also clearly shows the urgent need — and vast benefits — of immediately reducing emissions.
According to Pigot, the paper illustrates “two different worlds in which you could be living in by the end of the century,” one of which is “much nicer than the other.”
“I wouldn’t want to see it as a depressing paper because we’re not at that point yet where we don’t have a choice,” he said. “We can still completely choose each of those different worlds. Of course, the very optimistic one that we look at requires things like not only immediate, massive reductions in emissions, but also technologies that will draw down and lock in carbon to actually have negative emissions in the future.”
Banner image: A manta ray with diver, Socorro. Image by Hannes Klostermann / Ocean Image Bank.
Boyce, D. G., Tittensor, D. P., Garilao, C., Henson, S., Kaschner, K., Kesner-Reyes, K., … Worm, B. (2022). A climate risk index for marine life. Nature Climate Change. doi:10.1038/s41558-022-01437-y
Meinshausen, M., Lewis, J., McGlade, C., Gütschow, J., Nicholls, Z., Burdon, R., … Hackmann, B. (2022). Realization of Paris Agreement pledges may limit warming just below 2°C. Nature. doi:10.1038/s41586-022-04553-z
This article by Elizabeth Claire Alberts was first published by Mongabay.com on 25 August 2022. Lead Image: A manta ray with diver, Socorro. Image by Hannes Klostermann / Ocean Image Bank.
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