Nearly all marine species face extinction if greenhouse emissions don’t drop: study

Maintaining the status quo for greenhouse gas emissions could risk the extinction of up to 90 percent of marine species, according to a study published Monday in the journal Nature Climate Change. 

Researchers, led by ecologist Daniel Boyce of the Bedford Institute of Oceanography in Nova Scotia, looked at some 25,000 species, including animals, plants, protozoans and bacteria. Under a high-emission scenario, they determined that nearly 90 percent of those species will be at high-to-critical risk across 85 percent of their distribution. This scenario involves an increase of 3 to 5 degrees Celsius in global ocean temperatures by the end of the century. 

About 10 percent of the ocean overall features ecosystems that are considered high-risk based on a combination of endemism, climate risk and the threat of local species’ extinction, according to the study.  

In addition to the threat this poses to biodiversity around the planet, the results of the study present a major threat to people in the global south, with the biggest danger to species native to low-income countries that rely heavily on fisheries in the tropics and subtropics, according to Boyce and his colleagues. 

Meanwhile, reduced emissions — those consistent with the Paris Climate Agreement’s goals of keeping warming below 2 degrees — would cut the risk for about 98.2 percent of the analyzed species, according to the study.

The analysis is based on a combination 12 climate risk factors. Boyce and his team grouped them under the broader categories of sensitivity, exposure and adaptivity. 

“Our findings show a reduced climate risk for virtually all species and ecosystems under the low emissions scenario,” Boyce wrote in a blog post for Carbon Brief. “Thus, sticking to the goals of the Paris Agreement would have substantial benefits for marine life, with the disproportionate climate risk for ecosystem structure, biodiversity hotspots, fisheries and low-income nations being greatly reduced or eliminated.”