"Staggering" Loss Of N. Hemisphere Marine BIomass: 7.2% Of Fish Populations Per 0.1C Warming Per Decade
Chronic ocean heating is fuelling a “staggering and deeply concerning” loss of marine life, a study has found, with fish levels falling by 7.2% from as little as 0.1C of warming per decade. Researchers examined the year-to-year change of 33,000 populations in the northern hemisphere between 1993 and 2021, and isolated the effect of the decadal rate of seabed warming from short shifts such as marine heatwaves. They found the drop in biomass from chronic heating to be as high as 19.8% in a single year.
“To put it simply, the faster the ocean floor warms, the faster we lose fish,” said Shahar Chaikin, a marine ecologist at the National Museum of Natural Sciences in Spain and the study’s lead author. “A 7.2% decline for every tenth of a degree per decade might sound small,” he added. “But compounded over time, across entire ocean basins, it represents a staggering and deeply concerning loss of marine life.”
The study, published in Nature Ecology & Evolution on Wednesday, also found marine heatwaves were leading to short-term booms in some populations that masked long-term harm from climate breakdown. For instance, a heatwave that could cause sprat populations to fall in the Mediterranean Sea, which is at the warm edge of their natural range, would lead to a boom in the North Sea, at the cold edge of their range.
Fish in cold areas are better able to capitalise on these shifts than those in warm areas, the researchers found, but these temporary cold-water gains mask “widespread loss” due to ocean warming.
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https://www.theguardian.com/environment/2026/feb/25/chronic-ocean-heating-fuels-staggering-loss-marine-life-study