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Dead FishA recent report predicts shrinking global fisheries as a result of rising ocean acidification and the spread of undersea “dead zones.” 

Published jointly by the Sustainable Fisheries Partnership, the University of Cambridge’s Institute for Sustainability, and Cambridge’s Judge Business School, the report draws its conclusions from the United Nations’ climate change assessment, released earlier this year.

Ocean acidification occurs when too much carbon dioxide is absorbed by sea water. The excess CO₂ causes the water’s natural pH level to drop and reduces the concentration of calcium carbonate, an essential mineral for the formation of seashells and coral. Absorbing CO₂ is a natural part of the ocean’s ecosystem, but the rise in carbon emissions has accelerated this process, leading to the formation of weaker shells and coral reefs.

Coral reefs provide homes and food to many undersea creatures and their degradation promises catastrophe for the food chain. As the report states, “projected rise in acidity by 2100 would be at least twice today’s levels” and “is projected to drive a decline in global shellfish production between 2020 and 2060.”

Another danger to fish populations comes not from the air but from the land. Polluted runoff containing nitrates and phosphorous is being absorbed by the ocean and promoting the growth of algae that fail to provide enough oxygen to fish. Areas with the most runoff have become undersea “dead zones,” the most prominent of which is in the Gulf of Mexico and, as of last year, was the size of Connecticut.

These twin dangers, the report predicts, along with rising global temperature, may lead to mass migrations of fish and a massive blow to the seafood industry.

“This…is a wake up call for the seafood industry to recognize the scale of the threat to ocean resources from climate change and acidification,” says Blake Lee-Harwood of Sustainable Fisheries Partnership. “We need to see urgent action in trying to mitigate the likely impacts while adapting wherever that’s practically possible.”

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