Seafood diets, nutrients threatened by rising global heat

People in low-income countries that rely on fish and seafood in their diet face greater food security challenges in the future due to climate change, with seafood nutrient sources dropping by 30% (and even more in global hotspots) if warming isn’t limited, according to research published Monday.

Some of the countries facing the most sobering mariculture projections, such as Nigeria, Sierra Leone and the Solomon Islands, also expect some of the highest population growth and accompanying food security demand, even as their seafood resources diminish.

The United Nations Environment Program estimates that half of the world’s population already lives within 60 kilometers of the sea. In these locations, home to mega-cities like Beijing and Buenos Aires, coastal populations are projected to increase by over 50% by 2050, when compared with 2010 levels. Many of these nations have been investing in “blue economy” priorities for sustainable development.

“Low-income countries and the global south, where seafood is central to diets and has the potential to help address malnutrition, are the hardest hit by the effects of climate change,” said lead study author Dr. William Cheung, head of the University of British Columbia’s Institute for the Oceans and Fisheries (IOF).

“For many, seafood is an irreplaceable and affordable source of nutrients.”

The researchers find an average 4% to 7% loss of seafood nutrients per Celsius degree of warming. For lower-income countries across the tropics, it’s approaching 10% to 12% per degree. Cheung says that reducing the warming means reducing the mariculture impacts, degree by degree.

According to the paper, published in Nature Climate Change, the losses could be limited to about 10% of fish, shrimp, oysters, and other mariculture food sources, if the Paris Agreement targets of 1.5°C to 2°C of warming are met. So far, that’s not the pathway on which the planet finds itself.

The research is based on the nutrients themselves, including calcium, iron, protein and omega-3 fatty acids. The authors note that not only are these important food sources in low income countries, but they are food choices associated with protecting heart health and reducing the risk of type 2 diabetes across the world.

What they found is that the availability of the nutrients peaked in the 1990s and flattened into the 2010s. That’s despite increases in food sources provided by farming seafood, and from harvesting more shrimp and oysters. Calcium, already at levels too low for nearly half the world’s people, takes the hardest hit in the future, at up to 40% in the high-emissions scenario.

“Small pelagic (open sea) fish are really rich in calcium so in areas of the world where people have intolerances to milk or where other animal-sourced foods, like meat and dairy, are much more expensive, fish is really key to people’s diets,” said Dr. Christina Hicks of the UK’s Lancaster University. “In many parts of the world, particularly low-income countries across the tropics, fish supply nutrients that are lacking in people’s diets.”

Seafood farming won’t be able to offset the losses from fisheries, either. Under a high emissions scenario, any gains in the availability of nutrients before 2050 would be lost by 2100.

“The primary reason for this is climate change, which is also a significant threat to seafood farming, leaving us with a growing nutritional deficit,” said co-author Dr. Muhammed Oyinlola, a postdoctoral fellow at Canada’s Institut national de la recherche scientifique. “Seafood farming alone cannot provide a comprehensive solution to this complex issue.”

Some adaptation solutions could include using nutrient-dense fish, like anchovies and herring, to feed humans rather than create fish meal. Reducing food waste in production and other parts of the supply chain also can help.