when switching to seafood helps – and when it doesn’t


Small fish, like mackerel, have high nutritional value and a low carbon footprint.Credit: Getty

Replacing meat with certain types of sustainably sourced seafood could help people reduce their carbon footprint without compromising nutrition, according to an analysis of dozens of marine species eaten around the world.

The study, published September 8 in Earth & Environment Communications1suggests that farmed bivalves — shellfish such as mussels, clams, and oysters — and wild-caught small surface-dwelling (pelagic) fish, which include anchovies, mackerel, and herring, generate less greenhouse gas emissions and are more nutrient dense than beef, pork or chicken.

The research aimed to “better understand the climate impacts of seafood through the lens of a wide variety of nutritional qualities,” says co-author Peter Tyedmers, an ecological economist at Dalhousie University in Halifax, Canada.

The findings echo those of previous studies, including work by members of Tyedmers’ group who focused on seafood consumed in Sweden.2. This time, the researchers wanted to include a more diverse global range of seafood, says Tyedmers.

Benefits of the “blue” diet

Food production accounts for about a third of global greenhouse gas emissions, mostly methane and carbon dioxide3. More than half of these emissions are due to animal husbandry4. Plant-based diets offer a lower-impact alternative to eating meat, but solutions tend to overlook the benefits of seafood-based, or ‘blue’, diets, the study finds.1 said.

Using 41 species of seafood, the researchers came up with a nutrient density score that took into account essential nutrients, such as certain fats and vitamins. Species studied included farmed and wild fish, crustaceans, bivalves, and cephalopods (the group that includes octopus and squid). The team then used available emissions data for 34 of these species to compare their nutrient density with the emissions associated with their production or capture.

BEST FRY FISH.  Chart showing that some seafood has higher nutritional value and lower emissions than meat.

Source: Ref. 1

Half of the seafood species offered more nutritional value for their money in terms of emissions (see “Best Fish to Fry”). Wild pink salmon (Oncorhynchus gorbuscha) and red salmon (Oncorhynchus nerka), as well as wild-caught small pelagic fish and farmed bivalves, were the best choices for nutrient-dense, low-emission protein sources. Whitefish like cod (Gadus sp.) also had low climate impact, but were among the least nutrient dense foods. Wild shellfish had the highest emissions, with a carbon footprint that rivals only that of beef. The authors note that their emissions data does not include “post-production” emissions, such as those generated by refrigeration or transportation.

The analysis adds more perspective to the role of seafood in food systems, says Zach Koehn, a marine scientist at the Stanford Center for Ocean Solutions in California. He adds that one of the barriers to applying this research will be the need to make seafood more widely available at an affordable price, as those who could benefit the most from nutrient-dense foods may not have access to it. .

Tyedmers agrees that access to diverse diets is a privilege. “Every opportunity to replace beef with seafood is a small win for the climate,” he says. “It doesn’t have to be at every meal.

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