The environmental costs of producing meat, seafood

Which food type is more environmentally costly to produce—livestock, farmed seafood, or wild-caught fish? The answer is, it depends. But in general, industrial beef production and farmed catfish are the most taxing on the environment, while small, wild-caught fish and farmed mollusks like oysters, mussels, and scallops have the lowest environmental impact, according to a new analysis. Published in the journal Frontiers in Ecology and the Environment, the authors believe the study is the most comprehensive look at the environmental impacts of different types of animal protein production.

The study is based on nearly a decade of analysis, in which the co-authors reviewed hundreds of published life-cycle assessments for various types of animal protein production. Of the more than 300 such assessments that exist for animal food production, the authors selected 148 that were comprehensive and not considered too specialized to inform their new study. Broadly, the study uses four metrics to compare environmental impacts across the many different types of animal food production. The four measures are: energy use, greenhouse gas emissions, potential to contribute excess nutrients—such as fertilizer—to the environment, and the potential to emit substances that contribute to acid rain. The researchers compared environmental impacts across food types by using a standard amount of 40 g of protein—roughly the size of an average hamburger patty, and the daily recommended protein serving.

The analysis showed clear winners that had low environmental impacts across all measures, including farmed shellfish and mollusks, and capture fisheries such as sardines, mackerel, and herring. Other capture fish choices with relatively low impact are whitefish like pollock, hake, and the cod family. Farmed salmon also performed well. But the study also illuminated striking differences across animal proteins, and the researchers advise that consumers must decide what environmental impacts are most important to them when selecting their food choices.

Overall, livestock production used less energy than most forms of seafood aquaculture. Farmed catfish, shrimp, and tilapia used the most energy, mainly because constant water circulation must be powered by electricity. The study also found that catfish aquaculture and beef produce about 20 times more greenhouse gases than farmed mollusks, small capture fisheries, farmed salmon, and chicken.

Interestingly, mollusk aquaculture—such as oysters, mussels, and scallops—actually absorb excess nutrients that are harmful to ecosystems. In contrast, livestock beef production rated poorly in this measure, and capture fisheries consistently scored better than aquaculture and livestock because no fertilizer is used. Because livestock emit methane in their manure, they performed poorly in the acid rain category. Farmed mollusks again performed the best, with small capture fisheries and salmon aquaculture close behind.

“I think this is one of the most important things I've ever done,” said lead author Ray Hilborn, a University of Washington professor in the School of Aquatic and Fishery Sciences. “Policymakers need to be able to say, ‘There are certain food production types we need to encourage, and others we should discourage.’”

Abstract