The Great Summer Seafood Swap

By Paul Greenberg, Safina Center Fellow

With the pandemic hopefully on the wane and the tendency to dine out trending in the opposite direction, the temptation arises to go berserk. Why not eat anything we want, we say to ourselves. We’ve denied ourselves for so long.

I’m no scold to splurging, but at this moment in the planet’s climate crisis, let’s think about that splurge and splurge appropriately. So let’s start with the appetizer:

Many of us would like to start off that splurge meal with a shrimp cocktail. But in fact this is about the worst splurge we can make. Shrimp, particularly farmed shrimp, are notably terrible from an CO2 emissions point of view—by some estimates as bad as beef. 

In terms of nutrition per unit of greenhouse gas emissions bivalves (oysters, clams, mussels) beat prawns (aka shrimp) handily. From: J. Z. Koehn “Environmental Impacts of Nutrient Production in the Food System.”

That’s in part because over the last few decades, shrimp farming has destroyed millions of acres of one of the world’s most powerful carbon-sequestering ecosystems: mangrove forests. Mangroves, on average, sequester more than four times the CO2 per acre as tropical rain forests. But it’s mangroves that are most under pressure from shrimp. Shrimp favor brackish coastal waterways, the precise areas that mangroves tend to colonize. Actually wild shrimp get their start in the root webbed channels that mark a healthy mangrove forest. But in order to farm shrimp at scale, growers have often found it more efficient to clear mangrove thickets and replaces them with shrimp ponds.

A mangrove forest near Ca Mau, Vietnam. ©Paul Greenberg

In addition, shrimp must be fed industrial feed pellets that are often composed of fish meal and oil that come from wild fisheries. All this makes a shrimp cocktail an extremely carbon-intensive appetizer.

The good kind of splurge. ©Paul Greenberg

But there is another summer seafood appetizer that you can easily swap in for your splurge. Here I’m talking about oysters. Oysters, and, in fact, all farmed bivalves are extremely carbon-light. They require no feed, subsisting on a diet of wild algae and filtering and cleaning the water as they grow fat. That clever trick puts some bivalves in the same carbon cost range as many vegetables. Mussels, the grand emissions champions of the animal kingdom (and also one of the most affordable seafoods out there), can cost just .6 kilograms of carbon and other greenhouse gasses per kilogram of mussel meat. 

Of course, nothing comes for free. Oyster farms have been known to use pesticides to repress parasites and maximize their yield. Conflicts over how much bay bottom should be given over to oyster growers persist. But I would rather work through those conflicts oyster-by-oyster than participate in the degradation of mangrove forests all for the sake of a shrimp cocktail.

So, oysters anyone?