In newsletters #1 and 15 I’ve tried to scratch the surface on how what we eat affects the climate. The problem is huge: it will be impossible to slow climate change without seriously addressing what we eat and how it is raised. The simple and quick thing that almost everyone can do is to reduce or eliminate meat from ruminants — cows, sheep and goats.
Several people have written to me to say that they were eating a lot more fish in place of red meat. Jean & I have been doing the same thing, but I’ve had a nagging feeling that I should look further into fish as a primary protein source. Well, I’ve found that it is very complicated!
WILD FISH
The carbon footprint of some wild caught fish comes in pretty good. Ninety percent of greenhouse gas emissions from wild caught fish come from the fuel used to catch and transport them. The most efficient are small prolific species like herring, mackerel and anchovies — as little as 80 liters of diesel fuel per ton of landed fish. Other fisheries consume far more fuel — as much as 10,000 liters per ton of catch in some of the fisheries catching lobsters and Australian Tiger prawns.
Small fish towards the bottom of the food chain also contain lower levels of toxins. In contrast, most larger carnivorous fish have accumulated high levels of methyl mercury, PCBs and dioxin — all dangerous toxins, most of which come from burning coal. Gulf tilefish, shark, marlin, swordfish, the larger species of tuna, and lobster are all so contaminated that you should only eat them occasionally. Pregnant women and children should avoid them entirely. In addition, much more fuel is generally expended in catching these species, giving them a higher climate impact. Dietary recommendation for fish.
FARMED FISH
Aquaculture is already a very important food source in Asia, and worldwide we now eat more farmed fish than wild. Most of our shrimp comes from farms in Asia and Ecuador, while most fin fish, like salmon, comes from Canada, Norway and Chile.
The ecological footprint of farmed fish runs the gamut, from very good to horrific. By far the best are mollusks like mussels, oysters and scallops — they require no feed, help clean the water they live in, and sequester large amounts of carbon in their shells. Finally, their culture requires very little energy input. In fact farmed mollusks may have one of the lowest carbon footprint of any animal protein.
Farmed fin fish like salmon and sea bass have a higher footprint, as they require feeds made from plants, fishmeal (from wild fish) and animal trimmings. But a great deal of progress has been made in lowering the ecological impact of this technology: the feedstocks are more sustainable, the use of antibiotics is far less, and seabottom pollution has been greatly reduced. These species convert their feed more efficiently than land based farm animals, and in the final analysis, fish like salmon have a lower carbon footprint than eggs, chicken and pork, and are vastly better than beef and lamb. In addition, they have much lower toxicity levels than wild fish.
But be careful with farmed shrimp and talapia. Practices vary widely, but many shrimp farms are built by clearing mangrove swamps, hugely destructive to the coastal environment and a big source of atmospheric methane pollution. Many other farms use fish in rotation with rice, which also has big methane problems. Talapia has proven to be a very invasive species, with aquaculture a major source of spread. Some catfish farms have also proven to be serious methane producers.
So, eat more fish, but do it wisely!
A diet that includes fish is much more sustainable than one based on red meat, and a substantial improvement over one high in pork and chicken. Your doctor will give it two thumbs up. Eat more sardines, mussels, clams, oysters and scallops. Eat less tuna, and save swordfish, shark, marlin and other big predator species for special occasions. Same for lobster. Farmed salmon is a safe choice. If you’re shopping for shrimp, either buy wild caught or do some research on the source. Before you order shrimp in a restaurant, ask where it came from.
And now, the fine print:
Oceans cover 70% of the planet, but they are already being harvested at the maximum sustainable level — and that’s being optimistic. Fisheries management has greatly improved for some cold water species, but historically it has an abysmal record of protecting fish stocks, and laws are largely ignored in many parts of the world. We will need to be strong advocates for effective management to save this invaluable resource in the face of the global disruptions that climate change will likely bring.
Aquaculture will need to be greatly expanded if we wish to replace red meat with fish in our diets. In Maine (which has some of the best sites for farming cold water species) every aquaculture permit is fought tooth and nail by a potent coalition of shorefront property owners (who don’t want anything in their view) and fishermen (who don’t want to share their waters).
Many people object to fish farms on ecological grounds. But aquaculture technology has improved greatly in the past 20 years, and dredging up questionable horror stories from the past is not helpful — we are looking down the barrel of a vastly greater ecological disaster.
Decisions about what fish to eat inhabit a confusing matrix: heart and neural health, toxicity, habitat destruction, sustainable harvest, indigenous rights. Climate impact is only one factor.
I’ve tried to offer some simple guidance, but be aware that there are exceptions in almost every case. Lobsters caught in New Brunswick, Canada, have a lower carbon footprint than those caught in Maine. Some species of wild shrimp are fished after they have shed their eggs — we can harvest every one and not impact the resource.
For a through description of the many advantages of aquaculture: NOAA
Thanks for reading,
Doug Hylan, Brooklin, Maine
“Even if you never have the chance to see or touch the ocean, the ocean touches you with every breath you take, every drop of water you drink, every bite you consume. Everyone everywhere is inextricably connected to and utterly dependent upon the existence of the sea.” — Sylvia Earle
I worked for a sardine company one summer forty years ago. Interestingly, the largest US 'market' for sardines at that time was prisons. Cheap protein, I suppose.