pike place market salmonTo our BC readers, we realize this Thanksgiving post comes a month late. But as those of us below the 49th parallel make our holiday shopping lists, a study on salmon shows that many of our mental maps about how we eat and buy food—organic vs. conventional, fresh vs. wild—are really too simple.

The conclusion that’s grabbing headlines is that frozen salmon is generally better for the climate than fresh salmon. The authors of the study found that fresh salmon tends to be shipped around the globe in airplanes—consuming prodigious amounts of fuel per pound of fish.  Salmon that’s flash-frozen at sea can go by slower but more efficient rail or container ship.  In the end, they calculate that frozen salmon releases less carbon on its journey from the ocean to the typical plate, marking an apparent exception to the rule that frozen foods consume more energy than fresh.

But before you swear off fresh salmon for fish sticks, there’s more you need to know.  Early results of the ongoing salmon life cycle assessment being done by the Portland-based Ecotrust, Dalhousie University in Canada and the Swedish Institute for Food and Biotechnology are pretty nuanced:

Rather than pushing for organic or land-based production, or worrying about simple metrics such as “food miles,” the study finds that the world can achieve greater environmental benefits by focusing on improvements to key aspects of production and distribution.

What farmed salmon are fed, how wild salmon are caught and the choice to buy frozen over fresh matters more than organic vs. conventional or wild vs. farmed when considering global scale environmental impacts such as climate change, ozone depletion, loss of critical habitat, and ocean acidification.

Unfortunately for anyone standing in front of the fish counter, all of those details do matter. And so does geography. For those of us in the Northwest, the simple eat-frozen-over-fresh rule may not hold:  if you’re eating fresh salmon right off a boat near where the fish was caught, the total emissions may be far lower than for a frozen fillet that made a long trip to the fish counter or grocery freezer.

Sheesh, that’s a lot to keep track of.

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  • For wild salmon, the fishing method also makes a big difference to climate impacts. Salmon caught by purse seiners closer to shore have greenhouse gas emissions an order of magnitude lower than trollers that burn diesel fuel chasing fish with hooks and lines across the ocean, researchers found. They calculated, for instance, that the greenhouse gas emissions released just in catching troll-caught Alaskan salmon were higher than farming, freezing and shipping salmon from Norway to Chicago.

    All of this begs the question: what’s a shopper to do? Sustainable seafood guides tell you to eat Alaska longline cod, and to avoid monkfish, based in large part on how plentiful the fish are. But typically, those guides don’t factor in the diesel fuel burned to catch the fish or emissions associated in shipping it. And trying to figure out the provenance of a piece of fish—much less all the energy that was expended to get it to your dinner plate—is a lot to ask of someone who’s just trying to get through their shopping list.  Heck, calculating carbon footprints is a complicated enterprise even for a grocery conglomerate that just wants to give its customers some decent information.

    Now, multiply the problem with fish by all the ingredients that go into a Thanksgiving dinner. How much can the average person be expected to know about the life histories and production methods for everything from turkeys to squash to cranberries? Sure, there are general principles to live by: it’s a good bet that eating food grown close to home is more sustainable.  Unfortunately, that’s not always the case.

    Here’s a more reliable solution: put a price on carbon. Climate policies and mechanisms that hold food producers and other businesses accountable for their greenhouse gas emissions would make things more transparent for consumers. If policies factor a cost for releasing climate-warming carbon dioxide into the things you eat and buy, things that pollute more would cost more. You’d buy fewer of them. And it might even be easier than calculating the carbon footprint of your grocery list.

    Photo of Pike Place Market salmon courtesy of flickr user Justin Masterson under a Creative Commons license.