Shorter trial column

Some of the feedback I got in response to the trial fact check column I posted a couple of weeks ago was that I should try making it a good deal more concise.  I’m also interested in seeing how it flows without the conceit of the fake letter from a reader, so here’s my attempt at doing both of those things.


Is local food really better for the climate?

Reusable Bag

photo by Liz Throop

A few years ago, The Economist ran a provocative piece attacking the local, organic and fair trade food movements.  As usual, it had plenty of true facts in it, but made some leaps beyond the evidence because the author was so keen to make a contrarian point.

In this post I’ll only look at one of the claims they made: that local food is no better for the climate than what’s been trucked in.  Specifically: the claim that whatever harm is reduced by not shipping the food so far is outweighed by inefficiencies of the trendy small-scale food system.

One of the arguments for buying local is that typical supermarket food travels shockingly large distances from farm to table.  According to the Leopold Center for Sustainable Agriculture, the average vegetable travels 1,518 miles by truck before we get to eat it.  I couldn’t find an estimate for how far the average vegetable sold at a farmers’ market traveled, but we can do better: you can find out exactly how far your produce came by asking the individual traders.  In my case, the average is about 100 miles – less than a tenth of the distance that its supermarket equivalent has travelled.  Sounds impressive, eh?

When I think of the tomato that’s traveled 1,500 miles I think of an individual heroic fruit that’s outdone the Proclaimers in its single-minded dedication to get to me.  But our transport system is more efficient than it looks, mainly because we can pack so much into one truck.  On average, according to that same Leopold Center report, hauling a pound of food 1,500 miles only causes half a pound of CO2 emissions.  To put this in perspective, that’s the equivalent of burning 6½ tablespoons of gasoline.  Not such a huge impact, and it’s one you could easily swamp by driving a gas-guzzler to the farmers’ market.

As just one example, if the local produce is grown in a greenhouse then a surprising amount of energy will have been used to heat that greenhouse.  A typical greenhouse uses 22-31 KWh per pound of tomatoes grown.  At the average carbon intensity for electricity in the U.S., that translates to 29-42 pounds of CO2 emissions; about 70 times as big an impact as the shipping.

On the face of it, The Economist seems to have a point.  The environmental impact of food miles is often overstated.  But if we leave it at that, we miss some really crucial things.

So far, I’ve compared a relatively clean example of long-haul food—the efficiently loaded truck—with one of the most energy-intensive kinds of local food.  But reality has an awkward habit of being a bit more complicated than that.

What if the long-haul food were fish shipped in from Japan, as some sushi bars round here proudly advertise?  That fish has traveled much further than the average tomato, it had to be kept refrigerated on the way which itself uses a lot more energy, and to be fresh when it reaches us it had to be flown in, using far more fuel than a truck.  All this for something that could have been caught locally.  As a general rule, the more perishable and delicate the food, the more food miles do matter.

Foraged & Found Edibles -- Lobster Mushrooms Macro

photo by Brian Glanz

On the local side, our veggies don’t have to come from a greenhouse burning energy to grow tomatoes because it’s either in the wrong place or out of season.  When crops are naturally in season where you are, they don’t need heating, artificial light or long-haul shipping.  If you’re not sure what’s in season when, you can always ask the farmer.  At least you can at the market, which is one of the harder-to-quantify advantages that a local food system has over a typical supermarket.

There are all kinds of non-climate advantages to a varied local food system.  They’re off-topic for this post, but they do matter and if you’d like to learn more here are some good starting points:

After all that, what have we learned?  Well, food miles alone are a much less big deal than they sound like they should be, and local food can cause surprisingly large amounts of emissions.  On the other hand, the more perishable the food, the worse the impacts from transporting it, and food that’s in season locally is far less environmentally damaging than food out of season, wherever it came from.


That’s about a third shorter, which isn’t quite as short as I wanted it.  I’m finding myself stuck between wanting to keep the reasoning transparent and wanting to make it shorter and snappier.  I think part of the problem might be that I get attached to what I’ve already written, and part is that writing a shorter, snappier column requires a more narrowly focussed topic, so I’ll try a new topic later this week.  Meanwhile, how does this one read?  Does it read better this way, and/or have I taken too much out?

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