Thursday, August 26, 2010

Why Food Miles are Misleading

The New York Times just printed an article titled Math Lessons for Locavores. It points out some of the flaws in focusing on food miles to improve the environment.

Food miles are one of the places where arguments for local food and environmentalism overlap. If you haven't heard the term before it refers to how many miles a food has to travel from where it's made to where it's eaten. Proponents say fewer miles are better.

The main thrust of the article is that food transportion costs are a small percentage of our nation's energy bill overall (2%) and that reducing energy in our home kitchens (refrigerators, appliances, etc) would have much greater environmental effect.

It also points out that a crop grown in a suitable environment, then shipped to where people who eat it is often a more environmentally sound practice than growing a crop in a place that isn't suited to it just because it's local. I talked about this in my post on sugar.

Fair enough. Yet I think the author misses an even larger point. We shouldn't ignore food miles because there are other ways to do better by the environment. We should debate food miles because they may  just be plain wrong. That's because nearly every time you see them they're discussed as a whole number. But they're really a fraction. Let me explain with some maths.

You'll usually come across statements about food miles that read like this: "California strawberries travel 2,500 food miles to be sold in Michigan."

That's a big number. It makes you think each strawberry traveled 2,500 miles to get to you. Yes, it did. But it was in a train car with thousands of other strawberries. To really understand the environmental (energy) impact we need to calculate the miles per strawberry. As soon as we say that — add the word "per"  as in miles per strawberry— we've created a fraction.

So let's go back to the statement. California strawberries travel 2,500 food miles to be sold in Michigan. Then let's add another key fact: a train car holds 250,000 strawberries.

Now the food miles per California strawberry are:

2,500 miles / 250,000 strawberries = .01 miles per strawberry (about 52 feet)

Now, as a point of comparison, let's take Joe Green at the local Farmer's Market. His strawberries travel 40 miles to be sold. (20 miles each way, and we have to count his return trip because while Joe goes back to his farm with an empty truck train cars return to California full.) Let's say Joe sells 4,000 strawberries.

Now the food miles per Joe Green strawberry are:

40 miles / 4,000 strawberries = .01 miles per strawberry (52 feet) -- identical to the Californians.

I guess "Food Feet" don't sound as compelling as Food Miles. And 52 feet sounds pretty boring next to 2,500 miles. The fact that Californian strawberries may actually travel the same distance as a local one from Michigan -- well, I think it's interesting, but I'm not seeing a lot of articles written about it.

And of course trains are a lot more fuel efficient than Joe's old Ford Ranger. But that's another post.

Final caveat: food miles aside, there are plenty of reasons to buy from local farmers, not the least of which is the food often tastes better.

I explained a similar situation to this in my post Does Buying Local Reduce Fuel Consumption?.

1 comment:

Jen said...

Very good point! Navigating the ethical food world is very difficult. It makes a person want to give up and drown their woes in bacon.