Checking the food odometer

By RICH PIROG

A lot has been written about food miles since the Leopold Center published the “Food, Fuel and Freeways”report two years ago.

In that report, we found that under a conventional system many food items travel an average of about 1,500 miles from where they are grown to get to where they are purchased. We also found that the distance food travels to reach the consumer has increased compared to 20 years ago.

I’ve been fielding a lot of calls and e-mails about this work, and have come up with a few questions of my own. Does “locally-grown” mean the same thing for Iowa squash as it does for strawberries? How do the miles logged by locally grown fruits and vegetables compare to those coming to Iowa from across the country? Does it vary by the type of produce?

To answer these questions, ISU student Andrew Benjamin and I looked at records of 160 sales transactions that were part of food brokering efforts at Practical Farmers of Iowa (PFI). The transactions were for fresh fruits and vegetables from 34 Iowa farms sold in 2001 to 23 conference centers, hotels and other institutions in central Iowa. Using a formula representing both distance and weight of load transported, we calculated a weighted average source distance for 16 produce items in the PFI transactions. chart showing distance traveled

We then went to information collected by the USDA’s Agricultural Marketing Service for the same types of produce that arrive by truck at the Chicago and St. Louis terminal markets. We had to estimate where these items would likely have originated, and we used only sources within the continental United States responsible for at least 50 percent of U.S. produce arrivals. We were able to use this information to calculate a weighted average source distance for the produce items in a conventional system, substituting the weights of the PFI-brokered transactions so comparisons could be made with the locally grown distance data.

We found that locally grown produce traveled an average 56 miles from farm to point of sale; the average distance was 1,494 miles – nearly 27 times farther – if those items had come from conventional sources within the continental United States. Another perspective on this comparison is that the locally grown food spent about an hour in transport (assuming an average truck speed of 55 miles per hour) compared to 27 hours for the conventional produce.

The comparisons varied widely by the type of produce. Broccoli shipped under the conventional system traveled more than 90 times farther than locally grown broccoli. Carrots and sweet corn traveled approximately 70 times farther than their local counterparts.

Here’s another way to think about it: The sum of the average travel distances for the 17 locally grown produce items in our study totaled 716 miles, about the distance between Des Moines and Denver. The sum of the average travel distances for conventional produce was 25,301 miles, roughly a trip from Des Moines circling the earth pole to pole, plus 440 additional miles north almost to the Canadian border!

We restricted our study for conventional produce to the continental United States. However, an increasing proportion of what we eat comes from outside the United States, including 39 percent of the fruit, 12 percent of the vegetables, and 78 percent of the fish and shellfish. Had we included international data, travel distances would have been even farther for certain produce items in the conventional system.

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