Does It Really Matter Whether Your Food Was Produced Locally?

The local wits in Salina, Kansas, like to say the easiest way to for us "eat locally" around here is to heat up a Tony's® frozen pizza. It's not just that Tony's has a large plant on the west side of town. Salina is also surrounded by wheat fields and is home to a large flour mill. Our local pizza, at least theoretically, could be assembled on a local crust.

But our hometown pizza can be considered local only if we ignore the many miles ingredients like tomato sauce, cheese, pork and beef travel to reach the plant. To that should be added the highway or rail miles logged by the cattle and hogs who gave their lives for the pizza; the distances that feed grains and soybean meal traveled to reach the feedlots, dairy farms and hog-confinement facilities where the animals were raised; the trips that tomatoes took to the sauce factory, and the miles that fertilizers and other inputs were hauled to reach the fields where the tomatoes were grown.

We eat lots of high-mileage meals. In 1997, the distance traveled by an average food item from its site of production to the average U.S. grocery store (counting only the delivery distance, not the transportation involved in production) was 980 miles. In the next few years, food imports shot up dramatically; as a result, by 2004, the average food item was traveling 1,230 miles.

That is widely viewed as an undesirable, if not absurd, situation. The Seattle Times, for instance, advises, "Transportation of food requires copious amounts of fossil fuels and other resources that contribute to global warming and pollution, so the lower the food mileage we rack up, the better."

In a report stressing the need for more localized food, Iowa State University's Leopold Center analyzed two healthful vegetarian dinners consisting of rice, stir-fried vegetables and salad. The first was prepared with ingredients from a family garden, a farmers' market, and a food co-op; the second was put together from fresh, store-bought ingredients. Adding up the lengths of trips taken by all 13 ingredients from farm to kitchen, the first meal--despite efforts to localize--had logged 3,445 miles. It scored well, however, compared with the second, conventionally prepared meal, which had traveled 22,100 miles--circling the earth, figuratively speaking. But does that Iowa meal teach a useful lesson about the national or global food system? In other words ....

Do Food Miles Even Matter?

With rising demand for localization of food production, the concept of "food miles"-- first formulated in the early 1990s and generally understood as the sum of miles a given quantity of food travels from the point of production to the point of final sale or consumption -- remains a popular indicator of sustainability. A quick news search last week turned up 70 articles in the previous month that included the term "food miles."

Reducing food miles, local-food advocates argue, will not only reduce carbon emissions by shrinking transportation networks but will also help ensure that food is produced more responsibly and is of high quality. Although food from nearby sources is desirable for many such reasons, research over the past few years has shown that simply calculating food miles in the absence of other information does not capture the complexity of the food system in a way that is useful to the well-intentioned eater.

In a much-cited 2008 paper (pdf), Christopher Weber and Scott Matthews of Carnegie-Mellon University calculated that per U.S. household, the shipping of food from farms to retail outlets racks up 3,000 ton-kilometers per year (which could be accumulated by any combination of weight and distance -- for example, by hauling three metric tons of food 1,000 kilometers). This is what they called the "final delivery" leg of the food chain, the part normally used in calculations of food miles.

But, say Weber and Matthews, we should also take into account food production, which requires that other materials (for example, fertilizer, fuel and animal feed) be hauled a total of another 9,000 ton-kilometers per year per household! In sum, transportation for production plus delivery comes to 12,000 ton-kilometers annually. That consumes a lot of energy and produces a lot of greenhouse emissions; however, transportation has far from the biggest climate clout in the food business. Final-delivery food miles, the focus of many localization efforts, account for only 4 percent of the food system's total emissions.

How food is grown and processed and how it travels would seem to be much more important that how far it travels. Per ton of cargo, modes of transportation differ greatly in their global-warming potential and other environmental impacts. Hauling a ton of food one mile by truck emits 16 times the emissions created by hauling a ton of grain for a mile by oceangoing ship, or nine times the emissions from hauling it by river barge. Importation of food into the United States rose a staggering 25 percent between 1997 and 2004. But because international trade is dominated by ocean-shipping, food-miles emissions increased by only about 5 percent during that period.

Local or not, some types of foods account for a far bigger share of total emissions than do others. Factory-farmed beef and pork, for example, are spectacularly climate-unfriendly. Weber and Matthews concluded that by shifting only about 20 percent of its red-meat consumption to grains and vegetables, a household could achieve the same emissions reductions that would result from totally eliminating final-delivery food miles with a radically local diet.

The Wandering Sandwich

In the United Kingdom and other northern European countries, where diets are more import-heavy than in the United States, food miles have been a topic of intense debate and research for years. In a 2004 review of the evidence (pdf), the UK's Department for Environment, Food and Rural Affairs (DEFRA) concluded, "The impacts of food transport are complex, and involve many trade-offs between different factors. A single indicator based on total food kilometers traveled would not be a valid indicator of sustainability."

That complexity is exemplified by foods whose local production is highly resource-intensive; hauling such products long distances can actually reduce climate impacts. According to DEFRA, a UK grocery chain that imports field-grown tomatoes from Spain causes only one-third the carbon dioxide emissions that it would cause by buying domestic, greenhouse-grown tomatoes.

Last year, Caroline Saunders and colleagues at Lincoln University in New Zealand reported that because of the large quantities of energy required to raise lambs in northern Europe relative to New Zealand, UK residents could reduce their carbon emissions associated with lamb-eating more than three-fourths by buying meat raised in New Zealand rather than in the UK--even when the carbon cost of shipping meat halfway around the world was accounted for. Obtaining dairy products and out-of-season apples from New Zealand (with its reverse seasons) rather than producing and storing them for months in the UK could, they projected, cut the resulting greenhouse emissions as much as 50 percent.

One conclusion to be drawn from such studies is that given current production systems, eating red meat or out-of-season fresh fruits and vegetables is going to generate a lot of climate-altering emissions, whatever distance they travel.

Large British grocery chains now ship virtually all of their goods through their own regional distribution centers (RDCs), greatly increasing average food miles but giving small-scale food-growers a boost. By hauling their vegetables to the nearest RDC, says DEFRA, "smaller producers can gain access to national chains of shops, substantially expanding their market areas."

There is, however, a twist: the system makes it "virtually impossible" for small farms or processors to deliver directly to chain stores in their local area. "A sandwich company in Derbyshire," notes DEFRA by way of example, "supplies its products to a major supermarket chain and has a plant within a few hundred meters of one of its shops. The sandwiches arriving on this shop's shelves, however, have to be routed through one of the retailer's RDCs on a round-trip of approximately 160 kilometers."

Here in the United States, Wal-Mart, the largest grocery seller, pledged in 2008 to purchase more locally grown produce and claimed that 20 percent of its summertime produce stock was local; however, the company defined a source as "local" if it is in the same state as the purchasing store, even if the farm is large and ships nationally.

Flying Beans

Air transport accounts for a very small share of total U.S. food miles, but it emits outrageous quantities of greenhouse gases for the quantity of food delivered; as a result, air shipping accounts for about 7 percent of total U.S. food-transport emissions. Although a boycott of air-freighted meat or produce would make only a modest difference in overall emissions, it would have maximum impact per pound of food.

Because Europe does not have America's wealth of arable land in widely diverse climatic zones (or our vast low-wage agricultural labor force), food shipped to the continent by air has created a large and growing emissions problem. The International Institute for Environment and Development (IIED) calculates, for example, that flying a ton of produce from South Africa to the UK results in 150 times the greenhouse emissions that are generated if it's hauled by ship or if, instead, it is grown in Spain and trucked to the UK.

Kenya supplies by far the largest share of fresh produce being air-freighted from Africa to Europe. Despite the enormous per-pound climatic impact of Kenya's "flying vegetables" (pdf), IIED and Oxfam Great Britain have opposed moves by some European grocery chains to cut or abolish air-freighting of fruits and vegetables from Africa. The groups stress that air-shipped produce has sparked an agricultural boom in some parts of Kenya and that cutting off that trade could cripple those rural economies. They maintain that the greenhouse emissions resulting from that trade, while preposterous when tallied per package of green beans, are not significant in the larger picture. They write:

Kenyans contribute very little to the global emissions burden. And what is more, the entire airfreight trade in fruits and vegetables between the UK and Kenya adds a mere 0.1 per cent to the UK's total emissions. So in effect, Kenyans--as well as other Africans--have a lot of 'room to move', ecologically speaking. Given the industrialized world's historical responsibility for emissions, and its current high per capita emissions, is reducing its carbon footprint from 10.60 to 10.59 tonnes really worth imperiling 1 to 1.5 million livelihoods?

As an argument for saving people from short-term economic ruin and hunger, Oxfam's and IIED's support for flying vegetables -- what they call "fair miles" rather than "food miles"-- makes perfect sense. Yet, in a more economically rational world, it could be argued, people in Africa would be using their fragile soil differently. They would be free to achieve food security in a more sustainable way, rather than having to resort to exploitation of their soil and water to feed the export market, only to turn around and eat imported food staples.

IIED and Oxfam argue that efforts by the Kenyan government to support growers of maize, the country's chief staple food, have been undermined by market forces; therefore, they say, vegetables for export have been a lifesaver. But the country's food deficit is ballooning. Imports of staple grains, the foundation of Kenyan diets, have increased dramatically in recent years. This year, the country will have to import more than 40 percent of grain consumption. Food miles like that are not a luxury that can be dispensed with in the short term; they are a matter of survival.

Feeding Connecticut

In the United States, we have a little more than one acre of cropland per person -- more than enough land, if used properly, to feed our population. But the bulk of our fertile, croppable acreage lies a long way from the majority of our population. For example, Nebraska has 13 acres of farmland per resident, while Connecticut's per capita endowment of farmland is a mere one twentieth of an acre.

Our fundamental biological requirements will continue to dictate that vast volumes of staple foods be hauled from land to people over long distances. It's true that many of us are eating too much in the way of the major nutrients -- carbohydrates, fats and proteins -- and not enough of nutrients like vitamins that are needed in far smaller quantities. Nevertheless, every day, the nation's food system must deliver basic nutrients to more than 300 million Americans, each of whom will require a couple of thousand calories and a few dozens grams of protein, along with many other compounds.

The majority of the foodstuffs providing those nutrients, either indirectly (as when they're fed to animals) or directly, are cereal grains, grain legumes and oilseeds. Most of those crops are grown hundreds or thousands of miles from the homes of the people who require them. Fortunately, wheat, oats, pinto beans and other grain crops are dry, compact and not highly perishable, and they can be hauled long distances by rail at a low environmental cost per quantity of nutrients moved; a ton of wheat contains 17 times as much caloric energy and protein as does a ton of fresh tomatoes.

Food miles expended to deliver water-heavy fresh products -- usually by truck rather than by more fuel-efficient rail -- have a high emissions-to-nutrients ratio. When it comes to food miles, local food movements are right on target when they zero in on fruits, vegetables and dairy products.

(A footnote on meat: If there were a big shift away from factory farming of livestock toward more environmentally responsible methods of raising grass-fed animals, that would reduce the meat industry's total energy use and climate emissions. But because large expanses of grasslands lie far from most cities, delivery miles to urban markets would not be reduced significantly.)

Even for fruits and vegetables, "local" will have to mean "regional," not "around the corner." As I pointed out last year, if Americans planted food on every residential lot in the country, we would have enough yard space to substitute for only about 70 percent of current vegetable, fruit and nut acreage (and would mean wiping out most of the shade trees on home lots). Some urban areas are starting to be ringed with more fresh-food production, and that has helped expand local capacity. But as long as there is broad demand for fresh produce in winter and spring or as long as Americans want strictly tropical products like bananas, fresh-food miles can be reduced, but they won't be eliminated.

In a 2006 article (pdf) that warned against falling into what they call the "local trap," Branden Born and Mark Purcell of the University of Washington wrote that the concepts of "local" and "sustainable" are not synonymous. Given a specific goal, wrote Born and Purcell, it is important to choose the most effective strategies whatever their scale, rather than assume that local strategies will always work best. And as I have argued before, repairing the broken system that supplies the bulk of the nation's diet will, above all, require breaking the political chokehold agribusiness maintains on federal and state governments. The bottom line: Keep an eye on your food miles, but keep a closer eye on your food's history.

Meanwhile, with that in mind, I can't say that I'd recommend our local frozen pizza, whatever the distance it travels.