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Local v. Imported--How Do We Decide?
Erica Barnett, 13 Aug 07
Article Photo

Conventional wisdom says that we should seek out food that is seasonal, minimally processed, and produced within our local foodshed. (The 100-Mile Dieters, or locavores, take this as close to its logical extreme as you can get without raising all your food in your own backyard.) The reasons to keep it local are intuitive and many: buying local supports nearby farmers, increases the visibility of local farms, improves the local economy, promotes urban agriculture, preserves rural farmland and prevents sprawl, and minimizes the air pollution and greenhouse gas emissions created when transporting our food from farm to table.

Another reason is that local food just tastes better. :ong-transported food can deteriorate on the way to becoming dinner, and so is often bred to be hardy enough to survive trips of many miles at the expense of tastiness . The average head of broccoli travels 2,095 miles from farm to table; the average apple, 1,555 miles. The boom in the number of miles industrial produce travels, along with the widespread desire to have more of a positive impact on local communities and less of a negative one on the environment, has led some advocates to suggest that all food be labeled with "food mile" information, indicating how far it has traveled to market.

A much-covered recent study, however, gave some local-food advocates pause by suggesting that when it comes to carbon emissions, buying local may not be the panacea it appears to be. Researchers at Lincoln University in New Zealand looked at the environmental impact of various foods through a "life cycle analysis" matrix that factored in external factors such as water use, harvesting techniques, the use of renewable energy sources, the means of transport, and storage procedures, among other factors. We've written about their findings before, but here’s the basic claim: Imported food can, in some cases, actually have less impact on the atmosphere than food grown locally and transported to local supermarkets, if all these other factors besides miles traveled are taken into account. The prime example is New Zealand lamb: when shipped to England, it produced a mere quarter of the carbon emissions produced by lamb raised in England's nutrient-poorer pastures. The study reached similar conclusions about New Zealand's apples and dairy foods.

But wait -- it isn't that simple. As critics of life cycle analysis have pointed out, its supporters base their praise on studies of industrial farming methods. (One notable proponent of life cycle analysis is James McWilliams, whose recent New York Times op-ed singing its praises has revived the controversy.) Comparing lamb raised organically on a small pasture to one raised on a factory farm, albeit locally, is hardly apples to apples. Moreover, the study did not include several important factors in carbon production, including the carbon cost of trucking meat and produce from place to place. And the study assumed that fuel and fertilizer would continue to be inexpensive and widely available -- not the safest assumption in a world increasingly impacted by climate change.

What does all of this mean for those of us who want our food to have a minimal impact on the climate? For one thing, it means that we can't rely on simple conclusions from single studies. Yes, there’s more to the carbon impact of food than whether it’s local or not, but in many cases local and organic food may still be the best choice.

It also reveals the need for a single labeling system that goes beyond whether a food is organic and point-of-origin labels to include information such as where the food was produced; whether it's in season; whether it was chemically treated and if so, how; how much water was used to produce it; and whether it was grown by a small farm or massive agricultural corporation.

Carbon labeling shows tremendous promise in unifying all these confusing considerations into a single, easy-to-digest standard. If done right, carbon labeling would go a long way toward eliminating all the sticky decisions and tradeoffs environmentally conscious consumers must now make. But true carbon labeling is still years in the future. In the meantime, the best we can do is measure what we know, decide which factors are most important, and -- most importantly -- buy from stores, and farmers, we know and trust.

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Comments

I believe that a single, standard way of doing life-cycle analysis is critically important (as I had written on another blog one day: "new ISO standard, anyone?"). It only makes sense that we'll find many "counterintuitive" things in such complex systems. To me, it makes little sense to criticize life-cycle analysis as a whole, but very much sense to critique methodology.


Posted by: c! on 13 Aug 07

Actually there's one simple proxy for life-cycle analysis: cost. Under the assumption that our economy is limited by energy supply (which isn't far from the truth), you can trace back all costs to energy inputs - to the extent those energy inputs are fungible, total cost is a reasonable proxy for total life-cycle energy cost. Multiply the price of something by the economic average ratio of MJ per dollar, and then by the CO2 average release per MJ, and you'll not be far off the actual CO2 release for any given product.

Exceptions to this rule of thumb are primarily energy products themselves - obviously a gallon of gasoline purchased and burned has a much higher CO2 release per dollar than the economic average.

The 100-mile diet and advocates of buying local are succumbing to a convenient intuition that doesn't necessarily correspond to reality. Transportation even half-way around the world can be a small fraction of a product's cost and so in most cases also a small fraction of the associated CO2 emissions.


Posted by: Arthur Smith on 13 Aug 07

Actually there's one simple proxy for life-cycle analysis: cost. Under the assumption that our economy is limited by energy supply (which isn't far from the truth), you can trace back all costs to energy inputs - to the extent those energy inputs are fungible, total cost is a reasonable proxy for total life-cycle energy cost. Multiply the price of something by the economic average ratio of MJ per dollar, and then by the CO2 average release per MJ, and you'll not be far off the actual CO2 release for any given product.

Exceptions to this rule of thumb are primarily energy products themselves - obviously a gallon of gasoline purchased and burned has a much higher CO2 release per dollar than the economic average.

The 100-mile diet and advocates of buying local are succumbing to a convenient intuition that doesn't necessarily correspond to reality. Transportation even half-way around the world can be a small fraction of a product's cost and so in most cases also a small fraction of the associated CO2 emissions.


Posted by: Arthur Smith on 13 Aug 07

There are two ways to interpret the findings of the NZ study.

1) Getting lamb onto a British table releases more carbon if it comes from England than if it comes from New Zealand, so Brits should import their lamb.

2) The production of lamb in England is energy intensive, so Brits should not eat so much lamb, and ought instead to eat things better suited to being grown and raised locally.

I prefer the second interpretation, and find it frustrating that the NZ study seems to avoid food choice as a part of the local food movement.


Posted by: greg on 14 Aug 07

What greg points out above is at the root of these issues: local awareness/stewardship.

We all need to consider which foods grow the most efficiently in our geographic/climate area, and become fans of those foods. The First World is so completely spoiled, so utterly used to getting whatever it wants whenever it wants it...so this is going to be a difficult journey.

But it is VERY doable.


Posted by: ProgGrrl on 14 Aug 07

What seems to underly the "cheap sheep" phenomena is the fact that water transport is by far the cheapest way (carbon emissions and otherwise) to get a product from point a to point b; so for anyone living on the coast, it is most likely that goods from near another port on the other side of the planet have less of a carbon impact than goods from 500mi away.

Obviously the other life-cycle issues matter quite a bit, but the huge difference between land and sea transport doesn't seem to get as much attention as it deserves.


Posted by: Ethan Fremen on 14 Aug 07

Perhaps it would help to focus less on any one food item and more on our overall diets. Arthur Smith's analysis is helpful, but assumes that monetary price accurately reflects actual environmental and social costs - probably not the case. A better proxy might be the ecological footprint of an overall diet.

I live in Maine - our household raises about 25% of our diet, and about another 30% to 40% - especially animal foods - comes from local sources. I'm fairly sure these choices lower the ecological footprint of our diet. But it would be absurd for us to push the local preference too far, so long as we want to drink tea, cook with olive oil, and so on.

So we seek a balance and an awareness of our overall impact. I'm pretty sure that the local, grass-fed lamb I had for supper last night, accompanied by beans and corn from our garden, helped "offset" the ounce of dried tea from Sri Lanka that I had at breakfast this morning, with my local blueberries and yogurt from 275 miles (445 km) away. I'm also pretty sure that my local lamb was a better choice than tofu made from soy planted in Brazil on land cleared from a rain forest. And I'm confident that importing the tea was much more sensible than trying to grow it here in a heated greenhouse.

No reductionist analysis of any one foodstuff will tell us what we really need to know: how can billions of people nourish themselves without undermining the planet's ecological systems?


Posted by: David Foley on 14 Aug 07

Carbon labeling does already exist, in a commercial context: http://www.walkerscarbonfootprint.co.uk/walkers_carbon_footprint.html

Many bags of Walkers crisps (chips for the US) already have a label which tells me how much CO2 was produced in it's production (e.g. 75g for a 25g bag).


Posted by: John Kazer on 15 Aug 07

Lets take greg's point to its logical conclusion. If we can just close our boarders to trade and eat only the things that we can produce efficiently locally then we can solve all of our carbon problems!

... Or we can retake Econ 10 and forget this silly line of thinking.


Posted by: Chaz on 15 Aug 07

How about food shopping with a local bias? Here is my own example. Living on the east coast of the US, I eat Florida oranges, Southern Peaches, and Northern apples. When local vegetables are available, I get those. I weight local over organic. Usually, costs are lower for these fruits and vegetables. Surely, I am reducing food miles and energy inputs, and getting fresher foods even though every single decision I make may not be correct.


Posted by: Tom L on 16 Aug 07



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