You know what would be truly progressive? Calculating how much suffering different food choices cause. You know -- caring about more than just one's self.

"Well, perhaps, if you don't factor in elements like the 10-mile round-trip drive to the grocery store by each person who wants to buy some of those 48,000 bananas."

Talk about faulty logic! People are going to make trips to the store to buy bananas regardless of where those bananas came from. The real point here, then, is whether certain kinds of food tend to induce higher fuel consumption spent traveling to the store per item purchased. And there's a very strong case that mega-markets, like (gasp!) Wal-Mart, minimize this consumption. These establishments tend to also have more mass-produced, imported food.

Murray's point is very valid: if the transportation cost in going to buy groceries is orders of magnitude greater than the cost of transporting those groceries from their original location, then we should be much more concerned about the former.

Don't eat bananas.

If it can't be raised locally, don't eat it. Coffee, tea, spices—buh bye. You can't cheat by uttering "Fair Trade" either. Not one cent to foreigners for food.

Bill Cowper, is that a joke? Why the fanaticism?

The "buy local" movement is one of the most spectacular examples of misplaced activism I've seen, managing to construct a reactionary view of trade atop barely cogent concepts like "food miles."

What are the facts?

Fact 1: The level of carbon emitted in transporting food from its source to the store is a trivial fraction of global carbon output, and isn't necessarily any larger than the carbon you emit while driving to the store. Travelling extra miles to find a specialty store or farmer's market selling local produce can actually be counterproductive.

Fact 2: Food is often transported long distances for a very good reason: different climates suit themselves to very different kinds of food production. Rather than growing many kinds of food in each locale, regardless of the inefficiency, trade allows regions to specialize, with extremely positive consequences for agricultural productivity. (and possibly the environment)

Fact 3: The "treatment and wages" of impoverished agricultural workers overseas isn't going to improve if you adopt a blanket policy of buying local. Their poverty will only get worse.

Mega-markets are monumentally inefficient in selling produce, with some exceptions like bananas.

The rough schema is that managers select suppliers of products that they know little about to be taken care of by the staff than can't afford to know anything about those products to customers who know little. The end result is that only the hardierst and best looking varieties can survive this brutal system, and forget about details like taste. Which is quite OK with bananas that do not have much taste, are very durable and travel well (an opinion that is subject of change after visiting a farmers' market in Equador, I guess).

A little example: an ethnic Turkish store in Germany offers fruits at less than half of price of American supermarket, and that with super-strong Euro and produce largely comming from Euro zone. To be precise, 1 Euro per kilogram of apples and pears, which translates to 66 US cents per pound. Some varieties are "ugly" and they are popular because they have local tradition and customers know that they are tasty.

Now, if you have no idea what are different merits of different varieties of fruit and vegetables, you can go to Markt in the center of the city and converse with the sellers, who offer much larger variety of produce than an American supermarket (and a German supermarket for that matter). In season, there would be at least 5 varieties of asparagus. A typical American supermarket worker did not eat asparagus in his/her life, how can he advise which is better for what kind of dish?

Moreover, whom are we kidding when we write about ships with bananas? Most produce is not that durable and travels by truck across North America, for thousands of miles. Fuel, spoilage and intermediaries add to the cost, even with underpaid workforce at the farms.

Wal-Mart may be cheap in North America, but not in traditional markets of Europe.

The key to low price at ethnic markets tends to be that they buy the stuff from the wholesaler just about at the due date. The result is riper (better tasting) stuff, but a higher level of spoilage.

If we had a carbon tax, it would be much easier to figure out which modes of production are the most efficient.

Most produce is not that durable, and "buy local" obviously makes the most sense for produce. But most of what supermarkets sell is not fresh produce: olive oil, breakfast cereal, cheese, wine, frozen peas, etc. all travel perfectly well. And there's no particular reason to think that the local stuff is more sustainably produced or low in carbon impact than the stuff shipped from overseas.