Thanks to Tyler Cowen's blog, I've recently read two intriguing articles about carbon footprints. The "Localvore's Dilemma" from the Boston Globe challenges the common notion that buying local produce is more energy-efficient and greenhouse-friendly than buying food that has been shipped long distances.
Food activists in the US and especially in Western Europe have pushed to put the term on menus and grocery-store labels.
"[T]he typical item of food on an American's plate travels some fifteen hundred miles to get there," Michael Pollan writes in "The Omnivore's Dilemma," "and is frequently better traveled and more worldly than its eater."
But a gathering body of evidence suggests that local food can sometimes consume more energy -- and produce more greenhouse gases -- than food imported from great distances. Moving food by train or ship is quite efficient, pound for pound, and transportation can often be a relatively small part of the total energy "footprint" of food compared with growing, packaging, or, for that matter, cooking it. A head of lettuce grown in Vermont may have less of an energy impact than one shipped up from Chile. But grow that Vermont lettuce late in the season in a heated greenhouse and its energy impact leapfrogs the imported option. So while local food may have its benefits, helping with climate change is not always one of them.
The other article--Walking to the shops 'damages planet more than going by car'--comes from the London Times. I'm suspicious of these claims, but here goes:
Food production is now so energy-intensive that more carbon is emitted providing a person with enough calories to walk to the shops than a car would emit over the same distance. The climate could benefit if people avoided exercise, ate less and became couch potatoes. Provided, of course, they remembered to switch off the TV rather than leaving it on standby.
The sums were done by Chris Goodall, campaigning author of How to Live a Low-Carbon Life, based on the greenhouse gases created by intensive beef production. "Driving a typical UK car for 3 miles [4.8km] adds about 0.9 kg [2lb] of CO2 to the atmosphere," he said, a calculation based on the Government's official fuel emission figures. "If you walked instead, it would use about 180 calories. You'd need about 100g of beef to replace those calories, resulting in 3.6kg of emissions, or four times as much as driving.
"The troubling fact is that taking a lot of exercise and then eating a bit more food is not good for the global atmosphere. Eating less and driving to save energy would be better."
The article reads like a parody. Still, I have no idea how to evaluate the competing claims in either article. As Tess Vigeland pointed out to me, it's much like health news. One study will tout drinking red wine because it's healthy for you. Several months later another study will trumpet the opposite result. (Still, red wine is good for the soul if not the body.)
It's at this moment that I retreat to economic fundamentalism. I can't evaluate the competing claims. And I don't believe that individuals can really make much of a difference on their own. We're facing a common risk and a common good. That's why I favor simply imposing a steep carbon tax on everyone, and then let the collective wisdom of the market sort what is energy-efficient and carbon-friendly and what isn't.
The best global warming insurance policy is a carbon tax. Everything else is secondary commentary.
Economist Greg Mankiw at Harvard has insights on carbon taxes and gasoline taxes at his blog.