The Times (U.K.) reports:
Walking does more than driving to cause global warming, a leading environmentalist has calculated.
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."
I have no idea whether Goodall is right or wrong. But there have been enough stories like this — about recycling, energy production generally, carbon emission, and more — that it seems clear that there are all sorts of hidden tradeoffs that both casual intuitive analysis (nuclear bad, driving bad, recycling good) and even published reports often miss. This in turn makes me skeptical about demands that we, either individually or through government action, change our lives to improve the environment.
Some such demands may indeed be quite sound, and there certainly are real environmental hazards. Poisoning our neighbors, and ourselves, is bad, if there are alternatives that poison less at acceptable cost. (Recall that some degree of environmental harm is inevitable to get important benefits; to give a simple analogy from the context of biological poisoning, we put our fellow citizens at risk of contagious disease whenever we walk near them, even when we seem asymptomatic, but we think the benefits of such interaction exceed the cost.) But I'm cautious about jumping on bandwagons in this field, and the more strident the bandwagoneers, the more I wonder whether they've really examined the tradeoffs dispassionately, carefully, and thoroughly.
Thanks to Victor Steinbok for the pointer.