John Tierney suggests that a car trip may be more environmentally sound than walking, or taking a pedicab; after all, human beings have to consume fuel, too. I'm inherently sceptical of these sorts of claims; my impression is that they usually count all of the greenhouse gases emitted in growing and transporting the food, but calculate only the actual carbon emissions from burning the gasoline. Gasoline, however, has to be extracted and transported, too. Obviously, it's more energy dense than food--otherwise, we'd burn apples in our engines. But for all of the moralizing about Guatamalan raspberries we don't ship all or even most of the food we eat from across an ocean. Also, they seem to be very dependent on how many passengers you carry--full cars with high mileage are relatively energy efficient, but they're also relatively rare. Most of the cars I see on the road have a single occupant.
That said, what his numbers do point to is that the net benefit is probably much closer to zero than most of us would suspect.
Yeah, people will eat more to counter the calories they burn walking. Bring on the Hummer!
atrulyinconvenienttruth.org
I thought this might be relevant, it's a post from the NYT site from the author of the walking vs. driving study, I caps-locked the money quote:
"I wrote the piece on walking versus driving that this column comments on. I was extremely naive not to realise that the analysis would be perceived as an encouragement to drivers. I didn't intend it to be read that way. My purpose was to draw attention to the carbon intensity of modern food production, particularly of meat. . . . In the UK, the CO2 cost actually of making gasoline adds about 15% to the total CO2 impact. Similarly, a European car will typically create about 3 tonnes of CO2 in its manufacture. These numbers are not enough to remotely affect the conclusion that car travel is less carbon intensive than walking, IF THE WALKER REPLACES LOST ENERGY WITH ANIMAL PRODUCTS. A home grown potato would produce the reverse conclusion if cooked efficiently. A raw carrot would be even better.” - Chris Goodall
Wikipedia has an interesting article on this subject. The article claims walking produces an equivalent MPG of 235. Most efficient is an electric bicyle, followed by a manual bicycle.
http://en.wikipedia.org/wiki/Fuel_efficiency_in_transportation
The analysis also fails to include the energy saving effect of walking everywhere - you'll lose a few pounds, so will burn less energy carrying around and maintaining your blubber.
Lets grant that Tierney's dubious analysis is right. Nonetheless, I suspect that people who primarily walks to get around consume fewer calories than people who primarily drive to get around. But if bullshit rationalizations are what people need to get by, then Bob's your uncle.
Here's a good way to evaluate all of these green alternatives to fossil fuel consumption - look at the price. Many of the embedded "greener" ideas are more expensive for a reason - at the end of the day they consume more energy in one way or another.
I know the guy just wanted to make a point about animal products, but a burger-fueled pedestrian has an advantage over a car: they don't want to go very far. If our cities were designed for walking as primary transportation, the far lower number of miles traveled would probably make up for the increased CO2 per mile.
Fortunately, I've come up with a solution: lazy cars. They may go from 0 to 60 in a hurry, but they'll have to rest afterwards. Some models will start whining after just a few miles.
I'm inherently skeptical of spelling it "sceptical"...just kidding; it's just a pet peeve of mine. So is people in America saying "sacked" instead of "fired" when someone involuntarily loses their job. It just sounds so pretentious.
I have a simpler solution: don't agonize over it. As long as you're not dumping mercury wastes into drinking supplies, you're not doing much - or probably any - environmental damage beyond that entailed by your existence.
Whether you obviate that damage is, of course, a most personal decision, and depends on your views on suicide.
Many of the embedded "greener" ideas are more expensive for a reason - at the end of the day they consume more energy in one way or another.
Cost of driving a car: $20,000 plus $3000/year in gas plus repairs plus insurance
Cost of walking: $0
I imagine if the average American made his 12-mile daily commute on foot, he probably would burn some extra calories. Somehow it seems more likely that people who walk would instead have shorter commutes.