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.
Of course, the flaw in the reasoning for the alleged conclusion -- that walking contributes to global warming -- is the assumption that we wouldn't be taking in those calories if we weren't walking. Even thinking about our society a moment shows how obviously absurd this is. This is connected with further absurd assumption: that someone, by no longer walking, would reduce carbon emissions. Food production is supply-side in the sense that you first create the food and then try to get rid of it for profit; even refusing to buy the food wouldn't immediately reduce carbon emissions because that's all in production and distribution, which occur before the buying. The only thing one could hope to do in that regard is to make the carbon-intensive food production unsustainable as a business. The difference between walking and driving is simply that in driving you are adding the driving-related carbon emissions to the food-related carbon emissions; you aren't substituting them.
The reasoning also overlooks compensating factors. The carbon emissions on which the calculation were based was those created by beef and milk; but no one, not even those of us born in West Texas, get all our calories from beef and milk. Some we get from the local farms; some from the garden; some from the sea; etc. Even West Texans get some of their calories from Dr Pepper. Each different source would have a different carbon profile.
The only reasonable conclusion from the principles and data used is not to walk less (and certainly not to drive more) but to buy food more selectively, and lower the demand for beef and milk in favor of alternatives, if this would make a significant difference (alone or in combination with other projects).