Why driving a couple of miles might be more environmental than walking

here (via Steve Levitt):

If you walk 1.5 miles, Mr. Goodall calculates, and replace those calories by drinking about a cup of milk, the greenhouse emissions connected with that milk (like methane from the dairy farm and carbon dioxide from the delivery truck) are just about equal to the emissions from a typical car making the same trip. And if there were two of you making the trip, then the car would definitely be the more planet-friendly way to go.

Also, here's why plastic is more environmental than paper:

The making of paper can waste many thousands of gallons of water, as can the recycling of paper. The human and mechanical efforts and costs are very high, not forgetting the physical cost to loggers and those who work around the numerous chemicals. Plastic is, by comparison, efficient and low energy to produce, and, easily and efficiently recycled. Plastic reduces, recycles marvelously, and in that, is reused. After contrasting the efforts behind the making of paper and plastic, it is our unbiased opinion that plastic is indeed more beneficial to the environment, in that it is less harmful. The next time you are asked the dreaded question, "Paper or plastic?", you can answer knowing that you are making the informed choice.