A fast-food quarter-pounder costs $3, and 1,300 gallons of water. That's how much it takes, per burger, to hydrate the cow, grow its food and process its carcass, according to the Web sites of the National Park Service, the U.S. Geological Survey and a bottled-water trade group. By contrast, a loaf of bread uses up 150 gallons, and milk requires just 65.

The message dovetails with the goals of environmental meal-managing: Eat meat, and you're using up a precious natural resource.

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