Is your lunch causing global warming? Cars and factories are major sources of greenhouse gas emissions that are heating up the planet. But what you eat may have even more of an impact.

• Author: Rosenthal, Elisabeth
• Position: ENVIRONMENT

As you go through the cafeteria line and grab a roast beef sandwich and a bag of chips or a salad and a couple of cookies, maybe you're thinking about how much money or how many calories lunch will cost you.

But here's something you're probably not thinking about: Is your lunch a cause of climate change?

When people think about what's behind global warming, the images that tend to spring to mind are factory smokestacks and cars spewing tailpipe exhaust. And cars and power generation, whether for factories or to heat and cool our homes, are indeed major causes. But what we eat--and the energy required to grow, harvest, process, and transport all that food may have an even bigger impact.

"It's an area that's been largely overlooked," says Rajendra Pachauri, head of the United Nations Intergovernmental Panel on Climate Change.

An estimated 25 percent of the greenhouse gas emissions produced by people in industrialized nations can be traced to the food they eat, according to a recent study in Sweden.

Most scientists today think that global warming--the rise in Earth's temperature due to a buildup of heat-trapping greenhouse gases--is having a significant, and possibly disastrous, impact. There is already evidence of glaciers and arctic ice sheets malting, which could eventually cause ocean levels to rise so much that coastal areas around the world would be flooded.

BEEF VS. CARROTS

Since foods vary enormously in the emissions released in their production and transportation, experts say that changing our diets (which would prompt changes in the entire food-production chain) could have as much impact on reducing emissions of climate-changing gases as switching to a hybrid car or getting rid of the clothes dryer.

Meat is perhaps the worst culprit. Producing a pound of beef generates 11 times as much greenhouse gas as producing a pound of chicken, and 100 times as much as producing a pound of carrots (see graph, p. 8).

The United Nations estimates that livestock--the trillions of cows, pigs, and chickens raised for food--generate 18 percent of the emissions that are causing climate change. That's more, the U.N. says, than the emissions from cars, buses, and planes put together.

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Consider the environmental impact of eating a burger. Today, there's a good chance your burger comes from meat produced in an industrial feedlot like the one in Garden City, Kansas, where 37,000 cows are packed into an enormous grid of steel-fenced pens...