Earth Report

When it comes to our diets, we put a lot of emphasis on calories and cholesterol levels. We're concerned about how diet affects our personal health.

But should we also be considering how what we eat affects the planet?

There's plenty of evidence demonstrating that production of certain foods contributes substantially to the amount of gases believed to be causing global warming.

The U.N. Food and Agriculture Organization in 2006 reported that meat production accounts for about one-fifth of the world's greenhouse gas production. That's more than the greenhouse gases produced by all of the world's cars, trucks, planes, trains and boats.

Meat production and distribution promote climate change in other ways, according to the report:

They lead to deforestation. Vast areas of Earth's land mass are used for cattle grazing. Fewer trees mean less carbon dioxide can be absorbed from the atmosphere, and more carbon dioxide is released when trees are burned to clear grazing land.

They promote noxious emissions. Animals raised for food produce manure that sends nitrous oxide into the atmosphere, a gas with nearly 300 times the warming power of carbon dioxide. Then there's the other kind of gas. When cows pass gas - and they pass a lot of it - the methane has a more powerful warming effect than carbon dioxide.

They make intensive use of resources. A large share of the grain and soybeans grown around the world is fed to animals rather than being eaten by people. Only a fraction of those food calories are returned in the form of meat. Fossil fuels and huge quantities of water are needed for meat production and distribution. Industrial feedlots drain water supplies and pollute the air, water and soil.

When you consider that diets heavy in animal products promote obesity, coronary artery disease, cancer and other chronic diseases, you have to wonder why meat production is on the rise worldwide.

Last week, Lord Stern, an economist at the London School of Economics and former chief economist at the World Bank, told the Times of London that as people become aware of the carbon content of their food, meat-eating will become less acceptable.

Although not a vegetarian himself, he advocated that people switch to more meatless meals to help preserve the environment.