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Pollution on the hoof

Livestock emissions are a leading source of greenhouse gases. One solution may be to eat less meat.

October 15, 2007

It's a silent but deadly source of greenhouse gases that contributes more to global warming than the entire world transportation sector, yet politicians almost never discuss it, and environmental lobbyists and other green activist groups seem unaware of its existence.

That may be because it's tough to take cow flatulence seriously. But livestock emissions are no joke.

Most of the national debate about global warming centers on carbon dioxide, the world's most abundant greenhouse gas, and its major sources -- fossil fuels. Seldom mentioned is that cows and other ruminants, such as sheep and goats, are walking gas factories that take in fodder and put out methane and nitrous oxide, two greenhouse gases that are far more efficient at trapping heat than carbon dioxide. Methane, with 21 times the warming potential of CO2, comes from both ends of a cow, but mostly the front. Frat boys have nothing on bovines, as it's estimated that a single cow can belch out anywhere from 25 to 130 gallons of methane a day.

It isn't just the gas they pass that makes livestock troublesome. A report from the United Nations Food and Agriculture Organization identified livestock as one of the two or three top contributors to the world's most serious environmental problems, including water pollution and species loss. In terms of climate change, livestock are a threat not only because of the gases coming from their stomachs and manure but because of deforestation, as land is cleared to make way for pastures, and the amount of energy needed to produce the crops that feed the animals.

All told, livestock are responsible for 18% of greenhouse-gas emissions worldwide, according to the U.N. -- more than all the planes, trains and automobiles on the planet. And it's going to get a lot worse. As living standards rise in the developing world, so does its fondness for meat and dairy. Annual per-capita meat consumption in developing countries doubled from 31 pounds in 1980 to 62 pounds in 2002, according to the Food and Agriculture Organization, which expects global meat production to more than double by 2050. That means the environmental damage of ranching would have to be cut in half just to keep emissions at their current, dangerous level.

It isn't enough to improve mileage standards or crack down on diesel truck emissions, as politicians at both the state and national levels are working to do. Eventually, the United States and other countries are going to have to clean up their agricultural practices, while consumers can do their part by cutting back on red meat.

Manure, methane and McGovern

In a Web forum for presidential candidates in September, TV talk-show host Bill Maher asked former Sen. John Edwards a snarky question: Because Edwards had suggested that people trade in their SUVs to benefit the environment, and cattle generate more greenhouse gases than SUVs, "You want to take a shot at meat?" Maher asked.

Edwards wisely dodged the question. It is extremely hazardous for politicians to take on the U.S. beef industry, a lesson learned by Sen. George McGovern in the late 1970s when his Select Committee on Nutrition dared to recommend that Americans cut down on red meat and fatty dairy products for health reasons. After a ferocious lobbying blitz from meat and dairy interests, the committee rewrote its guidelines to suggest diners simply choose lean meats that "will reduce saturated fat intake." McGovern was voted out of office in 1980, in part because of opposition from cattlemen in his home state of South Dakota.

Beyond the dangers of taking on the beef bloc, legislating food choices is an unpopular and nearly impossible task, so it's unlikely any candidate will endorse a national vegetarian movement to fight global warming any time soon. There are other approaches, though.

Cows and other ruminants have four stomachs, the first of which, called the rumen, is where the trouble lies; bacteria in the rumen produce methane. Scientists -- mostly in Australia, New Zealand and Britain, where the problem is taken a lot more seriously than it is here -- are working on a variety of technical solutions, including a kind of bovine Alka-Seltzer. Scientists are also trying to develop new varieties of feed grasses that are more energy efficient and thus generate less methane, and they are experimenting with targeted breeding to produce a less-gassy strain of cattle.

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