Ban The Cows, We'll Get The Trees Later

First they came for your SUVs. Then your light bulbs. What's next? Beef:

As Congress begins to tackle the causes and cures of global warming, the action focuses on gas-guzzling vehicles and coal-fired power plants, not on lowly bovines.

Yet livestock are a major emitter of greenhouse gases that cause climate change. And as meat becomes a growing mainstay of human diet around the world, changing what we eat may prove as hard as changing what we drive.

It's not just the well-known and frequently joked-about flatulence and manure of grass-chewing cattle that's the problem, according to a recent report by the Food and Agriculture Organization of the United Nations (FAO). Land-use changes, especially deforestation to expand pastures and to create arable land for feed crops, is a big part. So is the use of energy to produce fertilizers, to run the slaughterhouses and meat-processing plants, and to pump water.

"Livestock are one of the most significant contributors to today's most serious environmental problems," Henning Steinfeld, senior author of the report, said when the FAO findings were released in November.

Livestock are responsible for 18 percent of greenhouse-gas emissions as measured in carbon dioxide equivalent, reports the FAO. This includes 9 percent of all CO2 emissions, 37 percent of methane, and 65 percent of nitrous oxide. Altogether, that's more than the emissions caused by transportation.

The latter two gases are particularly troubling – even though they represent far smaller concentrations in atmosphere than CO2, which remains the main global warming culprit. But methane has 23 times the global warming potential (GWP) of CO2 and nitrous oxide has 296 times the warming potential of carbon dioxide.

Now, before any of you vegetarians get all high-and-mighty (oh, too late. You all already think your better than us heathen meat-eaters) let's not forget that trees (and presumably other vegetation) are also a leading contributor to global warming:

Do trees pollute? In the early 1980s, then-president Ronald Reagan and some noted scientists attracted attention when they confirmed that trees themselves are a possible source of some types of air pollution. Trees do contribute to the formation of ozone by releasing VOCs such as isoprene, monoterpene, and alpha-pinene.

Under Title 1 of the federal Clean Air Act, states are required to estimate how much trees and plants contribute to VOC production for those areas that exceed ozone standards. The sources of these VOCs, known collectively as "biogenics," include forests, crops, lawn grasses, and other vegetation. The more vegetation an area has, the more these biogenics will contribute to overall VOC levels. For example, biogenics are estimated to account for 22 percent of all VOCs emitted in the woody Houston-Galveston area, but only 12 percent in the arid El Paso area. Nationally, the EPA estimates that biogenics and other natural sources actually produce more emissions of VOCs than do anthropogenic sources. Of course, biogenic sources are natural sources of air pollution, and cutting down trees to reduce pollution would be counterproductive: the air quality benefits of biogenics far outweigh the costs, since plants produce oxygen, filter the air, and prevent erosion. Biogenic sources are not figured into the calculation of how much an area must reduce VOC emissions.

So remember: after they come for our beef, your lettuce is next.