Advocates of reduced meat consumption—not to mention vegetarian and vegan interests—were elated, quickly elevating this finding to the level of dogma. For a while, it was not uncommon to hear people saying that a meat-eating Prius driver has a bigger carbon footprint than a vegan Hummer driver.
But Dr. Frank Mitloehner, an animal scientist at UC-Davis, was skeptical—especially when it came to the transportation comparison. With substantial funding from the Beef Checkoff Program, Mitloeher researched and wrote a peer-reviewed article called "Clearing the Air: Livestock's Contribution to Climate Change." In a talk delivered last month to the American Chemical Society, he drew upon this article to challenge the claim that livestock produce more greenhouse gas than transportation.
The authors of the FAO report, he revealed, took their transportation figure from the International Panel on Climate Change (IPCC). The problem with doing this was that the FAO had applied a far more comprehensive life-cycle analysis to animals than the IPCC had done to transportation, resulting in an overstatement of the effect of animal agriculture on global warming. The comparison of livestock and transportation, he argued, was essentially a comparison between apples and oranges.
A life-cycle analysis (LCA) is a stage-by-stage assessment of where energy is consumed (and greenhouse gases produced) in the production of a particular item. While invaluable in terms of improving energy efficiency, LCAs can vary wildly when it comes to comprehensiveness. When applied to livestock, a competent life-cycle analysis should at least examine the energy required to grow the grain to feed the cattle, to slaughter the animals and process the flesh into edible cuts, to refrigerate and transport the meat, and to dispose of the carcass. It should also measure bovine methane output and the carbon sequestration lost because of deforestation. The FAO was diligent in doing all this.
However, the IPCC, when it did its transportation lifecycle assessment, applied a much narrower focus (not because the IPCC is incompetent, but because the data is simply less available), thereby producing a smaller emissions figure. Responding to Mitloehner's charge, Pierre Gerber, a co-author of the FAO report, responded, "I must say that he has a point. We factored in everything for meat emissions, and we didn't do the same for transport, we just used the figure from the IPCC." This is a rare thing in the scientific community, by the way—an admission of error.
On the grand scale of scientific errors, though, this one was relatively minor. What matters most is that the 18 percent figure—and the corresponding implication that reduced meat consumption would lower global warming—remained essentially untouched by Mitloehner's report. Mitloehner's only complaint about the cattle emissions numbers was that they obscured regional variation in livestock emissions. A South American country actively clearing rainforests to raise cattle will make a much greater contribution to the 18 percent figure than a country such as the United States, which is not clearing land for livestock. It's a good point. But Mitloehner's debunking of the transportation comparison changes nothing about the overall impact of livestock on the environment. "We stand entirely behind the 18 percent figure," Gerber told the Columbia Journalism Review.