How long is your shadow? The answer, of course, depends, and differs whether you are standing on the equator at high noon, or on a mountaintop at sunset. Likewise the “shadow” or carbon footprint of livestock production depends on where and how you measure it.

Frank Mitloehner, PhD., an animal scientist and air-quality specialist at the University of California, Davis, Agricultural Air Quality Center, helped participants in the annual NIAA conference gain perspective on environmental impacts of livestock production. Perspective on the issue has been a rare commodity since 2006, when the U.N.’s Food and Agricultural Organization released its report titled “Livestock’s Long Shadow,” which claimed animal agriculture generates 18 percent of global greenhouse gas emissions, exceeding that of the transportation sector.

Mitloehner and other scientists since have demonstrated the fallacy of those conclusions, but the figures have become embedded in public consciousness and continue to appear in the popular press.

First, Mitloehner addresses differences in production practices around the world, and how they influence livestock’s carbon footprint. Land-use change, he says, is a key component in a comprehensive analysis. In some parts of the world, particularly South America, Africa and Southeast Asia, expansion in livestock production has come at the expense of considerable deforestation. As a result, greenhouse-gas emissions increase while at the same time, the carbon-storing properties of forests are lost. Also, in many of these developing nations, livestock production is extensive, while their transportation infrastructure is under-developed. So a lifecycle analysis will show that GHG emissions associated with livestock (including land-use change) are relatively high, and could exceed those of transportation.

The picture is far different in developed countries such as the United States. Here we see annual net gains in forested land, rather than deforestation, and more intensive, rather than extensive livestock production. Efficiencies in production systems allow more meat or milk production per animal and per land unit, meaning less GHG emissions. Grain feeding for cattle, for example, reduces methane emissions compared with those from grass finishing, although much of the public believes otherwise. At the same time, we have a well-developed transportation sector that generates enormous GHG emissions. In the United States, Mitloehner says, total GHG emissions for a unit of meat production are about one-tenth of those in Brazil. Emissions from generating electrical power account for about 31 percent of the U.S. total, according to EPA estimates, while transportation accounts for 26 percent and livestock about 3 percent.

Mitloehner also provides an example from dairy production, saying that in Southern California, dairies average about 20,000 pounds of milk per cow annually. Just across the border in northern Mexico, the average is 4,000 pounds. So it takes five times as many cows to produce the same amount of milk, with a proportional increase in GHG emissions per unit of production.

The FAO report, he says, lumps all regions together in arriving at the 18 percent figure, which has misled the media and consumers regarding animal agriculture in the United States. But it gets worse. In a report titled “Clearing the air: Livestock’s contribution to climate change,” Mitloehner and his research colleagues point out a significant error in the FAO report. The report relies on a type of study called “lifecycle analysis,” or LCA, to estimate GHG emissions from a system. But all LCA’s are not created equal. In FAO’s research, they used the most extensive type of LCA to estimate emissions from livestock, including all inputs, such as emissions produced from tilling crop fields for growing grain, drying and transporting grain, and every other process contributing to meat or milk ultimately delivered to consumers.

In their estimates of transportation emissions, however, the authors used the simplest form of LCA, looking only at tailpipe emissions. Contributors such as auto manufacturing, oil drilling and  fuel transport were conveniently disregarded. This apples-to-oranges comparison resulted in the distorted conclusion that livestock produces more GHG than transportation. The authors of “Livestock’s Long Shadow” have since admitted the error.

One thing they got right, Mitloehner notes, is a conclusion that intensification in livestock production reduces the carbon footprint compared with more extensive, less efficient production systems. That conclusion, unfortunately, was buried deep in the report and not included in the executive summary widely reported in the media.

For more, read “Clearing the air: Livestock’s contribution to climate change.”