Greenhouse gas emissions from livestock production have increased by more than 50 percent over the past 50 years and are set to zoom higher as the developing world consumes more meat, finds a new study published in the journal Proceedings of the National Academy of Sciences (PNAS).
The research is based on analysis of the impacts of livestock production per calorie consumed, including water and fertilizer use, land area requirements, and other factors. It went beyond carbon dioxide, evaluating greenhouse gas emissions from methane and nitrous oxide.
Like other studies, the paper found that beef has overwhelmingly the biggest climate impact among dairy, poultry, pork, and eggs.
 Percentage of the overall national environmental burdens exerted by the individual animal categories. Beef requires ≈88% of all US land allocated to producing animal-based calories, partitioned (from the bottom up) among pasture (≈79%), processed roughage (≈7%), and concentrated feed (≈2%). Image and caption courtesy of the authors. |
“Impacts of dairy, poultry, pork, and eggs were mutually comparable within a factor of two. Beef, however, required 28 times more land, 11 times more irrigation water, five times more greenhouse gas emissions, and six times more reactive nitrogen fertilizer than the respective average burdens of the other four livestock categories,” stated a release from PNAS.
The study also noted a significant divergence in trends on livestock-related emissions between industrialized countries, where emissions peaked in the 1970s, and the developing world, where emissions could double by 2050.
“The developing world is getting better at reducing greenhouse emissions caused by each animal, but this improvement is not keeping up with the increasing demand for meat,” said study co-author Dario Caro of the University of Siena in Italy. “As a result, greenhouse gas emissions from livestock keep going up and up in much of the developing world.”
The study concludes that shifting protein consumption away from beef would help curb rising temperatures.
“Potato, wheat, and rice production, on average, required two to six times less resources per calorie consumed than non-beef livestock,” said PNAS. “Understanding the impacts of different classes of livestock may empower consumers and policy-makers to mitigate environmental burdens through diet choice and agricultural policy.”
“That tasty hamburger is the real culprit,” added the Carnegie Institution’s Ken Caldeira, who worked with Caro, but wasn’t an author of the paper. “It might be better for the environment if we all became vegetarians, but a lot of improvement could come from eating pork or chicken instead of beef.”
CITATION: Gidon Eshel, Alon Shepon, Tamar Makov, and Ron Milo. Land, irrigation water, greenhouse gas, and reactive nitrogen burdens of meat, eggs, and dairy production in the United States. PNAS Online Early Edition the week of July 21-July 25, 2014