If we really want to cut down on global greenhouse emissions, we're going to have to do something about cow farts*.
That's the conclusion of a study published today in the journal Climatic Change. If we have any shot of reaching the Intergovernmental Panel on Climate Change's global-warming mitigation goals, the world is going to have to start eating a lot less meat.
Thirty-seven percent of all human-caused methane emissions come from the worldwide agricultural industry. Compared with CO2, methane is 21 times more effective at trapping heat in the earth's atmosphere, according to the United Nations. While transportation and electricity account for more than half of emissions in the United States, the EPA reports that agriculture comprises 8 percent of all greenhouse-gas emissions. And while relatively small, that's a significant contribution that can't be ignored—especially considering how progress in halting emissions from transportation has so far been minimal.
"In order to have any chance to reach a 2 degree target, fossil-fuel use has to be reduced drastically," Fredrik Hedenus, the study's lead author, wrote in an email. "However, what we show is that may not be sufficient, as the agricultural emissions ... may be too high. Thus we have to take action in both sectors." Transportation and energy are the biggest sources of greenhouse gases, but researchers say a global shift in people's diets is also necessary to contain climate change."We therefore conclude that dietary changes are crucial for meeting the 2 degree C target with high probability."
So, how much less meat do we have to eat?
"It all depends how much we can and want to do in the energy sector," Hedenus explains. "If we do a lot there it may be sufficient with a 25 percent lower meat and dairy consumption than predicted in 2070. If we do less, somewhere around 75 percent less may be reasonable."
If 25 percent to 75 percent less meat consumption worldwide sounds like an absurd long shot, it is. Global meat demand only continues to rise, as fueled by China and the developing world. Meat consumption in the United States has actually declined in recent years, explains Emily Adams, a researcher with the Earth Policy Institute. "Meat consumption peaked in the United States as a nation in 2007 and since then it has fallen 4 percent," Adams says. "That's not a 75 percent reduction like they are talking about, but that's coming without government fiat or absolutely insane food prices."
But while meat consumption in the United States has fallen, that's a small drop compared with the rising demand in China.
Also Monay, the IPCC released its latest progress report on climate change, finding that "global climate-change risks are high to very high with global mean temperature increase of 4 degrees C or more above preindustrial levels ... and include severe and widespread impacts on unique and threatened systems, substantial species extinction, large risks to global and regional food security, and the combination of high temperature and humidity compromising normal human activities, including growing food or working outdoors in some areas for parts of the year."
The reports are getting scarier, and papers like Hedenus's underscore how, if we're really going to attenuate the rate of climatic change, we're going to need severe changes in our culture. Electric cars may come to replace conventional ones, but they'll still be cars. Getting people to change their diets will require a global change in thinking and behavior.
The study's authors aren't exactly optimistic about this hard fact.
"Substantial deviations from current dietary preferences are unlikely and would probably occur only as a result of policy interventions," they write. "However, policy-driven dietary changes are contentious and would almost certainly emerge only after productivity improvement and technical measures largely have been exhausted."
*Clarification: Cow burps and manure actually contribute more to greenhouse gas emissions than the flatulence does.