In other words, methane from livestock is a big problem. A new study from the International Institute for Applied Systems Analysis suggests that taking steps to reduce emissions per kilogram of protein is an important part of addressing this issue and preventing catastrophic global warming in this century. 

The study, published last week in the scientific journal AGU Advances, applies a recently revised model from the IPCC to estimate the past two decades’ worth of livestock-related methane emissions and forecast different emissions scenarios through 2050. Lead author Jinfeng Chang and his colleagues found that while the overall global emissions from livestock production increased by more than 50% since 1961, emissions per kilogram of protein in a number of important categories, including beef and dairy, have actually decreased over the past 20 years. 

They attribute this decrease to innovations that allow producers to get more meat or dairy per animal raised. That increased output isn’t the same all over the world, with developed countries that have industrialized livestock production seeing increases in productivity not shared by developing countries. Part of the reason for this might be that animals in developing countries are often multi-use, rather than being raised and slaughtered for food alone.  

The team estimates that those developing countries, which are also where demand for meat is projected to increase the most, can substantially reduce their projected methane output by paying attention to what animals are fed, alongside other measures.

Changing what livestock eat to crops that have a low carbon footprint can make a significant dent in the overall emissions each food animal is responsible for. Additionally, adding substances that aid in digestion—even ones as simple as seaweed—to feed can help to reduce the amount of methane that cows and other ruminants produce. Together, measures such as these are known as “feed efficiency.”  

By 2050, the world’s population is expected to grow to nearly 10 billion people. “We know we will need more food,” says Chang. At the same time, he says, “we don’t want to seem as if we’re promoting industrialized livestock production.” In a number of categories, from livestock welfare to environmental pollution, industrialized livestock production as currently practiced has significant issues, he says.  

Jessica Zionts, a research analyst in the World Resource Institute’s food and climate subject area, agrees that feed is an essential part of reducing livestock-related methane emissions. “If you improve the feed efficiency you can improve pretty much every other category,” she says.  

But it’s important to also not lose sight of the need to reduce consumption of resource-intensive foods like meat and dairy, she says: “The reality is that you have to do both, really aggressively, and you have to do them now.” 

Others, like Matthew Hayek, a New York University environmental scientist, warn that the methane problem could be even bigger than we realize. He recently published a paper cautioning that IPCC estimates of methane emissions—such as those used in Chang’s paper—appear to be significant undercounts. 

“I think that the global problem of unsustainable agricultural development and diets is more urgent than the measurement and modeling studies can necessarily inform,” says Hayek. “This is at its root a socio-environmental problem.”