Sorry to ruin your appetite, but it's time to talk about cow farts.

In 2011, methane from livestock accounted for 39 percent of all the greenhouse gas emissions from agriculture, according to a report that United Nation's Food and Agriculture Organization released Friday. That's more than synthetic fertilizer or deforestation. Methane from livestock rose 11 percent between 2001 and 2011. The bulk of the emissions — 55 percent — came from beef cattle. Dairy cows, buffalo, sheep and goats accounted for the rest. Those emissions, combined with emissions from all the other sectors of food production, aren't likely to go down anytime soon. Greenhouse gas emissions from agriculture, forestry and fishing have doubled over the past 50 years, according to the report. Emissions could go up by 30 percent by 2050.All this talk about cow farts might make you want to give up meat. So should we all become vegetarians? Asking everyone to reduce their meat consumption isn't a very practical strategy, says Francesco Tubiello, a natural resources officer for the FAO. The demand for meat is rising most quickly in developing countries. And since the diets of many in the developing world are short on protein and calories, the poorest of them could really benefit from more meat production. Plus, "for many developing countries, agriculture is their main economic sector," Tubiello tells The Salt.