This article in the WSJ highlights a serious contributor to greenhouse-gas emissions:
Plenty of people, including farmers, think the problem of sheep burps is so much hot air. But governments are coming under pressure to put a cork in it, and many farmers fear that new livestock regulations could follow. They worry that environmentalists will someday persuade the U.S. Environmental Protection Agency to seek to tax bovine belches. Some activists are urging consumers to stop buying meat and thus slow climate change.
Jonathan Milder, Research Librarian