Environment reasons to cut out meat: Part II: Greenhouse gas emissions

The 2006 UN/FAO report "Livestock's Long Shadow" was key in spreading knowledge about the negative environmental impacts of livestock production.

At this time, it was estimated that "livestock are responsible for 18 percent of greenhouse gas emissions."

However, a more recent report published in 2009 by the Worldwatch Institute reexamines the UN/FAO report and argues that "livestock and their byproducts actually account for at least 32.6 billion tons of carbon dioxide per year, or 51 percent of annual worldwide GHG emissions". The report authored by Robert Goodland and Jeff Anhang, entitled "Livestock and Climate Change", concluded that "a 25-percent reduction in livestock products worldwide [...] would yield at minimum a 12.5-percent reduction in global anthropogenic GHGs emissions."