Above all else, the study underscores that while meat production will need to change in the future, so will meat consumption. It’s difficult to get a full and proper accounting of the total environmental impact of livestock production. A 2006 report from the Food and Agriculture Organization estimated that livestock were responsible for about 18% of human-caused greenhouse gases — a figure that has been criticized by the meat industry as too high and by some environmentalists as far too low . But what’s clear is that American levels of meat consumption can’t be sustainably adopted by the rest of the world, even if livestock management becomes more efficient globally. “Demand management has to be part of the solution as well,” says Herrero. For the environment — and for our hearts and waistlines too.