(Mother Jones) -- As Josh Harkinson noted this week, cows are the United States' single biggest source of methane—a potent gas that has 105 times the heat-trapping ability of carbon dioxide. That's one major reason why beef's greenhouse gas footprint is far higher than that of most other sources of protein, according to an EWG study. (Though it's consumed at a fraction of the rate of beef or chicken, lamb is by far the most carbon intensive of the major meats, according to EWG, since the animal's smaller body produces meat less efficiently but still produces a lot of methane.)
And EWG's estimate of beef's impact may actually be on the conservative side: A study released this week found the greenhouse gases associated with beef to be even higher.
So what should you eat instead of beef?
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