Intensively reared grain fed beef in the US – bad for the planet.
British hill farmed lamb on marginal land? Not so bad.
I can eat lamb raised on grass a few miles from my house. I can’t eat lentils grown in the same country.
Unfortunately the evidence says otherwise. You could fly lentils or soybeans many times around the world before their carbon footprint even comes close to the most efficiently produced meat.
http://www.sciencedirect.com/science/article/pii/S0306919212000942
And it’s really not as simple as intensive & distant = bad, natural & local = good. The vast majority of meat’s carbon footprint is produced on the farm, transport is negligible in comparison. And animals that live for longer, eat less digestible foods, and move around more (those on British farms for example), will produce more carbon dioxide and methane per kg of meat than those that grow quicker, move less and are fed more calorific foodstuffs.
Obviously intensive animal farming has a lot of other problems too – pollution from pesticides and fertilisers, runoff of animal waste, over-reliance on antibiotics etc.