A reader makes an important point:
Your reader said: “And please, if we all became vegetarians/vegans … we would probably run out of arable land to feed everyone.” This could not be more wrong. Converting plants into meat is a very inefficient way to transmit the plants’ calories and nutrients to people. If we simply ate plants instead of meat, we’d need a lot LESS agricultural land. And the USA has one of the lowest population densities of any developed country, so we have plenty of arable land to spare. This is a complete red herring.
Another backs that up with a NYT piece:
[A]bout two to five times more grain is required to produce the same amount of calories through livestock as through direct grain consumption, according to Rosamond Naylor, an associate professor of economics at Stanford University. It is as much as 10 times more in the case of grain-fed beef in the United States.
The reader adds, “I gave up eating meat years ago not because I am morally opposed to the idea of killing animals, but because it was the one action I could take that would have the greatest impact on my carbon footprint.”