Even their statistics about “(X) pounds of grain to produce a pound of meant...” are, at best, half truths. They omit the fact that meat is a much more concentrated source of protein.
Estrogen poisoning, from eating all that tofu, is the most likely explanation for their madness.
Sustainable “development” includes keeping open wild prairie and letting a few cattle and buffalo graze on it. If we don’t benefit from it, we’ll likely destroy it. Push the people out, and they’ll come back to plant vegan crops.