I don't think EVERYONE should be vegan, because not everyone can be vegan. A large portion of third world countries can't rely solely on plants for food because of their environment. BUT, I do believe that the first world countries can go and should go vegan. As for what happens after we do (which we probably won't), I'm sure we can figure out a way to lessen the blow on the environment. It's still better than eating our animal buddies IMO.