I don't know if this answers your question, but do read The Vegetarian Myth when you get a chance. It is one of the most profound and wonderful books I've ever read about the subject of sustainability/ethics for vegetarianism vs. omivoreism. Lierre Keith, while rather radical, makes a beautiful argument as to why meat (in moderation and humanely raised) is preferable to a veg-only diet. This is one of the top five books that's changed the way I see the world. Cheers!