I'm not sure if this has been linked, here, though I know the question has been raised. This is an amazing 20 minute TED talk about how to stop the increasing desertification of much of our land mass, as well as how to sustainably feed large numbers of people. (And wouldn't you know, it also supports the primal/paleo lifestyle ). I thought I would just watch a few minutes of it, but I wound up being fascinated and watching the whole thing. Very interesting!

Sustainability Sushmainability: Hey Vegans, How Does a Dozen Grassfed Cattle Per Person on Earth Sound? | Free The Animal