The permyz follow Joel Fuhrman’s Eat to Live regimen for all the reasons Gigi mentioned (Fuhrman doesn’t even describe the environmental benefits, but Francis Moore Lappe and Anna Lappe’s Hope’s Edge does). This diet seems especially well suited to home-grown food. In short, it just fits with permaculture.

By the way, the original crew of Biosphere 2 raised supposedly low-maintenance animals chosen specifically to eat agricultural by-products and not compete with human food production. But as Jane Poynter describes in The Human Experiment, the animals actually required lots of attention and provided only 150 calories a day  worth of food (less than a tenth of the bionauts’ actual diet). This suggests that ecologically speaking, animal food products should play a very minor role in our diet, and the medical data (Fuhrman) support this.

The starvation figure comes from Hope’s Edge: The Next Diet for a Small Planet (page 19)—an awesome, nearly life-changing book. If it inspires you to go vegan, I’d recommend NOT trying the included recipes, which either involve too much work or way too many onions. Better to start with The Peaceful Palate: Fine Vegetarian Cuisine (a great gift book for the new cook or vegan),  Vegan Planet: 400 Irresistible Recipes with Fantastic Flavors from Home and Around the World (just scant the noodles in all pasta dishes by half), or  Veganomicon: The Ultimate Vegan Cookbook (for the terminally hip).

And yes, we have a cat who does tricks for lettuce. But so will a rabbit.