Eat meat...and save the animals?
There was a famous/infamous article SOMEWHERE about 10 years ago, arguing that vegetarianism causes more animals to die than carnivorism (coz we took all their food!). Sounds ludicrous to me, but this was a detailed, mathematical analysis of plant consumption levels vs. animal body weights.
As a heavy meat-eater but vegetarian wannabe, I found it a fascinating piece. Does anyone recall it, and could point me in the right direction? I want to say The New Republic, but that's almost a blind guess at this point.
I suppose you could argue that habitats have been destroyed to make more agricultural land (to make more human-food), but in my experience it's tract housing that's the main culprit. Either way, we are crowding them out at an alarming rate to make room for more of us. I'm a vegetarian (mostly), but not because I'm not aware that we live in an eat-or-be-eaten world.
Living one level higher on the food chain involves straining the agricultural base far more than the level below. The conversion factors range from 1.1:1 for rabbits (1.1 lbs of feed to acquire 1 lb of rabbit), to an astounding 60:1 for beef creatures. The lowest impact situation is when one keeps chickens and/or swine and feeds them off hosehold scraps and local forage. Of course, this is meat eating as practised by the Chinese, not American style.
You might try F.H. King's book, "Farmers of Forty Centuries", reprinted by Rodale Press to get a better idea of how it goes.