This planet contains food for between 12-15 billions people, but because humans are killing and feeding 57 billion enslaved land-fed animals, people are dieing of starvation

Peter,
We all agree that “unnecessary” animal suffering and death are morally wrong. If that means anything at all, it must mean that we cannot justify animal suffering and death by reasons of pleasure or convenience. But what is our best justification for imposing suffering and death on the 56 billion animals (excluding fish) we eat annually?
Pleasure. Convenience.
So the only justification we have is that which we agree cannot suffice. This is moral schizophrenia.
If you are not a vegan, you are participating directly in animal exploitation. Being a vegan is easy, better for your health, and the most powerful way that you, as an individual, can say “no” to animal exploitation.
[Quote: http://www.abolitionistapproach.com/ ]

The earth contains enough food for 12 - 15 billion people [if we wouldn't feed more than 57 billion land-animals with the misfortune to being someone else's food/boots :'(               ]
We can manage to feed everyone and when people have wakening up and made a conscious choice not to hurt, kill and enslave other beings - just because they happen to be of another species - then we can also educate people to not have more children then this planet can feed.
In this way the food will for all future suffice to all being and to all individuals.
I really recommend this lecture: http://www.youtube.com/watch?v=SvZpF1R6GUo