It is not only feeding. It is the use of each and everything this planet provides.
Example is fossile energy. And I am not talking abour greenhouse gas now but about availability.
If you burn wood, you cannot burn more wood than you grow trees or you go into deforestation with all the negative effects this has.
Fossile energy is pretty much wood (or plant matter in general) that was grown long ago and when it is used up, we cannot easily renew it.
Same with sand that is used for construction (concrete). Desert sand is too fine and cannot be used for that and already today it is forseable, that sand of a quality that can be used for construction will actually be in short supply in a not too distant future (definitely within our lifetime).
And that goes for metals, minerals, everything.