So the development team said that they are creating an ecosystem that is self sufficient and that the only time the equilibrium is interrupted will be when players enter and cause that imbalance. I believe that we can assume that the NPCs will be used as a way of helping maintain that equilibrium. IE, they will ensure that the land is taken care of until it is discovered by players. I also believe that NPCs will be consumers as well as producers. You have to have + and - in order to maintain a balance.
I believe that they also said in the same thread that if we cause something then we will have to fix it. I am sure though that the development team will put a safety net in where, over a much longer time, the environment will return to equilibrium; however, the odds are low because of player involvement.
You'll have to wait on the hunger information. I do know that depending on what you do will depend on your diet and what your body type will be. IE if your are rarely in a city, you will probably be leaner because you eat more proteins because of that being your primary food source. I would expect that the more active you are, the more that you will have to eat.