I think the person who takes a job in order to live - that is to say, for the money - has turned himself into a slave.
If you look at it ecologically, deforestation is high on the list of things which bring devastation. You cut down trees to build homes, for fuel, and you end up with no trees left, and you have to move on. If you take the earth as a whole, eventually there's nowhere to move on to.

