The capitalist economic model is based on growth. Capitalism is working if there is growth. If industry produces more, if there are more things bought if more resources are exploited. But it is this very base that makes it destructive. Capitalism seeks infinite growth. If it does not grow, it is unsucsessfull. Yet, there are a finite number of resources present on the earth. One cannot maintain growth forever. Eventually a balance must be reached between population and avalable resources. Without such a balance humanity will become extinct. But such a balance cannot exist along with an economis system that is only made to grow.
The proleterians have nothing to lose but their chains. They have the world to gain. Working Men of the World, Unite! ~Karl Marx