Eco-fascism. An ugly word, that.However, forced population control (like they enforce it in China, for instance) is a beginning eco-fascist trait, where totalitarian rules are enforced in the name of pure, simple survival.
The reason there is poverty, unemployment, starvation and lack of space shouldn't be sought in the population size, but in society. The capitalist world has enough money to abolish poverty altogether (ruling out if we abolished currency as a system and used a system of shared resources, in which case the concept of poverty no longer makes sense). One of the principal reasons for unemployment is that automatization removes humans from the labor process (because it is cheaper to make automatised production - after all, robotic manufacturing plants do not demand wages).
Starvation is another brilliant example of a problem we can solve, but won't. In the EU alone, we burn off over 60% of the meat production and destroy over 80% of the fish production to keep prices up - in a world that starves. This is one of the unbalances inherent in capitalism, simply because profit is the bearing ideal - there's nothing in it for us to send that production to the starving people of the Earth. Another problem that poses a more sensible reason for us not to is the fact that sending a Third World nation foreign-produced food contributes to destroying their own production system - but then, I for one should say that it makes more sense to help a starving people than to keep prices up and that people down.
Living space can pose a problem, but it still doesn't. The former Soviet Union has an enormous land area - but a very small population density except in the larger cities.
However, the issue here is not as much overpopulation itself than it is the system that has given us this overpopulation. Integral to the capitalist philosophy is the thesis that growth is good. Economic growth, growth of population and the like are viewed as signs of a society's success. You made that assumption yourself in an earlier post where you asked why people under socialism wouldn't just procreate like mad, considering they would have the economic possibility to do that. However, in socialism growth is not to be viewed as an absolute good, for it clearly isn't. It is obvious that every growth bears an impact on the World in one way or another, growth in wealth often has a cost in the environment, growth in population certainly has, and growth in technology often bears with it a cost in humanity (interesting as it may be, the term of a person 'not having a life' didn't exist before information technology started getting out to the public).
What must be done is not to stop the population growth in itself. We must instead stop the growth philosophy that is integral to capitalism, and thereby stop unbridled growth. Some growth will be necessary in for example economy and science, but it is imperative that growth is to be rationally controlled instead of letting it give in to unbridled 'anarchy' (not to be confused with anarchISM). We must realize that growth is not necessarily absolute good.
Further, on the population growth I believe this is also a problem of society, not 'human nature' (I must warn against using that concept in political, economic or social discussions - it usually is a sign of having lost control of the debate and having to give in to the 'human nature' concept, which in itself is flexible and not absolute). In the Western world, we are taught that the nuclear family is good, two children an ideal. Children are viewed as a sign of success, for after all it is a sign of having enough money and personal resources to put offspring into the world. In earlier times, children were viewed as a simple, blunt necessity for survival - too many of them even a hindrance. So the urge to get as many children as possible is not necessarily a reflection of human nature, but more likely a result of the socially induced idea that children is a sign of success. It is that idea we must fight, and not its manifestation in the population growth. Attacking the manifestation of a problem in society is a tool of oppression, but what we have to do is to grasp the problem at the root (capitalism). That is the only way a just solution can be found.
