We are polluting the air, water and land in many ways and the more people we have, the more pollution we produce. If each of us reduced our carbon footprint by half, for example (very unlikely, of course) and the population doubled, we would have achieved nothing. And we actually increase our footprint and increase the number of people. We are running out of both renewable (e.g. water, food) and non-renewable (e.g. oil) resources, and the more people there are, the less there is around. It's simple arithmetic: more people, less things per person. Resource shortages and simple overcrowding within a country lead them to look longingly to the resources of their neighbors – and wars often result. Hitler's expansion into Europe took place under the title: Lebensraum: living space. The Germans did not have enough space in Germany, so they took control of neighboring countries. Overpopulation is a problem for both rich and poor countries. While poor countries tend to have higher birth and growth rates, rich ones use more resources and create more pollution per capita. Look at me...