We need far more than a place to squat. We need water, food, and warmth. And, whether we realize it or not, we need large wilderness areas, uninhabited by human beings. In terms of environmental impact, crowding humans together in cities preserves natural area better than spreading us evenly over the whole land. This, like all migration-control attempts, provides only a temporary reprieve.
Population centers send out their tentacles to bring in supplies from rural and natural areas.
To roughly figure your ecological footprint, take this simple 13 question quiz . Consumption has a lot to do with our footprints, and reproduction amplifies consumption. Do not count adopted, foster, or step children. When our population density improves, we won't have to convert natural ecosystems into agriculture, industry, housing, and amusement farms. Viewing Earth at night reveals just how little uninhabited area remains.