Citydwellers are more eco-friendly than almost everyone else:
“The city is the most environmentally benign form of human settlement. Each city-dweller consumes less land, less energy, less water, and produces less pollution than his counterpart in settlements of lower densities.”
Whole Earth Discipline, Stewart Brand
Environment aside, some people have actually suggested that moving everyone to the city is the only way to tackle poverty:
“Cities are so much more successful in promoting new forms of income generation, and it is so much cheaper to provide services in urban areas, that some experts have actually suggested that the only realistic poverty reduction strategy is to get as many people as possible to move to the city.”