The growth of urban areas is harmful, because it brings unemployment and health, crime, poorness problems . In one only China , 18-20 million people leave their villages for moving to cities over year. As stated by Premier of the State Council (China) , the chinese economy have to incrise 7.2% in every year to avoiding from unemployment rising.
There is a famous saying that says "2 minds are better than one". You see town populations can benefit from more people coming in, and sharing ideas. As we have seen in our history, from time to time people moved to America. One time, there was an outburst of Europeans that came. One of the Europeans that came was Henry Ford. He had European background, and if it wasn't for him we would not have reached the stage that we are in today in the car industry. The CEO of Intel moved into America. Steve Jobs's parents were Syrian, but sent him off to America. And still Engineers, Doctors, Lawyers are all coming from other countries. If we had made it known of town population harms, we would not have reached our true potential in America.