According to National Geographic, by 2050 66% of the world's population will live in cities. Most Americans probably greet that news with a big yawn. We have seen the trend of urbanization here for decades.
But we don't consider what comes with urbanization. As people coalesce into cities, there are inherent challenges and problems. All people have needs for food, water, and shelter. When a population is spread out in villages, the land can more easily provide for those needs. Crops and livestock provide for the dietary needs. Streams and wells provide adequate water. Natural building materials can be used for constructing homes.
But when millions of people live in close proximity, the immediate area can't support the population. Food must be shipped in from far away. Local water sources must be supplemented with water piped in from other locations. Sewage must be treated and returned to waterways. Garbage must be hauled away.
As the world's population becomes more concentrated, more fossil fuels will be needed to transport food and garbage. Clean water will become more scarce. Sewage will be more difficult to dispose of.
We need to consider what large cities do to the environment. If the trend around the world mirrors what we see in the United States, there could be significant issues ahead.