Thank you for taking about one of the biggest ignored issue. Let me state that while I think cities have a place in a modern economy, i'm against hyper-urbanization. Many villages and towns in the country side are dying. People think moving to the city is trendy, but they don't realize they're building a hostile environment for future generations.
I live in the suburbs outside a megacity. It's thousands of houses that all look the same. The developers just copy as paste them. While the parents drive to work, the children have nowhere to go. They have tiny front yard, with 5 feet of grass separating their driveway and the neighbors lawn.
The kids have to bicycle over a kilometer, just to find a small woodlot. Our ancestors use to be connected to the land. They use to surround themselves in nature, and wake up every morning to beautiful pastures, a river, and gorgeous mountains on the horizon.
What do the children have today? Endless streets, and nowhere to go, so they stay inside and play video games.
If I could recreate the world, I wouldn't let the biggest city grow over 500 000 people, and we would only have 100 000 000 on the planet. There would be plenty of rain forest left, because there would be less farms to feed the people.
We got to get people moving to underpopulated areas, instead of wanting to come to the city. Look a the havoc overpopulation has caused on India.
Cities are tiny in comparison to the farms required feed their citizens. Look at this image of South America. 1000 years ago it would be solid green. Over half of South America's Rain forest have been wiped out. If the population continues to expand northward, most of the Amazon will be wiped out. If we keep the population down, we can avoid a lot of environmental problems. If everyone on the planet had no more than 2 children, we could ethically reduce our population to sustainable levels. If the population continues to increase the price of food will skyrocket, the oceans will run out of fish, housing prices will become astronomical, and will spend endless hours stuck in traffic. We will have to work longer hours to pay for overpriced resources, when supply can't keep up with demand.
hahaha that pic tho