&quot;Already huge cities like Beijing or Delhi (India) are having huge problems (waste, energy, water, air quality, and all kinds of pollution, transport, ...) which easily could lead to very nasty scenarios.&quot;<p>I seriously doubt the waste and environmental impact per capita in urban communities approaches the staggering amounts of waste and environmental devastation caused by suburban living.  Having many people living in close proximity increases opportunities to optimize energy efficiency and control environmental impacts.<p>Look at the water used to create lawns out of deserts in Arizona and California, the natural environments paved over for parking lots, and the greenhouse gases produced by hour commutes by one person in an SUV.