This is the sort of thing I think about when the pro-urban/pro-density/anti-car people talk about their vision for the world. I live in a city now, and the lack of substantial nature is suffocating to the extent that I plan to move. The idea that we should all live this way to conserve space—a resource which is only scarce in these urban places—seems excessive to put it mildly. EDIT: A lot of urban folks are rebuttin…
Most pro-density/pro-mass-transit people aren't arguing against rural lifestyle. They're against suburban, car-dominated lifestyle.
I'll conjecture that, for many people, the potential benefit of living "close to nature" is more than negated by driving everywhere. Commuting in a subway in a mega-city easily racks up thirty minutes of brisk walking per day.