Describing a plan for Melbourne, Australia, Alex Steffen explains how urban density improves quality of life for everyone:

The city’s growing quickly, needs to add a million people over the next decade or two, but they don’t want that to be sprawl. So they took a digital map of the city and blocked off everything that’s currently single-family residences, everything that’s a historical building, everything that’s green space, working industrial land, and other things people are vociferous about valuing. That left a fairly small percentage of land.