Anyway, between my coworker and my planning colleagues' for-granted contempt of sprawl housing that takes up the entire countryside, it got me to wondering how bad the problem really is. Are we going to run out of land? If so, when? The other night an adjunct tossed out the following figures for Arlington County, one of the most densely settled jurisdictions in North America. There are, roughly, 200,000 residents in 34,000 households, or about 5.9 residents per household. Extrapolating that somewhat fishy number (do you know any 6-person households? I don't) to the entire country, all 300m of us translate into about fifty million households. Give each of those 1/8 acre (roughly the space needed for a modern mcmansion, including its portion of the street) and we'd cover 13,762 square miles, or a square about 117 miles on a side. In other words, the entire US population could fit into New Jersey, and everyone gets a detached house, yard and 2-3 car garage.
Now, you'd have to cross the river into PA to go to Target, because that doesn't include any space for retail, public or office/industrial buildings. But let's say that stuff takes up Delaware, or Manhattan. I don't want to think about the traffic on the turnpike in that case, but the point is that subdivisions on their own can't explain why the Washington, DC metro area extends from Baltimore to Fredericksburg, and as far as Hagerstown in the west. More than half of that must still be greenspace, but just contained in between housing developments instead of off by itself in the mountains. And this is why some of us who aren't religious new urbanists still try to push clustering of human settlements. Suburban greenspace tends to be manicured lawns, golf courses or tightly contained pockets of forest covering unbuildable geography. Most of it doesn't function well as wildlife habitat, and not at all as a useful resource for humans, i.e. you can't farm it either. Even without planting a house on literally every 1/8 acre in the country, we can still eat up all the land. And then ironically find ourselves without anything to eat.