Last week certainly was a “week to rejoice” if you love cities, although I think John Tierny missed the boat on exactly why. With the Accords signed, the sustainable (and not so sustainable) ranked, and the cul-de-sac revived and debunked, it was enough to give any aspiring urban planner a headache.

The statistics getting tossed around are staggering too. Just the first clause of the Urban Environmental Accords contains two rather impressive facts:

  • The majority of the planet’s population now (well, almost now) lives in cities;
  • continued urbanization will result in one million people moving to cities each week.

And that got me thinkin’: Whaddaya mean, “city?”

In search of the answer to this eloquent question, I headed to the webpages of the UN, since it is their Environment Program after all. Turns out that:

Because of national differences in the characteristics that distinguish urban from rural areas, the distinction between the urban and the rural population is not yet amenable to a single definition that would be applicable to all countries or, for the most part, even to the countries within a region.

Don’t worry, our hero will not give up that easily; more below the fold.I decided to, for now, say that a city is anything with over 1,000,000 people in it. Fine. Where does that leave us? From Thomas Brinkoff’s handy site, there are 428 “principal agglomerations” in the world with more than a million people in them. Summing their populations with a spreadsheet gives about 1.5 billion people. That’s more like a quarter of the world population, not half.

To me, the statistic proclaiming that a majority of the world’s population lives in cities is slightly misleading. While it may be technically true, when I think city, I think mega-city. I think New York City, or Tokyo, or Beijing. Especially when I think “green city,” I think of towering structures that “grow up, not out,” of public transportation that can whisk you from one side of town to the other quickly and cheaply, of integrated zoning that makes walking everywhere a possibility.

In order to say that half the world’s people live in cities, my guess is that we are going to have to include some of those dreaded suburbs as “cities.” So the challenge I set forth (besides making it through this post) is this:

How do you define “city?”