### A world made of cities
Cities are the human organizations with the greatest longevity but also the fastest rate of change. Just now the world is going massively and unstoppably urban (governments everywhere are trying to stop it, with zero success). In a globalized world, city states are re-emerging as a dominant economic player. Environmental consequences and opportunities abound.
As the author of _How Buildings Learn_ I kept getting asked to give talks on "How Cities Learn." With a little research I found that cities do indeed "learn" (adapt) impressively, but what cities mainly do is teach. They teach civilization.
I started with a spectacular video of a stadium in Philadelphia being blown up last year. The announcer on the video ends it, "Ladies and gentlemen, you have just witnessed history!" Indeed demolition is the history of cities.
Cities are humanity's longest-lived organizations (Jericho dates back 10,500 years), but also the most constantly changing. Even in Europe they consume 2-3% of their material fabric a year, which means a wholly new city every 50 years. In the US and the developing world it's much faster.
Every week in the world a million new people move to cities. In 2007 50% of our 6.5 billion population will live in cities. In 1800 it was 3% of the total population then. In 1900 it was 14%. In 2030 it's expected to be 61%. This is a tipping point. We're becoming a city planet.
One of the effects of globalization is to empower cities more and more. Communications and economic activities bypass national boundaries. With many national governments in the developing world discredited, corporations and NGOs go direct to where the markets, the workers, and the needs are, in the cities. Every city is becoming a "world city." Many elites don't live in one city now, they live "in cities."
Massive urbanization is stopping the population explosion cold. When people move to town, their birthrate drops immediately to the replacement level of 2.1 children/women, and keeps right on dropping. Whereas children are an asset in the countryside, they're a liability in the city. The remaining 2 billion people expected before world population peaks and begins dropping will all be urban dwellers (rural population is sinking everywhere). And urban dwellers have fewer children. Also more and more of the remaining population will be older people, who also don't have children.
I conjured some with a diagram showing a pace-layered cross section of civilization, whose components operate at importantly different rates. Fashion changes quickly, Commerce less quickly, Infrastructure slower than that, then Governance, then Culture, and slowest is Nature. The fast parts learn, propose, and absorb shocks; the slow parts remember, integrate, and constrain. The fast parts get all the attention. The slow parts have all the power.
I found the same diagram applies to cities. Indeed, as historians have pointed out, "Civilization is what happens in cities." The robustness of pace layering is how cities learn. Because cities particularly emphasize the faster elements, that is how they "teach" society at large.
Speed of urban development is not necessarily bad. Many people deplored the huge Levittown tracts when they were created in the '40s and '50s, but they turned out to be tremendously adaptive and quickly adopted a local identity, with every house becoming different. The form of housing that resists local identity is gated communities, with their fierce regulations prohibiting anything interesting being done by home owners that might affect real estate value for the neighbors (no laundry drying outside!). If you want a new community to express local life and have deep adaptivity, emphasize the houses becoming homes rather than speculative real estate.
Vast new urban communities is the main event in the world for the present and coming decades. The villages and countrysides of the entire world are emptying out. Why? I was told by Kavita Ramdas, head of the Global Fund for Women, "In the village, all there is for a woman is to obey her husband and family elder, pound grain, and sing. If she moves to town, she can get a job, start a business, and get education for her children. Her independence goes up, and her religious fundamentalism goes down."
So much for the romanticism of villages. In reality, life in the country is dull, backbreaking, impoverished, restricted, exposed, and dangerous. Life in the city is exciting, less grueling, better paid, free, private, and safe.
One-sixth of humanity, a billion people, now live in squatter cities ("slums") and millions more are on the way. Governments try everything to head them off, with total failure. Squatter cities are vibrant places. They're self-organized and self-constructed. Newcomers find whole support communities of family, neighbors, and highly active religious groups (Pentacostal Christians and Islamicists). The informal economy of the squatter cities is often larger than the formal economy. Slum-laden Mumbai (Bombay) provides one-sixth of India's entire Gross Domestic Product. The "agglomeration economies" of the burgeoning mega-cities leads to the highest wages, and that's what draws ever more people.
So besides solving the population problem, the growing cities are curing poverty. What looks like huge cesspools of poverty in the slums are actually populations of people getting out of poverty as fast as they can. And cities also have an environmental dimension, which has not yet been well explored or developed.
There has been some useful analysis of the "ecological footprint" that cities make on the landscape, incorporating the impacts of fuel use, waste, etc. but that analysis has not compared the per-person impact of city dwellers versus that of people in the countryside, who drive longer distances, use large quantities of material, etc. The effect of 1,000 people leaving a county of 1,000 people is much greater than that of the same 1,000 people showing up in a city of one million. Density of occupation in cities has many environmental advantages yet to be examined.
At present there's little awareness among environmentalists that growing cities are where the action and opportunities are, and there's little scientific data being collected. I think a large-scale, long-term environmental strategy for urbanization is needed, two-pronged. One, take advantage of the emptying countryside (where the trees and other natural systems are growing back fast) and preserve, protect, and restore those landscape in a way that will retain their health when people eventually move back. Two, bear down on helping the growing cities to become more humane to live in and better related to the natural systems around them. Don't fight the squatters. Join them.