One of the long-term secular trends in human society is urbanization. From the earliest proto-cities to today's megalopolises, people keep packing themselves into smaller and smaller areas, in larger and larger numbers. The implications -- on everything from ethics to the environment -- are profound, as Stewart Brand explains:

For 50 years, the demographers in charge of human population projections for the United Nations released hard numbers that substantiated environmentalists' greatest fears about indefinite exponential population increase. For a while, those projections proved fairly accurate. However, in the 1990s, the U.N. started taking a closer look at fertility patterns, and in 2002, it adopted a new theory that shocked many demographers: human population is leveling off rapidly, even precipitously, in developed countries, with the rest of the world soon to follow. Most environmentalists still haven't got the word. Worldwide, birthrates are in free fall. Around one-third of countries now have birthrates below replacement level (2.1 children per woman) and sinking. Nowhere does the downward trend show signs of leveling off. Nations already in a birth dearth crisis include Japan, Italy, Spain, Germany, and Russia -- whose population is now in absolute decline and is expected to be 30 percent lower by 2050. On every part of every continent and in every culture (even Mormon), birthrates are headed down. They reach replacement level and keep on dropping. It turns out that population decrease accelerates downward just as fiercely as population increase accelerated upward, for the same reason. Any variation from the 2.1 rate compounds over time.

That's great news for environmentalists (or it will be when finally noticed), but they need to recognize what caused the turnaround. The world population growth rate actually peaked at 2 percent way back in 1968, the very year my old teacher Paul Ehrlich published The Population Bomb. The world's women didn't suddenly have fewer kids because of his book, though. They had fewer kids because they moved to town.

Cities are population sinks -- always have been. Although more children are an asset in the countryside, they're a liability in the city. A global tipping point in urbanization is what stopped the population explosion. As of this year, 50 percent of the world's population lives in cities, with 61 percent expected by 2030. In 1800 it was 3 percent; in 1900 it was 14 percent.

The environmentalist aesthetic is to love villages and despise cities. My mind got changed on the subject a few years ago by an Indian acquaintance who told me that in Indian villages the women obeyed their husbands and family elders, pounded grain, and sang. But, the acquaintance explained, when Indian women immigrated to cities, they got jobs, started businesses, and demanded their children be educated. They became more independent, as they became less fundamentalist in their religious beliefs. Urbanization is the most massive and sudden shift of humanity in its history. Environmentalists will be rewarded if they welcome it and get out in front of it.

Brand amplifies on that last point about "getting out in front" of urbanization as follows:

The best way for doubters to control a questionable new technology is to embrace it, lest it remain wholly in the hands of enthusiasts who think there is nothing questionable about it.

And he also argues that it's time for true environmentalists to get behind nuclear power and to get out in front of it as well by agitating for the use of modern nuclear technologies like pellet-bed reactors.

I really liked the way Stewart Brand questioned assumptions in How Buildings Learn, and that seems to be one of his signature traits. Perhaps it's time for me to finally read The Clock of the Long Now (I've just requested it from the Denver Public Library).

Peter Saint-Andre > Journal