Kurt Vonnegut, Jr., famously suggested that sooner or later we shall bioengineer ourselves smaller and smaller, and so keep expanding numerically even if becoming microscopic in the process.

From my outlook as a legroom and wide open spaces loving guy, we have already moved too far in the wrong direction. Megacities, however, are the latest logical extension of a tendency to cluster into ever greater collections of ourselves. Megacity Manila now averages 111,000 people for every square mile. In megacity Tokyo, there are 35 million of us. The top ten megacities by population (Tokyo through Karachi in the listing below) average just under 25,000,000 each. Only the top 6 megacities together account for 159 million of us, more than half the U.S. population.

In 15-20 years, the number of such megacities (population centers of at least 10,000,000) is projected to be about 40-50. There are already over two dozen of them, a number expected to continue to rise by leaps and bounds as urbanization takes hold in Third World countries. In order of population, largest first, these current super-cities are:

1. Tokyo 2. Guangzhou 3. Jakarta 4. Seoul 5. Shanghai 6. Mexico City 7. Delhi 8. New York City 9. Sao Paulo 10. Karachi 11. Mumbai 12. Manila 13. Los Angeles 14. Osaka 15. Beijing 16. Moscow 17. Cairo 18. Kolkata 19. Buenos Aires 20. Dhaka 21. Bangkok 22. Tehran 23. Istanbul 24. Lagos 25. Rio de Janeiro 26. London 27. Paris

One of the world's many megacites, Tokyo, Japan (Wikipedia)

Manila shows us that people may exist much more closely packed than we typically imagine. Were New York City (which covers an area of roughly 500 square miles) today as dense as Manila, about 50 million Homo sapiens would live there. Imagine a world, of perhaps the year 2100, in which most megacities are at least that dense, and you may see how there could one day be many, many more of us than are around today.

Among nations with a large census, China, rushing to build the infrastructure for numerous huge new population centers, is probably the most ambitious. By 2017, five years hence, its plan is to create a vast megalopolis of 42 million inhabitants in the Pearl River Delta district. This may be only the beginning. Not shy about securing its interests, that nation's 20-year building explosion calls for a mean construction of over 1000 skyscrapers a year, like adding one New York City every twenty-four months, to accommodate its rising flood of urban dwellers. China is also hurrying to lock in access to global supplies of steel and other materials needed for that kind of boom.

While the potential is impressive for business and economic stimulus from such regional or global growth projections, so are the probable challenges.

• Are there enough industrial commodities in the world for such sustained levels of construction?

• Can the transportation needs of these burgeoning mega-populations be addressed?

• Is reasonably good and inexpensive health care a luxury which we cannot afford in a multi-megacities world?

• How shall enough housing be provided in so short a time?

• From where will the funding come for such growth to be sustainable?

• Are there any significant disease problems with unprecedented levels of urbanization?

• How will sufficient water resources be provided for the industrial, agricultural, and potable liquid needs of vast new urban centers?

• What about the impact of natural disasters when populations are so closely crammed?

• Can governments function efficiently enough to cope with the needs of rapidly rising city populations?

• Can all these megacities be built and sustained without aggravating global warming?

• How will the energy needs of future megacities be provided?

• Will there be enough jobs? Clearly not everyone can work in construction.

• Can law enforcement, intelligence services, and the military keep up with lawlessness, unrest, or terrorism in huge population centers?

• Can environmental pollution be kept within reasonable limits despite the addition of hundreds of millions of new megacity residents?

• How must individual rights and freedoms be curtailed to assure enough of us can live together within the smaller and smaller remaining areas?

Meanwhile, as in the old Chinese curse, we now live in interesting times. It will be fascinating to see how such tests or dilemmas are resolved in the years ahead.

I have so far been looking at the growing trend toward more and larger megacities with a jaundiced eye. Perhaps, though, in the "brave new world" toward which we are bullet-train-speeding, more numerous and bigger cities simply make sense and so might be seen at least as accurately from an optimistic perspective.

After all, just as bee, ant, or termite colonies can function far more efficiently than if the same number of individuals were spread over relatively large areas, there are many synergies possible among humans who live in swarms. Maybe I should try it. I might like it. Certainly many folks who live in The Big Apple feel they are in the best of all possible places and find great personal reward in thus being "megacitizens."