How Much Larger Can Our Cities Grow?


Many cities were begun in constrained environments, and the cost of continued expansion in their areas is rising. Many of the cities I have visited were started in places that naturally attracted humans – bays and estuaries, confluences of rivers, and other places where water and food sources were relatively more abundant and the climate was relatively favorable. I notice, however, that now that the human population has reached more than six billion these places are increasingly challenged for space, infrastructure, or resources of some important sort. At the same time, however, some are actually in a population decline, and some even have a declining “rate of sprawl.” The picture is complex, and differs significantly between developed and developing countries. So how are things likely to change from here, and how can we affect the situation positively?

Infrastructure costs may be rising faster than populations, but this can’t continue forever. Coastal cities have often used up the available land that is easy to build on, and I expect that the cost of building bridges, causeways, and tunnels to interconnect their parts is increasing at a rate faster than the population. Cities in more arid non-coastal areas are stretching available water supplies, and suburban sprawl is becoming more and more of a problem in most places as smaller cities around the big cities grow, some as bedroom communities and some because they provide other key elements or features. In general, as cities grow, they need more and larger roads to handle the movement of people and goods, and I would be interested in seeing a comparison between, say, the square area of roads built, the congestion of those roads, and the population over time. I imagine that the situation in this more-easily measured part of the infrastructure will be paralleled by the water, sewer, electrical, and information infrastructures, and projections based on such data might suggest a point where infrastructure growth exceeds the means to support it. In the meantime, as infrastructure is expanded and stretched, systemic risks grow at an increasing rate.

Many older and larger cities, especially in the developed world, have already begun to decline. I am in Miami now – my first time – and I could clearly see on the plane flight in over the Everglades that the city has been straining to push westward into the low, swampy land, constrained by the coast, and building more and increasingly higher buildings to contain its growing population (link). The cost of building on increasingly less-suitable land has to be going up, and it is quite possible the expansion rate has already begun to slow.

Total population growth, increased urbanization, and increased risk of catastropes are mostly occurring in the developing world. The United Nations currently expects the world population to continue to expand and possibly peak at around 9 billion in 2050 (link), and the bulk of the growth can be expected to be in cities of all sizes. Personally, I hope this number will never be approached. Interestingly, the highest growth rates and the bulk of the total (nearly 8 billion) are projected to be in the poorest third world countries and not in the developed world. The increasing risk of infrastructure collapse and local or regional catastrophes can only rise under the circumstances. That is not to say that the developed world isn’t at risk, as evidenced by hurricane Katrina striking New Orleans in 2005, but the death tolls in the least developed countries are staggeringly higher by comparison. (As I’ve noted in this blog before, though, none of the catastrophes in recent decades have been capable of creating more than a very minor, localized, and temporary slowing of population growth, nor have they had any noticeable impact on the world population explosion.)

Natural challenges to already-strained infrastructures can bring serious consequences. If the developing world follows what appears to be the trend in the developed world, the biggest cities will begin to grow more slowly as supporting cities in their hinterlands rise to support them, with smaller cities down to towns growing up nearby to either provide bedroom space, better living conditions, or key resources for the big cities. This suggests accelerating challenges to their infrastructures, however, and increased risk of systemic breakdown under the influence of major natural events (storms, earthquakes, etc.) or manmade disasters (wars, water shortages, etc.).

Voluntary birthrate reduction is the solution, the developed world needs to help, and you can help make that happen. The bottom line, and most effective, solution is still to curb birthrates. While this might be done using legislated solutions such as China’s one-child law, there is evidence (on which I have written previously in this blog) that economic and educational assistance, and development of family planning assistance systems, have the potential to reduce birthrates just as much, and have many added benefits that help at all levels: the individual, the family, the municipality, the region, the nation, and the world. We should each be persistently asking our government representatives to pursue these avenues in our assistance to developing world countries. We need to slow and stop population growth as soon as possible, or see the risk of regional and potentially more widespread catastrophes and infrastructure collapses greatly expanded, with highly undesirable consequences.

As always, I welcome your comments. – Tim

Interesting reading:
Population Distribution, Urbanization, Internal Migration and Development, Eduardo Lopez Moreno, Expert Group Meeting, United Nations Habitat
Report Card for America’s Infrastructure, the American Society of Civil Engineers

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