In the last couple of years humanity passed an important threshold: We are now predominantly an urban species, with a little more than half our total population (now a little over 7 billion) living in cities of all sizes. Accordingly, the size of cities is growing as well. In 1950 there were 75 cities with populations larger than 1 million, and in 2011 there were 447. In 1950 the average size of the 100 largest cities was 2 million, and in 2011 it was 7.6 million (Engelke 2012). In 2007 there were 19 megacities with populations greater than 10 million, and in 2025 there will be 26. In 2007 there was only one megacity with a population greater than 20 million (Tokyo, at about 36 million, with more people than Canada). In 2025 there will be 8, with many in developing nations (Table 1, UN Habitat 2009).
Table 1. Megacities
|13||Rio de Janeiro||11,748||13||Cairo||15,561|
|18||Moscow||10,452||18||Rio de Janeiro||13,413|
Source: UN-HABITAT 2008. Data from UN Population Division, World Urbanization Prospects 2007. Figures for 2025 are projections. Note: Population figures are for urban agglomeration, not city proper. Megacities are cities with populations of more than 10 million.
By 2030, about 450 million people may be living in megacities. That will represent only 5-6 percent of the projected global population of about 8 billion. Many of those people will be very poor, and some will be very rich. In any case, the megacities, as centers of finance, governance, manufacturing, commerce, and culture will be powerful forces of change in the world, either for good or ill, or both.
Characteristics of megacities and the threats and opportunities that may arise from them have been noted by many authors. Energy use in cities can be more efficient, due to higher population densities, but higher population densities along with weaknesses in freshwater, food, and energy availability and waste treatment processes can create devastating poverty, disease, and suffering. Freshwater, food, and energy will flow into cities from areas around the cities, creating the potential for resource depletion around the cities, and the waste flowing out will pollute watersheds, air sheds, and coastal areas. Migrant poor will flow into cities to escape regional resource depletion. They will provide cheap labor for manufacturing and service industries, or they will end up in the slums and provide fodder for the socio-political revolution.
Transportation systems within and around megacities can grease the wheels of an effective economy if they are well designed and well maintained, or they can create physical gridlock, economic stagnation, noise, pollution, and health threats if they are not. Construction that is well regulated can create habitat for humanity, or if poorly created can create disasters large and small. Megacities are more vulnerable to natural disasters such as flooding, hurricanes, earthquakes, tsunamis, and heat waves (many of which may be exacerbated by climate disruption) just by virtue of their high population densities — but their wealth can also be used to build resilience (Niemczynowicz 1996, Molina and Molina 2004, Varis 2006, Lawrence et al. 2007, Wenzel et al. 2007, Adikari 2010, Kramer et al. 2011, Engelke 2012). In all cases, wealth will be a buffer against many of the problems described above, and poverty will exacerbate them. A persistent global economic downturn may have devastating effects on megacities and all large cities struggling with increasing demands placed on decaying infrastructure.
So, will megacities be a cauldron for revolution, or for technical innovation?
Let me propose that the answer to this question will be a function of the ability of megacity governance to manage growth (by both reproduction and migration) and resource consumption. A megacity will be a cauldron for revolution if it cannot manage both well, and an engine for innovation if it can.
This proposal implies at least a couple things. First, it implies that governance, and not the private sector, should have a strong role in managing growth and resources. Around the world we see that good governance, along with wealth, can overcome the confining influence of resource scarcity. Singapore is an example of a big city (pop. 5.26 million) where that dynamic plays out, and where the city is a crucible of innovation. Good governance in Singapore has manifested over the decades as strong and strict leadership and immigration policy, good public education, and the strong rule of law. (Singapore benefits too because it is also a state, with much greater control than most cities over the dynamics described above.) We can think of many other big cities and megacities around the world where poor governance and resource scarcity are contributing to poverty, disease, and social unrest. Cities like Singapore emerge in the global landscape, but that emergence is the result of many historical events, some planned, some accidental. It is not so easy to recreate that emergence in regions around the world where it might be important. Good governance, in megacities and everyplace else, will be an essential component for fostering that emergence.
Second, the proposal above implies that that both growth and resource consumption can effectively be managed. Although there are many policy level and technological mechanisms for providing this management, it seems true that there are fewer examples around the world where growth and resource consumption are managed effectively than where they are managed poorly or not at all.
China has managed population growth to some extent, with well-known downsides, but its resource management appears to be out of control. Population growth in the US has controlled itself through the demographic transition from high infant and child mortality and high fertility, to greater survival of infants and children and lower fertility. Some resource management in the U.S. (e.g. water and air quality, biodiversity) is good (but probably not excellent) on account of good governance, the luxury of wealth, and effective regulatory mechanisms. However, energy use in the US is out of control. Europe’s population growth is under control because of its own demographic transition (which brings an aging population to Europe, with its own set of problems), and resource management may be managed better there than in the US. But in most other parts of the world, especially in the developing nations of Asia and Africa, both population growth and resource management may be characterized, so far, as being beyond human control. If one considers the skyrocketing exponential curve describing the growth of human population on Earth over the last few hundred years, then the conclusion that population growth is out of control is almost inescapable.
The growth of cities around the world may be a large-scale, long-term dynamic that, like the growth of population in general, may be beyond human control. Step back for a moment, run history in fast forward, and watch the movement of humanity from what was once tiny groups widely dispersed across the surface of the Earth, each with relatively tiny and widely distributed ecological footprints, into increasingly concentrated agglomerations of larger and larger numbers with ever increasing footprints. It looks like an evolutionary process, a biologically hard-wired feature of social hominids. How far will that go? Where is the equilibrium point in the ratio between urban and non-urban humans on Earth? Is there an optimal ratio, from the human perspective? And if we can identify it, can we manage things in such a way that we might balance ourselves on it?
Biological organisms have size limitations based upon their food and other energy sources, their metabolisms, and other ecological constraints. We have no mammals on Earth any bigger than blue whales, and they only got so big, in part, because they can float. Maybe a city is like a biological cell, moving resources in across the cell membrane, turning them into biomass (and in the case of cities, into human products) and moving waste out. Surface to volume ratios are crucial. Just how big can a city get before it can no longer move sufficient resources in across its boundaries, and before it can no longer move sufficient waste out? And as a city approaches that point, how do those stresses become manifest in human health, wealth, and security? Greater emphasis on the study of the ecology of cities would be useful.
Other authors have proposed that managing megacities will require massive technical investment, institutional development, a mix of policy measures, strong political will in managing environmental challenges in a sustainable way, and public dialogue (Molina and Molina 2004, Varis 2006). Let me propose that if population growth and resource consumption can be managed at all, then it will most likely come from some combination of all those things plus good governance, strong regulatory structures, and fiscal incentives. By good governance I mean that which is relatively free of corruption and which has the common good in mind. This will include assuring that the urban poor have sufficient opportunities to keep them invested in the rule of law. Strong regulatory structures will protect resource systems (water, energy, agriculture, ecosystems) from despoliation for short term profit. Fiscal incentives will help modify individual and collective human behaviors. All of this will benefit from computer simulation modeling implemented with stakeholders from the cities and used to evaluate tradeoffs associated with different future strategies.
But the devil is in the details, and changing our current governance, policy and fiscal approaches so that they match all those proposed above will be no easy task. Perhaps all we can conclude is that for the question posed above — Will megacities be a cauldron for revolution or for technical innovation? – the best answer may just be ‘Yes.’ And both options, peacefully achieved, might be for the best.
Adikari, Y., R. Osti, T. Noro. 2010. Flood-related disaster vulnerability: an impending crisis of megacities in Asia. Journal of Flood Management 3 (3):185-191.
Engelke, P. 2012. The security of cities; development, environment, and conflict on an urbanizing planet. The Stimson Center, Washington, DC.
Kramer, A., M. H. Khan, and H.J. Jahn. 2011. Public Health in Megacities and Urban Areas: A Conceptual Framework. In A. Kramer (ed.), Health in Megacities and Urban Areas. Springer-Verlag, Berlin.
Gurjar, B.R., A. Jain, A. Sharma, A. Agarwal, P. Gupta, A.S. Nagpure, J. Lelieveld. 2010. Human health risks in megacities due to air pollution. Atmospheric Environment 44:4606-4613.
Lawrence, M.G., T.M. Butler, J. Steinkamp, B.R. Gurjar, J. Lelieveld. 2007. Regional pollution potentials of megacities and other major population centers. Atmospheric Chemistry and Physics 7 (14): 3969-3987.
Molina, M.J., L.T. Molina. 2004. Megacities and atmospheric pollution. Journal of the Air and Waste Management Association 54(6): 644-680.
Niemczynowicz, J. 1996. Megacities from a Water Perspective. Water International 21(4): 198-205.
United Nations (UN) 2009. State of the World’s Cities, 2008/2009; Harmonious Cities. UN Human Settlements Programme, Nairobi, Kenya.
Varis, O. 2006. Megacities, Development and Water. Water Resources Development 22(2): 199-225.
Wenzel, F., F. Bendimerad, R. Sinha. 2007. Megacities – Megarisks. Natural Hazards 42: 481-491.
Howard Passell is an ecologist at Sandia National Laboratories in Albuquerque, New Mexico, USA.