Demographic information from the United Nations Organization has triggered widespread discussion of the degree of urbanization on the planet. According to UN figures, we are very close to 50/50 urbanization -- half the population living in cities, half in rural areas, and by 2030, well over 60% of the planet will be urban. But are these figures correct?
Research from France's Institut de Recherche Pour le Développement (IRD) says no. The UN models are too weighted towards Western-style urban development, they say, and overestimate the number of people in permanent residence in cities in the developing world. By drawing on historical records of developing world urban patterns, the IRD claims that the real urbanization patterns are far less dramatic than the UN has suggested. How much of an error are we talking about? Maybe a billion people:
This new model indicates that, on the global scale, the proportion of individuals living in towns and cities would be 49.2% by 2030, compared with 60.8% estimated by the UN model. This means that the urban population could amount to one billion fewer people than predicted. In 2030 most of the population of developing countries would not be urban: 55.4% of individuals would still live in rural areas. This would especially be the case in Africa (59.5%) and Asia (59.0%).
According to the IRD, the errors are partially the result of a lack of widely-accepted definitions of urbanization; an area is considered urbanized in China, for example, when it has 100,000 concentrated residents, while in Burundi, only 2,000 residents are required for a locale to be considered "urban."
If the degree of urbanization over the next 25 years will be lower than predicted, it has important implications for both development and environmental policies:
[Since] the urban way of life is often considered as a determining factor in the speed of demographic changes, the reduction of mortality and fecundity in the developing countries could be less than predicted. Moreover, these new projections bear considerable consequences for environmental policies. In a world that would be less intensively urbanized, the industrialized countries would still be the main producers of greenhouse gas emissions and the essential part of natural resources would remain located in the regions of the South.
As the argument is not about facts so much as predictions, there are doubtlessly good arguments in support of each approach to urbanization numbers. That said, the IRD research is a warning flag that we need to do a careful evaluation of the data used to model city growth in the developing world. The more aggressive UN numbers may well turn out to be accurate, and still make for useful working numbers, but the impact of error on development and environment policies would be enough that independent validation of the UN models is definitely warranted.