Over the next thirty years, the world's urban population could double from 2.6 billion in 1995 to 5.2 billion in 2025. Most of this growth will take place in developing countries, where some 4 billion people (over half of the total) could be living in cities by 2025, compared with 1.5 billion (37%) in the early 1990s. Particularly significant will be the growth of very large cities, so-called mega-cities. In fact, 36 or so cities around the world will have over 8 million inhabitants by 2015, and most of them will be in developing countries.
In the shorter term, rapid urban growth will be fuelled by high natural population increases within cities, combined with a high level of immigration from rural areas, reflecting the gradual shift from agriculture and other primary activities to manufacturing and services. In the longer term, the rate of urban growth should eventually slow as a result of lower fertility rates and a deceleration in the urbanisation process itself, as a growing share of the population becomes urbanised. For instance, in West Africa -- one of the regions of the world experiencing the fastest growth in population -- the expansion of city population should slow to 4.2% per year between 1990 and 2020, compared with 6.3% annually over the previous 30 years.
Not that reduced fertility will immediately prevent a marked increase in the working-age population. As many as a billion new jobs may be needed between 1990 and 2025. Most of these jobs will have to be created in cities as the non-agricultural labour force is expected to grow three times as quickly as the agricultural labour force.
Particular attention will have to be given to nurturing the informal sector, where most of the new jobs will be, in small-scale manufacturing, services and trade. Boosting the productivity of poor workers would be a major help; in West African cities the informal sector could absorb as much as 44% of the population in 2020, while generating only 23% of gross regional product.
The population explosion in the world's cities will lead to serious social problems, with widespread poverty, exclusion and destitution. Remedial action will be required, with comprehensive social measures to provide basic services in education, health, nutrition, family planning and vocational training.
The environmental risks in developing world cities will be legion. Insufficient shelter, inadequate sanitation, poor water supply, air pollution and congestion on the streets are all to be expected. Huge investments could help prevent the worst excesses of this, perhaps to the tune of $100-$150 billion a year world-wide. The lion's share will come from the revenues of national and local governments. Some will come from the private sector, including foreign direct investment. Official development assistance will at best act as a top-up, unless recent declining trends are radically reversed.
Problems like these have led many to dismiss the city's role in the future world economy, almost to the point of predicting its demise at the hands of new technologies. However, the potential of cities will be enormous, with urbanisation representing a major opportunity, for developing countries in particular in terms of overall spatial planning.
Channelling rural migration into cities can help relieve damaging population pressure on marginal rural land. Focusing development in cities themselves will, on balance, continue to bring economies of scale, in terms of transport, waste treatment and, of course, business. And even if there are countering forces of decentralisation enabled by new technologies, other technological innovations, such as in emissions control and communications, may make cities more attractive. So, though information and communications technology may generate a greater geographic dispersion of economic activity in the future, urbanisation will continue to be a major force of economic development.
In fact, the importance of cities could well grow in the 21st century. One reason is that they will sharpen their profile in the open and competitive international space of the new global economy. The importance of cities is likely to be strengthened by the creation of global city networks. These networks will give cities greater autonomy of action to tap into international markets and forge new economic links across national boundaries. The city will be conditioned by those networks, both politically and architecturally, and often to a greater extent than by their regional or national hinterlands. These networks will act as highways for the transfer of knowledge and best practice, for stimulating innovation in policy and project development; and as catalysts in economic co-operation.
Cities in developing countries will have to be particularly determined that they are "plugged" into these networks so as to profit from them and to avoid being sidelined. Sao Paulo or Beijing should therefore see to it that they are as much part of the network as Paris or London, but so too should medium cities, from Bahia Blanca to Bordeaux. Networked cities are rich in promise and diversity, giving us all an urban future to look forward to. (See Society article on Learning Cities.)
©OECD Observer No 217/218, Summer 1999