Cities and urban areas are gaining an estimated 60 million people per year - over 1 million every week. In many developing countries cities are growing two or three times faster than the overall population. As urban areas - particularly smaller towns and cities - continue to grow in size, about 5 billion people are expected to live in cities by 2030 - about 61 per cent of the global population of 8.1 billion, the UN projects.
Some cities have had astonishing population growth rates. Dhaka, Bangladesh, for example, nearly doubled in population between 1990 and 2000, gaining some 6 million people. Mumbai (Bombay), India, has now grown to over 17 million, and by 2015 it will probably be the world's second largest city, after Tokyo, Japan.
However, the rates of increase are not unprecedented. Many countries in West Europe or North America had periods when the proportion of the population living in towns and cities increased as rapidly.
Dona Marta favela, Rio, Brazil
© John Maier/Still Pictures
In addition, it was not only in Africa, Asia and Latin America that there was rapid urban change. Many cities in North America figure among the world's fastest growing cities during the 20th century (see Facts and Figures on the largest and fastest growing cities).
As the 21st century begins, cities around the world continue to be engines for economic growth in a global economy, and centres of social change and cultural diversity. Cities attract people from the countryside, from neighbouring countries, and even from around the world.
Yet many cities face a crisis. If they cannot cope with the massive influx of people, then poverty will continue to be endemic, and discontent and civil unrest could become chronic.
Most of the world's urban population - like most of the world's total population - lives in developing countries. In 2000, developing countries had 2 billion urban dwellers compared with only 900 million in the more developed regions. Asia had 1.4 billion urban residents, including China, with 479 million urban residents, and India, with 285 million.
In the next 30 years virtually all population growth will be in urban areas of developing countries. According to the latest UN projections, the urban population of developing countries will double, from just under 2 billion in 2000 to nearly 4 billion by 2030. In contrast, the urban population of the developed countries is projected to increase modestly - from 900 million in 2000 to 1 billion in 2030.
With the exception of Latin America, the developing world, which has been largely rural throughout history, remains much less urban than the developed world. In the more developed regions today, about 74 per cent of the population lives in urban areas. By 2030, 82 per cent of the population will be urban. Currently, in developing countries as a whole, only 40 per cent of the population lives in urban areas. By 2030, however, 56 per cent are projected to be urban. Thus, while the proportion urban will remain considerably less in developing countries than in developed countries, the increase will be more rapid and, in absolute numbers, much greater.
By 2030 each developing region is expected to have an urban majority, but the level and pace of urbanisation vary substantially among developing regions. The Latin America and Caribbean region already is as urban as Europe or North America, at an estimated 75 per cent urban. In contrast, Africa and Asia are only 37 per cent urban.
The largest percentage increases in the urban population, however, will be in Africa and Asia. The urban population of Africa is projected to increase to 53 per cent by 2030, and Asia's to 54 per cent. The percentage of the population of Latin America and the Caribbean that is urban is projected to increase to 84 per cent by 2030.
Migrant family on the outskirts of Nairobi
© Trygve Bolstad/Panos Pictures
In developing regions the actual size of urban population growth will be without precedent. By 2030 Africa, with a projected 787 million urban residents, will be second only to Asia's 2.7 billion among the world's regions in the size of the urban population. Generally considered already overwhelmingly rural, Africa already has a larger urban population than North America.
Over the next 30 years Asia is expected to gain over 1.3 billion urban residents. South Asia faces the most daunting prospects. India's urban areas will grow by a projected 297 million residents, Pakistan's by 86 million, and Bangladesh's by 64 million.
As population grows, the number of big cities will grow substantially. By 2015 the world will have 482 cities with 1 million or more residents. Of these, 326-about two-thirds-will be in developing countries. The number of "megacities" of 10 million people or more also will increase. Worldwide by 2015, 21 cities will be this big, all but four in developing countries. The largest share of the increase in the urban population, however, will be in cities with fewer than 500,000 inhabitants and in those with a population of between 1 and 5 million.
The world's population has been growing for at least 8,000 years, ever since the systematic cultivation of plants and the domestication of animals made permanent human settlements possible. Although large cities have existed in the developing world for centuries - Xi'an in China had one million inhabitants in 500 AD - it was not until the second half of the 20th century that accelerated population growth and migration propelled urbanization to new levels. Primarily reflecting trends in developing countries, the world's urban population more than tripled between 1950 and 2000, from 750 million to 2.9 billion.
In developing countries today rapid urban growth reflects three factors: migration to cities from rural areas; natural population increase (births minus deaths) among city residents; and reclassification of previously rural areas as urban, as they became built up. Urban areas will most likely continue to attract people from the countryside both because cities and larger towns offer more opportunity and because of stagnant rural economies, inequitable land distribution and degraded environments.
In the latter part of the 20th Century, natural population increase played a greater role in urban growth in developing countries than did migration. Between 1960 and 1990 an estimated 60 per cent of urban growth in developing countries, excluding China, occurred from natural increase. In China, by contrast, over the past two decades 70 per cent of urban growth was due to migration from rural areas.
Now, more and more people are leaving rural areas for cities. In 2000 half of urban population growth was due to in-migration. Over the next 30 years, in-migration is expected to play a more important role in urban growth than natural population increase. Meanwhile, fertility has fallen more in cities than in rural areas. Primarily reflecting in-migration, during the next 30 years the world's urban population is projected to grow at an average rate of 1.8 per cent per year, much more than the world's average annual total population growth of 1 per cent per year.
Because of out-migration, population growth in rural areas has come to a virtual standstill. Among the developing regions, only in Africa and the small islands of Oceania will rural populations continue to increase. In contrast, Asia's rural population will decrease by an estimated 26 million-from an estimated 2,297 million in 2000 to a projected 2,271 million in 2030.
In Africa urban areas are growing three times as fast as rural populations, reflecting massive in-migration from the countryside. The percentage of population living in urban areas of Africa is projected to continue increasing substantially.
In many developing countries urban areas are magnets that attract people from small towns and the rural areas, because cities offer more hope of jobs, education, health care, and better living standards. Big cities in particular are economic, social, and cultural centers. Mexico City, for example, accounts for about 30 per cent of the country's total Gross Domestic Product. Greater Seoul, South Korea, has one-quarter of all universities in the country. Bangkok, Thailand, contains three-quarters of the country's non-cellular telephones, one-half of all motor vehicles, and one-fifth of commercial bank deposits. Abidjan accounts for 70 per cent of all economic and commercial transactions in Côte d'Ivoire.
In Latin America, Caracas contains three-quarters of all industries in Venezuela and accounts for 61 per cent of the Gross Domestic Product. Lima accounts for 43 per cent of Peru's Gross Domestic Product.
People also leave rural areas to escape population pressures and environmental deterioration that make it increasingly difficult to survive there. Rapid population growth among low-income groups in rural areas has put overwhelming pressure on key resources-agricultural land, forests, and water. These pressures have been made worse by large-scale export-oriented agriculture, loss of land tenure among poor farmers, declining soil fertility and national policies that encourage agricultural intensification and consolidation of land holdings. With moribund rural economies and limited ways to make a living from the land, many rural poor are pushed into urban areas.
One major effect of rapid population growth in some developing countries is the shrinking size of family farms, as plots are divided into smaller and smaller pieces for each new and larger generation of male heirs. In 57 developing countries surveyed by FAO in the early 1990s, over half of all farms were less than one hectare in size, not enough to feed the average rural family. In India three-fifths of all farms are less than one hectare.
At the same time, more and more agricultural land is being taken out of production because of soil degradation, a result mainly of wind and water erosion, loss of soil nutrients, and poor irrigation systems that cause salinization and water-logging. Globally, land degradation threatens the livelihoods of at least one billion small-scale farmers and ranchers, almost all in the least developed countries.
As their populations grow, more and more countries are facing water shortages. Today about half a billion people live in 31 water-short countries. By 2025 there could be nearly 4 billion people living in about 50 countries suffering from water shortages for all or part of the year.
The agricultural labour force is expected to continue to drop during the first half of this century, as the agricultural revolution that has reduced labor needs on farms and plantations spreads throughout the developing world. There were an estimated 1.1 billion small-scale farmers and farm workers worldwide in the mid-1990s. If one-third of them are displaced over the next half century, as some studies project, developing countries will have to create as many additional nonagricultural jobs for farmers as now exist in all the developed countries together. Meeting this need would fall primarily to urban economies, as the main engines in job creation for displaced rural populations.
One of the main challenges of urbanisation will be to spread the benefits of development and diffuse urban population growth. Smaller urban areas can take advantage of special skills, access to critical resources, geographic location, economies of scale, and communication systems to attract residents and to stay competitive with major urban areas in the global economy. But for secondary cities to become attractive for investment, they need good local governance and improvements in transport and telecommunications.
Another challenge is the growth of slums. At present, over 900 million people – almost one in three of the world's urban population – are slum dwellers, and in 30 years’ time that number is likely to double to 2 billion, unless serious action is taken, according to UN-Habitat.
Snapshot of an Urban Dweller
Marina Lupina, an attractive women in her mid-20s, and her two children live in one of Manila's largest slum areas, called Apelo. She lives in a shack built from discarded wood and cardboard with a rusty piece of corrugated iron for a roof, next to a fetid, refuse-clogged canal.
By selling recycled cloth, Marina earns just enough to buy rice, fish and clothing. Like millions of others in big cities of developing countries, she has come in quest of a better life than the one she left behind in strife-torn Mindanao. Despite her poverty, Marina believes that she and her children have more opportunities in the city than if they had remained in the countryside.
The dirty water from this canal in
Apelo is use by the locals
for everyday use.
© Don Hinrichsen
"I can earn $2-3 dollars a day selling recycled cloth," she says with a broad smile. "In the rural village I came from on Mindanao, I would be lucky to earn fifty cents a day as a farm laborer."
She is quick to point out that both her girls are in school because a local NGO helps with school fees and uniforms. Marina also has access to quality medical care, including reproductive health, for herself and her children thanks to the work of a crusading doctor who helped the women of this community set up their own health clinic. Known as the Likhaan Clinic (which means "creation") the fees are not set. The women use an informal pay-as-you-can system.
"I consider myself lucky to be here at all," says Marina, gazing up from her work sewing pieces of cloth together. "My girls will definitely have a better life than I had. That's the main reason I came to Manila. We will stay no matter what."
This overview was researched and written by Don Hinrichsen. A contributing editor to People & the Planet, he is co-author of the recent issue of Population Reports on population and urbanisation Meeting the Urban Challenge
See also: Why the cities have grown by David Satterthwaite.
© People & the Planet 2000 - 2006