Our world is increasingly more urban, with people moving to the cities and towns that exist on every continent. People move to cities looking for new opportunities and a different and better life. This drift means that almost 50%, of the global population of more than six billion people, live in urban areas. This is continuing to grow at a rate of two and a half times that in rural areas. In 25 years time urban areas will contain more than 75% of the world's population.

Nairobi skyline (click for a larger image) (c) Sean Sprague/Panos Pictures

This rate of growth is greatest in the cities of the developing world, where there are twice as many people living in urban areas than in the developed regions. By 2015 it will be three times as many, by 2025, almost four times. Cities in Africa, Asia, the Middle East, and Central and South America are home to a third of the developing world's people. The developing countries already contain eight of the world's megacities, that is, cities with more than 10 million inhabitants. By 2015 there will be 26 such cities in the world.

Village One, Mathare Valley, Nairobi (click for a larger image) (c) Crispin Hughes/Panos Pictures

In the cities of the developing world, it is estimated that at least 50% of the urban population has little or no access to clean water and sanitation. Other public amenities are virtually unknown. Their homes are in the vast slums and squatter settlements that have become part of the urban explosion. Unwelcomed by city authorities struggling to provide even the basic services, they are living amidst squalor and dirt, often the first to be affected by natural disasters, pollution and disease.

The cities of the Less Economically Developed Countries (LEDCs) did not start to mushroom until the late twentieth century. Migration, population growth and industrialisation provided the catalysts that have led to the huge cities of today. The lure of 'streets paved with gold' continues to draw thousands of people from their rural centres, only to discover the harsh realities of hunger, crime, disease and death in the large slums or squatter camps.

Urban morphology

Expensive home for sale in exclusive district of Dhaka, Bangladesh (click for a larger image) (c) Zed Nelson/Panos Pictures

The shape of most developing world cities is irregular, with a small high-class sector usually situated near the central business centre (CBD) or on a prime site. The rest of the residential housing is less well-defined. Usually the largest zone is that of the ever-burgeoning shantytown development. Beginning close to the CBD, they have over the years spread outwards on the least desirable land. Often built upon wasteland or marsh, next to rubbish tips or sewerage disposal sites, their inhabitants build homes from whatever they can find. Gradually these temporary structures with more permanent dwellings. The industry of such urban areas is stretched out along the lines of communication from the CBD, and often followed the movement of people to the cities.

The numbers of poor people attracted to the cities of LEDCs continues to increase, bringing with it an increase in the severity and scale of the problems that city authorities have to face.

Clearly defined urban zones, Dhaka, Bangladesh (click for a larger image (c) Liba Taylor/Panos Pictures)

Housing
The rapid growth of cities has overtaken the provision of low cost housing, the result being the development of shantytowns and slum dwellings. At present, there are 100 million slum dwellers in the world's cities. Shantytowns grow up wherever there is space. Using anything that is available to provide shelter, these homes have no running water, sanitation, drainage or energy facilities. Often a number of people have to share one water tap and toilet. Open sewers run down the centres of the streets, carrying sewage that can pollute the water supply. With no rubbish collection, other waste lies in piles or heaps, scavenged by dogs and providing a natural breeding ground for diseases such as typhoid or cholera. Often overcrowded, extended families live together in appalling conditions.