The 21st Century has been described as the century of the cities. For the first time in history, more people live in cities today than those that do not. To say that cities are growing is to state the obvious- one can see it from our own windows. However the rate of growth is frightening. Fifty years ago, about 30% of the world�€™s population lived in an urban environment. In a decade from now it will cross 60%.

At present there are about 440 cities with a population of more than one million people. However, many of these are more than cities. Indeed a special name has been coined for them- Megacities. Megacities are defined as cities that have over a 10 million or residents. In 1950, there were 4 megacities worldwide. By 1980, this number had increased to 28, by 2002 to 39. It is estimated that by 2015 there will be more than 59 megacities. Most of these are and will be in the developing world.

Large scale migration within countries, bringing people from rural areas to urban centres with greater economic options, has been the chief forces leading to the growth of megacities. Chinese government figures indicate that at least 210 million rural labourers have migrated to urban areas in 2006. In the first six months of 2007, the number of migrant workers increased by 8.6 million, a year-on-year growth of 8.1 percent. The phenomenon has been described as the biggest internal migration in the history of the world. As China's urban centres boom they are gobbling up farmland at a voracious rate. A total of 16 million acres (6,475,000 hectares) have gone in the last 20 years creating a vicious cycle that fuels the growth of megacities.

The vicious cycle is further reinforced by push factors such as unemployment in rural areas, low agricultural productivity, lack of educational facilities and opportunities. The economic possibilities, attractive job prospects in cities act as pull factors. But how long can this growth go on? In megacities worldwide, we see infrastructure and basic utilities stretched to the breaking point- roads, electricity and water are the prime sufferers. A common sight that binds megacities of the world are poor quality housing for new migrants (slums in India, China, the Philippines, South Africa and Brazil), protests from the �€œoriginal residents�€ to the growing numbers entering their cities on a daily basis and never ending traffic jams.

The most dangerous trend in the manner that our megacities are growing is the increasing gap between the rich and the poor. In most cities, the five star hotels are a mere stone throw away from the squalid living areas of large numbers of people. If this disparity continues to grow, it will not be long before the rising discontent in the overpopulated slums will cause a real threat to the people living in ivory towers.

The biggest challenge that faces our urban policy makers and planners is to manage the development of our cities in a sustainable way, and to incorporate into their planning the aspirations of the majority of the population- which in some cities doubles every 10 to 15 years. It is debatable whether technological fixes like wind turbines, new types of mass transit systems, rooftop panels for solar energy and new materials for the building industry will be able to deal with the challenges that growing megacities will throw up in the future. The only way to deal with the challenges of our cities is to stop the migration into them by creating opportunities in the rural areas �€“a real prosperity in the periphery- creating an incentive for the rural people to live in dignity in their own homes. If this does not happen, we will have to seriously look at shifting to another planet.