In many poor countries, overpopulated slums exhibit high rates of disease due to unsanitary conditions, malnutrition, and lack of basic health care.
Many countries in the developing world neither have the legal nor the financial capacity to deal with the rapid growth of megacities.
Approximately one-sixth of today's world's population now live in shanty towns, which are seen as "breeding grounds" for social problems such as crime, drug addiction, alcoholism, poverty and unemployment.
The process of urbanisation presents enormous challenges to governments, social and environmental planners, architects, engineers and the inhabitants of the megacities. Just one example: The London population grew from one million to eight million people in 150 years, while the population of Mexico City grew from one million to over 15 million people in only 50 years.
No wonder, that the increasing number of people living in cities creates demand, in areas such as housing and services. The destruction of our environment and poverty are two other concerns, which city administrations have to take care of, as especially the poor do not have the necessary financial background to tackle these problems.
In 1800 only 3% of the world's population lived in cities. By the end of the 20th century, 47% did so. In 1950, there were 83 cities with populations exceeding one million; but by 2007, this had risen to 468 settlements of more than one million people. If the trend continues, the numbers of people who live in cities with at least 500.000 inhabitants, will double every 38 years, researchers estimate.
According to calculations of the United Nations, today's urban population of 3.3 billion will rise to nearly 5 billion by 2030, when three out of five people will live in cities and more than 2 billion people will be living in slums. The increase in the number of megacities causes huge problems, especially in Africa and Asia. Scientists reckon that until 2030 urban growth will mostly take place in developing countries. As a consequence, housing conditions are often very poor.
By 2007, e.g. 90% of the urban population of Ethiopia, Malawi and Uganda, three of the world's most rural countries, already lived in slums.
Although most of the world's megacities are located in the developing world, there are three major reasons why the developed world should clearly pay attention to them. First, because what happens there affects the rest of the world. Secondly, megacities are key instruments of social and economic development. Thirdly, they offer new market opportunities to both the developing and developed world.
Not always, but in a number of cases, a megacity is also the capital of a country or province.
Megacities influence a variety of living conditions for citizens. Although traffic jams, poor air quality and increasing health risks make life in megacities more difficult, people continue to choose to live there. Therefore it is essential, that more government programs are implemented in order to help improve living conditions for the inhabitants of metropolitan areas.
Megacities also offer great chances: according to the OECD Mexiko Cityand São Paulo produce around 50% of the income of their countries. Bangkok contributes more than 40% to the GDP, although it is home only to 10% of the population of Thailand.
We should take measures to reduce crime.