Half of the world's 6-billion people now live in cities and more will join them in the next two decades, putting pressure on governments to make urban areas more livable, according to a report released Friday.
Though most of this increase will occur in the world's poorer countries, industrialized nations will not escape the pressures of urbanization, the Population Institute said. Even in wealthier countries, more and more educated people will move from rural areas to cities in search of better opportunities.
"By 2050, an estimated two-thirds of the world's population will live in urban areas, imposing even more pressure on the space infrastructure and resources of cities, leading to social disintegration and horrific urban poverty," said Werner Fornos, president of the Washington-based institute, and an expert on population.
In 1900, the world's most populous cities were all in North America or Europe, the 18-page report said. At the end of the century, Tokyo, New York and Los Angeles were the only industrialized cities on the top 10 list.
"By 2020, New York and Los Angeles no longer will be included in the Top 10 _ pushed off by Dhaka, Bangladesh; Karachi, Pakistan; and Jakarta, Indonesia," the report said.
"And the only industrialized city among them, Tokyo, is projected to be replaced by Bombay, India, as the world's most populous city."
While the main attraction of cities is opportunity, their rapid growth leads to pressures on infrastructures, manifested in sanitary, health and crime problems, the report said.
Unskilled people arriving from rural areas frequently end up performing menial jobs at low wages or resorting to begging and stealing.
In addition, an estimated 25 to 30 percent of the world's urban population lives in inadequate housing, squatter settlements or in the streets where they lack sanitation, waste disposal and running water.
"City slums are breeding grounds not only for waterborne diseases such as diarrhea, typhoid and gastroenteritis, but sexually transmitted diseases including HIV/AIDS," the report said.
To combat growing urbanization in developing countries, their governments must establish programs to dissuade rural inhabitants from migrating to cities by improving infrastructure in the villages and encouraging industries to local in rural areas and provide jobs, it said.
Industrialized countries can help by increasing aid they provide to poorer countries to help them ward off "the devastating problems associated with urbanization."
The institute is an independent non-profit organization dedicated to achieving a more equitable balance between the world's population and environment resources.