With rapid urbanization overtaking the world, experts worry that planners and architects are too few and lack experience to tackle the coming challenge.
"This summer, the number of people living in cities exceeded the number living in rural areas for the first time. Of the planet's six billion people, three billion live in cities, of whom one billion live in urban slums. Twenty years from now, the total global population is forecast to increase to eight billion, of whom five billion will be living in cities, two billion of them in slums.
As the demands on the world's planners grow, academics from around the world gathered at a recent conference and expressed great unease about their ability to prepare the next generation of architects to build for this urban future.
"Every year the urban population increases by 80 million, equivalent to the population of Germany," said Lars Reutersward, an architect and director of the global division at UN Habitat, the United Nations department that looks at urban development.
"Within that there will be an increase in slum dwellers the size of Holland and Belgium put together - 35 million - every year. This is a complete disaster, and it doesn't have to happen," he added.
"People are dying in slums every day. It is horrible. We are lacking a sense of urgency; we are not coping with the speed of it."
The United Nations estimates that only 5 percent of the building work under way in the world's expanding cities is actually planned; in many Asian cities, 70 percent of residents are thought to be living in unplanned areas. These are usually the poorest inhabitants, who find themselves in badly built urban sprawls, with poor access to electricity, water and drainage.
In many parts of the world, the problem is worsened by a shortage of competent professionals. There is a stark disconnect between where architects are being trained and where the challenges lie.
"Seventy percent of architects come from the developed world but 70 percent of the work is in the developing word. There is a total mismatch," said Gaétan Siew, president of the International Union of Architects, at the conference on issues of urbanization organized by the Rockefeller Foundation in Italy last month.
"These architects are trained to work in their own country, not in the developing world. There is mobility of architects, but with mobility you can get inappropriate solutions."
The entire continent of Africa has 35,000 trained architects, of whom 25,000 are in Egypt. "Italy alone has three times this number," Siew said. "You can see the magnitude of the problem.""