Worldwide urban populations are expected to double within 10 to 15 years, presenting threats and opportunities, city planners said at the Planning Africa conference on Monday.

Urban planners from 26 commonwealth countries met in Sandton to debate three global challenges facing all cities -- urbanisation, poverty and climate change.

A developed country's urban population stabilises at around 80 percent of its national population, president of the Commonwealth Association of Planners, Christine Blatt, said.

If this trend was true for Africa this would require 43 cities the size of New York to house urban populations, she said.

Planning has a huge impact on societies and must be an integrated developmental tool for all government institutions, said Lecheta Tsenoly, chair of the parliamentary portfolio committee on provincial
and local government.

Ebrahim Fakir, researcher for Centre for Policy Studies, said that planning must differentiate between the particular needs and universal needs of people.

Planning was be cognisant of state needs and market needs and must be engaged within a society, he said. "Such engagement are the hallmarks of social capital."