It is now universally accepted that the Third World urban population will double by 2020, and cities are projected to triple in area. To be more dramatic, all of the urban housing of the past 6,000 years needs to be built again, but this time in only 20 years! And now the issues of environment and climate add to the challenges.

Data shows that 30% to 70% of housing in Third World cities is built informally, illegally, often in high-risk areas and without an understanding of basic construction knowledge. Do they dictate city development and form?

How will architects and planners as the spatial professionals participate in these challenges?