In particular, the challenge for Foster is Africa. Can he be the Bazalgette of an African future city? Africa's population will double to 2 billion before 2050. Its urban population will more than quadruple. There are unlikely to be enough jobs for young people to stave off populist unrest. Climate change is likely to jack up food prices and exacerbate water shortages. Africa has already lost much of its forest cover. It has the most degraded soils in the world.
I pressed him on the question of a new model of city for Africa, necessarily poor, without an industrial base, but youthful, vital, playful and verdant.The answer that Foster gave was inspirational, in my view:
What is needed in African slums", Foster ventures, "is the industrialisation of units that provide the sanitation, kitchens, energy-harvesting, run-off of rainwater, and a proper infrastructure of drains and sewers. That would be transformational, but that's a very different approach to the design-profession response to wipe it clean and superimpose another order, which completely disregards the fact that, notwithstanding the horrific deprivation, there is an underlying social order and an organic response to needs."Who would pay for this in cities whose governments don't really have the funds to get things going?
There is plenty of money to be made from squatters. Most of the economic growth in the world in the coming years will be from the poorest bits of cities in the poorest countries. Companies such as Coca-Cola and Unilever expect their profits from these communities to swell. Nokia will rise or fall according to whether slum-dwellers continue to buy its low-end phones. There is money in Foster's idea of laying down grids, especially for cities yet to be built. And there is reason to be optimistic about new technologies, such as solar-panel roof sheeting, affordable windows, LED lighting, gargantuan rainwater tanks, and high-tech latrines that pay for themselves by filtering urine into water and microwaving excrement into fuel. Africa's dense gatherings of young people present a high degree of political risk, but they also create economic value.This is the most positive set of ideas that I think I have ever seen about African cities, and makes me hope that there is hope.