The future of the city is a fundamental concern at WorldChanging, and is a topic we return to regularly, and for good reason: the planet as a whole is on the verge of becoming a majority-urbanized world. The question of the city's future takes two primary forms: How can the cities in the developed world become centers of sustainability, reducing the citizens' environmental footprint with smarter transit, energy and resource options? At the same time, how can the rapidly-growing cities of the developing world become both sources of sustainable economic growth and engines for ethical, democratic development? Alex's Urban Sustainability, Mega-city Leapfrogging brings these issues into focus, and shows how they are tightly linked.

Ninety percent of population growth by 2030 is expected to concentrate in cities. The megacities of Asia, Africa, the Mideast and Latin America are expected to swell by almost another two billion people. That translates to over four billion developing world megacity-dwellers, the equivalent of building another Los Angeles every three months for the next 25 years.

...Redistributing the future to create bright green urban prosperity is a job of mind-bending complexity. It can only be done through innovation and collaboration of a scale and speed never seen before.