The world's burgeoning cities are a critical fact of the 21st Century - and represent one of the greatest challenges to the future. By the year 2050 cities with populations over three million will more than double from 70 today to over 150. The authors in this book claim that contrary to conventional wisdom, that cities distort natural processes, just the opposite is true. Cities are far more than the sinks of energy, vast drains of natural resources, and obstacles to sustainable development. Properly managed, they claim, cities can be transformative arenas in which raw materials may be rationally and economically developed to support people decently, and whole regions sustainably. This volume provides new ideas for managing the mega-cities of our future. The editors' goal is to shape a new way of thinking about mega-cities - one that promotes their function in modern societies as engines of the ideas, technologies, and loci of political will needed to build a new regime of global sustainability.