This innovative book sees contemporary urban settlement as the new human ecosystems defining people's lives across the planet. Just as so-called natural ecosystems have defined our view of the symbiosis between humans and their environments, James H. Spencer argues that it is an urban ecosystem found across the planet that defines the twenty-first century. Using the globally diverse cases of Ho Chi Minh City, Addis Ababa, Honolulu, and New York, the book draws out the commonalities in how our intertwined built and social environments express a shared humanity across continents and cultures.