Nineteenth-century landscape architect Frederick Law Olmsted described his most famous project, the design of New York's Central Park, as "a democratic development of highest significance." Over the years, the significance of green in civic life has grown. In twenty-first-century America, not only open space but also other issues of sustainability--such as potable water and carbon footprints--have become crucial elements in the quality of life in the city and surrounding environment. Confronted by a U.S. population that is more than 70 percent urban, growing concern about global warming,...