Once considered the antithesis of a verdant and vibrant ecosystem, cities are now being hailed as highly efficient and complex social ecological systems. Emerging from the streets of the post-industrial city are well-tended community gardens, rooftop farms and other viable habitats capable of supporting native flora and fauna. At the forefront of this transformation are the citizens living in the cities themselves. As people around the world increasingly relocate to urban areas, this book discusses how they engage in urban stewardship and what civic participation in the environment means for democracy. Drawing on data collected through a two-year study of volunteer stewards who planted trees as part of the MillionTreesNYC initiative in the United States, this book examines how projects like this can make a difference to the social fabric of a city. It analyses quantitative survey data along with qualitative interview data that enables the volunteers to share their personal stories and motivations for participating, revealing the strong link between environmental stewardship and civic engagement. As city governments in developed countries are investing more and more in green infrastructure campaigns to change the urban landscape, this book sheds light on the social importance of these initiatives and shows how individuals' efforts to reshape their cities serve to strengthen democracy. It draws out lessons that are highly applicable to global cities and policies on sustainability and civic engagement.