Book excerpt: This study demonstrates the value of urban green. Focusing specifically on the role of vegetation and trees, the book shows the costs and benefits reaped from urban open spaces, from cooler temperatures to better quality ground water - and why it all matters. While a work of science, the book does not ignore the social component: it looks at low-income areas that have poor vegetation, and shows how enhancing these areas through the planting of community gardens and trees can alleviate social ills.