“Trees help clean our air, and reduce the pollutants that trigger asthma attacks and exacerbate other respiratory diseases. They cool our streets, sidewalks, and homes on hot summer days. Trees increase property value, and encourage neighborhood revitalization. And trees make our City an even more beautiful and comfortable place to live, work, and visit.”
http://www.milliontreesnyc.org/html/home/home.shtml