Trees can do a lot for a city. From an environmental perspective, they improve air quality and also reduce temperatures, leading to lower energy consumption. From an economic one, they've been tied to increased property value, particularly in highly walkable neighborhoods. From a psychological view, urban trees even have an incredible restorative effect on our attention.
But cities aren't doing much for their trees in return. In fact, urban America is losing tree cover at a steady rate, according to a study published in the latest issue of the journal Urban Forestry & Urban Greening. Using aerial photographs to compare changes over time in 20 major U.S. cities, researchers David Nowak and Eric Greenfield of the U.S.D.A. Forest Service found that tree coverage is on the decline, while impervious cover — roads, buildings, sidewalks, and the like — is on the rise: