By Joe Duckworth, American Forests

Tempe, Ariz
Tempe, Ariz. Credit: Sarina via Flickr.

When most people think of forests, they probably think of massive expanses of trees in national forests and parks. It’s safe to say that they don’t think of deserts in the American Southwest. But, as this region grows and more people move into its cities, the need for urban forests in metropolitan areas, like Phoenix, Tucson and Albuquerque, increases.

The benefits that urban forests provide are well documented. They improve air quality, make city streets safer and lower the temperature of cities — all the more important in places where the temperature routinely rises to more than 100 degrees in the summer. Cities are often hotter than the surrounding environment due to the urban heat island effect, which, in turn, causes higher rates of energy use for air conditioning. This phenomenon is caused by materials such as concrete, buildings and asphalt reflecting the sun’s heat. A robust urban forest helps to mitigate the higher temperatures by providing shade and increasing the amount of water that evaporates from soil and leaves.

The scientific knowledge about how trees can reduce this effect has primarily been associated with cities in traditionally forested environments, such as the Northeastern U.S. In the desert, different strategies may produce better results for the ecosystem. American Forests is, therefore, working with the City of Tempe, Ariz., and Arizona State University to create “cooling zones” in public space that help reduce the urban heat island effect and make Tempe a more walkable and bikeable community, even in the heat of the summer.

Being in a desert, there are different challenges to face, including determining the most effective species for an arid environment. American Forests is excited to find ways to help desert communities benefit from trees and to promote the benefits of a well-managed urban forest. With the lessons learned from our work in Tempe, we will be able to assess the impact similar work could have in cities and towns across the southwest.