Why do trees matter so much in cities anyway? Because trees offer innumerable economic, environmental, and social benefits.
Trees reduce the costs associated with sustaining urban neighbor-hoods. Our work on GreenPlan Philadelphia included a cost/benefit analysis of trees using two different square-mile sample areas in Philadelphia. Cost data included planting and maintenance costs for trees and benefit data included savings on energy consumption and maintenance, stormwater capture, carbon sequestration and pollution mitigation. Each area was found to have a net annual benefit of over $1 million—just from trees providing 30% tree cover! As the benefits of carbon sequestration become monetized and more highly valued, the market value of trees’ benefits will increase significantly.
What are other benefits of trees? Trees absorb carbon dioxide through carbon sequestration and remove gaseous and particulate pollution, improving air quality. Shade trees lower air temperatures, reducing building energy use and the heat island effect. A recent study of Philadelphia showed that ambient temperatures of surfaces like parking lots are about 8°F warmer than surfaces like shaded parks. A study in New York City found street trees to be the most effective heat island mitigation strategy, more so than reflective roofs or new parks. Moreover, the presence of trees in urban neighborhoods has been found to improve mental health and social cohesion. Given all these areas of benefits, trees are a backbone of sustainable cities, contributing to economic, environmental, and social health!
