Pittsburgh is one of four cities chosen as a Reforestation Hub to help our urban trees In 2014, National Geographic analyzed American cities’ urban tree cover — and found that Pittsburgh came out on top, with 42% tree cover. This “expanded urban forest removes 532 tons of air pollution every year,” noted the study. Since then, the City of Pittsburgh has dropped to an estimated 41% tree cover, due to pests, invasive species like the emerald ash borer, disease, and lack of maintenance. American cities as a whole lose an average of 36 million trees a year. Now the good news: Pittsburgh has been selected by Cambium Carbon and the Arbor Day Foundation as one of four cities to become a “Reforestation Hub.” The group will work with the Department of Public Works’ Forestry Division.