Planting for the Future
Seeking reforestation opportunities to reduce air pollution at Pittsburgh, PA
Air Pollution in the US
According to the 2021 State of the Air report by the American Lung Association (ALA), four out of ten U.S. residents—135 million people—live in counties with unhealthy levels of air pollution. Despite dramatic progress in cleaning the air since 1970, air pollution in the United States continues to harm people’s health and the environment.
Pittsburgh’s air quality is among the worst in the nation
Pittsburgh’s air got an F in ozone and particulate matter and ranked 9th worst in the country for long-term particle pollution. These factors are associated with heart and lung disease. In 2020, residents of the greater Pittsburgh region suffered through 57 days of bad air.
The biggest sources of air pollution in the Pittsburgh region are from cars, power plants upwind of Pittsburgh, and heavy industry, such as US Steel’s Clairton Coke Works in the Mon Valley.
Loss of Forests Intensifies Air Pollution
Trees remove gaseous air pollution primarily by uptake via leaf stomata, though some gases are removed by the plant surface. Pollution removal by urban trees in the United States has been estimated at 711,000 tonnes (t) per year.
Unfortunately, due to the growth of urban space, a lot of forests area is being cut and used for human development in Pittsburgh. The forest especially affected are closed to open canopy broadleaved deciduous tree cover and trees and shrubs in mosaic with herbaceous cover (as shown in the bar chart below). This means the city is losing its lung function and air pollution is intensified.
Left: Allegheny County Landcover 1992
Right: Allegheny County Landcover 2019
This map illustrates Allegheny county land that changed to urban areas from other types of land use between 1992 - 2019.
Land Change to Urban Areas 1992-2019
Reforestation to Reduce Air Pollution
Reforestation is one of the most effective ways to reduce air pollution. In addition, planting trees helps sequester carbon and mitigate the urban heat island effect. In 2021, the city of Pittsburgh was selected as one of four U.S. cities to receive a Reforestation Hub assessment. This means that Pittsburgh will work towards recovering some of its lost tree canopies.
According to Pittsburgh i-Tree Ecosystem Analysis, London planetree (Platanus x acerifolia) is one of Pittsburgh’s top-performing species and contributes the highest value in pollution removal.
Finding Suitable Sites
Using Southeast Pittsburgh as the study area, I modeled the process of finding suitable sites for reforestation, especially to plant London Planetree.
Allegheny County Landcover Change 1992-2019
Sites suitable to plant London planetree should be on average, medium to wet, well-drained soils in full sun (SE-SW aspect) on gentle slope area (< 15%) avoiding existing forest area. In addition, the sites should also locate in densely populated areas and close to the pollution source.
The following video details this process:
Related Reading
For more information about air pollution and reforestation, see the following resources: