Using GIS to Assess Urban Tree Canopy

The University of Vermont Spatial Analysis Lab used spatial analysis to map out how the city of Philadelphia’s tree canopy changed between 2008 and 2018. Urban tree canopy is defined as the layer of leaves, branches, and stems that provide many health and environmental benefits to residents.

Benefits of urban trees

Tree cover has been associated with many benefits such as reducing ambient temperatures (which, in turn, reduces energy needed for cooling buildings), removing carbon dioxide from the air, reducing rainfall runoff, absorbing pollutants, and providing social and mental health benefits. 

The USDA’s Urban Tree Canopy (UTC) Assessment protocols were used to analyze urban tree canopy in Philadelphia. These protocols were developed in 2006 for a study on urban tree canopy in Baltimore, Maryland. These protocols involve assessing land cover and tree canopy developed through data derived from aerial imagery, LiDAR, and other GIS datasets. The findings and a summary of the GIS analysis used have been presented in a report on the state of Philadelphia’s urban tree canopy.

By extracting data from LiDAR and aerial imagery, analysts were able to create high resolution land cover and tree canopy GIS datasets. From the report, “From a Church Street shade tree in Franklin Square to a core forest patch in Pennypack park, every tree in the city was accounted for.“

The study found that between 2008 and 2018, the city lost 6% of its tree canopy, a total of 1,095 acres. That’s equivalent to 1,000 football fields. Reasons for the canopy loss range from backyard clearings to tree removal due to construction.

The geospatial data extracted during the study was also use to identify vegetated areas that could potentially be planted in order to increase the tree canopy.

The Study

Tree Canopy Assessment ~ Philadelphia, PA

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