Study area
Philadelphia PA, USA is the sixth largest city in the United States with
a city population of 1.6 million inhabitants (U.S. Census Bureau, 2016)
and hosts an average population density of 30,297 inhabitants per square
kilometer. It is located at the confluence of the Delaware and
Schuylkill rivers on the eastern border of Pennsylvania with the
Appalachian Mountains to the west and the Atlantic Ocean to the east.
The city has a total area of about 370 km2 of which
350 km2 are land and the rest, water. Phildelphia is
one of the poorest cities in the US, with 26 percent of its population
living in poverty (PEW, 2017). Philadelphia is also one of the most
segregated cities in the US, with African American and Asian populations
concentrated in neighborhoods in West and North Philadelphia
respectively (The Brookings Institution, 2003). The city’s population
peaked in 1950 with over 2 million people, and was declining until 2010
when is started growing again. Recently, Philadelphia is experiencing
strong, yet uneven economic resurgence reflected in job growth and
rising housing prices (PEW, 2017).
Philadelphia’s urban structure emerged through the evolution of its
original plan, laid out by William Penn in 1643. It has a gridded layout
with mostly low and mid-rise residential buildings. A long time
“gentleman’s agreement” kept Penn’s statue on top of city hall as the
highest building in the city, preventing high-rise development for
decades until the 1980s. The most common residential structures in the
city are rowhouses. Rowhouses commonly occupy a narrow street frontage
and are attached to other homes on both sides (Simmons Schade et al.,
2008). Aside from the build environment, green space in the city
includes 19% tree cover and 24% grass-shrub cover that are distributed
unevenly across the city with some neighborhoods densely vegetated and
others with little to no green space (O’Neil-Dunne, 2011). Part of the
city’s sustainability plan, Greenworks Philadelphia, includes a goal of
tree canopy cover of 30% in all city neighborhoods by 2025 (City of
Philadelphia, 2015a). However, until recently, the only publicly
available data for a comprehensive analysis of the city’s green space
has been the National Landuse-Landcover (NLCD) datasets that do not have
the spatial resolution and functional categories required to identify
small and fragmented patches of landscape elements within the city. In
2011, a fine scale dataset of Philadelphia landcover was released (City
of Philadelphia, 2011) that is used here as the basis for the STURLA
classification system. Empirical evidence from two cities, Berlin and
New York City (NYC), were compared (Larondelle et al., 2014) and more
detailed analysis of within class and neighborhood effects were
performed in a Berlin case study (Kremer et al., 2018).