Mending the Land: Spatial Analysis in U.S. Cities
By Hanna Monteith
Fragmentation of the landscape. Highways dividing habitats. Wetlands drying up. All results of human occupation spreading across the land.
In the United States, we have built our cities through urban sprawl and endless suburbs, cutting up the land that was stolen from Indigenous people into acres to be bought and developed. Early Euro-American colonists believed that all of “their” land needed a grander purpose, whether that be farming, livestock, or urban development. As the American population grew and urbanized, contiguous habitats became increasingly disconnected from one another. In order to bring back connectivity and let biodiversity flourish, humans need to patch the holes in the land they caused in their sprawl. How might humans weave themselves into the natural world to create a diverse, productive, and just habitat for all species?
The answer lies in both new and old ways of looking at, studying, and analyzing the land. Modern technologies such as GIS (Geographic Information Systems) as well as historical, handmade maps can illuminate how landscapes have been altered over time. Satellite imagery is important for understanding both the past and the present. Google Earth, for example, can produce timelapses displaying how land has shifted over time. In addition to maps, we can also learn about past landscapes through written or spoken accounts from history. It is crucial to consider all stories, not only those coming from colonial perspectives. When all these resources are combined, a bigger picture begins to materialize: the fragmented landscapes surrounding our modern cities. Two major historic cities of the United States that exemplify such fragmentation are Philadelphia and New York City. Using interdisciplinary methods to examine the past and present landscapes of these places can help us reimagine more sustainable cities of the future.
Spatial analysis is nothing new to city officials, planners, and lawmakers. This technology has long been utilized to complete tasks like finding correlations between different neighborhoods and crime rates or making simple suitability models for ideal restaurant locations. However, there is also a dark past to spatial analysis that still plays a role in the equity issues plaguing the United States. Redlining was practiced in most cities to fuel segregation, racism, and inequalities while benefiting institutions and the white elites. Started by the Home Owners Loan Corporation (HOLC), a government-sponsored corporation, in 1933, the goal of redlining was to map U.S. cities’ neighborhoods in terms of investment value, giving neighborhoods grades based on their worth. Neighborhoods in Philadelphia with populations comprised largely of immigrants or people of color, such as North and South Philadelphia, were graded D and highlighted in red, while neighborhoods such as Germantown that were predominantly white and wealthy were labeled as worthy of investment with a grade of A and highlighted in green. These letter grades have had a lasting impact on the neighborhoods and people the government labeled as less valuable. Using remote sensing and satellite imagery to right these wrongs and promote healthier cities is crucial to a sustainable America.
The different growth of neighborhoods in Philadelphia is the result of redlining, but it wasn’t set up to be that way when the blueprints of the city were first drawn. William Penn, the founder of Philadelphia, had a revolutionary plan for how his city would look in 1682. He envisioned a grid with no dark alleyways, where each quadrant of the grid had open green space. Each lot was evenly spaced with room for gardens, a plan that embodies what an ideal sustainable city might be. However, there was a flaw in this plan; William Penn didn’t consider, and probably couldn’t even fathom, the boom of urbanization and population density that would occur after World War II and the redlining of neighborhoods that ruined the symmetry of his city plan.
Switching to modern technologies that can analyze the growth of megacities like New York, a 2010s land cover map of the municipal area shows spatial analysts the urban growth the city has gone through by making this snapshot of the land cover. The map classifies different aspects of the land, the red pixels marking buildings while dark green represents tree canopy and light green represents grasslands. The two labs that made this map–the University of Vermont’s Spatial Analysis Laboratory and the New York City Urban Field Station–also identify the lines of roads and water bodies such as the pond in Central Park. Classifying land use in these types of maps helps scientists and city planners figure out where habitat fragmentation is most prominent. Central Park is a haven for wildlife and New Yorkers alike, but its non-human residents are trapped within its borders, especially those species that don’t have wings. Looking south on the map, you will see the strict divide between green and red which signifies the edge of downtown Manhattan. Seeing these boundaries from a bird’s eye view gives scientists perspective on where to focus the efforts of urban ecology work.
In both of these iconic American cities, a trend is occurring that could help restore the continuity of fragmented land and solve some injustices or make it worse. Vacancies, empty lots, and abandoned businesses are increasing in U.S. cities as more people are moving to suburban areas. The power that vacancies hold lies in whether cities dedicate the previously used land to benefit the community and environment or leave the slabs of concrete and unstable buildings untouched. If city planners use these spaces to the community's advantage, like building a community garden, more sustainable cities could be on the horizon.
Vacant lots are not just unrealized potential sites for community development. These lots are impervious surfaces: surfaces that can’t absorb stormwater and increase air temperatures. The urban heat island effect impacts many cities due to the way concrete and asphalt bounce the heat back up, making cities more susceptible to heat waves. Scientists use remote sensing to understand surface heat and overlay the data with tree canopy and census data. Trees, of course, provide shade and cool the air through the transpiration of water vapor. Adding the census data tells the same story of the trees, but paired with the harder truth of redlining’s continuations on people of color. Historically redlined neighborhoods are hotter due to the lack of greenery. Cities are making efforts to confront these issues with programs like Million Tree NYC, which plants and cares for the trees which provide many ecosystem services for the city. Still, there is a big disparity that persists in the redlined neighborhoods even as Million Tree NYC continues to plant trees.
The lack of trees and shrubs in the neighborhoods that were highlighted as red in 1933 has also caused another unbalance: loss of biodiversity. Species that need trees, shrubs, and gardens to survive like birds, insects, and small mammals don’t thrive in the redlined neighborhoods. The urban species gravitate towards the streets lined with trees and the green spaces with grass and food to eat. Many of these observations of this fragmentation of nature are clear when apps that map where civilians find species like iNaturalist and eBird come up with lower numbers of species in these redlined neighborhoods.
By layering maps displaying original redlining data with modern maps of vacancies and species dispersal, urban planners can begin to develop spaces that effectively mend currently disconnected landscapes. Understanding where inequities in biodiversity and social justice exist on spatial scales through land cover maps and community observations shines a light on where improvements need to be made, and is a critical tool as we strive to etch sustainability into the layout of our cities. H
Art by Liza Teleguine
