Article: Nyelele, C. & Kroll, C.N. 2020. The equity of urban forest ecosystem services and benefits in the Bronx, NY. Urban Forestry & Urban Greening 53, 126723. DOI: https://doi.org/10.1016/j.ufug.2020.126723
Urban trees provide many natural services, better known as “ecosystem services”, to city residents. For example, trees can reduce air pollution, regulate heat, store carbon (and in doing so help fight climate change), reduce stormwater runoff and nutrient pollution (by taking up water and nutrients through their roots), and improve human health. However, the distribution of trees in cities, and therefore of these benefits, can be unequal. This can occur, for example, when impoverished neighborhoods have fewer trees and therefore fewer ecosystem services and benefits (for more on how this unequal distribution can influence bird diversity, check out this other recent Envirobites post).
To address this environmental justice issue, it is important that we have good ways to quantify ecosystem services provided by urban trees, analyze how these services are distributed, and identify patterns that relate to characteristics of the residents.
In a new study, Drs. Charity Nyelele and Charles Kroll of SUNY College of Environmental Science and Forestry quantified the ecosystem services and financial benefits that trees provide to residents in the Bronx, New York. The researchers used i-Tree, a freely available suite of software produced by the USDA Forest Service and its partners, to quantify how well these trees stored carbon, reduced stormwater runoff, reduced air pollution, and reduced heat. Next, they translated these calculations into dollar values, estimating the monetary benefit to the neighborhood that these trees naturally provide through each of these services.
The researchers then used data from the U.S. Census to see how these services varied with different socio-demographic and socio-economic indicators. These characteristics were related to income of the residents, population density, education level of the residents, percentage of residents living in poverty, and percentage of residents of a minority race. Once the researchers had these values, they calculated the inequality in the distribution of ecosystem services provided by trees.
Unequal Access in the Bronx
All ecosystem services and benefits measured in this study were unequally distributed. Ruling out relationships due to natural differences in the landscape, the researchers found that disadvantaged socio-demographic and socio-economic blocks of the Bronx tended to have lower tree cover and, as a result, received fewer ecosystem services and benefits.
They researchers determined, for example, that for every additional $1,000 in annual median household income in a neighborhood, that neighborhood gained additional ecosystem services related to the trees that valued $140 in carbon storage, $40 in removal of air pollution, and $6 from preventing nutrient runoff. In addition to income, the reduction of ecosystem services was also related to an increase in population density. These differences add up, providing disadvantaged neighborhoods with limited services from the environment.
Drs. Nyelele and Kroll note that their work cannot provide reasons for unequal distribution for ecosystem services, but they offer a few possible explanations for differences in tree cover by neighborhood based on past studies. Households with high incomes are often more willing to pay for properties with landscaping and are better able to influence public investment in tree planting. Low-income neighborhoods tend to have more renters, who may be less inclined to invest in long-term tree planting initiatives. Residents in some disadvantaged neighborhoods may prefer fewer trees for safety reasons (i.e., reduced tree cover to improve visibility), meaning that increases in tree cover to increase ecosystem services should be sensitive to their concerns. All of these potential reasons and more warrant further investigation, but studies like this one are a good starting point for finding inequality and possible explanations.
What Can We Do?
It is clear that the distribution of ecosystem services in cities can be unequal and unfair, and understanding the interactions between the characteristics of residents in a neighborhood and access to ecosystem services is crucial, especially in city planning. Dr. Nyelele and Kroll’s method serves as a possible way for cities to determine how just their distribution of resources is, and to monitor this inequality over time.
Several cities have already started incorporating environmental justice ideas into their planning. New York City is one of them, having launched MillionTreesNYC, a tree-planting initiative that included two low-income, low-canopy neighborhoods in the Bronx. With more analyses of ecosystem services in our city to better understand and monitor the distribution among residents, more mindful city planning, and initiatives such as MillionTreesNYC, we can help improve access to ecosystem services for all city residents and make the distribution more fair.
If you are concerned about this issue, consider learning more about initiatives in your area to improve access to ecosystem services for everyone. Consider reaching out to your local government to let them know that this is of importance to you as well. And, as this study demonstrates an important use of Census data (in addition to another important and relevant use of Census data: determining the distribution of government resources to communities), consider filling out the Census, if you have not already done so.