College of Social and Behavioral Science
86 Shade, Urban Heat, and Public Transportation in Tucson, Arizona
Celeste Maybell and Timothy Collins
Faculty Mentor: Timothy Collins (Environmental & Sustainability Studies, University of Utah)
Description of Project
Existing environmental justice literature has found that urban heat island temperatures are higher in United States neighborhoods belonging to low income and racial/ethnic minority communities. It is also known that urban spaces utilizing vegetation shade tend to be cooler than spaces that rely on architectural or building shade. There is, however, relatively little research on urban heat and public transportation waiting areas and the types of shade used in these areas despite the fact that people from lower income and minority racial/ethnic neighborhoods tend to rely on public transportation more than those from more privileged neighborhoods. This research pairs data derived from the United States Geological Survey on land surface temperature (LST) with sociodemographic data from the United States Census Bureau’s American Community Survey and primary data gathered on bus stop shade environments in the City of Tucson, Arizona. Data from the American Community Survey for small areas (census tracts and block groups) and from the City of Tucson on bus stops will be used to characterize neighborhood social characteristics of bus stop locations, and those data will be paired with data on bus stop LST and shade to examine social inequalities in heat environments. It is predicted that LST will be higher and there will be less shade around bus stops serving neighborhoods with lower incomes and higher racial/ethnic minority composition in Tucson. Additionally, it is predicted that public transportation waiting areas in Tucson will utilize infrastructural shade more frequently than green shade. The results of this project will contribute to research on urban heat island effects and public transportation. Results may suggest a new approach to addressing urban heat island inequities in cities for their public transportation waiting areas and encourage public transportation usage as cities strive to reach sustainability goals.
Literature Review
Environmental justice literature has consistently found that that the effects of urban heat are disproportionately felt in low-income communities and communities predominantly composed of racial/ethnic minority groups (Renteria, 2022; Mitchell, & Chakraborty, 2014, Hsu et al., 2021). In the United States, heat is the leading cause of weather-related deaths; the frequency, duration, and intensity of heat events are expected to increase because of climate change (Nahlik et al., 2017;
Goodell, 2023). The U.S. southwest is particularly vulnerable to these changes as rising temperatures, arid conditions, and dust storms are met with an increasing population placing higher demands on energy production (Brazel, 2019; Santamouris, et al., 2015; Goodell, 2023; Nahlik et al., 2017; Tong et al., 2017). It is imperative for cities in the southwest to engage in cooling and sustainability initiatives to stave off the worst effects of these intense heat events. Using plant/vegetation shade and public transportation, especially in densely populated cities, are two well-regarded methods to achieve these goals (Park et al., 2021; Aram et al., 2019; Sinha, 2003; Gossling, 2016). Yet, the potential to transform waiting areas for public transportation into greenspaces, which would effectively help to mitigate urban heat islands and encourage sustainable transportation, remains largely unexplored. In Tucson, Arizona, there is a vegetation shade deficit as the entire city averages 6% tree canopy coverage with some neighborhoods achieving less than 2% coverage, which is a far cry from the American Forests recommendation of 15% for desert cities (Tucson Community Forest Action Plan, 2023). To address this deficit, the City of Tucson has initiated several programs—including Tucson Million Trees, Storm to Shade, and Urban Forestry—with the aim to achieve 15% tree canopy coverage in the city by 2030 with a stated preference to plant trees in the low-income and racial/ethnic minority neighborhoods that currently have the largest deficit (Tucson Community Forest Action Plan, 2023; Tucson Tree Equity Scores, n.d.). Tucson offers a variety of public transit systems including buses, streetcars, and shuttles; of these, the regional Sun Tran bus system is the most reliable, accessible, and extensive form of public transportation in Tucson with 33 regular fixed routes running week-long and 12 express commuter routes which operate from Monday-Friday (City of Tucson, Sun Tran Route Schedules, n.d.). During the COVID-19 pandemic, Sun Tran waived all fares for all public transportation services and has not yet reimplemented these fares (Birmingham, 2020; Sun Tran, n.d.). This has provided a valuable opportunity for equity in Tucson as, shown from a survey gathered pre-free fare policy, 54.1% of total riders identified as low-income earners and 54.52% of riders identified as being a racial/ethnic minority (Service Planning and Development Department, 2022). The City of Tucson implemented fare-equity policies which has contributed to transportation justice within the city, however, the lack of greenspaces in neighborhoods show that environmental justice is yet to be achieved.
References
Aram, F., García, E. H., Solgi, E. & Mansournia, S. (2019). Urban Green Space Cooling Effect in Cities. Heliyon, 5(4). https://doi.org/10.1016/j.heliyon.2019.e01339
Birmingham, P. (2020). In-Depth: Free rides on Sun Tran soon to end. KVOA: News4Tucson. https://www.kvoa.com/news/in-depth-free-rides-on-sun-tran-soon-to-end/article_68264025-2be4-5b88-bc08-4d4d49fb28f7.html
Brazel, A. (2019). June temperature trends in the southwest deserts of the USA (1950-2018) and implications for our urban areas. Atmosphere, 10(12), 800. https://doi.org/10.3390/ATMOS10120800
City of Tucson. (n.d.). Sun Tran Route Schedules [Brochure]. https://www.suntran.com/
City of Tucson. (n.d.). Tree Equity Scores for Tucson Neighborhoods. https://experience.arcgis.com/experience/ef686020e5bb483f9840aedb6dc43bbc/
City of Tucson. (2023). Tucson Community Forest Action Plan: Overview, First Edition. PDF available from https://climateaction.tucsonaz.gov/pages/milliontrees
Goodell, J. (2023). The Heat Will Kill You First: Life and Death on a Scorched Planet. New York, NY: Little, Brown and Company.
Gossling, S. (2016) Urban Transport Justice. Journal of Transport Geography, 54. http://dx.doi.org/10.1016/jtrangeo.2016.05.002
Hsu, A., Sheriff, G., Chakraborty, T., & Manya, D. (2021). Disproportionate Exposure to Urban Heat Island Intensity Across Major US Cities. Nature Communications, 12(1), 2721. Doi: 10.1038/s41467-021-22799-5
Mitchell, B. C., & Chakraborty, J. (2014). Urban Heat and Climate Justice: A Landscape of Thermal Inequity in Pinellas, Florida. The Geographical Review, 104(4).
Nahlik, M. J., Chester, M. V., Pincetl, S. S., Eisenman, D., Sivaraman, D., & English, P. (2017). Building Thermal Performance, Extreme Heat, and Climate Change. Journal of infrastructure systems, 23(3). https://doi.org/10.1061/(ASCE)IS.1943-555X.0000349
Park, J., Kim, J., Sohn, W., & Lee, D. (2021). Urban Cooling Factors: Do Small Greenspaces Outperform Building Shade in Mitigating Urban Heat Island Intensity? Urban Forestry & Urban Greening, 64, 127256. https://doi.org/10.1016/j.ufug.2021.127256
Renteria, R., Grineski, S., Collins, T., Flores, A., & Trego, S. (2022). Social disparities in neighborhood heat in the Northeast United States. Environmental Research, 203, 111805. https://doi.org/https://doi.org/10.1016/j.envres.2021.111805Santamouris, M., Cartlais, C., Synnefa, A., Kolokotsa, D. (2015). On the Impact of Urban Heat Island and Global Warming on the Power Demand and Electricity Consumption of Buildings – A Review. Energy and Buildings, 98, 119-124. https://doi.org/10.1016/j.enbuild.2014.09.052
Service Planning and Development Department, Sun Tran. (2022). Title VI – Fare Equity Analysis: Suspension of Fares. City of Tucson. https://www.suntran.com/wp-content/uploads/2024/02/Fare-Equity-Analysis-for-the-Suspension-of-Fares-August-2022.pdf
Sinha, K. C. (2003). Sustainability and Urban Public Transportation. Journal of Transportation Engineering, 129(4), 331-341.
Sun Tran. (n.d.) Fares & Passes. https://www.suntran.com/fares-passes/
Tong, D. Q., Wang, J. X. L., Gill, T. E., Lei, H., & Wang, B. (2017). Intensified dust storm activity and valley fever infection in the Southwestern United States. Geophysical Research Letters, 44(9), 4304-4312. https://doi.org/10.1002/2017GL073524