A recent study published in Nature Communications found that Black, Indigenous, and People of Color (BIPOC) are disproportionately in census tracts with higher heat island intensity. Heat islands are defined as areas that experience higher temperatures than the surrounding areas. This is often in urbanized areas with large infrastructure, like buildings and roads, that lead to an increased sunlight intensity. In contrast, areas that are more suburban or rural have more green space, which helps with cooling temperatures.
Bloomberg’s CityLab reported that access to green space in cities is directly related to income and higher education, both of which are, in turn, associated with an increase in green space. The Nature Communications study found that in 169 of the 175 urban areas analyzed disparities in heat island effects were dependent on race. A higher exposure to heat leads to drastic health outcome, which already disproportionately impact marginalized communities. Heat impacts pre-existing conditions, like heart and lung disease, diabetes, and asthma.
In the hottest parts of Boston and its adjacent cities (Chelsea, Everett, and Somerville), daily temperatures can be 20 to 50 degrees hotter than nearby suburban areas that have more tree and vegetation coverage—like Melrose, Arlington, Newton, and Brookline. Building colors and types of infrastructure also play a major role in the heat island effect: dense urban areas with an aging housing stock and multi-story buildings, often made of brick and stone, retain heat collected throughout the day. While replacing asphalt with rubberized surfaces on children’s playgrounds is beneficial in preventing injury, black or dark blue playground surfaces can heat up to about 96 degrees on a sunny day in the mid-70s. While some cities are investing in long-term cooling plans, there are some setbacks. For instance, the City of Chelsea planted 2,000 trees between 2013 and 2017, but roughly 30 percent of the trees died within a year of planting. This is partially due to methane gas distribution system leaks nearby the affected trees.
Urban heat islands are often a result of racist systemic practices, such as redlining (where neighborhoods and communities are denied services as a result of racially discriminatory practices) and underfunding of marginalized communities. A study in the journal Climate found that 94 percent of the cities studied had higher land-surface temperatures in formerly redlined areas compared to non-redlined areas. To this day, Boston is still quite segregated, and like other cities in the United States, urban heat islands are strongly correlated with public disinvestment and systemic racism.
Sagal
Alisalad
Research Assistant
Myisha Majumder
Research Assistant
This is a part of the AEC Blog series