Breaking up Boston’s heat islands

Greenspace should be included in all new development

A PLACE to climb. An anchor for a tire swing. A home for wildlife. A source of shade on a hot summer day.

Trees hold many meanings. For families, a tree may be a timekeeper. A tree in a backyard may hold memories of children playing, robins nesting, and family gatherings. A tree standing tall over the years can serve as a connector between the past, present, and future. And for a community, trees are valuable. The presence of lush, green, and abundant trees in a neighborhood impacts not only aesthetics, but also property values and the overall health of the community and surrounding environment.

In several of Boston’s lower-income neighborhoods, a lack of greenspace coupled with an abundance of concrete, steel, and buildings produces “heat islands” where summertime temperatures rise up to 7 degrees higher than the city’s average. These temperature disparities are especially dangerous as Boston continues to experience record-high temperatures this summer.

Prolonged periods of extreme temperatures correlate with increases in heat-related illness and death. The elderly, the very young, and those with chronic illness are the most vulnerable to heat-related illness. According to the CDC, “[u]rban heat islands, combined with an aging population and increased urbanization, are projected to increase the vulnerability of urban populations to heat-related health impacts in the future.”

As explained by the Environmental Protection Agency, the urban heat island effect occurs when “structures such as buildings, roads, and other infrastructure absorb and re-emit the sun’s heat more than natural landscapes such as forests and water bodies.” Densely-populated cities in humid regions along the East Coast, like Boston, are especially susceptible to greater temperature disparities.

There are, however, strategies that can be used to mitigate the heat island effect. The EPA reports that “[i]ncreasing tree and vegetation cover lowers surface and air temperatures by providing shade and cooling through evapotranspiration. Shade alone can reduce surface temperatures by up to 45 degrees, and evapotranspiration, used with or without shade can cool off air temperatures by 2-9 degrees.” The use of garden roofs, cool roofs, cool pavements, and “smart growth” practices can also help reduce heat islands.

In Boston, the detrimental effects of heat islands aren’t spread across communities equally. Lower-income communities of color are among those especially impacted by heat islands. The Boston neighborhoods that historically were redlined are among those experiencing some of the hottest temperatures today. Residents of lower-income areas are less likely to have access to air conditioning to escape the effects of extreme heat. And for those who have air conditioning, the financial burden is ever-increasing as temperatures rise.

The city reports that extreme heat “impacts our systems and day-to-day needs” in the form of “more frequent power failures,” “reduced air and water quality,” “increased medical emergencies,” “tree canopy and green space loss,” and “slow or disrupted transportation infrastructure.” High temperatures are also linked to decreased productivity and increased absences at work and school.

To work towards reducing Boston’s heat islands, the city has initiated a Heat Resilience Study that focuses on the five neighborhoods that experience the greatest temperature disparities. These focus areas are Roxbury, Chinatown, East Boston, Mattapan, and Dorchester, which can all experience summertime temperatures 2-6 degrees higher than Boston’s average. Chinatown, in particular, is the hottest neighborhood due to dense development with limited trees and greenspace. As part of its study, the city is accepting input from members of these affected communities on their heat experiences and cooling recommendations.

Although the city is working towards solutions, private sector strategies are critical to minimize and eliminate Boston’s heat islands. Large housing complexes that are sprouting up in historically working-class communities of color contribute to the creation of heat islands. In East Boston alone, 15 new residential complexes are under construction, and three more are under review by the Boston Planning & Development Agency. A similar number of projects are underway in Roxbury and Dorchester. The city has taken some steps towards managing Boston’s heat islands, but it can do more to foster environmentally-conscious construction.

To be sure, the Boston Planning and Development Agency currently requires projects to submit site design plans which detail the building siting and use of non-built space. Larger projects are also required to submit a “climate resiliency checklist” focusing on a wide-range of building and site performance measures, including energy use. But the primary focus is on the building itself, leaving the use of the surrounding land largely discretionary.

To aggressively combat the heat island effect and to improve the health of our communities, more rigorous requirements should be incorporated into the review and approvals process for projects of all scales, rather than larger projects alone.

Successful models are readily available. For example, Seattle created the “Seattle Green Factor,” which requires that certain new developments meet a landscaping “score” given by the property’s zoning requirements. Seattle offers “a ‘menu’ of landscape credits for various features, including green roofs, rain gardens, vegetated walls, and trees, and shrubs.” The Seattle Green Factor was created, in part, to help keep neighborhoods cool.

Similarly, in Portland, Oregon, zoning requirements in certain areas mandate that new buildings install ecoroofs to help mitigate urban heat islands, improve air quality, and increase urban greenspace. These models demonstrate that development can go hand-in-hand with more greenspace — and more trees. Boston needs to join Seattle and Portland and become a leader on this front.

Building on the Boston Planning and Development Agency’s  existing mechanisms, all new construction — including projects of all scales — should be required to produce a more meaningful and robust greenspace plan as part of the permitting and approvals process. Standards must be strengthened and likened to affordable housing unit requirements.  Ideally, these standards will result in more projects dedicating a percentage of the parcel to greenspace; planting trees; relying on on-site generated solar or wind power; using green roofs or light-colored roofs; avoiding dark asphalt; reducing reflectivity and glare, and promoting community gardens. Each of these interventions should be incentivized.

Meet the Author

Ivan Espinoza-Madrigal

Executive director, Lawyers for Civil Rights Boston
Meet the Author

Lauren Sampson

Race & climate justice project attorney, Lawyers for Civil Rights
Meet the Author

Haley Harris

Legal intern, Lawyers for Civil Rights
To tackle the issue of heat islands, we must all work together towards solutions. The problem of climate change demands bold, innovative solutions, and we challenge the city to break up heat islands and to “green” our communities so Boston can be more livable for all.

Iván Espinoza-Madrigal is the executive director, Lauren Sampson is a staff attorney who spearheads the Race and Climate Justice Project , and Haley Harris is an intern at Lawyers for Civil Rights.