The social, environmental, and economic benefits of green infrastructure in Washington, DC

Matthew L. Richardson and Mamatha Hanumappa, University of the District of Columbia, Peter Aniello, Lara Miller, Brendan Shane and Taj Schottland, The Trust for Public Land, John R. Taylor, Plant Sciences and Entomology, University of Rhode Island, Kingston, RI

Background/Question/Methods
The world’s population continues to grow and urbanize, and people are increasingly disconnected from green spaces, nature, and their food system, creating health, social, and environmental problems. Coupled with these challenges, climate change is increasing global temperatures and extreme precipitation events, the effects of which are exacerbated in urban areas by the heat island effect and sealed surfaces. Within a single city, people who are undereducated, poor, in a minority racial or ethnic group, and/or immigrants are disproportionately affected by climate change, a degraded environment, environmental hazards, and food access. Properly sited multifunctional green infrastructure (GI) within cities can help address these urban challenges and offer myriad economic, environmental, and social benefits. We analyzed secondary geospatial data to determine the extent of existing GI and the potential for new multifunctional GI in the District of Columbia on roofs and at ground level. We then estimated actual and potential levels of carbon storage, carbon sequestration, stormwater and air pollution management, and energy/financial saving on private and public land.
Results/Conclusions
The District has a total area of 17,711 ha, of which 246 ha currently supports GI, but an additional 3,172 ha are potentially suitable for GI. The existing and potential space occurs mostly on private land. Wards 7 and 8, which are largely food deserts and whose residents are primarily African American and experience the greatest inequities, have the largest area suitable for urban agriculture. Increasing tree canopy by 17.4% by 2050 would increase carbon storage by 18.3%. Annually, it would also increase carbon sequestration by 14.8%, avoid an additional 19% of stormwater runoff, remove 14.5% more air pollution, and save an additional 220% of energy. The financial benefit from carbon storage would be $20.21 million and savings from carbon sequestration, stormwater and air pollution management, and energy and fuel reduction would be $9.44 million annually. With respect to heat, approximately 476,000 people are exposed to extreme urban heat, including more than 60% of residents in Wards 1, 5, 6, 7, and 8. Our work can clearly inform planners and policymakers on the benefits of GI and the need to implement it in a more equitable way across a city.