D.C.’s Trees Prevent Over 270 Million Gallons of Stormwater Runoff

By Kayla Benjamin

When heavy rains hit the District, the stormwater often sweeps through the city. It can cause flooding in residential and commercial areas while also picking up grime from the pavement that ends up as pollution in our rivers. 

One of the city’s most vital defenses against the flow of water might just be standing in your yard or along your street. Urban trees soak up 276 million gallons of stormwater runoff annually in D.C., according to a Climate Central report released May 3. 

Trees’ ability to absorb water will become even more important as climate change causes the D.C. region to experience increasingly common and severe heavy rainfall events. 

“As we are seeing more and more historic storms happen more frequently, and we are looking for more ways to become resilient, trees have just continuously showed up as this natural solution,” said Beattra Wilson, assistant director of the Urban and Community Forestry program at the U.S. Department of Agriculture. 

The Climate Central report, titled “The Power of Urban Trees,” lays out the numbers showing just how effective that solution really is. In addition to analyzing the amount of stormwater runoff trees absorbed in 242 different U.S. metropolitan areas, the report looked at how much air pollution trees prevent and how many tons of carbon pollution—which causes climate change—they remove from the air. 

Trees Keep Us Healthier in the Face of Climate Change

Over 2 million trees grow in the District. They absorb about a million tons of air pollution every year, according to the new report. That includes several pollutants that have proven harmful to peoples’ health, like fine particulate matter and ground-level ozone. 

In addition to reducing air pollution, trees contribute to public health in cities by keeping neighborhoods cooler. They help reduce the “urban heat island effect,” which causes places covered in pavement and other human-made materials to get significantly hotter than surrounding areas. 

Even within a city’s boundaries, neighborhoods with less vegetation and green space experience higher temperatures than leafier neighborhoods. Because of the racist legacy of redlining, historically Black neighborhoods in the District and nationally tend to experience much hotter temperatures than wealthier, whiter areas. 

Climate change will cause hotter summers with more frequent heat waves. The health impacts of those high temperatures—such as heat strokes, which can be deadly—disproportionately impact vulnerable populations. 

Wilson said that rising global temperatures should make planting and maintaining urban trees in minority and low-income neighborhoods a high priority. 

“When it comes to heat conditions, as we know with the climate changing, these communities are only getting hotter,” she said. “So there is a sense of urgency.”

The federal government dedicated $1.5 billion for urban and community forestry in the Inflation Reduction Act last year. That funding was part of the law’s wider efforts to invest in promoting environmental justice and reducing climate change. 

Urban trees help cities cope with the impacts of climate change, such as high temperatures and increased rainfall, and they also help prevent climate change to begin with. The Climate Central analysis reported that D.C.’s trees take in about 40,000 tons of carbon dioxide annually, preventing those emissions from entering the atmosphere, where they would contribute to climate change. 

Data About Your Neighborhoods Trees Is Public and Easy to Access

To inform its report, Climate Central used a public database created by the USDA Forest Service. Unlike a lot of environmental information collected by the federal government, data about trees and their benefits is available to the public and easily accessible. A suite of digital tools called i-Tree pulls tree inventories, local air pollution and meteorological data into searchable, easy to use format. 

That’s important because it enables local residents, advocates and organizations to learn where trees are missing in the city and push for equitable tree plantings. 

“It’s a longstanding tool to deliver the best science,” Wilson said. “All of these benefits, the calculations, the methodologies behind the curtain, come through in this tool. We’ve seen many modernized applications like mobile friendly apps. And that’s amazing, because it brings equity, and it puts advocacy in the hands of any American and homeowner and resident.”

This post was originally published on The Washington Informer.