Trees Play a Key Role in a Sustainable Urban Future
Though trees aren’t usually the first thing that comes to mind when thinking about city living, urban forests are integral to ensuring and enhancing the quality of life in densely populated areas. Trees and green spaces provide a range of environmental and social benefits that can address some of the most persistent issues facing our cities today, from health and well-being, to social and economic indicators and equity, to resilience and climate change. Indeed, with more than two-thirds of the world’s population projected to be living in urban environments by 2050, the future of urban forestry and the future of the very livability of our cities are inextricably intertwined. What’s more, innovative projects and organizations in cities across the country can show the way to other communities looking to harness the power of trees for a more sustainable future.
What Trees Bring to Cities
While it’s fairly intuitive that trees are a positive, concerns about maintenance costs and other considerations can sometimes counter the notion in people’s mind that “trees are good.” Fortunately, there is plenty of strong evidence to support a significant investment in trees for a variety of reasons.
Improving Health and Well-Being
Urban trees remove over 710,000 tons of air pollution per year in the U.S., which has a major impact on fighting respiratory illnesses like asthma. Trees also filter up to 80% of phosphorus out of stormwater before it pollutes waterways and drinking water. And tree canopy shade, along with evapotranspiration (the return of water vapor from trees and vegetation back to the atmosphere), can lower peak temperatures by 2°-9°F—a key tool in combating the heat island effect present in many cities, which disproportionately impacts lower-income neighborhoods and other vulnerable populations.
By providing inviting gathering spaces, grass cover and trees can strengthen ties between neighbors, encourage healthy children’s play, and discourage crime. In New Haven, CT, for example, a ten percent increase in tree canopy was associated with a 15 percent decrease in violent crime. Mature trees also add an average of 10 percent to a property’s value, according to a Forest Service survey.
Boosting the Economy
Sustaining a healthy urban forest—tree planting and care, managing community gardens and parks—provides direct skilled career opportunities, and is a growing field, with members of organizations like the Sustainable Urban Forest Coalition implementing workforce development and educational programs to encourage careers in urban forestry. Green industries contribute 1.6 million jobs, $82 billion in payroll, and $196 billion in sales to the U.S. economy. Trees also provide other economic benefits—for instance, workers in office buildings with views of trees report increased productivity and overall job satisfaction, while shoppers in business districts with robust tree canopy will spend 9 percent to 12 percent more for products.
Combating Climate Change
As extreme weather events continue to increase, trees can reduce greenhouse gases and energy use, lessening the impacts of climate change and strengthening the resilience of cities. At a basic level, trees remove carbon dioxide—a major greenhouse gas contributing to climate change—from the air during photosynthesis. Urban trees reduce energy use for heating and cooling homes in the U.S. by more than 7 percent. In turn, less fossil fuels are burnt to generate power, further lowering atmospheric carbon dioxide.
So what can communities do to realize the myriad benefits of trees while navigating the challenges of increasingly denser populations? Technology plays a big role, through management and assessment tools like i-Tree, and education, research and implementation platforms like Vibrant Cities Lab, which can guide decisions on what trees to plant where, and how to engage the entire community in the decision-making process. So does sharing innovative solutions from across the country, including:
To preserve and protect its tree canopy, Charlotte's Tree Canopy Preservation Program (TCPP) seeks to acquire and conserve land within the city. In certain commercial development situations, the City’s tree ordinance allows for payment in lieu of protecting trees on site, with money collected going into a fund designated for acquisition and preservation of land. Under the voluntary acquisition program, staff works with property owners to acquire land identified in cooperation with local organizations and other municipal agencies. Tree canopy is then protected under conservation easements or other legal tools for use restriction, ensuring its maintenance for future generations.
Over the past decade, the city’s Urban Forestry Section has worked across city agencies as part of an overall increase in the city’s sustainability efforts. For the Urban Forestry Section, this has meant an increased integration into construction and development projects through tactics such as pre-project tree inventories, workplans, and physical protections, and post-project tree replacement and maintenance. “We’re adding a very small percentage to the cost” of projects, explained former urban forestry manager Andrew Mertz, and “getting a much better product in the end.” The City has also partnered closely with organizations such as Keep Indianapolis Beautiful and Indianapolis Power and Light to plant thousands of trees throughout the city, with a focus on neighborhoods that stand to benefit the most from increased tree canopy.
Philadelphia Parks & Rec’s TreePhilly program gives trees away to increase canopy over plantable space in private residential yards. The program’s community mini-grants help neighborhood-based organizations run giveaway events semi-autonomously, under the premise that neighborhood groups can more effectively recruit neighbors to participate. Research shows it seems to be working, leading to more equitable distribution of trees across the city—an especially important fact given Philadelphia’s high poverty rate.
A strong partnership between the city’s urban forestry division, the Sacramento Tree Foundation, and the Sacramento Municipal Utility District has helped to grow and care for the city’s urban forest. The SMUD Shade Tree program has planted more than half a million trees since 1990, working with homeowners and community foresters to identify appropriate species and placements to maximize energy savings. The city’s urban forestry section developed a three-part plan in consultation with outside experts, prioritizing an industry-recommended 3-5 year pruning cycle, planting trees each year to maintain a diverse range of tree ages, and focusing on irrigation during the first 3-5 years of tree life—investments that are ultimately providing long-term benefits for sustainability.
Ultimately, thriving tree canopies, with their diverse benefits for cities, are fundamental to ensuring sustainable, livable communities. Trees can be a critical part of addressing virtually any of the pressing sustainability challenges that face our cities today.
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