From Seattle to Melbourne, Trees Are at the Root of our Cities' Health

By 2050, two of every three people worldwide will call cities home. This historic urban growth, coupled with a changing climate, calls for us to team up with communities to ensure a future where both nature and people thrive in cities.

Every city is unique — but as our urban spaces continue to grow in density, we are faced with similar challenges that we can address in concert from Seattle to Shanghai. Bringing nature back is a key approach to making our cities healthier and more livable. One such example is simply to plant more trees to improve air quality and fight problems such as the urban heat-island effect.

The Nature Conservancy has studied the effects of trees on air quality in 245 of the world’s largest cities and documented the findings in the Planting Healthy Air report. The analysis found that trees are as cost-effective as many other common solutions — investing just $4 per resident in tree-planting efforts in each of these cities could improve the health of millions of people.

Though trees alone can't solve the entirety of cities' air and heat problems, they are a critical piece of the puzzle. The report demonstrates that even a conservative global investment in dozens of cities on urban trees can save tens of thousands of lives. Around the globe, we’re using trees to improve urban spaces in a variety of ways:

In Washington, we are galvanizing an active, working coalition to implement viable solutions to cleaning up Puget Sound while building green infrastructure. With King County and the City Habitats Coalition, we aim to plant 1 million trees in the region by 2020. These trees not only sequester carbon – they provide much needed stormwater benefits in urban spaces. We invite you to join the 1 Million Trees effort! Whether volunteering, donating or planting a tree, you can make a difference.

Volunteers were guided by EarthCorps volunteers to complete a restoration project along Longfellow Creek in Georgetown, Seattle. They planting 200 trees, and learned more about relationships between rainwater and freshwater health. Photo by Milo Zorzino / TNC. 

In Metropolitan Melbourne, Australia, In Metropolitan Melbourne, we are meticulously mapping trees in an Australian first that will better inform city planning and maintain Melbourne’s status as one of the world’s most livable cities. New digital mapping technology is allowing The Nature Conservancy and our partner, Resilient Melbourne, to map the vegetation of the entire Melbourne metropolitan area in a consistent way for the very first time.

In Louisville, Kentucky, The Green Heart Project is examining the link between neighborhood greenery and human health. This collaboration is led by the University of Louisville, The Nature Conservancy, Hyphae Design Laboratory and the Institute for Healthy Air Water and Soil, to inform a new municipal decision-making process that prioritizes health. In Fall 2018, the team will plant 8,000 trees, plants and shrubs (many of them mature specimens) to create an urban ecosystem that promotes physical activity while decreasing noise, stress and air pollution. Over the next three years, 700 residents will receive annual check-ups to evaluate how the increasing greenery has affected their physical and mental health and their social ties.

The Brightside Organization, The Nature Conservancy, UPS and Brown-Forman partnered to plant 150 trees along West Broadway from 20th Street to the end at Shawnee Park in Louisville, Kentucky. Photo credit: © The Nature Conservancy (Devan King)

Tree planting is just one strategy that city planners can use to mitigate heat and air pollution. But only trees can both cool and clean the air. Furthermore, trees and other green infrastructure provide a broad range of co-benefits, as well—including habitat for wildlife, stormwater control, recreation opportunities, and beautification of public and private spaces in cities.