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How trees can be key to healthy urban neighborhoods

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In Louisville, the Green Heart Project is testing the “power of nature to project human health”

Cherokee Park in Louisville

Trees can add charm to city blocks. A new study launching today in Louisville, Kentucky, wants to see if trees can also become low-cost ways to improve the health of a neighborhood.

A joint effort by the Institute for Healthy Air, Water and Soil, the Nature Conservancy, and Dr. Aruni Bhatnagar, a pioneer of the study of environmental cardiology, the Green Heart Project will explore the long-term impact of trees on important indicators of livability and health, including respiratory and cardiovascular disease, as well as stress and social well-being. It’s the first-of-its-kind looking closely at the link between greening cities and healthy neighbors.

“Instead of working at a front yard level, we’re working at a neighborhood level,” says Veronica Combs, Director of the Institute for Healthy Air, Water and Soil.

By focusing a long-term lens on the impact of tree cover to overall urban health, the study hopes to chronicle the connection between nature, the environment, and human health, and eventually provide guidance for other cities to replicate.

Learning a tree’s true value

Louisville is sadly an ideal place for this trial. With one of the highest levels of air pollution among American cities—earning an "F" grade from American Lung Association the last six years—the city has a higher than average asthma rate, impacting 13 percent of the population compared to the national average of 8 percent.

Institute for Healthy Air, Water and Soil,

Studies have connects the city’s poor air quality to higher risks of heart disease, obesity and diabetes, the leading causes of death in Louisville. We may intuitively suspect that living ‘in nature,” around trees and away from polluting factories and cars, benefits our health. Studies by the Institute have show that trees add approximately $330 million in benefits annually to the city, in the form of resiliency and reducing pollution. In addition, the group tested how tree canopies block pollution at a site near Saint Margaret Mary school, and found the buffer cut dangerous particulate matter, a damaging pollutant, by 60 percent.

But no one has quantified the extent to which trees and vegetation can impact human health, or nullify the negative effects of local pollutants. The Green Heart Project was designed to define these connections. By setting up tree canopies near roadways, and planting additional trees in parks and backyards, the project hopes to create buffers to absorb pollution and shade to counteract the urban heat island effect.

The study will pack four neighborhoods across the city with a dense canopy of evergreen, oak, and gold cypress trees, adding 2,000 mature trees, 2,000 saplings, and 4,000 other plants, shrubs and bushes, aiming for four new, mature trees for every five residents. Researchers will measure air quality this fall to obtain a baseline, recruit participants this spring, and then finish planting during the second half of 2018. They’ll track the health of the 700 volunteers through the project’s timeline (currently, they have enough grant funding for five years).

Pollution isn’t like cholesterol, which builds up over the years, Combs says. It’s impact is pretty immediate, so the trial will have more than enough time to establish potential correlations.

A different approach to neighborhood health

The Green Heart Project launches as a confluence of factors conspire to make respiratory issues, such as asthma, worse. Climate change, and the steady rise in temperatures, triggers the condition, says Combs, while lengthening pollen season, adding additional irritants to the air. It’s one of many factors explaining why childhood asthma rates are rising, especially among the African-American population, both nationally and in Louisville. The Institute recently created an environmental data map tracking asthma triggers, installing air sensors throughout the city.

Researchers hope that by adding trees and creating pocket parks and more space for social interaction, they can not only positively impact health outcomes and help reduce asthma, but also create and strengthen social ties, and lessen isolation and depression.

The health care system has expressed great interest in the study, says Combs, as big players such as Humana begin to place more focus on the social impacts of health, and ways to impacts community health outcomes on a larger scale. Trees, she says, may be shown to be a valuable long-term investment.

“It’s a different approach to health,” she says. “It’s not, ‘are you taking your medicine?’ it’s more, ‘are you living in a place that supports your health?’ Does it have low pollution? It is walkable?”

If trees are shown to have as large an impact as Combs thinks they will, this type of planting project could become a model for a more cost-effective means of impacting neighborhood health, especially those suffering from concentrated poverty. Other efforts, such as sending volunteers, social workers, or health care workers door-to-door to offer care, assistance, and interaction, have trouble scaling, and can quickly become prohibitively expense. Trees can be cheaper, says Combs, and do more than add character.

“If you can get the neighborhood right, you can go from there,” says Combs.