In the fall of 2017, the Green Heart Project was launched to examine the link between neighborhood trees and human health in Louisville, Kentucky. The five-year study is the first of its kind to scientifically assess the impact of urban green space on air quality and human health. This collaborative project, led by University of Louisville, The Nature Conservancy, Hyphae Design Laboratory, and the Institute for Healthy Air Water and Soil, aims to guide future decision-making processes that connect human health with nature.
For six years preceding the study, the City of Louisville received an “F” from the American Lung Association for year-round particle pollution. Tree canopy analysis estimates that the city is losing over 54,000 trees each year due to age, invasive insects, development, and other factors. Louisville’s urban tree canopy is presently 37%; however, tree loss trends indicate that the canopy may decrease to 31% in the next ten years. Recent studies connect Louisville’s poor air quality to higher risks of heart disease, obesity and diabetes, which are the leading causes of death in the city. These challenges have made Louisville a perfect laboratory to test urban greenness and human health.
Launched with a large grant from the Owsley Brown II Family Foundation, the Green Heart Project has received additional support from The Nature Conservancy, the National Institute of Environmental Health Sciences, the United States Department of Agriculture Forest Service, and many other regional and local sources.
To determine the best location for Green Heart, project leaders evaluated existing tree cover, plantable space, roadways, population density, and neighborhood characteristics throughout the City of Louisville. This initial assessment led to choosing a three-square mile study area in South Louisville that encompasses six communities with approximately 22,000 residents. The study is made up 16 matched clusters, which includes eight target and eight control groups. More than 750 individuals have been recruited for the HEAL study, which records baseline heath, stress levels, disease risk, and lifestyle factors. University of Louisville is maintaining this cohort of community volunteers who are participating in the clinical studies and plans to recollect a post COVID-19 baseline in the spring of 2021 as well as previously established measurements.
Within the study area, Green Heart Louisville is measuring environmental parameters such as air pollution, light and vegetation metrics before, during and after planting has occurred. This data will be used to assess the effect of vegetation on air quality and noise, and will compare changes in health assessment data collected during the HEAL study. Green Heart Louisville has installed 60 passive air samplers on utility poles to collect data on airborne concentrations of ozone and nitrogen dioxide. Real-time monitors installed on vehicles are also used along pre-determined driving routes to measure air quality, and noise monitors are rotated throughout 60 sites to map noise levels. Satellite data and remote sensing data display vegetation density before and after urban greening. In 2022, the study will begin to compare changes in pollution, physical and mental health, and social cohesion from before tree planting, and will continue for two years after planting is complete.
The Nature Conservancy has contracted with a local non-profit partner, Louisville Grows, to plant and care for trees in the project area. Initial delays in recruiting volunteers for health monitoring coupled with COVID-19 delays have slowed tree planting efforts; however, planting initiatives are underway, and more than 1,100 trees will be in the ground by late fall of this year. In addition to private property plantings, TNC has partnered with the Kentucky Department of Transportation to plant large trees along the adjacent expressway in the study area to reduce volatile organic compound and particulate matter air pollution. By the end of the study, nearly 8,000 new trees and shrubs will be growing that will serve as a robust and sustainable ecosystem to maximize the removal of air pollution.
The Nature Conservancy is also working to maintain the health of existing trees in the Green Heart Louisville area. In 2019, TNC partnered with YouthBuild Louisville to carry out a baseline tree health assessment for existing trees in the target area using the Healthy Trees, Healthy Cities application. The Healthy Trees, Healthy Cities app is now being used for tracking tree planting, health and stewardship, as well as for mapping and managing ash tree treatment on public and private properties. After all plantings and treatments are completed, the team will conduct a post greening intervention clinical follow-up of targeted volunteers. Due to the impacts of COVID-19, University of Louisville has received a one-year grant extension from the NIH.
Planting trees and developing greenspace in neighborhoods helps to break up concentrated heat and mitigate rising temperatures. When communities invest in adding greenspace, they are ultimately investing in public health and reduction of energy costs for their community.
Research demonstrates positive connections between human health and access to nature. Being near trees has a host of physical and mental health benefits. But tree canopy is not equally distributed in developed areas. Urban forestry specialists are using geospatial analysis of tree canopy to identify residential areas and public spaces to prioritize projects that will cultivate greenspace for healthy communities.