From Dust Bowl to Green Heart: How Trees and Policy Can Shape Public Health
September 4, 2024
Overview
The University of Louisville’s Green Heart Project found that living in or around green canopy enhanced cardiovascular health. Beyond the findings related to cardiovascular health, the project provides strong support for the positive impacts of urban greening and highlights the role that environmental interventions can play in fostering healthier, more resilient communities.
The New Deal’s ambitious 1930’s initiative to plant a “Great Wall of Trees” to mitigate the Dust Bowl’s wind erosion marked an early recognition of the benefits of green spaces. Decades later, the field of ecopsychology underscored the positive connection between nature and mental health. Now, recent findings from the University of Louisville’s Green Heart Project highlight the link between green canopy and enhanced cardiovascular health. These insights provide a foundation for integrating strategies that prioritize green infrastructure to foster public health and well-being.
Background
The Health, Environment, and Action in Louisville (HEAL) study of the Green Heart Project, aimed to assess the relationship between greenness—or areas of land with vegetation—and blood pressure, focusing on spatial proximity, different types of greenness, and the variability of these associations based on participant characteristics. Specifically, the study investigated whether the associations observed in larger spatial scales held true within neighborhood areas; how these associations varied by greenness typologies (for example, tree canopy, deciduous or coniferous trees, grass cover); and whether certain participant subgroups were sensitive to these associations.
Beginning in 2018, the Green Heart Project “documented health data for 745 people living in a four-mile square radius in South Louisville.” With support from volunteers, the team then planted thousands of trees from 2020 to 2022 in the center of the study area, and routinely assessed residents’ health in both planted and unplanted areas.
While the study is ongoing, the team has found significant associations between greenness and blood pressure for residents in the center of the study area, though these associations vary widely. Notably, a higher leaf area index, or the amount of leaf material in a canopy, was associated with lower systolic blood pressure within 150-250 meters and 500 meters of homes. However, these associations were not observed for grass cover. Positive associations between leaf area index and systolic blood pressure were most evident “among participants who reported being female, White, without obesity, non-exercisers, non-smokers, younger age, of lower income, and who had high nearby roadway traffic.”
More research is needed to better understand outcomes in communities of color.
This data is noteworthy as urban areas across the country are grappling with the negative impacts of diminishing tree canopy and air pollution on health. Exposure to air pollution, for instance, can lead to oxidative stress and inflammation in human cells, potentially contributing to chronic diseases and cancer. Studies have also shown that short-term exposure to high levels of outdoor air pollution is linked to decreased lung function, asthma in children, heart issues, visits to emergency departments, and hospital admissions. Exposure to fine particulate matter (PM2.5) is linked to increased mortality rates, raising significant public health concerns. This burden disproportionately affects economically disadvantaged populations, and Black individuals who face a particularly heightened risk of premature death from PM2.5 pollution compared to their White counterparts.
Addressing these environmental impacts and disparities is crucial for advancing not only public health, but health equity.
Policy Considerations
Legislation that supports green infrastructure in urban planning, like the Great American Outdoors Act, can provide substantial long-term health benefits while also enhancing environmental sustainability. Green infrastructure includes parks, school yards, green roofs, community gardens, and urban forests. These elements not only provide recreational spaces but also mitigate the urban heat island effect, reduce air pollution, and enhance stormwater management. Policymakers can incentivize the development of green infrastructure through tax credits, grants, and zoning regulations that require a certain percentage of green space in new developments.
Additionally, policies should promote equitable access to green spaces. Studies have shown that access to green spaces is often unevenly distributed, with those communities who are marginalized having fewer and lower-quality green spaces. Prioritizing the creation and maintenance of green spaces in underserved areas may be achieved through targeted funding, community engagement in planning processes, and partnerships with local organizations to ensure that the protection offered by urban greening is accessible to all members of a community.
Policymakers can also consider long-term sustainability and resilience in urban greening initiatives. This involves adopting policies that support native vegetation, biodiversity, and climate adaptability. Urban greening efforts can be integrated into broader climate action plans or heat action plans, ensuring that cities are better equipped to handle the impacts of climate change. By fostering collaboration between public health officials, urban planners, environmental scientists, and community members, policymakers can develop comprehensive strategies that promote healthier, urban environments for current and future generations.
The implications of the Green Heart Project extend far beyond the immediate findings related to cardiovascular health. By showing the positive impacts of urban greening, the project lends itself to policy changes that prioritize sustainable urban development and equitable access to green spaces. In doing so, it highlights the role that environmental interventions can play in fostering healthier, more resilient communities.
This post was written by Nina Belforte, Deputy Director, Strategic Communications, Network for Public Health Law — National Office and reviewed by Jill Krueger, J.D., Director of Climate and Health.
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