Louisville comprises a patchwork of neighborhoods with unique identities and cultures, each offering something different than the next.
But those differences sometimes aren’t limited to sight and sound. Louisville also has one of the worst urban heat islands, which is a metropolitan area that experiences higher temperatures than surrounding rural areas. And within Louisville’s heat island, its severity varies among neighborhoods.
“If you live on the outskirts of the county and you drive into the downtown area, for instance, there can be as much as 12 degrees difference between where you live and where you work,” said Cindi Sullivan, Executive Director of TreesLouisville. “And that’s truly significant, and what we’re aiming for is overall cooling of our community.”
One of the major contributing factors to Louisville’s heat island is its insufficient tree canopy. TreesLouisville was established in 2015 with a mission to preserve the city’s remaining tree canopy and enhance it with additional tree plantings.
The organization was created after the Louisville Metro Tree Advisory Commission, which lasted from 2012 to 2015, identified a need for the city to improve its urban forestry. Two “red flags” uncovered were Louisville’s status as having one of the fastest warming urban heat island effects in the country and a low overall tree canopy of around 26%.
Sullivan said the conservation group American Forests recommends a canopy of at least 40%. There is no single cause for the decline in Louisville’s tree canopy over the years. Among the reasons cited by Sullivan were extreme weather events, insects and diseases that wipe out entire tree species, and commercial and residential development. Climate change has been linked to some of the threats to canopies, since air pollution, changes in water cycles and rising temperatures make trees more susceptible to pests and other types of damage.
“Unfortunately, the neighborhoods that had the lowest tree canopy here in our community are typically the neighborhoods that have the lowest socioeconomic status and have been disinvested for decades,” Sullivan said. “The same neighborhoods that were redlined in the 1930s, and it continued with these discriminatory practices over the decades, are the neighborhoods that have the lowest canopy. And those are the populations that are the most vulnerable.”
Downtown’s tree canopy is around 8%, Sullivan said. The percentage in west, southwest and south central Louisville neighborhoods ranges from the teens to the low 20s. Neighborhoods in the city’s east end have higher canopy coverage, thus cooler temperatures, because of large parks and dense forestry in the area.
The heat island effects created by the city’s low tree canopy isn’t just a matter of comfort. Sullivan said high temperatures can lead to health issues and, in many cases, death.
“If we tracked heat-related deaths the way that we do heart attacks, we would be looking at a really serious health problem,” she said.
To combat the heat island effects, TreesLouisville has engaged in tree-planting efforts throughout the city since its inception. Its goal is to increase the citywide tree canopy to 45% and downtown’s to 15% in the coming decades.
Project Manager Mike Hayman has overseen work at the planting sites. Partnerships with schools, industrial parks and the Kentucky Transportation Cabinet (KTC) have helped TreesLouisville make progress towards its goals, Hayman said.
“They also have a tremendous amount of property,” he said. “It’s really, really promising to work with these big institutions, because we can put a lot of trees in on one project a lot faster than working with one person or one homeowner at a time.”
Earlier this month, Hayman and a team of contractors started a project in collaboration with the KTC to plant more than 100 trees at two downtown sites – near the intersections of Liberty and Floyd streets and Brook Street and Muhammad Ali Boulevard. Both sites are slopes near on ramps to Interstate 65.
The 80 trees planted at the Brook Street and Muhammad Ali Boulevard site also makes it easier for KTC to maintain the land, Hayman said.
“It’s a very steep bank, and it’s very hard for them to mow,” he said. “In this site, what we’re doing is planting basically a forest, which within five or 10 years, will cover this area, shade the weeds and make it a lot easier for them to mow… And we also add canopy downtown, which is the hottest area which is a heat island.”
But not just any species of tree can be planted. Hayman said much of the soil throughout the city is inhospitable for planting. Because of this, TreesLouisville chooses “tough” species for its projects.
TreesLouisville’s species repertoire includes ‘Star Power’ and ‘Canaertii’ Junipers, Sweetgums, Ginkgos, ‘Exclamation’ London Planetrees, ‘Urban Sunset’ and Trident Maples, Kentucky Coffee trees, Catalpas, ‘Wichita’ Osage Orange and ‘Frontier’ Elms.
It’s important for each site to contain a variety of trees, Hayman said. Too much of a single species increases the risk of diseases and insects wiping out large percentages of the tree canopy. Hayman said this problem has been encountered in the past with elm, ash, maple and chestnut trees.
“We plant for the long term, and we’re not going to fix this quickly,” he said. “But we have to stay at it. It’s going to go on beyond my lifetime. The trees that I’m involved in are not going to reach their maturity until 50 or 100 years.”
For Hayman, the tree canopy issue goes beyond environmental and health reasons. He’s also interested in the aesthetics of reshaping landscapes.
“I think it’s a quality of life issue,” he said. “It should be beautiful… When we plant trees… I want them to have texture and color so that when people go by, they see a pattern or a quilt.”
If a tree catches someone’s eye, Hayman said there’s a chance that person will plant the tree on their own property. He hopes that could create a domino effect where more and more trees are planted.
Hayman said that type of public involvement is crucial to the success of TreesLouisville’s mission.
“That’s really the hope that I have, is that it goes from our very visible public plantings to people seeing it and doing it themselves,” he said. “We have to have people do it themselves. TreesLouisville and the other tree planting groups, we’re not going to plant all the trees we need to.”
This planting season will continue through spring 2021. By then, TreesLouisville plans to have added thousands of trees to the city.