LOUISVILLE — A research project years in the making through the University of Louisville, The Nature Conservancy and other partners has found planting thousands of trees and shrubs in a south Louisville neighborhood has improved the health of hundreds of residents.?

The University of Louisville’s Christina Lee Brown Envirome Institute launched the Green Heart Louisville Project in 2018. It has planted more than 8,000 large trees and shrubs across a four-mile area and studied the health of 745 nearby residents before and after the trees were planted.?

The researchers took blood, urine, hair and nail samples to collect health data from residents while also measuring tree coverage and air pollution levels in the area. The researchers then compared the collected data to city residents outside the research area.?

The results, announced before a crowd of supporters Tuesday in Wyandotte Park in south Louisville, showed residents living in the greener area had 13% to 20% lower levels of biomarkers for general inflammation.

Trees along a walking path in Wyandotte Park are among the thousands planted in neighborhoods and along the nearby highway corridor. “You all see those beautiful trees that are behind me? Well, they are more than beautiful. They are medicine,” said University of Louisville President Kim Schatzel to the crowd of supporters. “They are part of the revolutionary project to document and understand how trees affect the health of people living around them.”?

The biomarkers measured are called high-sensitivity C-reactive proteins, and higher levels of those proteins are strongly connected to cardiovascular disease and, according to a University of Louisville release, are “an even stronger indicator of heart attack than cholesterol levels.” Higher levels of the proteins are also connected to increased risk for diabetes and some cancers.?

Aruni Bhatnagar, the director of the Christiana Lee Brown Envirome Institute, framed the research as having the potential to significantly reduce heart attacks among Louisivillians.?

“We have over 1,800 to 2,000 heart attacks in Louisville every year, and if you can even decrease 10%? — that’s 200 lesser heart attacks,” Bhatnagar said. “If we can work on the scale that we’ve done here for the entire city, there will be a huge benefit. We can only think what it would be for the entire country.”?

Bhatnagar said while past research has shown that people living in “green communities” have a lower rate of mortality, he wasn’t aware of research like the University of Louisville project that compared the health effects of greenery added to a community.?

Toni Smith, 71, is one of the study’s participants and has lived across the highway from Wyandotte Park for the past 17 years. She said the added trees have helped beautify her neighborhood along with block some of the air and noise pollution coming from the highway.?

Smith, sitting under the shade of a tree in the park, said there’s a “certain calming aspect” to tree coverage, especially for those who love the outdoors. She said she’s a big advocate of anything that can help improve the environment and health of her neighborhood, mentioning the study has also served as a helpful health screening for participants.?

She would have had researchers plant a tree in her own yard, but there wasn’t room.?

“Because of my love of nature, I didn’t have a square inch to plant a tree, or I definitely would have had them come,” Smith said.