JUDY WOODRUFF: As we know, trees can add beauty and a sense of serenity to a neighborhood.
But, as John Yang discovered, researchers have launched an ambitious project in Louisville,
Kentucky, to see if greenery can also improve public health.
JOHN YANG: On a crisp morning in South Louisville, a 20-foot evergreen is deployed into an urban
laboratory.
At the designated spot, a three-man crew painstakingly lifts, twists and bends the tree, a green
giant arborvitae, to be precise, maneuvering it under a web of utility lines, until homeowner
Mark Goeing is the happy treecipient.
You turn around, you see that brand-new tree in your yard, how does that make you feel?
MARK GOEING, Homeowner: I think it looks beautiful.
And maybe it is just a long-term impact that maybe I won't live to see, but trees are obviously
a good thing for our environment.
JOHN YANG: Goeing, a retired zookeeper, is among the hundreds of South Louisville residents
getting trees, shrubs and other greenery over the next year.
It's part of a projected $15 million research project conducted by the University of Louisville
and sponsored by the National Institutes of Health and The Nature Conservancy.
It's called Green Heart Louisville.
Researchers say this project is the first of its kind, a large-scale scientific study
of how trees and green spaces affect residents' health.
It comes at a crucial time for the city of Louisville.
Between 2004 and 2012, the city lost an average of 54,000 trees a year to development, storms,
pests, and old age.
During that time, the tree canopy coverage in Louisville dropped to just 37 percent,
well below other cities in the region.
And since 1996, the American Lung Association has given the city a failing grade for air
pollutants like ozone.
What's more, Louisville is one of the nation's fastest-warming urban heat islands.
Parts of the city can be 10 degrees hotter than surrounding areas.
Green Heart researchers think more trees could be a solution.
They can improve air quality, cool neighborhoods, help combat global warming, and even muffle
noise pollution.
Chris Chandler is The Nature Conservancy's urban conservation director in Kentucky.
When you look at a street like this, what do you see?
CHRIS CHANDLER, The Nature Conservancy: I see an aged neighborhood with a declining
urban tree canopy.
It's had a lack of stewardship over the years and a lack of investments.
Our old trees are dying, and they're not being replaced and managed over time.
Nature is not a nice-to-have.
It's a must-have.
JOHN YANG: So, streets like this are a focus of the Green Heart study.
Crews are planting and helping maintain around 8,000 trees, shrubs and flowering plants in
South Louisville neighborhoods that are home to about 35,000 people.
Researchers have made baseline physical and psychological health assessments of some 700
residents, checking their blood pressure, lung capacity, and stress levels.
Half the participants will get new foliage on or around their properties.
Half will not.
After two years, they will be examined again to compare changes between the two groups.
ARUNI BHATNAGAR, University of Louisville Medical School: This is a very ambitious project,
both in terms of its scope, its time and its resources.
JOHN YANG: Aruni Bhatnagar of the University of Louisville Medical School is the lead researcher.
This is like testing a new drug.
ARUNI BHATNAGAR: It is exactly like -- same methodology.
We have a control group, in which there will be no change in greenness.
We have a treated group, where is we have put greenness.
So it's exactly run like a clinical trial with a placebo, but without -- instead of
a drug, we have trees.
JOHN YANG: Research has already shown that green space can relieve stress, but the team
in Louisville wants to know more about its effects on overall health.
CHRIS CHANDLER: What we hope to unlock is new foundational science that better allows
us to understand the role that nature plays in improving our health.
And if we can do that, we can change blueprints on how you build a healthy, just community
to be green prints and to include nature in that story.
JOHN YANG: In Louisville, as in so many cities, tree canopy coverage is a matter of rich and
poor.
The view from above tells the story.
Wealthier areas, like this East Side neighborhood, have up to twice as many trees as poorer areas
in the South and West, which have histories of discriminatory housing practices.
And the difference in health outcomes is staggering.
Due to a variety of factors, life expectancy is up to about 13 years shorter on the West
Side than the East.
DR.
SARAH MOYER, Louisville Public Health Director: Your zip code determines your health probably
the most.
JOHN YANG: Dr. Sarah Moyer is Louisville's public health director.
DR.
SARAH MOYER: We have neighborhoods where people are living really long and experiencing great
quality of life.
And so what is going on in those neighborhoods that we can bring to other ones?
Nature is one of those things that's different between those communities.
And how do we bring that to everyone in our city?
AMY YATES, Louisville Resident: It's pretty much just always been bare in this area as
far as trees go.
JOHN YANG: Amy Yates' South Louisville neighborhood is dotted with reminders of where trees once
stood.
Yates says she inherited a green thumb from her grandmother.
AMY YATES: My grandmother and I planted this tree in 2009, the year after my dad passed
away, kind of as a memorable thing.
JOHN YANG: The single mother of three has lived in this house 15 years.
She volunteered for the Green Heart study partly, she says, because her 14-year-old
son has asthma.
AMY YATES: Trees produce oxygen.
And they clean the air.
You know, they're beautiful.
It sustains our life.
It's the lungs of our planet.
JOHN YANG: She says she's not entirely surprised about her hometown's health inequality.
AMY YATES: I'm always very curious to see how where we live affects us.
You know, when you have kids, you want them to live long, happy, healthy lives.
And, sometimes, you're limited with your means.
And it is very sad to think that, because of that, we might live less years on this
planet because of it.
JOHN YANG: And this experiment will determine whether trees could spread a canopy of health
over more neighborhoods.
For the "PBS NewsHour," I'm John Yang in Louisville, Kentucky.