There’s a disagreement over the size of Charlotte’s tree canopy
Charlotte is known as the “Queen City.” But another nickname could be the “Tree City,” because of its lush tree canopy.
A new study on that canopy released last month concluded trees cover roughly 47% of Charlotte, down about half a percent from 2018. That was surprising because an earlier study from 2012 to 2018 found the canopy had shrunk more, to 45%. Not everyone agrees with the latest study’s findings.
Here to talk more about it and why it matters is Gavin Off, who wrote about this for the Charlotte Observer.
Marshall Terry: Who conducted this latest study and what is the disagreement over?
Gavin Off: The Colorado-based firm PlanIT Geo conducted the most recent study that looked at Charlotte's canopy from 2018 through 2022. PlanIT Geo found that canopy coverage decreased from around 47.8% to 47.3%. So basically, it said our canopy remained unchanged. The discrepancy arises when you take into account a previous canopy study, done by the University of Vermont, and measured the city’s canopy from 2012 to 2018. [The University of] Vermont found that during those six years, our canopy dropped from 49% to 45%. So when you look at the two different studies, not only is there a difference in several thousands of acres of trees, but there's also the possible difference in how fast we're losing them.
Terry: Who are the naysayers here with the most current study? And what do they think the real number is?
Off: Well, that's just it. Given the discrepancy between the two studies, no one knows what the real number is. I talked to the city and TreesCharlotte, both of whom funded the most recent study, and they think the new assessment is accurate. But then, there are local experts who I talked to, [like] Doug Shoemaker, who’s a UNCC ecologist who has studied our canopy for years, and Chuck Cole, he's the former head of TreesCharlotte, and both have a hard time believing that Charlotte’s canopy has remained stable, which is what PlanIT Geo found. As Doug told me for our article, saying it remains stable essentially flies in the face of what we know and see anecdotally.
Terry: Let's get a little technical here: How do people who study this count the exact number of trees in Charlotte, and why is it difficult?
Off: Well, they don't exactly count the number of trees. What they do is that they count the number of acres that trees cover. The best approach is usually a combination of two things, one being high-resolution aerial imagery, you can think Google Maps, and the other being LIDAR, which stands for Light Detection and Ranging. Imagery is great for detecting colors. LIDAR is great for measuring the heights of things. So, while imagery can see if something is green, LIDAR could help say if that green thing is grass or shrub or tree.
Now the 2018 Vermont study used both LIDAR and imagery. PlanIT GEO’s analysis relied on imagery, but the folks there said their machine-learning model was trained on light art, so it should have LIDAR-like results.
Terry: Why is it so important to get an accurate number for the tree canopy?
Off: Charlotte has long had this goal of reaching a 50% canopy by 2050, and you might think that 45%, 47%, close enough. But that's thousands of acres, and that matters if the city is going to keep 50% by 2050, or something like that. It could help determine how many trees the city has to plant or where they have to plant them. It could help determine how many acres the city would have to preserve and how much money it spends doing that. And it would ultimately go into account what types of tree-saving policies or regulations the city enacts. And of course, that would affect developers and development.
Terry: Why do trees matter? I mean they produce oxygen and look nice. But besides that, why are they important?
Off: Yeah, you're right. I think most people would agree that it's nice to drive through Myers Park or Dilworth and see those big 80-foot-tall Willow Oaks.
They're more than nice to look at. Studies have shown that being near trees reduces stress, improves mental health, improves worker productivity and even student test scores. Their roots absorb water, their leaves absorb carbon dioxide, which is a greenhouse gas, and they also provide shade.
You and I might have a nice home to go to with air conditioning, but I'm sure not everyone in Charlotte has that, so a healthy tree canopy could certainly help.