Counting trees and planning for the future

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Raleigh’s Urban Forester Sally Thigpen discusses her work and the street tree inventory underway this month.

Ben Brusie stands near Granada Drive and Tyson Street, facing a house. He counts his paces — 15  – and walks onto the lawn.

Wearing a bright yellow helmet and an odd-looking backpack, Brusie examines the nearest tree, making notes on a tablet device. He then holds a stick up to the tree, makes another note and moves on, counting his paces.

If you haven’t already, you might see Brusie or someone like him wandering around your street.

He is not trespassing, and no, he’s not checking for UFOs. Bruise is an urban forester, part of a team taking a street tree inventory in Raleigh this month.

Raleigh’s first street inventory, to be exact.

And long overdue, according to Sally Thigpen, Raleigh’s urban forester.

“It’s critical,” Thigpen said. “It is very routine for urban forest management to pursue and get a street tree inventory for your city. Charlotte’s got one, Greensboro’s got one …  It’s kind of like Urban Forest Management 101: Get a street tree inventory.”


Ben Brusie counts trees in the city right-of-way. Photo by Jennifer Wig.

What is a Street Tree Inventory?

A street tree inventory is a complete survey of all trees and planting sites within the city right-of-way or on city-owned land such as parks. This data will enable Thigpen and her team to better manage Raleigh’s urban forest.

Thigpen and her crew of eight maintenance workers have a lot of ground to cover: more than 1,100 miles of street right of way, 9,000 acres of parks, about 63 miles of greenways and all the city cemeteries and properties.

After a large ice storm, her crews are out in full force, cleaning up dead limbs and removing potential hazards. The only trees they don’t manage are those planted under power lines, which are maintained by Progress Energy.

“It’s a pretty daunting resource that we have to maintain,” she said. “We have to make sure the trees are safe for people using the public right of way and our trails, that there aren’t any hazardous trees that could impact pedestrians and vehicular traffic. And because don’t have a really good grasp of what our resource is, we are very much reactionary.”

Why do we need one?

Thigpen relies on inspectors, parks and recreation staff and citizens to report when city trees are old, decaying or hazardous.

Knowing what kind of trees are planted in the city, where they are and what condition they are in will enable Thigpen and her crew to work more efficiently. The data will help identify where trees are needed, help them prioritize which trees need to be pruned or removed and will document the benefits of the urban forest.

“It allows us to create a strategic plan on how we’re going to manage the resource into the future, what our needs are going to be to do it effectively,” she said.

The inventory began in early 2010 with interns who are studying forestry at NC State. Working part-time, the interns managed to collect the species, size and condition information of trees in the Northeast section of Raleigh – about 25-30 percent of the city.

Thigpen used a grant of $10,000 from the Division of Forest Resources, plus a match from the city, to pay for that portion of the project. Money from the city’s Sustainability Fund – $175,000 – will pay for an outside firm, Davey Resource Group, to collect data for about 70,000 trees inside the Beltline.

With full-time crews, Davey will have its section complete at the end of February. At that point, the tree survey will be about 60 percent complete. Thigpen is still seeking funding for the final portion, but hopes to find grant money or city funding to complete the project by the end of 2011.

The data gathered will be invaluable, she said, from knowing just how much carbon the city’s street trees are sequestering to how much space out there still needs trees.

“We can identify areas in the city that have fewer street trees and we can target those for planting rather than saying, ‘Oh I know there’s a new neighborhood that just went in in southeast Raleigh. Let’s go offer them some trees.’ Now we can really do it much more equitably and with a much clearer picture of what the needs are.”

Knowing the type of trees in Raleigh will help prevent a widespread wipeout from disease, Thigpen said. Many cities, including Cary, are losing stands of Hemlock trees to a non-native bug, the wooly adelgid. Midwestern cities, heavily planted with a type of Ash, have been decimated by the Emerald Ash Borer.

“So when I look at some of the numbers we have now, that shows us that we have 20, 25 percent Maple, that makes me concerned,” she said. “We need to increase our diversity.”

The public will also have access to the tree information through iMAPS, and will be able to see that the huge tree near their neighbor’s house is a 28-inch red Maple in great condition.

What’s that guy doing?

So back to Ben Brusie and his coworkers from Davey Resource Group. The company conducts street tree inventories nationwide. Brusie and his cohorts are arborists certified by the International Society of Aboriculture. Brusie’s yellow pack holds a GPS tracker, sticking up to locate his signal. In his hands, Brusie holds a tablet with the map – sort of like looking at Google maps on your phone or iPad. His version also shows the lines depicting the city’s right of way and his exact location. At each tree, he enters the location and address. He notes the tree’s scientific name and common name. He then uses a measuring stick called a Biltmore stick to measure the tree’s diameter at breast height.

Then he moves on, counting 15 paces down the street. If no tree is there, he observes whether one could be planted. Is there room? Are there power lines in the way or a fire hydrant? And so on.


Photo by Jennifer Wig.

Why is an urban forest so important?

It may seem like a lot of time, energy and money is spent worrying about the number and condition of the city’s trees. But the trees have many benefits.

On average, a tree will absorb one ton of carbon dioxide during its lifetime. Trees can also help a city with stormwater mitigation, erosion control, improving water quality, reducing a building’s energy costs and supporting urban wildlife.

Aside from that, people just feel safer when there are more trees, Thigpen said. More people walk in tree-lined areas because it’s a buffer between them and vehicles, she said.

And believe it or not, money really does grow on trees. Studies indicate that people who shop in areas with big trees actually spend more money than those shopping in concrete jungles. Real estate values are also higher when there are more trees.

“It’s kind of an unconscious thing, but when you’re driving down a tree-lined street, it’s somewhere people prefer to be. They just like it better,” she said. “That means ch-ching dollars for the city.”

“So there’s real hard science behind this stuff. We don’t just plant trees because they’re pretty.”

So how is the City of Oaks doing?

Raleigh’s nickname is not without merit. Of the 65,000 street trees inventoried so far, 4,578 are Oaks. That’s around 7 percent. Thigpen guesses Davey’s crews will find many more Oaks inside the beltline.

Indeed, Davey’s workers said the biggest tree they’ve measured so far was 80 inches in diameter — on an Oak tree downtown.

However, the street tree inventory will not indicate the city’s overall canopy cover. Thigpen guesses Raleigh’s canopy – like that of many cities – is declining, despite laws requiring conservation and buffers.

“Are we losing in the short run? Absolutely. Anytime we have to cut down a big tree, that’s 50 years, 100 years it takes for a tree to get really large. That’s a hit, it really is,” she said. “As long as we’re planting them back, I think we’re doing OK.”

Thigpen said Raleigh has been proactive about planting in developed areas. For example, 400 trees will be planted this spring in the area where Edwards Mill Road was expanded. She said contributions from Umstead and the other many state- and city-owned parks help the area tremendously.

“Trees grow in this town. We have a lot of trees so that makes me very confident that even though we’re always playing catch up in the city and fighting development,” Thigpen said. Planting trees, she said, “is just part of the plan now. It’s just automatic.”

The Future

Still, Thigpen hopes she can convince someone with grant funding that Raleigh’s trees need to be inventoried – not just to complete this first step, but to monitor the city’s trees in the future. Ideally, she would inventory a different section of the city each year on a rotating basis.

Doing so could save lives, she said. Just last month a tree killed someone when it fell and crushed an occupied vehicle in Gatlinburg, Tenn. A similar incident happened on Old Stage Road in Garner in 2009. That tree was on private property and would not have been impacted by the inventory. But Thigpen said that does not mean the city shouldn’t do its best to prevent those types of problems on its land.

“If we had a complete street inventory we’d be able to identify trees that are in poor condition and do some proactive maintenance on them rather than waiting for something like this to happen during a thunderstorm,” she said. “A lot of cities use street tree inventories as a management tool, and with Raleigh the Capital City, we should really be the leader in the state for urban forest management.”

One thought on “Counting trees and planning for the future

  1. The tree inventory also helps with urban biogeography projects that help us understand how to manage urban forests for longevity and biodiversity. There is a lot of evidence that says urban areas can support diverse wildlife. Some wildlife even prefer urban habitats. Much of the biodiversity we lose through urbanization, we can regain from studying how to maximize urban life for other creatures. There are many ongoing projects, including several at NCSU where I’m a student, that focus on this very topic.