The Not-So-Common Harebell

Hovering 200 feet over the Tennessee River, TVA uses new technology find a centuries-old species new to the region, and a new way to survey sensitive species in their native habitats.

August 4, 2020 -- TVA drones documented a rare cluster of Common Harebell plants on a Tennessee River bluff in East Tennessee this summer. This unique project started one year after TVA botanists Adam Dattilo and David Nestor noticed a few unusual blue flowers hanging from a rock outcrop, 15 or 20 feet above the ground. 

They first saw the cliff-dwelling plant in May 2019, while investigating reports of endangered plant species occurring in the area. Neither of them had ever seen this species before and they immediately thought they had found something special.  But after surveying the cliff from the base, Dattilo and Nestor realized they were never going to be able to see the mysterious blue flower up close.

With a long stick, the team dislodged a perfect specimen — roots, stem, leaves, a single flower and all. After careful examination, they ultimately identified the plant as Common Harebell (Campanula rotundifolia).

“This species is new to the state of Tennessee,” Dattilo said. “And our sample may be the only one ever collected because no other plants are within reach from the ground. Other botanists could get a sample, but they would have to rappel from the 200-foot bluff to reach the rock outcrops where the species grows.”

Finding the Flowers

To survey the site safely, Dattilo contacted Heather Hart, TVA Natural Resources & Conservation Specialist and Walt Hodges, Manager of Unmanned Aircraft Systems (UAS) Operations & Training. Together, the teams sprouted a plan to launch drones from a boat to conduct a search for more plants.

By hovering 200 feet off the ground, three to four feet away from the bluff, the drone survey would use hi-resolution imagery to remove all human safety hazards.

It took a little over a year for all three TVA departments to get everything ready for the project. When James Manni and Nigel Jones, Program Managers of UAS, manned the drones, they observed several dozen of the species growing in new locations on the cliff face.

“The request to help on this survey wasn’t one of the most common we’ve received in UAS,” Manni said. “We saw the Latin name for the flower in Adam’s email and looked at each other in confusion for a moment, but we knew we wanted to help if we could. It ended up being a fantastic project, and we’re so glad we were able to help prove that the flower is here.”

How It Got Here

According to Dattilo and Hart, Common Harebell — not easily transported by birds — is a native plant primarily found in northern latitudes and mountain outcrops, so its presence in Tennessee is extremely odd.

The nearest known sites for the species are 180 air miles from the new TVA location on Three Top Mountain, North Carolina and in Giles County, Virginia, but the plant is still very rare in both states. The species doesn’t become common until 350-400 miles north of the TVA site, and its preferred habitat extends well into the freezing bluffs of Canada and coastal Greenland.

“We’ll never really know how it came to be on the bluff,” Dattilo said. “But — given the species’ preference for colder environments — it could have been present at this site since the last ice age when both the climate and habitats in the southeast U.S. were much different than they are today.”

“It’s a strange case, but it’s here nonetheless,” Hart said. “Somehow the species has managed to acclimate to its changing environment and continue to live there, giving us the extraordinary opportunity to document it for the first time in Tennessee.”

‘The Possibilities are Endless’

Utilizing drones as a tool for preserving TVA’s natural resources is a new approach, but Hart said that drones are being utilized more and more for land and wildlife management by TVA and other management agencies everywhere. Wildlife biologists are attempting to adopt this new technology to address a wide range of questions and problems in wildlife conservation.

“Drones have a great future in being another useful tool for the work we do here at TVA, especially in plant conservation and research,” she said. “Research has found that we can use them to get an overall picture of the landscape for invasive-species prevention and control. Drones take photos with such high definition that the imagery can be processed into orthomosaics that, when pieced together, create aerial maps of the area.”

“We would like to see if drone imagery can potentially be used to census rare plant species with distinctive morphology in open habitats and understand their spatial distribution. Techniques for characterization of vegetation using high-resolution drone imagery have also received considerable study. However, the use of UAV technology to address problems in plant conservation is not well developed. The possibilities are endless for utilizing drones as a support tool for land management and treatment. It really is amazing.”

“The environmental preservation that TVA provides for the people of the Valley is fantastic, and drones are certainly an emerging technology for these specific industries,” Manni agreed. “We believe this was the start of a good relationship between our departments.”

Dattilo said that the departments’ partnership in projects like these will only continue to increase, and that it’s extremely important for preserving the Valley’s beauty that we take for granted every day.   

“You don’t have to go the Amazon rainforest or Grand Canyon National Park to see wonders of the natural world,” he said. “Since its beginning, TVA has managed rivers and public lands right here in east Tennessee that support some of the most amazing plant and animal habitats anywhere — you just have to know how to look for them.”