Morning sunlight on a Fernbank Forest trail Invasive ivy was a major problem for Fernbank Forest's native species, but those native plants have begun to flourish once again. (Photo: Fernbank Museum of Natural History)

Atlanta is often called The City in the Forest, and Atlantans take great civic pride in the nickname, and justifiably so. That's because the phrase reflects both Atlanta's historical legacy and the current number of trees along the city's streets and in its neighborhoods and parks.

The city, an international crossroads at the heart of America's ninth largest metropolitan area, was carved out of ancient forests more than 175 years ago when Georgia created a railhead to link the state to the Midwest. Today, Atlanta's tree canopy is well above the average for American cities — trees cover 47.9 percent of Atlanta, according to research conducted in 2008 by the Center for Geographic Information Systems and the Center for Quality Growth and Regional Development at Georgia Tech. The national average in U.S. cities is 27 percent, according to the U.S. Forest Service.

While trees — magnolias, dogwoods, redbuds, pines, towering tulip poplars and oaks, majestic maples and numerous other species — can be seen throughout the city, the forest that existed when settlers drove a stake into the ground in 1839 to mark the rail line's zero-mile post is long gone, with one prominent exception. Fernbank Forest, located on the campus of Fernbank Museum of Natural History, is an intact 65-acre mixed hardwood forest that has survived urban planners, bulldozers, sprawl and — to some degree — even neglect. The forest, which has been closed to self-guided tours since the summer of 2012 so employees and partners could restore the woodland to its natural condition by removing almost 50 species of invasive non-native plants, re-opened Sept. 24.

"Our end goal is not to remove all of the invasive species, the end goal is to have a healthy and diverse forest," said Fernbank ecologist Eli Dickerson. "We want to preserve the native species and the native biodiversity intact as much as possible while also removing invasives."

'A forever project'

In four years, Dickerson and teams of staffers, local volunteers and several nonprofit partners have made significant progress. Dickerson estimates they have done restoration work on a little over half of the forest. However, he quickly points out that restoring a forest is "a forever project." That's because seeds and root pieces broken off when invasives were removed could re-sprout, or birds, mammals or even humans could re-introduce invasive non-natives. "If we just sit back and say, 'Hey, great, we did a good job' and just leave restored areas alone for two, three or five years, we are going to have the same problem," Dickerson said. To prevent that from happening, he said his plan is "to get restored areas into a maintenance phase where we can maintain them with staff and volunteers without backsliding."

Before and after photos show Elephant Rock in Fernbank Forest Invasive plants may have made Fernbank Forest look greener, but they threatened native plants' survival. Here, Elephant Rock is pictured before (top) and after (bottom) restoration efforts. (Photo: Fernbank Museum of Natural History)

They've come too far for backsliding. Some of the areas of the forest floor adjacent to one of Atlanta's oldest neighborhoods were 95 percent covered with English ivy. Volunteers have been removing that ivy and other invasives such as Chinese wisteria, Chinese privet, chocolate vine, leather leaf mahonia and thorny olive. Not only was the wisteria threatening trees because it had climbed into some of the canopy, but the other non-natives were choking out an array of native plants. In the areas where restoration has been done, Dickerson said native plants such as Christmas fern, trilliums and wild ginger have flourished, native shrubs like viburnum, spicebush and hearts-a-bustin' are looking healthy again and tree seedlings such as tulip poplars, beech, ironwood and oaks are sending up shoots.

"Pretty much all of the native plants in the forest are producing seeds, so we know there is a pretty good seed bank," Dickerson said. "They just need a chance to germinate without being smothered by invasives."

He thinks in time even more native plants will emerge. "I would really love to see some of the native ferns such as sensitive fern and more of the lady ferns come up. At one time there were probably as many as 15-20 native fern species in the forest. At last count, we probably have about 10 or 11."

Dickerson also plans to transplant native trees as part of the restoration. "We'll probably stick with a lot of the same species we have. That would include tulip poplars, American beech, white oak, northern red oak and maybe even some lesser known trees like black gum and basswood."

Forests within cities

Fernbank is not unique by virtue of simply being an old growth urban forest. "Every major city in the nation has old growth urban forests," said Robert Loeb, professor of biology and forestry at Pennsylvania State University, DuBois Campus. Several cities, such as New York and Philadelphia, even have multiple old growth forests, added Loeb, who is the author of the book "Old Growth Urban Forests."

There are also different definitions of what constitutes an "old growth" urban forest or even an "urban forest." The U.S. Forest Service, for example, considers an urban forest to be "a continuum or matrix of green spaces with trees or the opportunity to grow trees from rural communities, to green corridors, to inner city parks," said Babete Anderson, Forest Service national press officer. By that definition, there are 138 million acres of urban forest lands in U.S. metropolitan regions, cities and rural communities.

Loeb, though, says it's important not to get hung up on definitions or, even, histories of urban forests. With what appears to be an "old growth" forest, "it’s really hard to be 100 percent confident that selective cutting wasn't done or cutting of some sort wasn't done" in them at some point, he said. But that's not the point, he added. Urban forests, intact or not, old growth or not, "should be protected, should be rehabilitated, and should be celebrated."

A forest restored

A before and after photo of Fernbank Forest's invasive ivy removal efforts The top photo shows a section of Fernbank Forest covered in invasive ivy, and the bottom photo shows the forest after the ivy was removed. (Photo: Fernbank Museum of Natural History)

In celebrating the re-opening of the Fernbank Forest to self-guided tours, Dickerson acknowledged that it can be tricky to compare one urban forest with another. Still, he firmly believes that Fernbank is truly unique among America's urban forests, certainly those on the East Coast. What makes it unique in his eyes? "We've drilled it down," he said, pointing to a combination of concrete data that avoids semantics. That data includes:

  • Soils. Fernbank Forest's topsoil depths range from 12-18 inches. This indicates the forest is relatively undisturbed, which Dickerson said is extremely rare and indicates there has been little to no logging or farming through the ages.
  • The forest is intact. An intact 65-acre old growth forest in a metro area with 5 million-plus people makes it the largest old growth forest in the Piedmont region, which stretches from Alabama up the East Coast to where New Jersey and New York meet.
  • Age of trees. Some trees in the forest, tulip trees and white oaks in particular, are more than 200 years old and some are approaching 300 years. While other urban forests have some very old trees, Dickerson points out that trees of this age are spread throughout Fernbank Forest.
  • Canopy height. The forest has a Rucker Index (average height of the tallest individuals of 10 different tree species) of 138.4 feet. The tallest trees are tulip trees (Liriodendron tulipifera), which soar to 156 feet.
  • Documented heights. Fernbank Forest is also home to some of the documented tallest trees of their species. These include: winged elm (Ulmus alata), the tallest of its species in North America at 128 feet, and the tallest documented southern red oak (Quercus falcata) in the country at 130 feet. The Native Tree Society, the clearinghouse for superlative tree data in North America, has confirmed these heights, Dickerson said.
  • Champion trees. Fernbank Forest has 32 of Atlanta’s champion trees (largest of their species in Atlanta), including the Atlanta champion eastern hemlock, pignut hickory and winged elm.

Dickerson and Fernbank are working with other local greenspaces and nonprofit forest managers and academics (University of Georgia, Emory University and Kennesaw State University at the moment) to share forest management lessons learned and best practices. In time, they plan to share these lessons with wider audiences.

Door-to-door gardening

In the meantime, they've developed a program called the Invasive-Free Yard Program in which Dickerson works with homeowners whose backyards abut the forest fence line to remove non-native, invasive plant species from their yards. Dickerson has visited each of the adjoining homeowners to tell them about the program, point out invasives in their landscapes and explain how these plants damage the forest and why homeowners should care about that damage. "I'll literally go out and tag all of the non-native species and recommend methods and any tools they might need to remove them," Dickerson said. He even gives homeowners lists of native species that they can purchase at local nurseries to substitute for the non-natives.

"It's been a huge success!" he said. "We’ve engaged 12 families so far. Once they have removed their invasives, I'll go back and certify their yards" as free of invasives. As a reward, participating homeowners receive an annual family membership to Fernbank for each year they live up to their end of the bargain. In essence, participating in the program could result in a lifetime membership to the museum. "It's a win-win," said Dickerson. "We are creating a buffer around the forest and in essence extending the boundaries of the forest."

He's only run into resistance on one occasion.

"One neighbor was pretty adamant about keeping a thorny olive," he said. "She removed all of the other invasives but drew the line on this one plant because it was a food and shelter source for birds." No amount of prodding or suggestions for alternative native shrubs would prompt her to remove this last invasive. "But her yard is now 99 percent invasive free," said Dickerson, "and that's a heck of a lot better than it was."