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American Society of Landscape Architects


July 2007 Issue

A Fine and Fancy Ramble
Landscape architects help bring a venerable zoo landscape—and its inhabitants—into the 21st century.

By Linda McIntyre

 Fine and Fancy Ramble Walter P. Calahan

Even within the rarefied niche of zoo design, the National Zoo in Washington, D.C., is a special case. It’s a historic Olmsted landscape, set within the larger historic landscape of Rock Creek Park. It’s part of a big and sometimes controversial national public agency, the Smithsonian Institution. And it’s home to a few A-list animal celebrities: giant pandas Mei Xiang, Tian Tian, and their adorable offspring, Tai Shan.

Now the pandas and six other endangered or threatened species—sloth bears, fishing cats, red pandas, clouded leopards, small-clawed otters, and a Japanese giant salamander—have new homes along the zoo’s new Asia Trail, which wends its way around almost six acres near the zoo’s main entrance. The zoo management sees the Asia Trail, with its environmentally friendly design features and detailed attention to the animals’ habits and preferences, as the first step in a planned 10-year revitalization effort aimed at improving animal care, habitat development, and sustainability as well as the visitor experience. “We want to refresh and replace the older exhibits and bring them up to the Asia Trail standard,” says National Zoo Director John Berry.

The Asia Trail has only been open since October 2006, but judging from its inhabitants—by turns frisky or relaxed, but apparently thriving—and the crowds even during this year’s chilly early spring, as well as the squeals of delight and murmurs of “awesome” in the background of Landscape Architecture’s recorded on-site interviews, it’s not too early to label it a success for the animals and their human visitors. For the design team, the project was an opportunity to collaborate across disciplines—way across.

“We learned a lot about animals, and we had to do a lot of homework,” says Warren Byrd, FASLA, principal in charge of the project for the Charlottesville, Virginia-based landscape architecture firm Nelson Byrd Woltz. “But we really had to rely on others who knew their stuff.” Everyone to whom Landscape Architecture spoke for this article—the landscape architects, the architects, the rockwork designers, the zoo staff—spoke of the “incredible collaboration” involved in this project, necessary in part because everyone was working to please “clients” who couldn’t readily communicate their own views. “We couldn’t just order [components of the exhibits] from a catalog,” observes Asia Trail Curator Tony Barthel. “We had to guess.”

Bear Necessities

The National Zoo was founded in 1889, and its plans were drawn up by Frederick Law Olmsted, conservationist William Temple Hornaday, and Samuel Langley, the third secretary of the Smithsonian Institution. The plan had to be modified owing to conditions on the site and today, says Mary Williams Wolf, project landscape architect for the Asia Trail, virtually none of the original alignment of the Olmsted Walk, the main path through the zoo, is intact. “The general route is the same but not the layout. The sinuous curves responding to the topography are no longer as evident,” she says.

In the 1960s, the zoo expanded its mission to focus on threatened and endangered animal species. One of those endangered species, the giant panda, has long been a star attraction for zoo visitors. The zoo’s original plan for improvement, conceived at around the time of Mei Xiang and Tian Tian’s arrival in 2000, was intended to shine a spotlight on the exotic ursine celebrities with an expanded panda habitat. A big new visitors center building was also envisaged. But after Lucy Spelman, a veterinarian, took over as the zoo’s director, the plan’s focus shifted to animal health and enrichment and the institution’s conservation mission rather than an attraction for visiting humans. “I plan for each of our new major exhibits to be well-designed physical places at the zoo, for the animals and our visitors, as well as the focus of much broader conservation programs,” she said in 2001.

Nelson Byrd Woltz had worked with Washington’s Chatelain Architects and others on the original concept. After the zoo decided to go forward with the new animal-centered project, Chatelain and Nelson Byrd Woltz returned as well. These firms could not draw on their experiences designing other zoo exhibits—this was the first such project for both.

Not that they viewed this as a problem. “It was a great challenge,” says Byrd. “I like nothing more about being a landscape architect than the diversity of what we get to do. We didn’t realize fully up front what we were getting into, but a lot of us love animals, and we’ve done a lot of work on wildlife habitats.”

“The National Zoo was interesting to us because it’s a public park,” says Wolf. “We would not have been as interested in working on a ‘theme parky’ zoo. A lot of ethical issues were at stake, and a real commitment was needed. We went all out and tried to learn as much [about these animals] as we could.”

That learning included visits to many zoos in the United States and abroad, such as the Bronx Zoo, at which the natural setting plays an important role, and the Rotterdam and Emmen zoos in the Netherlands, which are known for innovative animal enrichment and design. The landscape architects also did extensive research on the animals and their native habitats and worked closely with the zoo staff. “The zoo researchers and scientists provided great information on animal habitats from their personal experiences and travels,” says Wolf. “Curators, keepers, maintenance staff, and horticultural staff attended most meetings and provided much advice from hands-on experience with the animals. They gave us tours of animal holding areas, pointing out what was successful and what was not.” The zoo staff also provided minimum standards for the dimensions of yards and holding areas, based on guidelines set by the Association of Zoos and Aquariums; the designers exceeded those guidelines in all of the Asia Trail animal yards.

Two of Nelson Byrd Woltz’s team members, says Wolf, brought special expertise to the project. Sara Myhre, who was a project landscape architect and comanager for the design of the Asia Trail, previously worked for The Portico Group in Seattle, a landscape architecture firm with considerable experience in zoo design. Hara Woltz has an academic background in biology as well as landscape architecture and did extensive research on plants for the yards that were native to the animals’ habitat and would provide opportunities for shade and climbing as well as other enrichment. Woltz has now completed an advanced degree in conservation biology.

Nelson Byrd Woltz spent about two and a half years designing the Asia Trail and two years on construction. Before that process began, the firm spent more than a year working on various concept plans that evolved into the Asia Trail. In the early stages of the project, says Wolf, a lot of ideas were bandied about, including having the zoo’s sloth bears and pandas share habitats. Then, she says, the design team began to examine the possibility of an Americans with Disabilities Act-compliant path running between a new sloth bear exhibit—their previous decrepit home was one of the zoo’s oldest exhibits—and the panda habitat.

Asia was an obvious focus for the design effort, not only because of the pandas but based also on the needs of those less-flashy sloth bears, which hail from the Indian subcontinent. It was also an opportunity to display species such as the red pandas that were bred at the zoo’s rural conservation research center.  

Happy Trail

Making the trail and exhibits accessible to visitors was a priority for the designers and a particular challenge given the constraints of the site, with a grade change of about 60 feet from start to finish. “The trail is so tight,” says Wolf. “We probably could not have met ADA requirements if it had been one foot shorter.” Construction of the Asia Trail also enhanced the accessibility of nearby exhibits—reconstructed paths leading off the new bridge at the edge of the panda pavilion make the zoo’s popular Bird House easily accessible for the first time to people with disabilities or those pushing strollers. To get the most usable space and visual oomph out of the relatively small site and to reduce the project’s built footprint, holding areas for the animals, used at night and in cold weather, and mechanical systems were located underneath elevated areas.

The layout of the trail was designed to respect Olmsted’s original intent—“sinuous curves and gentle slopes, allowing a leisurely experience,” says Wolf. It also lets visitors see the animals from different heights and angles. A two-level “ring” around the panda yard allows a lot of people to see the popular giant pandas—and the playful, raccoonlike red pandas, who like to climb—at the same time. The designers also seized on grade changes as opportunities to soften the design with more plants and demonstrate sustainable techniques. The otter house, a last-minute addition to the project, has a green roof that is easily visible to visitors walking along the trail.

Several of the exhibits are fronted with glass, allowing visitors to get up close and personal with the animals, a phenomenon that Berry says is his favorite aspect of the Asia Trail. “We knew the pandas did not have a problem with people being close to the glass [front of the exhibit],” says panda curator Lisa Stevens, “so that was worked into the designs. It helps to give visitors the sense of being immersed in the pandas’ habitat.” Similarly, keepers reported that the fishing cats were not shy about scooping out their prey from a transparent tank, so their exhibit was designed to give visitors a close-up view of the hunt.

One of the more unusual barriers, located around the sloth bear habitat, was designed by Coyle & Caron (formerly known as Rampantly Creative), a landscape architecture and habitat design firm located outside Boston that also created the Asia Trail’s rockwork. It’s a series of tall steel rods sunk deep into the ground and painted in green and tan tones to evoke the look of bamboo. Real bamboo is planted among the rods to soften the look of the steel. “We hope that as the bamboo fills in, it will blend in with the artificial barriers,” says Wolf. “It’s a very effective way to hide the boundaries of the exhibit, which is a hard thing to do.” She adds that this barrier could not be used in the panda area, since pandas have opposable thumbs and so can climb, grab, and dislodge more effectively. So far, the barrier is holding up well to the weather and the bears, and its whimsical functionality works well both practically and aesthetically. 

Flora and Fauna

Each exhibit makes use of different features and plants, depending on the animals’ needs and preferences. A lot of trees suitable for climbing were planted in the panda habitat, and the space’s rolling terrain and rocks elicit a lot of playful behavior among all three bears, according to Stevens. The sloth bear habitat was designed to encourage the bears’ propensity to dig for insects and worms. “The variety of substrates—the rockwork, trees, hills, and pools—is a big success,” says Barthel. “Part of it is the natural terrain, but a lot of the nooks and crannies were intentionally created. We actively manipulate their environment, hiding things and scattering food around, letting the bears interact with their environment as they search for it.”

Water features were specially designed for each animal. In the panda habitat, Stevens says that the zoo staff had determined that the bears prefer playing in shallow water, so their new space was designed with shallow pools, a waterfall, and a stream. Misters were built into the walls to keep the bears cool during hot weather as well as to evoke the misty Asian landscape.

Plants were also selected for animal enrichment. In the sloth bear habitat, blackberries, blueberries, raspberries, and sumacs were planted to provide foraging opportunities. The sloth bears took full advantage, wolfing down not just the berries but entire plants. More fruiting shrubs have been planted. In addition to living trees, deadfall (fallen branches and the trunks and limbs of dead trees) from all over the zoo is strewn about the exhibits to give the animals more opportunities to play and climb.

Other animal-related considerations affected plant choice. Rhododendrons can be toxic to animals, but they are common in the animals’ native habitats, and the toxins and leathery leaves make them unpalatable to most herbivores. “There was a lot of back and forth about whether to use them in the exhibits,” says Wolf. “In the end the director felt it was too risky. We had to pull them out and scramble to use leftover plants and whatever the nursery contractor could get for us. We would have liked to have more time if it needed to be redone.” She adds somewhat ruefully, “It was a real bummer—those rhododendrons looked great!” The landscape architects were unhappy with some of the replacements, such as the forsythias in the red panda yard—they wanted more evergreens—but they have been told that the recommended replacements will eventually be planted.

Despite the separate plant lists and features for each habitat, the trail hangs together as a coherent whole. While elements such as water features and rockwork vary from one exhibit to another, their repeated use throughout the Asia Trail gives it a distinct look and feel. The plant palette includes many varieties of bamboo (their runners are restrained with three-foot-deep heavy plastic barriers) as well as widely used Asian species such as cryptomeria, Japanese maple, and ginkgo; beautiful and less-common species such as stewartia, dove tree, and paperbark maple; and exotic-looking but U.S. native species such as catalpa and bigleaf magnolia. Byrd, who studied horticulture as an undergraduate and has taught University of Virginia landscape architecture students about natural systems and plant communities for more than 20 years, welcomed “the opportunity for us to explore and to push diversity [in the planting design] to reflect the landscapes of both Rock Creek Park and Asia.” The landscape architects reviewed their plant lists with the zoo’s horticultural department to make sure they were acceptable in terms of maintenance, and Berry says the staff is carefully monitoring the plants to make sure no problems with invasiveness arise.

While the zoo management describes the Asia Trail as its “most significant improvement in nearly 40 years,” it sits comfortably in the larger landscape. The project team worked to preserve as many of the site’s existing trees as possible, says Jon Penndorf of Chatelain Architects. “The mature trees helped to anchor hillsides, so there was less soil erosion during construction. They provide shade for the animals and visitors in hot weather.” The contractors, he says, did a great job of protecting those trees, staking out root zones and doing a lot of hand digging during construction.

Talk to the Animals

The period during which the Asia Trail was designed and built was a time of upheaval for the zoo, not all of it a result of construction. Among these challenges were several high-profile animal deaths and a change in the zoo’s leadership. Even the birth of Tai Shan presented some complications. “We had to shut down construction around the panda yards,” says Penndorf. “When we started up again, we had to have weekly sound tests to make sure the equipment we were using wouldn’t bother them. But the contractor was very cooperative, and the pandas didn’t seem to mind!” Stevens reports the pandas are now very happy with their expanded and redesigned space, and during one of Landscape Architecture’s visits to the zoo, Tai Shan was leaning against the glass contentedly munching bamboo while a throng of enraptured children looked on.

The other species along the Asia Trail also seem well pleased with their new homes, after an inevitable period of adjustment. “The sloth bears took a little time to embrace the exhibit,” says Barthel. “They were slightly overwhelmed at first. We thought the glass might be a problem for them. But they were fine as soon as the first crowds came and they realized it was a secure, solid wall.”

The design team could not anticipate everything—just before Christmas, clouded leopard Mook or her male colleague Tai chewed a hole in the copper wire mesh enclosing their habitat, and Mook decided to go for a stroll. She didn’t go far—she was found lounging near the enclosure—but the zoo management closed the exhibit until a stronger wire material was installed.

‘‘The project was extremely demanding,” says Byrd. “At some points we had six people on the project full-time, and coordinating among so many people was daunting.” But he and his colleagues at Nelson Byrd Woltz have received the ultimate compliment for their work at the National Zoo—they are designing a habitat for the 40 pandas at the Wolong Giant Panda Reserve in China, where Mei Xiang and Tian Tian lived before moving to Washington. Wolf, who has been to Wolong twice for that project, says that the sites are quite similar—valleys with steep rocky slopes—though she’s happy to have a little bit more space to work with. She does wish she had been able to visit Wolong before working on the Asia Trail. Seeing it now, though, she says, “confirms for me that we were on the right track.”

Sidebar: Rock On

Rockwork—for animal enrichment and containment, aesthetics, and slope stabilization—was a top priority for the National Zoo project. “Our original goal was to use natural stone as much as possible,” says Mary Wolf. “But that wasn’t feasible with the steep slopes on the site.” To ensure that the artificial rockwork could blend with a landscape built on the striking Piedmont stone of Rock Creek Park, the design team engaged Coyle & Caron, who had done a lot of rockwork for zoos in the United States and abroad.

“Our involvement began after Nelson Byrd Woltz had developed a ‘massing footprint’ for the rockwork, which was part of a larger site concept and visitor sequence they developed with Chatelain Architects,” says Sally Coyle, ASLA. Typically, says Coyle, rockwork design extends only to the massing footprint. “Its character and three-dimensional qualities are left to the contractor to design during implementation with little thought given to an overall coherent geology,” she says. “We were capable of ‘giving life’ to the rockwork and creating a well-considered geological thread that would enhance and reinforce the site and thematic concepts,” including Asian geology and the natural landscape of Rock Creek Park.

After reviewing the design program and geological considerations with the client, Coyle and partner Quentin Caron sculpted detailed models onto bases commissioned by local fabricators out of high-density foam. “We construct our design in a way that can be translated by us into CAD, and both the models and the CAD drawings are used for the construction process,” says Coyle.

The design team also required the general contractor to hire an art director, Karen Phillips of Tucson’s Habitat Design Studio. Having the on-site art director “meant that the models were accurately interpreted and the characteristics we desired were well communicated to the artists,” says Coyle.

Putting so much effort and resources into the rockwork paid off—it’s hard to differentiate between real and constructed rock. Even obviously constructed pieces, such as the termite mounds in and around the sloth bear habitat, blend in with the natural boulders on the site and the locally quarried Carderock stone cladding the exterior of the exhibit.

But the rockwork doesn’t just sit there looking pretty. “The terrain of the site meant that in some cases the rockwork had to be engineered for both temporary slope stabilization requirements during construction and permanent structural stability,” says Coyle.

Some of the rocks, designed after extensive consultation with the zoo staff, also help the animals stay comfortable during Washington’s cold winters and hot, sticky summers. The sloth bears, with their tropical origins, enjoy rocks with radiant heating, while the pandas like to recline on their water-chilled “cool rock” at the front of the exhibit, part of which extends outside the habitat into the visitor area. A “hot beach” surrounds the otters’ glass-fronted pool. 

Perhaps the most innovative rockwork—and certainly the most fun—is found at some of those termite mounds in the sloth bear yard. Coyle & Caron, in close consultation with the zoo staff, fitted the mounds with tubes that run through to the exterior wall of the exhibit. Keepers can insert another tube from outside the exhibit, allowing the bears to use their powerful snouts to suck food from the hands of visitors in the adjacent stone amphitheater.

Coyle & Caron also designed artificial tree stumps, logs, and mangrove roots for additional animal enrichment.  “Changes were made in the field by the art director in consultation with the zoo staff based on field conditions such as conflicts with underground utilities and a refinement of the enrichment concepts,” says Coyle. “The follow-through on these changes and the final form of the features were handled by the art director and the zoo, so in the end this was more of a collaboration.”

Project Credits

DESIGN TEAM Landscape architecture: Nelson Byrd Woltz Landscape Architecture, Charlottesville, Virginia (Warren Byrd, FASLA, principal in charge; Mary Williams Wolf, project manager; Sara Myhre, project manager; Hara Woltz; Evan Grimm; Sophie Johnston; Matt Whitaker; Eugene Ryang; Breck Gastinger; Michael Stouse). Architects: Chatelain Architects, Washington, D.C. (Leon Chatelain, Stuart Billings, Jon Penndorf). MEP: Ove Arup & Partners, New York. Structural engineers: McMullan & Associates, Vienna, Virginia (Doug Bond, Colleen Nasta). Civil engineers: William H. Gordon Associates Inc., Chantilly, Virginia (Scott Peterson, Laura Miller). Rockwork design and habitat consulting: Rampantly Creative (now called Coyle & Caron llc), Scituate, Massachusetts (Sally Coyle, ASLA, Quentin Caron). Rockwork engineering/cable structure engineering: Weidlinger Associates Inc., Cambridge, Massachusetts (Peter Quigley). Trail lighting design: D. Gilmore Lighting Design Inc., Rockville, Maryland (Debra Gilmore, Gaspar Glusberg). Animal pools and streams engineering: Siska-Aurand, Norfolk, Virginia (Doug Aurand). Irrigation design: Irrigation Research, Richmond, Virginia (Bill Rogers). CONSTRUCTION TEAM General contractor: Hensel Phelps Construction Co., Chantilly, Virginia (Karen Phillips, Habitat Design Studio, art director). Construction manager: Bovis Lend Lease/Smithsonian. Smithsonian Institution construction: Marc Muller, Karen Swanson. Rockwork construction: Cemrock, Tucson, Arizona. Landscape contractor: Ruppert Nurseries, Laytonsville, Maryland. EXHIBITS Smithsonian National Zoological Park Exhibits Department (Susan Ades, head of Exhibit and Planning Design; Kara Blond, Technology and Communications; Ken Stuart, Exhibit Design).

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