Higher Ground

The next time you’re at Lincoln Park Zoo, look up. You might just see a glimpse of one of the zoo’s green roofs. We’re betting you didn’t even know they existed.

As part of the zoo’s commitment to sustainability, green roofs have been installed at 18 different sites here on zoo grounds. Also called “vegetated” or “living” roofs, green roofs lie over traditional building coverings and consist of a waterproofing membrane, a growing medium (think soil), and plants.

Why Green Roofs?

Green roofs provide many benefits, including the management of water runoff from surfaces like parking lots, streets and rooftops—an especially important consideration in an urban environment like Chicago, where a proliferation of paved walks prevents precipitation from being absorbed into the ground. Rain and snow can drain into nearby bodies of water like Lake Michigan, taking pollutants with them and damaging local water quality. Green roofs slow the flow of water from a roof by up to 65%, keeping nearby bodies of water cleaner.

Green roofs also make the zoo more energy-efficient; they cool buildings down, provide shading, and help regulate interior temperatures. On top of that, they can reduce the effects of urban heat islands, caused by the fact that concrete and asphalt absorb and re-emit heat, warming up cities. This results in extra energy consumption and heat-related problems.

Ultimately, green roofs just make a lot of sense: they provide additional habitats for plants and animals (especially pollinators like insects), and last longer than regular roofs. Of course, it doesn’t hurt that they add beauty to zoo grounds, even though most visitors don’t even know they exist. Here in the Lincoln Park neighborhood, the skyline view from some these roofs is pretty spectacular.

Green on Grounds

Not all of the green roofs are viewable from ground level, but you can see a few of them while you’re walking around. For example: look up from the viewing windows at Pepper Family Wildlife Center to view some of the green sites atop that building. You can also visit Bird’s Eye Bar & Grill and look south across Main Mall for an even better view of these spaces.

Other green roofs at the zoo are located at Regenstein Macaque Forest, Hurvis Family Learning Center, Robert and Mayari Pritzker Penguin Cove, Walter Family Arctic Tundra, Searle Visitor Center, Pritzker Family Children’s Zoo, Regenstein Center for African Apes, and Pepper Family Wildlife Center. If you’re keeping track, that means they’re pretty much all over the zoo, and some buildings have multiple roof garden areas.

All told, the zoo features more than 33,000 square feet of green roof space, a result of careful planning from the get-go. Green roofs require a certain amount of engineering to place properly, along with permits from the city and other requirements.

“The green roofs at Lincoln Park Zoo provide many benefits including improved air quality, building insulation, and improved storm water management. These roofs are one way the zoo shows its commitment to sustainability,” says Director of Horticulture Katrina Quint.

Maintenance Moxie

Members of the Horticulture staff must be fairly nimble to get to some of these green roofs. A few can only be accessed by tall ladders, and some are also restricted when the animals are out on exhibit or during certain seasons when animals, like the polar bears, are denning. This means the plants that grow on top of the buildings have to be able to fend for themselves, to some extent. While many of the roofs have irrigation systems, zoo staff may only be able to access the roofs three to four times a year.

Despite their height, though, green roofs do get attacked by weeds. Juniper, clover, sumac, solidago, mulberry dandelions, dogweed, crabapples, and other types of unwanted vegetation can easily make their way onto green roofs. That means that when Horticulture staff are able to access the roofs, they will do a certain amount of weeding to ensure the weeds aren’t crowding out the intended plantings.

Plenty of Plants

Because most green roofs can’t have a deep soil layer, only certain types of plants thrive in these environments. The plants of choice are low-maintenance perennials, like drought-resistant euphorbia and sedum.

“The plants chosen for green roofs thrive in these spaces. Sedums and prickly pear cacti are shallow-rooted plants that require little water to survive and are ideal for use in green roof systems,” Quint explains.

Sedum is a genus of green succulents with clusters of star-shaped flowers. Prickly pear cactus are one of the only cactus species native to Illinois.

Some roofs, like the ones at Pepper Family Wildlife Center and Regenstein Macaque Forest, are able to support a slightly deeper soil—up to 8 inches. This provides Horticulture staff with a little more freedom in what to plant, although these places also require more maintenance as a result. Here, you’ll find grasses like prairie bluestem among others.

“On our semi-intensive roofs we are able to grow plants with larger root systems, like prairie dropseed and purple coneflower, which also allows them to be seen from the ground,” Quint says.

These plants may not be as visible to zoo guests but they represent the zoo’s commitment to creating a more sustainable future that’s not limited to our animal care and conservation initiatives. It’s one more way the zoo makes Chicago a better place—even if no one can see it.

Horticulturalist Katrina Quint discusses the green roofs in this short video: