Ants in Cincinnati and other Ohio cities are scaling multi-story buildings to forage for food on rooftop gardens.
While that may sound pesky, research out of the University of Dayton suggests it's actually a good thing.
Associate Professor of Biology Chelse Prather worked on a study, recently published in Urban Ecosystems, comparing ant communities on nine green roofs and their adjacent ground-level habitats in Cincinnati, Dayton and Columbus. She says she wanted to explore how organisms in cities use man-made green roofs, especially as urbanization reduces the number of natural habitats available.
Prather and her co-author chose to focus on ants because they are ubiquitous. Many species of ants are also native, and they perform important ecosystem functions, like pollination.
“We know that they're an organism that will live in a lot of different places. You catch a lot of them going into your house, so we figured that if any organism was using these green roofs, that ants would be a likely candidate,” Prather tells WVXU.
The researchers looked at ant abundance, nutritional preference and other data on the green roofs and nearby ground habitats across several months.
She says they were expecting to find the ants on the roofs to be similar to ants seen in the top of trees. That wasn’t the case.
“The key finding is that the ant community was the same on the ground and the roof. That was really surprising because they have very different conditions,” Prather says. “The roofs are hotter, they're windier, they're drier — unless they're irrigated, which some of the roofs were.”
The researchers also observed lines of worker ants traveling up the buildings, seemingly going from their nests on the ground to the green roofs.
“A lot of the habitat on the ground was just like turf grass, maybe some planters, but not a whole lot of vegetation; not a whole lot of flowering stuff. Whereas on the roofs there was a lot of stuff that was flowering and ants could eat that potential nectar,” Prather says.
These results indicate that ants are using green roofs as habitat, and the rooftop gardens are able to support similar ant communities as ground-level urban habitats. Ground and roof ant colonies could also be connected, with green roofs serving as foraging sites for the insects.
Prather says native species' use of these intentionally planted rooftop habitats is good news for biodiversity in cities.
“As cities continue to expand, we're always interested in ways to increase biodiversity in cities because they're very different than a lot of natural areas,” Prather says. “One way to do this is these green roof sites.”
Prather adds, green roofs aren’t just useful for ants. During the study, researchers saw butterflies, bees and grasshoppers, as well as ducks and geese that had laid eggs on the plant-filled rooftops.
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