Air pollution doesn’t always mean hazy brown skies, since some pollutants are invisible–like ozone, which forms when vehicle emissions react with hot air on summer days. It’s a health hazard, but you might not know it’s there. A new “ozone garden” is a reminder: Each of the plants inside are slowly damaged from the gas, and visibly show how polluted a city really is.
“Damage to plants is the primary way to actually see the effects of ozone,” says Danica Lombardozzi, a postdoctoral researcher at the National Center for Atmospheric Research in Boulder, who created two ozone gardens there with fellow postdoc Kateryna Lapina. Over time, the plants in the gardens–milkweed, snap bean, potato, and cutleaf coneflower–will start to get black spots from pollution.
“The plants will only show signs of ozone damage if ozone levels are high for periods of time, and seeing the damage on plants will help people to realize that pollution levels have been high for some time,” Lombardozzi explains. “People might not always understand that ozone is a chronic problem because breathing problems will come and go as ozone concentrations go up and down.”
Of course, in many cities, you can also look at an air-quality report online. But ozone isn’t measured everywhere. “I do think it would be useful to have a network of gardens across the country,” she says. “Bio-indicator gardens could give us an idea of where we might need to better monitor ozone pollution in the future.”
Along with health impacts like making asthma worse, ozone can also make it harder to grow food on farms. “Ozone can reduce crop yields, so when bio-indicator gardens are planted on farms and show signs of ozone pollution, they can help farmers understand if ozone is one factor that might impact their crop yield,” Lombardozzi says.
It’s also possible to plant an ozone garden at home–though a bit tricky if you’re not an expert, since some other problems, like drought, can also make leaves start to turn black.
Lombardozzi hopes seeing the gardens might inspire people to take some action to help reduce local ozone, like trying not to drive in the hottest part of the day. “There are many things that people can do to reduce ozone pollution,” she says. “Many of them are small changes that can have a big impact.”