02/11/2024
Scientists have found that air pollution and strong scents in some garden products disrupt pollinators' ability to locate flowers. Planting large flowers like Echinacea can help by giving visual cues for the pollinators.
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The scentscape is so critical to the ability of plants and animals to communicate, find food, and mate that I devoted the first chapter of my book Wildscape to it. Now a new study, published today in Science, adds to a growing body of research showing how disruptive human activity can be to this underappreciated aspect of sensory ecology.
Measuring the effects of nitrate radicals, a team in Washington state found that this common pollutant degrades floral scents so much that some nighttime pollinators can’t even locate them. “Some moths couldn’t smell the ‘flowers’ at all,” one of the researchers told Science writer Elizabeth Pennisi. “It’s almost like the moths had COVID.”
Produced when ozone reacts with nitrogen oxide from exhaust and smokestacks, nitrate radicals are more prevalent at night. Conducting field and lab experiments, Jeremy Chan, the paper’s first author, showed that they degrade monoterpenes, the plant compounds that give essential oils their aroma and flavor. He and his colleagues also showed that pollution has reduced the distance a scent can travel by a factor of five, possibly since the Industrial Revolution.
Given what I learned while researching air and odor pollution for my book, I didn’t find the results very surprising. But the study is so comprehensive that scientists are praising it as a leap forward in terms of understanding and validating the problem. “I hope [the work] can help elevate chemical pollution to the same recognition that we give artificial light,” Cal Poly chemical ecologist Sarah Jennings told Pennisi.
I hope so too. And while there might not be very much we can do in our own backyards about broad-scale air pollution, research I described in my book gives us some ideas for how we can mitigate localized odor pollution. Studies conducted by Muhlenberg College professor Jordanna Sprayberry have found that scents in lawn products such as fertilizers and fungicides can disrupt bumblebees’ abilities to find flowers and learn and recognize floral scents. By planting large patches of strongly scented plants—mountain mints, common milkweed, late boneset, native clematis, bee balms—we might help insects cut through the olfactory noise in our home habitats. Flowers with large blooms, such as native sunflowers, rudbeckias, and echinaceas, can also provide strong visual cues that bees use to locate food at short distances.
For more on the latest study on the effect of nitrate radicals on nighttime pollination, see https://www.science.org/content/article/night-pollution-keeps-pollinating-insects-smelling-flowers
For more on Jordanna Sprayberry’s work on localized odor pollution, see her website here: https://spraylab.bergbuilds.domains/
For more on the scentscape and sensory ecology in our own backyards, you can also purchase a copy of my book Wildscape: https://www.humanegardener.com/wildscape/
Photo: Yucca moth on a yucca in my habitat. When adults emerge from the ground in the warm season, they are lured by the strong nocturnal scent of the flowers.
