Sure, air pollution does a whole bunch of nasty stuff: trapping heat, messing with ocean chemistry, and harming human health in countless ways. But have you heard that it might also be ruining romantic encounters between flowers and insects? That’s right, air pollution is playing the ultimate wingman, but in all the wrong ways!
A nifty new study suggests that compounds known as nitrate radicals, tending to party up in nighttime urban air, are reducing the fragrance of the pale evening primrose, thus leading to fewer visits from the ever-so-charming hawk moths – quite the nosy bugs, wouldn’t you agree? Yes, research reported in Science, essentially exposes air pollution as a bad perfume.
Who knew that air pollution could double up as a scent sabotaging menace? This perfumery pollution could throw a wrench into plant reproduction, threatening the production of fruits that feed all sorts of species – including us. It could also harm pollinators who rely on flower nectar for sustenance and are already experiencing global declines.
“We fuss a fair bit about humans being exposed to air pollution, but there’s a bustling system of life also getting a whiff of the same bad air”, says Joel Thornton, the atmospheric chemist version of Sherlock Holmes and co-author of the study. “And we are just starting to realize how deep the rabbit hole of air pollution impacts goes.”
The dynamic trio spearheading the project was Dr. Thornton; his colleague Jeff Riffell, a sensory neurobiologist and ecologist; and their joint doctoral student, Jeremy Chan, who is now having a blast researching aroma theft in the University of Naples.
The study put the spotlight on the pale evening primrose, a plant whose night-owl flowers rely on visits from hawk moths possessing antennas capable of sniffing out an attractive scent from miles away. “They have the sniffing abilities of a canine,” says Dr. Riffell.
To get to the bottom of what drives these moths crazy, the scientists bagged blooms and captured samples of the fragrant air. When the team performed an autopsy of these samples, they found out the signature primrose scent was a cocktail of 22 distinct chemical components.
The researchers had a eureka moment when they found that the moths were particularly fond of a group of compounds called monoterpenes – the same stuff that makes conifers smell like an evergreen forest.
Next up was a DIY session. The researchers used these hot-favorite aromas to replicate the primrose scent from scratch and added ozone and nitrate radicals – both unsolicited gifts from fossil-fuel combustion. They found that the introduction of these pollutants had a brutal effect on the moths’ favorite components, reducing these key allurements by as much as 84 percent. The essence was almost wiped out, noted a stunned Dr. Thornton.
The team then arranged for a faux flower emitting the replicated primrose scent in one end of a wind tunnel. Moths unleashed at the other end often traversed the tunnel to sniff out the flower; presumably to woo it.
Alas, when the fake flower wooed the moths with an air-pollution-tainted fragrance, the moths were far less interested. The number of tobacco hawk moths willing to make the journey to the flower dropped by 50 percent, while white-lined sphinx moths ghosted the flower.
When the researchers took this experiment into the wild, they found that artificial flowers emitting the tainted scent attracted 70 percent fewer moth visitors, which apparently led to a significant dip in primrose fruit production. “The scent–mite relationshipSponsored Product is playing a colossal role in shaping these ecological communities,” noted a reflective Dr. Riffell.
The researchers believe that the findings aren’t just limited to hawk moths and primroses. Many pollinators are sensitive to their beloved monoterpenes. The researchers calculate that pollution has reduced the potential “catchment area” of scent detection distances by over 75 percent across many cities since the preindustrial age.
Polluted Flowers Smell Less Sweet to Pollinators, Study Finds