Insects may have a hard time finding flowers because air pollutants are breaking down the chemicals responsible for the flowers' attractive scent.

“In recent years, there has been increasing interest in 'sensory pollution,'” he says. Jeff Riffel at the University of Washington in Seattle. This pollution resulting from human activities can change wild animal behavior by changing or introducing new stimuli, he says.

For example, we know that noise pollution affects bird songs and may be linked to an increase in whale strandings. Light pollution, on the other hand, can disorient a variety of animals, including migratory birds and sea turtles.

However, little is known about how human activities affect animals' sense of smell. Riffel and colleagues therefore investigated the effects of anthropogenic pollutants on plant pollinators.

They focused on ozone and nitric acid radicals, which are pollutants produced by the interaction of vehicle exhaust and gases in the atmosphere. Both are known to react with compounds emitted by flowers to change their scent.

The research team discovered pale evening primrose (evening primrose), a desert flower found in North America. Both pollutants degraded aroma compounds, but nitrate radicals did so more completely.

To study whether this led to changes in the behavior of the flowers' main pollinators, the researchers exposed species of hawk moths, including the hawk-moth sphinx.Hyles Lineata), flowers that emit a natural floral scent, or flowers that have been engineered to emit a degraded scent.

Primroses that emitted degraded scents were visited 70% less frequently than flowers that emitted naturally delivered scents. This decline in visitors could affect the hawkmoth's health, Riffel said. Researchers estimate that reduced moth visitation could reduce the amount of fruit plants produce by 28 percent, potentially having ripple effects on the broader ecosystem.

The researchers' models show that since the Industrial Revolution, the distance at which hawk moths can detect flowers has shrunk from about two kilometers to just a few hundred meters.

“This is another reason why we need to switch to energy sources that do not involve combustion,” say team members. Joel Thornton, also at the University of Washington. “Reducing nitrogen oxide emissions would be a win not only for air quality, but also for ecosystem function and agriculture.”