Insects may be struggling to find flowers due to air pollution degrading the chemical compounds responsible for their enticing floral scents.
There has been a growing interest in the potential effects of ‘sensory pollution’ in recent years. This pollution, which arises from human activity, can alter the behavior of wildlife by introducing new stimuli.
Noise pollution has been shown to negatively impact birdsong and has been linked to an increase in whale strandings.
Light pollution has been shown to disorient a range of animals, including migratory birds and sea turtles.
But less is known about how human activity has been affecting scents.
In a study recently published in the Journal Science, a team of scientists based at the University of Washington investigated the effects of anthropogenic pollutants on plant-pollinator interactions.
The researchers focused on pollutants called ozone and nitrate radicals, which are created when vehicle emissions interact with gases in the atmosphere. These pollutants are known to react with the compounds given off by flowers, altering their smell.
The researchers collected compounds released by the Pale Evening-primrose Oenothera pallida, a desert flower found in North America. Both ozone and nitrate radicals broke down the scent compounds, but nitrate radicals did so more completely.
In order to investigate the effect of degraded flower scent on the behavior of the flower’s primary pollinators, the researchers exposed hawk moth species, such as the White-lined Sphinx Hyles lineata, to two different types of flowers: those that emitted the natural scent of the flower, and those that were manipulated to release a degraded scent.
The study found that the primroses that emitted the degraded scents were visited 70% less frequently than the ones producing natural scents. The researchers estimated that the decline in moth visitations could lead to a 28% reduction in the amount of fruit produced by the plants. This decrease in visitation and fruit production could negatively impact hawk moth health and the ecosystem more widely.
According to the team’s models, the distance at which Hawk Moths can sense flowers has shrunk from about 2 kilometres to just a few hundred metres since the industrial revolution.
The study provides further evidence of why we should transition to energy sources that do not involve combustion. Reducing nitrogen oxide emissions would benefit air quality, ecosystem functioning, and agriculture.
Chan, J.K., Parasurama, S., Atlas, R., Xu, R., Jongebloed, U. A., Alexander, B., Langenhan, J. M., Thornton, J. A., Riffell, J. A. (2024). Olfaction in the Anthropocene: NO3 negatively affects floral scent and nocturnal pollination. Science, 383, pp. 607-611. DOI: 10.1126/science.adi0858