The enticing scents emitted by flowers, crucial for attracting insect pollinators, are being compromised by air pollutants, potentially disrupting the delicate balance of ecosystems.
Researchers at the University of Washington in Seattle, led by Jeff Riffell, have shed light on the phenomenon of “sensory pollution,” a consequence of human activity that alters or introduces new stimuli affecting wildlife behavior. While noise pollution has been linked to changes in birdsong and increased whale strandings, and light pollution can disorient various animals, the impact of human activity on animals’ sense of smell has remained relatively unexplored.
In their investigation, the team focused on ozone and nitrate radicals, pollutants generated from vehicle emissions interacting with atmospheric gases. These pollutants react with compounds emitted by flowers, degrading their scents.
By studying the pale evening-primrose (Oenothera pallida), a desert flower native to North America, the researchers found that both ozone and nitrate radicals broke down scent compounds, with the latter being more effective.
To assess the impact on flower pollinators, particularly hawk moth species like the white-lined sphinx (Hyles lineata), the team exposed them to flowers emitting either natural scents or scents manipulated to simulate degradation. They observed a 70% decrease in visitation to flowers emitting degraded scents compared to those with natural scents. This decline in visitation could have implications for hawk moth health and ecosystem dynamics, potentially leading to a 28% reduction in fruit production.
According to the researchers’ models, since the industrial revolution, the distance at which hawk moths can detect flowers has diminished significantly, from about 2 kilometers to just a few hundred meters.
Joel Thornton, another member of the research team, emphasizes the importance of transitioning to energy sources that do not involve combustion to mitigate nitrogen oxides emissions. Doing so, he argues, would benefit air quality, ecosystem functioning, and agriculture.
