The night sky is lit up by blinding electric lights that can interfere with the flight of birds. Light pollution can trap the birds in areas of bright light, thereby interfering with the compass orientation in migratory bird species. Human exploitation of nature has destroyed the natural equilibrium and disrupted essential natural processes across the world. One disrupted process is insect pollination.
Plant-pollinator relationships depend on the pollinators being able to find the plants. Therefore, any factor that disturbs the attraction between them will decrease the frequency and quality of these interactions. Pollinators are drawn to flowers by visual and chemical cues that humans might overlook. The color, shape and form of the flower are visual cues that guide insect pollination. For instance, bees are drawn to mountain pansies by how much ultraviolet light their blue petals reflect. Changes to ozone levels are resulting in a reduction in pedal size, which also changes how much ultraviolet light is reflected by the petals. These changes affect the perceptions of certain insects such as flies and butterflies, and make it harder for them to pollinate. Visual cues only attract pollinators during the daytime. At nighttime, animals solely rely on odor and chemical cues to locate flowers. Many scientists have carried out research on the chemical attractions in the plant-pollinator relationships.
Atmospheric scientist Joel Thornton, alongside Jeff Riffell, a sensory neurobiologist and ecologist, and their joint doctoral student, Jeremy Chan, conducted a study on the attraction between a pollinator and a night blooming flower. Specifically, they researched the interaction between the pale evening primrose and their pollinator, hawk moths. The team collected scent molecules from the flower and released the scent molecules in a wind tunnel with hawk moths. They observed that the moths were attracted to the scent of the pale evening primrose, specifically, to compounds named monoterpenes, which are also responsible for the fresh and evergreen smell from conifers. To test the effects of pollutants on chemical attraction, they added ozone and nitrate radicals to the wind tunnel. Ozone forms in the presence of sunlight, thus, is more abundant during the day, while nitrate radicals get degraded by sunlight and are more abundant at night. The results show that with exposure to ozone, the concentrations of monoterpenes dropped by 30 percent. Nitrate radicals proved even more damaging than ozone and an 84 percent drop in monoterpene levels.
The scientists also wanted to test their findings in the wild. They did this by planting a field of real and fake flowers. The artificial flowers released fragrances that were degraded by nitrate radicals. The team found that the fake flowers received 70 percent less pollination than the real flowers. “The flowers only bloom once per night,” Riffell said. “Without their pollinators, there can be a huge change in the plant community.”
However, our knowledge of the effects of pollutants on plant-pollinator attractions is still limited.“We’re at a very early stage of really understanding how big a deal it is,” Robbie Girling, a chemical ecologist at the University of Southern Queensland said. Studies provide an estimation of 75 percent of scent degradation since preindustrial times. Therefore, the decrease in plant-pollinator attractions caused by air pollution is harmful to the equilibrium of local ecosystems, potentially posing a threat to humans.