For humans, street lamps are associated with safer streets. But for nighttime pollinators, the artificial light poses a concentrated danger that, in the grand scheme of things, poses a real danger to the entire planet. That’s the conclusion of an August 2017 study published in Nature.
During daylight hours, all manner of bees and butterflies can be seen flitting about, spreading pollen from flower to flower. But did you know that when the moon comes up and the sun goes down, that’s when the graveyard-shift pollinators go about their job? Moths, beetles, and other night-owl insects come out at night to take over.
Scientists in Switzerland discovered that artificial lighting led to fewer visits from pollinators and reduced fruit production in patches of cabbage thistle. At the time, the researchers were admittedly in the dark about how artificial light affected nighttime pollinators.
So to learn more, they set up mobile street lamps over plots of the plants that had never before been placed under artificial light at night. They also used night vision goggles to watch and catch the pollinators.
The researchers found that the plots grown under the artificial light experienced 62% fewer visitors from nighttime pollinators, compared to plots grown in the dark. Moreover, the illuminated plots saw 29% fewer pollinator species.
Plants that had been covered in pollinator-proof bags produced about the same amount of fruit, regardless of whether or not they were exposed to artificial light.
Even though there are typically more daytime pollinators than nighttime pollinators, the daytime pollinators failed to make up the difference in lost pollination of plants living under artificial light.
Eva Knop, an ecologist at the University of Bern in Switzerland and first author of the study, said:
“These plants were visited frequently by pollinators during the day, too, so this means that in the daytime, pollinators simply can’t compensate for the lost pollination at night.” [2]
As for why nighttime pollinators struggle to do their job, it could be because many nocturnal creatures have sensitive vision which allows them to navigate the landscape in the dark, and bright light disorients or blinds them. Some may be attracted to the light, which distracts them from their natural habitat. Or it could be the exact opposite – light repels the pollinators, and they fly away.
Scientists need to understand what’s going on, though, because the planet’s daytime pollinators are struggling, and the amount of artificial light grows by about 6% every year.
Franz Hölker, a biologist at Germany’s Leibniz Institute of Freshwater Ecology and Inland Fisheries, who was not involved in the study, said:
“Insects are at the center of many food webs, so if you disturb them, there’s an effect on the entire ecosystem.”
Since artificial light – especially street lamps – are kind of a necessity, there’s really no way to completely solve the problem, but there are ways to ease the burden on nighttime pollinators.
Knop says one suggestion is to avoid using LED lights. They emit a high percentage of a certain type of light that is especially harmful to insects. Instead of leaving porch lights burning all night, people can opt for motion-sensing lights. Also, if you can do without decorative lighting, ditch it.
Knop urged:
“Urgent measures must be taken, to reduce the negative consequences of the annually increasing light emissions on the environment.” [3]
Sources:
[1] Nature
[2] The Verge
[3] Mother Nature Network