Street lamps change the number of times insects visit flowers not only at night, but also during the day. Artificial light at night thus indirectly influences the entire community of pollinators and plants – with unknown consequences for the ecosystem, as researchers from the University of Zurich and Agroscope have shown for the first time.
In the last few years the spread of artificial light has increased massively worldwide. This has negative consequences for the survival and reproduction of nocturnal organisms. Important ecological processes such as the pollination of plants by nocturnal insects are impaired by artificial light – which can have consequences for the yield of agricultural crops and the reproduction of wild plants.
Scientists from the University of Zurich and Agroscope are now showing for the first time that artificial light also affects the pollination behavior of insects during the day. In an experiment they illuminated natural plant-pollinator communities on six natural meadows at night with commercial street lamps. Six other natural meadows remained in the dark. In their analysis, the research team focused on 21 naturally occurring plant species as well as on the insect groups of the two-winged (Diptera), the hymenoptera (Hymenoptera) and the beetle (Coleoptera).
Different interactions depending on the type of plant
“Our results suggest that artificial light at night changes the number of plant-pollinator interactions during the day, depending on the type of plant,” says Eva Knop from the University Research Center on Global Change and Biodiversity at the University of Zurich and Agroscope. Three plant species received significantly fewer pollination visits during the day and another species slightly fewer. Another plant species, on the other hand, was visited a lot more with LED light and another a little more.
Interestingly, the activity of the nocturnal pollinators was also different in artificial light: For example, the forest cranesbill (Geranium sylvaticum) was visited equally often in lighted and dark meadows, but the insects differed: while the two-winged birds avoided the lighting, the beetles were more likely attracted. There were similar trends in two other plant species.
Indirect ecological consequences of light pollution
So far, indirect ecological effects of light pollution have been neglected. “Since insects play a central role in the pollination of cultivated and wild plants and are threatened by habitat destruction and climate change regardless of artificial light, it is important to clarify these indirect mechanisms,” says Knop.
Based on the results, Eva Knop and her colleagues demand: “The ecological consequences of light pollution should be researched more closely and measures developed to prevent negative effects on the environment.” Even if it is hard to imagine populated areas without artificial light, there are possibilities for it: Public lighting in combination with new technologies could be carefully planned and reduced to a minimum.
Featured image: Artificial light at night also changes the number of plant-pollinator interactions during the day. (Image UZH / Agroscope)
Giavi S., Fontaine C., Knop E. (2021) Impact of artificial light at night on diurnal plant-pollinator interactions. Nature Communications, March 16, 2021. Doi: 10.1038/s41467-021-22011-8
Provided by University of Zurich