Artificial light disrupts plant pollination, even during the day

Artificial light is known to disrupt ecological processes such as the nighttime pollination of plants by nocturnal insects, which could be detrimental to plant reproduction and agricultural crop yields. In a new study from the University of Zurich, experts have demonstrated that artificial light at night also interferes with insects’ pollination behavior during the daytime.

“A ‘luminous fog’ of artificial light at night is enveloping the locations inhabited by humans, with about 18.7% of the world’s terrestrial surfaces (excluding Antartica) currently being exposed to it,” wrote the researchers. “Furthermore, the area experiencing direct emissions from artificial light sources is estimated to expand at about 2–6% per year while already illuminated areas become brighter at a similar rate.” 

“In addition to effects on the physiology and behavior of organisms with consequences for mortality, reproduction, species abundance, and community composition, artificial light at night affects species interactions and ecosystem functioning.”

For the investigation, the experts used commercial street lamps to illuminate natural plant-pollinator communities overnight on six natural meadows, while six other natural meadows were left dark. The research analyzed the interactions of 21 naturally occurring plant species and their pollinators.

“Our findings indicate that artificial light during the nighttime alters the number of plant-pollinator interactions during the daytime, depending on the plant species,” explained study co-author Eva Knop.

For example, three plant species received significantly fewer pollinator visits during the daytime after LED illumination. By contrast, one plant species received substantially more pollinator visits.

Nocturnal pollinator activity was also found to vary in the presence of artificial light. For example, woodland geraniums received the same number of pollinator visits in illuminated and dark meadows, but not by the same insects. Dipterous insects reduced their visits to plants that were lit up during the night, and beetles tended to visit more frequently. 

“Since insects play a vital role in pollinating crops and wild plants and are already endangered by habitat destruction and climate change regardless of artificial light, it is important to study and clarify these indirect mechanisms,” said Knop.

The study authors are calling for the ecological impact of light pollution to be researched more thoroughly and for actions to be devised to prevent adverse effects on the environment. 

“We conclude that the effect of artificial light at night on plant-pollinator interactions is not limited to the night, but can also propagate to the daytime with so far unknown consequences for the pollinator community and the diurnal pollination function and services they provide,” wrote the researchers.

The study is published in the journal Nature Communications.

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By Chrissy Sexton, Earth.com Staff Writer