Ecology: Light at night affects pollination

Artificial light at night may be a threat to pollination, according to a study published online in Nature this week. The authors suggest that the negative effects of artificial light at night on nocturnal pollination could spread to daytime pollinator communities.

Artificial light at night is spreading globally at an estimated rate of 6% per year and has been shown to affect the physiology and behaviour of various organisms. However, the effect on communities, such as pollinators, and on pollination has been unclear.

Eva Knop and colleagues conducted experiments in 14 independent ruderal meadows (plots of disturbed land), in which 7 plots were exposed to artificial lighting at night using mobile street lamps. The authors monitored plant-pollinator interactions in each of the plots and found that there was a decrease of 62% in the number of visits by pollinators to plants in the illuminated plots. They also found that there was a 13% reduction in the number of developed fruits produced by the cabbage thistle (Cirsium oleraceum) in illuminated plots compared to control plots, even though the plants received a similar number of visits from pollinators that were active during daylight.

The authors conclude that pollination services provided by nocturnal pollinators are disrupted in the vicinity of streetlamps, and that this leads to a reduced reproductive output in plants, that cannot be compensated for by pollinators during the daytime.