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Nocturnal Pollinators and Lights at Night

(Editor’s note: These are excerpts from an article in an astronomy related magazine. See full story link below.)

Astronomers are well aware of the adverse effects of light pollution. Less well known, though being increasingly studied, are the possible adverse ecological effects of nighttime lighting on flora and fauna.

A case in point is the very large question of the effects of artificial light at night on nocturnal animals, which actually may be more numerous than diurnal animals, something that is hard for us to recognize, because we are diurnal animals. We are mainly outside seeing nature and wildlife during the day. When we are active at night, with the exception of astronomers, we are inside in front of a computer or television or otherwise preoccupied, having little idea what is taking place in the outside world at night.

A study reported in August in the prestigious journal Nature (vol. 548, p. 206–209, outlines how light at night is harmful for many types of pollinators. Most flowering plants depend on animals for pollination, especially bees, moths, and beetles. A team of researchers in Switzerland put LED street lamps in rural meadows to see their effect on night pollinators. When they looked at the cabbage thistle, they found 62 percent fewer insect visits in the lit meadows. There were 29 percent fewer pollinators than in the control plots without lighting and 13 percent fewer fruits on the cabbage thistle plants.

While this was a limited study looking at a single plant species for simplicity, it suggests there is a relationship between diurnal and nocturnal pollinators. The loss of nighttime pollination was not made up by diurnal pollinators. This work dovetails with other research suggesting light at night can have a significant harmful effect on nocturnal animals and plants. Pollinators may be misdirected or reduced in numbers, and the circadian rhythms of plants are disturbed.

Reproduced with permission from the December 2017 issue of the Reflector magazine (Astronomical League) (

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