Artificial light at night as a new threat to pollination

• Published in: Nature (London) 2017-08, Vol.548 (7666), p.206-209
• Main Authors: Knop, Eva, Zoller, Leana, Ryser, Remo, Gerpe, Christopher, Hörler, Maurin, Fontaine, Colin
• Format: Article
• Language: English
• Subjects: 631/158/2165; 631/158/2463; 631/158/670; 631/158/853; Agriculture; Agrochemicals; Anthropogenic factors; Breeding success; Climate change; Daytime; Diurnal; Ecological function; Ecosystem services; Environmental aspects; Environmental Sciences; Fruit set; Habitat changes; Human influences; Humanities and Social Sciences; Intensive farming; Introduced species; Invasive species; letter; Light; Light sources; Lighting; multidisciplinary; Night; Nocturnal; Pesticides; Plant communities; Pollination; Pollinators; Reproduction; Science; Terrestrial ecosystems
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature23288

The pollination service provided by nocturnal flower visitors is disrupted near streetlamps, which leads to a reduced reproductive output of the plant that cannot be compensated for by day-time pollinators; in addition, the structure of combined nocturnal and diurnal pollination networks facilitates the spread of the consequences of disrupted night-time pollination to daytime pollinators. Night lights put off pollinators Pollinator numbers are declining worldwide. Alongside factors such as land use change and agricultural intensification, artificial light at night has been proposed to contribute to this loss. Eva Knop and colleagues put this theory to the test in a field experiment in Switzerland. They exposed ruderal meadows to artificial light at night and monitored nocturnal pollinator behaviour. Pollinator visits to plants fell by 62% in the illuminated plots, and fruit production by a focal plant fell by 13%. The findings suggest that artificial light at night, which is spreading at an estimated rate of 6% per year, poses yet another threat to global pollinator health. Pollinators are declining worldwide 1 and this has raised concerns for a parallel decline in the essential pollination service they provide to both crops and wild plants 2 , 3 . Anthropogenic drivers linked to this decline include habitat changes, intensive agriculture, pesticides, invasive alien species, spread of pathogens and climate change 1 . Recently, the rapid global increase in artificial light at night 4 has been proposed to be a new threat to terrestrial ecosystems; the consequences of this increase for ecosystem function are mostly unknown 5 , 6 . Here we show that artificial light at night disrupts nocturnal pollination networks and has negative consequences for plant reproductive success. In artificially illuminated plant–pollinator communities, nocturnal visits to plants were reduced by 62% compared to dark areas. Notably, this resulted in an overall 13% reduction in fruit set of a focal plant even though the plant also received numerous visits by diurnal pollinators. Furthermore, by merging diurnal and nocturnal pollination sub-networks, we show that the structure of these combined networks tends to facilitate the spread of the negative consequences of disrupted nocturnal pollination to daytime pollinator communities. Our findings demonstrate that artificial light at night is a threat to pollination and that the negative effects of artificial light at night on nocturnal p