Artificial light disrupts nocturnal pollination and leads to a reduced number of fruits produced by the plant. This loss of night time pollination cannot be compensated by diurnal pollinators. The negative impact of artificial light at night on nocturnal pollinators might even propagate further to the diurnal community, as ecologists of the University of Bern were able to show.
The number of bees and other diurnal pollinators is declining worldwide – due to diseases, introduced parasites, pesticides, climate change and the continuing loss of habitats. Now, Eva Knop's team from the Institute of Ecology and Evolution at the University of Bern, shows for the first time, that nocturnal pollinators can be affected by artificial light leading to a disruption of the pollination service they provide.
Test setup used to investigate the impact of artificial light on the nocturnal pollination.
© UniBE/Maurin Hörler
"So far, nocturnal pollinators have been largely neglected in the discussion of the worldwide known pollinator crisis", says Knop. However, there are numerous nocturnal pollinators, and they play an important role for plants, as the study in the Bernese Prealps shows.
Knop’s team found out, that flowers on meadows which were experimentally illuminated with street lamps are visited around two thirds less frequently by pollinators, than those that were on meadows without any light sources in the vicinity. This has an effect on the fruit set, and therefore the reproduction of plants. The study has now been published in the magazine "Nature".
Loss of nocturnal flower visitors
In the last 20 years, the light emissions have increased by 70%, particularly in residential areas. "As it is possible that light sensitive insects have already disappeared in regions with high levels of light pollution, we conducted our study in the still relatively dark Prealps", explains Knop.
The researchers could show that during night a total of almost 300 insect species visited the flowers of around 60 plant species on ruderal meadows without any artificial light sources in the vicinity. Interestingly, on meadows with experimentally set up street lights, the nocturnal pollination visits were 62% lower than in the unlit areas. The LED lamps used, are used as standard for public street lighting.
Consequences for biodiversity
This loss of nocturnal flower visitors leads to a reduction of the fruit set of plants, as the researchers have proved for the first time, with the example of the cabbage thistle (Cirsium oleraceum). The pale flower heads of the cabbage thistle are a rich and easily accessible source of pollen and nectar, for numerous species of insects, and are amongst the most visited plants both during the day and at night.
The team investigated a total of 100 cabbage thistles, which were growing on five meadows experimentally illuminated with LED street lamps, and five meadows without artificial light. The illuminated plants were visited much more rarely by pollinating insects at night, than the unlit plants.
The decline in pollinators had a significant influence on the reproduction of the cabbage thistles: at the end of the test phase, the average number of fruits per plants was around 13% lower. "The pollination during the day obviously cannot compensate for the losses in the night", says Knop.
Diurnal pollinators also affected
The study also shows, that the nocturnal pollinators indirectly promote the diurnal pollinators, by visiting the same plants. The underlying mechanisms are still unknown – a possible explanation could be that the plants have a fitness advantage thanks to the nocturnal pollinators, and therefore provide more nutrition for the diurnal pollinators.
A loss in nocturnal pollination due to increasing light pollution, could therefore also indirectly have a negative effect on the diurnal pollinator community. According to Knop, this still needs to be researched in detail, as well as the long-term consequences of the pollination losses for the biodiversity.
The findings have driven the researchers to demand action: "Urgent measures must be taken, to reduce the negative consequences of the annually increasing light emissions on the environment", says Knop. This will be big challenge, as residential areas are worldwide increasing.
Details of the publication:
Knop E., Zoller L., Ryser R., Gerpe Ch., Hörler M., Fontaine C. (2017) Artificial light at night as a new threat to pollination. Nature, 2 August 2017, doi:10.1038/nature23288
PD Dr. Eva Knop
Institute of Ecology and Evolution, University of Bern
Tel. +41 31 631 45 39
Mobile: +41 79 362 27 90
Nathalie Matter | Universität Bern
Researchers invent tiny, light-powered wires to modulate brain's electrical signals
21.02.2018 | University of Chicago
The “Holy Grail” of peptide chemistry: Making peptide active agents available orally
21.02.2018 | Technische Universität München
For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.
In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...
Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale
Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...
For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.
But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...
Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.
The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...
Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters
Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...
15.02.2018 | Event News
13.02.2018 | Event News
12.02.2018 | Event News
21.02.2018 | Life Sciences
21.02.2018 | Life Sciences
21.02.2018 | Materials Sciences