Animal-assisted pollination is a key factor to the growth of many crops. A new study, published in Nature, found artificially lit areas have reduce visits of nocturnal pollinators to flowers by 62%.
Pollination has already been on the decline due to a number of factors. The new study reports these factors include ” habitat changes, intensive agriculture, pesticides, invasive alien species, spread of pathogens and climate change.”
“Our study suggests that it is quite common for plants to have both night and day pollinators. During night it is often the scent that attracts the nocturnal pollinators but also other cues can be important, such as visual cues as the nocturnal pollinators have often very sensitive eyes,” said the lead researcher on the study, Dr. Eva Knop.
The study took place in 14 meadows in Switzerland. Scientists flooded 7 meadows with artificial lights, and 7 meadows were left to the natural levels of darkness. Researchers monitored the insect and plant interactions. They found the number of pollinators at night were much, much lower in the meadows with artificial light.
However, does the amount of night pollinator visitors actually effect the yield of crop growth? Yes, it does. To deduce this answer, scientists focused on the cabbage thistle (as it is one of the most frequently visited plant by night pollinators). When this plant is exposed to artificial light at night, there is a 13% reduction in number of fruits produced.
The study also reports that artificial light at night is rapidly spreading across the globe at a rate of 6% per year. If the problem is not addressed, the study says “these effects have the potential to cascade from the nocturnal to the diurnal pollinator community.”
Unfortunately, the scientists have yet to conclude an exact reason as to why the artificial light causes pollinators to stay away from crops at night. However, they have several theories. Dr. Knop says “It is known that many nocturnal insects are attracted by the light of lamps and thus distracted from visiting flowers. Thus, this is a likely mechanism but probably not the only one.”
Therefore, one can infer that this decrease in pollination is deeply concerning. It will affect the livelihoods of millions as well the overall economy. The study reports “Pollination by animals is also a crucial ecosystem service for global food supply, the estimated economic value of pollination was US$361 × 109 in 2009.”