By Helen Gloege ‘23
Staff Writer
The current decline of insect populations around the world could put ecosystems at risk of collapsing. Insects are responsible for the biological foundation of all terrestrial ecosystems, pollinating plants, dispersing seeds, maintaining soil structure and fertility, controlling the populations of other organisms and providing a food source for other animals. For example, fireflies are important to ecosystems, as their larvae feed on pests that can destroy the habitat of other organisms, while grasshoppers benefit ecosystems by facilitating cycles of decomposition and regrowth.
A recent study titled “Narrow-spectrum artificial light silences female fireflies” by Avalon Owens and Sara Lewis discusses how using artificial light at night creates problems for nocturnal biodiversity. Fireflies use their flashes to find mates, and when these flashes can’t be seen at night due to artificial light, it hinders their ability to mate and survive. The study tested different artificial light colors at different intensities and found that all artificial light treatments significantly suppress courtship activity.
The study recommended minimizing the duration and strength of lights or having outside lights fitted with motion sensors that can’t be triggered by bugs. It is possible that energy-efficient LED lights could be making things worse, as the short wavelengths of LED lights are more attractive to insects.
Levels of artificial light at night are rapidly increasing by 20 percent each year, causing disruptions in animal behavior. Another study, titled “Nocturnal city lighting elicits a macroscale response from an insect outbreak population,” describes the reasons behind an insect outbreak in Las Vegas, Nevada, in 2019, where over 45 million grasshoppers concentrated over high-intensity city lighting.
Las Vegas is the brightest city in the United States. The grasshoppers stayed in the outskirts of the Las Vegas Valley during the day near vegetated habitats and would descend on the city when the lights came on at dusk.
This phenomenon is not exclusive to grasshoppers and fireflies. Moths are known to move toward human-made light sources instead of orienting toward the moon. Baby sea turtles often head toward bright street or city lights away from the natural light of the ocean. They will turn inland and often never make it to the ocean. Bird and butterfly species depend on starlight-based navigation for seasonal migration. Artificial light can disrupt their migration, moving them off their normal routes and ending in fatalities.
Light pollution can interfere with bioluminescent creatures’ mating calls, subsequently decreasing the frequency of mating. European glowworms refrain from shining until it gets dark so they can be seen by males. With artificial light, females will delay their glowing or stop glowing entirely. It is suspected the West Nile virus may have been amplified partly due to artificial light. In this case, sparrows were exposed to light at night and their immune responses were disrupted, causing them to carry the virus for longer.
Despite little study on the impact of artificial lights on insects or other animals, it is important to further understand the trade-offs and effects of artificial light on the world around us. Various solutions exist to decrease light pollution and create darker skies at night.