New studies have shown that light pollution is impacting the way insects hunt, mate, and protect themselves. It has made them disoriented and vulnerable to predators and other external threats. It has adversely affected the population of insects and threatens to disrupt the ecological balance in many areas on the planet.
Along with the threat posed by pesticides, loss of habitat, industrial pollution is a host of factors, light pollution created by humans is posing a potent threat to the existence of many types of insects.
Over half a million species of insects on the planet are nocturnal and light pollution adversely impacts their life cycles. Artificial light cover is increasing across the planet and covers a quarter of the land surface of the planet.
Light Pollution Directs Affecting Insect Population
Several studies have indicated that light pollution is harming the insect, bird, and animal populations, especially the nocturnal species. It can affect birds, bats, animals, insects, and even plants.
Douglas Boyes from the Centre for Ecology and Hydrology, UK, focused on the moth caterpillar in southern England. They focused on the caterpillars as they remain confined to a limited area during their lifespan. So any changes in their behavior could be attributed to local conditions.
Moths are extremely diverse ecologically and evolutionarily. Studying them can give a good idea of other nocturnal insects as they are representative of other species of insects. Boyes and his team spent a total of 400 hours outdoors studying the caterpillars in various conditions.
Boyes visited about 27 sets of sample sites that were the home of a couple of diverse clusters of caterpillars that could be studied easily.
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The sites comprised either a grass-margin or a hedgerow along roadsides that were illuminated and a matching site that was unlit. Of the 27 illuminated sites chosen, 11 were lit with LED lamps (Light Emitting Diodes), 14 with high-pressure sodium lamps, and 2 with low-pressure sodium lamps.
To get an accurate count of the insects, Boyes and his team disturbed hedges in summer and spring and counted the flying insects. They also brushed the grass using netting to get the numbers of those that had emerged at night to feed.
Light Pollution Adversely Affects The Numbers, Growth, Feeding Habits, And Reproductive Capacity
The majority of the 2,478 caterpillars counted by Boyes, most were from unlit areas. He discovered that the population of the caterpillars declined in illuminated areas by anywhere between a third and a half. Almost all the areas that were lit for 5 years or more were found to contain fewer caterpillars.
Other than the numbers, Boyes detected other changes in caterpillars in lit and unlit areas. The caterpillars in illuminated areas were found to be heavier, which could be attributed to stress brought about by rushed development. This will cause adults to be smaller and less fit evolutionary. The reproductive capabilities of caterpillars growing in lit areas are also affected, and they produce far fewer eggs.
The situation was the worst under LED lighting when compared to the traditional yellow light of sodium vapor. This was a matter of further concern as most streetlights are being changed to LED due to their brighter light and low electricity consumption.
Boyes also experimented by placing LED lights in previously unlit areas. He found that the nocturnal behavior of caterpillars was upset by this intrusion of light pollution.
White light emitted by LED was found to cause more disturbance possibly due to its similarity with daytime light. Insects are tricked into believing that it is daytime.
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Researchers are trying to translate these studies to fit the larger picture. With 1.1% of illumination present at the studied sites, Boyes says it is clear that while light pollution is a cause of this decline, it could not be solely attributed to light.
It is due to a host of factors, including climate change, loss of habitat, increase in agricultural land, use of pesticides, and light pollution is another addition to this list. But areas that have been impacted by light keep increasing rapidly, even outside urban areas.
Boyes says that immediate changes are possible to counter the harm caused by light pollution, including dimming the LED to make it more insect-friendly by reducing the use of blue wavelengths. This can minimize the harm caused to insects.