More and more evidences show that the insect population is shrinking due to climate change, habitat loss and pesticides. The factors are complex and diverse, including the continuous loss of forests, wasteland, grasslands and marshes, excessive use of pesticides, climate change and pollution of rivers and lakes. The use of artificial lighting at night is considered to be another driving factor of insect reduction, but its influence degree is still unclear.
In a British study, it was found that artificial street lamps disturbed the behavior of moths at night and reduced the number of caterpillars by half, among which modern LED street lamps seemed to have the greatest influence. This study, published in Science Progress, is by far the strongest evidence that light pollution will adversely affect the local insect population and affect birds and other wild animals that depend on caterpillars for food.
researchers believe that street lamps may prevent moths from laying eggs at night, or put insects at risk of being found and eaten by predators such as bats. Conversely, caterpillars born under street lamps, especially those born under LED street lamps, will change their eating habits. Researchers say that there are some practical solutions that will not harm public safety, including dimming street lamps in the early hours of the morning, installing motion sensors or using color filters to cut off the most harmful light bands and so on.
In this study, experts from charities, butterfly conservation organizations, Newcastle University and the British Center for Ecology and Hydrology investigated caterpillars in grasslands and bushes on both sides of roads in southern England. The researchers investigated 26 locations with street lights in Oxfordshire, Berkshire and Buckinghamshire, and each location was compared with similar unlit road sections nearby. According to the survey, in areas with lighting, caterpillars are reduced by about half (47% in hedges; 33% in the grass). In the second experiment, a lighting device was set up in the field. They found that the number of caterpillars under LED lights decreased, which indicated that it had an impact on the feeding behavior of caterpillars.
A scientific review of insect population in 219 pointed out that 4% of the world's species are experiencing a sharp decline. According to the study, bees, ants and beetles disappear eight times faster than mammals, birds or reptiles, while other species, such as houseflies and cockroaches, may flourish. The disappearance of insects has had a profound impact on the whole ecosystem. Insects provide food sources for many birds, amphibians, bats and reptiles, while plants rely on insects for pollination.