Light Pollution

Reference

According to researchers from the Chinese Academy of Sciences, high levels of Artificial light at night (ALAN) are making it difficult for insects to eat tree leaves. This is posing a threat to urban food chains.

Light Pollution due to Artificial Light

• Light pollution is defined as the presence of unwanted, inappropriate or excessive artificial light. Unnecessary and artificial lighting causes glare in the sky during night time.
• Thus, light pollution is a man-made change in the naturally occurring light levels.

Components of light pollution

• Glare: Excessive brightness causing visual discomfort
• Sky Glow: The glow of the sky at night in residential areas
• Light Trespass: Light falling at a place where it is not needed.
• Clutter: Glare, confusing and excessive scattering of light sources

Sources of light pollution

• Outdoor lights and streetlights
• Landscaping and mood lighting
• Sports lighting
• City lighting
• Oil and gas production
• Illuminated greenhouses
• Electronic advertising
• Industries and factories
• Homes and apartments
• Parking lots
• Satellites

Effects of light pollution

On wildlife and ecosystem

• Plants and animals depend on the daily cycle of light and darkness for life-sustaining behaviours such as reproduction, nutrition, sleep and protection from predators.
• According to scientific evidence, artificial light at night has a negative impact on many organisms including amphibians, birds, mammals, insects and plants.
• Nocturnal animals rest during the day and are active at night. Light pollution fundamentally alters their nighttime environment.
• Predators use light to hunt while prey species use darkness as a means of concealment.
• Glare also affects wetlands that are home to amphibians such as frogs and toads.
• Artificial light reduces the number of nocturnal animals by disturbing their reproduction.
• Sea turtles lay eggs on the beach at night. The hatched babies reach the sea by seeing the shining horizon above the sea. Artificial light drives them away from the sea.
• Birds that migrate or hunt at night make their way in the light of the moon and stars. They may be distracted by artificial light.
• Many insects are attracted to light but artificial light can create a fatal attraction.

On energy and climate

• Excessive lighting levels cause huge economic and environmental losses due to wastage of energy.
• Dark Sky estimates that at least 30% of all outdoor lighting in the US alone is wasted. This results in the emission of 21 million tons of carbon dioxide each year.

On human health

It increases the risk of sleep disorders, depression, obesity and heart disease, diabetes and cancer.

On research

Excessive artificial light and glare in the sky cause problems in astronomy research. Also, it affects the light coming from the stars.

Conclusion of Chinese researchers' study related to artificial light

• Artificial light hardens tree leaves, which may be unsuitable for herbivorous animals to consume.
  • This is likely to alter the dietary preferences of herbivorous insects.
• It also negatively affects birds and hatchling sea turtles.
• High levels of artificial light cause plants to focus on protection rather than growth, causing leaves to harden with more chemical defense compounds.
  • According to the researchers, areas with the most light at night had leaves that were extremely hard, showing no signs of insect activity.

Other major studies on light pollution

• According to the study published in the journal Frontiers in Plant Science, artificial light has species-specific effects on leaf nutrients, size and defence substances.
  • These changes can significantly alter key functional traits and ecological processes such as nutrient cycling and energy flow.
• According to a 2016 report published in Science Advances, more than 80% of the world's population lives in a light-polluted environment.
• According to a study published in the Science Journal in 2023, the intensity of light in the night sky is constantly increasing. On the other hand, scientists have recorded a decrease in the visibility of stars.

The effect of hardening the leaves

• Herbivory decreases with increasing leaf carbon content as well as leaf toughness.
  • Leaf toughness contributes to the most important leaf traits such as structural strength and mechanical protection.
• Leaves with higher toughness decompose at a slower rate, potentially negatively affecting nutrient cycling.
• Specific Leaf Area (SLA) can indirectly reflect the adaptive capacity of plants under different light intensities.
  • High light conditions may limit the increase in SLA, leading to the formation of thicker leaves with lower light capture efficiency and nutrition. This is less favorable for herbivorous feeding.
• High artificial light intensity is detrimental to the energy flow from plants to higher consumer levels.
  • This poses a potential threat to the maintenance of biodiversity, including arthropod and bird diversity, in urban ecosystems.