Along with the rapid growth of the human population, environmental pollution has increased due to the world’s urbanisation. Due to globalisation, more people are becoming aware of environmental pollution worldwide, and actions have been taken to mitigate the issue. However, light pollution remains underrated – a worldwide issue that could significantly impact the environment and is often overlooked.

Light pollution is excessive artificial light, also a form of energy waste. To facilitate nighttime activities and enhance quality of life, people have been using lights in various areas to illuminate every corner of their activity range.

Consequently, artificial light has become so widespread that it has formed a sky glow in urban areas, causing light pollution and threatening many animals in various ways.

First, it causes disorientation in wildlife. Insects such as moths and beetles have evolved unique photoreceptor adaptations that make them sensitive to light and, therefore, attracted to artificial light at night.

This disrupts their navigation, inhibiting their foraging and reproduction. Similarly, artificial light could disorient newly hatched turtles, leading them to move inland rather than into the ocean, potentially threatening populations of these marine reptiles.

According to the book Ecological Consequences of Artificial Night Lighting, published by Island Press in 2006, both sky glow and lighting interfere with migratory birds’ use of the horizon as a point of reference for direction when navigating at night.

In many cases, birds also crash into buildings with bright lights. Due to this phenomenon, which is especially prevalent in rainy and foggy weather, hundreds or even thousands of birds may be hurt or killed in a single night, reducing their ability to survive the winter.

In addition, light pollution disrupts animals’ vision. Nocturnal animals have developed better night vision because they have more rod cells (photoreceptors) in their eyes.

However, a sudden increase in illumination could temporarily blind some nocturnal animals, such as frogs. This reduction in visual capability may require recovery time ranging from minutes to hours.

During this period, they cannot get visual information on prey, predators, or conspecifics, which may affect their ability to reproduce, avoid predators, and engage in foraging and social activities.

Moreover, light pollution could disrupt the circadian rhythm of animals and plants. Under artificial illumination, diurnal animals, such as birds, lizards, and spiders, may extend their active period.

Some animals even develop crepuscular behaviours, shifting their foraging activity into the night, increasing predation pressure on nocturnal animals, such as moths, frogs, birds, turtles, and fish.

Besides animals, artificial light at night also disrupts plant flowering and growth patterns by affecting their metabolism, causing earlier leaf-out, later leaf-loss, and extended growing periods. This may reduce food availability for primary consumers, leading to cascading consequences for the food web and ecosystem.

Besides that, light pollution changes the prey-predator relationship. In some diurnal animals, artificial illumination at night increases the intervals between their predatory activities.

In response to a perceived increase in predation risk, prey species may reduce their activity in brighter surroundings.

In other words, artificial light at night may temporarily benefit predators. However, due to the potential changes in prey behaviour, it may be harmful to predators in the long run.

Lastly, communication between animals could be obscured by artificial light, as some nocturnal animals rely on visual signals, such as bioluminescent flashes, to find potential mates.

For example, the courtship display of fireflies involves exchanging bioluminescent messages often obscured by streetlights. Even though some insects can still see their surroundings, they are unable to recognise members of their own species, as in the case of teneral beetles.

In summary, the impacts of light pollution could be catastrophic for biotic communities and should not be underestimated.

Besides harming animals, light pollution also negatively impacts human health, such as insomnia, anxiety, and obesity.

More research is needed to shed light on light pollution, and urgent action is needed to promote the sustainable use of such energy while reducing its environmental impact.

Liew Kah Ying is an undergraduate in the Ecology Biodiversity Program at the Institute of Biological Sciences, Universiti Malaya. Associate Professor Dr Hasmahzaiti Omar is a Lecturer of the Ecology Biodiversity Program at the Institute of Biological Sciences, Universiti Malaya.