Switch it off!: How light pollution disorients ecosystems

Source: Down to Earth

Relevance: Impact of light pollution

Synopsis: Excessive use of light in urban areas has negative impact on human and animal life. Analysis of the impact and mitigation measures that can be taken.


Watching the night sky, the stars and other astronomical objects is an absolute delight. While one may still observe these phenomena in rural areas, they are becoming increasingly rare in densely populated urban areas. The presence of artificial light in the environment is a major reason behind this.

About Light pollution

“It is an unwanted consequence of outdoor lighting and usually occurs due to excessive and inappropriate artificial light”. There are five components of light pollution:

  1. Urban sky glow– Urban sky glow refers to the brightening of the night sky over urban inhabited areas
  2. Light trespass– The falling of light in an area where it is not intended or needed is called light trespass
  3. Glare– It is the excessive brightness of light, causing visual discomfort and disability.
  4. Uplight– An uplight is directed toward the open sky, causing a very strong, localized form of light pollution.
  5. Clutter– It refers to an excessive grouping of lights, commonly found in over-lit areas.
  • Poor placement of signage and streetlights
  • Excessive and inappropriate use of light
  • High population density
  • Higher road density and traffic density
  • Environmental conditions such as smog, fog and high levels of suspended particles also increase the intensity of light pollution.
Must Read: Skyglow forces dung beetles to abandon milky way as their compass
  • On plants– light pollution affects plants by interfering with photoperiodism. Several biological activities in plants, such as pigment formation, leave shedding and the onset and breaking of bud dormancy are determined by the photoperiod. Increasing lighting can prevent flowering and pollination in plants and hamper reproduction.
    • Photoperiodism: It is the functional or behavioral response of an organism to changes of duration in daily, seasonal, or yearly cycles of light and darkness.
  • On animals– Crepuscular (active only at dusk and dawn) and nocturnal (active only during the night) animals depend on the duration of day (light) length to start / stop their daily activities. Exposure to artificial light interferes with these activities, decreases their chances of finding food and mates and exposes them to predators.
  • On insects– Artificial light at night is one of the important causes of global decline of insects. Amphibians are sensitive to ambient light, long exposure to artificial light can interfere with their reproduction
  • On turtles– Sea turtles lay their eggs on beaches. However, artificial lights on the coasts draw them away from the ocean and in the wrong direction.
  • On nocturnal birds– Nocturnal birds use moonlight and starlight for navigation and hunting and, thus, become disoriented by a large amount of artificial light.
  • On humans– Artificial light causes major sleep disturbances in humans. Brain wave patterns, hormone generation, cell regulation and other biologic functions are affected by light pollution. Light pollution hampers disruption of circadian clock which has been associated with a variety of medical issues, including depression, sleeplessness, cardiovascular disease and cancer
  • We should use light only in places and at times it is needed. Installation of time and motion sensor-based lighting can help achieve this.
  • Efficient lighting should be used and should be directed at the ground, not the sky.
  • A good lighting design should optimize the visibility of the intended object and minimize glare and light trespass.
  • Artificial light should be minimized in ecologically sensitive areas, such as routes for migratory birds and beaches with active hatching of turtle eggs.
  • Proper guidelines should be introduced regarding lighting on the highways and roads in or near forest regions.


Awareness about this lesser-known form of pollution needs to be augmented so that we can fine-tune our activities to reduce the negative impacts and make the world a better place for all beings


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