Light pollution


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  • Recently, the district administration of Ladakh designated six hamlets within the Changthang Wildlife Sanctuary a “dark sky reserve”, an area whose skies were free of light pollution.
  • As the reserve is designated as a "dark sky reserve," it has a responsibility to keep the skies dark, particularly for the astronomical observatories located in the area.
  • The idea of the sky as a natural resource capable of being polluted became popular when SpaceX’s Starlink constellation of small satellites began to obscure the view of ground-based telescopes around Earth.


  • A Dark Sky Reserve is public or private land with a distinguished nocturnal environment and starry nights that has been developed responsibly to prevent light pollution.
  • Reserves consist of a core area meeting minimum criteria for sky quality and natural darkness and a peripheral area that supports dark sky preservation in the core.


  • Individuals or groups can nominate a site for certification to the International Dark Sky Association (IDSA), a United States-based non-profit organization incorporated in 1988.
  • There are five designated categories:
    • International Dark Sky parks, communities, reserves, sanctuaries and Urban Night Sky Places.
  • The certification process is similar to that of a site being awarded the UNESCO World Heritage Site tag or getting recognised as a Biosphere Reserve.
  • Between 2001 and 2022, there have been 195 sites recognised as International Dark Sky Places globally.


  • The IDSA considers a piece of land suitable for dark sky place only if:
    • It is either publicly or privately owned
    • It is accessible to the public partially or entirely during the year
    • The land is legally protected for scientific, natural, educational, cultural, heritage and/or public enjoyment purposes
    • The core area of the land provides an exceptional dark sky resource relative to the communities
    • Cities that surround it and the land offers prescribed night sky brightness either for a reserve, park or sanctuary.
  • India is still in the process of filing its nomination to IDSA.


  • The inappropriate or excessive use of artificial light is known as "light pollution."
  • Components of light pollution include:
    • Glare-excessive brightness that causes visual discomfort
    • Skyglow- brightening of the night sky over inhabited areas
    • Light trespass-light falling where it is not intended or needed
    • Clutter-bright, confusing and excessive groupings of light sources



  • Much outdoor lighting used at night is inefficient, overly bright, poorly targeted, improperly shielded, and, in many cases, completely unnecessary.
  • This light and the electricity used to create it are being wasted by spilling them into the sky rather than focusing them on the actual objects and areas that people want illuminated.




  • Wastes energy and money:
    • Lighting that emits too much light or shines when and where it’s not needed is wasteful.
    • Wasting energy has huge economic and environmental consequences.
    • For example, estimates show that at least 30 percent of all outdoor lighting in the U.S. alone is wasted, mostly by lights that aren’t shielded. That adds up to 3.3 billion dollars and the release of 21 million tons of carbon dioxide per year.
  • Disrupts the ecosystem and wildlife:
    • Plants and animals depend on Earth’s daily cycle of light and dark rhythms to govern life-sustaining behaviours such as reproduction, nourishment, sleep, and protection from predators.
    • Scientific evidence suggests that artificial light at night has negative and deadly effects on many creatures, including amphibians, birds, mammals, insects, and plants.
    • For example, nocturnal animals sleep during the day and are active at night. Light pollution radically alters their night-time environment by turning night into day.
    • Also, glare from artificial lights can also impact wetland habitats that are home to amphibians such as frogs and toads, whose night-time croaking is part of the breeding ritual.
  • Harming human health:
    • Humans adapted to the natural light-dark cycle of day and night. The spread of excessive artificial lighting means most humans no longer experience truly dark nights.
    • Research suggests that artificial light at night can negatively affect human health, increasing the risks of obesity, depression, sleep disorders, diabetes, breast cancer and more.
    • Humans, like the majority of life on Earth, follow a circadian rhythm, our biological clock, a sleep-wake pattern governed by the day-night cycle. Artificial light at night can disrupt that cycle.
    • For example, by disrupting the circadian rhythm, artificial light at night can hamper the production of melatonin, an influential hormone in the human body with effects on sleep, moods, and cognition. A study shows that circadian disruption, which alters melatonin levels, can increase the risk of breast cancer among night-shift workers by 40%.
  • Effect on Astronomy
    • Light pollution reduces the contrast between stars and galaxies in the sky and the sky itself, making it more difficult to detect fainter objects. This is one factor that has caused newer telescopes to be built in increasingly remote areas.


  • Use light sources with the minimum intensity necessary to accomplish the light's purpose.
  • Turn lights off using a timer or occupancy sensor, or manually when not needed.
  • Improve lighting fixtures, so that they direct their light more accurately towards where it is needed and with fewer side effects.
  •  Adjust the type of lights used so that the light waves emitted are those that are less likely to cause severe light pollution problems.
  • Evaluate existing lighting plans and redesigning some or all of them based on whether existing light is actually required.
  • Light with energy efficient sources such as LED’s and compact fluorescents.
  • Create public awareness about the wastefulness of excessive night lighting and the importance of using the right lighting for the right situation.


  • Various natural processes can only happen during the night in darkness. Examples are resting, repairing, celestial navigation, predating or charging of systems. For this reason, darkness has the equal and amendatory functional importance as daylight. It is indispensable for the healthy functioning of organisms and whole ecosystems.
  • The good news is that light pollution, unlike many other forms of pollution, is reversible, and each one of us can make a difference. Just being aware that light pollution is a problem is not enough; the need is for action.


Q. Discuss the impacts of increased and widespread use of artificial light at night. Suggest practical solutions to combat light pollution.