Light Pollution

Light Pollution

Subject: Environment

Section: Pollution

Context: Ladakh to have India’s first ‘Dark Sky Reserve’ to promote astronomy tourism

Concept:

What is a Dark Sky Reserve?

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.

According to the International Dark Sky Association (IDSA) website, these 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.”

How does a site become a ‘Dark Sky Reserve’?

Individuals or groups can nominate a site for certification to the International Dark Sky Association (IDSA). There are five designated categories, namely 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 January 2022, there have been 195 sites recognised as International Dark Sky Places globally.

Why was Ladakh chosen for the project?

• Ladakh is a unique cold desert located about 3,000 metres above sea level with high mountainous terrains. Long and harsh winters with minimum temperatures dropping to minus 40 degrees Celcius make large parts of the UT highly inhabitable.
• This aridity, limited vegetation, high elevation and large areas with sparse populations – all make it the perfect setting for long-term astronomical observatories and dark sky places.
• But the primary objective of the proposed Dark Sky Reserve is to promote astronomy tourism in a sustainable and environment-friendly manner. Scientific methods will be used here to preserve the night sky from ever-increasing light pollution.
• With metros, cities and peripheral areas experiencing light pollution and remaining constantly lit up, there are diminishing areas that offer a view of clear skies on cloudless nights, experts have noted.

Light pollution

• Light pollution is an unwanted consequence of outdoor lighting and usually occurs due to excessive and inappropriate artificial light.
• There are five overlapping components of light pollution: Urban sky glow, light trespass, glare, uplight and clutter.
  • Urban sky glow refers to the brightening of the night sky over urban inhabited areas.
  • The falling of light in an area where it is not intended or needed is called light trespass.
  • Glare is the excessive brightness of light, causing visual discomfort and disability.
  • An uplight is directed toward the open sky, causing a very strong, localised form of light pollution.
  • Clutter 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 and a higher road density and traffic density contribute significantly to light pollution.
• At times, certain environmental conditions such as smog, fog and high levels of suspended particles also increase the intensity of light pollution.

Impact of light pollution on plants, animals and human beings

• Plants are affected by three characteristics of light: Quantity, quality and duration.
  • Quantity of light refers to the total concentration or intensity of the light.
  • Light quality indicates the wavelength of the light and duration refers to the total period for which light is present.
• Light pollution affects plants by interfering with photoperiodism.
• Many plant species (such as night-blooming cacti, for example, Queen of the Night Epiphyllum Oxypetalum) bloom only at night and depend on nocturnal pollinators for pollination. Increasing lighting can prevent flowering and pollination in such plants and hamper reproduction.
• Similarly, animals are also affected by light pollution. 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.
• Light pollution, through the superchiasmatic nucleus, disrupts circadian rhythm by reducing the secretion of melatonin, a sleep-inducing hormone.
• Artificial light at night is one of the prominent causes of global decline of insects.