Why in the news?

  • Light pollution is reported to cause disruptions in the circadian rhythm of birds, keeping them awake during the night.

Light Pollution and Impact on Biodiversity

  • What is it?: Excessive, misdirected, or obtrusive artificial light introduced into the natural environment.
  • Major forms of Light Pollution:
    • Skyglow – brightening of night sky over populated areas.
    • Glare – excessive brightness causing visual discomfort.
    • Light trespass – unwanted spill of light into areas not intended.
    • Clutter – confusing grouping of lights.
  • Causes:
    • Urbanisation and 24×7 active cities.
    • Streetlights, billboards, vehicle headlights.
    • Industrial installations, ports, airports.
    • Over-illumination in tourist and commercial hubs.
  • Impact on Biodiversity:
    • On Plants:
      • Alters photoperiodism: flowering, leaf shedding, fruiting cycles disturbed.
      • Trees under streetlights retain leaves longer, affecting seasonal cycles.
    • On Animals:
      • Disturbs circadian rhythm and breeding behaviour.
      • Migratory birds misoriented by skyglow → collisions with buildings.
      • Insects get attracted to lights leading to their exhaustion, predation and population decline.
      • Disrupts pollination cycles of insects like Honey Bees and butterflies (especially moth-pollinated plants).
      • Frogs and toads’ nocturnal mating calls are suppressed by light and affect reproduction.
      • Artificial coastal lighting confuses sea turtle hatchlings and causes them to move inland instead of towards the sea.
      • Reduced hunting efficiency of nocturnal predators, affecting prey-predator balance.
    • On Ecosystem:
      • Disrupts food chains
      • Alters species competition and migration timing.
      • Causes ecological traps where organisms are attracted to harmful light sources.
  • Impacts on Humans:
    • Affects human health: Melatonin suppression, sleep disorders.
    • Cultural impacts: loss of stargazing, astronomy.
    • Energy wastage → contributes to climate change.
  • Mitigation Measures:
    • Use shielded lighting to direct light downward.
    • Adopt timers and sensors for lights.
    • Replace high-intensity white/blue LEDs with amber/yellow spectrum lights.
    • Declare dark-sky reserves near biodiversity-rich and astronomical zones.
    • Incorporate light pollution in EIA norms.
    • Awareness and community participation.
  • Global Best Practices:
    • International Dark-Sky Association (IDA): Creates awareness and takes mitigation efforts.
    • UNESCO recognizes dark-sky reserves:
      • India’s first: Hanle Dark Sky Reserve, Ladakh, 2022.
    • CPCB guidelines under Environment Protection Act, though light pollution is not explicitly regulated in India.
    • Smart Cities Mission promotes LED-based, shielded street lighting.