What is light pollution?


Our view of the cosmos is a source of infinite amazement for humanity, but in London, the stars are blocked out by light pollution. Is your neighbourhood filled with bright lights that stay lit all night? How far do you have to go to experience a truly starry sky or marvel at the Milky Way?

What is light pollution?

Light pollution is artificial light that shines where it is not wanted or needed. In broad terms, there are three types of light pollution:

  • skyglow – the pink or orange glow that spreads above towns and cities, caused by a scattering of artificial light by airborne dust and water droplets
  • glare – the uncomfortable brightness of a specific light source
  • light intrusion (light trespass) – light that spills beyond the boundary of the property on which it is located, sometimes shining through nearby windows and curtains

Why is light pollution important?

Light pollution is important for the climate crisis, biodiversity loss and human health. Wasted light is an expensive waste of energy – just imagine leaving a garden hose or faucet running all night. Light pollution also negatively impacts humans and wildlife, and it contributes significantly to our carbon footprint.

Climate emergency

The climate crisis is the biggest threat facing life on this planet. We must drastically reduce our greenhouse gas emissions, a significant percentage of which come from lighting. London and cities like it have a leading role to play, and reducing our light waste is a critical part of the solution.


Light pollution has a significant negative impact on biodiversity. According to Cofnod, 60% of wildlife in the UK depends on natural darkness to survive. Light waste interrupts natural wildlife rhythms both on land and in the sea, including migration, reproduction, pollination and feeding patterns, which in turn disrupt the entire food chain.

Human health

Artificial light at night is linked with problems for human health, such as sleep disorders, depression, insomnia, heart disease, breast cancer and risk of autism spectrum disorder in children. Recent studies have found that exposure to light at night disrupts the body’s production of melatonin, a brain hormone responsible for regulating the human biological clock.

Get involved – a dark skies bucket list

London may be one of the most light-polluted cities on Earth, but there are lots of ways to restore and protect our nocturnal ecosystem, from checking your home lighting to going outside to count the stars in the night sky.

  • Support CPRE London’s campaign as part of the More Natural Capital coalition to persuade the next Mayor of London to develop best practice guidance for lighting design to reduce light pollution and to safeguard and extend dark sky areas.
  • Participate in the annual Star Count, Globe at Night and other citizen science campaigns
  • Escape light pollution at your nearest dark-sky site to experience a truly dark, starry night sky
  • Learn about London’s nocturnal wildlife, such as bats, foxes, owls, hedgehogs and moths
  • Adjust the outdoor lighting at your home and use warm colour-temperature bulbs and timers
  • Ensure windows, including sky/rooflights, have curtains or blinds and keep them closed at night
  • Ask local councils and highway authorities to adopt lighting policies that protect our natural night
  • Write to your MP and ask them to join the All-Party Parliamentary Group for Dark Skies
  • Go for a nighttime walk in your local park to spot planets and stars
  • Attend a lecture or online event about astronomy or light pollution
  • Become a member of Dark Sky London and CPRE
  • Join or donate to the International Dark Sky Association

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