28 March 2009

Light kills

Our blazing night time lights impact wildlife on land and sea. Earth Hour is a moment of contemplation, hopefully not just of carbon pollution but also of direct light pollution.
Image by Calvin Teo, on wikimedia

It is well documented that baby sea turtles rely on the direction of starlight and moonlight reflected off the water's surface to help them find the ocean when they emerged from their nests. Turtles in urbanised areas go in the wrong direction, heading towards the brighter buildings and street lamps.

Artificial light can mess up coral sex and disrupt other reef activities (from Light Pollution Offers New Global Measure Of Coral Reef Health ScienceDaily 24 Nov 08). Lab studies show that light can disrupt coral reproduction, which is timed to moonlight. Light at levels that would seem insignificant to humans can be incredibly significant to marine organisms and even terrestrial organisms.

Artificial light tends to benefit predators, which is why many organisms rely on darkness to maximize their odds of survival. In Florida, lighting was seen to disrupt foraging behaviour of dune mice which naturally avoided foraging during the full moon. One beach mouse subspecies, the Pallid beach mouse, has already become extinct. (Lights From Beachfront Development Harm Endangered Beach Mice ScienceDaily 30 Nov 04)

Light can also disrupt migration patterns of birds, possibly leading them astray from food and safe passage. Most bird migration takes place at night. (Birds Migrate Together At Night In Dispersed Flocks, New Study Indicates ScienceDaily 7 Jul 08)

Light also causes bird death directly. Each year, it is estimated that millions of birds collide with communication towers. A study found that a simple alteration of the lighting scheme on these towers may reduce bird mortality by as much as 71%. (Change Of Lighting Could Drastically Reduce Bird Death By Collision With Communication Towers ScienceDaily 20 Mar 09)

Even in daylight, our urban structures create artificial polarised light that confuse wildlife (Light pollution forms 'eco-traps' Mark Kinver, BBC News 16 Jan 09)

Water is the primary source of horizontal polarised light in the natural world, and many animals - including birds, insects and reptiles - had highly developed polarisation vision. This particular form of light played a key role in the animals' lifecycle, such as finding breeding and feeding sites.

Artificial sources of polarised light: any kind of shiny, black object - oil, solar cells, asphalt - causes problems. The closer they are to wetlands, the bigger the problem.


  1. This is excellent point, thanks for letting us know. Nice blog here. Anna :)

  2. Thanks Anna, for the encouragement!

    I was also surprised to learn about the impact of our use of lights and thought it useful to share this during the time that we celebrate Earth Hour.

  3. do we have to turn off our lights tonight?

  4. Thanks for the excellent info on light pollution. I knew it is harmful but didn't know its impact. Now I know better.

  5. What an apt description for S'pore -- "blazing night time" ... At the beginning of this year, I tried explaining to someone about the perils of light pollution to nocturnal & migrating wildlife, esp. near (real) wetlands & waterbodies (with particular reference to the blindingly lit-up "white orb/mangosteen" at Sengkang Floating Wetland) -- but to no avail. Awareness about light pollution is not just lacking, but also not taken seriously in S'pore.

    You might be interested to read 'City lighting boosts pollution' (BBC News, 14 Dec 10). Researchers discovered that artificial light destroys light-sensitive nitrate radicals that aid in the breaking down of air pollutants during night time. The loss of these nitrate-cleansers thus increases the incidence of smog & ozone formation the next day.

    Quick reference brochures on the negative impacts of light pollution & ways to minimize this are available from the International Dark-Sky Association (IDA). For those who believe the more & brighter the lights are, the better the human safety at night -- this is not absolutely true -- eg. see IDA's 'Light Pollution and Safety' brochure on how night glare actually makes us UNABLE to see who/what is lurking right under an overly-bright (& energy-wasting) light.



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