Light pollution

Materials World magazine
1 Dec 2008

In the September column, I described my disappointment when I learned that my grandchildren and their contempories had never consciously viewed the Milky Way, and indeed had not fully appreciated the beauty, mystery and challenge of the rest of the firmament.

One reason for this is that their star-gazing has been impaired by the ubiquity of man-made terrestial lighting, known generally as ‘light pollution’. What I failed to realise was the extent to which light pollution has become a matter of international interest. One manifestation of this concern has been the decision by the editor of National Geographic Magazine to devote the cover of the November 2008 issue to a night-time aerial photograph of Chicago with its myriad lights, overprinted with the words ‘The End of Night: Why We Need Darkness’.

This vivid picture relates to an article in the magazine by Verlyn Klinkenborg. He included an image of an ‘electric blush’ above Salt Lake City, taken from a vantage point a hundred miles away from the township to show the range of the pollution. A world map is included to illustrate those areas most affected by light pollution. It has been calculated that two-thirds of humanity lives under skies polluted with light, and one-fifth can no longer see the Milky Way. Does our determination to turn night into day harm us? We are, after all, diurnal creatures with eyes adapted to sunlight, but we need darkness alternating with light for our natural circadian rhythm.


The negative impact of light pollution

Worryingly, recent evidence correlates higher rates of breast cancer with neighborhood night-time brightness. Light pollution also confuses wildlife. Frogs and toads living near brightly lit highways suffer light levels up to a million times brighter than normal and nesting sea turtles prefer dark beaches to lay eggs, becoming disorientated by artificial lights close to sea shores. Birds are the most affected – their migrations are influenced by changes in the daily ratio of light and dark. It has been estimated that in North America at least 100M die each year in collisions with man-made structures. Glass windows are the biggest killers – they baffle birds during the day and night.


Possible solutions to light pollution

As a partial remedy, Klinkenborg advocates adopting more efficient public lighting. He refers to a globe shaped streetlamp in Toronto which sends as much light wastefully towards the heavens as down to the street. He contrasts this with a lamp in Harmony, Florida, which has an opaque shade to prevent light emanating upwards. It focuses all the light where it is needed – along the town’s streets.

Klinkenborg’s paper is excellent in spelling out the formidable problems created by light pollution and no-one could argue with his central thesis that we must improve the efficiency of street lighting systems. What is disappointing is that nowhere does he attempt to address the problem of global warming and whether, in a general sense, we could not only improve the lighting of cities but also drastically reduce the level of lighting we use.

There are, of course, other ways of conserving electric lighting use. In a recent article in The Times, Sir Stuart Hampson points out that at this time of year, if the clocks went forward instead of back, we would reduce the need for domestic, office and street lighting and save over a million tonnes of carbon dioxide from being released into the atmosphere every year.


Further information

'Our Vanishing Night', by Verlyn Klinkenborg, National Geographic Magazine, November 2008.

'Daylight is precious. Let's stop wasting it', by Stuart Hampson, The Times online, 22 October 2008.