On a Saturday night in March 2009 a remarkable thing happened. Ordinary people around the world simply switched off their lights for 60 minutes. Iconic international landmarks like the Sydney Opera House, Empire State Building and Big Ben also went dark during the so-called Earth Hour, which was organised by the World Wildlife Fund to highlight how our wasteful attitude towards energy is contributing to climate change.

We’ve all grown accustomed to the sight of empty office blocks, public buildings and even car parks lit up at night, but the effects of so-called light pollution are now being felt far outside urban areas. Artificial outdoor lighting has increased dramatically over the last 30 years and Britain is now the second most illuminated country in Europe after the Netherlands.

Vast swathes of South East England, the Midlands and the Northern England conurbations are now marked out by ‘sky glow’, that artificial orange-yellow glare in the night sky that reduces natural visibility and makes the sight of a dark starry sky virtually impossible. Lighting from buildings, road lamps, freight depots, sports pitches and even the growing number of home security lights have all contributed to this effect, thanks in part to poorly shielded lamps or ill-directed fixtures.

According to the Campaign for the Protection of Rural England (CPRE), the insidious effect of light pollution and sky glow has crept deep into rural areas, with many locations well away from towns and cities now affected. Between 1993 and 2000 they claim that light pollution increased by 24 per cent across the UK and that the amount of truly dark night sky fell from 15 per cent to 11 per cent.

Using data from US Air Force weather satellites, CPRE has produced detailed light pollution maps for the UK that show how few areas of the country are now immune from the effects of badly designed street lighting, floodlights and security lighting – most notably Highland Scotland and Mid Wales.

Blinded by the light

Once upon a time, when it got dark we all went indoors, went to bed and that was that for the day. As one commentator has suggested, the ‘natural environment’ after sunset is of course darkness, so maybe we should call it what it really is – night pollution. Today we have a 24-hour culture where artificial light allows us to work, play and shop every hour of the day, including night-time. But could this actually be doing us long-term harm?

Distinct periods of light and dark form part of the 24-hour cycle, sometimes referred to as circadian rhythms, that are essential for the good health of all living things, including humans. There is clear evidence to suggest that exposure to artificial light at night reduces the human body’s production of melatonin, the hormone that tells us that it is dark.

Studies of people exposed to prolonged artificial light, such as night-shift workers, have shown that reduced levels of melatonin in the human body may be harmful in the long-run, increasing the risk of developing breast cancer, in particular.

For others, the effects of light pollution are detrimental in more fundamental ways. As veteran broadcaster Joan Bakewell puts it: “A bright starlit sky creates in us a sense of awe and wonder at the scale of the universe. Any further encroachment of this precious environment diminishes the nature of what it is to be human.”

If the effects of prolonged and widespread artificial light on humans is damaging, what is it doing to wildlife? Since all living things exist with regular patterns of light and dark, it is inevitable that ecosystems are being affected, whether through changes to mating, predation or eating habits.

Research has shown that migratory birds are disorientated by well-lit buildings and towers, and in the US there’s even a nationwide initiative called the Fatal Light Awareness Program that aims to reduce the huge numbers of migratory birds who die after flying into illuminated skyscrapers and other tall structures.

Nocturnal species such as bats and owls are inevitably affected by a loss of darkness, especially in terms of hunting and feeding. It also appears that artificial lighting is causing some songbirds to begin the dawn chorus much earlier than normal, especially the robin, which is often active in low light and whose song can be triggered by bright night-time lamps and floodlighting.

Insects are also influenced by bright unnatural light – and not just obvious ones like moths. Scientists say that ambient light and glare are harming fireflies and glow-worms in their search for mates, as their own self-produced light or bioluminescence is much dimmer.

Make sure your lights are right

• Fit the right wattage lamp: domestic security lights need no more than 150W, while 9W is usually adequate for an all-night porch lamp.
• Adjust lights so that they only illuminate the intended surface, and with security lights make sure they only pick up movement in the target area.
• Main beam angles of all lights should be below 70° to reduce the effects of glare.
• Direct light downwards if at all possible, but if using uplighting install shields to minimise wasted upward light.
• Don’t install equipment that spreads light above the horizontal. 

Star-filled heavens

The Campaign for Dark Skies (CfDS), run by the British Astronomical Association, is one initiative attempting to curb excessive and irresponsible lighting so that everyone can enjoy the sky at night. “Light from galaxies has taken tens, hundreds and thousands of millions of years to reach us on Earth,” says Bob Mizon, the campaign’s UK coordinator, “only for the signals to be lost in the last fraction of a second of its journey due to being swamped by light pollution.”

Four hundred years after Galileo first gazed at the night sky through a telescope, the aweinducing sight of 1,000 and more stars across an exceptionally clear night sky is becoming rarer than ever. In 2007, CfDS and CPRE asked people in Britain to count the number of stars they could see within the constellation of Orion, one of the most easily identified in the night sky (in a truly dark sky up to 50 stars should be visible to the naked eye). Of the 2,000 or so who took part, only 2 per cent said they could see more than 30 stars, compared to 54 per cent who saw fewer than 10 stars in Orion, with light pollution proving a major problem for many people.

Scientists estimate more than half the UK population cannot even see our own galaxy, the Milky Way, that band of cloudy light across the entire night sky, because sky glow is simply blotting it out.

Inevitably, new telescopes are having to be built in ever more remote locations to minimise the effects of unnatural light. In France, authorities have announced the creation of Europe’s first ‘anti-light-pollution reserve’ to help safeguard a clear view of the night sky. The idea is to establish a protective 10–15km buffer zone around the historic Pic du Midi mountain observatory so views of the solar system are not ruined by artificial light from the ground. The first steps involve local villages that are being asked to sign up to a charter to modify their street lighting.

The need to use lighting more efficiently and only where necessary is a factor that all of us need to consider. For instance, do some street lights need to be kept on all through the night, and why are advertising hoardings or empty car parks floodlit? Domestic lights outside private properties should be angled properly so that they don’t become a nuisance, a factor that local authorities are now obliged to consider after the Environmental Protection Act 1990 (and subsequently the Clean Neighbourhoods and Environment Act 2005) made light pollution a Statutory Nuisance for the first time.

And there are some signs of change for the better. South Tyneside Council’s ‘Light it’ is a £63 million scheme that uses brighter, clearer white light to replace traditional street lighting. Since fewer lights are needed, they are spaced further apart, which reduces upward light pollution, as well as light intrusion into nearby properties.

Ultimately, though, perhaps the most persuasive reason to counter growing light pollution is the sheer waste of energy and its obvious contribution to global warming. Lighting is responsible for around a quarter of energy consumption worldwide, and by cutting back on unnecessary and wasteful lighting, we could be saving more than just a view of the stars.