For almost the whole of human history, people have loved light and feared the dark. But growing light pollution worldwide is bringing about a welcome change in attitude. We would like stars to sparkle again in the night sky — if the Star of Bethlehem reappeared this year it would be lost in the artificial urban glow of a modern city — and we want to stop excessive illumination putting wildlife and human health at risk.

Places around the world are competing to attract visitors by proving their darkness. This month, for example, the International Dark-Sky Association (IDA) recognised two more Dark Sky Places in the UK: Isle of Coll off the west coast of Scotland and a 1,500 sq km reserve in the far north of England, encompassing Kielder Forest and Northumberland National Park. “Dark skies and astronomy have become a passion in the area,” says Heidi Mottram, chief executive of Northumbrian Water. All together, the US-based IDA has designated 24 Dark Sky places worldwide, including six in the United Kingdom, and it is evaluating many other candidates on the basis of the darkness of their sky and their commitment to fight bright light at night. Scott Kardel, IDA managing director, believes that the world, which has become ever brighter since the invention of artificial lighting, is approaching a historic turn back towards darkness.

“More people are realising the value of restoring the night sky to the glory it had before civilisation,” he says, “and appreciating the harm that light pollution can do to human health, plant and animal life, as well as the money and energy wasted on excessive lighting.”

The campaign has two interwoven strands.

One is to preserve — and celebrate — the special night-time darkness of remote places such as Kielder, where visitors can admire celestial sights such as the Milky Way that are invisible in most towns and cities. The other is to press governments at local and national level to clamp down on excessive lighting everywhere else, through legislation and planning controls, while encouraging highway authorities, businesses and householders to install less obtrusive outdoor lights along roads and on buildings. “When people have been to somewhere truly dark, they want to see less unnecessary light in their own community,” says Kardel. In France, a law went into effect in July, requiring businesses to turn off exterior lighting between 1am and 7am. In the UK, the results of the annual nationwide Star Count, run jointly by the Campaign to Protect Rural England and the British Astronomical Association, suggest that the tide may just have turned. The proportion of observers who could see more than 30 stars within the constellation of Orion with the naked eye — a measure of a truly dark sky — rose from 1 per cent in 2011 to 2 per cent in 2012 and 5 per cent this year.

Even so, Emma Marrington, Campaign to Protect Rural England (CPRE) dark-sky campaigner, says the figures show that a large majority of people in Britain still suffer severe light pollution, with more than half the Star Count observers unable to see more than 10 stars within Orion. “It is depressing how disconnected most of us are from the majesty of a starry sky,” she adds.

Improved technology, including street and building lamps that send all their illumination downward rather than up into the sky, is helping the fight against light pollution. “Far more well-directed lighting is being installed along British roads,” said Bob Mizon, co-ordinator of the UK Campaign for dark skies.

Such downward-pointing lights help to darken the sky, but Matt Shardlow, chief executive of the invertebrate charity Buglife, points out that they seriously disturb ground-dwelling nocturnal creatures, particularly if they use light-emitting diodes that have a spectrum closer to daylight than conventional incandescent bulbs or yellow sodium lights.

“Some of the biggest impacts come when artificial light shines on water — ponds, lakes, rivers and the coastline — where nocturnal creatures are very sensitive to surface illumination,” said Shardlow. On land, biologists discovered an African dung beetle this year that uses the Milky Way to navigate; it would get lost anywhere near a modern town.

Although people are not as sensitive as nocturnal wildlife to light, medical researchers say urban illumination is bright enough to damage human health. The glare from a street or building light, shining on to a bedroom window, even with curtains drawn, may disrupt the circadian rhythm of sensitive people and diminish the quality and quantity of their sleep.

Many city dwellers regard outdoor lighting as a security blanket — and some illumination does help older people, in particular, to avoid tripping on uneven pavements and other obstacles — but the widespread belief that bright light reduces crime is unfounded, according to dark-skies campaigners. On the contrary, it helps criminals to identify targets, security failings and escape routes.

No one is suggesting a total blackout. Well-directed external lighting enhances night-time safety. And some urban buildings, bridges and other monuments deserve illumination during evening on aesthetic grounds. But we also need more opportunities to admire the beautiful celestial lighting of stars and planets, moon and Milky Way.

— Financial Times