The dark side of light

2009-10-19 00:00

WHEN an earthquake knocked out the power in Los Angeles in 1994, anxious residents reportedly called local emergency centres to report a strange “giant, silvery cloud” in the sky. In the natural darkness left by the outage, what they were seeing — for the first time — was the Milky Way.

Unbelievable? Unfortunately not.

Even in the comparatively small African city of Pietermaritzburg, the effects of light pollution (see box) are making it difficult — even for those who know it’s out there — to see the night sky.

Local stargazers say light pollution is a “huge factor” in their activities, reducing the brightness and effect of what amateur astronomer Jake Alletson calls the “African sunset”.

“We have a real a problem,” said Alletson, who is chairman of the Natal Midlands centre of the Astronomical Society of Southern Africa, which operates out of an observatory above the city at World’s View. “The tall trees around us stop some of the glare from the city, but we really struggle.”

Alletson said dust and smoke in the air reflects light, creating a “light ceiling” over the city. This is particularly common during the winter when mist-free conditions are more conducive to sky watching.

Alletson describes his society as “helpless” in the face of light pollution. An environmental consultant by day, he said there is a lot the city could do to reduce light pollution, simply by “flicking some switches”.

“For a start, we could turn off the lights of office buildings at night and lights on billboards,” he said.

“I can’t put an exact figure on it, but I reckon we could take off a third to a quarter of our night- time nonessential power consumption. At a time when climate change is such a big issue, it seems unacceptable to be wasting so much energy,” he said.

Wasted energy isn’t the only reason to worry about light pollution. A growing body of scientific research suggests that darkness is just as important as light and excessive exposure to artificial light could have a range of negative effects on the health and wellbeing of humans and animals.

In humans, it can cause a disruption to the Circadian clock (the 24-hour day/night cycle) that is linked to several medical disorders, including depression, insomnia, cardiovascular disease and cancer, according to Paolo Sasone-Corsi, chairman of the pharmacology department at the University of California, Irvine.

Some research also points to a possible link between exposure of children to night light and myopia.

On birds and animals, and their natural environment, the effects are equally dire. Confused by lights on beaches, newly hatched sea turtles are known to navigate away from the sea and in the process become dehydrated, exhausted and overly exposed to predators.

A Canadian organisation called Fatal Light Awareness Programme (Flap) claims that an estimated 100 million birds in North America die each year when they fly into illuminated buildings.

If they manage to avoid this fate, Flap says many disoriented birds get “caught” in a beam of light, flapping around until they fall to the ground with exhaustion.

According to the International Dark-Sky Association’s fact sheet, light pollution disrupts all manner of natural behaviour, including mating and reproduction in fireflies and frogs. The fact sheet warns that “a season’s photoperiod [length of day] is the only consistent factor in the natural environment and many species of plants and animals rely on it to indicate the proper season for mating, moulting and other life-cycle activities.”

As the effects and awareness of light pollution increase, it is likely that its regulation will extend beyond the interests of astronomers.

According to University of KwaZulu-Natal’s Professor Michael Kidd, who specialises in environmental law, many developed countries are taking legal steps to protect the night sky.

“In the United Kingdom, for example, light pollution is recognised as a statutory nuisance. In terms of the Clean Neighbourhoods and Environment Act of 2005, exterior light which is deemed prejudicial to health or a nuisance can be acted upon,” he said. “In about 18 states in the United States, there is legislation governing light pollution.”

Kidd said that most laws on light pollution around the world have been motivated by the interests of large-scale astronomical observatories. For example, one of the first ordinances on light pollution to be introduced in the world in the late eighties was in Hawaii, home to two major observatories.

The ordinance required all new outdoor fittings to be low-pressure sodium lights, which produce a limited set of colours that can be filtered out by astronomers. It also controlled the hours during which other kinds of lights could be switched on and in some cases required the use of shields to prevent light from escaping upwards.

Since then, other countries with significant observatories have enacted similar laws, such as Spain’s 2002 Canary Island Sky Law, said Kidd.

And South African legislation is following much the same pattern. “While there is no legislation relating directly to the environmental effects of light pollution, we do have the Astronomy Geographic Advantage Act 21 of 2007,” said Kidd.

The act provides for the preservation and protection of areas that are uniquely suited for optical and radio astronomy through a reduction in light pollution or radio frequency interference.

According to Kidd, the act opens the door to the future regulation of light pollution.

“Clearly, the concerns [about light pollution] are no longer only confined to astronomy; they also extend to its impact on humans and biodiversity. In other countries, these issues have been raised and addressed through legislation and there’s no reason why this shouldn’t also happen in South Africa.”

Msunduzi conservation manager Rodney Bartholomew said although there are no written regulations or by-laws specifically relating to light pollution, measures to curb excessive light are part of the city’s broader plan to reduce the environmental impact of any new development.

Thus, upon viewing the draft environmental impact reports for a new housing development near Bisley Nature Reserve, the city stipulated that there should be no street lights and that where necessary, only downlighting should be installed so as to limit the impact on the neighbouring reserve.

Bartholomew said that once a recommendation is captured by the record of decisions issued by the Department of Agriculture and Environmental Affairs, it becomes a legal requirement.

He said the city had also, in the case of an existing development in Mkondeni, worked through the development’s environmental control officer to adjust lighting where concerns were raised about its impact on a population of dung beetles.

 

THE International Dark-Sky Association, which aims to “preserve and protect the night-time environment and our heritage of dark skies”, defines light pollution as any adverse effect of artificial light, including sky glow, glare, light trespass, light clutter, decreased visibility at night and energy waste.

THE good news is that of all modern-day pollutions, light pollution is the most easily remedied, through relatively simple changes to light design and installation.

According to the United States’s national park service, 50% of light from a typical unshielded light fixture is wasted, shining upward where it is not needed. About 40% of the light shines downward to illuminate the intended target and about 10% is lost in glare.

Good lighting is that which directs all light to where it is needed and wanted, usually down on the ground.

Thus, the International Dark-Sky Association recommends that all lighting be installed such that no light is emitted above a horizontal plane running across the lowest part of the fixture. IDA also recommends, wherever possible, the use of low-pressure sodium lights, which are the most energy-efficient lights available, although they make it difficult to distinguish colours of objects below. They also attract fewer insects.

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