Light Pollution Report by Geoff Dudley. Deputy Director Outdoor Lighting Improvement Section, Astronomical Society Victoria
What is it?
Light pollution is a general term, which encompasses all unwanted and unnecessary outdoor night lighting effects including glare, trespass, confusion and sky glow.
Why is it a problem?
Little attention has been directed toward the environmental and economic costs of light pollution. It is estimated that 2.5 percent of the total Australian electricity production is expended on night time outdoor lighting. About 30 percent of all outdoor night-time lighting ends up in the night sky.
This is equivalent to almost a billion kilowatt hours of electricity, more than the individual electricity production of many countries. About one half of light pollution arises from direct upward lighting and one half from reflections off the ground and buildings.
How much does light pollution cost the community?
Light pollution directly costs the country at least 80 million dollars a year in unnecessary electricity charges, in addition to the associated environmental harm from the mining and burning of fossil fuels to generate this wasted electricity. The equivalent of 397 million kilos of coal (or 266 million litres of oil) are burned annually in Australia simply to light up the night sky. The proper use of full, cut-off shielding, timers and appropriate light levels, if widely installed, could reduce the urban sky glow by at least a factor of four in the next few decades.
How does light pollution harm the environment?Light pollution harms the environment in four ways:
1. Urban sky glow hinders professional and amateur astronomy and deprives the public of its view of the night sky.
2. Coal, oil and nuclear fuels are mined and consumed in large amounts merely to light the night sky.
3. The monies spent on unproductive lighting of the night sky are not available for more worthwhile uses.
4. The fossil fuels burned to produce harmful lighting also contribute to air and water pollution. Over 80 percent of Australia's electricity production is derived from the burning of coal, much of which is obtained by open cut mining. Coal burning in itself is no small contributor to air pollution and acid rain. Thus, it seems rather short sighted for the country to allow its dark skies to be senselessly degraded by the consumption of non-renewable resources whose gathering and burning contribute nothing to the public good but further stress the environment.
How can we control light pollution?
Luckily, light pollution is relatively easy to control. Urban sky glow resulting from fixtures emitting light directly upward should no longer be tolerated. Efficient, full cut-off shielded fixtures are now available for most night lighting applications. Urban sky glow resulting from light reflected off the ground and buildings, as opposed to light shining directly upward in the sky, is more difficult to assess and control.
Some of it results from legitimate lighting necessary for night-time recreation, security and safety; even the most avid dark sky advocate wants properly lit major streets, highways and parking lots. Effective security lighting is also necessary in built-up urban areas. Nevertheless, much can be done to control upward reflected light by judiciously reducing the average light emission of most fixtures.
Billboard lighting and business signs should not be lit all night. Unnecessary lights ought to be turned off and security lighting should be kept to the level needed for the job, while streetlights, parking lot lights and security lights ought to use low-pressure sodium lamps (LPS). This light source offers the best economy of any source and is by far the least harmful to astronomy.
Such designs do not compromise night time safety, security and utility, but reduce energy waste, giving far less light pollution and light trespass and far darker skies. Efficient, full-cut shielded fixtures give more light on the ground and they require less wattage.
