Dark Skies Are Coming

In worldwide terms, 'Dark Skies' is becoming a common phase. It is in large part due to the success of the International Dark Sky Association (IDA), a US based international organisation of 10,000 members with headquarters in Tucson, Arizona. IDA was started in 1988, and although it was initially formed by astronomers from Kitt Peak and other observatories to address the adverse affects of electric lighting on astronomy, IDA has evolved to a broad membership determined to address the many problems of outdoor lighting across all public and professional boundaries. The dark sky movement is focused on eliminating light pollution, which is a general term for unwanted or wasted light. Artificial sky glow is the portion of light pollution that is a combination of direct uncontrolled light and high levels of reflected light going up into the atmosphere. This stray light is reflected by atmospheric water particles and particulates, leaving only the brightest stars visible in the night sky.

Also, dark sky enthusiasts are interested in reducing obtrusive light, also called 'light trespass'. Obtrusive light is the portion of light pollution responsible for the neighbour-to-neighbour complaint of 'light shining in my window'. It is also responsible for the photobiological impacts on living creatures and for disability glare that can cause impaired visual performance among drivers and pedestrians. Because obtrusive light is easily detected by the naked eye, it is often the focus of most lighting regulations.

Like other forms of pollution, outdoor light was at first seen as good, a sign of progress and a source of community pride. The damage went unrecognised for many years, and poor lighting practices were overlooked or in many cases, rewarded. Increasing population and urban sprawl exacerbate the situation by constantly requiring more lighting, and increasingly efficient light sources make ever-higher light levels possible without extreme expense.

The first indication of light pollution was the loss of the night sky due to artificial sky glow. Astronomers found their work increasingly difficult as the light of encroaching population caused a dramatic reduction in the ability to observe the stars. In turn, amateur astronomers and laypersons also became aware, and the groups joined together to address the problem, creating the IDA.

Meanwhile, obtrusive light has become a rallying issue for communities. Careless lighting practices became intrusions as efficient light sources and luminaires allowed very high light levels without the high costs of equipment or energy. The growth of interest in night sports and the belief that lighting serves as a form of security has caused the number and intensity of outdoor lighting systems to grow exponentially. Also, many communities have sought street lighting systems to create overly bright streets as a sign of progress, and merchants have used light to identify their businesses during the extended business day through bright lights and electric signs. It has become a race to achieve the brightest light in the community, with some car lots having electric light levels exceeding the light levels in a hospital operating room. But perhaps the most critical issues demanding change are environmental. Light pollution is caused principally by wasted or 'spill' light. It is estimated that more than 33% of the electric light generated for outdoor use is simply waste. Light pollution has been shown to directly affect wildlife, ranging from bacteria to mammals, with a variety of results. For example, light pollution will attract and misdirect sea turtle hatchlings, often resulting in their death. Lighting of tall buildings will disorient migrating birds, causing some to fly about in circles until plunging to their deaths. Other serious impacts have been reported on fish migration, reptile populations, and even humans.

In order to control light pollution, numerous laws have been written worldwide, ranging from local laws in small towns to national law in the Czech Republic. Too often written by well meaning and passionate community members, the vast majority of existing light pollution laws are technically faulty, impossible to enforce, and worst of all, different from community to community. Perhaps the most effective laws are in Tucson, where light pollution is 75% less per capita than average larger American cities. But the Pima County (Tucson) laws are too complex for a small town like Hailey, Idaho (pop <2000), where local dark sky advocates led by a local physician nicknamed 'Dr. Dark' have imposed one of the most rigorous standards in North America in order to protect their relatively pristine night environment.

The IDA has been working to develop a more universal solution. For several years, it has made available many documents on its web site, including copies of several lighting ordinances and a Handbook for ordinance and code writers. Recently, the IDA has announced the National Outdoor Lighting Code, a model code suitable for adoption by cities and other governing bodies. The concept is to improve enforcement by creating a single universal code. One code permits education and enforcement on a broad scale, much like the electrical or building codes. Versions for small cities (like Hailey) and large cities (like Tucson) permit a level of technical complexity commensurate with the need. Versions that include metric units make the document easily exported from the American ('Imperial') system of feet and foot-candles to the metric system and most of the world's nations and communities.

The dark sky movement poses a serious challenge to the professional lighting community. The vast majority of dark sky advocates do not understand even the most basic lighting terms, yet they are passionate and capable of getting lighting laws passed. If the professional lighting community fails to act to control the carelessness and excesses of outdoor lighting, others will. We can no longer sit back and wait to see what happens.

Both authors of this article have chosen to join and serve on the Board of the International Dark Sky Association. Its executive director, Dr. David Crawford, is an IESNA Fellow and widely known as a visionary. Other IDA leaders share Dave's wisdom in coming to the lighting community to find a common solution. Current members of the IDA Board include four IESNA Fellows, two IALD Professional Members, and four practicing professional engineers (PE) in the US. The message is this - the lighting community has one bona fide chance to join the dark sky movement and make its work a collaborative effort that permits lighting design while curtailing the thoughtless, wasteful practices that constitute the majority of outdoor lighting. The National Outdoor Lighting Code is the first collaborative product to see the light of day. It deserves the support of the lighting community.

information : www.iald.org