The Dark Sky Challenge and Dilemma

By James R. Benya, PE, FIES, FIALD

Among the many challenges facing lighting designers today is the light pollution caused by outdoor lighting. Mitigating light pollution is promoted by most environmental-responsibility standards like LEED and is required by code in particularly sensitive locations.

In California, Title 24 restricts the amount and type of lighting in the entire state in a manner similar to zones described in the Model Lighting Ordinance (MLO), jointly developed by the IES and DarkSky International 13 years ago. Restrictions are also emerging throughout much of the world now, and many use the BUG rating system first introduced by the MLO or similar concepts.

The first concerns about light pollution were raised by astronomers. They found their work impacted by anthropogenic [1] sky glow which was increasing over time, and action was required to preserve the viability of the observatories.

Leading them was Dr. David Crawford (1931- 2024), a world-class astronomer who, in the 1970s, was the Director of Kitt Peak National Observatory. “Due to his life-long efforts advocating for dark skies and against light pollution, he is regarded as one of the greatest environmentalists of the late 20th and early 21st centuries.” [2]

Dave and Dr. Tim Hunter founded DarkSky International (née the International Dark Sky Association, aka IDA) in 1988. Retiring from Kitt Peak, Dave devoted the rest of his career to IDA and taking action to fight off light pollution.

Like most people in the early years of the dark sky movement, Dave was first a world class astronomer who, like many of his colleagues, was frustrated with light pollution and its effects on astronomy.

He originally focused on the lack of clarity of the night sky for astronomy caused by anthropogenic light. Turn off all the electric lights and, weather permitting, behold! A pristine night sky. This reinforced the start of the “fully shielded” street lighting movement, made ever easier by LED lighting.

Starting in the early 1980s, Dave set out to fix the problem. He was a resourceful person to whom it was hard to say no. He engaged a number of “lighting people” in the 1990s to help, both by bringing expertise and by doing work of which Dave and other astronomers were not sufficiently knowledgeable. It was called “getting Daved”.

Among lighting industry persons, it appeared to have started with Chris Monrad and Nancy Clanton, if I recall correctly. But soon enough, I was among several lighting professionals lassoed into serving as an IDA Board Member and, in my case, co-chairman of the committee for a lighting ordinance.

Dave believed that a model code was critically important. I posited that a model code needed the official support of the IES, and in 2005, Nancy Clanton and I convinced the IES Board that an MLO should be co-developed by IES and IDA.

There were concerns from the Roadway Lighting Committee and quite a few individual members and outdoor lighting companies, but in the end, the Model Lighting Ordinance task force was created and the document published in 2012, with equal representation of IDA advocates, technical representatives, IES member roadway lighting experts, and lighting manufacturers.

It was written to be adopted by communities and modified with their own specific concerns and considerations. A good example is the Malibu Dark Sky Ordinance, [3] where the community leaders and members worked to simplify the MLO to Malibu’s specific issues.

Of course, there are thousands of different types and styles of outdoor luminaires, many having unique characteristics well suited for protecting the night sky. But there are significant differences in photometry among candidate luminaires, even those that are marketed as “dark sky” lighting products.

Because the MLO was written by lighting professionals, fluency in photometry was not a problem for them, and a system for rating and restricting luminaires was devised that includes:

• Limits to backlight (B), uplight (U), and glare (G) based on photometry using the “BUG” system [4]

• Spectral limits to prevent short wavelength emissions

• Limits to total site illumination-based area of tasks

In the MLO, there were originally four lighting zones (LZ1, LZ2, LZ3 and LZ4, in order from most stringent to least stringent) based on evolving lighting technology and appropriate lumen output to coincide with energy codes that would limit the lighting power density (LPD) based on task and lighting zone.

Lighting Zone zero (LZ0) was added to describe a location where lighting is inappropriate with exceptions for human safety, security and wellness. For example, a restroom or trailhead in a wilderness area (LZ0) can be lighted if the BUG rating of the luminaire is for LZ1 (B1, U1, G1 or better) and there is no other lighting unless equally necessary for safety.

The biggest challenge in designing lighting to comply occurs at the boundary between areas being lighted and those not being lighted. A good example is where lighting for a building façade or entrance canopy “trespasses” onto the street or an adjacent property, especially if the adjacent property has a lower illuminance allowance or is in a different lighting zone.

Because lighting design professionals were instrumental in developing the MLO, it has exceptions, provisions, and clear language about how to achieve the end goal of outdoor lighting being just enough with mitigated off-site impacts and little or no uplight.

With practice and patience, most lighting professionals can conquer the challenges of most sites.

However, special allowances and interpretations may still be needed. For example, California integrated the MLO into its building code, Title 24, and it is used statewide every day. In my practice, working with communities along the California coast where the entire community wants to be Lighting Zone 1 and the beaches are Lighting Zone Zero (no anthropogenic lighting except at trailheads and restrooms and aid stations), so some additional exceptions are needed.

In Malibu, exceptions were developed to permit gas station canopy lighting along Highway 1 to trespass onto the curb and outer lane of the road and to allow for increased parking lot, driveway, and street light trespass for safety situations such as crosswalks.

Most recently, my dark sky work involved digital signs and billboards. Digital signs employ clusters of RGB or RGBW LED emitter arrays into display modules that produce light aimed outwards and slightly downwards, like a matrix of computer displays without apparent joints. In several instances, I have measured the luminance of commercial arrays to be as high as 10,000 cd/m2 perpendicular to the plane of the sign or billboard panel, capable of producing measurable illumination levels in the vertical plane hundreds of feet away.

The first concerns about light pollution were raised by astronomers. They found their work impacted by anthropogenic sky glow which was increasing over time, and action was required to preserve the viability of the observatories.

I measured the luminance of one outdoor video billboard at 8,000 cd/m2 peak at night, many times more than an appropriate amount of luminance. Needless to say, the light trespass onto adjacent properties was exceptionally high. If it were a light, it would never have been permitted by that community’s lighting ordinance.

Likewise, LED artistic and commercial lighting effects, especially bridges and building facades, need to addressed, and I think we as an industry need to work closely with the sign industry now and in the future because, like in most environmental matters, I think we still have a lot to do in the field of lighting.

Light vs. Life:

Light pollution is not just about astronomy and star gazing. Environmental biologists were also concerned, having discovered impacts of anthropogenic light on a whole host of living beings, from plants and insects to turtles and birds. Dr. Travis Longcore [5] wrote a landmark article entitled “Ecological Light Pollution” (Longcore and Rich 2004), and in 2006, published Ecological Consequences of Artificial Night Lighting (Island Press).

Both the article and subsequent book came to define another dimension in the new and rapidly growing research area in ecology. Travis documented the impacts of light pollution on terrestrial and waterborne beings. A good example was a major bridge lighting project in Southern California that was stopped when Dr. Longcore challenged the environmental impact statement.

Since then, research has identified significant impacts on many species and resulted in a number of specific regulations for the primary benefit of endangered species, notably the State of Florida where the Department of Environmental Protection [6] requires communities to adopt and enforce an ordinance restricting light on or near beaches to protect sea turtle beach habitats.

Lights that Lure:

The Towers of Light in New York is one of the most powerful memorials ever made using only light. I freely admit to being overwhelmed when I first saw it.

But, I was not surprised when, due to periodic mass deaths of migratory birds, the memorial was limited to the night of September 11. According to FLAP, [7] the Fatal Light Awareness Program, “Hundreds of species of birds migrate at night. If the skies are clear and their path is moonlit, these migrants will often fly at high altitudes avoiding any possible obstructions. But the lights of 20th century society can be confusing to them, especially on foggy, rainy nights or when cloud cover is low. Then they may fly directly into tall lighted structures such as skyscrapers, transmission towers, monuments, lighthouses and the like. Where spotlights are shone into the night sky the birds fly "into" the light and become "entrapped", unable or unwilling to fly out again. Eventually, exhausted, they fall to the ground.” [8]

A related problem occurred in Redding, California. The Sundial Bridge over the Sacramento River by Santiago Calatrava was illuminated by artistic LED lighting post-completion. After several years of low chinook salmon runs following the lighting installation, environmentalists undertook to determine the reason. [9]

The culprit proved to be under-bridge lighting that dramatically increased predation and decreased the chinook population. Reducing or eliminating bridge lighting during runs and reducing lighting in general allowed the river’s ecology to recover.

References:

[1] Man-made

[2] "How legendary dark-sky advocate David Crawford sparked the fight against light pollution". Astronomy.com. August 5, 2024 from Wikipedia

[3] https://www.malibucity.org/705/Dark-Sky-Ordinance

[4] Backlight, uplight and glare (BUG) with specific limits on zonal photometry of the luminaire determine acceptable luminaires. Lighting power density (LPD) is then used to determine whether recommended illuminance levels are met.

[5] Adjunct Professor, UCLA Institute of the Environment and Sustainability

[6] MODEL LIGHTING ORDINANCE FOR SEA TURTLE PROTECTION

[7] https://flap.org/

[8] https://digitalcommons.unl.edu/flap/2/

[9] https://www.cafishpassageforum.org/wp-content/uploads/2023/09/Fish-Passage-Effects-of-Artificial-Light-A.-Jensen.pdf

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