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03-22-22 | Feature

Maintaining a "Dark Sky"

Light Pollution
by by Mike Dahl, LASN

Excessive lighting over Portugal mixed with smog creates "sky glow" which invades populated areas and hides the natural night sky. It is made stronger by clouds, rain, pollutions, and fog.
2003 Photo Credit: NASA - These graphics show ambient lighting in the United States in 2003, 2012, and 2021. Over these time intervals, light pollution has increased throughout the country, providing a strong case for the necessity for "Dark Sky" focused outdoor lighting.
2012 PHOTO CREDIT: SCIENCE PHOTO LIBRARY - These graphics show ambient lighting in the United States in 2003, 2012, and 2021. Over these time intervals, light pollution has increased throughout the country, providing a strong case for the necessity for "Dark Sky" focused outdoor lighting.
2021 PHOTO CREDIT: NBC - These graphics show ambient lighting in the United States in 2003, 2012, and 2021. Over these time intervals, light pollution has increased throughout the country, providing a strong case for the necessity for "Dark Sky" focused outdoor lighting.
Lighting pollution is also known as light trespass and comes in different forms such as glare, which is light that shines horizontally. This example of glare shows an iconic landscape with lighting fixtures that are open and therefore illuminate in every direction,which might not have been built under today's dark sky standards.
Leo Smith, who specializes in consulting public and private entities on outdoor lighting techniques that promote "dark sky" methods, advises that municipalities should implement streetlight warranting policies to help identify where they are necessary or where they can be. These area lights from LADetails shield the bulb at the top, so the light only shines downward, limiting lighting pollution.
Leo Smith, who specializes in consulting public and private entities on outdoor lighting techniques that promote "dark sky" methods, advises that municipalities should implement streetlight warranting policies to help identify where they are necessary or where they can be. These area lights from LADetails shield the bulb at the top, so the light only shines downward, limiting lighting pollution.
Leo Smith, who specializes in consulting public and private entities on outdoor lighting techniques that promote "dark sky" methods, advises that municipalities should implement streetlight warranting policies to help identify where they are necessary or where they can be. These area lights from LADetails shield the bulb at the top, so the light only shines downward, limiting lighting pollution.
Another form of light trespass is clutter - light that is too intense for the circumstances.
Dabmar Lighting Area/Street Fixtures
The impact that artificial light has on the natural environment includes interrupting the cyclical rhythms of plants such as this tree (inset) whose leaves near the streetlight remain, even after all other leaves have fallen off. This park in Bursa, Turkey features evergreen trees which retain their leaves year round, so the artificial lighting from the fixtures has minimal effect on their cyclical rhythms. An even better option, though, would be to place the lights on the other side of the walkway facing away from trees.
The impact that artificial light has on the natural environment includes interrupting the cyclical rhythms of plants such as this tree (inset) whose leaves near the streetlight remain, even after all other leaves have fallen off. This park in Bursa, Turkey features evergreen trees which retain their leaves year round, so the artificial lighting from the fixtures has minimal effect on their cyclical rhythms. An even better option, though, would be to place the lights on the other side of the walkway facing away from trees.
The impact that artificial light has on the natural environment includes interrupting the cyclical rhythms of plants such as this tree (inset) whose leaves near the streetlight remain, even after all other leaves have fallen off. This park in Bursa, Turkey features evergreen trees which retain their leaves year round, so the artificial lighting from the fixtures has minimal effect on their cyclical rhythms. An even better option, though, would be to place the lights on the other side of the walkway facing away from trees.
The International Dark-Sky Association and the Illuminating Engineers Society established five principles of responsible outdoor lighting.

We all depend upon light, much of it artificial, for our modern existence and comfort. But too much of it can be a bad thing. The overuse, and inefficient use, of the lights we install leads to what is known
as light pollution.

Leo Smith specializes in consulting public and private entities on the use of lighting fixtures and controls to reduce this problem.

"Improving the quality of night lighting by reducing excessive and unnecessary light pollution has environmental benefits that can be achieved with little or no additional costs to the lighting project," he states.

Smith recently gave a presentation that was sponsored by the Coalition for a Sustainable Cheshire (Connecticut) and the Cheshire Public Library. Following are the highlights of that report.
Sources of Light Pollution
Light pollution, artificial light that goes where it is not intended to go, is also known as light trespass. Light that trespasses horizontally, also known as glare, can temporarily blind drivers and creates harsh shadows. When too much artificial light is used to do the job at hand, it is termed clutter.

Another form of light pollution is sky glow - that orange cast over a city that obscures the natural night sky. Clouds, rain, air pollution and fog intensify sky glow.

Sources of Concern

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According to Smith, there are two main motivations that are driving the effort for light pollution control. First and foremost are the adverse consequences light pollution has on the health of humans, wildlife and plants. Second is the increased interference with astronomical observation.

The concerns for wildlife include habitat disturbance, wildlife behavior and indeed, wildlife survival. For example, artificial light contributes, annually in North America, to an estimated one hundred million bird deaths, attributed to them being entrapped by light at night and colliding into windows, and thousands of sea turtle hatchlings die each year from the undesirable effects of artificial light.

In fact, a very large portion of animals are nocturnal, so their very survival depends on the darkness of night. This includes one hundred percent of bat species and over ninety five percent of amphibian species. For nocturnal frogs, a quick increase in illumination causes a reduction in visual capability from which the recovery time may be minutes to hours. And after becoming adjusted to a light source, they may be adversely attracted to it as well.

There is evidence that light pollution can also affect the mating habits of wildlife, leading to enfeebled offspring. A study conducted at Ohio State in 2017 found that when hamster parents were exposed to dim light levels prior to mating, the resulting broods experienced deficient embryonic development and weakened immune systems.

As has been well documented, sea turtles emerging from their eggs on the beach, compelled by nature to make their way to the strongest source of light, which at night in the absence of artificial illumination is the ocean reflecting the light of the moon and stars, will wander towards manmade illumination, putting themselves in the path of peril from predators and vehicles.
Artificial lighting is also extremely detrimental to many insect populations as it disrupts normal flight activity and long-distance migrations. It's disruptive effects also include attracting insects that don't normally move from their habitat, effectively trapping them so they might be killed by predators or by the lamp's heat.

Smith points out that these "light traps are very likely changing the diversity of insects. If a particular species does not reproduce rapidly enough to make up for the loss at the lights, it may disappear from the community."

Why does this matter? The impact results in loss of insects that are important pollinators and allows predators of nuisance bugs to be damaging to human communities as well.

Effects to Humans
One third of all human food requires a pollinator. And many of the plants that provide us food are pollinated by nocturnal insects or small animals, moths and bats. So, "altering the lighting conditions at night can further unravel our web of life, which ultimately disrupts our food sources," attests Smith.

One has to realize that light at night is very recent in human history: only the past 120 years compared with 50,000 years of relatively bright days and dark nights.

Making Progress
There has been improvement in the last two decades in the effort to fight light pollution. For example, more federal grants from the National Institute of Environmental Health Science have been directed to light at night research according to Smith. In 2001, Connecticut, where Smith is located, enacted a law that requires all new streetlights to be fully shielded on all state and municipal roads. Later the state's Public Utilities Control Authority approved a new rate for streetlight that turn off at midnight. And Smith praises Connecticut's state building code light pollution control amendment that affects new commercial buildings and parking lots, as well as renovations on existing building and parking lots: requiring that exterior lighting be fully shielded.

The American Medical Association (AMA), in 2009, advocated that all outdoor lighting be of energy efficient designs to reduce waste of energy and production of greenhouse gasses that result from the wasted energy use of non-energy efficient lighting. The AMA also promoted the development of policies that support light pollution and glare reduction efforts at both the national and state levels. And they supported the policy that all future streetlights be of a fully shielded design or similar non-glare design to improve the safety of our roadways, especially out of concern for vision impaired and older drivers. In 2016, the AMA issued a notice in regard to the environmental effects of LED community lighting. In it they encouraged the use of lighting with a color temperature of 3000K or lower for outdoor installations in an attempt to limit blue light. They also advised that all LED lighting be properly shielded to minimize glare and detrimental human and environmental effects, and that consideration should be given to dimming LED lighting for off-peak time periods.

"Less Is More"
One of the ways that lighting designers can help lessen the problem of light pollution, according to Smith, is to include timers or motion sensors to extinguish light when it makes sense. And use outdoor shielded light fixtures, what he terms as "good neighbor lighting."

He also contends that, "many streetlights are a waste of energy because they provide no increase in collision avoidance."

His advice is to adopt a municipal streetlight warranting policy to help identify where streetlights are necessary or where streetlights can be turned off after midnight.

And to reduce light pollution in outdoor residential environments, Smith recommends using shielded fixtures, timers to avoid leaving lights on all night and avoiding "over-lighting." In other words, less is more.

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