Protecting The Night For People And The Environment

Excessive and poorly controlled outdoor lighting can have detrimental effects on plants and animals, as well as people.

By Christina Halfpenny
From the April 2023 Issue

Since the first electric streetlights in the late 1800s, artificial outdoor lighting has enabled myriad human activities, from navigation and work to sports and celebration. Today, outdoor light at night is so pervasive and essential to our 24/7 culture that many go about their after-dark pursuits without giving it a second thought.

There’s growing awareness, however, to the need to balance society’s reliance on quality outdoor lighting with the important function darkness plays in the lives of all living things. Plants and animals, as well as people, depend on the natural rhythms of the sun and moon to thrive.

outdoor lighting
(Photo: Adobe Stock)

The Impact Of Poor Outdoor Lighting

Right now, for example, the night sky is a superhighway for migrating birds—over three billion of them over the course of the early spring are winging their way from wintering grounds to breeding and nesting areas across the U.S. and Canada, according to Cornell University’s Lab of Ornithology. As they have for millennia, most complete these journeys at night, relying on the stars to navigate. Those guideposts are obscured, however, by excessive and poorly controlled outdoor lighting. Confused and distracted by light from illuminated building facades, parking lots, roadways, and other sources, birds lose their way, collide with lit up buildings or circle cones of artificial light to the point of exhaustion.

At a critical time for bird conservation, in the wake of a study chronicling a nearly 30% decrease in North American bird populations since 1979, Cornell’s BirdCast program estimates 365 million to 988 million birds die in collisions with buildings annually. Even isolated places offer little sanctuary. In Hawaii, the most remote population center on Earth, the U.S. Fish and Wildlife Service reports that over 1,200 fledgling seabirds were rescued between 2020 and 2021, and over 900 in 2022, fallen from the night sky after being attracted to and “trapped” in artificial light.


Confused and distracted by light from illuminated building facades, parking lots, roadways, and other sources, birds lose their way, collide with lit up buildings or circle cones of artificial light to the point of exhaustion.



Impacting the natural behaviors of wildlife species from insects and reptiles to mammals—as well as the well-being of some human communities, light pollution comprises three components:

  • sky glow from light scattering in the atmosphere from light fixtures and reflections;
  • light trespass from light spilling beyond property boundaries; and
  • glare that can include light scattering in the eyes that interferes with visibility, overly bright light that causes discomfort, and nuisance glare that is simply distracting and unwanted.

Overall, it’s a fast-growing problem. Light pollution has increased at a yearly rate of about 10% in North America since 2011 according to a January 2023 study. The World Atlas of Artificial Night Sky Brightness, published in 2016, found that more than a third of Earth’s population, including 60% of Europeans and nearly 80% of North Americans, can no longer see the Milky Way.

Improperly designed outdoor light at night also causes building owners and managers to use and pay for more energy than they need—about $3.3 billion worth, according to the International Dark Sky Association, which cites data indicating that a third of all outdoor lighting in the U.S. is wasted and therefore responsible for an unnecessary 21 million tons of carbon emissions annually.

Strategies To Mitigate Light Pollution

The good news is that light pollution is a challenge with available solutions. By following seven basic strategies, commercial facility operators, municipal building managers, colleges and universities, and others can help mitigate the unintended consequences of light pollution. In order of importance, these include:

  1. Use outdoor lighting that is dimmable and compatible with networked lighting controls.
  2. Consult with local experts and residents to identify and address any specific local concerns.
  3. Use only the right amount of light; avoid overlighting.
  4. Use lighting controls to reduce energy use and light pollution.
  5. Control lighting to respond to seasonal changes in the environment (less light during bird migration, for example).
  6. Control the distribution of light (avoid uplighting by shielding lights downward, for example).
  7. Minimize use of blue-violet light which scatters into the atmosphere more easily than does “warmer” red-amber light.

One way lighting decision makers can check several of these boxes is by choosing fixtures on the DesignLights Consortium’s (DLC) LUNA qualified products list (QPL) and installing these following best practices for responsible light at night. The DLC is a nonprofit that collaborates with utilities, energy efficiency programs, manufacturers, lighting designers, building owners, and government entities to create technical requirements for the performance of commercial and industrial lighting products. Products that validate that they meet these criteria through third-party testing are added to the DLC’s QPLs, which serve as the basis for many commercial lighting energy efficiency rebate programs across the U.S. and Canada.

outdoor lighting
(Photo: Adobe Stock)


After releasing its LUNA Version 1.0 Technical Requirements for outdoor LED luminaires in December 2021, the DLC approved the first products for the LUNA QPL last summer. In addition to meeting the DLC’s efficacy thresholds for LED lighting, LUNA-qualified products must comply with additional dimming, control, and shielding requirements. The LUNA program also introduces requirements for light distribution, correlated color temperature, and dimming controls to reduce light trespass and sky glow. The policy ensures that qualified products are both energy efficient and minimize light pollution, while also providing appropriate visibility for people.

Done properly, outdoor lighting benefits society in many ways. Complications and challenges arise when artificial nighttime lighting is misdirected and used in excess without sufficient regard for surrounding environments. The unintended impacts to human communities range from annoyance to interference with public safety and natural cycles of sleep. For birds and other wildlife that depend on nighttime darkness for various natural behaviors, the negative implications can be more dire and long-lasting at both species and ecosystem levels.

outdoor lightingDeveloping Tech Requirements For Outdoor Lighting Looks To The Night Sky

First draft of LUNA (Light Usage for Night Applications) requirements from DesignLights Consortium establishes performance thresholds for specific categories of outdoor lighting to minimize light pollution. Read more…

On the bright side, there are off-the-shelf options that lighting decision makers can use right now to mitigate the negative effects of light pollution, while simultaneously reducing their electricity use and cost. By using the right products and following procedures aimed at using the right amount of light only when and where it is needed, commercial and industrial facilities can help drive appropriate, responsible, and economical lighting solutions for people, their communities, and the environment.

Christina Halfpenny DesignLights ConsortiumHalfpenny is Executive Director and CEO of the DesignLights Consortium (DLC), a non-profit organization improving energy efficiency, lighting quality, and the human experience in the built environment. She drives success through strategic planning, stakeholder engagement and collaboration, and continuous improvement of business systems.

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