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Artificial Light at Night (ALAN)
Lose the light to save the night!
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Outdoor lighting at night is part of modern life, and few of us can imagine living without it.


Yet outdoor lighting has a “dark side.” Natural cycles of light and darkness are essential to the proper functioning of ecological systems. Life on Earth evolved in conditions subject to only natural sources of light and is adapted to these natural cycles. Many plants and animals depend on these cycles for optimal health and even survival.


Evidence is mounting that artificial light at night (ALAN) affects the behavior, health, and abundance of various living creatures, thereby disrupting natural ecological processes.

At the April 10 meeting of Greener Glenview, Robert Sullivan, a visual resource consultant and recently retired from the Argonne National Laboratory's Environmental Science Division, spoke on the topic: Light Pollution at Night (ALAN) and Its Effects on the Environment and Human Health. His presentation is divided into four sections.

Video: The Dark Side of Light Pollution: Light Pollution and Its Effects on the Environment and Human Health

Section 1: Introduction and Overview  (18:00)

  • Provides an overview of Artificial Lighting at Night (ALAN) and discusses various aspects of ALAN including sky glow, light trespass, glare, light cheating and over-illumination, astronomical and ecological light pollution, and the social impact of light pollution. 


Section 2: ALAN and Melatonin (7:27)

  • Explores how ALAN impacts melatonin, a hormone that all living organisms produce in response to darkness. Learn about how exposure to ALAN suppresses the production of melatonin and significantly impacts biological processes in both humans and non-human animals.

Section 3: How Does Light Pollution Affect Animals and Plants? (21:19)

  • Provides details about the effect of ALAN on the health of individual animals.  ALAN alters processes and behaviors that are dependent on day length and light and dark cycles. Learn about how light pollution affects bats, sea turtles, birds, moths, and fireflies. Section 3 concludes with a discussion of the direct and indirect effects of ALAN on plants.


Section 4: What YOU Can Do About ALAN (8:50)

  • Provides the good news and bad news related to how we can impact ALAN. The presenter offers practical suggestions to reduce the impact of ALAN. Light pollution mitigation is highly effective, well-understood, straightforward, and expensive, and the technology exists today.

Section 5: Questions and Answers (25:00)

Dr. Sullivan answers a variety of questions from the audience. You can advance the video to the time code to listen to a speciic response.

  • (5:22): Is there a light meter for your phone to measure light?

  • (7:52): Glenview now is trending towards allowing exceptions to standards.

  • (10:00): Historic lighting and LED lights

  • (15:44): How to choose an outdoor light for your home in a store?

  • (19:30): The height of lights of outdoor lights for home

  • (22:23): Temperature of lights

  • (24:22): Change of time twice a year


Download the presentation handout: Help Pollinators, Plants, and Animals: Turn Out The Lights! 


International Dark Sky Association


"How Animals Perceive the World" (The Atlantic, July/August 2022)

"Our Nights are Getting Brights, and Earth is Paying the Price" (National Geographic, April 3, 2019)

"Chicago is the Most Dangerous City for Migratory Birds, Study Finds" (April 4, 2019)

"Artificial LIght is altering behavior of Chicago's urban wildlife, according to new study" (August 15, 2019)

"What is Kelvin and Why Do I Care About the K Number in Lighting?" (July 2, 2020)

"Mapping behaviorally relevant light pollution levels to improve urban habitat planning"

"Chicago Stargazers Want to Bring Back the Night Sky" (May 5, 2015)


Bogard, P. The End of Night: Searching for Natural Darkness in an Age of Artificial Light. London: Fourth Estate, 2013

Eklof, J. The Darkness Manifesto. New York: Scribner, 2022 (English translation)

Rich, C. and T. Longcore, eds.  Ecological Consequences of Artificial Lights.  Washington, DC: Island Press, 2006

Village of Glenview Lighting Standards

Glenview Municipal Code Chapter 98 (Zoning) Article V!!! (Performance Standards), Sec. 98-382 (Lighting)

Lighting Appearance Code and Design Guidelines

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