19 Aug 2013: Report

Bringing Back the Night:
A Fight Against Light Pollution

As evidence mounts that excessive use of light is harming wildlife and adversely affecting human health, new initiatives in France and elsewhere are seeking to turn down the lights that flood an ever-growing part of the planet.

by paul bogard

Last month, France — including the City of Light — grew darker late at night as one of the world’s most comprehensive lighting ordinances went into effect.

From 1 a.m. to 7 a.m., shop lights are being turned off, and lights inside office buildings must be extinguished within an hour of workers leaving the premises. The lighting on France’s building facades cannot be turned on before sunset. Over the next two years, regulations restricting lighting on billboards will go into effect. These rules are designed to eventually cut carbon dioxide emissions by 250,000 tons per year, save the equivalent of the annual energy consumption of 750,000 households, and slash the country’s overall energy bill by 200 million Euros ($266 million).

But no less a motivation, says France’s Environment Ministry, is to “reduce the print of artificial lighting on the nocturnal environment” — a powerful acknowledgement that excessive use of lighting in many parts of the world is endangering our health and the health of the ecosystems on which we
The good news is that light pollution is readily within our grasp to control.
rely. The good news, however, is that light pollution is readily within our grasp to control.

Until recently, efforts to restrain our use of light have been primarily in response to the astronomical light pollution erasing starry nights. But researchers are increasingly focusing on the impacts of so-called ecological light pollution, warning that disrupting these natural patterns of light and dark, and thus the structures and functions of ecosystems, is having profound impacts.

The problem is worsening as China, India, Brazil, and numerous other countries are becoming increasingly affluent and urbanized. Satellite views of Earth at night show vast areas of North America, Europe, the Middle East, and Asia glowing white, with only the world’s remotest regions — Siberia, the Tibetan plateau, the Sahara Desert, the Amazon, and the Australian outback — still cloaked in darkness. Some countries, such as Britain, and some U.S. states — including Connecticut and California — have enacted regulations to reduce light pollution, but most nations and cities still do little to dial down the excessive use of light.

Technological advances such as LEDs, or light-emitting diodes, can improve our ability to reduce and better regulate lighting, but these same new lights may actually make things worse because they contain heavy doses of a “blue-rich” white light that is especially disruptive to circadian rhythms.

Scientists are investigating new ways to provide society with the lighting it demands for security, commerce, and aesthetics, while greatly reducing the flood of light that is increasingly interfering with human health and the ability of many creatures to function. One research group funded by the German government — Verlust der Nacht, or Loss of Night — is coordinating numerous studies on light pollution, ranging from research into the socio-political challenges of cutting light pollution in the Berlin metropolitan area to the effects of light pollution on nocturnal mammals.

View gallery
San Francisco Light Pollution

Thomas Hawk/via Flickr
A nighttime view of San Francisco.
Some 30 percent of vertebrates and more than 60 percent of invertebrates are nocturnal, and many of the rest are crepuscular — active at dawn and dusk. All are potentially impacted by our burgeoning use of artificial light, scientists say. “We have levels of light hundreds and thousands of time higher than the natural level during the night,” explains Italian astronomer Fabio Falchi, a creator of the World Atlas of the Artificial Night Sky Brightness, the computer-generated maps that dramatically depict the extent of light pollution across the globe. “What would happen if we modified the day and lowered the light a hundred or a thousand times?” That would be much worse, he concedes. But his point? “You cannot modify [light] half the time without consequences,” says Falchi.

Every flip of a light switch contributes to altering ancient patterns of mating, migration, feeding, and pollination, with no time for species to adapt. On the Caribbean island of Tobago, a 2012 study of leatherback turtles — a species that has been on Earth for 150 million years — found that “artificial lighting of the nesting beaches is the biggest threat to survival of hatchlings and a major factor in declining leatherback turtle populations.” Evolved to follow the reflected light of the stars and moon from the beach to the ocean, hatchlings now instead follow the light of hotels and streetlights, with the result that they die of dehydration, are devoured by predators, or run over by cars.

Many migrating birds, drawn off-course by artificial light, join the breathtaking number — between 100 million and 1 billion, we don’t really know — killed each year by collision with human-made structures. For moths, which help pollinate the world’s flora, our outdoor lights are irresistible flames, killing countless moths and other insects, with ripple effects throughout the food chain.

Other recent studies show that for bats — whose natural pest control benefits U.S. agriculture alone by billions of dollars annually, according to
Every flip of a switch alters ancient patterns of mating, migration, and feeding.
a 2011 study in Science — artificial light disrupts patterns of travel and feeding since many bat species avoid illuminated areas. Recent articles on a menagerie of species reflect a new awareness of artificial light’s effects on ecology. For example, research has shown that street lighting influences the migratory pattern of Atlantic salmon, and that bright lights also change the composition of entire communities of insects and other invertebrates.

Of course, “humans are animals as well,” explains Steven Lockley of Harvard Medical School’s Division of Sleep Medicine, “and so when light/dark cycles mess up seasonal patterns of trees or breeding cycles of amphibians, there’s no reason to think it’s not doing the same to us.”

As recently as 1980, humans were thought to be immune to the effects of artificial light at night. But continuing research has shown that nocturnal light disrupts our sleep, confuses our circadian rhythms — those 24-hour biological processes that regulate our body’s functions — and impedes the production of the hormone melatonin at much lower levels than previously thought possible.

More and more of the light we see at night — whether electronic gadgets or outdoor lighting — is rich with the blue wavelengths most disruptive to our body’s rhythms. (More than any other wavelength, blue wavelength light tells our brain that night is over, that morning’s blue sky has returned, and that the day has begun — the opposite signal that we want to be sending our brain in the middle of the night.) Studies continue to suggest that the consequences of excessive exposure to light at night include an increased risk for obesity, diabetes, and cardiovascular disease. Last year, the American Medical Association issued a statement calling for increased research into the “risks and benefits of occupational and environmental exposure to light-at-night,” and recommending “new lighting technologies at home and at work that minimize circadian disruption.”

View gallery
Street Light Glare Bomb

Kevin Wigell
A streetlight in upstate New York casting a so-called “glare bomb.”
In fact, researchers are concerned about the impact of some new lighting technologies. While their capacity to be computer-controlled and directed could make LEDs a key tool in reducing light pollution, these lights may actually make things significantly worse. Touted as energy-efficient and clearer in color, most LEDs currently being installed are often brighter than the old lights they are replacing, further increasing light pollution. In fact, explain Falchi and others in a recent article from the Journal of Environmental Management, LEDs could “exacerbate known and possible unknown effects of light pollution on human health (and the) environment” by more than five times.

Researchers and dark-sky advocates are seeking to mitigate the harmful effects of new lighting technologies and devise solutions to the flood of light that erases the night in many parts of he world. The International Dark-Sky Association and the Illuminating Engineering Society of North America have together designed the Model Lighting Ordinance, which communities of any size can adopt. The MLO recommends limits for the amount of light in five different zones of lighting intensity. The ordinance also recommends banning unshielded lighting in all zones.

In the Journal of Applied Ecology, researchers have identified numerous practical steps to reduce light pollution: changing the spectral composition of lighting (especially LEDs), limiting the duration of lighting, reducing the “trespass” of lighting into areas not intended to be lit, altering the intensity of lighting, and preventing areas from being artificially lit in the first place.

The relatively simple act of shielding our lights — installing or retrofitting lamp fixtures that direct light downward to its intended target — represents our best chance to control light pollution. While we seldom
Light pollution continues to grow at up to 20 percent, depending on the region.
leave our interior lights bare, most of our outdoor lighting remains unshielded, sending light straight into the sky, into our eyes, into our neighbors’ bedrooms. Until recently, consumers had few buying choices, but that is changing. Companies such as Lowe’s, the home-improvement chain, now offer lines of shielded lighting fixtures. Street lighting, stadium lighting, parking lot and gas station lighting — all can be now be shielded.

The objection will be that we need all this light for safety and security, with the justification that light equals safety, and darkness danger. This common belief goes far to explain why many gas stations and parking lots are lit more than ten times as brightly as they were just 20 years ago, and why light pollution continues to grow at up to 20 percent per year, depending on the region. In fact, the issue of light at night and safety is complex, with little compelling evidence to support common assumptions. For example, ever-brighter lights can actually diminish security by casting glare that impedes our vision and creates shadows where criminals can hide.

Experts say it is far more important to use light effectively than abundantly. Explaining France’s new lighting rules, Delphine Batho, until recently France’s environment minister, described the government’s desire to “change the culture” to include responsible use of light. This change is to be applauded, for what increasing numbers of studies — as well as our own eyes — tell us is that we are using far more light than we need, and at tremendous cost.

POSTED ON 19 Aug 2013 IN Business & Innovation Business & Innovation Policy & Politics Policy & Politics Pollution & Health Pollution & Health Sustainability Urbanization Asia North America North America 


Environmental Health Perspectives published a paper that recognizes "several studies over the last decade have suggested that the modern practice of keeping our bodies exposed to artificial light at night, or LAN, increases cancer risk, especially for cancers (such as breast and prostate cancers) that require hormones to grow. Women who work night shifts have shown higher rates of breast cancer, 1 whereas blind women, who are not likely to be exposed to or perceive LAN, have shown decreased risks. 2 In 2007, the International Agency for Cancer Research declared shiftwork a probable human carcinogen. 3 Now a large study of 164 countries adds another piece of evidence, implicating overall light pollution.

The study, conducted by University of Connecticut epidemiologist Richard Stevens and colleagues at the University of Haifa, showed that higher population-weighted country-level LAN levels were associated with higher incidence of breast cancer.4 A sensitivity test indicated a 30–50 percent increased risk of breast cancer in countries with the highest versus lowest LAN levels. No such association was found between LAN and incidence of non-hormone-dependent lung, colorectal, larynx, or liver cancers in women."

Also, the U.S. Green Building Council has credits in the LEED program for minimizing light pollution.

Posted by Bruce Maine on 22 Aug 2013

As of a few months ago, the outdoor lighting fixtures section at the Home Depot outlet in Idaho Falls did not offer a single shielded light fixture. Porch lights are the most "glaring" offenders effectively interrogating visitors who approach a front door at night.

Posted by Brot Coburn on 22 Aug 2013

Thank you for addressing this problem. It's strange that such a good technology as LED is used in such poorly designed structures. Where is the concern for nocturnal creatures, the night sky, and human health and well-being? Since Seattle started putting in LED streetlights a few years ago, I can hardly stand to walk or drive at night through all the glare bombs. And, the new LED headlights in cars are so bright, it actually dangerous to oncoming traffic. It seems a simple redesign of the structures would solve the problem, such as a yellowish lampshade, or a cap to focus light downward.

Posted by Denise Dahn on 22 Aug 2013

An informative article, but like many others, it compromises too much and does not strike at the core of the problem.

Think of it this way: About 70 percent of humans living on Earth can not see the magnificent Milky Way on clear, moonless nights! Can you? And millions live lives never once glimpsing more than a few stars at night! YIKES!

The only solution to light pollution? Turn off all unnecessary lights at night! Not all lights. Lights that desecrate nights. Don’t say it can’t be done. It is done every night in remote areas of Earth -- both oceanic and continental.

Indeed, hundreds of millions of people live entire lives under dark, star-soaked skies, seeing the same stars their ancient ancestors did thousands of years ago. Your ancestors survived and thrived, or you wouldn’t be here. Think about that. You are here because your ancestors survived and thrived!

Sunny Days! Starry Nights!

Stargeezer Jack

Posted by Jack Troeger on 22 Aug 2013

Excellent article.

Yes. Unwanted uncontrolled lighting is a health hazard. The irony is we put curtains in a room which has glass doors (sun facing) and light the room.

Dr. A. Jagadeesh Nellore (AP), India

Posted by Dr.A.Jagadeesh on 23 Aug 2013

Lighting at night should only be applied sparingly on a needs must basis, where needed, when needed, in right amounts and using appropriate lighting technology.

In areas where a twenty-four hour society prevails, (city centres), lighting can be left on all night. In suburban and residential areas it should be motion operated and subject to an 11p.m. curfew. In rural areas it should be banned outright unless there is a specific hazard that requires it. This includes small villages and rural motorways.

Alternative solutions to road safety issues can be addressed without naive recourse to street lighting by using reflective paints, better signage, and baffles on the central reservations of motorways. These do not consume energy and require little maintenance once installed.
The frivolous abuse of lighting should be banned outright. This includes floodlit buildings, skybeams, lasers, illuminated billboards, urban regeneration follies and crass art projects that involve illumination or injecting light into the sky.

Posted by Lincon Hashew on 28 Aug 2013

I really liked this article. Many animals vulnerable to extinction face even more troubles when humans override the nocturnal balance. Nighttime is natural, so why do humans have to interfere with it? I think it is a good idea to have at least six hours of dark time in cities around the world, like France did.

Not only is light pollution affecting vulnerable species, like bats, who eat pest organisms, having lights on when not necessary is contributing to global climate change, which affects all of us. While keeping lights on produces so much carbon dioxide, if we turn off more lights, we will save energy bills.

Unlike some other types of pollution, it seems that light pollution is “readily within our grasp to control.” However, it is hard to control light pollution when the world is urbanizing at a quick rate. Meanwhile, the biological effects are disastrous to nocturnal species that depend on darkness for survival. When species cannot adapt to light pollution, their mating, migration, feeding, and pollination patterns are disrupted. When this happens, species will become extinct, which will then affect humans because there are many species that humans depend on for medicine and crops. Even the unloved species are suffering from light pollution. We may not all love insects, but they are important in the food chain. If moths, “which pollinate the world’s flora” become extinct because they die from sources of light pollution, there will be terrible consequences in the food chain.

As for humans, “nocturnal light disrupts our sleep [and] confuses our circadian rhythms,” so I highly discourage pulling all-nighters. Too much artificial light can increase a person’s risk for “obesity, diabetes, and cardiovascular disease,” so going to sleep and turning off the lights helps the whole world become a better place.
Posted by Natasha on 14 Sep 2013

Very interesting article, but the French ordinances may be considered widely insufficient and are far from solving the problem of light pollution.

On the bright side, they have put a focus on this issue: in my work (in a French local authority) I can witness attempts and steps to reduce light pollution. But don't be naive, the reasonning of local elected officials is primarily economic. Public lighting represents 25 percent (average percentage) of French local authorities' annual energy bill (40 percent of the annual electricity bill). Plus, to obtain grants it is now mandatory to only install shielded lighting in all zones.

As for the LEDs, it is not the only kind of ligths that can be computer-controlled (it depends on the technology used by the lighting network) and it is the most efficient technology if you take a look at the lux/square meter/watt. Furthermore, the intensity can be "easily" modified.

Best regards from France.
Posted by Baptiste on 17 Sep 2013

If interested in more lighting ordinances, look up:
"Cook County & Forest Preserve Star Light Ordinance"
"Homer Glen, IL, Star Light Ordinance"

Joseph Glynn
IBEW 134

Posted by Joseph Glynn on 26 Sep 2013

In my opinion, this was a very interesting and informative article. I was shocked to learn that light pollution continues to grow at up to 20 percent! This is certainly a problem that needs to be addressed. In my own experiences, driving at night with this increase of light can actually be more dangerous than safe. The glares are awful, causing me to miss oncoming signs and traffic, which also gives me headaches. It truly is affecting individuals and our environment. I look forward to the direction this is heading. I certainly will continue to research and learn more about this fantastic topic!
Posted by Meghan Zidonis on 02 Oct 2013

People will continue to debate how much lighting to allow and under what circumstances for the foreseeable future. But whatever the outcome of that debate, there should be no excuse for property owners, cities and vehicle owners who put up cheap, glare-prone mis-aimed light fixtures that blind drivers and pedestrians with light that is doing nothing to illuminate the intended target. The stationary ones are usually mounted on low masts or buildings, and angled out so that their light goes well beyond the area that needs illumination. The ones put up by private property owners are the worst, sometimes blinding anyone within 1000 feet. Property owners should be required to aim their lighting so that no one outside of the boundaries of the property sees any direct light if only reflected light is seen, the object on the property become more visible without blinding those trying to pass by safely.
Posted by PCL on 20 Oct 2014


Comments are moderated and will be reviewed before they are posted to ensure they are on topic, relevant, and not abusive. They may be edited for length and clarity. By filling out this form, you give Yale Environment 360 permission to publish this comment.

Email address 
Please type the text shown in the graphic.

Paul Bogard is author of The End of Night: Searching for Natural Darkness in an Age of Artificial Light and editor of Let There Be Night: Testimony on Behalf of the Dark. A native Minnesotan, he is an assistant professor at James Madison University in Harrisonburg, Virginia, where he teaches creative writing and environmental literature.



In New Ozone Alert, A Warning
Of Harm to Plants and to People

Scientists are still trying to unravel the damaging effects of ground-level ozone on life on earth. But as the world warms, their concerns about the impact of this highly toxic, pollution-caused gas are growing.

Rocky Flats: A Wildlife Refuge
Confronts Its Radioactive Past

The Rocky Flats Plant outside Denver was a key U.S. nuclear facility during the Cold War. Now, following a $7 billion cleanup, the government is preparing to open a wildlife refuge on the site to the public, amid warnings from some scientists that residual plutonium may still pose serious health risks.

Pressure Mounts to Reform Our
Throwaway Clothing Culture

Americans dispose of about 12.8 million tons of textiles annually — 80 pounds for each man, woman, and child. In the U.S. and around the world, a growing number of environmentalists and clothing industry executives say it’s time to end the wasteful clothing culture and begin making new apparel out of old items on a large scale.

Sticker Shock: The Soaring Costs
Of Germany’s Nuclear Shutdown

German Chancellor Angela Merkel’s 2011 decision to rapidly phase out the country’s 17 nuclear power reactors has left the government and utilities with a massive challenge: How to clean up and store large amounts of nuclear waste and other radioactive material.

Views: Los Angeles Aims to
Revitalize a Concrete River



MORE IN Reports

Canada’s Trudeau Is Under Fire
For His Record on Green Issues

by ed struzik
After 10 years of a fossil-fuel friendly Conservative government, many Canadians welcomed the election of Justin Trudeau as prime minister. But Trudeau’s decisions to approve two oil pipelines and a major gas facility have left some questioning just how green the new leader really is.

As Chinese Luxury Market Grows,
An Upsurge in Tiger Killings in India

by sharon guynup
Poachers killed more tigers in the forests of India in 2016 than any year in the last 15. The spike is linked to demand for tiger parts in China, where the endangered animal’s bones and skins are regarded as exotic luxury items.

New Look at Rivers Reveals
The Toll of Human Activity

by jim robbins
A recent outbreak of a deadly fish parasite on the Yellowstone River may have seemed unremarkable. But a new wave of research shows the episode was likely linked to the cumulative impact of human activities that essentially weakened the Yellowstone’s "immune system."

On Slopes of Kilimanjaro, Shift
In Climate Hits Coffee Harvest

by daniel grossman
Rising temperatures and changing precipitation are taking a toll on coffee farms worldwide, including the plantations around Mount Kilimanjaro. If the world hopes to sustain its two billion cup-a-day habit, scientists say, new climate-resilient species of coffee must be developed.

Aimed at Refugees, Fences Are
Threatening European Wildlife

by jim o'donnell
A flood of migrants from the Middle East and Africa has prompted governments in the Balkans to erect hundreds of miles of border fences. Scientists say the expanding network of barriers poses a serious threat to wildlife, especially wide-ranging animals such as bears and wolves.

How Tracking Product Sources
May Help Save World’s Forests

by fred pearce
Global businesses are increasingly pledging to obtain key commodities only from sources that do not contribute to deforestation. Now, nonprofit groups are deploying data tools that help hold these companies to their promises by tracing the origins of everything from soy to timber to beef.

How Warming Is Threatening
The Genetic Diversity of Species

by jim robbins
Research on stoneflies in Glacier National Park indicates that global warming is reducing the genetic diversity of some species, compromising their ability to evolve as conditions change. These findings have major implications for how biodiversity will be affected by climate change.

Full Speed Ahead: Shipping
Plans Grow as Arctic Ice Fades

by ed struzik
Russia, China, and other nations are stepping up preparations for the day when large numbers of cargo ships will be traversing a once-icebound Arctic Ocean. But with vessels already plying these waters, experts say the time is now to prepare for the inevitable environmental fallout.

How Forensics Are Boosting
Battle Against Wildlife Trade

by heather millar
From rapid genetic analysis to spectrography, high-tech tools are being used to track down and prosecute perpetrators of the illegal wildlife trade. The new advances in forensics offer promise in stopping the trafficking in endangered species.

African Wetlands Project: A Win
For the Climate and the People?

by winifred bird
In Senegal and other developing countries, multinational companies are investing in programs to restore mangrove forests and other wetlands that sequester carbon. But critics say these initiatives should not focus on global climate goals at the expense of the local people’s livelihoods.

e360 digest
Yale Environment 360 is
a publication of the
Yale School of Forestry
& Environmental Studies


Donate to Yale Environment 360
Yale Environment 360 Newsletter



About e360
Submission Guidelines

E360 en Español

Universia partnership
Yale Environment 360 articles are now available in Spanish and Portuguese on Universia, the online educational network.
Visit the site.


e360 Digest
Video Reports


Business & Innovation
Policy & Politics
Pollution & Health
Science & Technology


Antarctica and the Arctic
Central & South America
Middle East
North America

e360 VIDEO

A look at how acidifying oceans could threaten the Dungeness crab, one of the most valuable fisheries on the U.S. West Coast.
Watch the video.


The latest
from Yale
Environment 360
is now available for mobile devices at e360.yale.edu/mobile.


An aerial view of why Europe’s per capita carbon emissions are less than 50 percent of those in the U.S.
View the photos.

e360 VIDEO

An indigenous tribe’s deadly fight to save its ancestral land in the Amazon rainforest from logging.
Learn more.

e360 VIDEO

Food waste
An e360 video series looks at the staggering amount of food wasted in the U.S. – a problem with major human and environmental costs.
Watch the video.

e360 VIDEO

Choco rainforest Cacao
Residents of the Chocó Rainforest in Ecuador are choosing to plant cacao over logging in an effort to slow deforestation.
Watch the video.

e360 VIDEO

Tribal people and ranchers join together to stop a project that would haul coal across their Montana land.
Watch the video.