ecological light pollution

The introduction of artificial light disrupts several natural light cycles that arise from the movements of the Earth, Moon, and Sun, as well as from meteorological factors.

The most obvious change in introducing light at night is the end of darkness in general. The day/night cycle, or diurnal cycle, is probably the most powerful environmental behavioral signal, as almost all animals can be categorized as nocturnal or diurnal. If a nocturnal animal is only active in extreme dark, it will be unable to survive in lit areas. The most acute affects are directly next to streetlights and lit buildings, but the diffuse light of skyglow can extend out to hundreds of kilometers away from city centres. The day/night cycle has even been shown to have an impact on blind creatures. Roughly one quarter of fully-blind individuals are in sync with the day/night cycle.{{Cite journal |last=Lamberg |first=Lynne |date=September 2006 |title=Melatonin Effective In Totally Blind People |url=https://psychiatryonline.org/doi/10.1176/pn.41.17.0026 |journal=Psychiatric News |volume=41 |issue=17 |pages=26–28 |doi=10.1176/pn.41.17.0026 |issn=0033-2704|url-access=subscription }}

The axial tilt of the Earth results in seasons outside of the tropics. The change in the length of the day, or photoperiod, is the key signal for seasonal behavior (e.g. mating season) in non-tropical animals and plants. The presence of light at night can result in "seasons out of time",{{Cite journal|url=http://informahealthcare.com/doi/abs/10.1081/CBI-200038144|doi = 10.1081/CBI-200038144|title = Seasonality and Seasons Out of Time—The Thermoregulatory Effects of Light Interference|year = 2005|last1 = Haim|first1 = Abraham|last2 = Shanas|first2 = Uri|last3 = Zubidad|first3 = Abed El Salam|last4 = Scantelbury|first4 = Michael|journal = Chronobiology International|volume = 22|issue = 1|pages = 59–66|pmid = 15865321|s2cid = 10616727|url-access = subscription}} changing the behavior, thermoregulation, and hormonal functioning of affected organisms. This may result in a disconnect between body functioning and seasonality, causing disruptions to reproduction, dormancy, and migration.

The behavior of some animals (e.g. coyotes,{{cite journal|title=Lunar Condition Influences Coyote (Canis latrans) Howling |journal=American Midland Naturalist |jstor=2426745 | volume=136 |issue=2 | pages=413–417|last1=Bender |first1=Darren J |last2=Bayne |first2=Erin M |last3=Brigham |first3=R Mark |doi=10.2307/2426745 |year=1996 }} bats,{{cite journal|jstor=2388947 | title=The Effect of Lunar Illumination on Movement and Activity of the Red Fig-eating Bat (Stenoderma rufum) | journal=Biotropica | volume=29 | issue=4 | pages=525–529| last1=Gannon | first1=Michael R | last2=Willig | first2=Michael R | year=1997 | doi=10.1111/j.1744-7429.1997.tb00048.x | bibcode=1997Biotr..29..525G | s2cid=85156702 }} toads,{{cite journal|author1=Rachel A. Granta |author2=Elizabeth A. Chadwick |author3=Tim Halliday |author3-link=Tim Halliday | title=The lunar cycle: a cue for amphibian reproductive phenology?| journal=Animal Behaviour| volume=78|year=2009|pages=349–357| doi=10.1016/j.anbehav.2009.05.007| issue=2|s2cid=53169271 }} insects) is keyed to the lunar cycle. Near city centers the level of skyglow often exceeds that of the full moon,{{cite journal |author1=C. C. M. Kyba |author2=T. Ruhtz |author3=J. Fischer |author4=F. Hölker |title = Cloud Coverage Acts as an Amplifier for Ecological Light Pollution |journal=PLOS ONE |volume=6 |year=2011 |doi = 10.1371/journal.pone.0017307 |issue=3 |pmid=21399694 |pmc=3047560|bibcode = 2011PLoSO...617307K |pages=e17307|doi-access=free }} so the presence of light at night can alter these behaviors, potentially reducing fitness. Experiments performed by biologists have also linked changes in the circadian rhythms of nocturnal animals to the presence of artificial light at night (ALAN).{{Cite web |date=2025-02-03 |title=The impact of artificial light at night on nocturnal insects: A review and synthesis - PMC |url=https://web.archive.org/web/20250203180524/https://pmc.ncbi.nlm.nih.gov/articles/PMC6262936/ |access-date=2025-03-04 |website=web.archive.org}}

File:Effect of light pollution on clouds.jpg

In pristine areas, clouds blot out the stars and darken the night sky, resulting in the darkest possible nights. In urban and suburban areas, in contrast, clouds enhance the effect of skyglow, particularly for longer wavelengths.{{cite journal|last=Kyba|first=C. C. M.|author2=Ruhtz, T. |author3=Fischer, J. |author4= Hölker, F. |title=Red is the new black: how the colour of urban skyglow varies with cloud cover|journal=Monthly Notices of the Royal Astronomical Society|date=1 September 2012|volume=425|issue=1|pages=701–708|doi=10.1111/j.1365-2966.2012.21559.x|bibcode = 2012MNRAS.425..701K |doi-access=free}} This means that the typical level of light is much higher near cities, but it also means that truly dark nights never occur in these areas.

This also means that the night sky is becoming increasingly less visible in certain areas, especially large cities. It has been noted that worldwide, the night sky is becoming 10% less visible each year.{{Cite web |last=Plait |first=Phil |date=2023-06-01 |title=Light Pollution Is Dimming Our View of the Sky, and It's Getting Worse |url=https://www.scientificamerican.com/article/light-pollution-is-dimming-our-view-of-the-sky-and-its-getting-worse/ |access-date=2025-04-30 |website=Scientific American |language=en}}

Terrestrial species are those which live entirely or predominantly on land. This includes species such as birds, insects, and land-based mammals.

File:Briare canal bridge Wasps Guêpe Light Pollution 2009 08 02.jpgs that are stealing the nocturnal insects caught in spiderwebs near street lamps demonstrate.]]

The attraction of insects to artificial light is one of the most well-known examples of the effect of light at night on organisms.{{Cite journal |last=Frank |first=Kenneth D. |date=1991 |title=Impact of Outdoor Lighting on Moths |url=https://doi.org/10.1017/s0252921100003687 |journal=International Astronomical Union Colloquium |volume=112 |pages=51 |doi=10.1017/s0252921100003687 |issn=0252-9211}} When insects are attracted to lamps they can be killed by exhaustion or contact with the lamp itself, and they are also more vulnerable to predators like bats.{{cite journal|last=Rydell|first=J|title=Exploitation of Insects around Streetlamps by Bats in Sweden|journal=Functional Ecology|year=1992|volume=6|issue=6|doi=10.2307/2389972|pages=744–750|jstor=2389972|bibcode=1992FuEco...6..744R}}

Insects are affected differently by the varying wavelengths of light, and many species can see ultraviolet and infrared light that is invisible to humans.{{Cite journal |last1=Kooi |first1=Casper J. van der |last2=Stavenga |first2=Doekele G. |last3=Arikawa |first3=Kentaro |last4=Belušič |first4=Gregor |last5=Kelber |first5=Almut |date=2021-01-07 |title=Evolution of Insect Color Vision: From Spectral Sensitivity to Visual Ecology |url=https://www.annualreviews.org/content/journals/10.1146/annurev-ento-061720-071644 |journal=Annual Review of Entomology |language=en |volume=66 |pages=435–461 |doi=10.1146/annurev-ento-061720-071644 |pmid=32966103 |issn=0066-4170}} Nocturnal insects such as moths use light as a cue to maintain a correct height when flying, by turning the upper side of their body towards the light. However, when close to artificial light sources this can cause them to continuously steer around the light - essentially trapping them.{{Cite journal |last1=Fabian |first1=Samuel T. |last2=Sondhi |first2=Yash |last3=Allen |first3=Pablo E. |last4=Theobald |first4=Jamie C. |last5=Lin |first5=Huai-Ti |date=2024-01-30 |title=Why flying insects gather at artificial light |journal=Nature Communications |language=en |volume=15 |issue=1 |pages=689 |doi=10.1038/s41467-024-44785-3 |pmid=38291028 |issn=2041-1723|pmc=10827719 |bibcode=2024NatCo..15..689F }} Due to their sensitivity to Ultraviolet light (UV), moths are more attracted to broad spectrum white and bluish light sources than they are to the yellow light emitted by low-pressure sodium lamps.{{cite news|last1=Gray|first1=R.|title=Fatal Attraction: Moths Find Modern Street Lamps Irresistible|url=https://www.telegraph.co.uk/earth/wildlife/10084659/Fatal-attraction-moths-find-modern-street-lights-irresistible.html|archive-url=https://web.archive.org/web/20130529153434/http://www.telegraph.co.uk/earth/wildlife/10084659/Fatal-attraction-moths-find-modern-street-lights-irresistible.html|url-status=dead|archive-date=May 29, 2013|access-date=15 November 2014|work=The Daily Telegraph|date=29 May 2013}}{{Cite journal |last1=Wakefield |first1=Andrew |last2=Broyles |first2=Moth |last3=Stone |first3=Emma L. |last4=Harris |first4=Stephen |last5=Jones |first5=Gareth |date=2018 |title=Quantifying the attractiveness of broad-spectrum street lights to aerial nocturnal insects |url=https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2664.13004 |journal=Journal of Applied Ecology |language=en |volume=55 |issue=2 |pages=714–722 |doi=10.1111/1365-2664.13004 |bibcode=2018JApEc..55..714W |issn=1365-2664}}

File:EcologicalTrapPiège écologiqueAout2010Lille.JPG

Dragonflies perceive horizontally polarized light as a sign of water.{{Cite journal |last1=Horváth |first1=Gábor |last2=Bernáth |first2=Balázs |last3=Molnár |first3=Gergely |date=1998-06-01 |title=Dragonflies Find Crude Oil Visually More Attractive than Water: Multiple-Choice Experiments on Dragonfly Polarotaxis |url=https://link.springer.com/article/10.1007/s001140050503 |journal=Naturwissenschaften |language=en |volume=85 |issue=6 |pages=292–297 |doi=10.1007/s001140050503 |bibcode=1998NW.....85..292H |issn=1432-1904|url-access=subscription }} For this reason, sources of water are indistinguishable from asphalt roads with polarized light pollution to them. Dragonflies searching for water either to drink or in which to lay eggs often land on roads or other dark flat reflective surfaces such as cars and remain there until they die of dehydration and hyperthermia.{{cite news|title=Polarized Light Pollution Leads Animals Astray|work=UPI Space Daily|publisher=United Press International|date=13 January 2009}}

Light pollution may hamper the mating rituals of fireflies, as they depend on their own light for courtship, resulting in decreased populations.{{cite news|first=Alan|last=Blinder|url=https://www.nytimes.com/2014/08/15/us/firefly-population-science-in-a-twinkle-of-nighttime-in-the-south.html?_r=3|title=The Science in a Twinkle of Nighttime in the South|work=The New York Times|date=August 14, 2014|access-date=August 18, 2014}}{{Cite journal|last1=Owens|first1=Avalon Celeste Stevahn|last2=Meyer-Rochow|first2=Victor Benno|last3=Yang|first3=En-Cheng|date=2018-02-07|title=Short- and mid-wavelength artificial light influences the flash signals of Aquatica ficta fireflies (Coleoptera: Lampyridae)|journal=PLOS ONE|language=en|volume=13|issue=2|pages=e0191576|doi=10.1371/journal.pone.0191576|pmid=29415023|pmc=5802884|issn=1932-6203|bibcode=2018PLoSO..1391576O|doi-access=free}}{{Cite journal|last1=Firebaugh|first1=Ariel|last2=Haynes|first2=Kyle J.|date=2016-12-01|title=Experimental tests of light-pollution impacts on nocturnal insect courtship and dispersal|journal=Oecologia|language=en|volume=182|issue=4|pages=1203–1211|doi=10.1007/s00442-016-3723-1|pmid=27646716|issn=0029-8549|bibcode=2016Oecol.182.1203F|s2cid=36670391}} Fireflies are charismatic and are easily spotted by nonexperts.{{Cite journal |last1=Zieger |first1=Michael |last2=Springer |first2=Steffen |date=2021 |title=Can Google Trends data confirm the need for charismatic species to generate interest in conservation? |url=https://doi.org/10.1071/pc20090 |journal=Pacific Conservation Biology |volume=27 |issue=3 |pages=296 |doi=10.1071/pc20090 |bibcode=2021PacSB..27..296Z |issn=1038-2097|url-access=subscription }} Their rapid response to environmental changes, makes them good bioindicators for the problems caused by artificial light at night.{{Cite journal|last1=Viviani|first1=Vadim Ravara|last2=Rocha|first2=Mayra Yamazaki|last3=Hagen|first3=Oskar|date=June 2010|title=Bioluminescent beetles (Coleoptera: Elateroidea: Lampyridae, Phengodidae, Elateridae) in the municipalities of Campinas, Sorocaba-Votorantim and Rio Claro-Limeira (SP, Brazil): biodiversity and influence of urban sprawl|journal=Biota Neotropica|volume=10|issue=2|pages=103–116|doi=10.1590/S1676-06032010000200013|issn=1676-0603|doi-access=free}}

Artificial light at night has been sugested as an important factor in the global decline of amphibian populations.{{cite book |last=Wise |first=Sharon |author-link= |url= |title="Studying the ecological impacts of light pollution on wildlife: amphibians as models." from "Starlight: A Common Heritage" |date=2007 |publisher=Cipriano, M., Jafar, J. |isbn= |location= |pages=209–218}} Many species are nocturnally active, and their biological rhythms could be affected by a change in their natural light-dark cycle. ALAN has also been linked to decreased growth and metamorphic duration.{{Cite journal |last1=Dananay |first1=Kacey L. |last2=Benard |first2=Michael F. |date=2018-07-04 |title=Artificial light at night decreases metamorphic duration and juvenile growth in a widespread amphibian |journal=Proceedings. Biological Sciences |volume=285 |issue=1882 |pages=20180367 |doi=10.1098/rspb.2018.0367 |issn=1471-2954 |pmc=6053935 |pmid=30051829}} It can also alter the amount or timing of feeding, sexual behaviour and fertilization success,{{Cite journal |last1=Touzot |first1=Morgane |last2=Lengagne |first2=Thierry |last3=Secondi |first3=Jean |last4=Desouhant |first4=Emmanuel |last5=Théry |first5=Marc |last6=Dumet |first6=Adeline |last7=Duchamp |first7=Claude |last8=Mondy |first8=Nathalie |date=2020 |title=Artificial light at night alters the sexual behaviour and fertilisation success of the common toad |journal=Environmental Pollution |volume=259 |pages=113883 |issn=0269-7491 |doi=10.1016/j.envpol.2019.113883 |pmid=31931411 |bibcode=2020EPoll.25913883T |url=https://doi.org/10.1016/j.envpol.2019.113883}} behaviour (such as improper orientation), and anti-predator behaviours.{{Cite journal |last1=Dananay |first1=KL |last2=Krynak |first2=KL |last3=Krynak |first3=TJ |last4=Benard |first4=MF |date=2015 |title=Legacy of road salt: apparent positive larval effects counteracted by negative post-metamorphic effects in wood frogs |journal=Environmental Toxicology and Chemistry |volume=34 |issue=10 |pages=2417–2424 |doi=10.1002/etc.3082 |pmid=26033303 |bibcode=2015EnvTC..34.2417D |url=http://doi.org/10.1002/etc.3082|url-access=subscription }}

Since most bats (Chiroptera) are nocturnal, they are severely affected by artificial light at night. These effects are highly species- and context specific. Effects range from disruption of migration{{Cite journal |last1=Voigt |first1=Christian C. |last2=Rehnig |first2=Katharina |last3=Lindecke |first3=Oliver |last4=Pētersons |first4=Gunārs |date=2018 |title=Migratory bats are attracted by red light but not by warm-white light: Implications for the protection of nocturnal migrants |journal=Ecology and Evolution |language=en |volume=8 |issue=18 |pages=9353–9361 |doi=10.1002/ece3.4400 |issn=2045-7758 |pmc=6194273 |pmid=30377506|bibcode=2018EcoEv...8.9353V }} and travel to hunting sites,{{Cite journal |last1=Hale |first1=James D. |last2=Fairbrass |first2=Alison J. |last3=Matthews |first3=Thomas J. |last4=Davies |first4=Gemma |last5=Sadler |first5=Jon P. |date=July 2015 |title=The ecological impact of city lighting scenarios: exploring gap crossing thresholds for urban bats |journal=Global Change Biology |language=en |volume=21 |issue=7 |pages=2467–2478 |doi=10.1111/gcb.12884 |issn=1354-1013 |pmc=4975606 |pmid=25644403|bibcode=2015GCBio..21.2467H }}{{Cite journal |last1=Stone |first1=Emma Louise |last2=Jones |first2=Gareth |last3=Harris |first3=Stephen |date=July 2009 |title=Street Lighting Disturbs Commuting Bats |url=https://linkinghub.elsevier.com/retrieve/pii/S0960982209011932 |journal=Current Biology |language=en |volume=19 |issue=13 |pages=1123–1127 |doi=10.1016/j.cub.2009.05.058|bibcode=2009CBio...19.1123S }} finding and accessing roosts,{{Cite journal |last1=Rydell |first1=Jens |last2=Michaelsen |first2=Tore Christian |last3=Sanchez-Navarro |first3=Sonia |last4=Eklöf |first4=Johan |date=December 2021 |title=How to leave the church: light avoidance by brown long-eared bats |url=https://link.springer.com/10.1007/s42991-021-00154-x |journal=Mammalian Biology |language=en |volume=101 |issue=6 |pages=979–986 |doi=10.1007/s42991-021-00154-x |issn=1616-5047|url-access=subscription }}{{Cite journal |last1=Boldogh |first1=Sándor |last2=Dobrosi |first2=Dénes |last3=Samu |first3=Péter |date=December 2007 |title=The effects of the illumination of buildings on house-dwelling bats and its conservation consequences |url=http://www.bioone.org/doi/abs/10.3161/1733-5329%282007%299%5B527%3ATEOTIO%5D2.0.CO%3B2 |journal=Acta Chiropterologica |language=en |volume=9 |issue=2 |pages=527–534 |doi=10.3161/1733-5329(2007)9[527:TEOTIO]2.0.CO;2 |issn=1508-1109|url-access=subscription }} and foraging behaviour.{{Cite journal |last1=Spoelstra |first1=Kamiel |last2=van Grunsven |first2=Roy H. A. |last3=Ramakers |first3=Jip J. C. |last4=Ferguson |first4=Kim B. |last5=Raap |first5=Thomas |last6=Donners |first6=Maurice |last7=Veenendaal |first7=Elmar M. |last8=Visser |first8=Marcel E. |date=2017-05-31 |title=Response of bats to light with different spectra: light-shy and agile bat presence is affected by white and green, but not red light |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=284 |issue=1855 |pages=20170075 |doi=10.1098/rspb.2017.0075 |issn=0962-8452 |pmc=5454258 |pmid=28566484}}{{Cite journal |last1=Hermans |first1=Claire |last2=Litovska |first2=Iryna |last3=de Pastors |first3=Mélyssa |last4=Visser |first4=Marcel E. |last5=Spoelstra |first5=Kamiel |date=August 2024 |title=Artificial light at night drives diel activity patterns of synanthropic pipistrelle bats and their prey |journal=Science of the Total Environment |language=en |volume=940 |pages=173699 |doi=10.1016/j.scitotenv.2024.173699|doi-access=free |bibcode=2024ScTEn.94073699H }}

{{see also|Bird-skyscraper collisions}}

Birds migrate during the night for several reasons. It is also cooler at night which means birds are able to fly and become dehydrated slower. With city lights outshining the night sky, birds have more difficulty navigating by stars.{{cite web|date=2020-10-15|title=در سایه‌ی نور‌ها|url=https://parisabajelan.com/brazil-birds-and-light-pollution/|access-date=2020-10-16|website=پریسا باجلان|language=fa-IR|archive-date=2021-04-10|archive-url=https://web.archive.org/web/20210410195730/https://parisabajelan.com/brazil-birds-and-light-pollution/|url-status=dead}}

Lights on tall structures can disorient migrating birds leading to fatalities. An estimated 365-988 million fatal bird collisions with buildings occur annually in North America, making human-made structures a large contributor to the decline in population of bird species.{{Cite journal|last1=Loss|first1=Scott R.|last2=Will|first2=Tom|last3=Loss|first3=Sara S.|last4=Marra|first4=Peter P.|date=2014-02-01|title=Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability|journal=The Condor|language=en|volume=116|issue=1|pages=8–23|doi=10.1650/CONDOR-13-090.1|s2cid=11925316|issn=0010-5422|doi-access=free}} The surface area of the glass emitting the artificial light at night is a major factor for fatal bird collisions with buildings, and turning off lights at night can minimize these fatalities.{{Cite journal|last1=Lao|first1=Sirena|last2=Robertson|first2=Bruce A.|last3=Anderson|first3=Abigail W.|last4=Blair|first4=Robert B.|last5=Eckles|first5=Joanna W.|last6=Turner|first6=Reed J.|last7=Loss|first7=Scott R.|date=January 2020|title=The influence of artificial light at night and polarized light on bird-building collisions|url=http://dx.doi.org/10.1016/j.biocon.2019.108358|journal=Biological Conservation|volume=241|page=108358|doi=10.1016/j.biocon.2019.108358|bibcode=2020BCons.24108358L |s2cid=213571293|issn=0006-3207|url-access=subscription}} The Fatal Light Awareness Program (FLAP) works with building owners in Toronto, Canada and other cities to reduce mortality of birds by turning out lights during migration periods.

File:CanonLumièreNY5294681087 1b4c59ec28 b.jpg.]]

Similar disorientation has also been noted for bird species migrating close to offshore production and drilling facilities. Studies carried out by Nederlandse Aardolie Maatschappij b.v. (NAM) and Shell have led to development and trial of new lighting technologies in the North Sea. In early 2007, the lights were installed on the Shell production platform L15. The experiment proved a great success since the number of birds circling the platform declined by 50–90%.[56] Juvenile seabirds may also be disoriented by lights as they leave their nests and fly out to sea causing events of high mortality.{{cite journal|last1=RodrÍguez|first1=Airam|last2=RodrÍguez|first2=Beneharo|title=Attraction of petrels to artificial lights in the Canary Islands: effects of the moon phase and age class|journal=Ibis|volume=151|pages=299–310|year=2009|doi=10.1111/j.1474-919X.2009.00925.x|issue=2|hdl=10261/45133|hdl-access=free}} To minimise mortality rescue programs are conducted on many islands giving a second chance to thousands of seabird fledglings.{{cite journal |last1=Rodríguez |first1=Airam |last2=Holmes |first2=Nick D. |last3=Ryan |first3=Peter G. |last4=Wilson |first4=Kerry-Jayne |last5=Faulquier |first5=Lucie |last6=Murillo |first6=Yovana |last7=Raine |first7=André F. |last8=Penniman |first8=Jay F. |last9=Neves |first9=Verónica |last10=Rodríguez |first10=Beneharo |last11=Negro |first11=Juan J. |last12=Chiaradia |first12=André |last13=Dann |first13=Peter |last14=Anderson |first14=Tracy |last15=Metzger |first15=Benjamin |last16=Shirai |first16=Masaki |last17=Deppe |first17=Lorna |last18=Wheeler |first18=Jennifer |last19=Hodum |first19=Peter |last20=Gouveia |first20=Catia |last21=Carmo |first21=Vanda |last22=Carreira |first22=Gilberto P. |last23=Delgado-Alburqueque |first23=Luis |last24=Guerra-Correa |first24=Carlos |last25=Couzi |first25=François-Xavier |last26=Travers |first26=Marc |last27=Corre |first27=Matthieu Le |title=Seabird mortality induced by land-based artificial lights: Seabird Mortality and Artificial Lights |journal=Conservation Biology |date=October 2017 |volume=31 |issue=5 |pages=986–1001 |doi=10.1111/cobi.12900|pmid=28151557 |hdl=10400.3/4515 |hdl-access=free }}

File:Brazil star trails and birds in light pollution photography in Rio beach at night.jpg

File:Birds flying trace.jpg

Ceilometers (searchlights) can be particularly deadly traps for birds,{{Cite web |url=http://www.staplenews.com/home/2010/9/16/10000-birds-trapped-in-the-world-trade-center-light-beams.html |title=10000 birds trapped in the World Center light beams |access-date=2011-08-25 |archive-date=2017-11-16 |archive-url=https://web.archive.org/web/20171116134023/http://www.staplenews.com/home/2010/9/16/10000-birds-trapped-in-the-world-trade-center-light-beams.html |url-status=dead }} because they can become caught in the beams and be at risk of exhaustion and collisions with other birds. In the worst recorded ceilometer kill-off, on October 7–8, 1954, 50,000 birds from 53 different species were killed at Warner Robins Air Force Base.{{cite journal|last=Johnston|first=D|author2=Haines|title=Analysis of Mass Bird Mortality in October, 1954|journal=The Auk|volume=74|issue=4|pages=447–458|year=1957|doi=10.2307/4081744|jstor=4081744|doi-access=free}}

As a result of light pollution, birds have been shown to experience sexual maturation earlier and forage more aggressively than previously identified.{{Cite journal |last1=Davies |first1=Thomas W |last2=Duffy |first2=James P |last3=Bennie |first3=Jon |last4=Gaston |first4=Kevin J |date=2014 |title=The nature, extent, and ecological implications of marine light pollution |url=https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/130281 |journal=Frontiers in Ecology and the Environment |language=en |volume=12 |issue=6 |pages=347–355 |doi=10.1890/130281 |bibcode=2014FrEE...12..347D |issn=1540-9309|url-access=subscription }}

Lights from seashore developments repel nesting sea turtle mothers. The turtle hatchlings should instinctively find their way toward the sea by using the light of the moon, but are often fatally attracted to landward lights such as street and hotel lights instead.{{Cite web |last=Salmon |first=Michael |date=2003 |title=Artificial night lighting and sea turtles |url=https://www.researchgate.net/publication/283857765 |website=ResearchGate}}{{Cite web |title=Artificial Lighting |url=https://myfwc.com/research/wildlife/sea-turtles/threats/artificial-lighting/#:~:text=Hatchlings%20that%20crawl%20toward%20artificial,what%20often%20leads%20hatchlings%20astray. |access-date=2025-02-13 |website=Florida Fish And Wildlife Conservation Commission |language=en}}

File:Ibira at night.jpg (Ibirapuera Park, Brazil) at night]]

Artificial lighting has many negative impacts on trees and plants, particularly in fall and autumn. Trees and herbaceous plants rely on the photoperiod, or the amount of time in a day where sunlight is available for photosynthesis, to help determine the changing seasons. When hours of sunlight decrease, plants can recognize that autumn is underway and begin to make preparations for winter dormancy. Deciduous trees shift the colour of their leaves to maximize different wavelengths of light that are more prevalent in the fall, before eventually dropping them as light becomes too scarce for photosynthesis to be worthwhile. When deciduous trees are exposed to light pollution, they mistake the artificial light for sunlight and retain their green leaves later into the autumn season. This can be dangerous for those trees, as the energy they waste trying to photosynthesize should be preserved for winter survival. Light pollution can also cause leaf stoma to remain open into the night, which leaves the tree vulnerable to infection and disease.{{Cite journal |last1=Škvareninová |first1=Jana |last2=Tuhárska |first2=Mária |last3=Škvarenina |first3=Jaroslav |last4=Babálová |first4=Darina |last5=Slobodníková |first5=Lenka |last6=Slobodník |first6=Branko |last7=Středová |first7=Hana |last8=Minďaš |first8=Jozef |date=2017-12-01 |title=Effects of light pollution on tree phenology in the urban environment |journal=Moravian Geographical Reports |language=en |volume=25 |issue=4 |pages=282–290 |doi=10.1515/mgr-2017-0024|s2cid=73529155 |doi-access=free |bibcode=2017MorGR..25..282S }}

Similarly, light pollution in the spring can also be dangerous for trees and herbaceous plants. Artificial light can cause plants begin producing leaves for photosynthesizing at a time in the season when temperatures may not yet be warm enough to support the new leaf buds. Small herbaceous plants that are exposed to artificial lighting potentially face a greater risk, as more of their body is illuminated. Therefore, only the root system is protected, and could potentially not be enough to sustain the whole plant as it tries to remain green through the fall and winter.{{Cite journal |last1=ffrench-Constant |first1=Richard H. |last2=Somers-Yeates |first2=Robin |last3=Bennie |first3=Jonathan |last4=Economou |first4=Theodoros |last5=Hodgson |first5=David |last6=Spalding |first6=Adrian |last7=McGregor |first7=Peter K. |date=2016-06-29 |title=Light pollution is associated with earlier tree budburst across the United Kingdom |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=283 |issue=1833 |page=20160813 |doi=10.1098/rspb.2016.0813 |issn=0962-8452 |pmc=4936040 |pmid=27358370}} Light pollution can also cause certain trees to begin budding earlier than they normally would.{{Cite journal |last1=ffrench-Constant |first1=Richard H. |last2=Somers-Yeates |first2=Robin |last3=Bennie |first3=Jonathan |last4=Economou |first4=Theodoros |last5=Hodgson |first5=David |last6=Spalding |first6=Adrian |last7=McGregor |first7=Peter K. |date=2016-06-29 |title=Light pollution is associated with earlier tree budburst across the United Kingdom |journal=Proceedings of the Royal Society B: Biological Sciences |volume=283 |issue=1833 |pages=20160813 |doi=10.1098/rspb.2016.0813 |pmc=4936040 |pmid=27358370}}

Aquatic animals are animals that live in the water. Animals like these include fish, dolphins, turtles, and many more. Ecological light pollution can also have critical effects on marine ecosystems.{{cite journal |last1=Marangoni |first1=Laura F. B. |last2=Davies |first2=Thomas |last3=Smyth |first3=Tim |last4=Rodríguez |first4=Airam |last5=Hamann |first5=Mark |last6=Duarte |first6=Cristian |last7=Pendoley |first7=Kellie |last8=Berge |first8=Jørgen |last9=Maggi |first9=Elena |last10=Levy |first10=Oren |title=Impacts of artificial light at night in marine ecosystems—A review |journal=Global Change Biology |date=September 2022 |volume=28 |issue=18 |pages=5346–5367 |doi=10.1111/gcb.16264|pmid=35583661 |pmc=9540822 |bibcode=2022GCBio..28.5346M |hdl=11568/1165839 |hdl-access=free }} As of 2010, roughly 22% of the worlds coastline were exposed to nightly artificial light pollution.{{Cite journal |last1=Davies |first1=Thomas W |last2=Duffy |first2=James P |last3=Bennie |first3=Jon |last4=Gaston |first4=Kevin J |date=2014 |title=The nature, extent, and ecological implications of marine light pollution |url=https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/130281 |journal=Frontiers in Ecology and the Environment |language=en |volume=12 |issue=6 |pages=347–355 |doi=10.1890/130281 |bibcode=2014FrEE...12..347D |issn=1540-9309|url-access=subscription }}

Zooplankton (e.g. Daphnia) exhibit diurnal vertical migration. That is, they actively change their vertical position inside of lakes throughout the day. In lakes with fish, the primary driver for their migration is light level, because small fish visually prey on them. The introduction of light through skyglow reduces the height to which they can ascend during the night.{{cite journal |author1=Marianne V. Moore |author2=Stephanie M. Pierce |author3=Hannah M. Walsh |author4=Siri K. Kvalvik |author5=Julie D. Lim |url=http://www.wellesley.edu/Biology/Faculty/Mmoore/Content/Moore_2000.pdf |title=Urban light pollution alters the diel vertical migration of Daphnia |journal=Verh. Internat. Verein. Limnol. |volume=27 |year=2000 |issue=2 |pages=1–4 |doi=10.1080/03680770.1998.11901341 |bibcode=2000SILP...27..779M |access-date=2011-08-19 |archive-date=2005-10-21 |archive-url=https://web.archive.org/web/20051021232549/http://www.wellesley.edu/Biology/Faculty/Mmoore/Content/Moore_2000.pdf |url-status=dead }} Because zooplankton feed on the phytoplankton that form algae, the decrease in their predation upon phytoplankton may increase the chance of algal blooms, which can kill off the lakes' plants and lower water quality.

Light pollution impacts migration in some species of fish. For example, juvenile chinook salmon are attracted to and slowed down by artificial light. It is possible that artificial light draws them closer to the shoreline, where they face a greater risk of predation from birds and mammals. Artificial lighting also attracts a greater density of piscivorous fish, which have an advantage due to the slower movement of the juvenile fish.{{Cite journal |last1=Nelson |first1=Thomas Reid |last2=Michel |first2=Cyril J. |last3=Gary |first3=Meagan P. |last4=Lehman |first4=Brendan M. |last5=Demetras |first5=Nicholas J. |last6=Hammen |first6=Jeremy J. |last7=Horn |first7=Michael J. |date=2021-02-16 |title=Effects of Artificial Lighting at Night on Predator Density and Salmonid Predation |journal=Transactions of the American Fisheries Society |volume=150 |issue=2 |pages=147–159 |doi=10.1002/tafs.10286 |s2cid=229392819 |issn=0002-8487|doi-access=free |bibcode=2021TrAFS.150..147N }} Light pollution also has impacts on the hormonal functioning of some fish; European perch and roach both experience reductions in the production of reproductive hormones when exposed to artificial lighting in a rural environment.{{Cite journal |last1=Brüning |first1=Anika |last2=Kloas |first2=Werner |last3=Preuer |first3=Torsten |last4=Hölker |first4=Franz |date=2018 |title=Influence of artificially induced light pollution on the hormone system of two common fish species, perch and roach, in a rural habitat |journal=Conservation Physiology |volume=6 |issue=1 |pages=coy016 |doi=10.1093/conphys/coy016 |issn=2051-1434 |pmc=5905364 |pmid=29686874}} Artificial light has also been shown to cause disruptions to fish (and zooplankton) in the high Arctic, where fishing boats with lights resulted in a lack of fish up to 200 metres below the water's surface.{{Cite journal |last1=Berge |first1=Jørgen |last2=Geoffroy |first2=Maxime |last3=Daase |first3=Malin |last4=Cottier |first4=Finlo |last5=Priou |first5=Pierre |last6=Cohen |first6=Jonathan H. |last7=Johnsen |first7=Geir |last8=McKee |first8=David |last9=Kostakis |first9=Ina |last10=Renaud |first10=Paul E. |last11=Vogedes |first11=Daniel |date=2020-03-05 |title=Artificial light during the polar night disrupts Arctic fish and zooplankton behaviour down to 200 m depth |journal=Communications Biology |language=en |volume=3 |issue=1 |page=102 |doi=10.1038/s42003-020-0807-6 |pmid=32139805 |pmc=7058619 |issn=2399-3642}}

At the turn of the century it was discovered that human eyes contain a non-imaging photosensor that is the primary regulator of the human circadian rhythm.{{cite journal |last1=Provencio |first1=Ignacio |last2=Rodriguez |first2=Ignacio R. |last3=Jiang |first3=Guisen |last4=Hayes |first4=William Pär |last5=Moreira |first5=Ernesto F. |last6=Rollag |first6=Mark D. |year=2000 |title=A Novel Human Opsin in the Inner Retina |journal=The Journal of Neuroscience |volume=20 |issue=2 |pages=600–605 |doi=10.1523/JNEUROSCI.20-02-00600.2000 |pmc=6772411 |pmid=10632589}} This photosensor is particularly affected by blue light, and when it observes light the pineal gland stops the secretion of melatonin. The presence of light at night in human dwellings (or for shift workers) makes going to sleep more difficult and reduces the overall level of melatonin in the bloodstream, and exposure to a low-level incandescent bulb for 39 minutes is sufficient to suppress melatonin levels to 50%.{{cite journal |last1=Schulmeister |first1=K. |last2=Weber |first2=M. |last3=Bogner |first3=W. |last4=Schernhammer |first4=E. |year=2002 |title=Application of melatonin action spectra on practical lighting issues |url=http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001009370 |url-status=dead |journal=Final Report. The Fifth International LRO Lighting Research Symposium, Light and Human Health |archive-url=https://web.archive.org/web/20160818092349/http://www.epri.com/abstracts/Pages/ProductAbstract.aspx?ProductId=000000000001009370 |archive-date=2016-08-18 |access-date=2016-08-01}} Because melatonin is a powerful anti-oxidant, it is hypothesized that this reduction can result in an increased risk of breast and prostate cancer.{{cite journal |author1=Scott Davis |author2=Dana K. Mirick |author3=Richard G. Stevens |year=2001 |title=Night Shift Work, Light at Night, and Risk of Breast Cancer |journal=Journal of the National Cancer Institute |volume=93 |issue=20 |pages=1557–1562 |doi=10.1093/jnci/93.20.1557 |pmid=11604479 |doi-access=free}}{{cite journal |author1=Eva S. Schernhammer |author2=Francine Laden |author3=Frank E. Speizer |author4=Walter C. Willett |author5=David J. Hunter |author6=Ichiro Kawachi |author7=Graham A. Colditz |year=2001 |title=Rotating Night Shifts and Risk of Breast Cancer in Women Participating in the Nurses' Health Study |journal=Journal of the National Cancer Institute |volume=93 |issue=20 |pages=1563–1568 |doi=10.1093/jnci/93.20.1563 |pmid=11604480 |doi-access=free}} A suppression of melatonin has also been linked to obesity, diabetes, and depression.{{Cite journal |last=Jiménez |first=Daniel |last2=Neira Arenas |first2=Laura |last3=Hernández Rincón |first3=Erwin Hernando |last4=García Céspedes |first4=María José |last5=Jaimes Peñuela |first5=Claudia Liliana |date=2025-06-01 |title=Luminous threats: The health impacts of artificial nighttime light on metabolic and mental health: A scoping review |url=https://www.sciencedirect.com/science/article/pii/S2666558125000260?via=ihub |journal=Wellbeing, Space and Society |volume=8 |pages=100260 |doi=10.1016/j.wss.2025.100260 |issn=2666-5581|url-access=subscription }}

One of the biggest ways humans receive artificial light at night is through technology such as phones, computers, and televisions. For computers and phones in particular, the light emitted is so close in proximity to the human eye that it has a profound impact on the human body and circadian rhythm.{{Cite web |date=2024-10-15 |title=Digital Devices and Your Eyes |url=https://www.aao.org/eye-health/tips-prevention/digital-devices-your-eyes#:~:text=Computer%20and%20digital%20eye%20strain,headache |access-date=2025-04-30 |website=American Academy of Ophthalmology |language=en}} These forms of technology also emit a significant amount of blue light which impacts the non-imaging photosensor in the human eye which regulates the circadian rhythm.

Other human health effects may include increased headache incidence, worker fatigue, medically defined stress, decrease in sexual function and increase in anxiety.Susan L. Burks, Managing your Migraine, Humana Press, New Jersey (1994) {{ISBN|0-89603-277-9}}Cambridge Handbook of Psychology, Health and Medicine, edited by Andrew Baum, Robert West, John Weinman, Stanton Newman, Chris McManus, Cambridge University Press (1997) {{ISBN|0-521-43686-9}}L. Pijnenburg, M. Camps and G. Jongmans-Liedekerken, Looking closer at assimilation lighting, Venlo, GGD, Noord-Limburg (1991){{cite journal |last1=Knez |first1=I |year=2001 |title=Effects of Colour of Light on Nonvisual Psychological Processes |journal=Journal of Environmental Psychology |volume=21 |issue=2 |pages=201–208 |doi=10.1006/jevp.2000.0198}} In places with high levels of nighttime light, such as cities, mood disorders and anxiety have been linked to artificial light at night.{{Cite journal |last=Helbich |first=Marco |last2=Burov |first2=Angel |last3=Dimitrova |first3=Donka |last4=Markevych |first4=Iana |last5=Nieuwenhuijsen |first5=Mark J. |last6=Dzhambov |first6=Angel M. |date=2024-12-15 |title=Sleep problems mediate the association between outdoor nighttime light and symptoms of depression and anxiety: A cross-sectional, multi-city study in Bulgaria |url=https://www.sciencedirect.com/science/article/pii/S0013935124018024#:~:text=Exposure%20to%20excessive%20nighttime%20light,be%20associated%20with%20mood%20regulation. |journal=Environmental Research |volume=263 |pages=119897 |doi=10.1016/j.envres.2024.119897 |issn=0013-9351|hdl=10230/68848 |hdl-access=free }} Likewise, animal models have been studied demonstrating unavoidable light to produce adverse effect on mood and anxiety.{{Cite journal |last1=Fonken |first1=L K |last2=Finy |first2=M S |last3=Walton |first3=James C. |last4=Weil |first4=Zachary M. |last5=Workman |first5=Joanna L. |last6=Ross |first6=Jessica |last7=Nelson |first7=Randy J. |date=28 December 2009 |title=Influence of light at night on murine anxiety- and depressive-like responses |journal=Behavioural Brain Research |volume=205 |issue=2 |pages=349–354 |doi=10.1016/j.bbr.2009.07.001 |pmid=19591880 |s2cid=4204514}}{{cite journal |last1=Longcore |first1=Travis |last2=Rodríguez |first2=Airam |last3=Witherington |first3=Blair |last4=Penniman |first4=Jay F. |last5=Herf |first5=Lorna |last6=Herf |first6=Michael |title=Rapid assessment of lamp spectrum to quantify ecological effects of light at night |journal=Journal of Experimental Zoology Part A: Ecological and Integrative Physiology |date=October 2018 |volume=329 |issue=8–9 |pages=511–521 |doi=10.1002/jez.2184|doi-access=free |pmid=29894022 |bibcode=2018JEZA..329..511L |hdl=10261/177341 |hdl-access=free }}

The effect that artificial light has upon organisms is wavelength dependent. While human beings cannot see ultraviolet light, it is often used by entomologists to attract insects. Generally speaking, blue light is more likely to be damaging to mammals because the non-imaging photoreceptors in mammalian eyes are most sensitive in the blue region.{{cite journal|last=Falchi|first=F|author2=Cinzano P |author3=Elvidge CD |author4=Keith DM |author5=Haim A |journal=Journal of Environmental Management|title=Limiting the impact of light pollution on human health, environment and stellar visibility |year=2011|volume=92|doi=10.1016/j.jenvman.2011.06.029 |pmid=21745709|issue=10 |pages=2714–2722|arxiv=2007.02063|bibcode=2011JEnvM..92.2714F|s2cid=18988450}}{{cite journal |last1=Falchi |first1=F. |last2=Cinzano |first2=P. |date=2011 |title=Limiting the impact of light pollution on human health, environment, and stellar visibility |url=https://doi.org/10.1016/j.jenvman.2011.05.017 |journal=Journal of Environmental Management |volume=92 |issue=11 |pages=2714–2722 |doi=10.1016/j.jenvman.2011.05.017 |pmid=21684061 |access-date= 2024-12-10|url-access=subscription }}

Exposure to blue light in humans, especially at night, has been associated with decreased melatonin, leading to sleep disorders and stress.{{cite journal |last1=Leonid |first1=K. |last2=Casper |first2=R.F. |last3=Hawa |first3=R.J. |last4=Perelman |first4=P. |last5=Chung |first5=S.H. |last6=Sokalsky |first6=S. |last7=Shapiro |first7=C.M. |date=2005 |title=Blocking low-wavelength light prevents nocturnal melatonin suppression with no adverse effect on performance during simulated shift work |journal=J. Clin. Endocrin. Metabol. |volume=90 |issue=5 |pages=2755–2761|doi=10.1210/jc.2004-2062 }}

In the environment, Rayleigh scattering contributes to the brightness of the night sky. This implies that shorter wavelength waves, such as blue light, are scattered more than those with longer wavelengths (red and green light).{{cite book |last1=Benenson |first1=W. |last2=Harris |first2=W.J. |last3=Stocker |first3=H. |last4=Lutz |first4=H. |date=2002 |title=Handbook of Physics |publisher=Springer-Verlag |isbn=0-387-95269-1 |pages=376}}

This means that if traditional vapour discharge streetlamps are replaced by white LEDs (which generally emit more of their radiation in the blue part of the spectrum), the ecological impact could be greater even if the total amount of radiated light is decreased.{{cite journal|last=International Dark-Sky Association|title=Visibility, Environmental, and Astronomical Issues Associated with Blue-Rich White Outdoor Lighting|journal=IDA White Paper|year=2010|url=http://docs.darksky.org/Reports/IDA-Blue-Rich-Light-White-Paper.pdf|access-date=2011-08-20|archive-url=https://web.archive.org/web/20110814204407/http://docs.darksky.org/Reports/IDA-Blue-Rich-Light-White-Paper.pdf|archive-date=2011-08-14|url-status=dead}}

File:Effect of light pollution on sky polarization.jpg is mostly unpolarized, and its addition to moonlight results in a decreased polarization signal.]]

Artificial planar surfaces, such as glass windows or asphalt reflect highly polarized light. Polarized light pollution is caused by our choice of technology and materials and can be reduced by more thoughtfully selecting materials for construction.{{Cite journal |last1=Horváth |first1=Gábor |last2=Kriska |first2=György |last3=Malik |first3=Péter |last4=Robertson |first4=Bruce |date=2009 |title=Polarized light pollution: a new kind of ecological photopollution |url=https://esajournals.onlinelibrary.wiley.com/doi/10.1890/080129 |journal=Frontiers in Ecology and the Environment |language=en |volume=7 |issue=6 |pages=317–325 |doi=10.1890/080129 |bibcode=2009FrEE....7..317H |issn=1540-9309}} One notable example of polarized light is the light that is reflected by the glass of a watch. Many insects are attracted to polarized surfaces, because polarization is usually an indicator for water. This effect is called polarized light pollution,{{cite journal|author2=György Kriska|author3=Péter Malik|author4=Bruce Robertson|date=August 2009|title=Polarized light pollution: a new kind of ecological photopollution|journal=Frontiers in Ecology and the Environment|volume=7|issue=6 |pages=317–325|doi=10.1890/080129|last1=Horváth|first1=Gábor|doi-access=free|bibcode=2009FrEE....7..317H }} and although it is certainly a form of ecological photopollution, "ecological light pollution" usually refers to the impact of artificial light on organisms.

In the night, the polarization of the moonlit sky is very strongly reduced in the presence of urban light pollution, because scattered urban light is not strongly polarized.{{cite journal|last=Kyba|first=C. C. M.|author2=Ruhtz, T. |author3=Fischer, J. |author4=Hölker, F. |title=Lunar skylight polarization signal polluted by urban lighting|journal=Journal of Geophysical Research|date=17 December 2011|volume=116|issue=D24|pages=n/a|doi=10.1029/2011JD016698|bibcode = 2011JGRD..11624106K |doi-access=free}} Since polarized moonlight is believed to be used by many animals for navigation, this screening is another negative effect of light pollution on ecology.

• Dark infrastructure
• Light effects on circadian rhythm
• Photobiology
• Scotobiology

{{Reflist|2}}

• [http://userpage.fu-berlin.de/~kyba/literature/ecol_light_pol.html List of peer reviewed ecological light pollution research papers]

{{Pollution}}

{{Public health}}

{{Artificial light sources}}

{{Environmental science}}

Category:Light pollution

Category:Ecological processes

Category:Pollution