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TECHNICAL SERIES REPORT

International Light Pollution Guidelines for Migratory Species

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 What is light pollution?

“Light pollution refers to artificial light that alters the natural patterns of light and dark in ecosystems.” – Resolution 13.5 (Rev.COP14).

The increasing use of artificial light at night (ALAN) has modified the natural light environment dramatically which can impact both humans and wildlife. Unlike other pollutants, light pollution disrupts behaviours and physiology without directly entering organisms’ bodies, affecting ecological balance. ALAN can be direct, such as beams emitted by streetlights, but it can also be scattered and reflected back from the atmosphere as artificial ‘skyglow’ which can have an influence far beyond individual light sources. Other types of light pollution include glare (contrasts between bright and dark areas), over-illumination, light clutter (unnecessary numbers of light sources) and light trespass (unwanted light). Light pollution is not constant and can vary; atmospheric conditions such as humidity, aerosols, clouds, haze, atmospheric pollution, and snow influence sky brightness, thereby affecting how it is measured and perceived.

 

 

 Artificial light at night

Insects attracted by the light of a street lamp © Gina Media/Getty Images

Artificial light emissions have been increasing over the last century. Between 2012 and 2016, the global artificially lit outdoor area was estimated to have increased by 2.2% per year. Light pollution affects 23% of the world’s land surfaces between 75°N and 60°S, including 88% of Europe and almost half of the United States. It is also estimated to affect 1.9 million square kilometers of coastal seas at a depth of 1 meter. Some countries have seen higher rates of increase and there are few places where lighting growth has remained stable or decreased. It is expected that artificial light emissions will continue to increase. As low energy light sources such as LEDs become more common, this can lead to more artificial lighting being installed as LEDs can be more energy efficient to use. Between 2011 and 2022, the average night sky got brighter by 9.6% per year.

 

 

 

 Effects on wildlife

Wildlife has evolved under consistent light conditions including day and night, lunar cycles, predictable star patterns and seasonal variations in day length. Natural light is used as a resource to help wildlife gain spatial and temporal information about the environment. Light enables vision for some species, for example for foraging, while darkness can provide essential cover for wildlife to remain hidden and creates optimal conditions for nocturnal species to hunt. Depending on these behavioural needs, animals can move towards or away from light. Light and darkness are involved in mechanisms which regulate physiology such as metabolism, growth, behaviour and the healthy functioning of biological clocks. Day length is an important cue for many animals living in seasonal environments. Light pollution can disrupt these natural processes. It can lead to hormonal imbalances and can affect sleep patterns. Reproduction, dormancy, navigation and migration can all be impacted. Light pollution can be a particular issue for nocturnal species but animals active during the day, dawn or dusk may also be impacted.

For more information, please refer to the CMS International Light Pollution Guidelines for Migratory Species. These guidelines detail the adverse impacts of light pollution on wildlife and offer practical recommendations for addressing the issue. They are designed for a broad audience, including governments, municipalities, urban planners, developers, and other stakeholders, and outline actions to reduce light pollution and mitigate its effects on migratory species and ecosystems.

 

 

 Light Pollution and International Commitments

Reducing light pollution supports international efforts under the Kunming-Montreal Global Biodiversity Framework (GBF). Target 7 specifically addresses pollution, including light pollution, as a disruptor of biodiversity and ecosystem functions. By mitigating light pollution, we help safeguard biodiversity, restore natural rhythms, and ensure healthier ecosystems. This also aligns with the Sustainable Development Goals (SDGs), promoting environmental sustainability and resilience and contributing not only to the targets aiming at protection of wildlife below water and on land, but also to a number of other development goals:

 

Sustainable Development Goals

Sustainable Development Goals Poster

SDG 14 – Life Below Water  

Artificial light in coastal zones, as well as from boating activities and oceanic infrastructure, disrupts marine organisms’ behaviours, life cycles, migrations, and reproduction, including sea turtles, fish, and plankton. Reducing light pollution supports Targets 14.1, 14.2, and 14.5 by restoring natural rhythms and fostering healthier marine ecosystems.

SDG 15 – Life on Land  

Artificial lighting interferes with terrestrial ecosystems reliant on natural light cycles. Reducing light pollution enhances biodiversity conservation and strengthens land ecosystems’ resilience, addressing Targets 15.1, 15.5, and 15.9.

SDG 3 – Good Health and Well-Being  

Light pollution is known to associated with negative health impacts to humans including increased risk of obesity, depression, sleep disorders, diabetes and breast cancer. LED lighting can often contain more short wavelength blue light, known to cause more glare to humans as they age making navigating artificially lit environments at night more difficult.

SDG 9 – Industry, Innovation and Infrastructure  

Much of ALAN comes from infrastructure. As technology advances there is an opportunity to build lighting infrastructure that is both adaptable to current and future needs as well as being inclusive of community and environmental needs while reducing energy use.

SDG 11 – Sustainable Cities and Communities  

Minimising excessive artificial lighting aligns with Target 11.3 by promoting sustainable urbanisation through reduced energy costs, Target 11.4 by safeguarding cultural and natural heritage and reconnecting communities with the night sky, and Target 11.6 by lowering environmental impact through decreased energy demand and greenhouse gas emissions.

SDG12 – Responsible Consumption and Production  

Transitioning to LEDs can mean better efficiency with global lighting infrastructure. But considering light pollution in smart lighting can increase efficiency further by only using lights when they are needed.

SDG 13 – Climate Action  

Reducing light pollution lowers energy consumption and supports healthier ecosystems, contributing to climate resilience and action.

 

Light Pollution in other Multilateral Environmental Agreements (MEAs)

White Stork in front of full moon © Pexels.com

CMS  

Resolution 13.5 (Rev.COP14) on CMS International Light Pollution Guidelines for Migratory Species was adopted by the Conference of the Parties as its 14th Meeting (Samarkand, February 2024).

CBD  

Kunming-Montreal Global Biodiversity Framework (GBF). Target 7: Reduce Pollution to Levels That Are Not Harmful to Biodiversity

IUCN  

In 2024 the International Union for Conservation of Nature (IUCN) World Commission on Protected Areas (WCPA) published the World At Night Report to explain light pollution, why it matters and how to reduce it.

Ramsar  

The Global Wetland Outlook (2018) recognises marine light pollution as one of the factors contributing to wetland change, with almost a quarter (22.2%) of global coastline exposed to nightly artificial light.

UNESCO  

In 2016 UNESCO published The Right to Dark Skies.

UNOOSA  

In October 2020 an online workshop took place Dark and Quiet Skies for Science and Society followed by another workshop in October 2021, Dark and Quiet Skies for Science and Society II. In April 2021, Recommendations to Keep Dark and Quiet Skies for Science and Society were submitted to the International Astronomical Union.

 

In 2007 representatives of UNESCO, UNWTO, IAU, UNEP-CMS, COE, SCBD, MaB, EC and Ramsar Convention agreed to the Starlight Declaration in Defence of the Night Sky and the Right to Starlight.

 

Migratory Species and Light Pollution

A green sea turtle hatchling races across the beach towards the ocean at Pulau Libaran, Borneo © Goddard_Photography/Getty Images Signature

The CMS recognises the significant impacts of artificial light, which disrupts critical wildlife behaviours and ecological processes. It can hinder the recovery of threatened species and interfere with migratory species’ ability to complete long-distance migrations essential to their life cycles. Artificial light also affects insects, a primary food source for many migratory species. Acknowledging these challenges, the CMS is committed to continuously developing and enhancing international guidelines to mitigate light pollution’s effects on biodiversity.

CMS Mandate  

At its 13th ordinary meeting (COP13, Gandhinagar, February 2020), the CMS first addressed light pollution through Resolution 13.5, which highlighted its growing global prevalence and adverse effects on wildlife and ecosystems. Australia presented their national guidelines on light pollution, laying the foundation for developing international standards.

Building on this groundwork, COP14 (Samarkand, February 2024) adopted the CMS International Light Pollution Guidelines for Migratory Species, which includes additional species-specific guidance to mitigate impacts on migratory landbirds and bats. Decision 14.222 further mandates the preparation of additional species-specific annexes, where required, for COP15, focusing on taxa not yet covered by the current guidelines.

 

  Resources

 

 

 

 

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