Dark skies and nature conservation

The web site of the IUCN Dark Skies Advisory Group

Managing artificial light to protect natural systems and to appreciate the night sky


The Dark Skies Advisory Group (DSAG) is part of the Urban Conservation Strategies Specialist Group of the World Commission on Protected Areas (WCPA), a Commission of the International Union for Conservation of Nature (IUCN).



Basic statement
Advisory Group: role and members
The environmental impact of light pollution
Outdoor lighting guidelines
The World At Night, IUCN report on light pollution and dark sky protection
The DSAG class system of dark sky places


Contact us: dsag.iucn@gmail.com

Basic statement

We are creatures of light, but in recent centuries our technology has enabled us to push back the frontier of darkness, extending our work and leisure time well into the hours of twilight and darkness. We tend to forget, however, that ecosystems and wild species operate 24 hours each day, seven days each week. They have evolved to cope with, depend on and take advantage of natural darkness. A night sky without artificial light is therefore vital to the proper functioning of natural ecosystems. Artificial lighting affects species migration patterns, predator-prey relationships, and the circadian rhythms of many organisms, to name just a few of the consequences of light pollution. Natural darkness is also essential to a full appreciation of our surroundings, to satisfy curiosity, to appreciate our environment in all its facets, and to preserve our diverse cultural integrity. However, compared to climate change, acid rain, exotic species, habitat destruction and other stresses, the need for natural darkness and the impacts of artificial lighting are often overlooked as we strive to protecting biodiversity and to appreciate the natural world and our cultural heritage.

There are at least ten reasons to reduce light pollution and to protect a natural night sky. They go beyond nature conservation to touch upon urban design and sustainable development policies.

• To preserve the ecological integrity of natural environments.
• To ensure the full enjoyment of a wilderness experience.
• To appreciate the integrity, character and beauty of rural landscapes.
• To protect and present the authenticity of cultural sites.
• To help preserve cultural practices and ceremonies related to the night sky.
• To help preserve the intangible heritage that relates to mythology, traditional navigation and cultural heritage related to the night sky.
• The protect human health, both medical and psychological.
• To contribute to energy efficiency.
• To benefit scientific and amateur astronomy and the right of all people to enjoy a clear, unpolluted night sky.
• To improve personal security through non-glare lighting in urban areas.

Improperly shielded outdoor light at night reflects from atmospheric particles, even moisture, and creates artificial skyglow. This haze of light prevents us from seeing most stars and the seven galaxies that should be visible to the naked eye. A clear, unpolluted night sky is also central to the cultural values of many societies around the world. An estimated 60% of Europeans and 80% of Americans have never seen the Milky Way, even on a cloudless night. Up to 1/6 of outdoor lighting is wasted by going directly to space. Light trespass into residences leads to sleep disturbance and contributes to several human health issues. The direct glare from over-bright and poorly shielded street and building lights compromises security by reducing our ability to see into shadows. Whether rural or urban, excess lighting interferes with nature’s predator-prey relationships and disturbs the seasonal and daily rhythms of many plants and animals. Bright lights confuse migrating birds and contribute to deadly bird impacts on buildings. Sunlight reflected from satellites threatens the future of ground-based astronomy, both for science and for the public enjoyment of the night sky.

The IUCN recognizes the importance of natural darkness to nature conservation, to ecological integrity of protected areas, and to the sustainability of healthy lives in healthy cities. The Dark Skies Advisory Group has been established within the WCPA to help advance this recognition, to provide IUCN endorsement of dark skies initiatives and to provide signposts to further information.

Dark Skies Advisory Group role and members

Established in 2009, DSAG provides advice and guidance to and on behalf of the IUCN, and to individuals and other bodies in regards to light pollution and dark sky values. Its particular focus is on the ecological and commemorative integrity, visitor appreciation and public understanding of protected areas, and the long term maintenance of dark sky values for future generations.

The group consists of members of the Urban Conservation Strategies Specialist Group [ theurbanimperative.org ], which in turn reports to the World Commission on Protected Areas [ www.iucn.org/our-union/commissions/world-commission-protected-areas ] of the IUCN [ iucn.org ]. Group members volunteer their time, either within the scope of their employment or business or as private citizens.

As of February 2024 its members are:
• Bruno Charlier, Pic du Midi International Dark Sky Reserve Project (France);
• Robert Dick, Royal Astronomical Society of Canada;
• István Gyarmathy, Hortobágy National Park (Hungary);
• Amber Harrison, DarkSky International (USA);
• John Hearnshaw, University of Canterbury (New Zealand);
• Christopher Kavanagh, Natural Sounds and Dark Skies Division, National Park Service (USA);
• Travis Longcore, The Urban Wildlands Group (USA);
• Juan José Negro, Doñana Biological Station (Spain);
• Catherine Rich, The Urban Wildlands Group (USA);
• Clive Ruggles, International Astronomical Union Working Group on Astronomy and World Heritage (UK);
• Jurij Stare, Initiative for an International Association for Dark Sky Parks (Slovenia);
• Ted Trzyna, Leader, IUCN WCPA Urban Conservation Strategies Specialist Group (USA)
• Antonia Varela Pérez, Fundación Starlight (Spain);
• John Waugh, Semaphore Inc. (USA);
• David Welch, Chair, Dark Skies Advisory Group,(Canada); and
• Linda Wong , China Biodiversity Conservation and Green Development Foundation Secretariat


The environment impact of light pollution

Biological systems evolved under the influence of the day/night cycle and its annual variation. They have developed light/dark sensing techniques that ensure the integration of their behaviour into the yearly progression of the seasons. Light pollution negatively affects their ability to fit their developmental and reproductive behaviour to the appropriate time of year. Light pollution may also affect the diurnal behaviour and activities of animals, with severe or extreme consequences. The impacts of light pollution on five major groups of organisms are briefly surveyed below.

Wild animals may have their hunting, feeding and breeding activities seriously affected by light pollution. It may also negatively affect their capacity for orientation and their ability to navigate effectively through their environment. The breeding and feeding activities of fish may also be compromised.

Birds are seriously affected by light pollution. They may suffer navigation problems from night lights during migration and become seriously disoriented. They tend to fly toward bright lights, and the death toll from their collisions with lights or brightly lit windows and buildings is very large. Their feeding habits, particularly of those that eat flying insects, can suffer from the effects of light pollution on their own behaviour as well as on the behaviour of the insects on which they feed.

Insects suffer disorientation and death from attraction to lights in the night. Their numbers are also decreased because they congregate under bright lights and become easy prey for insect-eating birds. They also suffer losses due to the interruption of their normal breeding habits by light pollution.

Plants have evolved to use the seasonal cues of changing day/night lengths in order to fit their annual developmental and breeding programs to the appropriate seasons. Light pollution prevents them from using these seasonal cues so that their breeding activities are compromised or prevented, and their development, particularly in their preparation for winter, may be affected to the point that they re unable to survive seasonal changes.

Finally, humans are likely to feel that light pollution negatively affects their appreciation of the night environment. It may also cause sleep deprivation as well as psychological disturbances that can have serious and sometimes lasting effects.

Overall, light pollution has no beneficial effects on the biological components of the environment: it only helps humans who wish to see in the dark. Its effects on the biological components of the environment are often seriously negative or even deadly, so lighting schemes should be developed that minimize these impacts.


Outdoor Lighting Guidelines

• Use light only if it is needed. Consider how the use of light will impact the area, including wildlife interactions and habitats. Rather than permanent lights, use reflective paint or self-luminous markers for signs, curbs and steps. Outdoor lighting should not be used for aesthetic purposes.
• Use the least amount of light needed. The amount of light should be appropriate for the activity taking place. Be aware of surface conditions as some surfaces reflect a lot of light into the sky.
• Minimise blue and violet spectral components. Use lights with a colour temperature less than 2700K, preferably less than 2200K. This aids night vision by all animals, including people.
• Use shielding so that the light beam does not spill beyond where it is needed and minimises the contaminated area. Do not use lights that project any part of their beam into the sky. Restrict beams to downward cones to reduce glare. This improves the ability of drivers and pedestrians to see into shadows.
• Use light only when needed. Active controls such as timers or motion detectors help ensure that light is available only when needed. Examples include curfews for arena lighting, and motion sensing and dimming for pedestrian areas.
• Encourage neighbours to reduce their light pollution, particularly glare and light trespass into your domain.
• Use energy efficient lights, provided that they do not conflict with the other principles.

The World At Night, IUCN report on light pollution and dark sky protection

Published in 2024, this report expands on the themes noted above, explaining light pollution, why it matters and how to reduce it. While centred on nature protection, it also addresses the importance of abating light pollution for cultural and traditional heritage conservation, wilderness enjoyment, security, energy conservation, human health, astronomy and the enjoyment of a natural night sky, from seeing galaxies and stars to planets, comets, meteors and aurorae. Download The World At Night from [ https://portals.iucn.org/library/node/51414 ].

The IUCN has twice recognized the significance of light pollution through motions at its World Conservation Congresses. As well, in 2007 the United Nations Educational, Scientific and Cultural Organization, the International Astronomical Union, the Council of Europe, the Secretariat of the Convention on Biological Diversity and other international organizations together issued a Declaration in Defence of the Night Sky and the Right to Starlight. These motions and declaration are included in the report.

This 160 page report summarizes the lessons learned from certified dark sky places. Dark sky guidelines are suggested for conservation management in urban, natural or heritage areas. Options are offered for public engagement through park interpretation, school events, public engagement, community outreach and media contact. Examples of national, regional and municipal light pollution laws and policies are described. Other topics include light pollution scales and measurement devices. Recommendations for different situations are given for spectrum, illumination levels and appropriate fixtures.

As the world urbanises and as more communities gain access to electrical grids, there is an ever-growing amount of light pollution on Earth, a trend exacerbated by the onset of ultra-efficient LED lighting. This makes it easy to provide far more light than is needed. This report encourages architects, planners and environmental and building managers to help abate light pollution, and to help concerned citizens to spread the word about light pollution. Everyone has the right to enjoy an unpolluted night sky and the natural world that goes with it.

The DSAG class system of dark sky places

Web searches using terms like dark sky, starry sky, dark sky preserve, ecology of the night, starlight reserve and artificial light at night quickly reveal many useful and comprehensive web sites which provide guidance on intelligent lighting, enjoyment of the night sky, and understanding of the impacts of light pollution on humans and nature. The Dark Skies Advisory Group does not try to replicate these.

Several organizations certify places with appropriate outdoor lighting policies and practices that minimize sky glow, that are compatible with nature conservation, and that offer interpretation and outreach programmes to residents and visitors alike. As of February 2024 there are over 325 such dark sky places in 34 countries, from strictly protected areas to astronomical research sites, from biosphere reserves to towns and villages. There are many terms in use for these dark sky protected areas and sites. Here are some examples.

• Dark Sky Park
• Dark Sky Preserve
• International Dark Sky Park
• International Dark Sky Reserve
• International Dark Sky Community
• Suburban Outreach Site
• Starlight Reserve
• Starlight Oasis
• Starlight Theme Park
• Starry Sky Park
• Urban Star Park
• Urban Night Sky Place

In practice, different name sometimes mean the same thing. For example, a dark sky preserve in Canada is equivalent to a dark sky park in the sense used by the International Dark Sky Association (IDA). To avoid confusion, and to help with reporting in an international context such as through the World List of Dark Sky Places, DSAG has developed a common class system.

A similar situation exists for parks, reserves and other names for protected natural areas. To facilitate international comparison and reporting, the IUCN uses a system of six categories. For example, a national park in the United Kingdom fits under category V, whereas a national park in Canada is category II. The category numbers do not indicate relative importance. All are of equal value in the protection of natural spaces and cultural landscapes. The full definitions are posted on-line at www.iucn.org/about/work/programmes/pa/pa_products/wcpa_categories/. These are the categories.

I      Strict protection
       Ia   Strict Nature Reserve
       Ib   Wilderness Area
II     Ecosystem conservation and recreation (National Park)
III    Conservation of natural features (Natural Monument)
IV    Conservation through active management (Habitat/Species Management Area)
V     Landscape/seascape conservation and recreation (Protected Landscape/Seascape)
VI    Sustainable use of natural ecosystems (Managed Resource Protected Area)

The IUCN approach to protected area categories is adopted as a model for the DSAG system. To qualify as a dark sky protected area, a place should:
• be an officially protected area in the sense understood by the IUCN;
• have management policies and practices in place to protect or restore natural darkness; and
• be recognized either by an authoritative body at arms length from the protected area agency itself, for example the IDA, the Royal Astronomical Society of Canada, the Hungarian Astronomical Union, or by legislation, regulation or policy of the appropriate national, territorial, state or provincial jurisdiction.

A class for dark sky communities is added to facilitate the inclusion of the IDA’s dark sky community designation, and recognizing the importance of nature conservation even in urban areas.

1 Starlight Reserve: research grade astronomical observatory site and surrounding protected area.
2 Dark Sky Park: protected natural area.
    2a Park, reserve, habitat, natural area or other ecological protection.
    2b Unpopulated area set aside for traditional or sacred practices related to the sky.
    2c Rural area, area of outstanding landscape beauty.
3 Dark Sky Heritage Site: protected astroarchaeological heritage work(s) of mankind.
4 Dark Sky Outreach Site: a site managed for public night sky viewing.
    4a Urban or suburban site.
    4b Rural site.
5 Dark Sky Reserve: mix of cooperating community, rural and natural area jurisdictions, similar in concept to a UNESCO biosphere reserve.
6 Dark Sky Community: city, town, village or populated rural area.
    6a City, town or village.
    6b Populated rural area without a formal protected area.

Follow the links on the DSAG home page to access the world list and map of dark sky places.


Dark sky advisory group

Beauties of Nature

Beasts in Nature