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 is part of the Urban Conservation Strategies Specialist Group of the World Commission on Protected Areas, a Commission of the International Union for Conservation of Nature.



Basic statement
Advisory Group: role and members
Environmental impact of light pollution
Outdoor lighting guidelines
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 (tangible heritage).
• To help preserve cultural practices and ceremonies relate 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 (starlight tourism) and the right for all people to enjoy a clear, unpolluted night sky.
• To improve personal security through non-glare lighting in urban areas.

The International Union for Conservation of Nature (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 IUCN’s World Commission on Protected Areas to help advance this recognition.  With the support of the Initiative for an International Association of Dark Sky Parks, the Group provides this web site to encourage protected areas and communities to embrace the concept and values of dark skies.  Web searches using terms like dark skies, starry skies, 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 and will not try to replicate these.  Rather, our aim is to provide IUCN endorsement of dark skies initiatives and to provide signposts to further information.


For the International Union for Conservation of Nature:

David Welch, Chair, Dark Skies Advisory Group, and
Ted Trzyna, Leader, Urban Conservation Strategies Specialist Group.


Dark Skies Advisory Group (DSAG): role and members

Established in 2009, the Group provides advice and guidance to and on behalf of the International Union for Conservation of Nature 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, which in turn reports to the World Commission on Protected Areas of the IUCN. Group members volunteer their time, either within the scope of their employment or business or as private citizens.

Group members volunteer their time, either within the scope of their employment or business or as private citizens. Subject to its capacity and priorities as outline above, the Group will respond to requests for advice directly from individuals and organizations.

As of September 2021 its members are:
• Bruno Charlier, Pic du Midi International Dark Sky Reserve Project (France)
• Ashley Wilson, International Dark Sky Association (USA)
• Robert Dick, Royal Astronomical Society of Canada
• David Goldstein, Northeast Regional Office, National Park Service ( USA )
• István Gyarmathy, Hortobágy National Park (Hungary)
• John Hearnshaw, University of Canterbury (New Zealand)
• Travis Longcore, The Urban Wildlands Group (USA)
• Antonia Varela Perez, Fundación Starlight (Spain)
• Juan José Negro, Doñana Biological Station (Spain)
• Clive Ruggles, International Astronomical Union Working Group on Astronomy and World Heritage (UK)
• Woody Smeck, Sequoia and King’s Canyon National Parks (USA)
• Jurij Stare, Initiative for an International Association for Dark Sky Parks (Slovenia)
• Karen Trevino, Natural Sounds and Dark Skies Division, National Park Service (USA)
• Ted Trzyna, Leader, IUCN WCPA Urban Conservation Strategies Specialist Group (USA)
• John Waugh, Semaphore Inc. (USA)
• David Welch, Chair, Dark Skies Advisory Group,(Canada)
• 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

Nature-friendly outdoor lighting follows these principles.
• 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.
• Direct light so that it only falls where it is needed. 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. Rather, 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.

Outdoor lighting specifications are suggested for various situations typical of protected natural areas. These include park buildings, vending machines, washrooms, paths, roads, shorelines, signs, navigation towers and community enclaves. Specifications are also offered for other built situations such as historic sites, commercial zones, residential areas, billboards and roads. In general, artificial light at night should be avoided or reduced to the minimum required for public safety and to meet regional and national regulations. For more details go to rasc.ca/sites/default/files/RASC-CGOL_2020_0.PDF.


The DSAG class system of dark sky places

There are many terms in use for dark sky protected areas and sites. They are used by several dark sky certification agencies, and appear in conference and workshop proceedings, and in communications with dark sky experts in various countries. 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.

Each dark sky place is judged overall for the best class to apply. However, if a dark sky place fits more than one class equally well, the following binary key is used to determine the DSAG class.

Does the dark sky place contain a research astronomy facility?
  If yes: 1 Starlight Reserve: astronomy observatory site and surrounding area
  If no, then:

Is the dark sky place a natural or rural area?
  If yes: 2 Dark Sky Park: protected natural area
  a Park, reserve, habitat area or other ecological protection. Or:
  b Rural or natural area set aside for traditional or sacred practices related to the sky. Or:
  c Rural area, area of outstanding landscape beauty
  If no, then:

Does the area protect heritage structures?
  If yes: 3 Dark Sky Heritage Site: protected heritage buildings or other physical works of mankind
  If no, then:

Is the area or site within a greater urban region and its surrounding rural area, and managed for public night sky viewing?
  If yes: 4 Dark Sky Outreach Site
  a Urban or suburban site. Or:
  b Rural site
  If no, then:

Is the area a mix of cooperating community, rural and natural area jurisdictions?
  If yes 5 Dark Sky Reserve
  If no, then:

Does the area correspond to an entire rural municipality, village, town or city?
  If yes: 6 Dark Sky Community
  a City, town or village. Or:
  b Populated rural area without a formal protected area



Dark sky advisory group

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