The web site of the IUCN Dark Skies Advisory Group

INDEX

Environmental impact of light pollution

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 appropriate design and land development control 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.
• To 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, the 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, dark sky preserve, scotobiology, ecology of the night, starlight reserve and light pollution abatement 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 promote IUCN endorsement of dark skies and to provide summaries of, and 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 on behalf of the International Union for Conservation of Nature (IUCN) to other bodies in regards to light pollution and dark sky values, in particular as they relate to 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. In connection with IUCN’s role as an Advisory Body to the World Heritage Convention, the Group will also advise, assess and make recommendations to the IUCN Secretariat in regards to World Heritage studies and nominations that address or touch upon dark skies and light pollution.

The group consists of members of the Urban Conservation Strategies Specialist Group, which in turn reports to the World Commission on Protected Areas of IUCN. Depending on the nature of the group’s work, outcomes and products may be subject to approval of the Specialist Group or the Commission.

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 December 2018 the members are:

• Bruno Charlier, Pic du Midi International Dark Sky Reserve Project (France)
• Adam Dalton, Intgernational 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)
• Cipriano Marin, UNESCO Starlight Initiative (Spain)
• Juan José Negro, Donana 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, IUCN (Canada)
• Linda Wong, China Biodiversity Conservation and Green Development Foundation Secretariat, Beijing

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 are unable to survive seasonal changes.

Finally, humans are likely to feel that light pollution negatively affects their appreciation of the nighttime 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.

Further reading
• Light pollution and ecosystems.
• Ecological light pollution.
• Ecological consequences of artificial night lighting.

Dark skies and nature conservation

The web site of the IUCN Dark Skies Advisory Group

Dark sky advisory group

Beauties of Nature

Beasts in Nature