Light Pollution Policy

(approved by Sierra Club Board 3/24/21)

Sierra Club recognizes that while artificial light provides desirable benefits to society, such as extended hours of social space at night, its excessive, inappropriate and poorly controlled use also leads to significant harm. Sierra Club defines light pollution as artificial light that adversely affects ecosystems and any living organism. Sierra Club includes in this definition anthropogenic light that is wasteful, or misdirected; has negative ecological impacts; is used as a form of aggression; is harmful to health, safety, or other human rights; or disrupts our view of the natural night sky, disconnecting us from our cosmic environment, including the Milky Way galaxy where we live. Therefore, light pollution imposes natural resource, economic, biological, political, psychological, and cultural burdens.

The Sierra Club recognizes that:

  • Artificial lighting has increased significantly, and continues to increase exponentially, and this problem exists not only in urban and suburban areas, but in rural areas as well.

  • Cumulative lighting impacts at night, and even during the day, arise from the proliferation of various types of artificial lighting, including:

    • street and parking area lights;

    • illuminated and digital billboard signs;

    • lighting from buildings and bridges;

    • greenhouse grow lights;

    • light cannons and laser beams;

    • decorative lighting, entertainment lights and light strings;

    • vehicle lights;

    • blinking, strobing and flashing lights;

    • flashlights and work lights;

    • spotlights, light towers and floodlights;

    • sports field and stadium lights;

    • illuminated drones; and

    • other forms of stationary, portable and moving light sources. 

  • The increased availability of cheaper and more energy-efficient lighting has the unintended consequence of increasing the number and distribution of sources that contribute to light pollution, leading to unnecessary or excessive lighting wasting energy and contravening environmentally responsible efforts to conserve energy, promote sustainability and cut down on greenhouse emissions that contribute to climate change and other adverse impacts of energy production.

  • The rapid and widespread adoption of blue-rich light-emitting diodes (LEDs), driven in large part by energy efficiency goals, has not adequately taken health and environmental impacts into account.

  • Short-wavelength (bluer) light worsens nighttime artificial skyglow because it scatters more in the atmosphere than longer wavelength (warmer) colors.

  • Artificial blue light at night causes more glare to humans and disproportionally and negatively affects a wide range of wildlife species. Artificial blue light can also disturb the production of melatonin that regulates the circadian rhythm in humans, and can cause or contribute to damage to living cells, blindness, physical and psychological stress, mood disorders, diabetes, obesity, and some forms of cancer.

  • Light pollution can also disproportionally and adversely affect people with higher light sensitivities or weaker immune systems.

  • Artificial light at night has documented negative ecological impacts, deadly in some instances, on both flora and fauna. Animal species documented to be adversely affected include, but are not limited to, sea turtles, bats, birds, insects, fish, corals and bioluminescent species. Artificial light has also been documented to affect the timing of fluorescence, pollination, growth, and/or dormancy in various plants, including nocturnally pollinated plants.

  • Well-directed lighting, no brighter than and when needed, in settings such as sidewalks, bike/ped paths, and street crossings can increase pedestrian visibility and provide wayfinding on highways. However, lighting that is improperly aimed, or excessively bright, or in dense clusters, or flickering or flashing, can trespass into or affect the personal space of others, including light entering via bedroom windows where it can contribute to loss of sleep and adversely affect human health and well-being. It can also cause dangerous glare that puts drivers, pedestrians, airplane pilots, and others at risk.

  • Excessive or harmful lighting is often prevalent in lower-income areas, including communities of color, and may be used or perceived as a form of policing, either through "smart" surveillance streetlights or via strategically placed lights. This contributes to environmental injustices, including neighborhood blight, increased stress, sleep deprivation, and worsen urban air pollution. 

  • Economically disadvantaged communities often lack the financial resources or political clout to install and maintain environmentally responsible and aesthetically pleasant lighting. Further, by precluding equitable and safe access to the emotional and recreational enjoyment of starry night skies, light pollution acts as yet another form of cultural and social injustice. Community lighting should not come at the expense of the right of all people to also enjoy the amenities of pristine night skies and nocturnal ecology and landscapes. Equitable investments and policies are needed that can achieve both objectives.

  • Light pollution impairs ground-based astronomical research and nocturnal citizen science.

  • Light pollution may also impact cultural and historical resources, long-treasured vistas stretching out from historic national parks overlooks, and indigenous people’s  traditional ways of life and tribal lands.

  • Decades of observations and research validate serious concerns over light pollution and the need for bold actions; however, there are data gaps that merit further research, such as how and to what extent are more species are affected.

As a result of these issues, the Sierra Club opposes unnecessary and harmful artificial lighting during the day and night.  To address light pollution, the Sierra Club supports:

  • The right of all living species to benefit from natural light and darkness, and to not experience fear or harm from artificial anthropogenic light;

  • Legislation; regulations; land use, building and zoning codes; resource management plans; best practices; institutional capacity; environmental assessments; light level monitoring; compliance monitoring and enforcement;

  • Funding; incentives; recognition programs; and educational initiatives that help to equitably reduce light pollution in all its forms and to protect, conserve and restore natural light in all types of ecosystems, including diurnal and nocturnal habitats, and in the day and night sky;

  • Enforceable ordinances, standards and best practices that avoid or minimize light pollution and its adverse ecological effects; protect public health; reduce energy waste; and improve energy efficiency (for both new and existing lighting). These must include comprehensive policies and measures to equitably address the complexity and breadth of ecological and public health burdens from light pollution;

  • Restrictions on spectral power distribution (which defines energy levels for each wavelength in a light source), sub-sensory flicker, contrast between ambient and artificial light, luminous flux (lumens), luminance, brightness levels, light trespass, time and duration of light use, mobile lights, and blinking, flashing and strobing lights;

  • Curfews and “lights out” initiatives that limit the use and timing of harmful and unnecessary outdoor lighting, such as during sea turtle nesting season, and bird and insect migratory seasons;

  • New, safe and available sustainable lighting technologies and practices that save energy; use clean renewable energy; and prevent or reduce adverse effects of excessive artificial lighting, including:
    (1) timers, motion sensors, dimmers and adaptive lighting controls to reduce the duration and brightness of outdoor lighting and to automatically turn off lights when the sun is shining;
    (2) energy-efficient lighting that is adequately shielded (indoors and outdoors); that illuminates only where and when light is needed; that is downward directed; that avoids glare and light trespass (unwanted light falling on unintended areas); that is mounted as close as possible to the ground; and that avoids or minimizes harmful spectra (colors), including blue light emissions at night (such as via color-tunable lighting, filtered and PC amber LEDs, and low pressure sodium);
    (3) lighting diffusers that soften light to prevent harsh light;
    (4) electronics that prevent sub-sensory flicker; and
    (5) reflective paints and markers that provide safe wayfinding and help reduce need for permanently installed outdoor lighting;

  • Just and equitable access to sustainable and necessary lighting during the day or at night that avoids or minimizes adverse effects on people, wildlife and the environment;

  • Daylighting inside buildings to save energy and minimize need for artificial light indoors; and

  • Research that furthers our understanding of the adverse effects and positive solutions to light pollution in all settings, including but not limited to urban, rural and conservation areas.

Adopted by the Sierra Club Board of Directors, March 24th, 2021

Note:   A light policy was initially adopted by Sierra Club in May 1971.  The March 2021 update was informed by the review of several resources published by non-profit organizations, researchers, government agencies, and others that have described light pollution sources, impacts and solutions. Find these resources here.