Chasing Stars in Neon Skies: Light Pollution and Its Impacts

Artificial lights at night cause light pollution, which impacts humans and nature alike. Earth.Org takes a closer look at some recent developments in this space.

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The night sky with its countless stars and cosmic colours has inspired art, literature, science and philosophy for centuries. In the natural world, stars guide nocturnal foragers as they hunt in the dark and help migratory birds adjust their internal compasses for the long journeys ahead. However, bright city lights have changed nightscapes around the world, making it increasingly difficult to spot stars with the naked eye. This form of pollution has received little attention until recently, but is an increasing cause for concern, especially as nearly 7 in 10 people globally are projected to live in cities by 2050. 

Bright Lights, Dim Stars

Artificial light has been a groundbreaking invention for humans, improving visibility in the dark and providing safety. However, too much of anything good can turn detrimental. Excessive or inappropriate use of outdoor artificial light causes light pollution. The highest levels of country-wide light pollution in the world can be found in Vatican City, Monaco, and Macau. In contrast, the Central African Republic, South Sudan and Tuvalu have the least ambient light.

Among the several forms of light pollution, the following can be commonly observed:

• Skyglow: The unnatural brightening of the night sky caused by artificial light, typically over populated areas, obscuring celestial objects.
• Glare: Intense, uncontrolled brightness that causes discomfort or reduces visibility.
• Light Trespass: Unwanted light spilling into areas where it is not intended or needed.
• Clutter: An overwhelming presence of too many light sources in one area that creates visual confusion and disorientation.

Several methods and tools have been used to understand the magnitude of light pollution and monitor it. 

The Bortle scale measures the quality of the night sky’s brightness at a specific location and consists of nine levels. Class 1 represents the darkest skies on Earth, while class 9 is the inner-city sky with barely any star visible. To gain a more comprehensive understanding of light pollution, a team of researchers led by Christopher Kyba incorporated data from citizen scientists to assess its impact on human visibility of the stars across the globe from 2011 to 2022. Participants were shown sky maps depicting varying levels of light pollution and asked to identify which one most closely matched their view. The resulting data revealed a concerning trend: the brightness of the night sky is effectively doubling every eight years. As a result, many observatories around the world are being forced to move to remote, dark areas or invest in light pollution mitigation technology.

Beyond Night Skies

Apart from impacting visibility of celestial objects, light pollution also affects wildlife, disorienting migratory birds and exposing nocturnal predators such as bats and cougars. While research into the effects of light pollution is ongoing, scientists have confirmed that it also significantly impacts plant growth. Artificial light alters a plant’s ability to respond to natural light and disrupts its seasonal cycles. Nocturnal pollination also diminishes impacting reproduction. 

Artificial light at night (ALAN) also interferes with the atmosphere, leading to decreased air quality and negative public health outcomes. To take an example, natural processes at night allow the nitrate radical to cleanse the air by reacting with volatile organic compounds to prevent the formation of ozone and smog. However, this vital reaction is hindered by brightness from urban lights, which, like sunlight, can degrade the nitrate radical and diminish its effectiveness. As a result, air quality is undermined, posing risks to health. 

Air pollution further feeds back into the loop by amplifying skyglow. Thus, tackling light pollution would effectively limit air pollution and vice versa.

Looking Ahead

Light pollution can be reversed and limiting it is the only way to reclaim dark skies and bring back order in the natural world. It also makes financial sense: a 2021 study revealed that global light emissions represent 250,000 gigawatt-hours of energy, adding up to at least $50 billion in energy costs. This is equivalent to at least 1% of global greenhouse gas emissions. Enhancing lighting efficiency and minimizing light waste would thus lead to a reduction in both planet-warming emissions and costs.

The DarkSky International and the Illuminating Engineering Society have released five principles for responsible outdoor lighting, which can be adopted by entities and individuals alike to prevent and reduce light pollution. Adhering to the principles will make sure outdoor light is used only when needed, targeted, no brighter than necessary, controlled, and warm-coloured. Motion sensitive lighting can reduce the amount of waste light emitted. Street lighting can be optimized by directing light downwards. This is achieved by positioning the bulb so that it is encased above and to the sides, channelling light towards the ground where required, rather than upwards.

A pioneer in the field of astronomical preservation, Coconino County in Arizona implemented the world’s first lighting ordinance in 1958. This revolutionary legislation aimed to limit the use of non-emergency searchlights to reduce light pollution and preserve the night sky. Building on this initiative, Coconino County later enacted the Flagstaff Light Ordinance, which restricts the amount of artificial lighting per acre, making Flagstaff the world’s first International Dark Sky City in 2001. Home to the renowned Lowell Observatory, Flagstaff’s efforts not only reflect a commitment to safeguarding the night sky but also serve as a model for other communities aiming to combat light pollution.

As we move forward, it is essential to remember that the night sky is not just a backdrop to our world – it is a shared resource that connects us to the broader universe. Every small step counts, whether it is a conscious effort to reduce light waste or supporting policies that protect dark skies. Together, we can reclaim the night, one light at a time.