Light Pollution: Any Silver Linings To This Dark Cloud?

Light pollution, defined as the excessive or inappropriate use of outdoor artificial light, is a global issue that has been linked to adverse effects on human health, wildlife behaviour, and our ability to observe the night sky. However, amidst the negative impacts, there are a few positive outcomes associated with light pollution that have been observed in certain contexts. For example, it has been found that light pollution can benefit some migratory birds by providing them with more time to forage for food and making it easier to locate prey by sight rather than touch. In terms of human benefits, street lights enhance road safety, and appropriate lighting in public spaces can positively impact social well-being. Additionally, LEDs have lowered electricity costs for lighting, and 24-hour lighting provides an increased sense of safety and round-the-clock access to goods and services. While these positive effects exist, it is important to recognize that light pollution's detrimental consequences on human health, wildlife, and the environment are significant and have sparked a global movement to address this issue.

Light pollution helps migratory birds find food at night

Light pollution has traditionally been viewed as a negative phenomenon, with its effects on wildlife, astronomy, and human health well documented. However, a recent study by the University of Exeter has revealed that light pollution can have some positive effects on wildlife, specifically migratory birds. The study found that light pollution helped migratory birds find food at night, improving their feeding habits and, consequently, their survival rates.

The study focused on the common redshank (Tringa totanus) in the Forth estuary of eastern Scotland, an area that serves as a winter home for hundreds of thousands of birds migrating from the Arctic. The researchers compared the feeding habits of birds under continuously illuminated conditions to those in darker areas. They found that the illuminated conditions enabled the birds to forage for longer and locate food by sight rather than touch, resulting in improved energy reserves for the return trip to their summer breeding grounds.

The artificial light in the study area was emitted from lamps and flares at the Grangemouth oil refinery and Longannet power station, creating the effect of a perpetual full moon. This additional light source allowed the birds to switch to a more effective foraging behaviour, capitalising on the extended periods of moonlight to locate prey. The use of radio transmitters attached to the birds' backs further validated these findings by providing data on their feeding behaviour.

While light pollution has been recognised as a threat to nocturnal biodiversity, this study highlights a more complex reality. The presence of artificial light can benefit migratory birds by enhancing their ability to find food, particularly during the winter when food sources are scarcer. This positive impact on bird populations in industrialised areas or near coastal cities may help offset some of the negative consequences of human development on their natural habitats.

However, it is essential to acknowledge that light pollution remains a significant concern for bird conservation. The very same lights that can aid in food location can also attract birds during migration, drawing them towards urban areas where they face hazards such as colliding with buildings or glass structures. This disorientation caused by artificial lights can directly impact their ability to migrate successfully, underscoring the complex relationship between light pollution and its effects on migratory bird populations.

Street lights improve road safety for humans

Street lights are essential for improving road safety for humans. Boyce (2019) asserts that street lights enhance safety for road users, including vehicles, pedestrians, and cyclists. This is especially critical at night when visibility is reduced.

LED street lights, in particular, have been shown to improve road safety significantly. LED lights offer superior brightness and clarity, uniformly producing a brighter and more focused light output that covers a larger area. This enhanced visibility helps drivers see distant objects more clearly, reducing the risk of accidents. The targeted lighting feature of LED street lights enables precise direction of light towards specific locations, such as crossroads and pedestrian crossings. This not only reduces light pollution and glare but also enhances visibility for all road users, creating a safer environment.

The improved color rendering of LED lighting is another advantage. It provides a spectrum of natural colors, enhancing the accuracy of perception of the surrounding environment. This can be crucial for identifying potential hazards or obstacles on the road. Furthermore, LED lights consume less energy than traditional light sources, making them more energy-efficient and cost-effective.

While street lights undoubtedly improve road safety, it is important to acknowledge that excessive lighting or improper lighting design can have adverse effects. Glare from bright, unshielded lights can cause discomfort for drivers and even obscure road markings, compromising safety. Additionally, while well-lit areas may subjectively feel safer, there is no clear scientific evidence that increased outdoor lighting deters crime or improves safety.

To strike a balance, smart lighting that directs light where it is needed can be employed. This type of lighting aims to create a balance between safety and preserving the visibility of the night sky. By minimizing glare and properly addressing the glare factor, street lights can maximize visibility, which is crucial for road safety.

Artificial light can improve social well-being

Artificial light has transformed outdoor environments, modifying natural light cycles in terms of time and wavelength. While light pollution is a relatively modern social issue, artificial light has been a part of human life for a long time, from the use of candles and flame-operated lamps to the advent of electricity and incandescent lights. Today, artificial light at night (ALAN) is ever-present and has improved the quality of life for humans through increased productivity, convenience, safety, and liveability.

The use of appropriate lighting at night in public spaces can benefit people's social well-being. For example, street lights enhance road safety for humans. Lighting is a vital environmental element that affects people's outdoor activities and the creation of liveable neighbourhoods in cities. Research has examined the effects of urban morphological characteristics on outdoor night-time lighting behaviours in 11 urban neighbourhoods in Shenzhen, finding that maximising the amount of light entering the home has a larger impact on emotional subjective well-being (E-SWB). Increased space between dwellings and larger, sun-facing windows improve E-SWB, particularly for women and young people.

However, it is important to note that artificial light can also have adverse effects on human health and behaviour. Artificial light can disrupt the human body clock and the hormonal system, leading to health problems. The ultraviolet and blue light components of artificial light have the greatest potential to cause harm, and there are concerns that new energy-saving lamps may negatively affect those with light-sensitive conditions. Additionally, the flickering of artificial lights has been linked to headaches, seizures, and neurological impacts, and there may be a connection between fluorescent lighting and increased anxiety symptoms in patients with agoraphobia.

Furthermore, while artificial light can benefit some wildlife, it can also threaten nocturnal biodiversity. For example, while migratory birds in illuminated areas can forage for longer and locate food more easily, light pollution can disrupt the behaviour of animals that move between land and sea. The broader environmental impacts of lighting schemes have also eroded the natural aesthetic of the night sky, and there are concerns about the effects of sky glow on scientific astronomy. Therefore, it is crucial to develop unified measurement techniques and tailored lighting systems to balance the benefits of artificial light with minimising adverse effects on health, the environment, and ecosystems.

Warmer LEDs can reduce harm to melatonin production

Light pollution, particularly from LEDs, has been found to suppress melatonin production in humans and animals. Melatonin is a hormone that influences our circadian rhythms and is produced in greater quantities in the dark. Blue light, in particular, has been found to suppress melatonin production for longer and shift circadian rhythms more than other types of light.

LEDs are a common source of blue light, and their use in streetlights and digital devices has been linked to disrupted sleep patterns and adverse health effects. However, LEDs can be modified to reduce the potential harm to melatonin production.

The issue with LEDs lies in the high amount of blue light they emit. By removing the blue light from LEDs or using amber LED lights, melatonin levels can be maintained at a level comparable to natural darkness. This was demonstrated in a study on wallabies, where those exposed to blue-shielded LEDs or amber LED lights showed similar melatonin levels to those in natural darkness.

Warmer LEDs, which emit less blue light, can thus reduce the harmful impact on melatonin production. This can be achieved by using coatings inside the bulbs to produce a warmer light. While this approach may mitigate the negative effects of blue light on melatonin, it is important to recognize that LEDs still contribute to light pollution and can have other ecological impacts.

Light pollution may reduce bat activity

Light pollution, or artificial light at night (ALAN), has been shown to have both positive and negative effects. While it has disrupted the natural aesthetic of the night sky, it has also been found to benefit some wildlife and human health. For example, light pollution can help migratory birds find more food at night. It also provides safety to humans at night. However, the benefits of light pollution are not always applicable to bats.

Bats are nocturnal wildlife that are particularly affected by light pollution. A study by Dr. Chad Seewagen and colleagues found that light pollution can have far-reaching effects on light-averse North American bats, such as the little brown bat and the big brown bat. These light-averse bats avoided illuminated areas, reducing their foraging activity and limiting their already restricted habitats.

The little brown bat (Myotis lucifugus) was found to be particularly sensitive to light pollution, with a significant reduction in foraging activity at 75 meters from the light source. The big brown bat (Eptesicus fuscus) was less affected, with a decrease in activity closer to the light source, at up to 25 meters away.

Furthermore, the study found that even small-scale residential lighting can drive shifts in the overall bat community composition, altering the presence of different bat species within an area. This can result in changes to the community composition up to 50 meters away from the light source.

While some bat species, such as the eastern red bat and hoary bat, do not seem to alter their behavior due to light pollution, others may be attracted to well-lit areas that lure in insects for them to prey on. However, the overall effect of light pollution is a reduction in bat activity and a disruption to their natural habits and biodiversity.

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