Red Light: Reducing Light Pollution

Light pollution, caused by unwanted, inappropriate, or excessive artificial lighting, affects 83% of the world's population and 23% of the world's land area. It has been linked to negative impacts on human health, ecosystems, and biodiversity. To combat this, some countries in Europe have adopted red light installations in protected areas or near sensitive species, as red light is hypothesized to induce less sky glow and glare, and has a reduced impact on insects and bats. While red light may be a potential solution to light pollution, there are also concerns about its effects on human safety and visual performance, as well as its potential ecological consequences on diverse species.

Red light is less attractive to insects

Light pollution, caused by unwanted, inappropriate, or excessive artificial lighting, has impacted ecosystems and human circadian rhythms. To mitigate light pollution, red light has been promoted as a possible solution. Red light has a longer wavelength and is less attractive to insects compared to other colours of light.

Insects are attracted to light sources for navigation, orientation, and finding mates. Light with shorter wavelengths, such as blue and ultraviolet (UV) light, scatters less in the atmosphere, making it more visible to insects from longer distances. Insects perceive light in the 300-650 nanometer range but prefer light between 300-420 nanometers, which includes UV light. As red light has a longer wavelength, it is less appealing to insects.

Pest management professionals (PMPs) have advised customers to use yellow bulbs instead of white incandescent or fluorescent bulbs to reduce the attraction to night-flying insects. Red bulbs are even less attractive to insects than yellow bulbs, but they provide little visible light to humans and carry a social stigma. Additionally, red light has poor colour quality and low luminous efficacy of radiation, requiring higher input power for the same light output.

While red light may help reduce the attraction of insects, its effectiveness in mitigating ecological impacts is uncertain. Further research is needed to balance design functionality and ecological impacts before the widespread adoption of red lighting outdoors.

Red light reduces sky glow

Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It has been estimated that 83% of the world's people live under light-polluted skies, and 23% of the world's land area is affected by sky glow.

The widespread use of electric lighting has revolutionized society but also brought unintended consequences, such as light pollution, which impacts ecosystems and human circadian rhythms. To address this issue, researchers have explored the use of red light as a potential solution.

Red light has been promoted as a measure to mitigate light pollution, particularly in outdoor settings. Light at longer wavelengths, which is perceived as red by most humans, scatters less in the atmosphere compared to light of other wavelengths, potentially reducing sky glow. This makes red light a desirable option for reducing light pollution.

The use of red light in outdoor installations aims to minimize the impact of electric lighting on the nocturnal environment, with a specific focus on mitigating the effects on bats and insects. Red light is hypothesized to induce less sky glow and glare, making it a potentially effective approach for reducing light pollution. It also has a reduced impact on insects as they are less attracted to lights with a lower color temperature.

However, it is important to consider the potential ecological consequences and challenges in lighting design functionality. While some bat species are less impacted by red lights, other species exhibit varying behavioral responses, indicating that the benefits may be specific to certain species. Additionally, red light has poor color quality and low luminous efficacy, which can impact human visual performance and safety.

Overall, while red light shows promise in reducing sky glow and mitigating light pollution, further examination of its ecological consequences and impact on human safety is necessary before widespread adoption.

Red light preserves human night vision

Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It has been estimated that 83% of the world's population experiences light-polluted skies, and this figure is only expected to increase.

One proposed solution to this issue is the use of red light in outdoor settings. Red light has been promoted as a measure to mitigate light pollution, particularly in Europe. This is because light at longer wavelengths, which is perceived as red by most humans, scatters less in the atmosphere compared to light of other wavelengths, potentially reducing skyglow.

Red light is also believed to preserve human night vision. This is because red light does not cause the human eye pupil to shrink to the same degree as bluish or white light. As a result, red light helps preserve peripheral vision better than white light, as the eye does not adjust as much. Furthermore, human eyes adjust faster to red light than white light when transitioning from darkness to light.

However, it is important to note that red light has some drawbacks. For example, red light has poor luminous efficacy, and it can be challenging to identify objects, including faces, under narrow-band red light. Additionally, some bat species exhibit varied behavioral responses to red lights, indicating that the benefits may be species-specific.

While red light may help reduce light pollution and preserve night vision, further research is needed to fully understand its ecological consequences and impacts on different species.

Red light is safer for some bat species

Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It has been estimated that 83% of the world's population experiences light-polluted skies, and the number is only increasing. Light pollution has several adverse effects, including impacts on human health, ecosystems, and biodiversity.

To mitigate light pollution, researchers have suggested using red light in outdoor settings. This is because light at longer wavelengths, which is perceived as red by most humans, scatters less in the atmosphere compared to light of other wavelengths, potentially reducing skyglow. In addition, red light produces less glare and has a reduced impact on insects.

While red light may be a solution to reducing light pollution, it may not be the best option for all species. For example, soybean farmers have found that even a small amount of red light at night can reduce crop yield by 20 to 40 percent due to delayed flowering and ripening.

When it comes to bats, the effects of red light are mixed. Some studies have found that certain bat species are attracted to red light during their migration, which could be dangerous for them. However, other studies have found that red light has no effect on the activity of slow-flying, light-shy bats, and may even result in higher activity for some species compared to white or green lighting.

Overall, while red light may be safer for some bat species, more research is needed to fully understand the impact of red light on different bat species and their migration patterns.

Red light is better for stargazing

Light pollution is the presence of any unwanted, inappropriate, or excessive artificial lighting. It has been estimated that 83% of the world's population lives under light-polluted skies, and the area affected by artificial illumination continues to increase.

One way to mitigate light pollution is to adjust the type of lights used, so the light waves emitted are less likely to cause severe light pollution. Mercury, metal halide, and first-generation blue-light LED road luminaires are much more polluting than sodium lamps, as the Earth's atmosphere scatters and transmits blue light better than yellow or red light.

Red light has been promoted as a measure to mitigate light pollution. Light at longer wavelengths, which is perceived as red by most humans, scatters less in the atmosphere compared to light of other wavelengths, potentially reducing skyglow. Red light is also hypothesised to induce less sky glow and glare, along with a reduced impact on insects and bats in comparison to white light. This makes it a potentially effective approach for mitigating light pollution.

Red light headlamps, for example, will create less light pollution than white light and make it easier to see stars. When transitioning from darkness to light, human eyes adjust faster to red light, and red light also helps preserve peripheral vision better than white light.

However, it is important to note that red light has an innately low luminous efficacy of radiation due to its mismatch with the photopic and scotopic spectral sensitivity functions, resulting in an increase in required input power for the same light output. There is also a need for further examination of the potential ecological consequences of red light, as there is currently insufficient scientific understanding of its impact on diverse species.

In conclusion, while red light may be better for stargazing due to its reduced impact on light pollution, there are also challenges and potential risks associated with its use that need to be carefully considered.

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