Reducing Light Pollution: Two Simple Solutions For Clearer Skies

Light pollution is a growing problem, with a 2023 study published in Science magazine finding that the number of stars visible in the night sky decreased by 7-10% per year from 2011 to 2022. This is due to a variety of factors, including rural and suburban development, population growth, and the increased use of powerful light sources such as LEDs. Light pollution has negative impacts on human health, wildlife, and the environment. However, there are simple solutions to reduce light pollution and mitigate these effects. Two solutions are:

1. Using motion-sensitive lighting: This ensures that lights only come on when people or objects are present, reducing the amount of wasted light emitted.

2. Using covered bulbs that face downwards: By encasing bulbs above and to the sides, light is channelled downwards to where it is needed, reducing the amount of light wasted by illuminating the sky.

Use motion-sensitive lighting

Motion-sensitive lighting is a simple yet effective way to reduce light pollution. This type of lighting is designed to be activated only when motion is detected, which means that lights are on only when needed, reducing the amount of wasted light.

Motion-sensitive lighting uses a sensor to detect movement and turn on the lights when someone or something is approaching. This can be particularly useful for street lighting, illuminating an area only when people or moving objects are present, rather than keeping the lights on all night. By using motion-sensitive lighting, we can reduce the amount of unnecessary light that is emitted, helping to minimise light pollution.

Benefits of motion-sensitive lighting:

• Reduced light pollution: The primary benefit of motion-sensitive lighting is its ability to reduce light pollution by ensuring that lights are only active when needed. This minimises the amount of artificial light that escapes into the night sky, preserving the beauty of the natural environment.
• Energy conservation: Motion-sensitive lights conserve energy by operating only when triggered by motion. This not only reduces energy costs but also contributes to environmental conservation and helps mitigate climate change by lowering energy consumption and associated emissions.
• Safety and security: Motion-sensitive lighting can enhance safety and security in public spaces. By illuminating areas only when they are in use, these lighting systems can deter potential intruders or hazards, making it easier for people to navigate their surroundings.
• Flexibility and control: Motion-sensitive lights offer flexibility in terms of customisation and control. Users can adjust the sensitivity of the motion sensors, the duration of illumination, and the brightness of the lights to suit their specific needs and the environment.

Best practices for motion-sensitive lighting:

• Placement: Ensure that motion-sensitive lights are placed in areas where they can effectively detect motion. Consider the range and coverage of the sensors and install them at appropriate heights and angles to maximise their effectiveness.
• Regular maintenance: Like any lighting system, motion-sensitive lights require regular maintenance to function optimally. Ensure that sensors are clean and free of debris or obstructions, and replace batteries or light bulbs as needed to maintain their functionality.
• Consider the environment: Take into account the surrounding environment when installing motion-sensitive lights. Avoid placing them in areas where they may be triggered by wildlife or natural movements, such as tree branches swaying in the wind, to prevent unnecessary illumination.
• Combine with other measures: For maximum effectiveness in reducing light pollution, combine motion-sensitive lighting with other strategies. Use warm-toned lighting, minimise light trespass by directing lights downward, and turn off unnecessary lights when not in use.

By adopting motion-sensitive lighting and following these guidelines, we can significantly reduce light pollution, preserving the natural beauty of the night sky while also enjoying the benefits of modern lighting technology.

Ensure bulbs are covered and face downwards

Ensuring that bulbs are covered and face downwards is an important step in reducing light pollution. This is particularly relevant for street lights and highway lighting. By facing downward, the light is directed towards the ground, where it is needed, and reduces the amount of light that escapes upwards into the sky. This method, known as 'cutting off light at the horizontal', ensures that light is used efficiently to illuminate the ground and not wasted by lighting up the sky.

To achieve this, light fixtures should be designed with an encasement above and to the sides of the bulb. This simple design feature helps to channel the light downwards, minimising the amount of wasted light. This technique can be applied to both indoor and outdoor lighting. For indoor lighting, it is also recommended to keep blinds and drapes closed at night to prevent light from escaping outside and contributing to light pollution.

The use of covered, downward-facing bulbs not only reduces light pollution but also improves visibility on the ground. This enhanced visibility can benefit motorists and pedestrians, improving safety and reducing potential hazards. Additionally, by reducing the amount of light escaping into the sky, this method can help mitigate the negative impacts of light pollution on wildlife and the environment.

It is worth noting that while this approach is effective in reducing light pollution, it should be combined with other strategies for a comprehensive solution. For example, using warm-coloured bulbs, such as low-pressure sodium (LPS) or low-colour-temperature LEDs, can further minimise light pollution. Additionally, incorporating motion sensors, timers, and dimmers can help reduce overall illumination levels and save energy.

Use low-watt bulbs

Using low-watt bulbs is a simple yet effective way to reduce light pollution. Here's why:

Energy Efficiency and Cost Savings

Low-watt bulbs, such as compact fluorescent lights (CFLs) and light-emitting diodes (LEDs), are more energy-efficient than traditional incandescent bulbs. They require less electricity to produce the same amount of light, resulting in reduced energy consumption and lower utility bills. This not only saves money for households but also reduces the environmental impact of electricity generation, as less fossil fuel needs to be burned. According to the U.S. Department of Energy, the new minimum standard for light bulbs is 45 lumens per watt, phasing out older, high-energy incandescent bulbs.

Reduced Light Pollution

Low-watt bulbs emit less light, reducing light pollution. This is especially true when compared to incandescent bulbs, which waste energy by emitting a significant amount of heat. By using low-watt bulbs, less light is scattered into the night sky, preserving the visibility of the stars and the natural darkness of the night sky. This is crucial for stargazing and astronomy enthusiasts.

Health Benefits

Opting for low-watt bulbs can also have positive effects on human health. Blue light, which is common in higher-wattage bulbs, has been linked to disruptions in circadian rhythms, leading to sleep problems. Additionally, blue light can suppress the production of melatonin, a hormone crucial for regulating sleep-wake cycles. By choosing low-watt bulbs with warmer color temperatures, we can reduce our exposure to blue light and minimize these negative health impacts.

Environmental Impact

The use of low-watt bulbs can also help protect the environment and wildlife. Artificial light at night can disrupt the behavior of animals and insects, affecting migration patterns and breeding cycles. By reducing light pollution with low-watt bulbs, we can minimize these disturbances and help preserve the natural behaviors of nocturnal creatures. This, in turn, can contribute to maintaining biodiversity and the health of ecosystems.

Longevity and Maintenance

Low-watt bulbs, such as CFLs and LEDs, tend to have longer lifespans than incandescent bulbs, reducing the need for frequent replacements. This not only saves money but also reduces the environmental impact of producing and disposing of light bulbs. With less frequent replacements, we can also minimize the hassle and potential safety risks associated with changing bulbs in hard-to-reach places.

Minimise light loss from your home

Reducing light pollution is not just a task for municipal governments. There are many ways to minimise light loss from your home and play your part in reducing light pollution.

Firstly, ensure that you are only using the lights that you need. Get into the habit of turning off lights when they are not in use, and use fewer lights when you are inside. This will also help to reduce your energy costs. If you are about to sleep and there is no activity outside your house, turn off all the lights. If you are concerned about security, you could install motion sensors, which will only turn the lights on when motion is detected.

Secondly, keep the blinds and drapes closed at night. This will prevent light from escaping your house and contributing to light pollution outdoors. It will also give you more privacy, especially if you live in close quarters such as a hotel or apartment building.

Thirdly, when using lights outside, ensure that they are downward-facing. This will help to minimise light pollution and prevent light from escaping into the sky. You can install light shields for any outdoor lighting setups to help direct the light downwards.

Finally, be mindful of the type of light bulbs you are using. The International Dark-Sky Association (IDA) recommends that only warm light sources be used for outdoor lighting. This includes low-pressure sodium (LPS), high-pressure sodium (HPS), and low-colour-temperature LEDs. Use "warm" or filtered LEDs (CCT < 3,000 K; S/P ratio < 1.2) to minimise blue emission.

Use coloured lights (e.g. yellow, red, amber)

Using coloured lights such as yellow, red, or amber can be an effective way to reduce light pollution. These colours are anti-glare and do not affect night vision, making them ideal for outdoor lighting.

Coloured lights, particularly in the amber range, are recommended by the International Dark Sky Association (IDA) and other experts for their minimal impact on the environment. Amber-coloured lights are considered the least harmful type of lighting and can aid night vision for both people and animals. This is because they minimise blue and violet spectral components, which are known to cause glare and compromise human and animal vision.

By using coloured lights, you can help reduce the negative effects of lighting at night. For example, blue-rich white light sources are known to increase glare and negatively impact the vision of motorists and pedestrians. They also have adverse effects on wildlife behaviour and reproduction, especially in cities where migratory species may be present.

When choosing coloured lights, opt for "warm" or filtered LEDs with a correlated colour temperature (CCT) of 3000 Kelvin or lower, and a scotopic/photopic ratio (S/P ratio) of 1.2 or lower. This will help to minimise blue emission, reducing its negative impact on the environment.

In addition to using coloured lights, it is important to ensure that outdoor lighting is properly designed to avoid excessive illumination in the sky. This can be achieved by using covered bulbs that direct light downwards, also known as "cutting off light at the horizontal". This ensures that light is used to illuminate the ground where it is needed, rather than contributing to sky glow.

Frequently asked questions