Reducing Light Pollution: Global Strategies For Dark Skies

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. It is caused by artificial light sources such as street lamps, houses, and skyscrapers. Light pollution has several negative consequences, including harm to wildlife, a hindrance to research on climate change, and adverse effects on human health. It also interferes with the aesthetic beauty of the environment. To reduce light pollution, individuals, institutions, and governments should take various actions, including changing light bulbs and fixtures, adopting measures to reduce light trespass and glare, using motion sensors and timers, and supporting initiatives for dark sky conservation.

Reduce decorative lighting

Reducing decorative lighting is a key strategy in the fight against light pollution. Here are some ways to do so:

Reduce the Amount of Decorative Lighting

Decorative lighting is often used excessively during festivities and celebrations, brightening the night sky. To reduce light pollution, it is recommended to minimise the use of such lighting and opt for environmentally friendly candles instead. This not only helps conserve energy but also reduces the amount of light pollution.

Use Timers and Motion Sensors

Instead of keeping decorative lights on all day and night, consider installing motion sensors or timers. Motion sensors will only activate the lights when motion is detected, reducing energy consumption and light pollution. Timers can be set to turn lights on and off at specific times, ensuring they are only on when needed.

Choose the Right Type of Lights

When using decorative lighting, opt for warm-coloured bulbs or LEDs with a colour temperature of 3000 Kelvin or lower. Avoid blue-rich white light sources, as they increase glare and have a larger geographic reach, worsening sky glow. Warm-coloured lights, such as low-pressure sodium (LPS) or low-colour-temperature LEDs, minimise blue emission and reduce light pollution.

Direct Lights Downwards

Another way to reduce light pollution from decorative lighting is to ensure the lights are directed downwards. Using shades, covers, or shields can help focus the light on the intended area, reducing light spillover and upward light pollution. This can be achieved by angling the lights downwards or using fixtures designed to minimise upward light emission.

Turn Off Unnecessary Lights

A simple yet effective way to reduce light pollution is to turn off unnecessary lights. Only use decorative lighting when needed and consider the duration of their use. By being mindful of our light usage, we can significantly reduce light pollution and our impact on the environment.

Use covered bulbs that face downwards

Light pollution is a growing problem, caused by artificial light sources such as street lamps, houses, and skyscrapers. It obscures the night sky, harms wildlife, and hinders research on climate change. However, there are ways to reduce light pollution, such as using covered bulbs that face downwards.

Covered Bulbs That Face Downwards

Using covered bulbs that face downwards is an effective way to reduce light pollution. This method can be applied to street lights and highway lighting. By using covered bulbs, the amount of light illuminating the sky is reduced, thus minimising light pollution.

To further reduce the impact on the night sky, it is recommended to use warm-coloured bulbs with lower colour temperatures. Specifically, the International Dark-Sky Association (IDA) suggests the use of Low-pressure Sodium (LPS), High-pressure Sodium (HPS), and low-colour-temperature LEDs. Additionally, "warm" or filtered LEDs with a correlated colour temperature (CCT) of less than 3000 Kelvin (K) and an S/P ratio of less than 1.2 are ideal for minimising blue emission.

Other Ways to Reduce Light Pollution

In addition to using covered bulbs that face downwards, there are several other ways to minimise light pollution:

• Reduce the use of decorative lighting during festive seasons.
• Minimise the use of lights when not needed, such as turning off unnecessary indoor lighting in empty buildings.
• Use automated timers and systems to turn off street and highway lights during the day or when the moon is bright.
• Refrain from light trespassing, which is directing bright outdoor lights towards neighbouring residences.
• Use glare-free lighting for vehicles at night to avoid disturbing wildlife and compromising safety.
• Avoid using blue lights at night, as they increase glare and negatively impact human and wildlife vision.
• Support initiatives for wilderness protection, such as keeping exterior lights off to maintain the natural cycles of nocturnal creatures.

By implementing these strategies, we can collectively reduce light pollution and restore our connection to the night sky while also minimising harm to wildlife and the environment.

Minimise the use of lights

Minimising the use of lights is one of the most effective ways to reduce light pollution. This can be achieved through a combination of behavioural changes and the adoption of new technologies.

Firstly, it is important to switch off unnecessary lights, especially when going to sleep or when there is no activity outside the house. This simple action can significantly reduce light pollution and is also cost-effective, as it lowers energy consumption.

In addition to behavioural changes, technological advancements offer further opportunities to minimise light usage. For example, the use of automated street lights with timers can ensure that streetlights are only active when needed, such as during the night or in low-light conditions. This not only reduces light pollution but also conserves energy.

Another innovative solution is the use of motion sensors for outdoor security lighting. Motion sensors activate lights only when motion is detected, minimising the amount of light emitted into the night sky and reducing energy costs.

To further decrease light pollution, it is recommended to use covered bulbs that emit light downwards. This downward-facing lighting reduces the amount of light reflected upwards, minimising light pollution and improving visibility on roads and streets.

Lastly, individuals can contribute by reducing the use of decorative lighting during festive seasons. Instead, environmentally friendly candles can be used, which not only lessen the impact on the environment but also conserve energy.

By combining these strategies, we can effectively minimise the use of lights and play our part in reducing light pollution.

Use motion sensors on outdoor lights

Light pollution is a growing problem, with the world's night sky more than doubling in artificial brightness between 2011 and 2022. It harms wildlife, blocks our view of the stars, and hinders research on climate change.

One way to reduce light pollution is to use motion sensors on outdoor lights. Here's how:

Motion sensors detect movement and trigger lights to turn on. The most common types are passive infrared (PIR) sensors, which detect infrared radiation from warm objects, and microwave sensors, which emit microwave pulses and measure reflections to detect movement. Dual technology sensors combine both PIR and microwave sensors for increased accuracy. The effectiveness of motion sensors depends on their detection range and sensitivity. Factors affecting these include sensor type, quality, and light design. Proper placement is also key, ensuring a clear line of sight and no obstructions.

Benefits of motion sensors

Motion sensors offer a range of benefits:

• Security: They act as a powerful deterrent to intruders by suddenly illuminating dark areas, startling anyone approaching your property. Research has shown that well-lit areas are less likely to be targeted by criminals.
• Energy efficiency: Motion sensors only activate lights when needed, reducing energy consumption and utility costs. This also makes them an eco-friendly choice, lowering your carbon footprint.
• Convenience: Motion sensors eliminate the need for manual operation, automatically illuminating pathways, driveways, and entrances when you need them lit. They also ensure you never forget to turn lights on or off, enhancing safety and convenience.

Choosing motion sensors

When selecting motion sensors, consider the following:

• Sensor range and detection angle: Choose sensors with an appropriate range and angle to cover the area you want to monitor. For larger areas, opt for a longer range and wider angle.
• Light brightness: Select the right lumen output for the space. For example, driveways typically need 1,500-2,000 lumens, while pathways require 100-300 lumens.
• Durability and weather resistance: Look for sensors designed for outdoor use, with features protecting against harsh weather conditions. An Ingress Protection (IP) rating of IP65 or higher is recommended.

Best practices for installation

To maximize the effectiveness of motion sensors, follow these installation tips:

• Height and placement: Install sensors at the recommended height, usually between 6 to 10 feet above the ground, to detect movement effectively while minimizing false triggers. Strategically place them at entry points, along pathways, and around the property perimeter.
• Clear line of sight: Ensure sensors have a clear and unobstructed view, avoiding walls, fences, or landscaping features that may block their detection.
• Avoid reflective surfaces: Don't position sensors too close to reflective surfaces, as this can interfere with their accuracy.

By adopting motion sensors for outdoor lighting, we can play our part in reducing light pollution, preserving the night sky, and protecting our environment.

Avoid blue lights at night

Blue light at night has a wide range of negative effects on both human health and wildlife. Firstly, blue light can disrupt the body's biological clock, known as the circadian rhythm, which can lead to sleep issues and potentially contribute to the development of diseases such as cancer, diabetes, heart disease, and obesity. Research by Harvard researchers found that blue light suppressed melatonin for twice as long as green light and shifted circadian rhythms by twice as much.

Blue-rich white light sources also increase glare and compromise human vision, especially for older people. These lights can create road safety issues for motorists and pedestrians. In addition, blue light at night has been shown to negatively impact wildlife behaviour and reproduction, particularly in cities that migratory species often pass through.

To avoid the negative consequences of blue light, there are several actions that can be taken:

• Use dim red lights for night lights as red light is less likely to interfere with circadian rhythm and melatonin secretion.
• Avoid looking at bright screens 2-3 hours before bedtime.
• If you work night shifts or use a lot of electronic devices at night, consider wearing blue-blocking glasses or using apps that filter blue/green wavelengths.
• Expose yourself to ample bright light during the day to improve sleep quality and boost your mood and alertness during the day.
• Use "warm-white" or filtered LEDs (CCT < 3000 K; S/P ratio < 1.2) to minimize blue light exposure.

Frequently asked questions