Written by Neil Parslow
The Growing Issue of Light Pollution: How Thoughtful Lighting Design Can Make a Difference
Light pollution is an ever-growing problem affecting cities, towns, and rural areas around the world. While advancements in LED technology have led to greater energy efficiency and reduced fossil fuel consumption, there is an under-publicised downside: certain LED products negatively impact both human health and the environment.
The Impact of LED Lighting
Commercial and domestic LED lighting has been in use for over 15 years, with manufacturers continuously improving efficiency. While this is seen as progress over incandescent lighting, the reality is that poorly designed and misapplied LED lighting is contributing to increased light pollution.
DarkSky International, a leading non-profit organisation dedicated to combating light pollution, works to reduce its harmful effects on both people and wildlife. The main contributors to excessive artificial light include streetlights, electronic advertising boards, car parks, sports facilities, commercial greenhouses, and factories.
For instance, streetlights often use high colour temperatures (between 4000K and 6500K) with varying light intensities, ranging from 3000 lumens to 100,000 lumens per fixture. Another significant source is high-powered LED floodlights, widely used for security and industrial purposes. These lights, often exceeding 7000K, typically have a broad 120° beam spread but are frequently misaligned, exacerbating light pollution.
The Negative Effects of Excessive Lighting
Excessive and improperly directed light can cause veiling luminance, which leads to disability glare, making environments less safe rather than more secure. Poorly designed lighting, especially floodlights, can create unnecessary hazards by masking dangers rather than illuminating them. Instead, effective landscape lighting design can provide safer and more aesthetically pleasing solutions while minimising glare and light spill.
The human eye is highly adaptive to low light levels, so reducing high-contrast lighting through thoughtful design is crucial. Studies have shown that intense, cool-coloured streetlights near trees can cause growth anomalies and premature leaf drop, ultimately leading to long-term damage or tree death.
Responsible Outdoor Lighting Solutions
Despite these concerns, proper landscape lighting design can be implemented in a way that enhances outdoor spaces without contributing to light pollution. Accessories such as glare shields, hex louvres, and internal filters help control light spill and reduce unwanted glare. Well-designed landscape lighting uses fixtures with wattages between 0.5W and 6W (producing around 30 to 600 lumens), significantly lower than streetlights.
Optimal colour temperatures for garden and landscape lighting range from 2700K to 3000K, which provide natural illumination while preserving the environment. Many leading designers, including myself, prefer 3000K, as it highlights tree and shrub foliage in the most aesthetically pleasing way across all seasons.
A Real-World Example: Foxholes Care Home Lighting Project
Starting in spring 2025, Foxholes Care Home in Hitchin, Hertfordshire, will open its newly landscaped front gardens each night for visitors to experience well-executed, low-impact lighting design. The project incorporates 2700K and 3000K lighting through carefully positioned uplighting and downlighting. After 10 PM, a Dark Sky setting will be activated, turning off most lights via timed controllers to minimise disruption to wildlife. No booking will be required—visitors are welcome to see firsthand how good lighting design can enhance an area while protecting the night environment.
The Five Principles for Outdoor Lighting (DarkSky International)
- Useful – Every light should serve a clear purpose within the overall composition.
- Targeted – Lights should be accurately aimed to prevent unnecessary spill.
- Low Level – Light outputs can be as little as 30 lumens or lower.
- Controlled – Use dimmers, sensors, timers, or simply switch lights off when not needed.
- Warm Colour Temperature – 2700K to 3000K is ideal for landscape lighting.
