When planning, designing and procuring new lighting for the public realm, we think about price, energy usage, ambience and style. Is the environmental impact on your checklist? Are your lighting choices informed by the negative effect that the scheme could have on the plants, trees, birds and insects that populate the space?
We all need to do our bit to protect and enhance the biodiversity of our outdoor spaces, and we can achieve this by making relatively simple adjustments to lighting choices and usage. Before we get on to the solutions though, let’s have a look at why some outdoor lighting is causing problems.
Too much light to function
Just as humans rely on night and day to manage our circadian rhythms and behaviours, animals and plants also rely on natural light and dark cycles to regulate their behaviours and support important processes. But when outdoor spaces are lit by artificial light sources, and in particular LED sources that emit excessive blue light, this can negatively impact wildlife.
As blue light suppresses the production of the hormone melatonin (which helps humans and animals to sleep), the circadian rhythms of affected nocturnal animals are disrupted, and consequently so is their sleep. Their bodies have less time to rest and repair themselves, their immune systems are compromised and healthy reproduction is put at risk.
Nocturnal animals, for example bats and almost all amphibians, are very sensitive to blue light. They may avoid well-lit but otherwise suitable habitats, upsetting the predator/prey balance, and species that are afraid of light will hide rather than hunt, missing out on good food supplies.
Birds can be affected too. If artificial lighting overwhelms natural lighting sources, migrating birds can be thrown off course and fly until they collapse from exhaustion. In addition, light pollution reduces the area of suitable hunting habitat for owls, which use low level moonlight and starlight to hunt at night.
David Attenborough has given a stark warning about the decline of the world’s insect population: “If the invertebrates were to disappear, the world’s ecosystems would collapse.” A third of our entire food supply depends on natural pollinators, yet artificial night-time lighting continues to contribute to their decline.
Some moths, for example, are nocturnal pollinators, using moonlight to orientate themselves. They are therefore drawn to artificial lighting, which exposes them to unnaturally high rates of predation and leads to disrupted feeding and reproduction patterns. In fact, the UK’s nocturnal moth population has declined by a third over the last 50 years.
Research has also found that daytime pollinators such as bees and butterflies will pollinate significantly less during the day, if they have been exposed to artificial light during the night.
Plants and trees also rely on light and dark cycles to grow and need darkness to regenerate and develop. Urban trees have been found to die earlier than those in rural areas, in part because they don’t get enough darkness. In autumn, trees may keep their leaves for longer in the parts that are close to artificial sources of light, which can cause frost damage and harm photosynthetic tissue.
Thankfully, there are laws in place to reduce light pollution and to help protect at-risk nocturnal animals such as bats. In approaching any urban landscape design project, we encourage architects to prioritise the environmental impact of their lighting choices, and to explore options that will help to protect nature.
The first question to ask is simply: is external lighting necessary? In some cases, once this is really considered, the answer is no, and this is by far the easiest way to improve the environmental credentials of a project.
However, in most urban settings some form of lighting is needed and so we look to improved lighting design and control for solutions.
Lighting schemes should be designed in accordance with British Standard requirements and the ILP Guidelines for the Reduction of Obtrusive light. You can explore options such as luminaires with zero ULOR (Upward Light Output Ratio) for lighting roads and footpaths, and specify luminaires incorporating integral pre-programmed LED drivers that allow for part-night dimming and switching.
When specifying luminaires, choose those with a CCT (Correlated Colour Temperature) of 3000k or lower. For inspiration, you might like to look at the lighting concepts used at Ironbridge Gorge in Telford, Piece Hall in Halifax and Whitfield Gardens, off Tottenham Court Road in London.
We offer specialist CPD sessions on lighting and ecology, in which we delve far deeper into the issues surrounding outdoor lighting schemes and, of course, the solutions. If you would like more information about this, please get in touch with our Business Development Manager, Steve Ellis on: email@example.com.