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Insect-friendly lighting

Sustainable and ecological outdoor lighting

Since street luminaires are operated outdoors, their light has a direct impact on flora and fauna – both in natural spaces and in the city. 

If you ask how ecological and insect-friendly lighting (LED outdoor lighting) LED outdoor lighting: „As much light as necessary, as little light as possible!“. Compared to other lighting technologies, LED luminaires are best suited to fulfil this requirement because LED light can be directed particularly well with reflectors and lenses, it can be easily switched and dimmed as required and LED luminaires are available with insect-friendly light spectra.

Risks of artificial lighting for animals and insects

Light aisles

Illuminated roads and paths can be barriers for animals. So-called light aisles cut through their habitat, which restricts their radius of action and possibly hinders their search for food. Fragmented biotopes can lead to small, isolated populations of a species and thus to disadvantages in reproduction. However, they can also harbour species compositions with unfavourable predator-prey relationships. Such a light barrier can also become a problem for fish during their spawning migration. This must be taken into account for bridge lighting, among other things.

Rhythm shift

Rhythm shifts: Lighting can cause nocturnal animals to wake later, leaving them less time to forage. This applies, for example, to light in front of the flight holes of bats, but has also been proven for certain amphibian species. In addition, songbirds were observed laying their eggs in the vicinity of streetlights earlier in the year. This can mean that the young's need for food does not start at the same time as the greatest availability of food.

The fact that these effects can be considerable becomes clear, for example, when using continuous light or when simulating daylight phases of different lengths in fish farming. The former is intended to inhibit the maturation of the reproductive organs in order to promote growth and weight gain in young fish. The latter is used to produce fish eggs and reproduce fish outside the spawning season.

The power of attraction of light

Attraction: Artificial light sources attract insects and bats in particular, but also birds. With serious consequences: Fast-flying insects are injured or killed on impact with the luminaire housing. In other cases, the animals enter the luminaire housing and die there due to heat or starvation. When insects move near bright lights, they are also easier for their predators to spot. By flying disorientated around lights, they also lose their energy reserves. As not all insect species are equally attracted to light, the balance between populations can be disturbed.

Misleading birds

Many migratory birds are travelling at night. Light sources can clearly irritate them and throw them off course. It is assumed that the reason for this is that birds can perceive their orientation aid, namely the earth's magnetic field - or more precisely the magnetic field lines - with the help of photoreceptors in the eye. These receptors are adjusted to natural light conditions and therefore to darkness at night. If bright artificial light then hits the bird's eye, this sensitive system becomes confused and disturbs the bird's orientation.

What makes insect-friendly lighting

Over-sizing is easily avoidable - light management

The principle "As much light as necessary, as little light as possible!" is one of the key conditions for insect-friendly lighting and can be fulfilled particularly well with LED post-top luminaires, as the technology allows manufacturers to fine-tune the performance classes within the luminaire series. This means that a model with the right luminous flux is available for every project-specific requirement. LED light sources can be easily switched and dimmed and are therefore ideal for adapting the light supply to lighting requirements.

Presence-dependent control

If the sensors do not detect any moving vehicles, a low dimming level is active in this area of the car park. If the sensor detects a parked vehicle, the lights in this section of the car park are switched up to full illuminance.

Travelling light

If no users are travelling along the path, a low dimming level is active. If the sensor detects a user, the luminaires in a certain section in front of the user are switched up to full illuminance and dimmed down again once the user has left the area.   

Precise light control

Light should be directed to where it is needed. Unnecessary light emissions must be consistently avoided. This is ensured by well-chosen luminaire locations on the one hand and the reflectors and lenses - i.e. the optical system - of the luminaire on the other.

Targeted light distribution for operation during the first operating hours in the evening.

Adaptive lighting in the late evening hours directs the light in a more targeted and environmentally friendly way.

A luminaire with a high indirect light component visible to insects from a large distance.

Software-supported planning

Additional anti-glare plates or tubes can be used for special project requirements. It is also helpful to use the lowest possible mounting heights, i.e. low masts. Of course, all standard specifications and visual requirements must still be met.

On request, TRILUX supports system installers with software-based lighting design that determines the optimum luminaire types and luminaire locations for the respective project.

Features of insect-friendly luminaires

Insect-friendly luminaire design

To prevent insects from burning, the surface temperature of the luminaire housing should not exceed 60 °C. A well-sealed housing prevents animals from entering the luminaire and dying from heat or starvation. Cover panes or cover troughs with a prismatic structure or made of opal materials appear as luminous surfaces visible from afar. NABU - Nature and Biodiversity Conservation Union Germany therefore recommends clear materials for the lower end of the luminaire housing.

Effect of different light colours on insects

Short-wave light in the blue and UV range is particularly attractive to many insects. LED light sources have a potential advantage here, as they generally do not emit UV light. Warm white LEDs (≤ 3,000 Kelvin) also usually have a lower proportion of short-wave light, which tends to be more insect-friendly. However, the effects can vary depending on the type and environment.

There is a need for research

It is not possible to make an explicit statement about which illuminance levels, light distributions or contrasts are likely to endanger animals and plants. Systematic research into the threat posed to individual species or species groups by artificial light has not yet been carried out. Incidentally, light emissions alone are often not responsible for the disappearance of a species at a particular location. Rather, many influencing factors interact.

Rules of insect-friendly outdoor lighting

  1. Outdoor light management with several switching levels for possible level changes (e.g. LiveLink Outdoor)
  2. Spatial illumination is reduced by using direct distribution luminaires
  3. Suitable light distribution according to the geometry
  4. Use of low light points according to surrounding building heights
  5. Wide range of different light colours (2,200 - 4,000K)
  6. Luminaires with at least an IP54 protection rating
Editors
Isabel Sabisch
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