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How damaging is artificial lighting to the environment? Landscaping Solutions MD Ben West considers the impact.

Artificial Lighting

Artificial light can adversely impact the behaviour of birds.

We don’t have lighting in our garden. The generosity of the local borough council is such that all the light we need, and pools more, is gathered from an adjacent lamp post. Indeed ‘light trespass’ from this single luminaire infuses evening al fresco dining with all the charm of a Gestapo interrogation. The offending street lamp has recently been limited to operation from dusk until midnight, presumably as a cost cutting measure but possibly also as a response to emerging evidence of the negative effects of artificial light on the environment.

Recent studies, particularly those undertaken by the Environment and Sustainability Institute at the University of Exeter, have revealed artificial light to be adversely impacting the behaviour of a much wider range of species than myself and the missus. Birds are particularly affected with physical reproduction traits and behaviours being modified. Bird movements are also being disrupted, along with those of bats and fish, as navigational ‘signposts’ such as starlight, moonlight and diffuse natural light in the atmosphere are obscured or obliterated by ‘Skyglow’ from artificial light. This phenomena is observable many miles from source, can be equal to or exceed light intensities produced by moonlight and sufficient to mask natural lunar light cycles.

Light pollution is a relatively new phenomenon so the long term effects on biodiversity are unknown. However, the short term effects are obvious; leave a window open on a summer’s evening and it’s clear that artificial light has an effect on night flying insects such as moths. Is there a link between the reported declines in moth numbers over the past thirty years and the increase in artificial lighting during the same period? It’s too early to answer questions like these definitively but it’s easy to test the hypothesis; switch out the lights and the problem disappears. Knowing the detrimental effects on wildlife, can we continue to freely prescribe lighting in our design work? Maybe it’s time for a more measured approach. Let’s look at the facts;

The relative impact of different types of lighting depends on where they are on the spectrum. Different kinds of lamp emit light over a distinctive range of wavelengths. Light becomes more environmentally impactful in the following ways;

a) As it becomes broader on the spectrum (or ‘whiter’).

b) As the ratio of blue to red emissions increases.

c) With increased emissions in the UV (ultraviolet) range.

The broader the spectrum the more overlap with the sensitivity of biological systems. Lighting toward the red end of the spectrum is generally thought to be less impactful to the environment though this also has a bearing on the ability of birds to migrate and has an effect on plant physiology.

Light-emitting diode (LED) lighting systems require lower wattage than traditional light sources and produce lower radiant heat for the same light output. They have a longer working life and allow easy light level manipulation. Unfortunately they utilise white light which is disruptive to natural systems and the blue component is disruptive to human circadian rhythms.

So what should we be doing as environmentally conscious professionals?

- Maintain naturally unlit areas wherever possible.

- Specify light only where there is clear, sufficient and necessary human benefit. - Provide barriers to ‘light trespass’ such as covers or hoods, walls, screens and evergreen hedges.

- Ensure lighting is switched on only when needed by utilising motion control

- Disseminate knowledge to clients to raise awareness.

- Use LED lights on as dim a setting as possible.

- Avoid use of white and blue lights and fittings which emit UV light.