Use ‘warmer’ (red/yellow) lighting rather than other lighting colours

Supporting evidence from individual studies

1. A replicated, paired, controlled study in 1997 in three sites in a rural built-up area in Rhineland-Palatinate, Germany (Eisenbeis & Hassel 2000) found that yellow lights with a lower intensity attracted fewer individual moths than broader spectrum lights with a higher intensity. Under yellow, lower intensity lights (high-pressure sodium ellipsoid lamps, HSE), the number of moths caught (2–8 individuals/trap/day) was less than the number caught under lights with a broader range of visible and ultra-violet (UV) light at a higher intensity (high-pressure mercury-vapour lamp, HME: 8–28 individuals/trap/day; high-pressure sodium-xenon lamp in tube form, HSXT: 8–25 individuals/trap/day), but higher than at the trap with no light (0 individuals/trap/day). At each of three sites, three different light types (HSE: 50–70 W, yellow light with very little UV light; HME: 80 W, visible and UV light; HSXT: 80 W, visible and UV light) were compared to a control without light. From May–September 1997, flying insects (including moths) were sampled for 60 nights using flight eclector traps installed below each lamp.

   Study and other actions tested

   Referenced paper

   Eisenbeis G. & Hassel F. (2000) Attraction of nocturnal insects to street lights: A study of municipal lighting systems in a rural area of Rheinhessen (Germany). Natur und Landschaft: Zeitschrift fur Naturschutz und Landschaftspflege, 75, 145-156.

2. A replicated, controlled study in 2009 in a wet heathland in Noord Brabant, the Netherlands (van Langevelde et al. 2011) found that light traps with longer wavelength (warmer) bulbs attracted fewer moths and fewer species than those with shorter wavelength (cooler) bulbs. There was no significant difference in the number of moths found in traps with bulbs with wavelengths of 618 nm (average abundance: 1.3), 617 nm (average: 1.1), 597 nm (average: 3.0), 554 nm (average: 2.5) and 534 nm (average: 5.8), but fewer moths were found in these traps than ones with bulbs with a wavelength of 382 nm (average: 13.2). Additionally, lower species richness of moths was found in traps with bulbs with wavelengths at 618 nm (average: 0.9 species) or 617 nm (average: 1.1) than those with 534 nm (average: 4.1) and 382 nm (average: 6.7) bulbs, but there was no significant difference between 618 nm, 617 nm, 597 nm (average: 1.9) and 554 nm (average: 1.9) bulbs. See paper for abundance and species richness of individual types of butterfly. Twice weekly between 12 July and 25 August 2009, eighteen Heath’s light traps with 6 Watt T5 fluorescent bulbs were operated at night in a 2.3 ha area of wet heathland. Each used one of six types of bulbs with differing average wavelengths (replicated three times): actinic (382 nm), green phosphor (534 nm), warm white (554 nm), white phosphor (597 nm), and red phosphor either with (618 nm) or without white phosphor (617 nm). Traps were checked for moths one hour after sunrise after each trapping night.

   Study and other actions tested

   Referenced paper

   van Langevelde F., Ettema J.A., Donners M., WallisDeVries M.F. & Groenendijk D. (2011) Effect of spectral composition of artificial light on the attraction of moths. Biological Conservation, 144, 2274-2281.

3. A replicated, paired, controlled study in 2011–2013 in 15 churches in Slovenia (Verovnik et al. 2015) found that yellow filtered lights attracted fewer individuals and species of moths than blue filtered lights or conventional lighting. On church walls illuminated with yellow light, both the abundance (12 individuals/year) and species richness of moths (10 species/year) were lower than on walls illuminated with blue light (abundance: 20 individuals/year; richness: 15 species/year) or conventional lighting (abundance: 73 individuals/year; richness: 42 species/year). Fifteen churches in dark, rural areas were grouped into adjacent triplets, and illuminated in one of three ways: blue or yellow metal halide lamps, or the existing light (metal halide or sodium vapour, 70–400 W). Experimental lamps were 70 or 150 W, had custom-made filters to remove wavelengths shorter than 400 nm (blue) or 470 nm (yellow), and blinds to prevent the scattering of light away from the building. The illumination used on each church was rotated within each triplet each year. From May–September 2011–2013, moths were counted for 45 minutes six times/year within a 10 × 3 m area of wall on each church. Churches within a triplet were surveyed on the same night.

   Study and other actions tested

   Referenced paper

   Verovnik R., Fiser Z. & Zaksek V. (2015) How to reduce the impact of artificial lighting on moths: A case study on cultural heritage sites in Slovenia. Journal for Nature Conservation, 28, 105-111.

4. A replicated, randomized, paired, controlled study in 2012 in a laboratory in the Netherlands (van Langevelde et al. 2017) found that four species of moth spent more time feeding under red light than under white or green lights, but less time than when they were in full darkness. Moths were more likely to feed under red light (5–14% of observations) than under white (4–11% of observations) or green (2–8% of observations) lights, but still fed less than in dark conditions (17–34% of observations). Forty compartments (30 × 25 cm, 60-cm-deep), arranged in 10 blocks, were randomly assigned to four light treatments: red, white, green or no light. A 1 W Deco-LED lamp above each compartment was mechanically filtered to the correct wavelength, and covered with layers of cotton to diffuse the light. Light was applied at 15 lux. On three nights in August–September 2012, one moth was placed in each compartment. Each night, 20 compartments contained captive-bred cabbage moth Mamestra brassicae of the same age, and 20 contained either straw dot Rivula sericealis, small fan-footed wave Idaea biselata, or common marbled carpet Dysstroma truncata (one night/species), caught from the wild the previous night using light traps placed in mixed forest. All moths were starved for one day before the experiment. Moths were provided with a 1:10 sugar-water soaked piece of cotton wool, and recorded as feeding or not feeding 10 times/hour for six hours.

   Study and other actions tested

   Referenced paper

   van Langevelde F., van Grunsven R.H.A., Veenendaal E.M. & Fijen T.P.M. (2017) Artificial night lighting inhibits feeding in moths. Biology Letters, 13, 20160874.

5. A replicated, randomized, paired, controlled study in 2014 in 12 woodland edges and hedgerows in southern England, UK (Wakefield et al. 2018) found that yellow high-pressure sodium (HPS) and light-emitting diode (LED) street lights caught fewer moths than broad spectrum metal halide lights, and HPS lights caught a lower diversity of insects (including moths) than LED or metal halide lights. The total number of moths caught by HPS (0–8 individuals/light) and LED lights (2–9 individuals/light) was lower than the number caught by metal halide lights (4–55 individuals/light). The diversity of all insects caught by HPS lights (32 families) was lower than the diversity caught by LED (49 families) and metal halide lights (69 families). At each of 12 sites, >100 m from existing artificial lighting, three lights were placed on 5-m-high tripods, 32–35 m apart, along a woodland edge or hedgerow (>170 m long). Three common street light designs were used: high-pressure sodium (50 W), LED (2 × 8 arrays) and metal halide (45 W), housed in matching cases. From July–September 2014, insects were collected overnight using flight intercept traps hung 20 cm below each light on one night/site.

   Study and other actions tested

   Referenced paper

   Wakefield A., Broyles M., Stone E.L., Harris S. & Jones G. (2018) Quantifying the attractiveness of broad-spectrum street lights to aerial nocturnal insects. Journal of Applied Ecology, 55, 714-722.