News & Insights

The lights are too bright!

Cardno undertook a literature review of the potential effects of artificial night-light on fauna. Terrestrial species, flying species, and swimming species could be potentially affected. The Milky Way is also not visible across large parts of the urban sky.

Hutt City Council asked Cardno to undertake a review of potential effects of artificial night-light on fauna in the Lower Hutt District. This included looking at effects of night-light on birds, mammals, lizards, insects, and freshwater fish, but excluded effects on plants, humans, or marine animals except to the extent affected by light sources on land. We found that three key aspects influence how badly fauna are affected by light at night. They are:

  • how much light is being emitted,
  • what the colour of the light is,
  • and how a particular species reacts to light.

Falchi and affiliated researchers (2016) created a world atlas by calculating the likely light pollution of artificial sky luminance using new high-resolution satellite data and new precision sky brightness measurements. These data showed that the Milky Way was unlikely to be visible from urban areas in the Wellington, Hutt Valley or Porirua districts due to the amount of light emitted at night.

There are a range of light bulbs available, and the types also differ for commercial and sports illumination, and indoor and outdoor lighting. There are five main types of light[1], and they vary in energy efficiency and light output. They also differ in colour output from a warm orange tint to blue-white tint. The human eye may not see the full colour spectrum of light that is being emitted.

Animals often see in quite a different colour spectrum than humans. Some species are more attracted to lights at the blue end of the spectrum, while other species find lights at the orange end more attractive. So the type and colour of light used outdoors can affect different species.

Many of the animal species known from Lower Hutt district are active at night and therefore potentially affected by artificial outdoor illumination. Research on the effects of light on fauna is relatively limited but increasing. There is little information for many of the New Zealand fauna, or their overseas close relatives. Some of the internationally reported fauna effects of increased night-light were changes to:

  • species behaviour; e.g. different flower nectar-producing times, birds singing all night,
  • species physiology; e.g. exhaustion due to constant light, changes to the internal (circadian) clock,
  • how and when species interact with their environment; e.g. some insects flock to lights within 500 m and some birds to lights within 5 km, other species avoid brightly lit areas (including migrating fish),
  • breeding; e.g. laying eggs too early in the season, asynchrony of spawning, attracted to light rather than a mate.

Cumulatively these effects, on a wide range of species, can result in temporary or long-term consequences for biodiversity within and near an urban area, but there is a range of management options that can help reduce the effects of night-light on fauna.

[1] Incandescent, tungsten-halogen, fluorescent, light-emitting diodes (LED), and high-intensity discharge (HID).

For more information contact:

Astrid van Meeuwen-Dijkgraaf
Terrestrial Ecology Lead - New Zealand
Phone: +64 4 566 0922


Commonwealth of Australia 2020. National Light Pollution Guidelines for Wildlife Including Marine Turtles, Seabirds and Migratory Shorebirds. Report produced for the Department of the Environment and Energy. 107pp.

Falchi, F, Cinzano, P, Duriscoe, D, Kyba, CCM, Elvidge, CD, Baugh, K, and Furgoni, R (2016a). The new world atlas of artificial night sky brightness. Science Advances 2(6), e1600377–e1600377.

Falchi, F, Cinzano, P, Duriscoe, D, Kyba, CCM, Elvidge, CD, Baugh, K, and Furgoni, R (2016b). Supplement to the new world atlas of artificial night sky brightness, GFZ Data Services. Retrieved from