A tree in the light of a sodium vapour lamp

Artificial light can have different effects on animal and plant species.

 

With regard to numerous insects, birds, amphibians, reptiles, fish, crustaceans, mammals and plants, we have scientific proof of the impacts of artificial light.

 

Night-time Illumination is a problem for animals that are active by day and are disturbed in their rest at night. The same applies to nocturnal animals, which depend on the dark to live a natural life. About thirty percent of all vertebrates and more than sixty percent of invertebrates are active during the night (Hölker et al. in Leibniz-Gemeinschaft, 2009).

 

The effect of light on organisms depends above all on its spectral composition and luminous intensity.

 

Animal species can be affected in the following ways:

  • Temporary blinding and disorientation
  • Disturbed or restricted foraging
  • Changes in predator-prey relations
  • Disturbed social interaction (development and reproduction)
  • Restricted radius of action (barrier effect, displacement)
  • Disturbed rest periods

http://wua-wien.at/home/naturschutz-und-stadtoekologie/weiterfuehrende...

http://www.helldunkel.ch/

 

 

Illuminated screen

Nocturnal insects

 

Nocturnal insects use the light emitted from the celestial bodies for orientation. They mainly have maximum vision in the ultraviolet portion of the spectrum, which is invisible to human beings.

 

Such animals are dazzled by artificial light sources and lose their sense of orientation. In clear weather this can happen at distances of up to 700 meters. They fly automatically to the light source and circle it until they die of exhaustion or burns. Such situations deprive billions of insects of their habitats, including some that are classified as threatened or endangered species.

 

For more information on the the power of attraction exercised on insects by various light sources, go to Projects >>

 

Moths are members of the Lepidoptera order. Many members of this thoroughly researched group of insects are well adapted to specific habitats. more >>

 

PDF (Buglife, A Review of the Impact of Artificial Light on Invertebrates)

 

 

Skybeamer

Migrant birds

 

About two thirds of all migrant birds fly by night. "For birds, the starry night sky is like a compass," says Gerald Pfiffinger, Executive Director of Bird Life Österreich.

 

In bad weather especially, the birds fly at lower altitudes, and powerful point light sources and large illuminated areas can cause problems of orientation. After hours of disorientated flight, they die from exhaustion or collisions with illuminated objects (Hotz & Bontadina, 2007). Cases recorded in Germany, Switzerland and other countries provide evidence of the death of thousands of birds of passage during the main periods of migration from August to November and March to May.

 

For more information on ornithological observations of the illuminated Post Tower in Bonn, go to Light Blight >>

 

http://www.flap.org/

 

 

Brown long-eared bat (Plecotus auritus)

Bats

 

If the bats’ exit holes are illuminated, they will not fly until later in the night. That means the bats have less time to hunt for food.

 

Cases have been reported of bats abandoning their nests following installation of a lighting system and of higher mortality rates among their young caused by illuminating the public space for festivals (Hotz & Bontadina, 2007).

 

 

Common toad (Bufo bufo)

Amphibians

 

Where artificial lighting is used, many amphibians leave their hiding places later in the night and thus have less time to find the food they need.

 

As soon as their eyes have become adjusted to the night light, the animals are attracted by it. That actually makes the hunt easier for them, but it also increases the risk that the amphibians themselves will be preyed on.

 

Many types of frog only mate when the light is very weak, or they do not produce their mating call in the presence of light. In such cases, artificial light is a threat to reproduction (Hotz & Bontadina, 2007).

 

 

Sea turtles

Sea turtles

 

Artificial light sources located near beaches can cause problems of orientation for freshly hatched turtles especially.

 

They hatch out at night when the temperatures are lower. When they emerge from the sand, they have to find their way straight to the sea. For that purpose they make use of local light stimuli; the hatchlings move down the beach in the direction of the lighter surface of the sea, in which the light of the celestial bodies is reflected. Street lighting and luminaires used for indoor and outdoor lighting for hotels and residential buildings along the coast can disorient the hatchlings so that they move inland, where they are run over by vehicles or die of exhaustion (Borgwardt & Tucker in Posch, Freyhoff & Uhlmann, 2010).

 

 

Martagon lily (Lilium martagon)

The natural household

 

All plants and animals are part of the ecological network. The loss of one species can have serious repercussions on other species and the whole ecosystem.

 

When moths, for example, fall victim to street lighting, they are no longer available as prey for birds, bats and frogs. The strongly scented flowers of the martagon lily or the lesser butterfly orchid are pollinated exclusively by moths. When they disappear, their food plants vanish, too.

 

 

Who are the winners?

 

Some bat species such as the pipistrelle have chosen street lights as their favourite hunting grounds. There they make a meal of everything that is attracted by the light, i.e. all kinds of insects. This has nothing to do with protection for bats, however, all the more so as many bat species avoid light. Their food density is increased at the expense of insects, but the bats would be better served by measures to protect their summer and winter quarters and by general improvements to their habitats.

 

Many species of spiders, such as the bridge or grey cross spider, like to attach their webs to outdoor light fixtures so as to trap disoriented and exhausted insects. Geckos and praying mantis have also been sighted on light fixtures (Hölker et al. in Leibniz-Gemeinschaft, 2009).

 

In New York, a number of peregrine falcons have specialised in hunting disoriented birds circling in the bright light of the skyscrapers; they seem to have learnt to take advantage of the light that is proving fatal to other species (Hüppop in Posch, Freyhoff & Uhlmann, 2010).