The impact of light pollution

The pictures of the earth at night give most of us a sense of awe as we see a world with the bright lights of the cities and the expanses of darkness.

The light dissipating into space is of course a waste of energy. Modern lighting is more controlled and the amount of light directed upwards has reduced over the past decades. However the volume of artificial light at night (ALAN) is still increasing at about 6% per year.

Behind the human story we are conducting a giant experiment on wildlife. The cycle of day and night has been the rhythm of life for millions of years. For nocturnal animals light pollution radically alters their night time environment.

Insects - Many species of insects are in rapid decline and there is growing evidence of the interference of artificial light with the development, movement, foraging, and reproductive success of diverse insect species.

We are all aware that moths are drawn to artificial light, expending energy which can result in them becoming trapped or exhausted. They have less time for feeding and are more liable to predators.

Birds - Birds can be disturbed from sleep. Robins for example seem to be very sensitive to light and will extend their feeding period into the night.

Artificial light disrupts migratory birds’ navigation and can upset the overall timing of their migration.

Bats - Bats have sensitive eyes that are efficient in low light conditions and some species are used to operating in complete darkness. Areas of light can act as a permanent barrier to feeding sites. 

Like many environmental changes the impacts are generally disruptive but there are a few examples of species that are taking advantage. Pipistrelle bats have learned that their prey is attracted to light and have benefited from the enhanced food supply. Peregrine falcons have taken advantage of the longer hours of light in cities and are thriving.

The guidelines for installing outdoor lighting are as follows:

• Make sure your lighting has a clear purpose and consider how the lighting might impact wildlife.

• Try and target the light to where it is specifically needed. 

• Use the lowest level of light actually needed and be aware of reflective surfaces.

• Use timers or motion detectors where possible.

• Use warmer-colour lights (limit the use of blue-violet light)