Skyglow forces dung beetles to abandon the Milky Way as their compass

Relevance: Impact of light pollution on the environment

Synopsis: Researchers used Dung beetle to study the impact of the growing light pollution on our environment.

What is Skyglow?

Globally, nights are becoming ever brighter. This light floods directly into the eyes of animals that are active at night and also into the skies. There a proportion of it is redirected back downwards towards an earthbound observer. This is known as ‘skyglow’, an omnipresent sheet of light across the night sky in and around cities that can block all but the very brightest stars from view.

Study on the dung beetle

The study compared the dung-rolling performance of beetles in a rural part of Limpopo province with that of beetles at the University of Witwatersrand in inner city Johannesburg, both in South Africa.

• Findings confirm that beetles exposed to light pollution (direct light and skyglow) are forced to change strategy. They abandon their sky compass and rely instead on earthbound artificial lights as beacons.

This change in strategy comes at a cost.

Impact of light pollution 

Many species that rely on compass references also suffer from the loss of the stars.

• Nocturnal ants use landmarks for outbound journeys, but need their sky compass when returning home.
• Migratory birds have a magnetic compass, with which they check latitude and magnetic North, but use their sky compass to calibrate their magnetic compass to geographic North.

Suggestion/Measures

There is a remarkably simple solution to reducing animals’ experience of direct and indirect light pollution:

• Turning off unnecessary lights at night.
• Shielding of lights: Where lights cannot be turned off, they can be shielded so that they do not shed light into the surrounding environment and sky.
• International Dark Sky Places: The International Dark-Skies Association has certified more than 130 ‘International Dark Sky Places’, where artificial lighting has been adjusted to reduce skyglow and light trespass. However, nearly all are in developed countries in the northern hemisphere. Less-developed regions are often both species-rich and, currently, less light-polluted, presenting an opportunity to invest in lighting solutions before animals there are seriously affected.

Terms to know:

• International Dark-Skies Association