Light pollution
- August 1, 2021
- Posted by: OptimizeIAS Team
- Category: DPN Topics
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Light pollution
Subject: Environment
Context: Globally, nights are becoming ever brighter. Increasing urbanisation and the installation of new streetlights, security floodlights and outdoor ornamental lighting all contribute to growing light pollution.
Context:
Dung beetles mechanism of dung pile
- They are found across southern Africa, India, collect dung from various animals, fashioning it into a ball. By rolling this ball away from the dung pile they need not share it with other insects
- They leave the dung pile as quickly as possible, by using their internal compass to travel in a straight line away from it.
- Before rolling the dung away to an area where it can safely dig into the ground, rest and feed, each beetle climbs on top of its ball and performs a brief pirouette termed the orientation ‘dance’. It scans the scene for features it can use to hold its course.
- Since it starts each night in unfamiliar territory, the most reliable references are those in the sky that stay stable while the beetle maintains the same heading. On starlit nights, the Milky Way acts as these beetles’ primary reference.
- When the beetles relied on artificial lights to navigate, they all rolled towards them — numerous beetles rolling in the same direction. Under natural conditions, they almost always roll in different directions. Rolling towards artificial lights makes them more likely to encounter one another and fights may break out as the beetles try to steal each other’s dung balls.
- Artificial light is also more likely to guide beetles into the concrete and asphalt regions of their immediate environment, where they may find themselves unable to dig into the ground and bury their ball.
Effect of Light pollution in dung beetle
- The 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.
- On a study of ‘sky compass’ of the nocturnal dung beetle, Scarabaeus satyrus, to compare orientation under pristine and light polluted skies.
- The study compared the dung-rolling performance of beetles with that of beetles and the findings confirm that beetles exposed to light pollution both directly through the glare of bright artificial lights and indirectly via skyglow that obscures the stars are forced to change strategy. They abandon their sky compass and rely instead on earthbound artificial lights as beacons.
Other species affected by light pollution
- 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.
- In the worst case, animals that need the stars to find their home or breeding site may never make it. But even with their backup systems, Brighter night skies may cause them to gradually deviate off course, wasting energy and risking predator encounters.
Solutions
- The simple solution is to reducing animals’ experience of direct and indirect light pollution: turning off unnecessary lights at night. Where lights cannot be turned off, they can be shielded so that they do not shed light into the surrounding environment and sky.
- 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.