New Research Shines Light on Light Pollution

Friday 24th January 2014

What do Italy, Poland, Serbia and Exeter all have in common?

Clue: It’s not that they are all home to a world class light pollution research team, although that is certainly true of Exeter.

Answer: They all shine brighter at night now than they did 10 years ago.

An enlightening new study has used nocturnal satellite images of Europe to develop a map showing where the amount of light spilling out from roads, industry and cities has increased or decreased between 1990 and 2010.

The results are fascinating.

While light pollution from Europe has increased very markedly, the pattern is anything but uniform.  Most countries have increased their light pollution levels, including most notably the above countries, Portugal and France, but some countries are now much less polluting, particularly Slovakia, Sweden, Ukraine, Finland and Belgium.  In these countries and in the seaside resort Torbay, just down the road from polluting Exeter, levels of light pollution have plummeted by up to 20%.

The picture in the UK is generally mixed and our modest increase in pollution leaves the UK ranked as the 10th lowest increase.

It is difficult for humans to perceive light as pollution.  We are fundamentally a diurnal species, but we extend our daily boundaries with artificial light.  Light is our friend and ally.

We forget that the night is already occupied – that’s where the nocturnal species live!

There are swathes of types of animals who are restricted to night time exploits.  Earthworms, beetles, snail, moths, woodlice, spiders and many more animals are primarily active in darkness.  Many are wildly more, and differently, sensitive to light than humans.  Nocturnal wildlife activity patterns are dominated by moonlight.  Full moonlight and predators hunt, the prey hides, and for some mating or dispersal is triggered, on moonless nights the prey feeds.

Changes in the background levels of light, changes that we would hardly notice, can transform nocturnal ecology.  Badly placed or designed street lights can:

  1. Attract hundreds of insects and result in the death of a third of them
  2. Halt the turnover of water in lakes – usually driven by the nocturnal movements of plankton
  3. Prevent riverfly dispersal
  4. Cause the local extinction of rare and declining species
  5. Create lonely-hearted glow-worms unable to find their better halves.


For more on the environmental impacts of light pollution and how they could be avoided please read “A Review of the Impact of Artificial Light on Invertebrates” (Bruce-White and Shardlow 2011).

The new study by Jonathan Bennie and Kevin Gaston’s research team at Exeter University is a fabulous breakthrough.  Not only can we see light pollution, we can see how it is changing and the pattern that this reveals is one of hope.  Particularly uplifting are the clear borders visible on the map between countries like France and Belgium and Slovakia and Poland.  While some changes are the result of industrial decline or shift, it is also clear that policy decisions about lighting type, siting and abundance are enabling some countries and cities to reduce their light and energy waste – for instance Belgium has reduced lighting on its road system.

This and other fantastic scientific studies continue to illuminate and highlight the ecological harm that our light pollution is doing, but also that we have all the technology, and the inspiration to reduce energy use and costs, that we need to greatly reduce light pollution.

Let’s encourage councils to save money, save wildlife and turn the light down.

Figures from ‘Contrasting trends in light pollution across Europe based on satellite observed night time lights’  Bennie, J., Davies, T. W., Duffy, J. P., Inger, R. and Gaston, K. J. Scientific Reports 4, Article number: 3789, Published 21 January 2014.

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