Sunday, December 4, 2011

Light pollution

Light pollution is the emission of artificial light at night with unnecessary intensity, direction, hours and spectral ranges. In other words: illuminating more than necessary. It may seem a minor problem if compared to other types of pollution, but just take a look at this picture of northern Italy taken from the International Space Station (ISS) to realise that it is an issue. If you still have some doubts, take a look at this spectacular video taken from the ISS again showing our planet by night.
What’s the problem with light pollution? After thousands of years living in the dark, electricity allows us to have as much light as we need, and even more, to the point that some people complain of the poorer lighting in some cities, especially in newly-rich countries like Spain. Lately, letters to the editor of most newspapers in Barcelona are about the “poor lighting” in the streets, revealing that we are not aware of the consequences of over-illumination. Let’s analyse this problem in depth.
First, night ecosystems are harmed: light pollution disturbs the night rest of diurnal animals, hinders camouflage and reproduction of nocturnal animals, and disrupts hunter-prey relationships. Secondly, excessive light reduces the visibility of stars to the point that the UNESCO is thinking to declare starlight as World Heritage in order to preserve it. If you have ever seen the night sky in the desert, you know what we mean: it has nothing to do with the night skies you have seen so far. There is an international campaign advocating for the right to see the stars called Starlight Initiative 2007 with the support of some governments and international organisations.
If you are not convinced with such environmental arguments, there are other mundane yet forceful arguments. Artificial light is also directed upwards, towards the sky, which is pointless, and it costs a fortune. Catalonia, for instance, with just 1 out of every 1,000 inhabitants in the world and only one urban area of more than one million inhabitants, spends 30 million euros every year to light the clouds. Do your sums worldwide. In times of social budget cuts, let’s put this figure in context: 30 million euros is more than the cut for international cooperation in Catalonia (from 49 million euros in 2010 to 22 million euros in 2011).
Anyway, we are not only wasting money, but also energy. In 1998, Germans calculated that the energy wasted to light clouds was equivalent to the energy produced by a small nuclear reactor. And bear in mind that Germany is one of the most efficiently-lit countries in the western world! If calculated in terms of fossil fuel, the figures are staggering: according to the Department of the Environment of the government of Catalonia, the amount of wasted light means burning 14,000 tons of fuel and emitting 50,000 tons of CO2 to the atmosphere. It’s worth considering, isn’t it?
How can we end up with such a waste of money and energy and, incidentally, make nocturnal animals, astronomers and poets happy? Basically, we should give priority to lighting downwards (we do not need to see the clouds while driving or walking down the street), use energy-saving lights and be common-sensed to understand that we do not need to have a daylight night. 


  1. Image of northern Italy from the International Space Station showing light pollution:
  2. A spectacular video of our planet as seen from outer space, showing light pollution:
  3. International Dark-Sky Association web site:
  4. Starlight Initiative web site:
  5. International cooperation cuts:

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