A dark night sky may become a thing of the past – unless we are very careful. Just a century ago, we all experienced dark skies after nightfall, but now our world is illuminated around the clock. The result is light pollution, and the effects could be far-reaching.

The International Dark-Sky Association (IDA) defines light pollution as inappropriate or excessive use of artificial light. A recognised authority on light pollution, The IDA campaigns for "the protection of the night sky". Their work led to the creation of The Dark Sky Places Program which, since 2001, has encouraged communities worldwide to restrict their output of light at night. And their work has not come a moment too soon. Since the advent of electric lights, outdoor lighting has grown at between 3%-6% annually in the second half of the 20th century. Human productivity has benefited, but the night has lost out.

So why should we be concerned? Well, for a start 30% of vertebrates and more than 60% of invertebrates are nocturnal. And as Franz Holker of the Leibniz-Institute of Freshwater Ecology and Inland Fisheries says: “The problem is that light has been introduced in places, times and intensities at which it does not naturally occur, and many organisms have had no chance to adapt to this new stressor.”

It has also been suggested that human health suffers. Artificial light at night has been linked to diabetes, obesity, depression and some cancers, as well as sleep disorders. The issue is that darkness promotes our natural production of the hormone melatonin, which helps maintain our sleep cycle, and which also may strengthen our immune system.

A remarkable Interactive world map reveals the areas worst affected by artificial light. You can find it at https://www.lightpollutionmap.info

Sources:

1.Mother Nature Network:
Light pollution impacts energy use, wildlife and health.

2.The LA Times:
Artificial lights are eating away at dark nights .