In defense of darkness

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Earth needs darkness just as much as it needs light.

But human light pollution is pushing back the dark, which is changing the natural world, and could be hurting us, too.

Johan Eklöf , scientist and bat researcher. Author of The Darkness Manifesto: On Light Pollution, Night Ecology, and the Ancient Rhythms That Sustain Life .

Emily Fobert , research fellow at the University of Melbourne who studies the impact of light pollution on marine species.

Geoff Goins , visitor services supervisor at New Mexico’s Capulin Volcano National Monument, a certified Dark Sky Park.

Keith Krueger , Pinal County, Arizona resident and citizen scientist whose neighborhood doesn’t have streetlights.

Casey Rodriguez , dark sky advocate in Pittsburgh, Pennsylvania.

Zach Thompson , dark sky advocate with the International Dark Sky Association in Lincoln, Nebraska.

On inspiration for The Darkness Manifesto

"I'm very often mixed up for this guy in Stockholm, which has he has the same name as me, but he's a marine biologist. ... He emailed me the other day and say, Hey, everybody calls me but about the book. I've been doing research on bats for 25 years and being out a lot during the evenings. And a few years ago, we realized that, well, that's often lived in churches, at least here in Sweden. And in the nineties, all the churches started to use floodlights, too. Well, we have seen some hundreds or even thousand-year-old church buildings.

"And of course, the municipality wants you to show off these buildings and so they put floodlights on them. Then we started to investigate what happens to the bats, and it turned out they either move or they just starve to death. So in 30 years' time, half of the bats living in churches is actually gone. And when realizing that, I thought that, well, this is not just about bats, it's not about killing bats. It's about killing the night. And that must mean something. And to animals, to plants and even to ourselves. So that's when I started to write a book about darkness."

On the human need for darkness

"There is something about the night sky that perhaps we don't realize that we miss it every day. But if we think about it, we want to see these stars. There are so many. ... And somehow this connects us to history and to our forefathers seeing the same stars and things like that. But that is, of course, very hard to measure. It's just a feeling of missing out. And there are so many other things with the darkness that we actually need."

On how night affects the body

"As any other animal we have a cycle, we have a rhythm. If they're active during the day, we sleep during the night, and for the body to come to rest and relax, we need our sleep hormone, the melatonin. And that is something that is triggered by darkness. And that makes us all the muscles are testing our body temperature drops and a lot of things happen in your body and to make sure your immune system works correctly.

"And if we have the lights on for too long, or if we never get start this melatonin never really isn't triggered properly. So first of all, we have a hard time to sleep. But this hormone system also triggers other hormone systems, for example, making us hungry in the middle of the night. ... And there are all sorts of things happening, which we have been starting to see a link between different diseases and artificial light, actually."

On improving the welfare of the planet

"There are so many things we can do, if we choose to turn off the lights when we don't need them. For example, if you're in your garden having a barbecue or whatever in the evening and when you go inside and watch TV instead, you can just turn off the lights in your garden and then you would still have night outside. If you have a bicycle path through a park and the lights are just turned on the moment someone actually uses it. And then we turn off the lights again using timers or motion sensors or something like that. We would still have light, and at the same time we would benefit from the lights as we intended to. So there are so many things we can do and we just use the technology that we have."

Journal of Ecology : " Ecological effects of artificial light at night on wild plants " — "Plants use light as a source of both energy and information. Plant physiological responses to light, and interactions between plants and animals (such as herbivory and pollination), have evolved under a more or less stable regime of 24-h cycles of light and darkness, and, outside of the tropics, seasonal variation in day length."