Before getting to skyglow, let's just quickly remind ourselves that light at night is one of the most dramatic environmental changes that humans have made to the Earth. Over many parts of the Earth, true night no longer occurs, we experience only twilight or daytime.
The image shows the brightness of skyglow around the world: https://www.science.org/doi/full/10.1126/sciadv.1600377
For every place colored yellow, the sky directly above on a starry night is at least twice as bright as natural.
But does shining a bit of light really change behavior? And what about physiology?
Well, changes in behavior are simple to demonstrate: the whole reason we use artificial light at all is to allow us to see better at night, in order to enjoy ourselves and enable the nighttime economy.
Just as light allows people to get around and stay up later, animals can also use it for the same purpose. This can be beneficial or detrimental, depending on the animal. But it's clearly a huge change compared to their evolutionary experience.
This is my favorite photo for demonstrating the impact of #LightPollution on physiology. The image was taken by shows a soybean field illuminated by a badly directed streetlight.
What's happening here is that soybeans are supposed to grow leaves in the early part of summer, and as nights get longer, they should make #soybeans and turn brown. In the green area, the plants don't understand what time of year it is, and it's therefore a complete loss for the farmer.
The reason I love the photo so much is because you can see the shadow of the light mast on the field.
The photo was taken by Dwaine Eddie McGriff & Ben Tankersley, and originally posted to Xitter (the post no longer exists).
The problem could be entirely solved by using a streetlight with strong backlight shielding (i.e. shining the light only on the roadway).
