Light pollution is a hidden problem with a variety of detrimental impacts to us and our surroundings. But with a little education and awareness, this form of pollution can be greatly reduced everywhere and with zero (yes, zero) impact on the quality function of outdoor nighttime lighting.
My purpose is not to shame but to inform. Because most people do not even know of light pollution as a real problem, it is largely ignored in light design (although this seems to be changing, very gradually). Discussing concrete real-world examples and how one might go about fixing them is the best solution.
Onto today's example. I came across this amazing treehouse DIY project on Reddit. It is very cool and impressive. But the one issue? The lighting. As you can see from the picture above, it uses non-shielded bulb strings.
Non-shielded bulbs of any sort emit stray photons into the sky, contributing to light pollution.
Even though the treehouse looks to be built in a remote area, the main danger here is that thousands of people will see this design, including the light setup, and look to copy it in their own living spaces. Most people's properties are almost guaranteed to be far more densely populated than our example. Plus, strung light bulbs like this are a general contributing factor to pollution in many backyards. Sure, they look nice and conjure allusions of Bilbo Baggins's birthday party in The Lord of the Rings., but they are completely unshielded, spread over a wide area, and emit photons in all directions.
Also in this example, since the treehouse is likely isolated in the wilderness, a bright beacon like this could have detrimental effects to the surrounding wildlife ecology. Granted, this is a big unknown as to how much of an impact such a beacon has, not just to the larger animals, but small too, and plant life. Chances are, though, that the lights are not on very frequently, greatly reducing their impact.
I am not sure if there is a good light pollution remedy to the common backyard bulb string, but ideally each bulb should have a completely encompassing shield that directs light exclusively down. This, after all, is where the light is needed - especially in this example photo - to avoid falling off that cliff!
Placing a few shielded light fixtures directly on the surrounding trees, in conjunction with a shielded porch light or two on the treehouse itself, would go a long way towards directing light where it is needed, and not allowing it to spill into the open sky, nor potentially harm the surrounding wildlife.
If you have other suggestions on how to solve this light pollution example, please let me know in Comments!