Once in a while a client asks me if I design landscape lighting. The answer is a definitive no. In fact, I recommend against it. With a few exceptions.
Landscape lighting is marketed as a way to beautify your home, accentuate your plants, and make your home safer. However, it creates serious problems for birds and pollinators. It also wastes energy and creates light pollution.
Light pollution is a major problem in most metropolitan and residential areas.
"The fact is that much outdoor lighting used at night is inefficient, overly bright, poorly targeted, improperly shielded, and, in many cases, completely unnecessary." -- the International Dark-Sky Association
There are a lot of reasons light pollution is a problem, including unnecessary energy use (my personal pet peeve), but since this is a landscaping and gardening blog, let's focus on its effects on wildlife. Upward directed lighting, like those shining on the front of a house or up into trees, can disorient birds, especially during their migration. Lights in general draw pollinators to them, causing flying insects to spend all their time flying around the light source instead of eating or reproducing. Remember the bug zapper? Can you believe we used to use those? There is some anecdotal evidence that suggests switching out your white light bulbs for amber ones attracts less insects, but I don't know if that has been scientifically proven. Lights can also disrupt the activities of nocturnal wildlife, who depend on darkness for hunting and breeding. Lighting can disrupt wildlife's sense of day/night and even the seasons. Bright street lights can even prevent trees from sensing when it's time to go dormant in the fall.
For me, the only outdoor lighting I recommend is for safety. I'm not talking about crime prevention. Studies have shown that excess lighting does not prevent crime. I'm talking about preventing personal injury in the dark. Porch lights are necessary but can be activated with motion sensors. The same goes for path lighting. Path lights should always be directed downward (shielded) onto the path only. These can also be activated with a motion sensor.
What do you do if your home is already fired up with landscape lighting? Turn it off. Uninstall it. Or just use it for special occasions when you will be having guests. Get those path and porch lights on a motion sensor.
And what about holiday lights? I'm a little torn on this one. It's a fun tradition. We put lights up on the house every year. They consume a lot of unnecessary energy. Maybe those big light shows and displays are not so great? Here in South Central PA, I don't think the time period for holiday lights coincides with bird migration or much insect activity. I don't know enough about winter wildlife habits to know how detrimental it might be. Plant dormancy is unlikely to be affected by holiday lights. But that's not true for every part of the country where plants and wildlife are still active at that time of year.
So, in my opinion, save your money and only use the minimum necessary lighting for safety reasons, and let the wildlife (and humans!) have as much darkness as you can.
tl;dr
Use your existing lighting only on special occasions.
Eliminate upward and outward directed lights in the landscape.
Make sure path lighting is directed only downward, directly onto the path, or use marker lights.
Use Dark-Sky Friendly lighting (click the logo to find some).
Get your porch and path lighting on a motion sensor.
Consider minimizing your holiday light display, especially if you're in an area with active wildlife and plant growth during the holiday season.
Remember, darkness is a good thing for humans, wildlife, and plants!