When you picture nighttime in a perfectly landscaped garden, chances are good that you imagine it lit. According to National Association of Homebuyers survey data, close to 90 percent of people find exterior lighting desirable. Close to half consider it essential.
But wildlife experts and ecologists say outdoor lighting has become excessive, and it’s having an outsize impact on the species that share our habitats. Artificial outdoor lighting negatively affects insects, birds, bats and other small mammals, and it can even make the plants in your garden less productive.
The good news is there’s an easy fix: more darkness. And turning out the lights doesn’t have to mean your garden is off-limits. There are ways to enjoy it just as much after the sun goes down.
Disrupting the dark
“If you’ve ever had a neighbor with a light that shines in your window when you’re trying to sleep, you know it’s really disrupting to your cycle,” says Mary Phillips, head of the native plant habitat impact team at the National Wildlife Federation. “It’s the same for wildlife in general but particularly our nocturnal species.”
It may seem like your garden “goes to sleep,” says Travis Longcore, senior associate director of the UCLA Institute of Environment and Sustainability, and — like humans — many species do use the night as a period of rest and recovery. “But then there’s all these things that come to life at night,” Longcore says. “Scavengers, spiders, all the things that are vulnerable to desiccation and predators during the day. Wood lice, centipedes, millipedes, snails, slugs and earthworms all take advantage of the fact that nights are more humid and that it’s a little harder for the predators to see them.”
All those nocturnal garden inhabitants perform ecosystem services, including scavenging and composting, but light can disrupt those jobs.
“Some insects are very attracted to light; you’ve probably seen them circling,” Phillips says. “They’re basically draining their energy, and then they’re not out there doing their regular cycle of feeding and mating. They’re vulnerable because they’re very visible to predators. Over time, this leads to lower populations and shorter lifespans for these important species.”
One thing that makes some nocturnal species so important, especially in the garden, is their role as pollinators. “We have a tendency to think of pollinators as simply being daytime species, when in fact moths and bats and other things that move around at night are doing a lot of it,” Longcore says. “All sorts of plants take advantage. There are moth-pollinated flowers that only open at night.”
But it’s not just those plants that don’t thrive as well without darkness. Eventually, what happens in the garden at night will also begin to affect how it produces during the day. Longcore points to a study by Swiss researchers that “showed that places that have lights at night have reduced flower seed set, and then reduced flowers the next year, and then reduced daytime pollinators,” he says. “Lights at night have a cascading impact.”
And that impact has grown in recent years as the night has become increasingly well-lit. “As a thing gets cheaper, people use more of it,” Longcore says. “We see that with lights and LEDs. When I grew up, you didn’t leave lights on all the time if you didn’t need them. You turned the porch light on when somebody was coming to visit. You didn’t just leave it on all night for ‘safety.’ It’s incredibly wasteful, and it affects all these other things.”
But the solution is simple and can be implemented quickly, Longcore adds.
“If we think about sustainability and meeting conservation and climate goals,” he says, “doing lighting better is the easiest, simplest, lowest-lift thing that we could possibly do.”
Embracing the evening
The first step to creating healthier darkness, Longcore says, is to take stock of your current outdoor lighting and see what you can do without. “Even little solar lights can affect the distribution of species,” he says. In the places where you absolutely need to have light, choose something a bit more bug-friendly. “Longer-wavelength lights are going to be better than shorter-wavelength lights,” he says, “so yellow and red — like the ’bug lights’ that you can buy — are better.”
Longcore understands that outdoor lighting can offer a sense of security (although some research finds it doesn’t actually reduce crime), but he suggests using a light that goes on when you need it and stays off when you don’t. “Put it on a motion detector so that you’re not bathing everything with light all the time,” he says. “And put it on the shortest duration that you can.”
Once you’ve reduced the light, don’t let the darkness chase you inside. In fact, the evening can offer a whole new way to enjoy your garden.
“Especially in the heat of the summer when it’s just too hot with the sun beating down during the day, weeding at night can be preferable, not to mention peaceful from a mental health perspective,” Phillips says.
Go out at dusk “and let it get dark as you work, so your eyes can adjust,” she suggests. “The other cool thing is you become really aware of your surroundings as the light fades.”
If you find you really enjoy that extended garden time, you can even begin to choose plants specifically for enjoyment after dark. “Some people call it a moon garden,” Phillips says. “There are night-blooming plants that have pale or fragrant flowers.”
The ultra-fragrant blooms of varieties such as jasmine, flowering tobacco and moonflower open after the sun sets. Plants with white or silver foliage and flowers can reflect moonlight. “Evening primrose opens at dusk and then almost glows,” Phillips says. “Oak leaf hydrangeas have really big white blooms, and they look stunning.”
There are a lot of ways darkness can transform your garden, most notably by increasing biodiversity. “Even within a season, you’re going to see significant new activity,” Phillips says. You may notice more moths, beetles, bats and other small mammals. More crickets and cicadas might mean more nighttime noise.
“When you’re out there gardening or just sitting on your patio observing all this, it’s really amazing to see all the activity that’s going on,” Phillips says. “And if you turn on the big, bright porch light, you’ll miss it all.”
Kate Morgan is a freelance writer in Richland, Pennsylvania.
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