Nantucket Lights: Light Pollution, Plants, and Pollinators

To: Bluedot Living 

From: Gail Walker, Founder and President of Nantucket Lights

Subject: Better Lighting for Better Gardens: Light Pollution, Plants, and Pollinators

Every spring, Nantucket erupts in a riot of color — roadsides thick with daffodils, lush gardens blooming with hydrangeas, storybook cottages covered in distinctive blush-pink roses. and wildflowers brightening our conservation lands. These flowers are an indelible part of the island’s natural heritage. They are also at risk from an unexpected source: outdoor lighting.

Artificial light at night doesn’t just interfere with our ability to enjoy the stars or get a good night’s rest. Carelessly used, it also wreaks havoc with plants and the ecosystem at large. While it’s not possible to reduce the negative impact to zero — after all, we need to ensure the safety of family and guests after the sun goes down — the good news is there’s a lot we can do to minimize harm.

Disrupting Nature’s Rhythms

Over millions of years, plants — and the pollinators they need to thrive and reproduce — evolved together in response to natural light cycles, with the night illuminated only by the stars and the moon. Then came artificial light, disrupting these delicate rhythms. 

While the impact varies from species to species, every artificial light fixture alters the night in some way, with potentially negative consequences for plants and wildlife. Here are some examples:

• Reduced nighttime pollination. Studies have found that nighttime pollinators like moths visit flowers 62% less frequently in artificially lit areas compared to naturally dark ones. Some depend on the lunar cycle to know when to be active; artificial light that mimics a full moon throws them off. Others are disoriented by the light, expending precious energy flying in circles until they die from exhaustion. Artificial light also leaves pollinators exposed, reducing their ability to avoid predators. Others are simply deterred by the unnatural light. The result of all this is a disruption in nighttime pollination, as important to plants as daytime pollination.
• Reduced daytime pollination. Artificial light at night has been found to alter pollination activity even during the day. In some cases, the artificial light shifts the timing of flowering into times of the year when daytime pollinators (think bees, butterflies and birds) are less active or not active at all. Even when that doesn’t happen, the light reduces the sleep and recovery time of daytime pollinators, making it harder for them to pollinate and reproduce. It can also change the scent, color, amount of nectar or other characteristics of plants, making them less attractive to pollinators. 
• Harm to plants beyond the disruption of pollination. Like people and animals, plants need rest at night. When artificial light turns night into day, and they don’t get enough rest, it’s challenging for many of them to stay healthy. It can cause them to continue growing when they should be dormant, or bloom or shed leaves prematurely. It can also render their defenses to pests less effective or cause them to photosynthesize more, which in turn can kill them. 

If we want to avoid this kind of harm — and we should — we need to think harder about how, when and where we use outdoor lighting.

How to Make Outdoor Lighting Pollinator- and Plant-Friendly

Here are some easy ways to make outdoor lighting less harmful to pollinators and plants:

Minimize the amount of illumination

• Turn off (even better, remove or disable) all lighting that’s not needed for safety, security, or functionality. 
• Use lighting that is only as bright as absolutely needed.
• Use dimmers to adjust the brightness depending on the time of night and specific needs. 
• Avoid accent lighting whose only purpose is to highlight plants or other garden features. 

Minimize the area of illumination

• Use fixtures that are fully shielded and aim them down, so no light is directed up or sideways.
• For pathway lighting, use fixtures low to the ground and only as many as needed for safe navigation. 
• Strategically place and aim fixtures to avoid light shining directly on plants.

Minimize the duration of illumination

• Turn off lights as soon as they’re not needed (ideally before 11pm).
• Use motion sensors so that the lights only come on when needed. 

Minimize the emission of blue light

• Use the warmest color temperature possible, ideally 2400K or less.

At a minimum, please comply with the outdoor lighting bylaw that was adopted in 2023. Free guidance is available at nantucketlights.org.

Want to be even more friendly to plants and pollinators? Use shades or curtains to keep indoor lights from lighting up the outdoors. 

A Bonus: More Magical Nights!

Adopting environmentally friendly outdoor lighting will enhance the overall experience of your outdoor space in addition to leading to healthier plants. Imagine stepping into your yard at night and being able to see a full sky of stars overhead while listening to the creatures of the night, undisturbed by artificial lights. That’s a magical moment that most of the world can only dream of. On Nantucket, that could be the reality for all.

This article was reviewed for factual accuracy by John Barentine, founder of Dark Sky Consulting and principal author of the Artificial Light at Night: State of the Science reports published by DarkSky International.