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How Outdoor Lighting Influences Wildlife and Your Garden

How outdoor lighting influences local wildlife and your garden. pictured is a garden at night with lots of landscape lighting

This year, Massachusetts Governor Maura Healy designated April 2-8 as Dark Sky Week for the Commonwealth. There is also legislation moving through the Senate (S.2102) and the House (H.4502) to establish best practices for state and municipal lighting projects – but why does this matter to you and your garden?

 

Depending on the type of exterior lights and how they're used, excessive artificial light at night can disrupt the natural cycles of plants and wildlife. However, strategically placed and properly timed lights can provide illumination without harming your garden and the surrounding ecology. By being mindful of your contribution to light pollution and taking steps to reduce it, you can help protect the environment, promote the health of your garden, preserve the beauty of the night sky, and save money on energy in the process.


2023 satellite imagery of light pollution in Massachusetts and a close-up of the Groton area

 

Outside lights can be bad for pollinators, birds, and even your plants due to the following reasons:

 

Disruption of Behavior: Bright lights at night can disrupt the behavior of nocturnal pollinators, such as moths and bats, which are important for pollinating certain plants. These animals may be attracted to the light source instead of carrying out their natural behaviors like pollination. Light pollution also has had a dramatic impact on fireflies whose gentle flickers to attract a mate can’t compete with exterior lighting. Artificial light at night can also disrupt the natural light-dark cycle that plants rely on for growth, reproduction, and behavior. This disruption can affect plant flowering, fruiting – meaning that some night-blooming flowers (like evening primrose) might not be open for business when nocturnal pollinators stop by.


Firefly and Evening Primrose flower


Interference with Navigation: Migratory birds, as well as nocturnal birds, like owls, use natural cues such as the moon and stars to navigate. Artificial lights can interfere with these cues, leading to disorientation and difficulty finding food or shelter.


Barred Owl in a tree in the evening

Barred Owl in a tree

 

Attracting Predators and Disrupting Nesting: Lights can attract predators of pollinators and birds, leading to a decrease in their population. Conversely, bright lights also attract pests to your garden that may feed on your plants or disrupt the ecosystem balance by becoming overly abundant. Bright lights can also confuse the circadian rhythms of nesting birds, negatively impacting their ability to care for their young.


Chickadee feeding its young

Chickadee feeding its young

 

To mitigate these effects, using outdoor lighting thoughtfully, employing techniques such as shielding lights, motion sensors, and choosing fixtures with warmer, less disruptive wavelengths is important. There are several types of exterior lighting commercially available designed to reduce impact on the local ecology.

 

Using low-intensity lights with warm hues can help reduce disruption to nocturnal animals and insects. LED lights are particularly energy-efficient and can be designed to emit light in specific wavelengths (think warm, not blue light) that are less disruptive to wildlife and plants.

 

Installing lights that are directed downwards and shielded can minimize light pollution by focusing the light where it's needed, such as pathways or entrances, without unnecessarily illuminating the sky or surrounding areas. There are also niche “dark sky-friendly fixtures” designed to minimize light pollution by directing light downwards and that also reduce glare and upward light spillage.

 

Lights equipped with motion sensors only activate when motion is detected, reducing unnecessary illumination and disturbance to the ecosystem while still providing security when needed. Timers and dimmers are another option that can be used to control the timing and intensity of outdoor lighting, ensuring that it's only on when necessary and at the appropriate brightness level. Both of these options are also energy efficient, saving you money as you ultimately reduce the time your exterior lights are on.

 

With some mindful Dark Sky practices (and maybe incorporating some eco-friendly lighting options) you can illuminate your outdoor spaces while helping wildlife, your garden, and the local ecology. So, go ahead and leave the lights on for your friends or have an evening garden party (or two!) this summer; just remember to turn off the lights when you aren't using them.

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