As a gardener, I usually direct my eyes downward, at the plants that I love, the weeds that need to be removed, the soil and its need for amendment, and insects and birds carrying pollen from flower to flower. I raise them to the sky primarily to determine if the rain predicted is evidenced by any clouds in the sky. I seldom think of the sun and its essential role in helping the plants I love produce the chlorophyll that keeps them healthy and growing. And before now, I never really thought about the darkness of the night and what role it played in my garden.
But a YouTube lecture by Smith College astronomer James Lowenthal started me thinking about those beautiful star-filled nights that backlight my garden and what role they play in keeping order in the natural universe. The lecture is about light pollution and its impact on human sleep patterns and depression, safety on the roads (bright light inhibits our ability to see; it does not enhance it), energy usage, and our ability to take in the night sky. While this initially may not seem like a topic for a garden column, as the lecture unfolded it became clear that the call for regulation of lighting may be of direct interest to gardeners as well, as it impacts plants and their flowering cycles and the pollinators that fertilize them, our meadows and fields, and the plants which are a part of our food supply.
When I moved to the Berkshires, I was so excited to see the array of stars that were visible to me that had been masked by urban light pollution. After a few years of living in Manhattan, day and night had become interchangeable to me. I was in my 20s, after all. It was the era of Jay McInerny and nightlife in New York shone more brightly than the sun in my estimation. I remember going on a date, walking along the Hudson River to see the sun set, and realizing that the sun still rose and set in the city. But times change and so do we, and in the years since my 20s (more than I care to admit) I have come to love the dark skies. As a gardener, I often go out when there is a full moon to tour my garden. It is a great moment to see the forms and shapes of your garden and to assess your success in creating a garden that is not just colorful but filled with a variety of shapes and forms.
But just as artificial light at night impacts humans (it correlates with sleep disorders, depression, and even cancer), it impacts the world outside our bedroom windows as well. Many pollinators (as well as 70 percent of mammals) are nocturnal and are impacted by increasing light pollution at night. Light pollution can reduce pollination of flowers by as much as 62 percent. The increased use of LED lights makes the problem worse, as their lower cost encourages people to light the landscape more brightly. Such lights, particularly when they are aimed upwards, impact pollinators and migrating birds (eighty percent of birds migrate at night using the stars to lead them on their journey), plants in their flowering cycles which can be impacted by perceived daylength, and even the screech owl which helps lower the vole population in my garden by hunting at night. It is even impacting the ability of fireflies to find mates and threatening them with extinction.
Many of us have outdoor lights to make us feel safe, but in reality less light aimed downward and carefully focused can increase our ability to see intruders and pedestrians, uses less electricity, is not reflected into the skies, impacts birds and pollinators less, and allows us to mitigate the effects of light pollution. Even if we are hoping to use lights to simply keep away the wildlife we don’t want around our house, motion activated lights are more effective and contribute much less to light pollution.
At the end of his lecture, Professor Lowenthal has five things to consider when lighting the outdoors. And they seem pretty easy to implement on both a personal and a municipal level.
- All lights should have a clear purpose.
- Light should only be directed where needed.
- Lights should be no brighter than necessary.
- Lights should only be used when useful.
- Warmer colored lights should be used where possible (blue light is more disruptive).
I like to think that by following these rules, I will have other lights that are more awe-inspiring, such as the Pleiades and a night sky illumined by thousands of fireflies. For this, I think I can turn off the light switch.
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A gardener grows through observation, experimentation, and learning from the failures, triumphs, and hard work of oneself and others. In this sense, all gardeners are self-taught, while at the same time intrinsically connected to a tradition and a community that finds satisfaction through working the soil and sharing their experiences with one another. This column explores those relationships and how we learn about the world around us from plants and our fellow gardeners.
