Protecting Darkness at Night, and Why Gardeners Should Care
April 21-28, the week of this month’s new moon, is International Dark Sky Week. This is a worldwide celebration of darkness at night. It is also part of an effort to build awareness about the harmful impact of light pollution on humans and wildlife, including birds and insects in our gardens.
Light Pollution’s Impact on Humans: Darkness at night allows us to see our place in the universe and to be awed by the beauty of the stars. This is just one of many reasons to be concerned about the disappearing darkness of the night. Light pollution is causing our nights to become almost 10 percent brighter every year, according to data from citizen scientists. This is in large part due to the advances in LED lighting, making it relatively inexpensive to install brighter and bluer light. This light shines into the sky where it is scattered, and it reflects off surfaces to create domes of light over our cities.
The disappearing darkness not only limits our view of the stars, but it also has serious implications for the health of all living things on the planet. Over billions of years, all biological processes have evolved with the Earth’s predictable rhythm of night and day. Our response to this predictable rhythm is encoded in our DNA. There is growing evidence that the disruption of the day/night cycle can have serious consequences for our mental and bodily health.
Nighttime exposure to artificial light, specifically the blue light emitted from LEDs, suppresses production of melatonin, which is needed to keep us healthy. Melatonin has antioxidant properties, induces sleep, boosts the immune system, lowers cholesterol, and helps our body function properly. Recognizing the health effects of high-intensity LED lighting, the American Medical Association has issued guidance urging communities to minimize and control blue-rich environmental lighting.
Light Pollution’s Impact on the Natural World: If artificial light at night is dangerous to us, it should be no surprise that its impact on the natural world is far reaching as well. International Dark Sky Week falls in the middle of the spring bird migration. Some 70 percent of birds migrate, and 80 percent of migrating birds fly at night. Migrating birds become disoriented when their celestial map is obscured by light pollution coming from sources such as the windows of buildings, security lighting and streetlights. This results in the deaths of millions of birds every year due to direct collisions with buildings or from exhaustion.
Artificial lighting also disrupts nocturnal pollinators like bats and moths and insects like lightning bugs. In fact, research shows that artificial light at night is a substantial contributor to the world’s massive declines in insect diversity and abundance, described as the insect apocalypse.
Excessive Lighting Wastes Energy, Costs Money and Contributes to Climate Change
The light detected by satellites is wasted light because it is not providing any useful illumination to us on Earth. The U.S. Department of Energy reports that “well under 1 percent of light generated by luminaires reaches an occupant’s eye.” This means that at any given moment, at least 99 percent of artificial light we produce is not serving a useful purpose. In the United States alone, outdoor lighting consumes enough energy to power 35 million homes each year, which adds up to a significant source of greenhouse gas emissions. The worldwide cost of this wasted light is estimated to be over $50 billion a year.
Does More Light at Night Keep Us Safer?
Scientific evidence does not support the belief or practice that more lighting and brighter lighting universally increases safety and security. A 1997 National Institute of Justice study concluded, “We can have very little confidence that improved lighting prevents crime.” A study published in 2000 found that an increase in alley lighting in Chicago resulted in an increase in reported crimes in all categories. Reductions in streetlighting in Wales and England have not resulted in increases in crime and accidents. Poor lighting design that produces glare and reduces contrast degrades and impairs vision rather than enhancing visibility. Safety is improved with well-designed lighting that follows the five principles of responsible lighting (see below).
What Can We Do to Address the Problem of Light Pollution?
In Your Home:
The good news is we can easily make a difference by following the five principles of responsible outdoor lighting as recommended by Dark Sky International and the Illuminating Engineering Society:
1. Useful—Use light only when it is needed. Consider the impact on your neighbors and wildlife. Drop your blinds at night to prevent light from spilling out. Turn outdoor lights off when not needed. Avoid solar lights that stay on all night. Never up-light trees or leave string lights on overnight.
2. Targeted—Direct light so it falls where it is needed. Use shielding to keep light from shining into the sky or into your neighbor’s windows.
3. Low level—Keep lights at the lowest level possible. It does not take much light to see where you are walking at night once your eyes have adjusted to the darkness.
4. Controlled—Use timers and motion sensors to provide illumination only when it is needed.
5. Color Temperature—Use warmer-colored light, and limit the amount of shorter wavelength (blue-violet) light.
Choose the right bulbs by reading the label. Select bulbs with the warmest temperature and the lowest lumens. Also at home, try this experiment: stop “screen time” for two hours before bed, move cell phone chargers out of bedrooms, and dim indoor lights at home for several hours before bedtime. See if your sleep is enhanced.
In Your Community:
● Advocate for stronger local outdoor lighting ordinances and enforcement. In Albemarle County, the Board of Supervisors recently issued a proclamation recognizing International Dark Sky Week, noting light pollution’s “significant impacts to the ecology and human health of all communities.”
● Share knowledge and encourage neighbors, businesses and houses of worship to adopt responsible lighting practices and to participate in Audubon’s Lights Out program during the spring and fall bird migration.
● Visit one of the state’s International Dark Sky Parks and participate in local stargazing programs.
Together we can bring back the darkness at night to enjoy the stars and the fireflies and to reconnect with the natural rhythms of day and night. We must act now to protect our health and the health of the planet.
Prepared by Master Gardener Christine Putnam, a member of the Albemarle County Natural Heritage Committee and a member of Dark Skies Piedmont
Additional reading:
Artificial Light at Night: State of the Science 2024, Dark Sky International
https://darksky.org/app/uploads/2024/06/ALAN-State-of-the-Science-2024-EN-1.pdf