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There is a new moon tonight. But will it be dark?

Uploaded: Jul 16, 2023

Tonight (Sunday night) there will be a new moon. But for many of you, if you go outside, it won’t be dark. In 2016 researchers found that 88% of Europeans and half of Americans essentially experience perpetual twilight, and over 99% of US and European populations see some sort of skyglow.

Population centers in California are suffused with artificial light at night. You can see the Bay Area, Sacramento, and the greater Los Angeles area in this satellite image. Source: NASA (2016)

According to UCLA Professor Travis Longcore, who has been studying the effects of light pollution for decades, even a “natural” space like Griffith Park in Los Angeles is affected. “The park never really experiences anything dimmer than twice as bright as the full moon … even though it is 4500 acres of open space.”

San Jose and the Capitol Auto Mall at night. Source: Wikimedia (2021)

Where is the light coming from? A study of Tucson found that streetlights were only up to 20% of the problem with the rest attributed to businesses, homes, an airport, advertising signs, sports complexes, and vehicle traffic. There is no single dominant source.

Dr. John Barentine, a light pollution consultant who has helped run several “Dark Sky” organizations, believes that the availability of inexpensive light in the form of LEDs has exacerbated the problem, with more lights illuminating more area over longer periods of time. “It really comes down to an overuse relative to what our needs are. That overuse is a result of … a lack of awareness. A lot of people don’t think that light at night can be a bad thing. They think of it as a social good… and they don’t give a lot of thought to what other effects it might be having on the nighttime environment.”

There are many ways in which artificial light at night distorts the natural environment. Many animals feel safer in the dark. Lit areas and especially lit corridors can impact their ability to travel. Scientists have seen over the years that fish won’t go past a low lit bridge, that bats won’t fly over a lit road, that mountain lions shy away from lit regions. The light distorts their natural behavior and can impact their habitat and range.

In contrast, some animals are attracted to light, and not just moths. Migratory birds can be distracted by lit buildings, and as they circle the buildings they become vulnerable to collisions and fatigue. The haunting 911 memorial in New York City distracted an average of 100,000 birds each year on September 11 until volunteers began turning off the lights for 20 minute intervals as needed so the birds could escape.

The 911 memorial in New York City diverted and killed many birds on September 11 during their fall migration until volunteers stepped up to turn off the lights when birds swarmed to them. Source: pxfuel

Researchers have shown that many young turtle hatchlings and sea birds that would use the stars and moon to navigate out to the ocean will never get there if there is too much light distraction. If you are in Hawaii for vacation, check to see how the resort is lit up at night. The Grand Wailea in Maui was sued a few years ago for the impact of its lights on the endangered Hawaiian petrel.

Turtle hatchlings use the moon and stars to navigate to the ocean, and so can easily be diverted by artificial light at night. Source: Charlotte County

Artificial light at night can interfere with many types of behavior, including pollination, breeding, and foraging. The negative impact of such light extends beyond animals. Some plants have evolved to rely on dark nights. Longcore gives the example of winter soybeans, which set seed and turn brown as winter comes. But if they are exposed to light, winter never comes and they remain green.

Winter soybeans do not go to seed when exposed to artificial light at night, here shown in a concentric circle around a light post. Source: Dwayne Eddie McGriff on Twitter

As Longcore puts it, our wastefulness with light means that we have lost the lunar cycles in many urban areas. We have lost the signal of day length over the course of seasons. We have lost darkness as a refuge for species. The range of impacts is so great that Barentine writes that artificial light at night “is one of the most pressing and imminent threats to global biodiversity.”

Fortunately, an enormous amount of research is underway to quantify some of these effects and develop evidence-based standards and recommendations for lighting. If we are smarter about how we use lighting we can reap the benefits without the negative impacts.

From left to right, this panel illustrates one way that we can optimize lighting to achieve a goal (in this case a lighted path) while reducing the impact on wildlife. Illustration by Leigha DelBusso from Longcore and Rich (2017)

We could also potentially save billions of dollars in the US alone if we eliminated the approximately one-third of our lighting that is wasted, according to the International Dark Sky Association.

If you do go outside on Sunday or Monday night and some of the light you see is from your own home, consider these options:
- Add a sensor to a light fixture, so it only comes on when needed.
- Replace a light switch with a timer switch and set it to turn off at night.
- Replace a light switch with a dimmer switch (if needed) and dim it.
- Switch to a warmer color bulb. Warmer colored bulbs are less intrusive for many (but not all) animals.

Window shades and replacement light fixtures can also help, though they may be pricier.

A bill is making its way through California’s legislature (again) to make sure we have environmentally-friendly light fixtures on government buildings, at least for new fixtures. Governor Gavin Newsom vetoed the first version but because the bill has wide bipartisan support and the sponsorship of organizations including the local Audubon societies, the sponsoring legislators (our own State Senator Josh Becker 13th District and Assemblymember Alex Lee 24th District) have reintroduced it with some changes to reduce cost and provide more exceptions. It no longer applies to replacement fixtures, unfortunately, and the list of exemptions is long. But it’s a start.

I’d love to hear in the comments if you went outside on Sunday or Monday night and looked for artificial light. What were the sources? Where was light useful and where did it seem extraneous? Have you made any changes to reduce night-time light from your home?

Notes and References
1. Night-time light also affects humans, though studies have primarily focused on indoor light. Too much night-time light, and particularly blue light, affects circadian rhythms, which can in turn affect sleep, body temperature, certain hormone levels, blood sugar, immunity, even cancer, with research on-going. For more information, see section 3 on pages 7-9 of this briefing.

Many of you will have seen a setting like this on your computer or smartphone.

Current Climate Data (June 2023)
Global impacts, US impacts, CO2 metric, Climate dashboard

Earth had its warmest June on record. The June sea surface temperature anomaly was the highest for any month on record

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Posted by Mondoman, a resident of Green Acres,
on Jul 16, 2023 at 12:40 pm

Mondoman is a registered user.

When I was a kid, my astronomy club had access to a small property just off Skyline right at the top of the ridgeline. We would camp and observe overnight with our telescopes; the best viewing was when the fog rolled in to a height just below the ridge top, blocking much of the light from Santa Cruz and San Jose and allowing us to observe a much darker sky.
Nice to see this reminder that more light is not always better.

Posted by Bystander, a resident of Another Palo Alto neighborhood,
on Jul 17, 2023 at 7:13 am

Bystander is a registered user.

I believe there is evidence that as humans we do need dark to get good sleep and also to maintain our eyesight. There have been many articles lately about how much light we have in our homes, in particular our bedrooms, from lights that are on our devices, appliances, etc. and recommendations that we should do our best to keep them away from our bedrooms to enable us to sleep better.

We do need to have some light at night particularly if we use the bathroom and don't want to turn the main lights on, but having low level light on for that purpose rather than a motion detector light is not really good for our sleep. Likewise, we are and have been in the habit of leaving a night light on for a baby or a child as a given, when really we should be training our children to sleep without light of any kind. I have read that nightlights for children could be affecting their eyesight as well as their sleeping habits.

Posted by Sherry Listgarten, a Mountain View Online blogger,
on Jul 17, 2023 at 9:49 am

Sherry Listgarten is a registered user.

Well, that was depressing. I went out last night -- here are a few photos. You can see the ambient light reflecting off the clouds. The light was strong enough at the street to cast a clear shadow. We have very tall light poles with bright, blue-tinged unshielded LED lights. It couldn't be much worse. "Perpetual twilight" indeed!

Did anyone else take a look last night? If not, tonight (Monday night) is also a good chance.

Posted by Joseph E. Davis, a resident of Woodside: Emerald Hills,
on Jul 17, 2023 at 11:35 am

Joseph E. Davis is a registered user.

This is definitely something that bugs me a lot. There seems to be a lot of wasted outside light that both uses energy needlessly and is annoying to look at. For example Canada College redid their parking lots a few years ago and now it casts a lot more light on the neighborhood.

I understand the safety concern with dark areas but that could be mitigated by using motion sensitive lights or reducing the amount of light that goes beyond the property.

Posted by TuppenceT, a resident of Adobe-Meadow,
on Jul 17, 2023 at 2:47 pm

TuppenceT is a registered user.

Thank you for bringing up the issue of over-lighting - its devastating to our health and to the natural environment and its reversible. Just turn the light off when not using it!

Posted by anon1234, a resident of College Terrace,
on Jul 17, 2023 at 2:55 pm

anon1234 is a registered user.

Thank you for this important article!!
I did not take photos last night .... this is a growing problem but one i think is easier to control than other environmental disasters!
We should all agree to prohibit this assault on our night skies and the species that depend on the dark to survive, NOW!

Posted by Bystander, a resident of Another Palo Alto neighborhood,
on Jul 18, 2023 at 7:54 am

Bystander is a registered user.

I went out late last night and having read this article yesterday, these are my thoughts.

On my short walk for most of the time I could count at least 4 planes flying in different parts of the sky. Some were more distant or more high and could have been mistaken as stars or at least planets in say a still photograph or a quick glance. But most were obviously a cluster of several lights including red lights and green lights for port and starboard. These lower planes probably coming in to land apart from their noise do make the sky very bright.

Many homes in the area have various types of solar lighting, either to light up their front pathway, as decorative accents, or as a porch light. Presumably since yesterday was a sunny day they would stay bright for most of the hours of darkness but on a dull day they might not be so bright.

Our streetlights are not as good as they once were for actually lighting our path either for vehicles or pedestrians. Many of them are less useful because the surrounding trees have grown so big blocking the light from where it should be and causing more shadows. It is possible for a pedestrian to be completely invisible in these shadows.

Posted by MyFeelz, a resident of another community,
on Jul 18, 2023 at 7:38 pm

MyFeelz is a registered user.

I worked in darkrooms for years. Eventually I could function equally in the dark or daylight. . On camping trips,I had a gas lamp to put on the picnic table. Eventually gave that up too. And when you keep your campsite dark, you also get visitors. Encounters with wildlife, are the gift you receive if you sit quietly in the dark in the woods. Best place to see a carpet of stars or a new moon or full moon: Mount Diablo. If it's night you can see the city lights below, but its far away not to interfere with the overhead view. 2nd best place-- Del Valle.

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