July 2025: Know, But Don’t Know Your Fireflies!, Light Pollution News.

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This Episode:

In this episode, we take a deep dive into fireflies. And that’s a good thing because we have the President of the Pennsylvania Firefly Festival, Jeff Calta, here to talk about everything related to our little flying friends. Also here, is Dark Sky International’s Tom Reinert!

We talk about the importance of data collection; how three townships in Ohio turned off the lights for mayflies; and we asked – do plants care if pollination happens during the daytime vs nighttime? Listen up next for the answer!

Host:

Guests:

1. See photos of Manhattanhenge as seen from 42nd St. in Manhattan, Seth Harrison, Iohud.
2. Manhattanhenge 2025 continues tonight in NYC. Here’s where to watch for the best view., Renee Anderson, CBS News New York.
3. Space-time cube reveals escalating light pollution in China’s national parks: impact of boundary geometry and human activities (1992–2021), Environmental Pollution.
4. Night lights from space: potential of SDGSAT-1 for ecological applications, Remote Sensing in Ecology and Conservation.
5. Dark Skies, Nevada Division of Outdoor Recreation.
6. State resource aims to preserve night skies, support dark sky tourism, Las Vegas Sun.
7. Oregon route named one of the best train rides in the U.S. for stargazing, Kjerstin Gabrielson, The Oregonian.
8. 10 of the dreamiest stargazing trains in the U.S., Megan Eaves, National Geographic.
9. Streets going dark to deter mayflies, Caitlin Hunt, News5.
10. Pollination Across the Diel Cycle: A Global Meta-Analysis, Ecology Letters.
11. Nocturnal pollinators just as important as their daytime colleagues, study finds, Phys.org.
12. Bees face new threats, putting our survival & theirs at risk, University of Reading.
13. Effects of different intensities of artificial light at night on functional traits of invasive and native plants, Journal of Plant Ecology.
14. What evidence exists on the impacts of artificial light on terrestrial non-flying mammals native to Europe? A systematic map and a narrative review, Frontiers in Ecology and Evolution.
15. How LED lights can help birds avoid fatal run-ins with windows, NPR.
16. Hawk Masters Traffic Lights to Hunt Urban Prey, ScienceBlog.com.

Light Pollution News: July Highlights

Manhattanhenge in NYC

Manhattanhenge is a stunning annual event in New York City when the setting or rising sun aligns perfectly with the city’s street grid, creating breathtaking views. In 2025, the phenomenon was visible on May 29 due to cloud cover, with another opportunity coming on July 11 and 121.

Light Pollution Trends in China’s National Parks

A recent study published in Environmental Pollution analyzed nearly 30 years of light pollution data across five Chinese national parks: Panda, Northeast Tiger and Leopard, Hainan Tropical Rainforest, Sanjiangyuan, and Wuyi Mountain. The research found significant increases in light pollution, mainly from park boundaries and nearby settlements. Advanced visualization tools, like space-time cubes, helped pinpoint areas most affected by artificial lighting.

SDGSAT-1 Satellite Advances Nighttime Light Analysis

The Chinese SDGSAT-1 satellite, launched in 2021, offers high-resolution nighttime light data, detecting sources as close as 40 meters apart—far surpassing previous satellites. Its multi-spectral imaging helps researchers monitor light pollution, assess dark sky preservation efforts, and map nocturnal wildlife corridors, although it cannot determine light directionality.

Nevada’s Dark Skies Certification and Astrotourism

Nevada has launched a dark skies certification program, encouraging responsible outdoor lighting for homeowners, businesses, and municipalities. Certified locations can boost astrotourism, attracting visitors to stargazing experiences like the Ely stargazing train and Oregon Coast Scenic Railway’s Moonlight Excursion, which offers scenic nighttime rides along Tillamook Bay.

Ecology News: Light Pollution’s Impact on Wildlife and Plants

• Mayflies in Ohio: Streetlights were temporarily turned off to protect mayflies, whose deaths create hazardous road conditions and disrupt local ecosystems. Mayflies are crucial for healthy waterways and serve as food for birds and other wildlife.
• Nighttime Pollinators: Research highlights a bias toward studying daytime pollinators, even though bats, moths, and nocturnal butterflies play essential roles. A meta-analysis found that 90% of 139 plant species benefit equally from day and night pollinators, emphasizing the need to protect nocturnal species.
• Light Pollution and Pollinators: According to the University of Reading’s Bee: Wild report, light pollution is now the ninth biggest threat to pollinators, disrupting moth behavior and reducing pollination visits by up to 62%.
• Invasive Plants: A study in the Journal of Plant Ecology found that artificial light at night (ALAN) boosts the growth of invasive plant species, especially under higher light levels, while native plants often suffer. This gives invasives a competitive edge, partly due to improved nitrogen use efficiency.
• Mammals and Circadian Disruption: A meta-analysis in Frontiers revealed that light pollution disrupts the circadian rhythms of non-flying European mammals, affecting sleep, hormone production, breeding, and hibernation cycles.
• Reducing Bird Collisions: Utah State University researchers found that shining ultraviolet LED lights on window glass with UV coatings can eliminate bird deaths from collisions, though widespread implementation requires more funding.

Wildlife Adaptation: Urban Hawks

A Cooper’s hawk in New Jersey has learned to use traffic light cues and audible crosswalk signals to hunt more effectively during morning commutes, showcasing the adaptability of urban wildlife

Light Pollution News: July Read Along

Let’s kick off this episode with an interesting event that occurs annually in New York City. The city, known for its towering structures, experiences what is called Manhattanhenge a handful of times a year. This is exactly what you think it is – when the sun either rising or setting crests the horizon and aligns with the city grid.

This year it was slated to be May 28^th and 29^th, but due to clouds, viewers only caught the sun’s glow on the 29^th. Don’t worry if you live in the City, you’ll have a second try on July 11^th and 12^th.

There’s a study out of the journal ‘Environmental Pollution‘ that provides a pretty succinct visualization of sky glow changes that occurred at five national parks in China. Those parks are Panda, Northeast Tiger and Leopard, Hainan Tropical Rainforest, Sanjiangyuan, and Wuyi Mountain National Parks.

Over the course of nearly 30 years between 1992 and 2021, light pollution increased, at times by sizable double digits. Most of the increase itself came either from outside of the park, on the park boundaries, or from settlements inside of the park. This study utilized space-time cube visualizations to provide a targeted cross section of lighting encroachment.

It’s been a bit since we had any good news about satellites, but here’s a positive story. A team of researchers looked at the strengths and weaknesses of SDGSAT-1’s nighttime light analysis abilities, and then paired their analysis with some real world conservation applications. The SDGSAT-1, for you at home who may be asking – what words am I speaking – is a Chinese research satellite launched back in 2021.

The satellite has a rather narrow field of view, so to say, in that it’s able to identify light sources down to 40 meters apart. Putting that in perspective, other previously available satellites were limited to ¾ of a km. The camera also sports some beneficial tools for researchers as it includes three spectral bands at blue, green, and red/near-infrared, and an all encompassing band. This enables researchers to discern types of light sources. I will add that the satellite is not able to discern the directionality of light.

Per the article, thanks to the strengths of the data, conservation minded researchers should be applying this data to document the degree of light pollution exposure in designated ecological zones, monitor the success of dark sky preservation, and map, track, and preserve nocturnal wildlife corridors.

Now this is pretty neat. In 2021, Nevada Senate Bill 52 gave the Nevada Division of Outdoor Recreation the task of implementing a dark skies certification program, which officially came into effect late last year. Last month, the Nevada Division of Outdoor Recreation and Travel Nevada released a digital ‘Nevada Dark Skies’ toolkit that offers homeowners, businesses, and governments advice on how to implement responsible lighting practices. As more motivation for following instructions laid out by the Department of Outdoor Recreation, Nevada organizations can then register as a Starry Skies Certified place, including as a School, Homeowner’s Association, Tribal Nations, Park/Conservation area, Municipality, or Business Association. It’s all part of a push by the state to capitalize on astrotourism.

Well, Nevada, you have some local competition. If you’ll recall the story of the stargazing train of Ely, Nevada, which describes itself as operating on ‘Sunset, Stars, and Champagne.’ Well, look out, Ely, The Oregon Coast Scenic Railway’s Moonlight Excursion Train put itself on the map recently.

The train ride rolls on for a round trip of three hours from Garibaldi to Wheeler and back. Now, it doesn’t appear to be as fancy as the ones we’ve talked about previously on this show that seemed downright ‘dreamy’ if I may appropriate that phrase. However, the moonlight excursion does take you around Tillamook Bay, which looks quite stunning in much the same vein as all of the Oregon coast.

If you at home are curious to what one of these rides costs, well, you might want to cover your ears. You can ride the train for a base cost of $65, then tack on an additional $10 for food or drink, and $20 for both. Experiences don’t come cheap, but you do get to ride with the top off, and that’s pretty neat.

Since we’re talking about fireflies, we might as well use this moment to transition over some ecology news, for which we have a very sizable amount this month. Reminder, supporters receive all news links, including any articles we don’t have time to cover here today. You can also learn more about artificial light at night’s impacts on the environment simply by venturing over to our website and clicking on our ecology tab.

First up, since we mentioned fireflies, let’s talk more about some flying insect friends. Out in Ohio, FirstEnergy shut off street lighting on several roads spanning three Ohio townships. The official reasoning was that, apparently, Mayflies, when killed en masse, extract an oily residue on roadways, thereby making it dangerous for drivers. Second to that, of course, was actual concern for mayflies, which serve as one of the basic food groups for many living things, including birds.

Mayflies tend to be found around healthy waterways, thereby their appearance is an ecologically good thing. The streets stayed dark for a couple of weeks until the hatching season passed.

According to researchers at Lund University, we have a daytime bias against nighttime pollinators. Researchers cite less scientific attention to bats, moths, and nocturnal butterflies. I bet that you at home may not have known that there were even such things as nocturnal butterflies – I’m not sure I did, quite frankly!

From Ecology Letters, they performed a meta-analysis covering 135 studies and found that 90% of the 139 plant species looked at didn’t care if it the pollinator was working the dayshift or the night shift – the plants just wanted some pollination! Which means, in the eyes of plants, pollination shouldn’t be limited to our own biased diurnal understanding of the world!
Staying on pollinators, according to a new report put out by the University of Reading’s Bee: Wild, light pollution now ranks number 9 on the list of dangers for pollinators. Per the report, “studies show that artificial light disrupts many stages of a moth’s life, affects key behaviours and can reduce pollination visits to flowers by 62%.”

We have to move on from pollinators. I know many of you listening to the show are fans of prior guest John Barentine. I have one of his articles on our ecology page. We weren’t able to include it in this episode.

However, here’s one that doesn’t regularly get talked about: how does artificial light at night impact plants? In particular, anyone who’s worked in conservation will recognize this plight – the effectiveness of certain invasive plants to overtake an area completely. A study in the Journal of Plant Ecology found that artificial light does impact the success of invasives.

The study used a control without light, a 15 lux lamp (say a hallway light), and a 30 lux lamp (a parking lot level of light). The color temperature of the lights was 6500K, which is a bit unrealistically cool, unless you happen to live in a community that already uses 5000K.

On biomass accumulation, invasives grew significantly under 30 lux, while natives witnessed a decrease. At 15 lux, they both experienced growth. Not surprisingly, both sets of plants performed better from a photosynthetic standpoint under the low level of lighting, though again, when we look at the higher levels of light, invasives benefited and natives, for some reason, declined. Artificial Light at Night somehow appears to be correlated with the invasive plant’s efficiency pertaining to nitrogen use. All of this leads to a clear advantage for the invasive set of plants.
The other impact of artificial light at night that most people find incredulous involves its impact on mammals. A meta analysis in Frontiers looked at evidence for light pollution’s effects on non-flying European mammals over 48 articles. The paper found that mammals suffer from circadian rhythm disruption, including phase shifts of their natural activity hours, changes in melatonin and reproductive hormones, breeding/hibernation mismatches, reduced sleep duration, and more.
Typically, we want to shine the lights down, but what if shining the LED lights on windows would reduce bird deaths? The theory sits on lighting up the UV coating of modern window glass. A team at Utah State University shined ultraviolet LED lights onto such windows from flag poles outside. According to NPR, this impact reduced bird deaths from 11 a month at a certain location to zero! So maybe the solution is actually to shine a light on the problem!
I will note that the researchers are in need of funding, so this is not a fix to be implemented anywhere anytime soon.

Finally, I want to end tonight with something lighthearted, unless you’re a songbird that is! In New Jersey, a hawk has mastered traffic lights – something many of its human neighbors still have yet to figure out. The Cooper’s hawk pieced together how long the audible crosswalk sound would backup traffic at a light, enabling cover for hunting mourning doves, house sparrows and starlings. This all occurred during the morning commute, requiring the hawk to have a precise mental image of the neighborhood, for which it skillfully navigated 90 degree corners and houses to attack its prey.