June 2026: Let Bats Be Themselves!, Light Pollution News

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This Episode:

Hey there, it’s Light Pollution News! This episode, I welcome three great guests: Author and naturalist Charles Hood; from the Soft Lights Foundation, I welcome back Mark Baker; and, out and about, starting his own thing, I welcome back Night Light Consulting’s Ken Walczak!

This episode, we talk bridges, some good, some… maybe not so good. And…headlights…have we been down this road before? You’ll have to listen to find out! Oh…and we have some ecology news this month; it’s a bit bat laden!

All this and much more in this episode of Light Pollution News!

Host:

Guests:

Ken Walczak

Ken is the founder of Night Light Consulting, a Board Member for Dark Sky International, and co-led the designation of the largest Urban Night Sky Place, the Palos Preserves!

Mark Baker

Mark Baker has a Bachelor of Science in Electrical Engineering from the University of California, Santa Barbara. Mark was a computer programmer for 20+ years and a middle school math teacher for 10+ years. Mark has been involved in the effort to protect people from LED light since 2016. Mark founded the Soft Lights Foundation as a 501(c)(3) non-profit registered in the state of Oregon in 2021. The Soft Lights Foundation is now one of the world’s leading advocacy groups for the protection of people from the harms of Visible Light radiation emitted by Light Emitting Diodes and for the protection of the natural night as a resource.

Charles Hood

Charles Hood has been a factory worker, a ski instructor, a dish washer, and a nature guide in Africa. He later went on to receive an MFA in poetry from UC Irvine, studying with Nobel Prize-winner Louise Glück. He is currently Professor Emeritus at Antelope Valley College.

Hood has published 23 books, including Wild Sonoma, with a foreword by Jane Goodall, and A Salad Only the Devil Would Eat, which was named the Nonfiction Book of the Year by the editors of the Foreword book review. His books about the world after dark include Nature at Night, from Timber Press, and Nocturnalia, Heyday Books in Berkeley.

Prior to these, his book Wild LA was named a Nonfiction Book of the Year by the California Association of Independent Booksellers. It has a 4.9 star rating on Amazon and is in its 5th printing.

Nature study has taken him across all fifty states and to eighty countries, from New Guinea to Madagascar, and to the South Pole. During these journeys, Charles has encountered 6,500 species of birds and over 1,000 species of mammals.

Along the way, he has been lost in a whiteout in Tibet, contracted (and survived) bubonic plague, been charged by a musk ox, and published over 800 photographs.

He is currently working on an essay about Confederate monuments, an essay about the history of panorama photography in the American West, an essay about bristlecone pines, and a poetry book that is a history of Lewis and Clark that is set in outer space. Later this summer, his oak tree book titled Acorns in a Nutshell will be published by Timber Press in Portland, Oregon. Charles owns thirteen headlamps, flashlights, and spotlights, and he currently lives in the Mojave Desert with two dogs and 5,000 books.

Full Article List:

1. Finland’s longest bridge reaches completion in Helsinki, Starr Charles, Dezeen.
2. The Bay Lights Come Back On Tonight After Three-Year Hiatus, SF Gate.
3. Lighting the Sound, Form.
4. Artificial light at night and invasive signal crayfish alter aquatic‐terrestrial food webs, Functional Ecology.
5. Light and ultrasonic noise pollution displaces trawling Daubenton’s bats, Scientific Reports.
6. Assessing the benefits of part-night lighting on a tropical bat species endemic to Reunion Island, Biological Conservation.
7. A Novel Light-Induced Collective Circular Movement inArmadillo sordidus Isopods, Ecology and Evolution.
8. Time after time: a quarter century of progress in plant circadian biology, Stacey L. Harmer, NJP.
9. Architects in the Dark: Nocturnal Behavior and Evolutionary Trade-Offs in Social Insects, Jia Wu, Nocturnal Animals – Adapted or Inherited Plasticity.
10. From gas lamps to LEDs: The 100-year war on headlight glare, Kris Culmer, Autocar.
11. Intelligent automotive lighting: the car’s new language, Matthew Beecham S&P Global.

Light Pollution News: June Highlights

Helsinki’s Kruunuvuori Bridge Sets a New Standard for Responsible Bridge Lighting

Finland’s longest and tallest bridge, the Kruunuvuori Bridge, stretches three quarters of a mile and rises 443 feet above Helsinki, designed by WSP and Knight Architects as a rail and pedestrian-cycling crossing. Its lighting system uses targeted, shielded fixtures that illuminate the footpath without directing light upward into the sky, outward toward the shoreline, or downward onto the water below. The design also accounts for glare reduction for walkers, residents, and passing ships, and includes adaptive brightness controls that respond to both time of night and atmospheric conditions.

San Francisco Bay Bridge Relighting Sparks Environmental Lawsuit Over Bypassed Review

Nonprofit Illuminate, led by founder Ben Davis, raised $11 million in private donations to relight the Bay Bridge suspension cables after the original installation by artist Leo Villareal degraded in 2023 following approximately a decade of operation. The replacement design doubled the original LED count to 50,000 fixtures and was executed in partnership with Musco Lighting, the same supplier endorsed by Dark Sky International for sports field applications. Conservation group Soft Lights, backed by the Golden Gate Bird Alliance, filed suit against the Bay Area Toll Authority, the Metropolitan Transportation Commission, and Caltrans for bypassing a mandatory environmental review, with biologist Robert Hamilton’s independent report endorsed by Dr. Travis Longcore confirming the legal conclusion that skipping the review was indefensible. [Light Pollution News reached out to Musco Lighting for a comment; to which Musco Lighting did not respond]

“Lighting the Sound” in Western Australia Claims Title of Largest Outdoor Light Installation Ever

Artist Kari Kola staged Lighting the Sound over three weekends in March across Torndirrup National Park and the Vancouver Peninsula near Albany, Western Australia, using 750 LEDs spanning 12 kilometers alongside fifteen Ayrton Mamba laser fixtures. The installation was co-designed with guidance from the Menang First Nation people to honor the cultural history of the region, and its color palette was required to pass review under the Australian National Light Pollution Guidelines for Wildlife. The exhibit operated for only a few hours each evening across its run.

Nocturnal Insect Navigation Strategies Reveal a World Built Without Light

A chapter from the edited volume Nocturnal Animals: Adapted or Inherited Plasticity examines how termites, ants, and honey bees have each evolved distinct strategies for operating in darkness. Termites navigate entirely through chemical pheromones and vibration, with soldiers drumming tunnel walls as an alarm system, while many nocturnal ant species have enlarged eye structures enabling navigation by polarized moonlight, starlight, and the Milky Way used as a celestial compass. Honey bees divide their activity across the clock, foraging by day using polarized light and spending nights in the permanent darkness of the hive guided by touch, temperature, and chemical signals, with some crepuscular species having additionally evolved enhanced low-light vision for twilight foraging.

Artificial Light Reduces Bat Foraging Activity by 43% at Source in Danish River Study

A 30-night field study published in Scientific Reports measured the foraging behavior of wild Daubenton’s bats at a river site in Odense, Denmark, using nine acoustic recorders spaced at set intervals from designated light and noise sources. Artificial light reduced bat echolocation activity by 43% directly at the source and by 23% at distances up to 20 meters away where light levels fell below an estimated 1 lux, while ultrasonic noise produced a comparable 49% reduction at the source but dissipated beyond roughly 10 meters. Bats recovered within approximately one minute after lights were extinguished, while recovery from ultrasonic noise required an additional 2.4 minutes.

Earlier Streetlight Shutoffs Shown to Reduce Bat Activity at Lit Sites on Réunion Island

Researchers publishing in Biological Conservation used a natural experiment on Réunion Island in the Indian Ocean, where a conservation campaign shifted existing streetlight switch-off times roughly two hours earlier from approximately 11 PM to 9 PM. Across 60 sites observed over 13 nights, bat activity at lit locations in the early night was 62% higher than at unlit sites, rising to 73% higher during early morning lit hours, as insects drawn to streetlights created concentrated foraging opportunities. The findings add to growing evidence that part-night lighting strategies, while imperfect, can reduce but not eliminate the ecological disruption caused by artificial light at night.

Streetlights and Invasive Crayfish Reshape Spider Diets in Riparian Ecosystems

A study in Functional Ecology used 16 artificial stream units with adjacent riparian areas to assess how 4000 to 4500K white artificial light at approximately 20 lux and invasive signal crayfish independently and jointly affected the diets of riparian spiders and crayfish. Artificial light expanded spider dietary niche width by 14% when applied alone and by 13% in combination with crayfish, meaning spiders consumed a more diverse prey range rather than simply more food. Crayfish reduced spider population density by 27% on their own, but under artificial light shifted their own diets heavily toward midges and amphipods, which comprised roughly three quarters of their intake compared to about half without light present.

25 Years of Plant Circadian Research Highlights Vulnerability to Light Pollution

A perspective piece in NPJ Biological Timing and Sleep synthesizes a quarter century of plant circadian biology research, arguing that every major dimension of plant growth and development is regulated by the internal circadian clock to some degree, including hormone signaling, drought and cold stress responses, starch metabolism, disease resistance, flowering time, and pollinator attractiveness. Plants whose internal clocks were mismatched to external light-dark cycles demonstrated slower growth and lower survival rates compared to those with synchronized clocks. Although the paper does not directly address artificial light at night, its findings underscore how disruption of the light signals plants use to calibrate their clocks may produce cascading consequences for plant health and ecosystem function.

Thousands of Pill Bugs Form Mysterious Circular Processions Around Streetlights in Israel

First observed by amateur naturalists at two sites in northern Israel between 2021 and 2025, a phenomenon published in Ecology and Evolution documents thousands to tens of thousands of pill bugs marching in organized circular rings around streetlights at night. Researchers ruled out magnetic fields and UV light as causes, finding that vertically oriented white light projecting a circular pattern onto the ground was the only stimulus that reliably reproduced the full circular procession across three independent trials, while a horizontal beam caused clustering without circular motion. The authors note the behavior has so far been documented only in this one species, only during summer nights, and with a population that skews roughly 80% female and largely egg-carrying, leaving the underlying mechanism and adaptive significance unexplained.

Headlight Glare Complaints Are Nothing New, With Britain Regulating the Problem as Far Back as 1937

A piece from Autocar traces the history of automotive headlight glare complaints back to the early 20th century, when headlights rated at 21 candlepower (roughly 13 times dimmer than modern equivalents) still generated enough public frustration to spawn a cottage industry of shielding, reflectors, and shutters. France mandated yellow headlights in 1933, and the UK enacted its first anti-glare automotive regulation in 1937 only after approximately 30 years of sustained public complaints. Contemporary automotive lighting has since expanded its role beyond safety to include branding, with some vehicles featuring animated lighting sequences and displays during charging.

Light Pollution News: June Read Along

[Light Pollution News reached out to Musco Lighting for a comment; to which Musco Lighting did not respond]

Let’s kick the show off right! Let’s talk about something that I know is everyone’s favorite topic – bridge lighting! Over in Helsinki, the Kruunuvuori Bridge debuted. It’s both the longest and tallest bridge in Finland, coming in at ¾ a mile in length and 443 feet (135m) in height. The bridge isn’t designed for drivers like you or me; rather, it’s a rail bridge designed with pedestrian/cycling pathways. As if that isn’t novel enough to my North American ears, there’s an even more impressive design tidbit!

The bridge was designed specifically to minimize light pollution! How can this be? Well, as I’m sure you at home are aware, all it takes is a little forethought to make something that isn’t completely irresponsible and wasteful!

The bridge utilizes targeted and shielded fixtures…I know… shielding’s a pretty novel concept, right? So the footpath is completely lit, but that light isn’t aimed upward or outward toward the shore or water. The fixtures themselves were purposely positioned to minimize glare for a variety of users, including walkers, nearby residents, and ships below. And as if that wasn’t enough, the bridge does have decorative lighting, though from pictures you can clearly see that the light remains on the bridge, not extending far out into the water, nor upward into the sky. The bridge lighting is able to adjust to both the time of night and to the atmospheric conditions for optimal brightness, not careless or excessive brightness.

The bridge was designed by two companies: WSP and Knight Architects.

Well, don’t worry – over here in the States, by and large, we don’t have to worry about such forward thinking! Or do we?

There is this group, Illuminate, led by its founder Ben Davis, which we’ve talked about previously on the show. Davis did something that I’m quite jealous of, and that, of course, is to raise $11M in private donations – including some big one-time drops (think $1M) amid the small (think $2) donations. All of this was raised to relight the Bay Bridge connecting San Francisco to Oakland, California. For those of you not familiar with San Francisco, this is not the Golden Gate Bridge, to which the central tower masts are lit, not the cables.

Mark, before I open this up, let me run through the backstory and timeline here. Roughly 15 years ago, Davis got the idea to pitch decorative bridge lighting to California’s Department of Transportation (Caltrans). At that time, Davis ran a PR firm, Words Pictures Ideas, that the Department of Transportation contracted with. He somehow connected with artist Leo Villareal. Villareal ended up designing the initial decorative lighting for the bridge which debuted about a decade back. The decorative lighting then, and now really, involved a simple idea – to light the suspension cables from the road to the horizontal cable. That became the iconic look for the Bay Bridge. Fast forward to 2023, the bridge lights essentially ran their course given the weather in San Francisco.

Now, after raising the needed dough, Davis again contracted with Villareal. In March, half of the anticipated 50k LEDs were installed and activated on the Bay Bridge. This new replacement count is double that of the original design.

I want to note the main player here, because the name will raise an eyebrow. The key partner for Villareal’s reinvisioning of the Bay Bridge involved Musco Lighting. Yes, the same provider endorsed by Dark Sky International for its sports fields lighting, and the provider who debuted responsible lighting at the US Open. Over on Musco’s page featuring the Bay Bridge relighting design, rest assured, there’s no mention of ‘responsible lighting’, nor the word ‘ecology’, and, it goes without saying, ‘light trespass’ or ‘light pollution’. Per Ben Davis, the intent of the new lighting is ‘so people can see it not just from San Francisco and the North Bay, but as a matter of aesthetic equity, to communities all around the Bay.’

Of course, some of you know that the story didn’t end there. Mark, you raised up your hand and said…hold on…I get that you want to help bring joy to the community, but this sounds like you’re asking to essentially upsize the original ecologically careless bridge lighting! You had allies jump on board, including the Golden Gate Bird Alliance, which also requested timers and dimmers for the new lights, both of which I didn’t find anything indicating that Musco or Davis responded to.

So, you, via Soft Lights, took a trio of groups, the Bay Area Toll Authority, the Metropolitan Transportation Commission, and the California Department of Transportation, to court, citing a failure to provide a mandatory environmental review. You called in the services of Robert Hamilton at Hamilton Biological. Dr. Travis Longcore stepped in to independently review the report and found Hamilton’s work to be accurate and endorsed the legal conclusion that the environmental review bypass was indefensible.

Before we go too far, there was another notable lighting exhibit. This one that took place in the land down under, put on by Kari Kola. It’s even considered the largest outdoor light installation ever undertaken. It’s an exhibit called ‘Lighting the Sound.’ It took place over three weekends back in March. The area specifically lit was the hills of Torndirrup National Park and the Vancouver Peninsula around Albany. The official purpose was to honor the cultural history of the region, to which the First Nation peoples called Menang. In fact, it was co-designed with First Nation guidance.

Kola installed 750 LEDs shining over 12 Km with fifteen laser mambas (think dense event spotlights). Some of which shot up into the land and others shot up over into the sky. The color selection had to pass muster with the Australian National Light Pollution Guidelines for Wildlife, which they apparently did, despite the fact that Kola used green as one of the major colors. This exhibit only remained lit and active for a few hours each evening.

This is interesting. I came across this chapter out of the edited volume Nocturnal Animals — Adapted or Inherited Plasticity. It looks at some less than appreciated architects of our nighttime environments, that being termites, ants, and honey bees.

Termites don’t use light. Instead, they navigate their world through chemical pheromones and vibration. This activity reinforces the most efficient paths through positive pheromone feedback loops. There’s also a vibration alarm system complete with soldiers headbutting tunnel walls to create a drumming sound when a nest is breached. They live a whole life without the need for light or much detailed vision.

Ants, on the other hand, use their eyes but have an important feature. Many nocturnal ant species have enlarged eye structures that capture greater amounts of dim light. As we saw last month, some can navigate using polarized moonlight, starlight, and even the polarized light of the Milky Way, essentially using this light as a celestial compass. This visual system works in tandem with chemical trail senses. This enables ants to operate across a wide range of light conditions and environments rather than being locked into a single vision strategy, like termites are.
And then we have our fan favorite, the honey bees. These guys split the clock. Daytime involves foraging with polarized light for navigation. Nighttime is spent in the hive, which sits in permanent darkness. Worker bees process nectar, build comb, and care for larvae guided entirely by touch, temperature sensitivity, and chemical signals. Some crepuscular species have additionally evolved enhanced low-light vision to exploit the twilight, accessing night-blooming flowers with next to no competition.

From Scientific Reports, a team looked at how artificial light and ultrasonic noise pollution affected the foraging behavior of wild Daubenton’s bats at a river site in Odense, Denmark. The study was conducted over 30 nights. They used nine acoustic recorders deployed at a predetermined distance interval from a designated light or noise source. Researchers measured bat echolocation calls per minute as a proxy for foraging activity.

Light was found to reduce bat activity by 43% directly at the source and further reduced activity by 23% as far as 20 meters away, where light levels were estimated to drop below 1 lux. On the noise front, the team utilized ultrasonic noise, which produced a similar 49% reduction at the source, but this dissipated more quickly, becoming undetectable beyond roughly 10 meters away. Bats recovered within approximately 1 minute after light was turned off, while noise required an additional 2.4 minutes of recovery time.

One note is that light intensity was not directly measured in the field but rather extrapolated from controlled dark-room calibrations.

From Biological Conservation researchers asked whether part-night lighting can reduce light pollution impacts. Specifically, they took aim at the practice of switching off streetlights during low-activity hours to see if this provides any benefit to the Réunion Island free-tailed bat. Researchers used a natural experiment on Réunion Island in the Indian Ocean, where an annual conservation campaign moved existing switch-off times approximately two hours earlier, from roughly 11 PM to 9 PM.

They looked at 60 sites (split evenly as lit and unlit) over 13 nights. The results indicate that light played a significant role in luring bats to the fixtures for foraging on collected insects. Bat activity at lit sites in the early night was 62% higher than at unlit sites. And 73% higher for areas lit in the early morning hours compared to unlit sites. The light intensity at individual streetlamps was not measured.

This month, we have yet another case of how artificial light at night, in this case, streetlights, restructure the food chain in ecosystems. A study out of Functional Ecology assessed artificial light at night and invasive signal crayfish as they relate to the diets of riparian spiders and crayfish. The study looked at 16 artificial streams with adjacent riparian areas. These units were randomly assigned to four treatments, including a control, artificial light at night only, crayfish only, and a combination of crayfish and artificial light at night. The artificial light at night included 4000–4500K white light mounted 1 meter above the water surface, emitting approximately 20 lux. With 20 lux being an intensity comparable to typical urban street lighting.

The study found that aquatic sources made up the majority of spider diets across all treatments, ranging from 56% in the control up to 64% under the crayfish-only treatment. As this pertains to artificial light at night, light expanded the spider’s dietary niche width by 14% under artificial light alone and by 13% when light was paired with crayfish. This means that spiders were eating a more diverse range of prey, not simply more food overall. Also, the combined treatment produced a weaker than expected interaction, suggesting that the two stressors partially offset one another rather than compounding. The crayfish only treatment reduced spider population density by 27%, which is how crayfish most affected the food web. Under artificial light, crayfish themselves shifted their focus toward midges and amphipods, which together comprised roughly three quarters of their diet under light versus about half without it.

I saw this very educational perspective piece out of NPJ Biological Timing and Sleep. The write up offers useful context for understanding why plants are vulnerable to light pollution. It reviews 25 years of research in plant circadian biology, with the thesis being that every aspect of plant growth and development is modulated by the circadian clock to some degree. That being hormone signaling, drought and cold stress responses, starch metabolism, disease resistance, flowering time, pollinator attractiveness, and more. As we’ve heard previously, plants whose internal clocks were mismatched to environmental light-dark cycles actually grew more slowly and had a lower survival rate than those with matched clocks.

Now, this piece isn’t talking about Artificial Light at Night, and it never really mentions it, but I think you at home can make the simple connection that the primary signal plants use to calibrate that clock is light itself. As we’ve seen in prior studies on this show, if light is the input that synchronizes these systems, and artificial light at night desynchronizes that input, some plants struggle to adapt to the non-stop lit environment we hoist onto them.

And lastly, how about this? From Ecology and Evolution, some folks noticed thousands of pill bugs forming large, coordinated circular processions at night around streetlights in northern Israel. First spotted by amateur naturalists at two sites between 2021 and 2025, the behavior involved thousands to tens of thousands of individual pill bugs marching in organized rings. To investigate what drove this, researchers tested three potential causes: magnetic fields, UV light, and white light. A magnet placed near an active instance did nothing. UV light attracted a small fraction of individuals but produced no circular motion. White light, ahah – that was the key, but only when oriented vertically, pointing downward. A horizontal white beam caused isopods to cluster but not circle. The vertical beam reliably produced the full circular procession across three independent trials, suggesting the pill bugs are walking the perimeter of the circular lit zone projected onto the ground.
Some things to note with this piece: it is based on a handful of events at two sites over several years, so the statistical foundation is narrow, and the researchers acknowledge they cannot yet explain why this behavior appears restricted to this one species or to summer nights specifically. Or even why the sex of these pill bugs is largely female (80%) and largely carrying eggs.

Before we go tonight, I have this piece from Autocar. It’s funny how history, if not repeating in near verbatim fashion, rhymes quite eerily!

What if I told you that the headlights are too dang bright! What if I told you we need the government to do something about them! What if I told you that Britain’s government has received complaints upon complaints regarding headlights! And…what if I told you that this all occurred in the first third of the 20^th century?!

Back then, headlights were 21 candlepower, roughly 13 times dimmer than today! The glare put off by the lights spurred a cottage industry of shielding, reflectors, and shutters. In 1933, France’s government even mandated that the color of the headlights be yellow! Then by 1937, the UK passed its first anti-glare automotive requirement. It took 30 years of complaining to finally get some regulatory action!

In that time, one article from the S&P notes that front and rear lighting has evolved quite a bit. The role isn’t solely about safety and seeing but also about branding and creating personal connections. For instance, some cars put on lighting displays while charging. Others have animated sequences to greet drivers.