Written by Joshua Sokol
Translation Yang Fan (Senior Engineer, National Astronomical Observatories, mainly engaged in stellar physics and astronomical observation technology)
Astronomers were among the first to notice the brightening of the night sky, and worsening light pollution was a major hindrance to their observations. But the harm of light pollution is by no means limited to not seeing the stars and the Milky Way, and countless animals throughout the ecosystem are suffering from it.
Many stories tell us that light pollution can be recovered. With the rise of the awareness of night protection, humanity is recovering the lost starry sky.
False twilight
The city of Tucson, Arizona, USA, is like a bubble radiating light, eating away at the eastern sky and the shoulders of Orion. The slightly dimmer lights of Interstate 10 snake snake out of this glow, stretching 160 kilometers north and connecting with the glare of Phoenix. And to the south, across the border, another luminous semicircle of lights in the Mexican city of Nogales can be faintly seen.
All this light pollution is a deadly threat to the high-profile astronomical observations on Kitt. For decades, astronomers have taken various emergency measures to try to slow or even reverse its spread. For astronomers, the boundary of each halo is a tug-of-war front, expanding or shrinking with the victory or defeat of each skirmish; Local policies, countless collective attempts (or collective helplessness), the proliferation of advertising signs and street lights, and the imperfect dark night overhead are proof of all this.
In this way, light pollution is still spreading. An astronomer at Kitt Peak told me that hours after sunset, it takes twice as long to resolve a target source under conditions with strong stray light than it would normally be. While the increasing frequency of wildfires linked to global warming may pose an immediate risk to telescopes placed nearby, brighter nights are a greater threat to astronomical observations.
Many of the ecological disasters of our time are difficult to see with the naked eye: for example, species are disappearing, carbon dioxide is increasing in the air by parts per million, and marine life is devouring microplastic particles. This is not the case with light pollution. Although telescope astronomers may have been the first to actually notice it, its impact is not limited to astronomy. Over the past decade, biologists have discovered that nighttime lighting, in addition to a huge waste of energy, actually greatly invades animals, plants, and the ecological relationships that bind the world together. The impact extends far beyond cities and involves all regions of the globe. Kevin Gaston, a well-known conservation biologist at the University of Exeter in the UK, pointed out: "We need to think about this as seriously as we treat plastic pollution and the impact of global climate change. ”
However, scientists remain convinced that people don't have to make much sacrifice to mitigate the problem of light pollution. As the scope of the problem continues to be revealed by new research, potential solutions become clearer. Just like chimney exhaust and factory wastewater, light pollution can be understood and treated. The sooner we act, the better. Satellite data shows that more than three-fifths of Europeans and four-fifths of Americans live under severe light pollution that makes the Milky Way invisible to the naked eye. Other analyses show that the artificially lit areas of the Earth's surface are still expanding outward at a rate of about two percent per year, eating away the remaining night sky like cheese. Although the latest LED technology has made lighting cheaper and more energy-efficient than before, consumers don't seem to be pocketing these savings or reducing carbon emissions. On the contrary, people are turning on more and more lights.
Light pollution is not inevitable. The starry dark night sky is already the exception, but it can once again become the norm, reducing the burden on the ecosystem while bringing magnificent astronomical wonders back to people's daily lives. In fact, many continents have drafted laws and regulations aimed at achieving this goal. However, any solution depends more on social than scientific questions: can we continue to conduct the research necessary to properly define and deal with light pollution? How much night lighting is what we need? The most critical and maddening thing is, does anyone really care about all this?
The helplessness of moths to the fire
What kind of impact would it have on the ecosystem to let the world bathe in a false twilight forever? This has always been difficult to assess. For some creatures, light is an irresistible temptation; For other creatures, it's a repulsive force field. The time, wavelength, direction, and intensity of illumination and the structure of the person's eyes play a role. And, unlike mercury in tuna or DDT residues in bald eagles, photons do not leave a long-lasting and measurable chemical trace. Taken together, though, studies of at least 160 species provide ample evidence that artificial light sources send a series of confusing and anachronistic signals to natural creatures – don't sleep! Hide! Go hunting! Fly this way! Adjust your metabolism!
One morning last May, I drove to a cattle ranch in rural North Carolina to meet Murray Burgess, a graduate student at North Carolina State University. She had previously hung small Christmas lights by the swallow's nest on the rafters of the barn. She climbed a ladder and pulled out the chicks that looked like wriggling pink dinosaurs one by one, gently clutching them in her warm palms and conducting a series of tests one by one. She offered to let me hold one too, but I was afraid that I would squash it, so I refused. She said the parents of the chicks were unaware of removing their nests from the light, which caused damage to the chicks' bodies. Compared to neighborhood chicks that grow up in no light, a small light bulb makes these chicks stunted, underweight and even diabetic. Burgess lamented to me, "The effect of light deep into the cell is really crazy." ”
This mechanism of harming a single barn swallow baby also applies to entire species and even ecosystems. On the shore, artificial light causes reef-building corals near the surface to stop spawning at once, turning what should have been a synchronized burst of fresh life into useless and untimely eggs and sperm. In the United States alone, hundreds of millions to a billion birds die each year after hitting windows, many of them summoned by indoor lights.
The consequences for insects are particularly dire. Moths keep pounce on the light bulb, but scientists still don't understand why. The cricket's chirping is becoming decoupled from the rhythm of day and night transitions. In rural England, research shows that caterpillar populations are plummeting in roadside hedges illuminated by LED street lights. It is almost certain that light pollution is accelerating the insect apocalypse, and the variety and abundance of insect organisms on Earth will be drastically reduced, although few studies have really focused on this cruel ending.
Not only that, but the effects of light also ripple through other living systems that are more closely related to us. In a 2017 experiment, scientists wearing night-vision goggles to observe cabbage plants confirmed that ambient light hindered the activity of nocturnal pollinators. The inability of pollinators during the day to compensate for this deficiency has led to fewer fruits produced by plants, suggesting that the effects of brightening at night may eventually be reflected on supermarket shelves. The light at night may daze our favorite insects, but it can make the insects we despise passionate: The Egyptian spotted mosquito, which causes more than 400 million cases of dengue and Zika infections each year, seems to bite more aggressively encouraged by artificial light, as does another mosquito that transmits West Nile virus.
Polluted sleep
In the past, only professional journals documented such effects in a single biological way, without linking broad research projects. It wasn't until the late 90s of the 20th century that a pair of graduate students in Los Angeles began to collect and build archives of such events, calling themselves environmental "troublemakers". Katherine Ritchie, a law to ecology student, tried to recommend her doctoral research project on light pollution and wildlife to 7 academic departments and sought funding. As a result, she was completely ignored. "All I hear is generally 'you're going to have any results,' something like. But Ritchie and her husband, Travis Longcore, didn't give up, and they organized a groundbreaking academic conference on the subject.
In their 2002 conference, 2004 review paper, and subsequent books, Ronclé and Ritchie deliberately avoided another parallel area of research—the impact of brighter outdoor and indoor light on human health. (We've long known that nighttime light is associated with a myriad of problems, from obvious sleep disturbances to the more surprising increased risk of breast cancer.) But it's unclear how much of that comes from outdoor light pollution, and how much comes from our glowing displays and other interior furnishings. Even so, journalists and the public have begun to realize that light pollution is real pollution from an ecological point of view. By 2011, many of Europe's most influential ecology labs, including Gaston's lab, were taking up the topic and publishing their own findings and literature reviews. As of this year, Ronclay and Ritchie's review paper has been cited more than 1,500 times.
A significant portion of these results relate to the most common light pollution: a single strong light source as harsh as the LED headlights on a new SUV, such as shining your scene. Recently, however, some people have begun to pay attention to the halo effect I saw at Kitt Peak, which is subtle but widespread. The most detailed recent ecological studies have shown that such low levels of background light pollution can have biological consequences even if no specific light source is visible.
In 2021, an experiment was conducted under a dome floating in a lake in Germany and showed that the bright night sky alone caused a decrease in melatonin, a hormone messenger associated with the night, in Eurasian bass. Another paper last year showed that South African dung beetles typically watch the galaxy guide itself to bury droppings in the grasslands, a low-level but essential task that brighter nights can make it disoriented. In addition, a 2021 study led by Longclay showed that similar low-intensity light on California's beaches prevents plovers (a migratory bird) from roosting here and prevents grunions from coming ashore to spawn.
All of this is critical because the skylit dome can be seen from hundreds of miles away along state and even national borders. Studies have shown that it can lure migratory birds and insects across the entire region. Even in rare corners of Earth that have not yet been affected by the skylight dome, organisms seem to respond to faint changes in lighting. In the Arctic Ocean, for example, plankton rises and falls daily despite the sun always below the horizon, and artificial light from fishing or mining can also disrupt this system.
The darkness required for astronomical observations
Two weeks before my stay on Outer Kitt Peak in Tucson, I stood in the pine forest around the Lowell Observatory in Flagstaff, Arizona, shivering with the cold night wind and looking up at the lunar eclipse. As the Earth's shadow glides across the lunar surface, the deep sky becomes darker and the starlight brightens, like an image editor fiddling with the contrast in a photo.
The most memorable part of the whole experience, though, was when you overlooked the night view of Flagstaff Town, where there was hardly any light other than a few traffic lights. So you wink, trying to convince yourself that you're overlooking a sleepy seaside village, not a mountain town of 75,000 people hoping to attract visitors en route to the Grand Canyon. It looks like a little corner forgotten by modernization, somehow learned to close its eyes and fell asleep.
To date, the most successful cases of defending the dark night have occurred near expensive astronomical observation facilities. In 1958, around the same time that Rachel Carson was inspired by modern environmentalism and writing Silent Spring, a rotating spotlight beam from a car dealership began disrupting the observation environment at the Lowell Observatory. In response, the town of Flagstaff enacted the world's first ordinance on light control. Arizona has since been at the center of the Save the Night movement.
Two years ago, a few hundred kilometers to the south, astronomers and guides from the surrounding Tohono Odham tribe rode to Kitt Peak outside Tucson, exchanging Western and indigenous starry sky stories around a campfire at the top of the mountain. Soon, the federal government leased the land permanently from the tribe, and larger and better telescopes were erected on top of the hill.
As light pollution intensified in the nearby city of Tucson, astronomers at Kitt Peak turned to allies like Tim Hunt. The doctor grew up watching the Milky Way under elm trees in the suburbs of Chicago, and then helplessly watched the artificial light source fade the Milky Way like the Dutch elm disease caused trees to rot. In 1988, Kitt Peak astronomer Dave Crawford joined Hunter in forming the International Dark Night Society (IDA) in hopes of creating a broader cooperative alliance that would include their allies in Flagstaff.
Over the years, as advocates have watched the night fade away, the tools and techniques needed to track it have advanced. Light pollution models evolved from equations stuck on pen and paper to computer simulations of ray tracing. Advanced wide-angle cameras have made it easier to measure skylight from the ground, and satellite imagery is beginning to show spider web-like bands of light spread across the globe. The general trend is discouraging: The deeper researchers dig into the problem, the worse it seems to appear.
Crime and darkness
Will light pollution surely increase as our cities grow? The International Dark Night Society and associated researchers disagree. Often, crime prevention tends to be an excuse for cities to evict the night. But how effective is this approach? Perhaps the most definitive evidence that lighting can curb crime comes from 2016. Criminologists placed about 400 lighting towers the size of basketball hoops in public outdoor spaces in New York City housing projects. The blue-and-white lamps, powered by their own portable fuel generators, were also turned on during the day — eventually showing that outdoor crime around the lighthouse had dropped by about a third.
But scholars of Night Conservation point out that these lighthouses are far brighter than mere street lights. They also point out that any anti-crime policy that relies on exposing minority-majority communities to prison-like lights overnight should be morally questioned. In fact, throughout the continental United States, like other known pollutants, the burden of nighttime lighting tends to fall on the weaker groups: According to a 2020 study by sociologists at the University of Utah, black, Hispanic, and Asian-American neighborhoods tend to be about twice as lit as white neighborhoods.
Another common reason for flooding lights at night is road safety. But scientists believe that many brightness standards are driven by habit rather than science. In 2018, researchers at Heard University in the United Kingdom took a closer look at regulations in Europe and North America. They concluded: "Many of the current recommended brightness standards in road lighting guidelines have little credible empirical support." ”
Other lighting choices are down to industries and individuals, many of whom remain untouched or completely unmoved by the problem. Spend some time in the circle of night protection, and you'll hear the curse: when you suddenly see bad and wasteful lighting and realize it, you will no longer be able to pretend not to see it. (I got this feeling while walking around a neighborhood in Raleigh, North Carolina.) It occurred to me that a historical, predominantly white neighborhood was using darker amber street lights, while a neighboring prominent black neighborhood was installing more glaring white light fixtures. ）
Many people also use this curse as motivation to act. On the second day of watching the lunar eclipse in Flagstaff Township, Chris Lukingbull and I sat down for small talk at the local Dark Night Beer Company. Lukingbull was an astronomer at the nearby U.S. Naval Observatory and has been protecting the dark night in Flagstaff for 40 years. He knows the field of night protection and its progress better than almost anyone. The street lights here are dim orange because, as Lukingbull explains, blue light is more disturbing at night for most animals, including humans, as well as astronomical observers. This is because blue light with shorter wavelengths is more likely to scatter in the air, forming a localized light fog.
Lukingbull praised his town as a model and proof that the concept of night conservation can be replicated in other communities. In 2017, the U.S. National Park Service deployed an ultra-sensitive panoramic camera outside Cheyenne, Wyoming, which is similar in size to Flagstaff but does not have dark night protection regulations. Cheyenne is 14 times brighter than Flagstaff Town, while the halo around it is 8 times larger. Lukingboul says his strategy is simply to show people the stars and convince them to see that there is no irreconcilable contradiction between stars and social development. "Do I think the stars will eventually defeat light pollution? No doubt! "People are changing their minds, and people must change their minds." ”
In 1942, Nazi Germany sent a large number of U-boats across the Atlantic to hunt merchant ships on American shipping lanes. Cargo sank tons and drowned bodies washed ashore. It soon became clear that at night, submarine gunners selected targets by dark shadows in the glow over the coastline.
Elected officials and chambers of commerce in cities like Miami, Florida, were forced to dim the lights and turn off glitzy outdoor billboards. Obviously, this light pollution is already a matter of life and death. However, community leaders have dragged their feet on the grounds of economic problems, greatly reducing the effectiveness of collective efforts. The massacre at sea eventually forced then-U.S. President Roosevelt to issue an executive order mandating coastal blackouts. U-boat attacks have also waned as defensive patrols have intensified and communities within kilometers of the coast have severely restricted the use of night lights.
Rediscover the hope of the Milky Way
The pressure to dim the lights is increasing. Several U.S. states are reviewing laws that favor the protection of the night. The movement to turn off lights during bird migration season is also spreading across the United States. Last spring, for example, hundreds of downtown buildings in cities like Dallas and Houston, Texas, dimmed their lights. Since 2001, the International Dark Night Society has certified places that are undergoing dark night conservation – of course, Flagstaff is the first on the list – and more than 200 locations worldwide have been certified to date.
Bolder policies are underway in Europe. In France, a law passed in 2019 prohibits businesses from lighting decorative light signs all night; Germany has also developed a legal action to reverse the decline of insects, one of the main goals of which is to control light pollution. In the field of technology, LED manufacturers are also keenly aware of a new need and are introducing to the market dark night protection-friendly, downward-pointing, longer wavelength lighting devices. Berlin's Holker laboratory, which has completed complex experiments with lake skylight, has also developed a prototype lamp that operates in a wavelength range that does not interfere with most insects. Ecologist Jesse Barber told me, "What's exciting about this question is that it's recoverable!" "This is actually the common feeling of the entire Night Protection Group.
It's hard for people to care about things they've never seen before. Being able to see the Milky Way again—the awe flash bomb that all our grandparents and humans before us could see at any time—would be the biggest reward for limiting light pollution to us. Unlike the western United States, which can be summoned by modestly reducing the lighting, in the denser and brighter eastern United States, even the slightly worse galactic scene cannot be seen without driving for hours to an isolated dark corner.
Recently, I learned that there was a quiet, little miracle hidden in my little world: a new ghost firefly found in the old pine bushes near my house in Piedmont, central North Carolina. The male fireflies of this species light up for up to 30 seconds at a time, scribbling behind faint, floating messages, while female fireflies lie quietly below, silently responding with green answers.
In 2021, several citizen scientists discovered populations of this firefly in some of the state's most urbanized counties. Of course, they were there before anyone noticed. And they can easily go extinct because of the cement before they are discovered. An entomologist searching for the species, Clyde Sorenson of North Carolina, even stumbled upon a group in his own backyard. He timidly told me, "You know, I've been living there for 25 years. ”
So I drove to his driveway one night this spring. We stepped on the leaves, wore headlamps, and accompanied the call of a bullfrog to the neighboring woodland. As a new species, we don't know exactly when and how much of the year they appear. But we are convinced that darkness is necessary.
Obviously, fireflies are sensitive to light levels, which is the medium through which they communicate. Studies have shown that ambient light pollution can hinder fireflies from courting and even make some species too lazy to try. As we walked down the road that night, the lights of our mobile phones, the streetlights passing through the trees, the safety floodlights of our neighbors – all kinds of undesirable lights in the environment illuminated all possible hiding places and hindered our search for them.
That's when we saw three female fireflies curled up twinkling like misplaced stars, shimmering from gaps in the leaves that blocked the glare. They continued to glow for about half an hour, until at the end of that night's shift, when they disappeared into the night.
Guang Ming Daily (December 15, 2022, version 14)
Source: Guangming Network - Guangming Daily