Light Pollution Is Disrupting the Seasonal Rhythms of Plants and Trees (theconversation.com) 44
An anonymous reader quotes a report from The Conversation: City lights that blaze all night are profoundly disrupting urban plants' phenology -- shifting when their buds open in the spring and when their leaves change colors and drop in the fall. New research I coauthored shows how nighttime lights are lengthening the growing season in cities, which can affect everything from allergies to local economies.
In our study, my colleagues and I analyzed trees and shrubs at about 3,000 sites in U.S. cities to see how they responded under different lighting conditions over a five-year period. Plants use the natural day-night cycle as a signal of seasonal change along with temperature. We found that artificial light alone advanced the date that leaf buds broke in the spring by an average of about nine days compared to sites without nighttime lights. The timing of the fall color change in leaves was more complex, but the leaf change was still delayed on average by nearly six days across the lower 48 states. In general, we found that the more intense the light was, the greater the difference. [...]
This kind of shift in plants' biological clocks has important implications for the economic, climate, health and ecological services that urban plants provide. On the positive side, longer growing seasons could allow urban farms to be active over longer periods of time. Plants could also provide shade to cool neighborhoods earlier in spring and later in fall as global temperatures rise. But changes to the growing season could also increase plants' vulnerability to spring frost damage. And it can create a mismatch with the timing of other organisms, such as pollinators, that some urban plants rely on. A longer active season for urban plants also suggests an earlier and longer pollen season, which can exacerbate asthma and other breathing problems. A study in Maryland found a 17% increase in hospitalizations for asthma in years when plants bloomed very early. The study has been published in the journal PNAS Nexus.
In our study, my colleagues and I analyzed trees and shrubs at about 3,000 sites in U.S. cities to see how they responded under different lighting conditions over a five-year period. Plants use the natural day-night cycle as a signal of seasonal change along with temperature. We found that artificial light alone advanced the date that leaf buds broke in the spring by an average of about nine days compared to sites without nighttime lights. The timing of the fall color change in leaves was more complex, but the leaf change was still delayed on average by nearly six days across the lower 48 states. In general, we found that the more intense the light was, the greater the difference. [...]
This kind of shift in plants' biological clocks has important implications for the economic, climate, health and ecological services that urban plants provide. On the positive side, longer growing seasons could allow urban farms to be active over longer periods of time. Plants could also provide shade to cool neighborhoods earlier in spring and later in fall as global temperatures rise. But changes to the growing season could also increase plants' vulnerability to spring frost damage. And it can create a mismatch with the timing of other organisms, such as pollinators, that some urban plants rely on. A longer active season for urban plants also suggests an earlier and longer pollen season, which can exacerbate asthma and other breathing problems. A study in Maryland found a 17% increase in hospitalizations for asthma in years when plants bloomed very early. The study has been published in the journal PNAS Nexus.
Lucky Sky (Score:5, Interesting)
At my house I'm up on a hill and have a huge view of the night sky so I love getting my astronomy binoculars, telescope and cameras out to take some pictures. However the streetlight below blocked some angles and I would have to be positioned behind some of the foliage of my garden to get a good view of the sky.
I had the good fortune of being home when the local council was replacing the lights with led lights in a new reflector unit which seem to be a lower color temperature and less bright. As the workers were replacing the reflector unit I asked them if they could point the streetlamp away from me a bit and they happily obliged and this has allowed me to see much more of the night sky.
I wonder if it means I'll have to do less gardening as well?
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I had the good fortune of being home when the local council was replacing the lights with led lights in a new reflector unit which seem to be a lower color temperature and less bright.
Output spectrum is the single most important factor when it comes to light pollution.
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No, its not. I live 100 meters from a truck farm. They replaced the sodium lamps in their site lighting with LED lights and the light polution is worse because they don't have them aimed correctly, in fact its worse now than when the old lights were in place. If they were installed to only illuminate their property it would be much better.
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No, its not. I live 100 meters from a truck farm. They replaced the sodium lamps in their site lighting with LED lights and the light polution is worse because they don't have them aimed correctly
Sodium lights are very energy efficient and have an ideal output spectrum. LPS is particularly nice narrow band yellow. Even HPS has basically no blue.
Cheap white LEDs have horrible output spectrums with a huge blue spike. More modern low temperature LEDs don't have this problem but they cost more and rarely find their way into street lamps.
The reason this matters so much is the same reason the sky is blue. This frequency of light is preferentially scattered by the atmosphere.
Sure light pollution is wors
Yeah (Score:1)
lets make our cites go dark. Riiggght
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There are several ways to do this:
- Adjust humans genetically to see in the dark
- Add external device that allows humans to see in the dark
- Move humans under ground and let plants live above ground.
- Focus lights where they are needed and eliminate reflections by adjusting angles or by using material that doesn't reflect light.
- Focus lights using AI only directly to where humans are looking at.
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Move humans under ground and let plants live above ground.
Many people on this forum are pioneering this effort.
Inevitability (Score:2)
the police told us light didn't help (Score:5, Funny)
Had a police officer come talk to us about neighborhood safety. Neighbor said the streets were dark (big trees blocking the street lights) and he said they didn't see a strong correlation between lighting and crime.
Fast forward many years later, neighbor has his catalytic converter stolen, with the car parked UNDER a streetlight.
Turn them all off...
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We've been through this. Only guns can protect you from crime.
There literally is no other choice. If your area still has crime, just get more guns.
Yup. Nothing like a bunch of people with guns [cnn.com] to stop crime.
Re:the police told us light didn't help (Score:5, Interesting)
The evidence that streetlights reduce crime is mixed.
One problem is that neighborhoods without streetlights tend to be poor neighborhoods that have higher crime rates with or without the lights.
Before-and-after comparisons are also problematic because new streetlights are usually accompanied by funding for other improvements as well, such as increased patrolling. Or the streetlights go into neighborhoods that are gentrifying, and that is what is causing the crime to drop, so the causation is reversed.
The bottom line is that streetlights either make no difference or a small enough difference that the cost would be better spent on other crime reduction methods.
The most cost-effective method of reducing crime is reducing childhood exposure to neurotoxins such as lead, mercury, and cadmium. But that doesn't fit on a bumper sticker.
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It might be more effective to fit streetlights with motion detectors. So they're off until someone walks near them. Would save quite a bit of electrickery too.
Given the age we live in I'm suprised they've not already been fitted with motion senstive CCTV cameras with facial recognition !
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Not traditionally done because until very recently, this was impossible to do.
High pressure sodium lamps take a while to light up once struck, usually anywhere from 15 minutes or more. So they're not really amenable to being able to be turned on and off because they don't produce light until some time later. They are used because they are extremely ef
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We have those on cycling and walking paths in Melbourne. They have a small solar panel and battery, as well as a connection to mains power. They run at low brightness until something triggers the motion sensor, causing them to switch to high brightness for a while. I'm not sure how useful it actually is. If you're cycling, you'll be in the next light's area almost as soon as one light notic
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Japan doesn't have street lighting in many areas. Often people have a small light or two on the outside of their house that they leave on, but a few hundred lux doesn't do much.
Yet crime is very, very low in Japan.
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Regardless if they prevent crime or not, they definitely protect against traffic accidents. The impact on plants this study proposes seems rather minor in the scheme of things- and even thing it's not clear to me that the temperature difference + reduced sunlight from being in a city is not part of the cause.
As far as light pollution- that's caused by improper design of street lights and lights on homes. If the lights are entirely pointed downward, towards the ground, as they're supposed to be, they don't c
Re: the police told us light didn't help (Score:2)
As a driver, I think streetlights probably protect pedestrians more than cars.
When coming home in the dark, I find the illumination of people on the sidewalk (especially corners) useful. Headlights aren't really designed for wide and far illumination unless using high beams.
I wish they used much warmer LED colors and lower output though.
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It seems you've never driven through a medium sized city at night if you think sidewalk and crosswalk are so far apart.
Drunk people do stupid things and I'd rather not hit a pedestrian even if it's their fault.
I'm not talking through ways, I'm talking about coming home to a walkable mixed use grid neighborhood after 9pm.
The high beams are aimed down and to the right, they do not do well at letting me see the left sidewalk on a one way street.
I have complaints about the over lighting in my city and complain
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Yes and no. Especially in non-urban areas, there's a tendency to light up intersections brightly and in between not so much. That makes it harder to see something beyond the brightly lit intersection, like a jay-walking pedestrian.
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Headlights protect against traffic accidents. Streetlights glare blind drivers.
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I also blame solar (Score:2)
Every garden-owner and his dog has solar-lights installed in the garden that are alight until 5 in the morning.
The bats are thinking it was again the century of the fruit-bat.
News? (Score:2)
I don't think this is news. This has been known since Sept. 4, 1882.
Not news, but change is hard... (Score:5, Insightful)
This has been known for a long time. Yet fixing the problem seems to be really hard. We need two laws or regulations:
First and most important: a light should only illuminate its target. The LED or bulb must not directly illuminate anything else. Spend some money designing proper fixtures and reflectors.
Second, light levels should be the minimum required to do the job. There is no reason to light up streets like runways. It would generally be nice to eliminate a lot of illumination altogether. Most street lights are simply not needed. How many pedestrians are out at night, really? If they are, then they can carry flashlights.
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Spectrum matters too. Human eyes are most sensitive to yellow-green. The plant phytochrome system (night detection) is most sensitive to red / far red. There's also general photosynthesis as a hormonal trigger (most activity per unit energy in the red spectrum, but some across the whole visible spectrum), as well as cryptochromes and phytochromes, which cause hormonal triggers in response to blue light. So for human lighting with the least impact to plants, you ideally want lighting in the yellow-green ran
New street lights fix this (Score:1)
3 or 4 years ago here in rural North Carolina, they switched all the old mercury vapor lights to these super-bright, super-intense, super high color temperature LED lights for "energy savings" and "increased safety" around the town and outskirts. The results were immediate, and deadly.
The first thing that happened was that nighttime driving accidents increased by about 6 times, because these super-intense point sources of light that were not well shrouded, were blinding drivers and causing them not to be ab
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Imagine a city without lights at night today, like after a natural disaster or during a war -- the overwhelming fear, the lawlessness.
Exactly the sales pitch we used to present to neighborhood associations when I worked the the power company and we wanted to sell street lighting. Even though it's not true.
You are better off installing motion detector light which keep themselves turned off unless there is actually something moving around in the dark.
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Timing signal (Score:2)
More importantly... (Score:2)
...it has disrupted my ability to see tiny dots, or to resolve dots into tiny spheres for my own enjoyment.
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Was it the light or the heat (Score:1)