Mike Hawtin – Head of Polyhalite Projects
Dark Skies – revered by our ancestors, a gateway to science, crucial to nocturnal wildlife and a special quality enjoyed by residents and visitors to the North York Moors National Park – are under threat.
Over 80% of people in the UK are unable to see the Milky Way, our own galactic neighbourhood. In most cities you’d be lucky to see a handful of stars due to light pollution but in truly dark places, like the North York Moors National Park, you can still see thousands. With the availability of cheap high power LED lighting though, those pristine dark skies are increasingly at risk.
It’s not all bad news though. Unlike other man made threats to the natural world, this one isn’t so complex that we’re almost paralysed into inaction, we just need to talk about ALAN.
So who on earth is ALAN!? Well, ALAN stands for Artificial Light At Night and when used incorrectly and inconsiderately, ALAN can have a devastating impact, not just on our ability to enjoy Dark Skies but on animal and plant life, and even human health.
Imagine a situation where developments that interrupt or obscure our natural daytime landscapes or that impact on natural habitats and disrupt animal behaviour, were allowed to go ahead unchecked? Well that’s exactly what happens when we go to the middle of those well-known budget supermarkets to buy those cheap super bright white LED lights and put them up around our property. These lights are designed to flood the outside of our homes and garden with simulated daylight, often causing significant glare and nuisance to others, both near and far.
Understandably we can be quite protective of our need for light at night. Let’s face it, we all need it, whether it’s for safe working, recreation, getting to our front door with shopping bags and children in tow or for general feelings of security. At the same time though, we can probably all think of poor examples of lighting, from inconsiderate neighbours keeping us awake into the night, car sales forecourts dangerously dazzling us when driving past, long after closing time or that one floodlight we can see for miles in an otherwise dark and tranquil remote landscape.
The rhythms of life
The impacts of light pollution go much further than ‘just’ causing a nuisance. It prevents us from seeing something humans have been able to see for thousands of years, something that has inspired humans to seek to understand our place in the universe, to help explain the fundamentals of science we now take for granted and even helped us navigate, long before we had maps or smartphones.
Throughout evolution, circadian rhythms, present in most living things have been responsible for natural sleep wake cycles. As daylight fades, replaced by warmer light then darkness, it signals physiological changes which signal a slowdown, which prepares us for sleep.
ALAN disrupts these natural rhythms, altering animal and plant behaviour. It can cause bats to think it’s still daylight so they stay in the roost instead of feeding and mating. It attracts moths which increases their predation and prevents them undertaking their role as nocturnal pollinators.
It even disrupts the migratory behaviour of birds and the dormancy cycles of trees and plants can be altered, impacting on their ability to survive the rigors of winter. As if that’s not enough, study after study shows that too much light (especially blue light) at night also disrupts human circadian rhythms, which has been attributed to weight gain, stress, depression, diabetes and even heart disease and some types of cancer.
We know that many living things are already struggling to adapt to accelerated climate change over the past century. Widespread use of LED lighting technology though is little more than 10 years old and, through an increasing number of studies, we are just beginning to understand the impacts, which, left unchecked, could be devastating for wildlife and human health.
Conservation at the flick of a switch
It’s not often in the world of conservation, at a time when we’re tackling complex ecosystem problems, that we can legitimately say that a problem is solvable at the flick of a switch. Imagine if we could crack plastic pollution, noise pollution or vehicle pollution often with little or no cost or, if in fact that in solving the problem, we would actually save money! Wouldn’t that be something?
In the case of light pollution though, for the most part, it really can be that easy. Tilting lights down to only light where we need and switching them on only when required, and sensitively using low power LED lighting at a level suitable for the situation, will save energy and money. It will also prevent nuisance light pollution from wasted upward light and glare.
The answer isn’t simply urging us all to switch off lights though, with a bit of thought and effort, we can have the best of both worlds. By only lighting what we need, when we need it and at a level suitable for the situation, we can protect our dark skies, our nocturnal animals and even our human health whilst still having enough light to work, play and feel safe at night.
It’s all about control
Think about how you feel when you’re driving towards an inconsiderate or forgetful driver who keeps their lights on full beam, dazzling you and causing danger to other road users. It’s easy to fit a floodlight and angle it up at 45 degrees thinking it’s doing the job intended when in fact half of the light is being projected above horizontal into the sky. So with the exception of those trying to signal the caped crusader or visitors from outer space, that’s up to 50% of light completely wasted. Additionally if we look at those lights, we’re dazzled, preventing us from seeing properly, especially into the deep shadows created, which contributes to reduced safety rather than improving it.
It’s also understandable to think that leaving lights on all night will offer more security but it has two significantly negative impacts:
- It advertises our location for miles around so those unwelcome visitors looking for opportunities will know where to look.
- If lights are on all night, we have no idea whether somebody is meant to be there or not.
Using sensors for instance will immediately alert us if there’s an unexpected presence. If we’re concerned about animals setting them off then selecting a light with a separate sensor can help solve this by allowing the light and the sensor to be angled independently of each other.
Warm light good – Cool light bad
The colour temperature or warmth of the light is also very important. Warmer light has less impact on nature and human health. It mimics evening light (remember those circadian rhythms) as the end of the day is approaching and is much less likely to cause disruption to the natural world. Warm light also triggers feelings of relaxation, safety and welcome, most likely developed over thousands of years of sitting around the warm light of camp fires with friends and family, and feeling safe from predators.
Think about driving past that shop, hotel or pub at night and consider what looks and feels more welcoming, warm cosy light or harsh blue white light? Another impact of blue white light is that it scatters much more readily into the atmosphere which means it can cause much greater sky glow if installed incorrectly.
The colour temperature of light is measured in kelvin (k). 3000k is considered a key threshold. Below this is considered warm and over is considered cool. Dark Skies friendly lighting should have a recommended colour temperature of 2700k but where technology or availability doesn’t allow then 3000k should be considered an absolute maximum. The good news is that most lights and bulbs are available in warm white and have this specification stated on the box. It will also usually show the amount of light given off in lumens. 500 lumens is usually ample for most residential applications.
DID YOU KNOW? North Yorkshire County Council have agreed to install fully shielded streetlights with a maximum colour temperature of 3000k in our protected landscape.