Shining a light on why Dark
Skies matter
The Dark Skies movement began in 1988 with the formation of the not-for-profit organisation now called DarkSky International. Originally associated mainly with astronomers, it’s increasingly shaping how we light our gardens and other outside spaces at night.
No-one ever claimed astronomy is easy. Launching telescopes millions of miles out into space is the very definition of rocket science. But throughout the past century or so astronomy has become even trickier as we increasingly light up our nighttime cities, towns and roads. Those streetlights may be a handy help in guiding us on our way, but to astronomers they’re light pollution, blotting out the view of the stars at night and making it difficult for anyone inclined spend a moment marvelling at the Milky Way in all its majesty.
Coming back down to earth, the main relevance of Dark Skies for anyone with an outside space – be it an urban courtyard garden or several rolling acres in the countryside – lies in how we choose to light our outdoor spaces at night. Because it’s not just astronomers who rage at light pollution. Local council planning departments, too, are taking a serious interest in the issue, driven by the fact that nocturnal animals can be seriously harmed by light pollution. These creatures have evolved to thrive in an environment with a predictable number of hours of uninterrupted nighttime. Once we start messing about with outside lighting, they don’t know whether they’re coming or going.
The creatures we’re talking about are birds, bats, moths, other insects, rodents…you name it. Light pollution even affects human beings, interfering with our circadian rhythms, as anyone with a streetlight right outside their bedroom window will enthusiastically attest.
Creatures affected by light pollution include:
Not being nocturnal ourselves, it’s easy to overlook how much impact light pollution can have on those creatures who are. For a whole menagerie of birds, bats and insects, light pollution can interfere with their feeding habits, confuse their mating behaviour and play havoc with their migrations. It’s equally easy to underestimate the number of creatures affected: did you know 30 per cent of vertebrates and 60 per cent of invertebrates are nocturnal? There’s a whole lot of life going on out there in the darkness that we ought to be more mindful of.
Owls, like the UK’s Tawny and Barn Owl, don’t need artificial light to see their prey, but artificial light means their prey can see them. Coastal seabirds like shearwaters, which wait until after dark to return to their nests, and petrels, which do most of their hunting after dark, can get distracted by bright coastal lighting, causing them to crash or land in hazardous areas. Many nocturnally migrating songbirds and thrushes use the stars to navigate, so light pollution can leave them seriously disoriented. Too many also collide with illuminated glass tower blocks, with predictable results. Even daytime birds like robins can be stressed out by streetlights, fooled into singing and feeding late into the night to the point of exhaustion.
Bats are light pollution victims, too. A few of the more flexible species, like Pipistrelles, will hunt insects attracted to streetlights, but most of the UK’s rarer bats, such as lesser and greater horseshoes and all the Myotis species, avoid illuminated areas like the plague, which can make it difficult to get to their favourite hunting grounds. But all bats can be disrupted by light pollution, either by delaying when they leave their roosts, blocking flight paths with bright light barriers, or fragmenting their habitats. In the most extreme cases it can lead to bats refusing to leave their roost to feed and ultimately starving because they assume it’s still daylight outside.
Moths are another casualty of light pollution. There are about 2,500 moth species in the UK and pretty well all are affected by light pollution to some extent. It disrupts their navigation, making it more challenging to feed, and bewildered moths dithering about near bright lights are easy prey for bats. Some moth caterpillars are also attracted to artificial light, luring them away from their food sources – a recipe for lots of hungry caterpillars. Research by Butterfly Conservation and partners shows that caterpillar numbers drop by up to 52 per cent near modern LED streetlights, leaving slim pickings for the birds that feed on them.
| Creature Type | Percentage that are Nocturnal |
|---|---|
| Vertebrates | 30% |
| Invertebrates | 60% |
Bare in mind these tips to help align your lighting with the Dark Skies movement.
1. Less is more.
For safety and practical reasons, some outdoor lighting feels essential, particularly for paths, steps, front doors and seating areas. But for more ecorative lighting of trees, shrubs and architectural features, pause a moment to remember our nocturnal neighbours and then reflect on whether it’s really desirable. For example, is it worth lighting your driveway when the only people using it after dark are in vehicles equipped with headlights?
2. Dark Skies thinking requires all your light fittings should project their light down to the ground, not up to the sky.
The fittings will therefore be shielded on the top and sides. That way, creatures on the wing can’t see the light source, which is by far the brightest part of the light fitting. If in doubt, look for the DarkSky Approved seal when selecting your light fittings.
3. Only use your outside lighting when you need to.
Motion detectors and timers are ideal for limiting usage, while also helping to keep your electricity bill down.
4. Not all things bright are beautiful.
For each light fitting, use the minimum wattage necessary to do the job. The most enjoyable garden lighting schemes tend to be those that create a subtle interplay between soft light and shadow.
5. Choose your light colour with care.
LEDs give you the choice of different light colour temperatures. The rule of thumb is: the warmer the light temperature, the happier your wildlife will be. The standard 2700K warm white is acceptable, but even better is the 2200K extra warm white offered by our Hudson, Hunza and LuxR fittings, and the 1800K ultra warm white option for our Hudson fittings. Any light colour above 2700K (e.g. 3000K) is not Dark Skies compliant.
Uplighting a large tree such as an oak can certainly look dramatic. But is it environmentally responsible? For example, our English oak has some 2300 wildlife species relying on it for food, shelter or breeding, with over 300 of them depending on oaks for their survival. Hundreds of insect species, including gall wasps, caterpillars and beetles, feed on the leaves, acorns and wood. Birds like jays and pied flycatchers scoff the insects and acorns. Bats, squirrels and birds nest in the hollows of older trunks. Lichens and mosses colonise their bark.
Uplighting your mature oak won’t disturb all these species, but it will make life harder for many. However, if you still need to press ahead, use a spot light beam that’s as narrow as possible so you’re only lighting the tree, not the night sky around it. Choose a warm white light colour of 2700K or less. And fit your spot light with a glare guard or snoot to minimise glare and light spill from the light source.