The rhythm of night and day is integral to all plants and animals, governing the behaviours that sustain life. However, light pollution is disrupting the way both diurnal and nocturnal species behave – and the problem is only getting worse.
Solareye supplies eco-friendly solar lighting to private landowners and local authorities all over the world. We know public safety and recreation time shouldn’t come at the cost of wildlife. That’s why we created the Solareye80 bat hat, a solar ground light which reduces upwards light spillage by 98%, and a warm white (2,700k) LED option (as recommended by the International Dark Sky Association), which minimises blue light levels, something that has been found to impact the feeding patterns of bats.
In this blog, we explain everything you need to know about ecological light pollution.
What is light pollution?
Light pollution is a broad term encompassing all the negative impacts of outdoor lighting. It is caused by artificial lighting at night (ALAN) that is unwanted, excessive, and inappropriate to the point that it disrupts ecological rhythms and our ability to discern celestial objects. Light pollution is a local and global phenomenon, with some effects like light trespass operating in close proximity, and some taking place on a much larger global scale. As forms of pollution go, it’s purportedly increasing faster than any other – growing by 49% in the past 25 years (source). Light pollution acts in various different ways, including:
- – Glare – an uneven contrast between bright and dark areas.
- – Light trespass – where unwanted light invades another’s space.
- – Light clutter – excessive illumination through the grouping of lights.
- – Sky glow – light reflecting off moisture and particulate matter in the air, causing a glow.
Types of light pollution
Many people choose to split light pollution into two distinct types, though really, they are just different manifestations of the same problem. The reason for doing so is that more attention is generally paid to the former because we tend to take an anthropocentric view. Creating a separate category for ecological light pollution raises awareness for the environmental impacts of ALAN, which affect us indirectly.
- – Astronomical – when we think of light pollution, most people think of washed-out skies with the quality of night degraded. As a result of increased glare, sky glow, and other effects, humans are finding it harder and harder to discern and study celestial objects.
- – Ecological – light pollution poses a significant threat to diurnal and nocturnal species alike because it alters the cycles of natural light. Since many activities are governed by these cycles, ALAN causes behavioural changes that reverberate throughout ecosystems, causing population-threatening imbalances.
Sources of light pollution
Any ALAN can contribute to light pollution if not properly mitigated, but artificial lighting at night offers numerous benefits to us – improving safety and increasing recreation and leisure time. The good news is that dark-sky friendly lighting is possible, but many people aren’t doing enough to limit the impact of their lighting schemes. From illuminated buildings and security lights to streetlights and other forms of public lighting to fishing boats and vehicle lights, many different light sources contribute to the problem.
What are the effects of light pollution?
Disorientation & misorientation
Many different species react to light, whether that’s positively or negatively. Small nocturnal mammals may be repulsed by light, whilst certain insects and migratory birds that use starlight to navigate may experience an attractive response – causing them to become misoriented. Amphibians in particular have extremely reactive photoreceptors and experience temporary blindness in the presence of ALAN which doesn’t return to normal for several hours.
ALAN also disrupts feeding, because many species use light cues to prompt the start and end of foraging behaviour. Animals like bats, for example, have been known to emerge later than normal as a result of light pollution, reducing the time they have available to hunt. Nocturnal insects are often attracted to artificial light, and they can face increased predation from fast-moving bats as a result. On the other hand, slow-moving bats tend to be more vulnerable to night time raptors, so they are unable to take advantage of this. Instead, they find themselves victim to the ‘vacuum effect’ because all their prey has been drawn away.
Light pollution can also have an impact on the reproductive patterns of many species. Amphibians like frogs and toads, for example, croak during the night as part of their breeding ritual – something that is discouraged by ALAN. A range of other species find their rates of reproductive success negatively impacted by artificial light, including bats and birds. Even the night time pollination of plants can be affected!
In an ecosystem, every species is connected. That means if ALAN impacts one species, the consequences will be felt throughout the habitat, disrupting intra and inter species competition and predation, and altering ecological niches. Some species have been known to take advantage of foraging under ALAN in what is known as a ‘night light niche’. However, this behaviour is not sustainable and will imbalance the ecosystem in time as prey populations dwindle.
Dark corridors are fundamentally important to light averse bats who avoid well-lit areas and commuting routes. If any of these corridors are affected by the increased presence of light pollution, they may find their habitat fragmented. This will make it harder for the bats to travel between feeding grounds and roosts, or increase travel time which will go on to impact reproductive success.
Ecological outdoor lighting from Solareye
Lighting an outdoor space for the public to enjoy doesn’t have to disrupt local habitats. By choosing products and planning your lighting scheme carefully and consciously, you can reap the benefits of increased illumination without the environmental toll. To find out more about how our products can enhance your outdoor space, feel free to give us a call.