Last updated August 1, 2018 at 10:18 am
Brighter artificial lighting is affecting biological functions such as sleep, immune function, growth, reproduction and survival in the animal – and human – worlds.
In simple environmental terms, LED lights appear a clear winner. They are significantly more efficient than traditional incandescent bulbs and last considerably longer.
But they are also a lot brighter, individually and collectively, and that is increasing the levels of light pollution across large swathes of the planet.
Studies from various parts of the world are showing that this, in turn, is increasing the already negative impact that artificial lighting is having on a range of animals, including birds, mammals, reptiles and insects.
In 2015, for example, zoologists from Melbourne’s La Trobe University revealed that Tammar wallabies living in the presence of artificial light at night delayed when they gave birth, resulting in their offspring being born out of sync with when their natural food sources were available.
Earlier this year, ecologists from the University of Delaware studied seven years of data tracking Northern Hemisphere birds on their autumn migration south and found that the presence of artificial light at night was luring them into urban areas rather than the forested areas where they would normally land.
LED can affect melatonin
Recent evidence suggests that LED light might be exacerbating the problem.
“The transition of street lighting from incandescent to LED continues to increase the amount of light pollution,” said UD’s Assoc Prof Jeff Buler.
“If you think about it from an evolutionary sense, for all wildlife really, mammals and insects and birds, they’ve only been exposed to this light pollution for less than 200 years. They’re still adapting to the light.”
In the case of Buler’s birds, the problem is essentially the brightness of the light and the sheer quantity of it. In the north-eastern United States, there is no refuge from the light – birds can always see and potentially be disoriented by the sky glow of a city.
For Dr Kylie Robert, who led the La Trobe study, the problem runs a little deeper.
LED lights typically emit more blue light, which can directly affect melatonin. This chemical plays a key role in the natural sleep-wake cycle of wildlife and humans, but its production is supressed in the presence of light.
It’s an issue that another Australian researcher, Dr Therésa Jones from the School of BioSciences at the University of Melbourne, is only too aware of.
“There is good evidence that blue light in particular affects some key physiological processes as well as the timing in our biological rhythms,” she said.
Blurring night and day
“It’s affecting some important chemicals, particularly melatonin. We produce melatonin naturally, as do all animals. It is sensitive to light so production during the day is extremely low or non-existent and it should increase at night. However, its production is sensitive to artificial light so in the presence of artificial light at night this does not happen.”
It is easy to see how bright lights might confuse birds or new-born turtles heading for the ocean, with often dramatic consequences.
A comprehensive international study, with input from researchers from Victoria’s Phillip Island Nature Parks, has estimated that at least 200,000 seabirds would have died around the world in recent years had specific rescue programs not been established.
However, Jones says the problem is more complex, as suggested by Robert’s research with wallabies.
“We know that artificial light is having affects physiologically as well because it messes up timing,” she said.
“A lot of the biological systems in a lot of the species use changes in light and dark as indicators: not just of day and night but also for the seasons for example. As we head towards winter we get shorter days and longer nights and that for seasonally reproducing species such as the Tammar wallaby this is linked to the hormones that stimulate reproduction.
“But light at night is masking both the change between night and day and potentially the seasons. We are now seeing things changing.
“Some species of European song birds commence singing at the wrong time and sing for longer into the night. Diurnal animals, which usually sleep during the night might extend their activities into the night.
“Nocturnal animals might be forced to compete with more species or more critically be at more risk from predation as their night-time niche is invaded.”
Jones and colleagues are midway through an Australian Research Council funded project designed to better understand these impacts.
“We are introducing lights at night and seeing what happens to the physiology of different animals, including crickets, spiders, flies and swans ; does it affect biological functions such as sleep, immune function, growth, reproduction and survival?
Return to darkness
“In all cases to date we find that the answer is yes. It’s creating change that is having real biological effects. Orb-weaving spiders are an interesting case, because they benefit from their fact their prey are attracted to the lights, much like birds, and so they potentially get more food.
“However, our research shows that they suffer physiologically and ultimately produce fewer offspring. We don’t really know why, but one possibility is that melatonin also interacts with chemicals that are related to hunger.”
While scientists try to get to grips with the extent of the problem, the obvious question is how to address it in a world getting increasingly lighter. Current activity is focused on two main areas.
The first is looking at the nature of light (are some colours less problematic than others) and how we can change the structures that lights are held in to try to minimise the scatter and the amount of light that goes straight up.
The second is to look at scenarios where it is practical and realistic to expect people to turn the lights off if it will have a clear and positive impact.
A number of community projects in the US and Europe have trialled options such as turning off street lights during the nesting season of turtles to try and reduce the number of hatchlings becoming disoriented by the inland lights.
More broadly, says Jones, the “ecological community is working hard to protect the spaces that are dark and mitigate the impacts of spaces that are currently light”.
“We’re fortunate in Australia as we have quite a lot of those, but even in other parts of the world there are areas where we do not see artificial light all the time and we need to take steps to preserve that.”