Most people are aware of water pollution, marine pollution or air pollution, but not many know about light pollution, which scientists say has wide-ranging impacts on human health, the environment and nature. 

With increasing technological advancements and urbanisation, our environment is also continuing to get ever more illuminated, with the world’s artificially lit areas expanding at an estimated 2.2 per cent a year. Global light pollution is skyrocketing and experts want immediate measures taken to limit artificial light at night in main cities and inside houses. 

World Economic Forum (WEF) senior writer Emma Charlton reveals five major negative impacts of light pollution damaging the environment and recommends what to do about it. WEFs report, ‘Nature Positive: Leaders’ Insights for the Transition in Cities’, discusses how to develop our cities in harmony with the environment. 

The first negative impact of light pollution, Charlton notes, is that it devastates wildlife. Plants and animals depend on Earth’s daily light and dark cycle to govern life-sustaining behaviours. Research shows that artificial light at night has adverse effects and even deadly effects on many species. 

Second, she argues, light pollution can make you less safe. There is no clear evidence that increased outdoor lighting deters crime. Poor outdoor lighting can decrease personal safety by making victims and property more visible to criminals. 

Third, light pollution wastes energy and money. As much as 50 per cent of outdoor lighting is wasted, which increases greenhouse gas emissions, contributes to climate change, and renders us all more energy-dependent. 

This waste can be solved with advanced lighting controls like dimming and remote sensors and transitioning to energy-efficient LEDs, which could save US$15.4 billion per year in the US alone. 

No nights 

Fourth, Charlton suggests that light pollution may harm your health. Studies suggest that artificial light at night negatively affects human health by increasing our risks for obesity, sleep disorders, depression, diabetes, breast cancer and more. 

Fifth, Light pollution apparently robs us of our heritage. Our ancestors experienced a night sky that inspired science, religion, philosophy, art, and literature. Now millions of children across the globe will never know the wonder of the Milky Way, she says. 

However, light pollution is reversible and there are four key steps recommended that the world can take to minimise its impacts. 

The first one is to reduce the use of light, installing it only when it’s really needed and at the lowest brightness possible. Second is to use controls like dimmers, timers and motion sensors to make the lights as efficient as possible.  

The third recommendation is to use shields to direct light toward the ground, reduce glare, and the fourth is use warm-coloured lights where possible and limit use of blue wavelength lights, which are thought to be the most disruptive. 

In her article, ‘From fireflies to fish, light pollution is damaging the environment, what can we do about it?’ Charlton delves into the history before the invention of the electric light. 

Then, humans largely lived, slept, and worked in a way governed by the light of day. This natural rhythm of day and night, she explains, is encoded into all living things, from people to plants.  

Things changed with Thomas Edison’s 1880 patent for the incandescent lamp paving the way and since, electric lighting has been standard in most houses in the developed world since the md-twentieth century. 

“Since then, we have been lighting our homes, offices and streets to the point where a 2016 paper concluded that night-time light pollution covers nearly 80 per cent of the planet. With increasing technological advancements and urbanization, it’s continuing to get even lighter,” Charlton explains. 

The dramatic shift away from natural light cycles is affecting wildlife, biodiversity, human health and global energy efficiency. While a broadly accepted definition of light pollution is, the light generated by human activity that makes it difficult to see things in the sky at night, a growing body of evidence suggests the impact goes beyond merely blocking the potential for stargazing. 

How dark the night sky is affects wildlife, including bats, migratory birds, and insects. Light pollution threatens the health and natural cycles of humans, wastes energy and money, and disrupts ecosystems. 

Light pollution has increased by at least 49 per cent over 25 years, according to scientists. But why is light pollution a problem? The consequences of light pollution are wide-ranging and can pose serious risks to many aspects of life. 

Light pollution interrupts wildlife patterns and harms biodiversity. Studies show that birds, bats, and insects are among those in the natural world affected by light pollution. Migratory birds rely on natural light to guide them and interruptions can lead to collisions and incorrect navigation on their long-distance journeys.  

Sea turtles confuse artificial light for moonlight and are drawn away from the ocean, with millions of hatchlings dying in this way each year. 

Artificial light disrupts nocturnal moths and may have reduced the number of caterpillars by half, according to another study. And the mating flashes of fireflies meanwhile can be disrupted by even momentary flashes from vehicle headlights. This has knock-on implications for those who feed on them.  

Excess light can also tamper with the habits and reproductive cycles of bats. The patterns and habits of other animals at night – including owls, badgers, mice and frogs – are also impacted. For example, animals that use the cover of night to hunt, or to hide, are being affected, disrupting food webs.  

Precarious prey 

Bats have been shown to steer clear of lit-up areas because it exposes them to predators such as owls. The effects aren’t limited to land animals – fish also adapt their behaviours in response to light, for example shifting to deeper waters. 

Light pollution is associated with risks to human health. Humans are not exempt from the effect artificial light has on animals. Studies show it disrupts the body’s biological clock, hampering sleeping cycles. Worse, artificial light was found in a study to be significantly correlated to all forms of cancer including lung, breast, colorectal and prostate cancers individually. 

“Immediate measures should be taken to limit artificial light at night in the main cities around the world and also inside houses,” the authors of another study wrote, saying 99 per cent of outdoor lighting is wasted, only 1 percent serves a useful purpose.  

Light at night wastes energy and money, contributing to climate change. Light pollution accounts for 1 per cent of global emissions or the equivalent of 38 million vehicle miles or 80 roundtrips from the Earth to the Moon.   

Conserving energy is one of the easiest ways to combat climate change. Leaving artificial lights on – for example, in offices or stores after hours – is called “over illumination”, and curbing it is one of the easiest ways to cut back on light pollution and save energy. 

A European Commission study showed that city lights decrease the night-time cleansing of the atmosphere, and reduce the way nitrogen oxides are removed. The good news is that light pollution is reversible – and this sets it apart from other forms of pollution. 

“Unlike many other environmental issues facing the world, solving light pollution is straightforward, saves money, and delivers immediate results,” says International Dark-Sky Association Executive Director Ruskin Hartley.