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Sustain v07 i03
Spring 2006

As a new law is introduced in the UK to curb light pollution, Anna-Marie de Souza looks at the harmful effects that artificial lighting can have on the environment...

If it wasn't for my next-door neighbour's security light, which goes on every time I walk up my front path, I would never be able to find the keys at the bottom of my Mary Poppins-like bag. The same light also comes in handy to let me know who is visiting, walking past or, in fact, when any number of the neighbourhood's cats prowl by. To date, I am unaware of any 'predators' that this light has managed to scare off - in fact, in the main, this light is no more than a nuisance. And I am not alone in thinking that.

On 6 April this year [2006], the first UK law to tackle light pollution came into force. Exterior lighting has now joined noise and smells on the list of things that can be treated as Statutory Nuisance under the Environmental Protection Act 1990. And not before time.

The Environment Agency defines lights pollution as 'a brightening of the night sky caused by artificial light being scattered by small particles in the air, such as water droplets and dust.' Light pollution also includes light intruding into our homes, such as bright streetlight or - as in my case - a security light. However, minor nuisance issues with troublesome neighbours is nothing in comparison to to the effects light pollution is having on wildlife, astronomical research and climate change.


'Light pollution is a 'Cinderella' pollutant and it is only just now beginning to be recognised as the serious issue it is.' says Martin Morgan Taylor, from DeMontfort Law School.

According to research by the British Astronomical Association and the Campaign to Protect Rural England, some 85 per cent of the UK's population reside in areas where artifical lighting blots out the night sky. Over a quarter of England's landmass now produces more light than in 1990, preventing most UK residents from seeing the night sky.

Even professional astronomers find that telescopes built to observe the farthest reaches of the galaxy a few decades ago are no longer effective. As NASA's David Herring explains : 'Light pollution impairs our ability at the surface to see the stars, planets and other celestial bodies.'


Whilst it may be a shame not to be able to do a spot of stargazing from our bedroom windows, does light pollution really have any serious consequences ? Well, the simple answer is 'yes'. Amateur astronomers routinely discover comets, asteroids (sometimes potentially hazardous asteroids), and monitor the behaviour of thousands of stars. However, light pollution is seriously undermining the ability of British-based astronomers to take the lead in this field. As Bob Mizon, from the British Astronomical Association's Campaign for Dark Skies says : 'One of the reasons that professional UK astronomy has been driven abroad to mountain tops in Chile, the Canaries and Hawaii is the seriously degraded state of the UK night sky.'


Although light pollution's impact on stargazing is as clear as day, its effects on nature and the overall environment is just coming into focus. John Burton from the World Land Trust describes the potential devastation caused by light pollution : 'Millions of birds are disorientated by street lights and billions of insects die beneath them.'

Many creatures are affected by light intruding into their nocturnal world - the light confuses their natural patterns and deters them from establishing foraging and nesting areas, which affects their breeding cycles causing, in some cases, premature breeding and subsequent high mortality rates. For example, some birds become so disorientated by artificial lighting that they build nests in autumn, rather than spring.

In a light-polluted site, birds continuously chirp throughout the night, in anticipation of a dawn - this can affect all manner of things, including reproduction and migration.

Birds use the moon and stars to navigate their bi-annual migration: scientists speculate that when birds fly into lit areas, the bright lights disrupt their steering sense. Numerous reports document birds flying off-course toward bright lights, buildings and towers.

Birds are attracted to the lights and, when they reach the source, they can become confused, get blinded by the glare or burnt. Birds often crash into illuminated areas, or circle them until they drop from exhaustion.

Albert M Maville, from the US Division of Migratory Bird Management, explains : "Lights on towers (especially the tall, guyed towers) attract night-migrating songbirds, especially during inclement weather conditions, killing what we conservatively estimate to be 4 to 5 million birds per year."


Lights also attract a host of insects, which can cause problems around the home, and the insects themselves risk death by electrocution. This is of particular concern in relation to the decline of numbers of some moth species, something that has correlated with the rise of excess outdoor lighting.

Whilst everyone knows that moths are attracted to light, most are unaware of the quantity of eenrgy that moths expend in this pursuit and that it can cut the female's chances of attracting a male. It aso interferes with locating places to lay eggs, giving the larvae inadequate conditions to develop.

Trees, which provide entire ecosystems to many animal and insect species, can also be detrimentally affected by light pollution. Trees need to adjust to seasonal variations, and artificial light prevents them from doing so, resulting in trees dropping and sprouting their leaves in the wrong season.

This [effects] the wildlife that depends on trees as their natural habitat. For example, many birds are unable to nest in trees due to unstable surroundings.


It is said that lighting contributes to one-fourth of all energy consumed worldwide. Each year, thousand[s] of kWs of electricity are wasted on outside lighting, be this shop fronts, billboards, floodlighting in empty car parks - or security lights.

Studies have shown that 50 to 90 per cent of building light is unnecessary, and at a far higher voltage than is actually needed. The average household security light uses a 500W bulb, which leads DeMontfort's Martin Morgan Taylor to wonder: "The UK's most powerful Lighthouse uses a 1000W light, so why does an average household light need to be as powerful as half of this ?"

Morgan Taylor paints a stark picture of how serious a problem excess lighting is with a shocking sum (see below) that likens the consumption of energy used on household security lights as similar to that of emissions from a diesel car that has travelled 600Mkm.

It goes without saying, then, that if simple steps were taken - for instance switching off unnecessary lights or using energy-efficient bulbs - the UK could save tonnes of CO2 emissions each year.


Whilst studies show there is little evidence that outdoor lights actually act as an effective deterrent to burglars. John Burton does concede that "there are places where night-time lighting reduces accidents, but there are plenty of places where there is no obvious benefit of lighting being on at 2am." Furthermore, a common view is that outdoor lighting may actually aid potential predators by making entry points clearer and highlighting home-security risks.

So, it's probably about time I went and warned the next-door neighbour that his security light is now legally a nuisance and a danger to the environment as we know it. I also think it's about time we let the neighbourhood cats roam in peace and, above all, in the dark.


It is know that there are 22M dwellings in the UK, so if one in ten had a 500W floodlight, then thre would be 2.2M lights. Generating 1kW/hr of electricity produces 0.9kg of CO2 emissions, if generated from fossil fuels.

Most lights are on an infrared switch, activated needlessly when, for example, cats or pedestrians walk by. If an average light is on for quarter-of-an-hour a night, then the average national statistic is (2.2M x 500W) x 0/25hr / night = 275,000 kW/hr/night.

Per year this must be multiplied by 365 = 100MkW/hr/year.

If 1kW/hr produces 0.9kg CO2, then some 90Mkg/yr of CO2 is produced as a by-product from producing the electricity needed to power domestic floodlights within the UK.

If a new diesel car produces 150g of CO2 per kilometre travelled, then one car woudl have to travel 600Mkm to produce the same amount of CO2 as that produced by home floodlights in the UK.

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