The Threat to wildlife

Many birds and animals are affected by stray light intruding into their night world (e.g. abstracts from the Ecological Consequences of Artificial Night Lighting conference), confusing their natural patterns, deterring them from established foraging areas, and affecting their breeding cycles (causing premature breeding).
This is not just limited to urban areas; the detrimental effect of light pollution penertrates deep into the heart of our rural landscape.

The effect on Mammals

Lights attract and disorientate animals, for example British Bats (see Bats and lighting in the UK [pdf] for guidance), and endangered Beach Mice in the US. Even the milk production in dairy animals can be detrimentally effected by lighting. For many more examples, take a look at the LiteLynx-mammals page.

The effect on Birds

In a light polluted site, birds are continuous chirping throughout the night, in anticipation of a dawn that will not arrive for many hours. This seriously disrupts their sleep patterns, preventing them from resting. The dawn chorus from a dark site begins much earlier than the dawn chorus under light polluted skies. Under dark skies, birds begin singing the dawn chorus as soon as dawn begins. However, under light polluted skies, birds do not begin singing until the dawn Sun has finally overpowered the light pollution. This restricts the birds ability to be the early bird that catches the worm. For more details, please see the RSPB website.

In the UK, Owl numbers are falling (see this BBC News article). Light pollution reduces the suitable area of feeding habitat for owls and other night-hunting birds (see the International Dark Sky Association).

Light pollution may be the reason for the large decline in UK Sparrow and Thrush numbers (The independent). This decline of both species may also be due to light pollution assisting birds of prey (BBC News) or reducing insect numbers. Sea-birds are also affected by light pollution (PRBO conservation).

Most songbirds evolved to migrate at night, when predators retire and winds subside. Lighting increases the mortality rate of wild birds, via fatal collisions with illuminated buildings (see the Fatal Light Awarness Program website). In the USA and Canada there is growing concern over the increasing number of migrant birds dying as a result of hitting illuminated buildings at night. The dead and wounded birds are often scavenged by rats, raccoons, cats and seagulls, etc. Net result: Songbirds diminish while scavengers thrive!

Needless to say, birdwatchers would like buildings to extinguish all interior building lights and non-essential outdoor lights (especially all floodlighting) during migration time, and to shield essential lights.

Since 1990, Chicago's Hancock Centre has doused its ornamental night-time lighting during spring and autumn to save the nearly 1,500 birds that - nightly - met with an abrupt death when they crashed into the tower during migration season, mistaking its illumination for stars or the moon. In 2000, volunteers gathered over 3,000 dead and wounded birds of 138 different species in Toronto. In 2006, a further 2,000 dead birds from 89 different species were put on display at the Royal Ontario Museum to ecourage people to turn off unnecessary lights (see Royal Ontario Museum; Canada.com; CBC News; Lights-out policy in cities saves birds)

The effect of lighting on birds has been graphically demonstrated on the anniversaries of the September 11th terrorists attacks on New-York's World Trade Centre. The New York authorities commemorate the murder of thousands of innocent people in that attack by, oddly enough, murdering thousands of innocent birds, by shining two high powered beams of light into the sky. As a witness explains: "The beams were visibly filled with birds for their entire height, looking like clouds of bugs. Their twittering was audible. There were so many birds, it was impossible to track any one individual for any length of time. I did see one bird that circled in and out of the uptown beam six times before I lost track. Each time, the bird stayed in the light for from 3 to 9 seconds. I found all this extremely disturbing." It takes a song-bird about a week to lay down a gram of fat, fuel for about 120 miles of its long-distance migration - which can all be lost due to bad lighting.

The effect on Insects

Insects are also detrimentally affected by bad lighting. Lights attract insects which are destined to be either killed instantly with the heat of the bulb, or to circle the light until they are too exhausted either to feed or procreate.

To quote from a BBC News article: "It is only a humble beetle but the ability to use moonlight as a compass may be widespread in the animal kingdom. Many birds use the Sun, Moon or stars as a marker in the sky. But the African dung beetle seems to have even more remarkable skills. It uses the pattern created when moonlight strikes tiny particles in the atmosphere (polarisation) to orient itself and travel in a straight line. When nights are cloudy, its progress across the ground is more random and it tends to go around in circles."

Lights attract a wide variety of insects, which can cause problems around your home, especially in the summer months. If your lights are frequently on, insects will get into the habit of nesting and feeding around your lights even when they are turned off. So if you have problems with insects, make sure you minimise the use of your lights!

Glowworms and fireflies are severely affected by ambient light and glare caused by light pollution (BBC News), which scientific researchers in entomology believe seriously precludes their ability to seek and find mates using their own much dimmer bio-luminescence. That threatens species' survival at the very core. Moths are also effected (see the Butterfly Conservation website).

The effect on Trees

Trees provide entire ecosystems to many animal and insect species, and are detrimentally affected by light pollution. Trees need to adjust to seasonal variations, and artificial light prevents them from doing so - many trees are prevented from loosing their leaves by bad lighting. This has an effect on the wildlife that depend on the trees as their natural habitat. For example, many birds are unable to nest in trees due to the surrounding light pollution.

Further reading...

News stories

February, 2006
Night lights mean lights-out for snakes
"Artificial lighting helps humans play in the dark, but researchers think it might be hurting some animals nighttime activities, particularly snakes."

October, 2005
BBC News: New York dims lights to aid birds
"The city that never sleeps is turning out the lights on dozens of skyscrapers in the hope of protecting birds distracted from migration paths. Every night in autumn, hundreds collide with Manhattan's high-rise towers.
Owners of tall buildings are being urged to dim their lights to save the lives of night-migrating birds, while reducing energy costs. "

July, 2005
The Independent: Town tormented by yob birds calls in the Seagull Terminator
"With no predators, plenty of food and street lighting that enabled them to feed at night they [seagulls] flourished."

July, 2005
BBC News: "The three main threats to the glow-worm are changes in habitat, artificial lighting and pesticides."

April, 2005
The Leicester Mercury: Watt a carry on
"New high-powered lamps installed in the village are so intense the residents claim they can read books in their gardens in the middle of the night. They say the bulbs burn so bright they have confused birds into singing 24 hours a day. People living in Wood Lane, which is one of the worst affected areas, say the street now appears to be floodlit.
Quorn Parish Council, which is calling for the lights to be dimmed, said the changes had stunned local residents. Clerk Kathryn Paterson said: "It looks like lighting from a retail park. It is incredibly bright and not at all what you would expect from a country lane. On the first evening after they were installed, birds were still singing, even though it was very dark, because the street lamps had convinced them it was still light. Have street lighting by all means, but we don't want the whole area lit up like this."
Parish council vice chairman Phil Child said: "It did come as a bit of a shock to people compared with the low-level lighting we have before. "To their credit, Leicestershire County Council has agreed to reduce the wattage, so we will have to wait to see what happens." "

April, 2005
Spring storm kills many birds in Yellowstone
"A swirling snow squall that settled over Yellowstone National Park early Wednesday left behind more than 120 dead birds scattered on roofs, parking lots and wooded areas around Canyon Village.
The carnage at Canyon - precipitated by the storm and possibly made worse by the bright lights there - may also prompt changes in how the park illuminates some of its developed areas. McEneaney said he plans on recommending that lights be aimed downward to reduce the risk of attracting birds at night.
"There's a good lesson to be learned here," he said. "The lesson is we need to modify our lighting." "

June, 2004
CNN: Lights-out policy in cities saves birds. "PHILADELPHIA, Pennsylvania (Reuters) -- Turning out the lights of city skyscrapers is helping to save the lives of thousands of birds migrating across North American cities to their spring breeding grounds."

April, 13th, 2004
BBC News: Migrating birds rely on sunsets. "US scientists believe they have made an important breakthrough in the mystery of how migrating birds manage to navigate thousands of kilometres and arrive at exactly the same spot each year. ... The researchers concluded that each night the thrushes must have "recalibrated" their inbuilt compass from the position of the setting Sun." (If birds depend on light to navigate, it is no wonder that light pollution kills and confuses so many birds.)
Return to BAA CfDS homepage