More Evidence of Light Pollution Harm to Animals

Artificial Outdoor Light Negatively Affects Many Wildlife Species

Jan 9, 2009

While many people are aware of the problems outdoor lighting create for sea turtles and migratory birds, few understand its wide-ranging impacts on other wildlife.

Alteration of the environment by outdoor lighting has been implicated in changes in the behavior of everything from aquatic invertebrates to migratory birds. While not all of these changes are negative, the majority do create problems for wildlife.

Effects of Commercial Outdoor Lighting on Migratory Birds

Flocks of migratory birds crashing into brightly lit city buildings or being sent off course by flashing lights on communication towers have been documented for many years. Declines in some seabird population have been linked to increased outdoor lighting. These discoveries marked the first steps toward efforts to reduce light pollution.

Sea Turtle Nest Sites and Hatchling Behavior

The next species to receive attention were the sea turtles coming ashore to nest. Hatchling sea turtles wandering into brightly lit beachside restaurants triggered concern, as did the discovery that light pollution affects where females lay their eggs. Changes to nest sites may increase egg predation, a serious problem for the many endangered sea turtle species.

Fish and Amphibians Suffer From Light Pollution

Salamanders are more easily found by predators as they forage at night. Light levels also affect behavior and possibly territorial control. Light pollution may also disrupt the migration of some partially terrestrial salamanders back to their breeding ponds.

Frogs, already facing serious threats from chytrid fungal disease, are affected by artificial light in many ways. Reproductive activity is inhibited in some species, intrspecific visual communication may be disrupted and predation may increase as the frogs are more easily visible. Conversely, light pollution may draw more insect species making foraging easier.

In the Pacific Northwest, changes in migration behavior of salmon, herring and sand lance have been noted in areas where there is increased artificial lighting. Increased predation on these fish species, some of which are endangered, has occurred as a result, with predators utilizing the light pollution at fish ladders and spillways to forage later into the evening.

Effects of Artificial Outdoor Lights on Insects and Invertebrates

Lakes and coastal waterways near cities are highly affected by commercial outdoor lighting including neon signs, street lamps and brightly lit buildings. Light levels from these sources mimic full moon effects to a depth of 3 meters. The effects on aquatic invertebrates of this constant light are just beginning to be studied.

Recently published research into the effects of polarized outdoor light on insects shows that species such as dragonflies, in search of water on which to lay eggs, may be diverted into oil slicks, buildings, dark cars and water puddles on paved roads. These surfaces are more strongly polarized by artificial light than natural water sources.

In another study, a link has been made between artificial outdoor light and increased numbers of midges which carry the cholera bacteria. These biting insects prefer cloudy waters, full of nutrients. The cloudy waters produce greater polarized reflections, drawing the midges. In this case the information may be used to control midge populations and potentially limit the spread of cholera.

The variety of species negatively affected by artificial lights, especially in urban, commercial settings, indicates the importance of tackling light pollution. Further study is likely to add to the evidence in favor of decreasing artificial light usage.

The copyright of the article More Evidence of Light Pollution Harm to Animals in Wildlife Conservation is owned by Dawn M. Smith. Permission to republish More Evidence of Light Pollution Harm to Animals in print or online must be granted by the author in writing.

Feb 18, 2009 2:34 AM

Guest :

You are right that turtles can be misled by artificial light. But this turtle was not suffering from light pollution - the photo was taken on Heron Island, where artificial light is strictly controlled. This species is often seen out of the water in daylight, especially in the early morning. What this turtle was being suffering from was drought - sand that is too dry is unsuitable for egg laying.

Feb 24, 2009 6:31 AM

Dawn M. Smith :

Thank you for your input on the turtle photo. All of the pictures represent species affected but none, to my knowledge, are of specific individuals that have been affected by light pollution.
Your message is a good reminder that light pollution is not the only threat endangered sea turtles face.

Mar 28, 2009 9:23 AM

Guest :

i agree it is sad how many hatchlings are killed because they are misled by the light.

Jun 29, 2009 4:12 PM

Guest :

Light pollution will one day be seen as the greatest "hidden" threat to sustainability in Life On Earth. The popular myth is that light is good and so more is better? Sadly this is not so - it just increase the profits of utilities at the expense of our collective future. You may not WANT to believe this but the CfDS has its new 2009 handbook "Blinded by the Light?". Learn the truth and know your future - it is not as rosy as you want it to be?