Ecological light pollution

Ecological light pollution is the term used to describe how the presence of artificial light disrupts the lives of individual organisms and of the structure of ecosystems as a whole.

The effect that artificial light has upon organisms is highly variable, and ranges from beneficial (e.g. increased ability for predator species to observe prey) to immediately fatal (e.g. moths that are attracted to incandescent lanterns and are killed by the heat). It is also possible for light at night to be both beneficial and damaging for a species. As an example, humans benefit from using artificial light to extend the time available for work and play, but the light disrupts the human circadian rhythm, and the resulting stress is damaging to health.

Through the various effects that light pollution has on individual species, the ecology of regions is affected. In the case where two species occupy an identical niche, the population frequency of each species may be changed by the introduction of artificial light if they are not equally affected by light at night. For example, some species of spiders avoid lit areas, while other species are happy to build their spider web directly on a lamp post. Since lamp posts attract many flying insects, the spiders that don't mind light gain an advantage over the spiders that avoid it, and consequently become more common. Changes in these species frequencies can then have knock-on effects, as the interactions between these species and others in the ecosystem are affected and food webs are altered. These ripple effects can eventually affect even diurnal plants and animals. As an example, changes in the activity of night active insects can change the survival rates of night blooming plants, which may provide food or shelter for diurnal animals.

The study of ecological light pollution is still in its infancy, but it is already clear that the introduction of artificial light at night has had comparable, or perhaps greater, effect to other types of anthropogenic changes such as toxic pollution, land use change, and climate change due to increases in the concentration of green house gasses.

Effects of light pollution on individual organisms

Insects

The attraction of insects to artificial light is one of the most well known examples of the effect of light at night on organisms.

The compound eye of moths results in fatal attraction to light.

Turtles

Loggerhead sea turtles are attracted to street and hotel lights rather than to the ocean.

Zooplankton

Zooplankton (e.g. Daphnia) exhibit diel vertical migration. That is, they actively change their vertical position inside of lakes throughout the day. In lakes with fish, the primary driver for their migration is light level, because small fish visually prey on them. The introduction of light through skyglow reduces the height to which they can ascend during the night. Because zooplankton feed on the phytoplankton that form algae, the decrease in their predation upon phytoplankton may increase the chance of algal blooms, which can kill off the lakes' plants and lower water quality.

Polarized light pollution

Artificial planar surfaces, such as glass windows or asphalt reflect highly polarized light. Many insects are attracted to polarized surfaces, because polarization is usually an indicator for water. This effect is called polarized light pollution, and although it is certainly a form of ecological photopollution, "ecological light pollution" usually refers to the impact of artificial light on organisms.

External Links

• Indexed list of peer reviewed ecological light pollution research papers
• Fatal Light Awareness Program (FLAP) (Toronto)
• "Ecological Consequences of Artificial Night Lighting" (2002 conference, by the Urban Wildlands Group)
• International Dark-Sky Association
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