Light pollution has been, traditionally, seen as concentrating near or within high population areas, due to the high use of nighttime lights along streets, public areas, residences, and businesses. While much of the public is aware of a concept of light pollution, its ill effects and influences on society and nature are less clear to most people. Furthermore, how light pollution is defined has not always been agreed, as many see nightlight as a benefit, while others simply see light pollution as more of an aesthetics issue.[1] In fact, within geography, darkness has not always been attributed as a positive quality in urban contexts. Authors have called for a reassessment of dark spaces within urban areas so that greater awareness and perception of how light pollution can have detrimental effects is more evident.[2] However, light pollution is generally defined as light that trespasses, over-illuminates, and interferes with astronomical observation.

Impact of Light Pollution on Health

Light pollution also has clear health and environmental detriments, including harming abilities to sleep, increasing possible cancer, and harming animal behavior, including migration. Linkages with health and wildlife have been a key focus in the geography literature. One study showed that there is a 110% increase in prostate cancer probability in countries with higher levels of light pollution. This is seen to be driven by circadian disruption.[3] In light of some urban or built-up regions that have very high levels of light pollution, such as in Hong Kong where it was determined that the urban areas are up to fifteen times brighter in the night, are evident. [4]

Light pollution along the Eastern Seaboard in the United States. Image: NASA.

Light Pollution Affects Migratory Birds

For animals, light pollution disruptions might be severe enough to threaten some species. Migratory birds, as one example, were found to be affected in their migratory pattern based on urban light pollution. In particular, juvenile birds undertaking their first migration are more likely to be affected.[5] Among various species, certain bats in Europe have been found to be negatively affected in their nighttime behavior by artificial light, leading them to be increasingly threatened.[6] Some species of bats, however, were found to be better adapted to artificial light conditions.

Conservation and Light Pollution

While campaigners continue to see the need to educate about light pollution, one idea has been to introduce world heritage or some type of protection status for places so that they can remain “dark” during nighttime hours. This has been proposed, for instance, for places that have significance for astronomy, where observatories may increasingly find it harder to make measurements in the night sky as glow and other forms of pollution interfere with measurements.[7] Particularly as artificial light has affected a variety of species, day and nighttime, where varieties of species have now been forced to adapt to artificial light, even in areas that might otherwise be normally be protected from other sources of pollution.[8] In effect, creating a type of protection status can bring greater awareness and possible protection from light pollution.

What is evident is that light pollution likely continues to be one of the less well known forms of pollution. The public still sees it as more of an annoyance, despite the scientific community demonstrating that clear health risks could be associated with light pollution. Threats to certain species and the environment are also other aspects threatened by light pollution. Geographers have documented how light pollution attitudes could be changed, while campaigners have even considered giving world heritage status to places so that darkness can be better maintained for locations important to the scientific and other communities.

References

[1] For more on a recent study showing that light pollution is largely seen as an aesthetics issue, see: Lyytimäki, J. & Rinne, J. (2013) Voices for the darkness: online survey on public perceptions on light pollution as an environmental problem. Journal of Integrative Environmental Sciences. [Online] 10 (2), 127–139. Available from: doi:10.1080/1943815X.2013.824487.

[2] For a recent assessment of perceptions on light and darkness in urban spaces, see: Edensor, T. (2015) The gloomy city: Rethinking the relationship between light and dark. Urban Studies. [Online] 52 (3), 422–438. Available from: doi:10.1177/0042098013504009.

[3] For more on the study linking light pollution and prostate cancer, see: Kloog, I., Haim, A., Stevens, R.G. & Portnov, B.A. (2009) Global Co‐Distribution of Light at Night (LAN) and Cancers of Prostate, Colon, and Lung in Men. Chronobiology International. [Online] 26 (1), 108–125. Available from: doi:10.1080/07420520802694020.

[4] For more on Honk Kong’s light pollution levels and monitoring, see: Pun, C.S.J., So, C.W., Leung, W.Y. & Wong, C.F. (2014) Contributions of artificial lighting sources on light pollution in Hong Kong measured through a night sky brightness monitoring network. Journal of Quantitative Spectroscopy and Radiative Transfer. [Online] 139, 90–108. Available from: doi:10.1016/j.jqsrt.2013.12.014.

[5] For more on bird migration and light pollution, see: La Sorte, F.A., Fink, D., Buler, J.J., Farnsworth, A., et al. (2017) Seasonal associations with urban light pollution for nocturnally migrating bird populations. Global Change Biology. [Online] Available from: doi:10.1111/gcb.13792 [Accessed: 7 August 2017].

[6] For more on a study on bats and artificial light, see: Lacoeuilhe, A., Machon, N., Julien, J.-F., Le Bocq, A., et al. (2014) The Influence of Low Intensities of Light Pollution on Bat Communities in a Semi-Natural Context John Morgan Ratcliffe (ed.). PLoS ONE. [Online] 9 (10), e103042. Available from: doi:10.1371/journal.pone.0103042.

[7] For more on a recent meeting discussing how a world heritage status framework, such as given by UNESCO, could be utilized to keep places dark, see: Smith, M.G. (2015) Session 21.6: Preserving Dark Skies and Protecting Against Light Pollution in a World Heritage Framework. Proceedings of the International Astronomical Union. [Online] 11 (A29A), 480–489. Available from: doi:10.1017/S1743921316003628.

[8] For more on types of species affected by light pollution, see: Gaston, K.J., Duffy, J.P., Gaston, S., Bennie, J., et al. (2014) Human alteration of natural light cycles: causes and ecological consequences. Oecologia. [Online] 176 (4), 917–931. Available from: doi:10.1007/s00442-014-3088-2.

See Also