Ecological and Organismic Effects of Light Pollution

Abstract

Abstract Since the invention of the electric light bulb in 1879, a significant portion of the planet has been transformed from experiencing a natural pattern of light and dark determined by the sun, moon, stars and occasional other transient lights to being subjected to intermittent and perpetual illumination from human civilisation that is unprecedented in the history of Earth. The pervasiveness of this phenomenon and its exponential growth has measurable and significant consequences for living organisms. The results of recent research have extended knowledge about the geographic scope and specific impacts of artificial night lighting on animal behaviour, physiological processes and ecological interactions across a range of taxa and its broader ecosystem effects. Key Concepts Artificial lighting alters natural patterns of light and dark over large areas of Earth's surface. Most species have circadian rhythms that are entrained by cycles of light and dark that can be affected by artificial lighting. Organisms vary widely in their perception of intensity and wavelengths of light; what is perceived as ‘dark’ by humans may be bright to another species. Many species specialise in activities in particular lighting conditions (either day versus night or illumination levels during a month or during the course of a night) and this temporal partitioning can be disrupted by artificial lighting. Nocturnal processes of repair and recovery, including production of essential hormones such as melatonin, can be interrupted by artificial night lighting. Decisions to forage at night are related to lighting levels; species weigh the risk of predation against need to seek food. Additional light at night tends to favour predators, except when groups of prey species, such as a flock of birds or a school of fish, exhibit a communal vigilance for predators. Artificial lighting can interfere with spatial orientation of organisms, resulting in direct mortality or unnecessary movements (e.g. migrating birds, hatchling sea turtles, insects at lights). Adverse effects of artificial night lighting can be reduced through careful consideration of need, spectrum, intensity, direction and duration of light used.