Ecological and Species Impact

The ecological impacts of light pollution are wide-ranging, but essentially boil down to the fact that  artificial light is disrupting the natural light-induced patterns of ecosystems and the species within them. “Until very recently, darkness has been inescapable part of the environment and natural history of our planet. Accordingly, life has evolved and adapted to daily, monthly, and annual cycles in the level of ambient light” (Gallaway, Olsen, and Mitchell 2). Unnatural alteration of such light patterns can disrupt factors such as feeding, reproduction, sleeping, and migration, depending on the system and species. One notable problem is that constant artificial light breaks down niche barriers based on night/day foraging. This can disrupt interactions between groups of species that partition resources based on light gradients (Longcore and Rich). Similarly, excess light can disrupt predator-prey relationships. Prey are vulnerable to predators for longer periods of time, but also have potentially more foraging time. These are just some examples of the widespread effects light pollution can have on local ecosystems and the species within them. The specific effects of light pollution on various species are detailed below.

Birds

Birds Trapped in a Light Beam
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Many bird species, particularly those that migrate or hunt at night, are very negatively impacted by light pollution. Night-lights can disorient birds, causing them to lose their sense of direction, collide with buildings, or become fixed on the light beam, flying towards it until they are physically unable to any longer. In North America alone, nearly 100 million birds a year die from collisions with lighted buildings and towers.



Insects

As many people know, insects are often drawn to artificial light sources, and can hover around them all night. Such light-induced activity wastes the energy of insects, leaving less energy for necessary activities like mating and migration. This, along with subsequent increased vulnerability to nocturnal predators, has resulted in population reductions in some insect species (International Dark-Sky Association).

Insects like moths are often attracted to artificial light sources

Sea Turtles

Sea turtles generally nest and hatch nocturnally, and coastal light pollution has been shown to disrupt the visual cues sea turtles rely on for such activities. As a result of this light, sea turtles often become disoriented, and many times fail to make it to the sea as a result. Instead, they move towards the light source, thereby becoming more exposed to predators and other dangers (Howell).

A nocturnally nesting sea turtle

Nocturnal Mammals

Light pollution negatively impacts nocturnal mammals in various ways, including disruption of foraging patterns and increased predation risk. According to some studies, nocturnal mammals can generally respond to artificial lighting in two ways: the first is that they continue to forage under bright light, thereby significantly increasing predation risk. The second is that they shy away from the artificial light, which minimizes predation risk but also reduces food consumption, leading to decreased body mass (Longcore and Rich).

The black-footed ferret, a nocturnal mammal impacted by light pollution
http://www.pc.gc.ca/pn-np/sk/grasslands/natcul/~/media/pn-np/sk/grasslands/natcul/6/bff_fa1.ashx?w=590&h=392&as=1