Artificial light at night could change the behavior of all animals, not just humans

This article was originally published in The Conversation (will open in a new tab). The publication published an article in Expert Voices: Op-Ed & Insights on

Teresa Jones (will open in a new tab)Associate Professor, Department of Evolution and Behavior, University of Melbourne.

Catherine McNamara (will open in a new tab)postdoctoral fellow, University of Melbourne

When the moon rises on a warm evening in early summer, thousands of baby turtles appear and begin their perilous journey to the ocean, while millions of moths and fireflies take to the air to begin the complex process of finding a mate.

This nocturnal behavior and many others like it have evolved to take advantage of the darkness of the night. However, today they are under increasing threat due to the presence of artificial lighting.

On the subject: Is it possible to see stars in a lighted sky?

At its core, artificial light at night (such as from streetlights) masks natural light cycles. Its presence blurs the transition from day to night and can weaken the moon’s natural cycle. We are increasingly aware that this has significant physiological and behavioral implications, including changes in hormones associated with some species’ day-night cycles and their seasonal breeding, as well as changes in the timing of daily activities such as sleeping, foraging or mating. (will open in a new tab).

Increasing intensity and distribution of artificial light at night (estimated at 2-6% per year). (will open in a new tab)) makes it one of the fastest growing global pollutants. Its presence was associated with changes in the structure of animal communities. (will open in a new tab) and biodiversity decline (will open in a new tab).

How animals are affected by artificial lighting

Night light can both attract and repel. Animals living near urban environments are often attracted to artificial lighting. Turtles can turn their backs on the safety of the oceans and move inland where they can be hit by a vehicle or drown in a pool. Thousands of moths and other invertebrates become trapped and disoriented around city lights until they fall to the ground or die without finding a mate. Female fireflies produce bioluminescent signals to attract a mate, but this light cannot compete with street lighting, so they may not breed either.

Millions of birds every year (will open in a new tab) injured or killed because they were trapped in the beams of bright city lights. They are disoriented and crash into brightly lit structures or get distracted from their natural migration paths. (will open in a new tab) into an urban environment with limited resources and food and a large number of predators.

Other animals, such as bats and small mammals, avoid light or avoid it altogether. This effectively reduces the habitat and resources available for them to live and reproduce. For these species, street lighting is a form of habitat destruction where light, rather than a road (or perhaps both), cuts through the darkness needed for their natural habitat. Unlike humans, who may return to their home and block out the light, wild animals may have no choice but to leave.

For some species, night lighting provides some advantages. Species that are normally only active during the day may increase their feeding time. Night spiders and geckos often visit places around fires because they can feast on the many insects they are attracted to. However, while these species may benefit on the surface, this does not mean that there are no hidden costs. Studies with insects and spiders show that exposure to light at night can affect immune function. (will open in a new tab) and health and change their growth, development and number of offspring (will open in a new tab).

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How can we fix this?

There are several real examples of effective mitigation strategies. In Florida, many urban beaches use amber-colored lighting (which is less attractive to turtles) and turn off street lights. (will open in a new tab) during the turtle nesting season. On Philip Island, Victoria, home to over a million short-tailed petrels, many of the new street lights are also amber and off on known migration routes. (will open in a new tab) during fledging to reduce mortality.

In New York, the Tribute in Light (consisting of 88 vertical floodlights visible from almost 100 km) is switched off for 20 minutes. (will open in a new tab) to allow disoriented birds (and bats) to escape and reduce the structure’s attractiveness to migrating animals.

In all cases, these strategies have reduced the environmental impact of night lighting and saved the lives of countless animals.

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However, while these targeted measures are effective, they do not solve what could be another global biodiversity crisis. Outdoor lighting standards exist in many countries and several independent guidelines have been written, but these are not always enforceable and are often open to interpretation.

As a person you can help, for example:

In one sense, light pollution is relatively easy to fix – we can simply turn off the lights and let the moonlight naturally illuminate the night.

From a logistical point of view, this is basically not feasible, since the light is used for the benefit of people who are often reluctant to give it up. However, while artificial light allows humans to use the night to work, relax and play, it is also catastrophically changing the habitats of many other species.

In the absence of blackouts, there are other management approaches we can use to mitigate their impact. We can limit their number; reduce their intensity and duration of their action; and possibly change their color. Animal species vary in their sensitivity to different colors of light, and studies show that some colors (amber and red) may be less harmful than the blue-saturated white light that is becoming commonplace around the world.

This article is republished from The Conversation (will open in a new tab) under a Creative Commons license. Read original article (will open in a new tab).

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