Light Pollution Research Shows Humans and Wildlife Can Coexist

It is no secret that light pollution has an impact on wildlife.

For billions of years, all life has relied on Earth’s predictable rhythm of day and night. It’s encoded in the DNA of all plants and animals. By introducing artificial light to the nighttime landscape, humans have disrupted this natural cycle and altered species’ behavior and biology. Particularly, light pollution can disorient or inappropriately attract species to lit areas, interfere with ecological interactions like predator-prey relationships, interrupt habitat connectivity, disrupt natural circadian rhythms, and influence species’ ability to detect seasonality.

For decades, the research community has sounded the alarm on the ecological impacts of light pollution and in recent years there has been a stark increase of studies on the topic. IDA’s Artificial Light at Night (ALAN) Research Literature Database indicates that the number of academic studies focused on animals and light pollution has more than quadrupled in the last five years. Here’s a snapshot of what these studies are bringing to light and what we can do about it:

Light Pollution is Contributing Significantly to Insect Apocalypse

Insects are very sensitive to artificial light at night which can affect their circadian rhythms, mating rituals, and ability to navigate. Studies have shown that lights at night impact nocturnal pollinators, including many species of moths.

“We strongly believe artificial light at night – in combination with habitat loss, chemical pollution, invasive species, and climate change – is driving insect declines…We posit here that artificial light at night is another important – but often overlooked – bringer of the insect apocalypse.” – Avalon C.S. Owens et al.

There has been a particular focus on insects lately as researchers recently identified light pollution as a ‘key bringer of the insect apocalypse’ and another study warned that fireflies could face global extinction due to excessive light at night. Severe insect decline is particularly concerning considering their place in the food web and important role in pollinating food crops.

Light Polluted Cities are Deadly for Birds

The Yale School of Forestry and Environmental Studies reports that 40% of the world’s 11,000 bird species are in decline. Several studies indicate that light pollution plays a major factor in this decline, causing fatal collisions with lit buildings, impacting bird’s ability to navigate, and even influencing the transmission of diseases like West Nile Virus.

Bright Lights Disorient Sea Turtle Hatchlings

Of all the species threatened by shrinking habitats and light pollution, sea turtles are among the most at risk for extinction. Several turtle species are listed as either threatened or endangered in the U.S. and by international organizations, with populations rapidly declining over the past 100 years. Sea turtles are particularly impacted by light pollution, as their hatchlings often become confused by the bright lights of cities as they attempt to navigate from their nests on land to their home in the ocean.

Humans and Wildlife Can Coexist

“With careful planning and collaboration, usually with nearby jurisdictions, managers of parks and other protected lands can be leaders in the control of light pollution and increase enjoyment of natural lands from inner city parks to wilderness areas.” – Travis Longcore and Catherine Rich.

Artificial light at night does have an impact on the natural nighttime ecosystem, but there are steps we can take to limit that impact. In their report, Artificial Night Lighting and Protected Lands: Ecological Effects and Management Approaches, Travis Longcore and Catherine Rich offer land managers practical approaches for lighting environments for human use while also mitigating impacts on wildlife. They provide guidance on how to thoughtfully light various habitats such as shorelines, deserts, dense forests, and urban settings. By carefully considering the characteristics of a habitat and lighting needs, direction, duration, color spectrum, and intensity, landowners can create environments that respect both human and animal needs.

A pale-colored path can be just as effective as electric lights in some park situations.

The more focused light can be on its target, the less it will affect other species.

Embedded lights allow wayfinding with minimal intensity and good directional control.

Timed lights may affect species negatively during the transitional period of dusk, but may reduce impacts later at night.

Motion- and heat-detecting lights provide illumination only when it is needed

Yellow light that does not contain blue or ultraviolet wavelengths attracts far fewer insects.

Cities are affected by altered light environments, which are exploited by synanthropic species such as crows and some bat species.

Lights in desert scrublands are visible for long distances and night lighting affects a disproportionate fraction of the wildlife because high daytime temperatures induce nocturnal activity patterns.

Grasslands are vulnerable to disruption from even distant lights because of their open character. Fireflies, often found in wet grasslands, can have their signals disrupted or be excluded by high illumination, while some grassland bird species, such as black-tailed godwit (Limosa limosa), have been shown to avoid streetlights in selecting nest sites (De Molenaar et al. 2006).

Predator–prey interactions are affected by artificial lights during long nights on the tundra.

Species of the deciduous forest are adapted to the lower light levels found under the canopy. Flying squirrels and salamanders will delay their foraging under artificial lights.

Light in wetlands can suppress diel vertical migration of zooplankton and influence foraging behavior of amphibians.

Lights along rivers and streams can disrupt predator–prey interactions, such as seals hunting salmon under lights.

Beach environments are vulnerable to the effects of anthropogenic light because of their open nature. Hatchling sea turtles are easily disoriented by onshore lights or sky glow and patterns of nocturnal foraging by shorebirds are also affected.

Cruise ships and squid boats are just two of the sources of artificial lighting on the oceans that attract seabirds and migrating songbirds.

Hover mouse to pause the slider. Graphics: DelBusso in Longore and Rich (NPS: NRSS:NSNS:NR-2017:1493)

Looking for more research on light pollution and wildlife? Check out IDA’s Artificial Light at Night (ALAN) Research Literature Database.