Guided by the light

As seen from space, Rappahannock County is a dark spot on an increasingly bright map.
As seen from space, Rappahannock County is a dark spot on an increasingly bright map. Courtesy of PEC. Source: NOAA
By Julie Bolthouse

Light pollution has been a recent topic of discussion in Rappahannock County. From flood lights glaring into adjacent neighbors’ windows to the dimming of the night sky — these are both valid concerns. But an often overlooked impact is how light pollution affects our natural environment.

Various biological rhythms of wildlife and plants have evolved with the natural light cycles. Artificial night lighting can disrupt these patterns, affecting migration, feeding, breeding and even seasonal foliage changes.

When looking at NASA’s 2012 Earth Observatory data of night lighting in the United States, Rappahannock County is one of the darkest counties in Virginia. Not surprisingly, it also has a high percentage of forested land cover and unfragmented habitat, making it an ecological haven for many species.

Many bird species, such as warblers, vireos, thrushes and tanagers, migrate at night using guiding lights from the moon, stars and setting sun. Migrating at night helps them avoid predation under the cover of darkness, provides cooler temperatures, and enables them to avoid daytime wind gusts that make it more difficult to maintain a steady course. However, artificial lights can attract and disorient these birds, causing them to use up precious energy and, in some extreme cases, die. In fact, there is a phenomenon known as “towerkill,” where tall, lit antenna towers have been known to attract migratory birds that fly near them in cloudy weather conditions, causing them to circle until they collide with each other or the structure.

Amphibians and reptiles are also affected by light pollution. Similar to birds, some amphibians and reptiles use light for navigation when migrating to breeding grounds and artificial lights can disorient them. These secretive creatures forage and communicate under the cover of night. Without darkness, their foraging and calling has been shown to decrease, affecting their health and reducing reproduction. Melatonin disruptions due to extended exposure to light have also been documented in salamanders. Melatonin is the master hormone regulated by photoperiods. Longer exposure to light reduces its production, leading to a wide variety of physiological and behavioral problems.

We have all seen the effect of night lights on moths and other nocturnal insects that seem excessively drawn to circle and collide until their death. This phenomenon, called flight-to-light, is not well understood, but it is suspected that nocturnal insects use light from the moon and stars to navigate, and artificial lights cause a kind of short-circuit in their brain. However, this isn’t the only effect our lights have on these beautiful pollinators of the night. Predators have been observed to hunt at artificial lights, exploiting the high densities of prey insects attracted. There is also evidence that artificial night lighting can affect reproduction by inhibiting release of sex pheromones by female moths, suppressing oviposition, or encouraging females to lay eggs at unusually high densities in unsuitable areas near lights.

Even plants can be affected by artificial light at night. Moths and bats are pollinators that are sometimes overlooked because they often work under the cover of night. Plant species that bloom at night depend on these night pollinators, though, and can be indirectly affected if the pollinators’ populations are reduced or deterred by nearby light pollution. Night lighting on trees, especially in the red to infrared range of the spectrum, can encourage growth and photosynthesis beyond the time when it is safe to do so. Trees in our area lose their leaves in the autumn and go into a protective dormancy. When trees keep their leaves into winter they are susceptible to harsh weather conditions and may not survive.

So what can you do to help? You can reduce your night light footprint by using motion sensors or only turning on outdoor lights when needed, pointing lights downward and using shields that direct it to the intended area and using more subtle lighting with lower wattage. You can also support Rappahannock County’s effort to have the board of supervisors seek clear legislative authority from the General Assembly to regulate residential lighting and dark skies.

Julie Bolthouse ( is a land use officer for the Piedmont Environmental Council. For conservation questions specific to Rappahannock County, contact PEC’s Carolyn Sedgwick at

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