Posted by: pointreyesscience | August 6, 2009

Natural Soundscapes and Dark Skies

Every year the natural sights and sounds of national parks are fading in the face of overpowering human noises and lights. To preserve natural and cultural resources in the face of light and noise disturbances, the National Park Service is actively managing its natural soundscapes and dark night skies.

Natural Soundscapes

A soundscape is the human perception of an acoustical environment. An acoustical environment is made up of many sounds like wind, water, wildlife, vegetation, and even cultural sounds like battle reenactments, tribal ceremonies, or quiet reverence. Some sounds come from biological resources, like bird calls and noise from bat echolocation. Others, like the sound of falling water or wind in trees, originate from physical processes.

Wildlife can be adversely affected by intrusive sounds in a natural soundscape. Sound impacts can have harsh implications for wildlife health, particularly when combined with other stressors like winter weather, disease, insect harassment and food shortages. Wildlife has been known to suffer adverse physiological and behavioral changes due to noise disturbance. Animals may experience immune system suppression, increased heart rates, and high respiration rates, and release stress-related hormones. When noise masks natural sounds, wildlife may be unable to hear important environmental cues or signals. Songbirds faced with noises are known to sing louder than birds in quiet environments, expending extra precious energy when calling to attract mates or warn other birds of predators. Energy is also wasted when animals, from mountain goats to whales, flee from invasive noise. Noise sometimes prompts wildlife to flee its territory, resulting in low reproduction rates.

Muir Woods soundscape monitoring volunteers recording ambient noises

Muir Woods soundscape monitoring volunteers recording ambient noises

Park managers throughout the National Park System consider data about the loudness and pitches of sounds in their park. The natural ambient sound level (the baseline sound emitted by natural and cultural resources) varies from park to park. Certain parks have found it appropriate to restrict vehicle and personal water craft use in order to reduce noise disturbances. Others have made changes in park operations, like reducing the use of a loud generator at a ranger station. The National Park Service has partnered with the Federal Aviation Administration under the National Parks Air Tour Management Act of 2000 to reduce the impact of commercial air tour operations on natural park soundscapes.

Human sounds in national parks come may come from roads, hikers, vehicles, or maintenance activities. Intrusive sounds affect humans as well as wildlife. Noise may negatively impact cultural, archaeological and historic resources, as well as visitor experiences.

Ways to enjoy natural sounds:
1) close your eyes
2) count sounds
3) walk and listen
4) appreciate sounds
5) listen to landscapes
6) walk in the wild
7) chat like an animal

For more information, check out:
The NPS Natural Sounds Program
Golden Gate National Recreation Area – Soundscape / Noise
The Acoustic Ecology Institute
The Nature Sounds Society

Dark Skies

Natural lightscapes are the natural resources and values that exist in the absence of human-caused light. Unfortunately, light often escapes upward and scatters through the atmosphere, brightening yet diminishing the view of the night sky. Light pollution is problematic for wildlife, for energy efficiency, for human safety, and for human health. In the national parks, improper lighting impedes the view and the visitor enjoyment of the natural dark night sky. Light pollution also diminishes appreciation of the cultural significance of the night sky, a natural resource common to all cultures that is present in countless myths, religions, and works of art.

Life has evolved over billions of years with reference to a relatively stable night-day schedule, until now. Animals and plants live by a circadian rhythm attuned to the planet’s 24-hour cycle. This rhythm is disturbed by artificial light. Nocturnal animals in the presence of night light experience difficulty foraging for food, exposure to new predators, and increased mortality due to impaired night vision. Birds and insects may become fixated on and drawn to a light source, continually flying into the beam until exhausted, until they fall, or until they become prey. Artificial lights also cause migrating birds to wander off course, wasting energy and sometimes never reaching their natural destination. Reptiles like sea turtles need dark places to breed. Hatchling sea turtles are instinctively drawn towards light, which usually indicates the reflection of the moon or phosphorescence in the ocean. Artificial lights disorient sea turtle hatchlings, drawing them away from the ocean until they are fatally exhausted or dehydrated. Humans too may feel the effects of artificial light. A disturbed circadian rhythm may cause, among other problems, depression and insomnia.

Winter Solstice celebration of dark night skies at Muir Woods

Winter Solstice celebration of dark night skies at Muir Woods

Despite the common belief that well-lit areas are safer for humans, this is not always the case. When light is scattered into the sky without direction by improper fixtures, it wastes energy, creates glare, intrudes into the domain of others (known as “light trespass”), and may actually reduce nighttime visibility. Proper light fixtures meet the basic security, visibility and comfort needs of humans with minimal harmful impact. Good fixtures, like “shielded” or “full cut-off” fixtures, direct all light where it is needed without scattering it wastefully into the night. Such lighting fixtures often cost more upfront yet pay for themselves within a few years because they are more energy efficient than light-wasting fixtures.

The National Park Service has developed a system for measuring sky brightness in order to quantify the source and severity of light pollution. In 1999 a group of National Park Service scientists formed the Night Sky Team to document the status of our night skies and protect them for future generations. Using specially calibrated research cameras to quantify sky brightness, the Night Sky Team has documented light affecting parks from over 200 miles away. Almost every national park surveyed has noticeable light pollution.

Nighttime walks, nocturnal wildlife viewing and stargazing events are also organized in national parks to encourage appreciation of the dark sky and to raise awareness about light pollution issues.

Solutions you can try:
1) shield outdoor lighting
2) only use light when you need it
3) use timers and dimmers
4) shut off lights when you can
5) use only enough light to get the job done
6) use long wavelength light with a red or yellow tint to minimize impact
7) work with neighbors and your local government to keep the skies dark

For more information, check out:
The NPS Night Sky Team
Golden Gate National Recreation Area – Lightscape / Night Sky
The International Dark-Sky Association


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