It’s easy to see the effects of litter and other physical pollution in our nation’s wild places but how do you gauge pollution when it involves light and sound?

Chances are you haven’t heard of the Natural Sounds and Night Skies division of the National Park Service but they are the people who are figuring it out. Their mission is to protect, maintain, and restore acoustical and dark night sky environments throughout the National Park System.


From the Natural Sounds page: America’s national parks contain many cherished treasures. Among them are captivating natural sounds and awe-inspiring night skies. The joy of listening to the quiet symphony of nature and the wonderment of seeing the Milky Way stretching overhead are unique experiences that can still be found in many of our national parks.

Natural sounds and natural lightscapes are essential in keeping our national treasures whole. They are magnificent in their own right and inspirational to the visitors who come to national parks. They are vital to the protection of wilderness character, fundamental to the historical and cultural context, and critical for park wildlife.

As part of their work they have sampled the sounds heard at nearly 600 different locations at Parks across the country and used the resulting data to create maps of estimated noise levels for the contiguous US.

Map of Existing Conditions:
This map shows the estimated median sound levels for areas of the 48 contiguous states of the U.S. The range goes from deep blue (low decibels) to light yellow (high decibels). 
Map of Natural Conditions:
This map shows the naturally occurring noise levels across the country. The range goes from dark brown (lower decibels) to dark blue (higher decibels). Note that the color coding is different than in the first map because naturally occurring sounds are much quieter. Higher sound levels can be seen in wetter areas with more vegetation due to wind blowing through vegetation, flowing water, and more animals (especially birds and frogs) vocalizing.

Find out more about noise pollution, sound science, and how to reduce sound pollution at the NPS Natural Sounds division.

From the Night Sky page: Starry night skies and natural darkness are important components of the special places the National Park Service protects. National parks hold some of the last remaining harbors of darkness and provide an excellent opportunity for the public to experience this endangered resource. 

The NPS uses the term “natural lightscape” to describe resources and values that exist in the absence of human-caused light at night. Natural lightscapes are critical for nighttime scenery, such as viewing a starry sky, but are also critical for maintaining nocturnal habitat. Many wildlife species rely on natural patterns of light and dark for navigation, to cue behaviors, or hide from predators. Lightscapes can be cultural as well, and may be integral to the historical fabric of a place. Human-caused light may be obtrusive in the same manner that noise can disrupt a contemplative or peaceful scene. 

Find out more about light pollution, the science of light, and how to reduce light pollution at the NPS Night Skies division.