The Natural Sounds and Night Skies Division of the National Park Service studies, and tries to minimize, human impacts on two historically under-appreciated natural resources — quiet, and darkness.
The Sturgis Motorcycle Rally may be one of the loudest, sustained aural assaults on the quietude of a vast swath of public lands teeming with wildlife, though it doesn't necessarily have to be.
SDPB spoke with Dr. Frank Turina, Program Manager for Policy Planning and Compliance at the Natural Sounds and Night Skies Division about the program, affects of noise on animal behavior, the sounds of Sturgis, and NPS outreach to the motorcycling community.
Can you tell us a little but about the evolution of the NPS Natural Sounds and Night Skies program?
Within the Park Service, the issue of noise and what we call protecting the acoustic environment really come to life in the 1970s, particularly in the area around Grand Canyon. In 1975, the Grand Canyon Enlargement Act was passed and it was the first piece of legislation that identified natural quiet as being a resource that the Park Service needed to protect.
The impetus for that component of the legislation was that there were a lot of overflights of the Grand Canyon — a lot of sightseeing tours — and the Park Service recognized that was having some impact on visitors to the park, and potentially wildlife and cultural resources.
As the years went on, our understanding of the effects of noise has grown and there’s been some additional pieces of legislation, again primarily dealing with overflights, in a lot of cases sightseeing aircraft. There was a study done in the 1990s that looked at that issue. It was presented to Congress. The results of that study led to a couple pieces of legislation, the dominant of which was the National Parks Air Tour Management Act in 2000. That required the Park Service to work with the Federal Aviation Administration to mitigate and prevent any impacts on park resources from noise emitted by aircraft.
Around 2000, our [Natural Sounds] program was officially recognized.
As our understanding has continued to develop, we’ve realized that there are lots of noise sources that are effecting park resources and that we need to help parks address those issues and take actions to mitigate and reduce noise from a variety of sources.
Is sound pollution a bigger issue for human visitors or wildlife?
All of the above. There’s a lot of literature out there in the scientific world that shows that wildlife are affected by noise. Going back decades, there’s research showing that road noise in particular affects wildlife — or to put it differently, that roads affect wildlife. There are a lot of aspects of roads that affect wildlife. Teasing out the noise component and whether it’s the noise as opposed to the existence of the road was a little bit of a challenge. In recent years, we’ve done some studies that show indeed a lot of the impacts we see from roads are coming from the noise component.
We know that noise from roads and other sources have adverse effects on many different wildlife species. So that’s obviously an important concern for the Park Service to minimize those impacts.
On the visitor side, we’ve done numerous surveys over the last ten to twenty years, and consistently our visitors tell us that they visit national parks to hear the sounds of nature. Natural sounds are right up there with the visual scenery.
And we know that noise has an adverse effect on people’s experience of a park. There have been interesting studies that show that visitors’ assessment of visual quality is effected by noise. If you’re looking at a vista of the Grand Canyon, and you hear the sounds of birds and crickets and natural sounds, you’ll rate the scenery at a higher quality than if you’re exposed to noise.
There are also effects on cultural or historic elements of parks. So when you got to places like Gettysburg, those areas have this sense of reverence. Even with no signs, visitors will often speak in a whisper. So that acoustic component is an important part of the cultural and historic heritage that the parks are trying to protect.
What kind of impacts do you think a big human-caused noise event like the Sturgis Motorcycle Rally has on wildlife in the Black Hills?
There are a couple of interesting aspects. As a little bit of context, the Park Service studies many different noise sources. We’ve looked at sources such as boats, off-road vehicles, personal watercraft, oil and gas activity, and aircraft overflights. We look really closely at our park administrative activities for the types of noises that we create ourselves. We have an interest in understanding and protecting park resources from a multitude of different noise sources, and motorcycles are just one of those.
We have done some studies on the effects of motorcycles on parks. We spent a fair amount of time at Devil’s Tower — that’s probably where we have the most data about motorcycles.
There are some things about motorcycles that make them somewhat unique in terms of their noise and how that affects parks. The character of the noise depends on things like the style of the motorcycle, the size, type of exhaust system and other factors. Not all motorcycles are loud. Some that we’ve measured are as quiet or quieter than cars. Others are much louder.
One thing is that many styles of motorcycle will generate more low frequency noise than most other vehicles. And while most high frequency sounds are scattered by the environment typically within a pretty short distance from the road, the low frequencies can travel for much greater distances. The other thing is that parks typically have very low background noise conditions. Parks are typically very quiet. So, the data that we collected from some of the parks show that low frequency noises generated by motorcycles can often be heard more than ten miles into the backcountry.
Has the NPS Natural Sounds done any work to try to minimize the noise impacts of the Rally?
Yes. We did some measurements of road noise at Devil’s Tower during the Sturgis Rally in 2014 and 2015.
Devil’s Tower and the surrounding areas — basically all of the Black Hills — are sacred to many Native American tribes, so the effects of the noise from the rally are important to the park. They asked us to come out and measure some of the sound levels before and after Sturgis. So, we were looking at the motorcycle noise and how we wanted to address the issue and minimize some of the effects on park resources.
We came up with an education and outreach program that we’ve been implementing in parks across the country, to reach out to the motorcycle riding community and educate on the effects of noise, what [motorcyclists] can do to minimize noise when they’re riding through parks.
The goal of the program was to reduce the effects of excessive noise; again not all motorcycles are noisy. We’ve gotten a lot of support from the motorcycle riding community themselves. I think a lot of riders understand that excessive noise presents a perception problem for motorcyclists. The American Motorcyclists Association has an official position on noise that says, “few other factors contribute to misunderstanding and prejudice against the motorcycling community than excessively loud motorcycles.”
So we developed a sign [similar to signs that tell you how fast you’re driving] that tells you how loud your vehicle is. Instead of a number like the speed sign, you have a light bar that goes up and down from green to red. If you have a very loud vehicle, then as you drive by it the bar will go up into the red zone. So we’ve taken those to several parks, and it gets people’s attention. Then, we’ll have an outreach center where we have materials that say here’s what you can do to minimize your noise footprint in the park. We’ve provided that message at Devil’s Tower during the Sturgis Rally and I think the reaction that we got from almost every motorcyclist that we talked to was very positive.
What kinds of wildlife behaviors — relevant to the kinds of wildlife we have here in the Black Hills — have been observed in response to noise?
A study in Colorado by a post-doctorate student looked at the effects of traffic on prairie dog colonies. They went to a colony that was not really exposed to much human-caused sound and played back recordings of the traffic on I-25 in Denver, and watched the behavioral changes. And he found three different effects, which are pretty consistent with a lot of studies about highways in general: The prairie dogs spent less time above ground. They spent more time in a vigilant posture, looking around for threats. And as a result, they spent less time foraging. Those are fairly typical types of effects that we see from noise — and other aspects of highways and transportation — on wildlife.
[Another] post-doc from Colorado State University did a long-term study at Devil’s Tower, where [the researcher] put out sound meters near a prairie dog colony during the Sturgis Rally and collected data on the changes in behavior. Those data haven’t been analyzed yet. They’ve just recently been collected so we don’t know anything about the results yet, but it should be an interesting study to keep an eye on.
Are there any common threads you see across studies on different types of wildlife and how they react to noise?
Yes. For example, there was a study of bighorn sheep exposed to helicopter noise in Grand Canyon and they saw similar things to what the researchers found in the prairie dog colony. They spent more time in a vigilant pose, less time foraging. There was evidence that the sheep were fleeing from the sound of the helicopters.
Noise impacts on birds are another area that’s been pretty widely studied. A really innovative study was completed recently by a researcher at Boise State, called the “phantom road” study because they went to an area of a national forest with a high diversity of different species of birds that are usually on a migratory path. So they’ll stop there for a day, eat a lot, and continue on their migratory path.
The researchers strung a bunch of speakers in the trees and intermittently played back the noise of a highway. And then they looked at the differences in how the birds used that habitat. And they found pretty significant decreases in both the number of birds that used that habitat during the time that the road noise was on, and that when birds did use that habitat while it was on, they were losing weight compared to the times when the noise was off.
Those are important impacts when you’re thinking about a bird that has to migrate thousands of miles, and maintaining their caloric intake and energy budget is critical for them to be able to make that migration. So, having noise interfere with that process could have longer-term implications for the health and survival of the population.
How do various animals’ sensitivity to sound compare to our own?
There’s a range of sensitivities to noise in different wildlife species. Some species, like some bats, owls, coyotes and other canid species tend to have very sensitive hearing — more so in the high frequency range. So they can hear those very faint rustling sounds. There’s some great video online of foxes listening for mice under six feet of snow, and diving into the snow and coming up with a mouse.
And there are other species that focus on the low frequency noises. Many rodent species use lower frequency sounds.
The interesting thing is that humans are right in the middle. We have pretty good hearing in the high frequency range, and the low frequency range. So we often use humans as a sort of proxy for protecting the acoustic environment for animals. If we’re doing well in protecting the spectrum that humans hear most, we’re probably doing pretty well for most of the species of animals out there.