SCOTT SIMON, Host:
Biologists who studying ecosystems typically look at the landscape as a whole to understand how each plant and animal fits in, but they don't generally listen to the landscape. Now, a group of scientists is calling for the creation of a new field of study to do just that.
NPR's Richard Harris reports they call this new field soundscape ecology.
RICHARD HARRIS: There's nothing new about studying animal sounds, biologists have been doing that for centuries.
(SOUNDBITE OF BIRDS CHIRPING)
HARRIS: After all if you want to understand birds, like these in Madagascar, you need to understand how they communicate - with sound. But Bryan Pijanowski is now asking his colleagues to take a huge step back and, metaphorically speaking, listen not just to the trees but to the forest.
BRYAN PIJANOWSKI: We're trying to understand how sounds can be used as measures of ecosystem health.
HARRIS: He and some colleagues have written a call to action in the journal, BioScience. It's time, they say, to formalize the study of soundscape ecology.
PIJANOWSKI: So, we're interested in kind of like all the voices of the landscape; not just particular individual species, but really the orchestration of those different sounds by biological organisms.
HARRIS: Pijanowski has a few examples to make his point. Listen to this.
(SOUNDBITE OF ELEPHANTS)
PIJANOWSKI: So we're listening to forest elephants at about three o'clock in the morning in the middle of the Congo. But we're also hearing some other sounds; the crickets and occasional bird, and maybe some other things that are in the background here.
HARRIS: This recording shows, among other things, how animals divide up the soundscape. Insects are monopolizing the high-frequencies and elephants are commanding the low notes. Pijanowski says this sound is just as important to the environment there as the trees and the ponds.
HARRIS: Okay, here's another example from his study.
(SOUNDBITE OF ANTS)
PIJANOWSKI: So what we're listening to here is stridulation patterns from ants.
HARRIS: Stridulation is a fancy way of saying that ants are rubbing their body parts together to make sounds that they use to communicate. If you've never heard this sound, it's probably because you've never been buried inside an ant mound.
PIJANOWSKI: One of the main points that we're trying to make here is that a soundscape can be something that we humans just don't hear. It can be at a fairly small scale.
HARRIS: One goal of this research is to understand those soundscape - how animals interact with each other and even across species. For example, some silent newts follow frog sounds to find the best breeding ponds.
But one of the biggest questions confronting the field is figuring out how human beings affect the soundscape. Pijanowski made this recording near Purdue University.
(SOUNDBITE OF TRAFFIC)
HARRIS: The high-pitched sound is from a soaring insect-eater called a nighthawk.
PIJANOWSKI: It's flying overhead and we hear these a lot in kind of small towns in the Midwest. And so they kind of help give us a sense of place. But we also have a church bell in the background, and that is something that we all kind of like. It's a cultural soundscape. But there are other sounds there that we don't find all that attractive and pleasing.
HARRIS: Like traffic. Those sounds may not be disturbing the nighthawk, but some other bird species do poorly when nesting near the thrum of tires.
And Jesse Barber at Boise State says scientists have just begun to explore how noise affects animals.
JESSE BARBER: Probably the most telling work has come from a series of groups that have worked in oil and gas fields.
HARRIS: They compared bird life around noisy equipment that compresses natural gas with similar but quiet habitat. In Alberta, Barber says, they found that birds had fewer offspring at the noisy sites. Similar results came from the Southwestern United States.
BARBER: The group working in New Mexico found that there's significantly reduced species richness comparing these two sites.
HARRIS: Lab experiments in Germany found that noise interferes with bats that hunt for insects on the ground, by listening for the sounds they make when scurrying around.
Barber says people just don't think much about how noise is affecting wildlife.
BARBER: For instance, most land management agencies don't consider noise when they're making decisions about how to manage public resources. And even biologists, on the more basic level, haven't thought about how it's all integrated.
HARRIS: Barber has been part of a project to understand how noise is affecting national parks. He says there's been a huge change in the past few decades, as both vehicle traffic and airplane traffic have just about tripled in the U.S.
BARBER: For instance, if you record in the back country of Yosemite, you'll find that 70 percent of the time, a high-flying jet can be heard on the recording.
HARRIS: He suspects that low rumble is probably not bothering most animals. But still...
BARBER: Even if it's not affecting wildlife, I would say that 70 percent of the time occupied by high-flying jets is definitely an influence to human enjoyment of that landscape.
HARRIS: So Barber agrees it's time to study the ecology of sound and find out how it affects people and wildlife alike.
Richard Harris, NPR News.
SIMON: You can hear more sounds of the landscape on our website, npr.org/science.
(SOUNDBITE OF MUSIC)
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