Understanding the Sounds of Ecosystems
Bryan Pijanowski (center) collects data from a forest. (Purdue Agricultural Communication photo/Tom Campbell)
An emerging new scientific field called soundscape ecology suggests that sound can tell us a lot about the health of ecosystems. Bryan Pijanowski is a Purdue University professor and founder of the new discipline. He tells host Bruce Gellerman about a few of the tens of thousands of the recordings he has compiled.
CURWOOD: Okay class, listen carefully. There's a gold star in it for anyone who can identify this sound.
CURWOOD: The answer: that’s the sounds of an ant colony. The squeaking is called stridulation. It's the sound ants make when they greet each other. And it's just one of the tens of thousands of recordings in a unique archive at Purdue University.
GELLERMAN: Bryan Pijanowski oversees the collection. It's part of a new discipline he calls "soundscape ecology." Professor Pijanowski wrote about it in the current issue of the journal Bioscience.
PIJANOWSKI: Well it’s the study of all the sounds in a landscape - everything that is biological, geophysical, and from those from the humans. We’re trying to understand how sounds in the environment can be used to assess ecosystem health. What we’re doing is we’re actually sticking a microphone out in the middle of the woods and recording it continuously. Every day, every week, for a long period of time - matter of fact, we’ve been doing it now for about four years.
GELLERMAN: And you listen to all the sound?
PIJANOWSKI: Well, no. Our computers do. And some of my students. Yeah, I mean we run them through supercomputers and analyze the patterns in data and try to look at different kinds of what we call orchestrations.
We’re very interested in the dawn chorus and the dusk chorus and how these change over time and how they’re modified when we kind of look at different ecosystems that are potentially impacted by humans. I mean we’re all kind of familiar with it: when we wake up in the morning, we hear birds singing, or frogs, or crickets - and so it’s very characteristic of every natural ecosystem in the world.
PIJANOWSKI: This was in the middle of the Sequoia national forest.
GELLERMAN: And what’s that sound, do you know?
PIJANOWSKI: Well we’ve got some birds; I think we have a few insects in the background.
GELLERMAN: Now let’s hear the same time of day, on the other side of the planet.
GELLERMAN: So this is a dawn chorus in Africa.
PIJANOWSKI: That’s correct.
GELLERMAN: Where are we?
PIJANOWSKI: Zimbabwe! And here we’re listening to birds, insects, and an occasional monkey in the background.
GELLERMAN: Now, as a soundscape ecologist, what do these two pieces of sound say to you? What can we learn from them?
PIJANOWSKI: I think these are both very healthy ecosystems. They are very complex - there are a lot of different sounds occurring in this landscape.
GELLERMAN: So sound becomes an indicator of the health of an environment.
PIJANOWSKI: You can even go further than that. You can say that if a particular sound is missing from a landscape, it might be a signal that something is happening to it - that it might be threatened, that something is missing. In some cases, you can consider these as kind of like a fossil of some sort - it’s like an acoustic fossil.
My colleague Bernie Krause, who’s a co-author on the paper, has been recording all around the world. And in many cases, those ecosystems no longer exist - they have been developed, they’ve been converted to farmlands, and so that’s the only record that we have of those landscapes.
GELLERMAN: I’m reminded of Rachel Carson’s book “Silent Spring”…
GELLERMAN: …and the way she knew that it wasn’t healthy - that something was happening - was that the birds were silent.
PIJANOWSKI: Yeah, I mean that’s another point we’re making in the article in Bioscience: that we could be threatening our natural soundscapes to a point where we could be silencing them. I mean I think Rachel Carson’s call to action is really what we’re trying to reflect upon again.
GELLERMAN: Well let’s hear a sample from one of the sounds that you recorded, we have it here…
[LOUD ANIMAL SOUNDS]
PIJANOWSKI: That’s from the Congo. Those are forest elephants - this is about three o’clock in the morning. These particular recordings reflect a very unique kind of soundscape. There are very few places in the world where an elephant would go to this kind of wetland - it’s called a bai: it has a high salt concentration; these elephants need it for their diet.
The landscape around it is very unique. It’s a one-of-a-kind, and it’s one that we need to identify, protect, and preserve, because once it’s gone, there’s nothing to replace it. It’s irreplaceable.
GELLERMAN: So I want to play you something that’s kind of a haunting sound - listen to this, this sounds like something out of a Dracula movie.
PIJANOWSKI: So what we have here are wolves. We’re in the middle of the Algonquin National Park in Canada. And this is a marvelous recording that I think illustrates that acoustics give us a sense of place. We…as we listen to this, we probably have a visual image of this landscape, of this forest, and we can almost put ourselves there.
GELLERMAN: What’s interesting is that you can hear the birds chirping away in the midst of all this haunting wolf howls.
PIJANOWSKI: And they continue. They don’t stop. So as you kind of listen to many of these recordings - and they’re all online - the same kinds of patterns exist. I mean we have lots of amphibians and frogs chorusing the background, and birds that are vocalizing and singing - again, those are very characteristic of natural landscapes.
GELLERMAN: So are you going to be accepting submissions of sounds from lay-people?
PIJANOWSKI: Yes we are! Anyone who wants to submit their recordings can do so. We plan to have a website this summer where people can actually do that and would automatically be placed into an archive.
GELLERMAN: Well I have a submission for you, Professor, I want you to hear this one.
PIJANOWSKI: Oh excellent!
[SOUNDS OF BIRDS CHIRPING IN A FOREST]
PIJANOWSKI: Wow. I love it! I could listen to it for a long time.
[AMAZON RAINFOREST SOUNDS NEAR THE RIVER OF THE DEAD]
GELLERMAN: Well, Professor, thank you so very much, I really enjoyed it.
PIJANOWSKI: This has been great, thanks.
GELLERMAN: Bryan Pijanowski is a professor of forestry and natural resources at Purdue University. For a link to his article in the journal Bioscience and to hear more recordings from the soundscape ecology archive, visit our website loe.org.
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