An all-natural animal orchestra
A landscape may look healthy, but how does it sound, and what does that say about how its wildlife is doing?
It's a question Bernie Krause has spent much of his life trying to answer. To do so, he's recorded the sounds of thousands of places in far-flung corners of the world.
He coined the word "biophony" to describe these recordings. These soundscapes have helped him show what happens to animals in stressful environments, and explain where our language comes from.
It wasn't what he originally planned to do.
Bernie Krause started as a classic musician. He joined the US folk group The Weavers in 1963, but became famous for introducing some of the biggest bands in the world to the synthesiser in the mid-1960s.
George Harrison, Simon & Garfunkel and The Doors all learned from Krause and his partner Paul Beaver.
Beaver and Krause composed and played the Moog synthesiser with the Monkees and provided soundtracks for big Hollywood blockbusters. They're credited with introducing the synthesiser to pop music and film.
But it was a chance encounter while recording an album that put Krause's life on to a different track.
"We were doing an album for Warner Brothers called 'In a Wild Sanctuary' which was the first album ever to use ecology as its theme, and the first ever to use natural soundscapes as a component of orchestration," he said.
"I just went out into the field and the first time I switched on the recorder it changed my life, because the stereo space opened up in a way I had never heard before.
"Being outside and hearing the wind in the trees and birds flying overhead and the way space opened up was just magical to me so I decided that's what I wanted to chase for the rest of my life."
He now has an archive of more than 4,500 separate soundscapes collected from all over the world since 1968. More than half of the soundscapes he recorded have since disappeared from nature.
The Arctic in Alaska and the Northwest Territories of Canada are the most pristine sounds he has collected, as there are so few people around.
He has examples from Borneo, Zimbabwe and the Amazon, which were crowded with sound when he recorded them.
But political change, climate change and the impact of humans on the landscape have all contributed to their loss.
In his book The Great Animal Orchestra, Krause uses the evidence of 'biophony' degradation to demonstrate how even healthy-looking ecosystems can sound damaged.
Krause argues that in a pristine place, animals, insects, birds and reptiles have each found a niche - their own frequency in which they can communicate to each other and be heard above everything else.
"It's taken quite a while for all those critters to figure out where their voices should be," he says.
By creating a spectrogram - a graph of the soundscape created by plotting time against frequency - he's able to see the patterns that natural sound forms.
"When it looks very structured and you can see the discrimination between those voices, you know it's healthy habitat."
A spectrogram can also instantly show if certain frequencies are missing.
In 1988 Krause recorded a soundscape in part of northern California before a new style of logging began. When he returned a year later, the scene looked healthy, but many of the ecosystem's sounds had gone.
Krause also links the languages humans developed to the sounds of the wild.
"Animals taught us to dance and sing because we were mimics - we were always mimics," he says. "When we heard the biophony, the sound of living organisms in a given habitat, we imitated those sounds and their structure.
"We used the sounds of the forest, or the desert, or wherever it was we happened to live as a natural karaoke orchestra with which we performed. In other words we used it as a backup band."
His collection mostly includes the sounds of whole landscapes, not individuals, on land and beneath the sea. To record sea and river sounds, he uses an underwater microphone called a hydrophone.
He recorded a shrimp, which makes the loudest sound on the planet for its size, and a sea anemone which isn't as quiet as it looks.
For Krause, listening to the environment provides a much-needed perspective.
"We're not listeners, we are lookers," he says. "We understand our world through what we see in Western culture, we are not guided much by what we hear."
That's too bad. As Krause's work shows, there is so much to hear, if we'd only just listen.