Sound system ecology is a growing scientific discipline. It involves recording and studying the acoustic landscapes of the planet to assess how they are affected by human confusion and the climate crisis. The results are uplifting.
Our planet has a soundtrack. Naturally the birds interpret it, competing with trills, chirps, whistles and cracks in the dawn chorus, but mammals also play in the orchestra of the earth. Lions roar. The moose brays.
Insects are known to be talkative: any cicada will tell you that. The fish gurgle. Underwater symphonies arise from the coral reefs in which shrimp mark the rhythm.
Plants also emit sound waves. Young peas listen attentively to the flowing water. Even mushrooms talk: according to scientists, the mycorrhizal network, which connects the roots of trees in a forest, is as chatty as a school playground during recess.
The wind whistles. The water goes plop plop. Thunder rumbles. Glaciers creak and the earth’s crust cracks.
Rachel Carson, the pioneer
Together, these sounds tell a story that scientists are just beginning to decipher. “Sound is a truly wonderful thing that surrounds us and that we have simply ignored, not only as a global society, but also as a scientific community,” says Bryan Pijanowski, director of the Center for Global Soundscapes at Purdue University, Indiana [aux États-Unis]. In 2011 he created with some colleagues a new discipline: the ecology of the soundscape.
The idea that sounds are clues to the health of our world began to be explored some sixty years ago, when American biologist Rachel Carson published her shocking book on birds decimated by pesticides, silent spring [dont une édition augmentée vient d’être publiée en français, aux éditions Wildproject].
In the following decades, new generations of scientists have increasingly realized the importance of the planetary sound ecosystem for animals that communicate through sound. “We are such a visual species that we have disqualified sound as a means of assessing and measuring the changes taking place on our planet”, observes Bryan Pijanowski.
An increasingly less vibrant score
The truth is that the earth sings a strange and haunting tune. The biophony of the planet – all the sounds emitted by living organisms – is less and less vibrant. Humans are cutting down forests, turning the land upside down, drying up the seas, killing wild animals and introducing invasive species.
The bioacoustic and musician [américain] Bernie Krause has assembled the world’s first collection of nature sounds. In the late 1960s he began recording all the sounds that inhabited the rainforests of Asia, Latin America and Africa, deviating in particular from the usual practice of chasing voices. He wanted to know what animals in the world around them heard, whether each part of the planet had a specific soundscape in a particular tonality, and what was happening at night.
The result was 4,500 hours of audio tapes. “Listening with ears wide open aroused in me an extraordinary feeling of humility and offered me a sacred gift: the memory of a living sound in a certain place and at a certain moment”, he writes in his book The great orchestra of animals [éd. Flammarion, coll. “Champs”, 2018].
The orchestra of the earth is out of tune
Today, nearly half of these soundscapes exist in his library alone. They are acoustic fossils. And those that remain are very impoverished and in competition with all the sounds produced by man: anthropophony. It’s not just our growing voices that make noise, it’s also what we do. Our factories, our cars, our boats, our jets, our bombs, our bulldozers and our air conditioners.
Even more sinister, we are changing one of the main means of propagation of sound. CO concentration2 in the atmosphere makes the air hotter and wetter, or hotter and drier, which jars the planet’s instruments. The ocean also becomes warmer and less salty, which increases the speed of sound waves.
The earth speaks. Are we listening to it? “For nothing”, Pijanowski said.
For whales and other marine animals, sound is far more important than sight. Sound waves travel through water nearly five times faster than through air, making it an ideal medium for sonar communication. Also, some of the life of marine animals takes place in water that is too deep for light to reach them, which reduces the ability to use vision. And in the Arctic and southern oceans, marine mammals live without sunlight for half the year, making them completely dependent on what they hear.
“They evolve in a world of sound. Every noise gives them information, points out Valeria Vergara, co-director of the Cetacean Research Program at the Raincoast Conservation Foundation, British Columbia [au Canada]. It tells them where they are in relation to other members of their group, how far away their pup is, which direction to go, or where is a hole or channel in the ice where they can hunt.
There’s still a lot to learn about how animals use sound. We know, for example, that frogs and toads use their voices