Listening to the soil as a way of assessing biodiversity?

Listening to the soil: in recording the soil’s soundscape, researchers can estimate the biodiversity it holds.
Credit: Space for Life (Francis Cardinal)
Écouter le sol : en captant le paysage sonore du sol, les chercheurs peuvent estimer la biodiversité qui s’y trouve.
  • Écouter le sol : en captant le paysage sonore du sol, les chercheurs peuvent estimer la biodiversité qui s’y trouve.
  • Une pelouse traditionnelle : cette pelouse s’apparente à une monoculture et ne supporte pas beaucoup d’organismes vivants.
  • Un terrain minéralisé : sur un terrain minéralisé, il est peu probable que la vie dans le sol puisse jouer un rôle sur le cycle des nutriments.
  • Sol d’une forêt : en nature, le sol est rarement nu et les débris végétaux sont recyclés par la faune du sol.
  • Les organismes vivants du sol sous la loupe : un sol sain abrite une faune et une flore très variée.
Listening to the soil as a way of assessing biodiversity?

Sounds in the soil, an indicator of biodiversity

It might seem far-fetched, but it’s nevertheless what a recent study by a Swiss team wanted to shed light on by recording sounds coming from the ground under their feet. If certain noticeable noises like tummy rumbling, the throbbing engine of an old car or neighbors having a party are synonymous with the word nuisance, a noisy soil, on the contrary, might be a sign of health! As it happens, many organisms that live underground emit sounds.

Earthworms, mites, pillbugs, springtails, various larvae, spiders, centipedes, beetles and many others are part of the soundtrack; the more varied the recorded sounds are, the more diversified the wildlife in the soil will be.

In capturing this soundscape, researchers reckon that they’re able to associate it with the fauna producing it, and that way assess the biodiversity found there.

A promising (and inexpensive) technique for assessing soil biodiversity

Armed with recording devices and microphones, the Sounding Soil project team is trying to determine the sound signature of soils. This low-cost process is innovative, because it aims to establish the biodiversity of the soil by way of recorded sounds – in contrast to the traditional technique consisting of laboratory analysis through meticulous dissection of carrots gathered from the soil. The recording of sounds is an accessible method that makes it possible to involve the public in community-science projects and even be associated with artistic works.

Why is the soil noisy?

The creatures that live in the soil produce sounds for various reasons. Whether they’re moving around, feeding, or communicating with one another, the recordings bear witness to their life. The more varied the sounds are, the more likely the conclusion that considerable biodiversity can be found there. A surprising fact: it was in a compost heap that the soundscape proved to be most abundant. Many living beings in the soil break down organic matter and are an essential part of the nutrient cycle.

So what does silent soil mean?

A mute soil can very well be synonymous with absence of life. In 1962, the American biologist Rachel Carson published the book Silent Spring, which called attention to the impact of pesticides on bird populations. We learned that the loss of avian fauna could give rise to springtime made silent by lack of birdsong.

Strangely, in their studies the Sounding Soil team got recordings that were undiversified, even uncommunicative, during their analyses in conventional agricultural land, where synthetic fertilizers and pesticides are used. Coincidence?

Although highly promising, this technology is still in its early stages. Sound pollution in soil from human activity is still misunderstood, and may blur the results. A lot of work remains to be done for us to be able precisely match sounds to particular organisms. In school I was taught that the soil was part of the non-living, but our knowledge evolves, and certain practices change. For your gardening season, keep in mind that soil can be protected with mulch, and that it can be nourished with soil amendments. Life in the soil is something to be considered, to be nourished and to be protected.

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