Source: Grist | by Ayurella Horn-Muller | August 29, 2024
Ground-breaking “ecoacoustics” use underground critter concerts to monitor a hidden ecosystem.
Think back to the last concert you went to. Now replace the music that rang through the venue with an erratic series of pops, muffled staccatos, distorted taps, and sudden clicks. No single sound is quite distinguishable from another, all blending together in a medley of unsynchronized noise.
Except, instead of musicians, what you’re hearing is a mass of underground invertebrates. And they’re putting on an unorthodox show for the handful of humans who know where, and how, to tune in—a complex symphony of vibrations and pulses that relay the state of the very soils these organisms are moving within.
“You can actually use sound to listen to the soil, and get an indication of soil health, based on the little critters moving around,” says Jake Robinson, a microbial ecologist at Flinders University in Australia. He’s the lead author of a study just published in the Journal of Applied Ecology that found that ecoacoustics, or the study of environmental sounds, can not only be used to detect organisms in the soil, but also mined to identify the difference between restored and degraded land.
Earthworms are just one of many organisms that can impact soil health.
Although the practice of recording the sounds of nature has existed for over a century, using those recordings to analyze ecosystem health is a newer discipline. Scientists have, in recent years, started experimenting with using ecoacoustic tools to capture the full range of sounds in healthy ecosystems—such as in coral reefs, caves, and oyster beds—and applying those recordings to restoration efforts in damaged and degraded areas.
And yet, soils, and the many hidden species and organisms that subsist underground, haven’t been considered for such techniques. Until now.
“People in the past have thought ecoacoustics probably can’t be used for that, because there’s no vocalization or echolocation. We’ve shown that it actually can be used,” says Robinson. The trick, he notes, is deploying sensitive-enough microphones that allow you to detect the most minuscule of movements. “Things like millipedes, the little tappy legs, you can compare that to a worm, [which has] more of a slidey action. So actually, you can tell slight differences between the acoustic profiles of these little critters.”
From millipedes to nematodes, soils across the world teem with billions of living organisms that make up Earth’s biosphere and contribute to the global food supply. All told, the ground beneath our feet houses the most biodiverse habitat on the planet. “The more invertebrates that are in the soil, the more active that they are, the more different sounds and vibrations they are emitting,” says Robinson.
“Things like millipedes, the little tappy legs, you can compare that to a worm.”
His team used a belowground sampling device and sound chamber to record and collect 240 soil acoustic samples from deforested plots, locations undergoing restoration, and those with at least some of their original vegetation in a corridor of grassy woodlands in Mount Bold, South Australia. After listening to the acoustic recordings first onsite, and then removing soil samples to analyze them in controlled conditions in the field, they discovered a pattern: The acoustic complexity and diversity of the soundscapes were significantly lower in the deforested plots.
Originally published on Grist, click to read more here.