Monitoring Ecosystem Health by Listening to Earthworm Movements

While they may not be as captivating as a dawn bird chorus, the sounds of ants, beetle larvae and earthworms recorded underground provide a snapshot of whether an ecosystem is healthy.

“The idea is that we can monitor soil health using the sounds made by invertebrates.” Jake Robinson At Flinders University, Adelaide, Australia.

He and his colleagues Mount Bald Conservation AreaThe project will involve 240 recordings over five days in spring 2023, with each recording lasting nine minutes, covering a 55 square kilometre area around a reservoir south of Adelaide.

Two sites had been cleared of trees approximately 15 years ago and maintained as grassland, two sites had been cleared but had regrowth of trees and bushes over the course of approximately 15 years, and the remaining two were intact grassland forests.

Robinson and his colleagues dug up soil samples at each site, placed them in containers, and placed them in sound-attenuating chambers — devices that allow them to record sounds from the soil in a controlled environment while filtering out other sounds. The researchers then examined the soil samples and counted the types and numbers of invertebrates present in each sample.

The researchers found that intact and revegetated plots contained more soil invertebrate species, including organisms such as beetle larvae, earthworms, centipedes, woodlice and ants, and generally more specimens, than did the clear-cut plots.

To analyze the noise, Robinson and his colleagues used a sound complexity index, which works on the premise that many biological behaviors, such as millipede movements, produce distinctive sound patterns.

More diverse sound activity corresponds to a higher index score and more species of organisms present. Soils in revegetated sites had an index score 21 percent higher than soils in deforested sites.