Ecoacoustics: how soil sounds measure biodiversity

Australian research has highlighted the correlation between the complexity of noise produced by invertebrate communities and the level of soil biodiversity

by Matteo Cavallito

 

Soil sounds are the very measure of land health and biodiversity. This is the concept behind ecoacoustics, a new discipline that is attracting the interest of scientists studying aquatic and terrestrial ecosystems. Among them are researchers from Flinders University in Adelaide, South Australia, who recently released details of their latest study on this matter.

The findings, according to a research published in the Journal of Applied Ecology, a publication of the British Ecological Society, “provide new support that ecoacoustics can help monitor soil biodiversity in different forest restoration contexts, including in UK temperate and Australian grassy woodlands.” This technique, in particular, “holds promise in addressing the global need for effective soil biodiversity monitoring methods and protecting our planet’s most diverse ecosystems.”

A new discipline applied to the soil

Ecoacoustics, the authors explained, is the study of sounds produced by animal communities, plants and their environment. Over the years, scientists have experimented with using recorders in trees to capture the sounds produced by different species above ground. In this way, they managed to obtain relevant information on biodiversity and the dynamics of ecosystems. The same principles and tools are now being applied to the soil.

“Researchers are beginning to explore the sounds of soil, using recorders and specialised microphones attached to probes in the ground,” the Flinders researchers noted in an article published by the Australian website The Conversation. ‘These devices record the acoustic vibrations produced by soil-dwelling organisms as they move through the underground world’. The data collected are particularly important.

More complex sounds in regenerated areas

The study, which follows similar research carried out in 2022 in the UK, was conducted in the Mount Bold Nature Reserve in southern Australia and involved the team of Flinders University researchers led by Professor of Restoration Ecology, Ecosystem Health and Genomics, Martin Breed, and his colleague at the Chinese Academy of Sciences, Xin Sun. Here, the authors employed various tools including an underground sampling device and a sound attenuation chamber.

This made it possible to record the sounds produced by soil invertebrate communities whose presence was also quantified by manual counting.

The recordings were made in some deforested areas and in other areas that had been regenerated. In the latter, greater complexity and acoustic diversity were noted. These two features were found to be “significantly associated with soil invertebrate abundance and richness.”

A silent soil cannot be healthy

According to the authors, the research shows how soil sounds can be a measure of the presence and vitality of invertebrates, which are known to be essential for maintaining the balance of the soil ecosystem.

“We found a greater diversity of crackles, clicks and pops in the restored soils,” the scientists explained. “We linked this to a higher number of invertebrates moving around. If the soil sounds quiet, it’s a sign it’s not healthy.”

Finally, the authors highlight the importance of ecoacoustics for the restoration efforts of global soils, which are still subject to general degradation. ‘This new field of research aims to investigate the vast, teeming hidden ecosystems where almost 60% of the Earth’s species live,’ explained Flinders University researcher Jake Robinson in a statement. “With 75% of the world’s soils degraded, the future of the teeming community of living species that live underground face a dire future without restoration.”