There’s a pretty secret soil rave going on just beneath your feet. Healthy soil creates a racket of sound that the human ear can’t really pick up, but that’s definitely there. Ecologists from Flinders University in Australia and the Chinese Academy of Sciences recently listened in on this phenomenon and made special recordings of the clicks and bubbles in the ground.
This chaotic mix of soundscapes could be a way to gauge what kinds of creatures are living in the soil. It seems that the complexity and diversity of the sounds the team recorded are related to the presence of more invertebrates in the soil, including spiders, earthworms, beetles and ants. This, in turn, seems to be a clear indication of the health of the soil. The recordings and findings are detailed in a study published August 16 in the Journal of Applied Ecology.
Acoustic monitoring was conducted on soil in remnant vegetation, as well as on degraded plots and land that was revegetated 15 years ago. CREDIT: Flinders University.
Although soil degradation is a natural process, the United Nations estimates that about 75 percent of the world’s soils are considered degraded. Human activities, including over-farming and intensive agriculture, deforestation, forest fires, and construction, can accelerate this process. All of these activities make soil more vulnerable to erosion by wind and water, which can then damage the complex ecosystems below ground.
It takes hundreds of thousands of years to form a single centimeter of topsoil, so regeneration can take an incredibly long time. The team says the diverse community of species living underground faces a dire and uncertain future without recovery.
[Related: The ingredients for a tastier, stronger tea could be in the soil.]
“Restoring and monitoring soil biodiversity has never been more important,” said Jake Robinson, a microbial ecologist at Flinders University, in a statement. “Although it is still in its early stages, ‘eco-acoustics’ is a promising tool to detect and monitor soil biodiversity and is now being used in Australian bushland and other ecosystems in the UK.”
This new study aims to investigate the hidden ecosystems where nearly 60 percent of the world’s species live by recording the sounds they make. The team compared the results of acoustic monitoring of remnant vegetation—the remaining patches of native trees, shrubs, and grasses in urban areas—with degraded plots and land that was revegetated in 2009.
There is an astonishing diversity of life living in the world’s soil and scientists are beginning to listen in. CREDIT: Flinders University
The passive acoustic monitoring measured soil biodiversity over five days in the Mount Bold region of the Adelaide Hills in South Australia. The team also used a subsurface sound sampling device and a noise attenuation chamber to record soil invertebrate communities, which they counted manually.
[Related: Dying plants are ‘screaming’ at you.]
“Acoustic complexity and diversity are significantly higher in revegetated and residual plots than in cleared plots, both in situ and in sound attenuation chambers,” Robinson explains. “This technology holds great promise in addressing the global need for more effective methods of monitoring soil biodiversity to protect our planet’s most diverse ecosystems.”
