The use of ecoacoustics to monitor soil ecology: a critical review with reference to earthworms

The use of ecoacoustics to monitor soil ecology was identified as a priority in the 2024 horizon scan of global biological conservation issues. Proponents suggest it will have societal impacts by improving soil health assessments, enhance soil biodiversity monitoring and facilitate the conservation, remediation and management of soil ecosystems. Here we review soil ecoacoustics in terms of its definition, theoretical basis, acoustic indices and statistical inferences. To do this we explain mechanical wave behaviour, mechanoreception by fauna, and tactical signal design with reference to earthworms as ecosystem engineers. Ecoacoustics emerged from research on animal long‐distance communication systems, and its direct application to soils has been identified as a problem area. A new field within ecoacoustics has been created for soils, sonoscape investigations, to capture spatio‐temporal complexity of ecological features (rather than soil ecology). There is a good case for reclassifying soil ecoacoustic ‘soundscape’ studies as sonoscapes. We identify that further refinement of ecoacoustics is required for applications to soil habitats. The performance of sonoscape investigations is dependent on acoustic indices and statistical inferences, and we question why stationary signal processing is used as the base transform for soils data, and highlight the issue of unbalanced data sets, particularly pertinent to soils as there is limited understanding of what exactly is being detected. We list the key research needs and highlight that integrating soil science and mechanistic modelling of soil processes and wave propagation as an essential component of developing reliable monitoring solutions. Embracing these interdisciplinary avenues will help develop sensing capabilities for soils in robust scientific principles and mitigate the risks of speculative overreach.