Soil fauna diversity and chemical stressors: a review of knowledge gaps and roadmap for future research

Abstract

Soils harbour highly-diverse invertebrate communities that play important roles for ecosystem services, including the mitigation of environmental pollution. Chemical stressors, such as pesticides, pharmaceuticals and metals, are being increasingly spread into ecosystems due to human activities. While it is crucial to predict the consequences of chemical stressors for soil biodiversity, chemical toxicity is often assessed using individuals or populations in laboratory cultures. There has been no systematic evaluation of the evidence documenting the impacts of chemical stressors on diverse, natural soil communities. Here, we use a comprehensive literature review of 274 studies to evaluate the current state of knowledge about the effects of chemicals on soil fauna communities. Most research has had limited spatial scope, with noteworthy gaps in the regions that are potentially the most threatened by soil pollution (Southern Hemisphere). Furthermore, reports generally were constrained to a few emblematic soil fauna groups (nematodes, collembola and earthworms) and chemical stressors (metals). Future research should address biases in spatial distribution of studies, as well as the taxonomic groups and chemical compounds considered. Specifically, emphasis on indirect effects mediated by species interactions, ecosystem functioning and interactive effects of stressors and climate change, currently lacking in the literature, is needed to improve soil-biodiversity conservation and restoration efforts, as well as predictions of global diversity change.

Challenges of and opportunities for protecting European soil biodiversity

“…Thereby, baselines will also promote the investigation and monitoring of threats to soil biodiversity and ecosystem functions. Such threats need to be redefined (e.g., species invasions that are often unconsidered when using soil inocula in agricultural systems [Ambrosini et al., 2016]) and thresholds for threat levels that cause detrimental or irreversible changes in soil communities need to be estimated (Beaumelle et al., 2021). It is also important to agree on a common definition of soil biodiversity (Orgiazzi, 2022), which is necessary to create soil‐specific species lists for nature conservation; recent soil biodiversity reports (e.g., Orgiazzi et al., 2016; FAO et al., 2020) can serve as a basis.…”

Frontiers in soil ecology—Insights from the World Biodiversity Forum 2022

“…Furthermore, the recent surge in high‐resolution remote‐sensing products has been less expansive for soil properties, due to the inherent issues related to assessing belowground conditions from space. For several other, less common drivers, such as pesticides (Beaumelle et al, 2021; Edlinger et al, 2022; Riedo et al, 2021), antibiotics, other—often new—chemical substances, such as PFAS (perfluoroalkyl and polyfluoroalkyl substances), heavy metals and microplastics (Rillig et al, 2019; Steiner et al, 2022), global coverage is even lower: Assessing and predicting underrepresented drivers : Importantly, while assessment of the current levels and implications of most of these environmental conditions is scattered at best, many of them are also rapidly changing under global change. Assessments of ongoing changes, let alone predictions of future changes or reconstructions of past changes, are rare even for soil temperature (Lembrechts & Nijs, 2020) and nonexistent at the large scale for most of the other environmental parameters covered above.…”

“…Furthermore, the recent surge in high-resolution remote-sensing products has been less expansive for soil properties, due to the inherent issues related to assessing belowground conditions from space. For several other, less common drivers, such as pesticides (Beaumelle et al, 2021;Edlinger et al, 2022;Riedo et al, 2021), antibiotics, other-often new -chemical substances, such as PFAS (perfluoroalkyl and polyfluoroalkyl substances), heavy metals and microplastics (Rillig et al, 2019;Steiner et al, 2022), global coverage is even lower:…”

“…Widespread monitoring of soil environmental conditions, and especially soil contamination, is therefore needed (Hou & Ok, 2019). Especially rare and often overlooked contaminants should become part of government monitoring programmes, and be analysed across biomes and along elevational and latitudinal gradients, in different land-use types and including nature-protection areas, where they are not applied (Beaumelle et al, 2021). Indeed, limited but important data on soil organisms show that latitudinal and altitudinal patterns of aboveground biodiversity are often in opposite directions compared to belowground ones (e.g., Decaëns, 2010;van den Hoogen et al, 2019;Phillips et al, 2019;Tedersoo et al, 2014).…”

“…Indeed, for many specific groups of soil biota, we have very little understanding of how they respond to changes in these parameters. The remaining key questions are (i) if these compounds impair (or improve) the functioning of specific groups or soil biodiversity and functioning as a whole, (ii) if and how multiple contaminants interact (Rillig et al, 2019;Thakur et al, 2018), (iii) how they interact with climate change (Beaumelle et al, 2021) and ( 4) what (often nonlinear) shapes these relationships take (Saleem et al, 2019)? (Guerra et al, 2021b;Orgiazzi et al, 2018):…”