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Soils are key components of our ecosystems and provide 95%–99% of our food. This importance is reflected by an increase in participatory citizen science projects on soils. Citizen science is a participatory research method that actively involves and engages the public in scientific enquiry to generate new knowledge or understanding. Here, we review past and current citizen science projects on agricultural soils across Europe. We conducted a web‐based survey and described 24 reviewed European citizen science projects in the light of the 10 principles of citizen science and identified success factors for citizen science. Over 66% of the projects generated soil biodiversity data; 54% and 42% of the projects generated data on vegetation cover and soil organic carbon, respectively. Our findings show that soil citizen science projects aligned with the 10 principles of citizen science offer an unexploited resource for European soil health research. We conclude that promoting co‐creation, fostering knowledge‐sharing networks and enabling long‐term communication and commitment with citizens are success factors for further development of citizen science on soils. [ABSTRACT FROM AUTHOR]

Land‐use change and habitat degradation are among the biggest drivers of aboveground biodiversity worldwide but their effects on soil biodiversity are less well known, despite the importance of soil organisms in developing soil structure, nutrient cycling and water drainage. Combining a global compilation of biodiversity data from soil assemblages collated as part of the PREDICTS project with global data on soil characteristics, we modelled how taxon richness and total abundance of soil organisms have responded to land use. We also estimated the global Biodiversity Intactness Index (BII)—the average abundance and compositional similarity of taxa that remain in an area, compared to a minimally impacted baseline, for soil biodiversity. This is the first time the BII has been calculated for soil biodiversity. Relative to undisturbed vegetation, soil organism total abundance and taxon richness were reduced in all land uses except pasture. Soil properties mediated the response of soil biota, but not in a consistent way across land uses. The global soil BII in cropland is, on average, a third of that originally present. However, in grazed sites the decline is less severe. The BII of secondary vegetation depends on age, with sites with younger growth showing a lower BII than mature vegetation. We conclude that land‐use change has reduced local soil biodiversity worldwide, and this further supports the proposition that soil biota should be considered explicitly when using global models to estimate the state of biodiversity. [ABSTRACT FROM AUTHOR]

Motivation and aim: Soil biodiversity is central to ecosystem function and services. It represents most of terrestrial biodiversity and at least a quarter of all biodiversity on Earth. Yet, research into broad, generalizable spatial and temporal patterns of soil biota has been limited compared to aboveground systems due to complexities of the soil system. We review the literature and identify key considerations necessary to expand soil macroecology beyond the recent surge of global maps of soil taxa, so that we can gain greater insight into the mechanisms and processes shaping soil biodiversity. We focus primarily on three groups of soil taxa (earthworms, mycorrhizal fungi and soil bacteria) that represent a range of body sizes and ecologies, and, therefore, interact with their environment at different spatial scales. Results: The complexities of soil, including fine‐scale heterogeneity, 3‐D habitat structure, difficulties with taxonomic delimitation, and the wide‐ranging ecologies of its inhabitants, require the classical macroecological toolbox to be expanded to consider novel sampling, molecular identification, functional approaches, environmental variables, and modelling techniques. Main conclusions: Soil provides a complex system within which to apply macroecological research, yet, it is this property that itself makes soil macroecology a field ripe for innovative methodologies and approaches. To achieve this, soil‐specific data, spatio‐temporal, biotic, and abiotic considerations are necessary at all stages of research, from sampling design to statistical analyses. Insights into whole ecosystems and new approaches to link genes, functions and diversity across spatial and temporal scales, alongside methodologies already applied in aboveground macroecology, invasion ecology and aquatic ecology, will facilitate the investigation of macroecological processes in soil biota, which is key to understanding the link between biodiversity and ecosystem functioning in terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

Human impacts are causing an unprecedented change of biodiversity across scales. To quantify the nature and degree of the biodiversity change, there have been a number of meta-analysis studies investigating the effects of global change drivers (land use, climate, etc.). However, these studies include few primary literature studies of soil biodiversity. Soil biodiversity is important for a variety of ecosystem services that are critical for human wellbeing. Yet, we know little about how soil organisms may respond to changing environmental conditions. Although studies have investigated the impact of global change drivers on soil biodiversity, they lack sufficient depth in the number of drivers and/or taxa included. Additionally, the previous focus on aboveground organisms has also resulted in a bias towards certain global change drivers in the primary literature. For example, climate change and land use change are more often studied, whilst pollution is typically understudied as a global change driver. Building on previous studies, we will conduct a meta-analysis to compare the effects of global change drivers (land use, habitat fragmentation/loss, fire, climate change, invasive species, pollution, and nutrient enrichment) on soil fauna (micro- to macro-invertebrates). This project aims to fill the current gaps in the literature, and actively participate in incorporating soil biodiversity into future global biodiversity assessments, by creating the first global open-acess dataset on the impacts of multiple global change drivers on soil fauna. [ABSTRACT FROM AUTHOR]

The high biodiversity of soil ecosystems is often attributed to their spatial heterogeneity at multiple scales, but studies on the small-scale spatial distribution of soil macrofauna are rare. This case study of an Ash – Field Maple woodland partially converted to conifer plantation investigates differences between species assemblages of soil and litter invertebrates, and plants, using multivariate ordination and indicator species analysis for eleven microhabitats. Microhabitats representing the main body of uniform litter were compared with more localised microhabitats including dead wood and areas of wet soil. Species accumulation curves suggest that for this site it is more efficient to sample from varied microhabitats of limited spatial scale rather than the broad habitat areas when generating a species inventory. For comparative work sampling the main body of uniform litter is more appropriate, given that microhabitats vary from woodland to woodland and would make standardisation problematic. Vegetation showed more distinctive microhabitat-specific species assemblages than soil and leaf litter invertebrates and was strongly associated with environmental variables. Microhabitats with distinct assemblages included dead wood habitats, which had a high proportion of saproxylic species; a highly disturbed microhabitat with distinct plant and soil species characteristic of ruderal habitats and seeps with earthworm species rarely sampled in standard soil biodiversity surveys. The leaf litter in the conifer plantation area was species poor and the biodiversity quantified was considerably enhanced by the sampling from the additional microhabitats - illustrating the importance of small-scale heterogeneity for increasing plant and soil macrofauna biodiversity at this site. [ABSTRACT FROM AUTHOR]