Soil organisms provide crucial ecosystem services that support human life. However, little is known about their diversity, distribution, and the threats affecting them. Here, we compiled a global dataset of 60 sampled earthworm communities from over 7000 sites in 56 countries to predict patterns in earthworm diversity, abundance, and biomass. We identify the environmental drivers shaping these patterns. Local species richness and abundance typically peaked at higher latitudes, while biomass peaked in the tropics, patterns opposite to those observed in aboveground organisms. Similar to many aboveground taxa, climate variables were more important in shaping earthworm communities than soil properties or habitat 65 cover. These findings highlight that, while the environmental drivers are similar, conservation strategies to conserve aboveground biodiversity might not be appropriate for earthworm diversity, especially in a changing climate.

Summary In the Netherlands soil biological measurements are undertaken in a nationwide monitoring programme. The measurements are combined in the Biological Indicator of Soil Quality (BISQ). About 300 locations were selected in a random stratified design comprising stringent combinations of land use and soil type. All locations were sampled in a six‐year cycle. In this contribution we describe the monitoring network and the BISQ and present average values for biomass, abundances and taxonomic diversity of various soil dwelling organisms derived from 10 years of measurements. We further highlight some results and discuss the possibilities in soil and land management policy frameworks for improving sustainable land management.

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max. 125 words) 53 Soil organisms are crucial for ecosystem services that support human life. However, little is 54 known about the distribution, diversity and threats facing them. Here, we compiled a global 55 dataset of sampled earthworm communities from over 7000 sites in 56 countries to predict 56 patterns in earthworm diversity, abundance, and biomass. Further, we identify the 57 environmental drivers shaping these patterns. Local species richness and abundance typically 58 peaked at higher latitudes, while biomass peaked in the tropics, patterns opposite to that 59 observed in many aboveground taxa. But similar to many aboveground taxa, climate variables 60 were more important in shaping earthworm communities than variables relating to soil or habitat 61 cover. These findings highlight that, while the environmental drivers are similar, conservation 62 strategies to conserve aboveground biodiversity might not be appropriate for earthworm 63 diversity. 64

Soil is one of the most biodiverse terrestrial habitats. Yet, we lack an integrative conceptual framework for understanding the patterns and mechanisms driving soil biodiversity. One of the underlying reasons for our poor understanding of soil biodiversity patterns relates to whether key biodiversity theories (historically developed for aboveground and aquatic organisms) are applicable to patterns of soil biodiversity. Here, we present a systematic literature review to investigate whether and how key biodiversity theories (species–energy relationship, theory of island biogeography, metacommunity theory, niche theory and neutral theory) can explain observed patterns of soil biodiversity. We then discuss two spatial compartments nested within soil at which biodiversity theories can be applied to acknowledge the scale‐dependent nature of soil biodiversity.