Earthworm populations and their drivers in agroecosystems across Europe: land use, soil properties, climatic factors

Earthworms are a crucial part of soil biodiversity and indicate soil health, as they constitute the majority of soil macrofauna affecting various soil functions and ecosystem services. Among the most important drivers of the size and diversity of earthworm populations is land use, especially agriculture. It is widely known that agricultural activities such as tillage, fertilization or the use of agrochemicals directly and indirectly affect earthworms. However, it is rarely investigated to what extent soil properties and climatic factors interact with the influence of agricultural activities. To study this, we analysed datasets of earthworm surveys across 35 European countries covering various agricultural sectors, various soil types and climatic regions including mediterranean, oceanic, and continental climates, across several altitudinal ranges. Investigations were performed within the project MINOTAUR within the European Joint Programme Soil. Data on earthworm abundance and biodiversity in agroecosystems was collated from public sources containing FAIR (findability, accessibility, interoperability, and reusability) data such as GBIF, Edaphobase, datadryad, or zenodo, including many historical and non-English studies to prevent a publication bias. Moreover, long-term ecological research sites were sampled for earthworms as part of the project. The greatest challenge in collating earthworm data was to find meta-data regarding agricultural activities, soil properties and climatic data of the study sites. Moreover, data quality varied considerably, often lacking standard vocabulary, consistent species nomenclature, and details on sampling designs. Thus, preliminary outcomes of our analysis are (i) the need for data harmonization in biodiversity monitoring, (ii) the inclusion of a minimal set of meta-data regarding soil properties, land use intensity, and sampling methodology in order to be able to examine the drivers of earthworm populations in agricultural systems. After a tedious data harmonization process we will analyse our data using structural equation models, to determine which factors had the biggest impacts on earthworm abundance and biodiversity. Using this information, we can better understand earthworm population developments, and promote strategies to foster soil protection and earthworm biodiversity on a European scale.