BioDive4Soil - A systematic survey of soil biodiversity for soil health evaluation 

The decline in biodiversity in conjunction with global change poses a severe threat to ecosystem functioning and long-term resilience. Soils host around 60 % of all species on earth, yet our knowledge of soil biodiversity across different land-use types and the drivers of biodiversity change remains limited. Recognizing its importance, several national and international legislative frameworks call for a systematic monitoring and reporting of the biological state of soils, with the goal of assessing, protecting and restoring soil biodiversity and the services it provides. A prominent example is the European Soil Monitoring and Resilience Law (EU 2025/2360), which aims to halt soil biodiversity loss and achieve healthy soils by 2050.The German Environment Agency (UBA) has launched a high-impact research program in collaboration with the Fraunhofer-Gesellschaft and ten other institutions to advance preparedness in soil biodiversity assessment and evaluation of soil health. The BioDive4Soil project – a large-scale systematic survey of soil biodiversity – aims to assess soil biodiversity across Germany, covering a wide range of habitats, land-use types, and soil regions. By determining the morphological, functional, and molecular diversity of soil microorganisms and fauna, it will establish baseline knowledge of soil community composition. In addition, eDNA-metabarcoding and barcoding of individual species across different soil organism taxa will improve genomic reference databases. Data gathered from near-natural ecosystems and across a gradient of increasing land-use intensity will help defining soil biological reference values indicative of healthy soils, as well as drivers of soil community composition such as land-use management, soil type and pollution.Currently, UBA relies on indicators derived from case studies in selected regions to fulfil its reporting obligations on soil biodiversity. One central aim is therefore to further develop sensitive and specific indicators for the biological state of soil, allowing, where possible, to discriminate between good, moderate and poor soil health status based on soil biodiversity metrics. The systematics of indicators in the different frameworks also raise questions regarding the long-term availability of consistent data and the definition of target values for soil biodiversity.