The new EU Soil Strategy aims to restore soil health across Europe by 2050, yet few Member States have defined biological criteria to assess progress. This study explores the challenges of establishing such criteria using bioindicators within uniform soil units. Due to limited data and environmental variability, criteria could only be defined in France for earthworms in certain soil types. The authors highlight three key priorities: harmonising definitions across countries, incorporating climate-specific thresholds, and standardising sampling protocols. Temporary solutions are proposed to address data gaps, while long-term success depends on integrated data systems and consistent monitoring frameworks.