The relationship between erosion and biodiversity is reciprocal. Soil organisms can both reduce soil loss, by improving porosity, and increase it, by diminishing soil stability as a result of their mixing activities. Simultaneously, soil runoff has ecological impacts on belowground communities. Despite clear research into interactions, soil erosion models do not consider biodiversity in their estimates and soil ecology has poorly investigated the effects of erosion. In order to start filling in these research gaps, we present a novel biological factor and introduce it into a well‐known soil erosion model (the revised universal soil loss equation). Furthermore, we propose insights to advance soil erosion ecology. We present three pathways to fill in current knowledge gaps in soil biodiversity and erosion studies: (a) introducing a biological factor into soil erosion models; (b) developing plot‐scale experiments to clarify and quantify the positive/negative effects of soil organisms on erosion; (c) promoting ecological studies to assess both short‐ and long‐term effects of soil erosion on soil biota. We develop a biological factor to be included in soil erosion modelling. Thanks to available data on earthworm diversity (richness and abundance), we generate an “earthworm factor”, incorporate it into a model of soil erosion and produce the first pan‐European maps of it. New estimates of soil loss can be generated by including biological factors in soil erosion models. At the same time, the effects of soil loss on belowground diversity require further investigation. Available data and technologies make both processes possible. We think that it is time to commit to fostering the fundamental, although complex, relationship between soil biodiversity and erosion.