Towards valuation of biodiversity in agricultural soils: A case for earthworms

Soil biodiversity is deteriorating in Europe due to an on-going intensification of agriculture, climate change and food production supporting measures of the European Common Agricultural Policy (CAP). Nevertheless, the CAP tries to take biodiversity into account via proposing a range of agri-environmental measures. These ES contribute to food security, climate change mitigation, water retention and plant biomass growth. Healthy soils also help to prevent erosion, desertification, and landslides and to stabilise crop yields. The provision of ES by soil biota is a result of their impact on soil processes in interaction with soil conditions as well as soil management practices of the farmers such as tillage or crop rotations. Some taxa amongst soil biota play key roles in regulating soil processes. With respect to biocontrol of soil-borne pests, the earthworm species Lumbricus terrestris is known to play an important role in suppressing toxigenic plant pathogens, such as Fusarium culmorum and its mycotoxin deoxynivalenol (DON). We highlight the importance of earthworms for pest control to conceptualise and show how farmers' management practices influence soil ecosystem services and outline how this can be examined in a socio-ecological context by providing a concrete example of an economical evaluation of ES provided by earthworms.