Earthworms are fundamental to soil health and are harmed by intensive agriculture. Emerging discussion about invertebrate welfare extends to earthworms as a frontier case.
Earthworm welfare represents the most contested frontier of invertebrate ethics. Their nervous system is far simpler than insects, and the evidence for sentience is extremely weak. However, earthworms do display avoidance responses to noxious stimuli, suggesting some form of nociception. At the scale of agricultural ploughing - killing millions of earthworms per field per tillage operation - even very small probabilities of suffering carry aggregate moral weight under the precautionary principle. The policy case for reduced tillage rests primarily on soil health and carbon sequestration, but welfare considerations add further motivation for reducing soil disturbance.