The welfare of soil invertebrates - earthworms, beetles, millipedes and others - is rarely discussed but may affect more individuals than all other animal welfare issues combined. What does science say?
Wild invertebrate welfare sits at the most uncertain frontier of animal ethics. Whether earthworms, beetles and other soil invertebrates have subjective experiences of pain and suffering is genuinely unknown - they have simple nervous systems but demonstrate nociceptive responses. The precautionary principle applied to the scale of potential suffering - billions to trillions of invertebrates affected by farming practices annually - suggests taking this question seriously even under uncertainty. Practical welfare improvements that also benefit ecosystems - reduced tillage, pesticide reduction, organic farming - can be advocated on both welfare and environmental grounds without requiring certainty about invertebrate sentience.