Earthworms are critical ecosystem engineers with basic nociceptive capacity. Agricultural practices including tillage, pesticide use, and soil compaction kill vast numbers annually.
Whether earthworms can suffer in a morally significant sense is genuinely uncertain. They have nociceptors and show withdrawal responses to damaging stimuli, but their nervous system is far simpler than vertebrates and likely lacks the structures associated with subjective suffering. However, from an ecological welfare perspective, the loss of earthworm populations has cascading effects on the welfare of all animals depending on healthy soil ecosystems. Agricultural practices that maintain earthworm populations — no-till, organic matter addition, reduced pesticide use — represent a form of ecosystem welfare that benefits vast numbers of dependent species from birds to mammals to other invertebrates.