Earthworms and soil invertebrates are among the most numerous animals on Earth. Emerging evidence of their sensitivity challenges their exclusion from welfare consideration.
The welfare status of earthworms and soil invertebrates is genuinely uncertain but warrants consideration given the numbers involved. If earthworms have any capacity for aversive experience, the scale of agricultural soil disturbance represents welfare harm at a magnitude that dwarfs all other human-caused animal suffering combined. This is not a settled scientific question — earthworm sentience is far less supported than vertebrate sentience — but the combination of behavioral evidence for nociception and the astronomical scale of potential impact makes it a morally serious uncertainty. At minimum, agriculture practices that protect soil invertebrate populations serve biodiversity goals that benefit the welfare of ecologically dependent animals with more certain sentience.