Freshwater mussels are among the world's most imperiled animals, with North America hosting the world's greatest diversity but also the highest extinction rate, raising questions about welfare at immense scale.
The welfare status of freshwater mussels is deeply uncertain given their simple nervous systems and limited sensory capabilities. However, the ecological context of their decline creates welfare implications for the many animals that depend on healthy mussel-filtered water. The mass extinction of freshwater mussel species represents the loss of irreplaceable biodiversity. If mussels have any capacity for experience, the conditions killing them in impaired waterways - suffocation from silt, toxicity from agricultural runoff, thermal stress from temperature changes - would constitute welfare harms. The conservation urgency is clear regardless of the sentience question: North America's freshwater mussel extinction crisis represents one of the continent's greatest biodiversity failures.