The plight of monarch butterflies raises questions about insect welfare at scale, as population crashes driven by habitat loss and pesticide exposure may involve large-scale suffering if insects are capable of experiencing it.
The welfare dimensions of monarch butterfly decline depend on the unresolved question of insect sentience. If monarchs experience their environment in ways that involve subjective states — if pesticide exposure causes something analogous to suffering, or population fragmentation causes something analogous to social isolation distress — then the 85% population decline represents a welfare catastrophe of enormous scale. Even under substantial uncertainty about the degree of insect sentience, the precautionary approach suggests that minimizing unnecessary harm to monarch populations is appropriate. The conservation interventions that protect monarch populations — milkweed planting, pesticide reduction, habitat protection — simultaneously address both the conservation concern and any potential welfare concern, making them doubly justified under a welfare-sensitive conservation framework.