Monarch butterflies undertake one of nature's most remarkable migrations — but population declines of over 80% raise welfare and ecological concerns about the fate of billions of individual insects each year.
The welfare status of monarch butterflies raises the same uncertainty as other invertebrates — whether individual butterflies experience suffering in a morally relevant sense. But even setting welfare aside, the scale of population collapse represents ecological loss of enormous consequence: cascading effects on pollination, food webs, and the ecosystems through which billions of butterflies once moved. If butterflies have even limited capacity for suffering, the scale of harm from habitat loss, pesticide exposure, and migration disruption is significant. Conservation actions that restore milkweed, reduce pesticide use, and protect overwintering sites deliver both ecological and potential individual-level welfare benefits.