Monarch butterflies undertake one of the world's most spectacular migrations, but their overwintering sites in Mexico and California are under threat from logging, climate change, and extreme weather events.
While the sentience of individual butterflies remains scientifically uncertain, the welfare implications of monarch conservation are significant at ecosystem and population scales. Mass mortality events at overwintering sites — from extreme cold, disease, or habitat loss — kill millions of individual animals that may experience distress. Weakened butterflies unable to complete migration face physiological exhaustion and starvation. The catastrophic population decline represents a welfare crisis at scale even if individual insect experience is uncertain. The charismatic nature of monarchs has made them conservation ambassadors, and protecting their migration corridor delivers ecosystem welfare benefits for countless other species dependent on the same habitats.