Monarch butterflies undertake one of the most remarkable animal migrations on Earth. Habitat loss, pesticide use, and climate disruption have caused population declines of over 80% in recent decades.
Whether individual monarchs have welfare-relevant experiences remains scientifically uncertain, but the scale of population decline represents a profound loss of animal life and ecosystem function. Monarchs in decline face starvation when milkweed is absent, disorientation during migration from climate disruption, and death from pesticide exposure. Individual butterflies that fail to find nectar sources during migration die in ways that may involve negative experience. The most tractable interventions — planting milkweed and native flowering plants — are available to individuals in any region of the monarch range. Reducing pesticide use in gardens provides complementary benefit to monarchs and the many other insect species that share their habitats.