Monarch butterfly populations have declined by over 80% in recent decades due to habitat loss, pesticide use, and climate change, raising questions about the welfare implications of mass invertebrate population collapses.
Whether monarch butterflies can suffer in a morally significant sense remains scientifically uncertain, but the mass collapse of populations does have clear welfare implications for predators and ecosystem services that other animals depend on. Setting aside the direct welfare question for butterflies, the ecosystem degradation signaled by monarch decline affects the welfare of many animals whose food webs depend on intact pollinator communities. Restoring monarch habitat by planting milkweed and reducing pesticide use is among the most accessible actions available to individuals seeking to improve ecological conditions for wildlife broadly.