Monarch butterfly populations have collapsed dramatically over recent decades, with migratory individuals facing habitat loss, pesticides, and climate disruption across their range.
The welfare of individual monarch butterflies is affected by the degradation of every component of their migratory system. Larvae that consume milkweed contaminated with neonicotinoids suffer neurological disruption and reduced survival. Adults that migrate through landscapes stripped of nectar-producing wildflowers face energetic depletion — a physiological state of growing distress. Climate disruption of migration timing may strand monarchs in conditions outside their thermal tolerance. Whether individual insects have subjective experience of these stressors is uncertain, but the precautionary principle — and the intrinsic value of these extraordinary animals — supports acting to prevent their suffering and extinction. Simple, scalable actions at the individual level (planting milkweed and native wildflowers) have documented population-level benefits.