Monarch butterfly populations have declined by over 80% in recent decades. While their sentience is uncertain, the scale of loss and the suffering from habitat degradation warrant attention.
Monarch welfare considerations involve significant uncertainty about insect sentience, but the scale of population decline and the ecological disruption it represents justifies serious attention. Monarchs completing weakened migrations arrive at overwintering sites in poor physiological condition, reducing survival through winter. The loss of milkweed across the central US has eliminated breeding habitat that sustained billions of monarchs. Restoration of milkweed plantings and reduction of pesticide use can reverse this trend. Individual monarchs experiencing failed migrations may undergo physiological stress and starvation that, under any precautionary approach to insect welfare, warrants prevention.