Monarch butterfly populations have collapsed by over 80% in recent decades due to milkweed loss, pesticides, climate change, and logging of overwintering sites, threatening one of nature's great migrations.
The question of insect welfare is scientifically uncertain, but the scale of monarch decline is staggering enough to merit attention on both ecological and potentially welfare grounds. Monarch caterpillars and adults may experience something analogous to distress when their nutritional needs cannot be met - milkweed-deprived larvae frequently die of starvation before completing development. Pesticide exposure causes death through neurotoxicity. If insects have even rudimentary capacity for suffering, the billions of monarchs killed through habitat destruction and pesticide exposure represent welfare impacts of enormous scale. The ecological loss also harms countless other species that benefit from monarch-associated habitats.