Monarch butterfly overwintering colonies in Mexico and California face temperature and precipitation threats from climate change, creating welfare and conservation challenges for both western and eastern populations.
The welfare implications of overwintering colony disruption for monarchs span the scale from individual insects experiencing hypothermia and storm stress to the loss of millions of individuals in catastrophic weather events at concentrated sites. Whether insects experience suffering in a morally relevant sense remains scientifically contested, but the scale of mortality in overwintering events — potentially involving billions of individuals — warrants precautionary welfare concern even under uncertainty. More concretely, the ecological loss of monarch migration represents a profound reduction in natural richness that affects ecosystems, human wellbeing, and the sense of wonder associated with one of nature's most spectacular phenomena. Protecting overwintering sites and addressing climate change simultaneously serve ecological, precautionary welfare, and cultural values.