Monarch butterflies overwinter in dense colonies in Mexican mountain forests, where logging and climate variability threaten their survival. Protecting these sites directly improves the welfare of billions of individual insects.
The overwintering aggregations of monarch butterflies represent a concentration of individual animals at extraordinary density, making the welfare of this site directly relevant to the welfare of hundreds of millions of individual insects. Logging that reduces forest canopy exposes butterfly clusters to lethal temperature swings. Severe storms that saturate clusters with rain cause mass mortality through hypothermia. Whether butterflies experience suffering in a morally significant sense is uncertain, but the scale of potential harm — hundreds of millions of individuals at a single site — warrants serious consideration under precautionary welfare principles. Protecting overwintering habitat through forest conservation and climate policy is simultaneously a conservation and a potential welfare intervention of extraordinary scale.