Hundreds of millions of monarch butterflies overwinter in the oyamel fir forests of central Mexico's Monarch Butterfly Biosphere Reserve. By 2026, logging, climate volatility, and milkweed loss across their North American breeding range have pushed overwintering populations to critically low levels.
Overwintering monarchs crowded at critically low population sizes face heightened risks: a single climate event can eliminate a significant fraction of the entire population. Illegal logging reduces forest canopy, exposing clusters to lethal temperature fluctuations. While individual butterfly sentience remains debated scientifically, population-level welfare — the ability of the species to complete its extraordinary migratory lifecycle — is clearly compromised. Conservation welfare focuses on habitat protection, community-based forest guardian programs, and milkweed restoration across the breeding range.