Monarch butterfly populations have declined by 80% in North America since the 1990s, driven by milkweed loss from herbicide use on GM crops, logging of Mexican overwintering forests, and climate disruption of migration timing.
Monarch larvae that cannot find milkweed starve. Adults that complete the 4,000km migration to Mexico only to find degraded overwintering habitat face cold exposure and starvation. Pesticide exposure causes sublethal effects including impaired navigation and flight ability. The welfare of individual monarchs across their range is inseparable from the population-level conservation crisis caused by agricultural transformation of the Midwest landscape.