Overview
- WWF’s 2025/26 winter survey found nine colonies in central Mexico, with three in Michoacán and six in the State of Mexico; five were inside the Monarch Butterfly Biosphere Reserve and four were outside protected areas.
- Researchers assess population size by mapping the forest area occupied by overwintering clusters rather than counting individual butterflies.
- It marks a second consecutive year of growth in the wintering area occupied by the migratory population.
- WWF warns the current level remains far below 1990s highs, noting a 1996/97 record of 18.19 hectares as a reference point.
- The organization cites herbicide use, land-use change and climate impacts as ongoing threats and urges tighter herbicide rules in North America, sustainable forestry in Mexico and stronger climate action.