Area Occupied in Mexico Winter Sites

Area with monarchs roosting on trees (1 hectare = 2.5 acres).

Note year to year weather-driven variation, but long-term decline in monarch numbers illustrated by decade means.

[Data from 1993-2003: Monarch Butterfly Biosphere Reserve (MBBR, CONANP). Data from 2003-2021: WWF-Telcel Alliance, in coordination with the MBBR.]