Monarch Butterfly Biosphere Reserve

The Monarch Butterfly Biosphere Reserve is a World Heritage Site containing most of the overwintering sites of the eastern population of the monarch butterfly. The reserve is located in the Trans-Mexican Volcanic Belt pine-oak forests ecoregion on the border of Michoacán and State of Mexico, 100 km, northwest of Mexico City. Millions of butterflies arrive in the reserve annually. Butterflies only inhabit a fraction of the 56,000 hectares of the reserve from October–March. The biosphere's mission is to protect the butterfly species and its habitat.

Most of the overwintering monarchs from eastern North America are found here. Researchers discovered these areas in 1975. Presidential decrees in the 1980s and 2000 designated these still privately held areas as a federal reserve.

Source: Wikipedia