page_title: Monarch Butterfly Biosphere Reserve
section_title: Monarch migration
hierarchical_section_title: Monarch Butterfly Biosphere Reserve / Monarch migration
caption_attribution_description: Monarchs (Danaus plexippus) overwintering in Oyamel Fir Trees at the Angangueo overwintering site in Mexico. (author/photographer - Barbara Page. source - personal visit to the Angangueo preserve in 2000.)
context_page_description: The Monarch Butterfly Biosphere Reserve is a World Heritage Site containing most of the over-wintering 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 over-wintering monarchs from eastern North America are found here. Western researchers discovered these areas in 1975. Presidential decrees in the 1980s and 2000 designated these still privately held areas as a federal reserve. The Reserve was declared a Biosphere Reserve in 1980 and a World Heritage Site in 2008. The reserve remains predominantly rural. Reserve administrators continue to be concerned with deleterious effects of illegal logging and tourism. Conservation efforts sometimes conflict with the interests of local farmers, community-based landowners, private land owners and indigenous people.
context_section_description: Millions of butterflies travel south into Mexico, from Texas and then follow the Sierra Madre Oriental mountains to the preserve.  The butterflies congregate, clustering onto pine and oyamel trees. To many, the trees appear orange and branches sag from the weight. In spring, these butterflies migrate across America, sometimes ending up in Eastern Canada. Over the time it takes them to make this journey, four generations of monarch butterflies are born and die. The monarch butterflies migration patterns are altered by climate change. During migration, monarchs fly north once they are exposed to cooler temperatures. Dense congregations are thought to conserve heat. If warmed by the sun, the butterflies take flight. The beating of their wings has been compared to the sound of a light rain. The reserve is susceptible to lethal, freezing temperatures.
caption: Cluster of monarchs on a tree limb near Angangueo
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