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date: 01 October 2022

Monarch Butterfly Conservation (Mexico)locked

Monarch Butterfly Conservation (Mexico)locked

  • Will WrightWill WrightHistory Department, The University of British Columbia


One of the most spectacular biological spectacles on the North American continent must be the annual migration of monarch butterflies. For eight months out of the year, beginning each spring, the winged wanderers spread out over two million square miles, from Minnesota to Maine, Manitoba to Mississippi, as generations lay eggs on milkweeds as they move northward. The caterpillars that emerge munch on their host plant, internalizing toxic cardenolides found in some milkweeds as a defense against birds, then form chrysalids to metamorphose into adult insects with orange wings which signal their poisonous nature. By autumn, most butterflies east of the Rocky Mountains, though not all, go southward to central Mexico, funneling down and overwintering at a mountainous location covering 0.015 percent of the area they occupied in the summer. At the Transverse Neovolcanic Belt, a mature forest of Oyamel fir and Montezuma pine provides an ideal microclimate for these hibernating monarchs—too cold and they freeze to death, too warm and they perish burning up their fat reserves. Come spring, after clustering on the trees for about four to five months, they begin the migratory cycle again.

Before 1975, the monarch migration was basically a mystery. Canadians, Mexicans, and US residents had seen plenty of butterflies for centuries prior, but nobody understood the scope of this 2,800-mile journey until the late 20th century. Mexico’s Monarch Butterfly Biosphere Reserve, created by President Miguel de la Madrid in 1986, was limited in its ability to conserve overwintering forest land due to a commitment to austerity budgets after the Mexican debt crisis and the challenge of sustainable development for Mexican ejidos. Side accords to the North American Free Trade Agreement of 1994 promised greater cooperation among nation-states, but the loss of milkweed and nectar sources in the United States and Canada jeopardized trinational solidarity in conservation efforts. Debates over how to address illegal logging within the biosphere reserve divided those who favored surveillance and policing from those who advocated jobs and payments. Democratizing scientific knowledge first brought the monarch migration to the attention of the wider world, and democratizing income for conserved forests may offer a path to protecting it.


  • History of Mexico
  • 1945–1991
  • Environmental History

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