every year, in In early November, one of the world’s most impressive natural exhibits takes place in Michoacán, Mexico. Hundreds of millions of migratory butterflies live in the forests of the Monarch Butterfly Biosphere Reserve, about 100 kilometers west of Mexico City. Having flown south for eight months, they begin their journey in the northern United States or southern Canada, hibernating here before reuniting in the spring.
After flying more than 4,000 kilometers, these butterflies land on the oyamel fir trees in the Ejido el Rosario region, where they gather for weeks, protecting themselves from the wind and the cold of the night. Without these trees, butterflies would not be able to survive their exhausting journey.
The oyamel fir grows in a very narrow climate, one that is humid but cold. “Its distribution is limited to the highest mountains in central Mexico,” said Cuauhtémoc Sáenz Romero, a professor at the Universidad Michoacana de San Nicolás de Hidalgo. Sáenz Romero is the lead author of a recent study that predicts the forest will gradually decline and even disappear due to climate change, putting the butterflies at risk.
For monarchs, the oyamel canopy acts as a barrier to the temperature and humidity of the environment, explains Sáenz Romero. “During the day, under the shade of an oyamel, the environment is always 5 degrees Celsius cooler than outside. It is a protection against high temperatures. At night it’s the other way around, leading to a warmer 5 degrees Celsius.” The density of the canopy also protects from winter rain. “When the temperature drops below zero and butterflies wet their wings, they can freeze. That’s why these trees represent a place to live,” said Sáenz Romero.
After hibernating and mating in central Mexico, these insects fly north to Texas in the United States, where they lay their eggs. “For all this, they need electricity to come back, which they don’t have to use to fight the cold in the winter,” he explained.
This beautiful balance in their lives is only offered by oyamel firs. However, some species show that the climate that allows them will have disappeared in this area by 2090. “Due to the increase in temperatures, we are seeing a process of deforestation,” said Sáenz Romero, who is leading the initiative to establish new areas for winter planting. of kings, which are on the red list of endangered species.
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