Why Mexico May Disrupt Butterfly Migration

As the major path during butterfly migration, Mexico, the United States, and Canada all share responsibility for the conservation of the monarch butterflies. However, with the North American migratory path at risk, a biologist warns that the monarch may become a thing of the past, according to an article by Mexico News Daily.

Monarch Butterflies (danaus plexippus) are the only butterfly species that make a massive journey of up to 3,000 miles each year. These insects which have an average lifespan of six to eight months begin their migration each fall ahead of cold weather, which will kill them if they tarry too long.

While climate change may be one of the main factors that could disrupt butterfly migration, as billions of butterflies vanished in the period between 1990 and 2015 due to heatstroke and winter storm, part of the bigger picture are the environmental malpractices human beings, particularly those who live in the route from southeastern Canada to the fir tree forests of Michoacán and México state.

Víctor Sánchez-Cordero, a researcher at the National Autonomous University's Institute of Biology and Mexico's lead representative on a tri-national scientific committee that studies the monarch, blames the excessive use of herbicides and changes in the land use. Reduction in the availability of nectar and pollen is also considered a factor.

"The commitment to conserve this migratory phenomenon not only focuses on Mexico; it's a shared responsibility between our country, Canada and the United States," Sánchez-Cordero said.

The researcher, along with his team developed a system to monitor the migration of the monarch, said that there Mexico is not alone in carrying the responsibility of ensuring the continuation of the phenomenon through the conservation of forests in the Monarch Butterfly Biosphere Reserve (RBMM), located about 100 kilometers northwest of Mexico City.

That idea "has placed great international pressure on Mexico," Sánchez-Cordero said, adding that he and his team published an article in the journal Frontiers in Environmental Science that shows that the decline in the number of monarch butterflies migrating to Mexico is not due to deforestation in the RBMM.

According to the researcher, deforestation has been drastically reduced in the past 10 years yet butterfly population has continued to decline.

"The dramatic reduction in the density of monarch butterflies that arrive at overwintering sites in Mexico doesn't correlate with the loss of forest coverage, which shows that this factor is not responsible for the population reduction. ... Other hypotheses to explain the decrease must be sought," Sánchez-Cordero said.

He cited the excessive use of herbicides as one of the factors. This malpractice has killed milkweed, a plant that is a main food source for monarch butterflies and on which females lay their eggs. Sánchez-Cordero added that another factor is the reduced nectar and pollen in the United States and Canada as a result of deforestation.

According to the lead researcher, a network of conservation areas along the migration routes of monarch butterflies needs to be developed to conserve their migratory phenomenon. He added that the routes followed by the butterflies should be declared protected areas.

"A new conservation paradigm is needed. ... It's something that we [Mexico, the United States and Canada] should build together," Sánchez-Cordero said.

For the people of Mexico, these butterflies carry the souls of their ancestors, that is why maintaining a safe space for butterfly migration will not preserve ecological balance but also a piece of cultural heritage.