Migratory Monarchs Threatened by Deforestation
By MARK LORENZANA
March signals the end of overwintering for monarch butterflies in Mexico, and their migratory patterns dictate that they fly back north to the United States and Canada, leaving behind the warm, forested mountains of Mexico that they temporarily call home for four months.
On Tuesday, March 21, Mexico’s National Commission for Protected Natural Areas (CONANP), the Secretariat of the Environment and Natural Resources (Semarnat) and the World Wildlife Fund (WWF) conducted a joint press conference in Mexico City to report on the recent butterfly migration to the country, which usually starts in October and ends this month.
Jorge Rickards, director of WWF Mexico, said that one of the first sightings of monarchs last year occurred on Oct. 11 in Ciudad Acuña, in the northern Mexican state of Coahuila, as reported by the Coahuila-based Correo Real Monarch Project, which is strategically located along the butterflies’ migration route.
As one of the first areas in the country to welcome the monarch butterflies along their migratory route, for a few weeks in October, Coahuila bears witness to thousands of the brightly colored insects flying overhead — but rarely do any of the monarchs settle there. Their final destinations include the forests in the western Mexican state of Michoacán and the State of Mexico (Edoméx).
The butterflies start arriving in their hibernation sanctuaries in Michoacán and Edoméx in November, which tourists can visit to see the monarchs in their natural habitat.
According to Humberto Adán Peña Fuentes, head of the CONANP, there were 11 monarch colonies registered in Mexico for the wintering season of 2022-2023, which spanned a total of 2.21 hectares of occupied forest. Eight of the 11 colonies were situated in Michoacán, and three were located in Edoméx. Peña Fuentes said that six colonies were located within the Monarch Butterfly Biosphere Reserve (RBMM) and five outside of it.
However, the total monarch colonies for this wintering season in Mexico decreased by 22 percent compared to the 2021-2022 season, which spanned 2.84 hectares of occupied forest. So far, the record hibernation season was registered in 2018-2019, which had a total of 6.05 hectares occupied.
The reduction in number of colonies for this hibernation season can be attributed to migration instability, according to Rickards, along with a host of other more worrying factors.
“The reduction of breeding habitat in the United States due to the use of herbicides, land use change in North America, forest degradation in wintering sites in our country and, above all, extreme weather conditions in all terrestrial ecosystems of the continent, negatively impact the population of the Monarchs,” said Rickards.
Gloria Tavera, CONANP director of conservation, shared that in the last monitoring of the forests where the monarchs decide to settle for their hibernation, the CONANP detected that the three main causes of degradation are forest fires, logging and forest sanitation — which, ironically, is the removal of dead, damaged or susceptible trees, essentially to prevent the spread of pests or pathogens and to promote forest hygiene.
Tavera said that they are working continuously with the local communities, the federal government and private companies to help preserve more forest cover to further strengthen — and, hopefully, increase in the future — the monarchs’ migratory population.
Rickards called on Mexico, Canada and the United States to continue a coordinated effort to protect the overwintering of monarchs in North America.
“It is not just about conserving a species, but a unique migratory phenomenon in nature, which contributes to maintaining the health and diversity of terrestrial ecosystems when butterflies carry pollen from one plant to another,” said Rickards. “Continuing to have clean water and food in our homes means worrying about all pollinators, since about 80 percent of the food we grow needs to be pollinated to reproduce.”
The butterflies travel up to 4,000 kilometers from Canada and the United States to the forests of Michoacán and Edoméx, which is why they require a large area of forest cover to hibernate.
After spending several months in Mexico to escape the frigid winter, the monarchs return north beginning in March, starting the cycle again as they lay their eggs in northern Mexico and the southern United States.