The Impact of Climate Change on Monarch Butterflies' Winter Habitat
Annually, the onset of November marks a remarkable natural phenomenon in Michoacán, Mexico, where vast numbers of monarch butterflies migrate to their wintering sanctuary. This spectacle unfolds within the Monarch Butterfly Biosphere Reserve, situated approximately 100 kilometers west of Mexico City. The butterflies embark on an arduous journey of over 4,000 kilometers from their breeding grounds in northern United States and southern Canada, seeking refuge from the winter chill.
Hibernating in the oyamel fir trees located in the Ejido el Rosario region, these butterflies congregate to shield themselves against harsh weather conditions, including cold nights and strong winds. The survival of these insects depends significantly on the presence of oyamel fir trees, as they provide a unique microclimate necessary for the butterflies' hibernation.
According to researchers, the oyamel fir thrives in a distinct climatic niche that is both humid and cold, predominantly found in the high mountains of central Mexico. As climate change progresses, studies predict a gradual decline of this vital forest habitat, which poses a serious threat to the monarch butterfly population.
The canopy of oyamel firs plays a crucial role in regulating temperature and humidity for the butterflies. During the day, the shade offered by the trees keeps the environment up to 5 degrees Celsius cooler, while at night, it retains warmth, creating a protective habitat essential for the butterflies' survival. The canopy also acts as a barrier against winter precipitation, preventing the butterflies from freezing in the event of wet wings.
As the butterflies emerge from hibernation and mate in central Mexico, they must migrate northward to Texas to lay their eggs. For this journey, they rely on energy reserves accumulated during their wintering period. The oyamel firs are instrumental in this process by providing a stable and suitable habitat to sustain the butterflies during winter.
However, projections indicate that by 2090, the climate conditions favorable for oyamel firs may no longer exist in their current location. The rise in temperatures is already contributing to forest decline, prompting conservationists to take action. Cuauhtémoc Sáenz Romero, a professor at the Universidad Michoacana de San Nicolás de Hidalgo, is at the forefront of efforts to establish new overwintering sites for the monarchs.
Over the past two decades, Sáenz Romero has been actively involved in conserving the coniferous forests of Michoacán. His recent initiatives include planting oyamel firs on higher altitudes, specifically on the Nevado de Toluca volcano, a designated Protected Natural Area. This strategic move aims to create new habitats for the butterflies as temperatures rise and current habitats become unsuitable.
Collaborating with the indigenous community of Calimaya in the neighboring State of Mexico, Sáenz Romero's team has been working to plant these firs in locations that offer cooler climates. This approach, known as assisted migration, seeks to develop new forests that can serve as sanctuaries for the monarch butterflies.
With the indigenous community's extensive ecological knowledge, the project has seen the successful transplantation of pine seedlings from the Monarch Butterfly Biosphere Reserve into a community nursery. From there, these seedlings are planted across different altitudes in the Nevado de Toluca region, allowing researchers to monitor their growth and adaptability to changing climate conditions.
As of now, nearly 1,000 seedlings have been planted at varying altitudes, with the highest site reaching 4,000 meters. This initiative aims to identify the maximum elevation at which oyamel firs can survive in the current climate scenario. Early observations suggest that the migrating monarchs have begun to establish colonies in cooler areas of Nevado de Toluca, indicating a potential shift in their wintering behavior.
The primary challenge lies in the rapid pace of climate change, which exceeds the natural ability of ecosystems to adapt. While forests can migrate gradually through the dispersal of seeds, this process is inherently slow. Sáenz Romero emphasizes the necessity for human intervention to facilitate this transition and mitigate the impact of climate change on the monarch butterfly population.
Despite some conservationists expressing skepticism about relocating forests, Sáenz Romero advocates for a dual approach that includes both the preservation of existing habitats and the creation of new ones. This strategy aims to ensure the survival of the monarch butterflies while addressing the urgent challenges posed by climate change.
As the project continues, the hope is that the newly established oyamel fir forests will eventually attract migrating monarchs, providing them with a safe haven in the face of a rapidly changing environment.
