Can moving trees save the monarch butterflies in Mexico?

An innovative project aimed at cultivating new oyamel fir forests in central Mexico holds promise for the survival of monarch butterflies, which rely on these trees for their winter hibernation. The ongoing threat of climate change has raised concerns that these crucial habitats could vanish by the end of the century. Researchers initiated this experiment by planting hundreds of young oyamel fir trees (Abies religiosa) approximately 100 kilometres away from their native forests, and recent findings indicate that a significant majority of these saplings are thriving.

The Need for Action

The undertaking is viewed as a necessary step in preserving ecosystems. Karen Oberhauser, a conservation biologist at the University of Wisconsin–Madison, emphasises the urgency of facilitating the movement of tree species in response to changing climates. Each autumn, monarch butterflies migrate from milkweed-rich regions in southern Canada to the mountainous oyamel fir forests in central Mexico. However, the combined challenges of declining monarch populations and climate change predict a dire future for these habitats.

Relocating Oyamel Fir Trees

Cuauhtémoc Sáenz-Romero, a forest geneticist at Universidad Michoacana de San Nicolás de Hidalgo, advocates for relocating oyamel fir to higher elevations, where they can endure the colder temperatures necessary for their survival. The existing trend shows that as temperatures rise, the oyamel fir may struggle to find suitable habitats within their current ranges. The project’s focus involves moving these trees to taller mountains, as they cannot relocate independently.

Planting and Early Results

The research team collected oyamel fir seeds from elevations between 3,100 to 3,500 metres within the Monarch Butterfly Biosphere Reserve in Michoacán state. Collaborating with the Indigenous community in Calimaya, they planted around 960 trees across various elevations on the Nevado de Toluca volcano. Early results from the experiment show that while seedlings planted at higher altitudes are smaller, a commendable survival rate of around 80 per cent after three years was observed.

Looking Ahead

Looking ahead, Sáenz-Romero acknowledges the challenges of garnering community and governmental support for such initiatives. A critical question remains: will the migrating monarch butterflies locate these newly established habitats? The winter of 2023–2024 saw some monarchs bypassing the traditional biosphere reserve in search of cooler environments, indicating their adaptability in the face of climate change.