While moving a whole forest may sound like a drastic measure, “desperate times call for desperate measures,” says Karen Oberhauser, a conservation biologist at the University of Wisconsin–Madison who wasn’t involved in the research. “If we don’t help organisms move around, you know, we’re just going to lose a lot of ecosystems.”

“I know that this sounds crazy, but we need to move the forests to a higher elevation,” says Cuauhtémoc Sáenz-Romero, a forest geneticist at Universidad Michoacana de San Nicolás de Hidalgo in Morelia, Mexico. Oyamel fir, which grow from around 2,400 meters to 3,500 meters, need cold mountain air to survive. The high-elevation chill also works to slow the metabolism of butterflies, allowing them to survive the long winter. As central Mexico gets warmer, new generations of oyamel fir will likely creep higher up their native slopes. They could soon run out of mountain to climb.

Sáenz-Romero wants to move the trees to taller mountains, but he’s aware that they won’t get there by themselves. “Unfortunately, the scene in The Lord of the Rings, where the trees are walking toward battle — it’s just fiction. It doesn’t happen.”

His team collected oyamel fir seeds from elevations between 3,100 meters and 3,500 meters inside the Monarch Butterfly Biosphere Reserve in Michoacán state and grew them temporarily in a tree nursery. Then, in partnership with the Indigenous community in Calimaya, the team planted around 960 trees at four different elevations in the community’s forest on the Nevado de Toluca volcano.

Some seedlings were planted at 3,400 meters — similar to typical oyamel fir that live inside the butterfly preserve. But Sáenz-Romero wanted to determine just how much altitude an oyamel could take. Other trees were planted higher, in colder climates, at 3,600, 3,800 and 4,000 meters above sea level.

If the fir could take root at higher-than-normal elevations, the trees might thrive there in the future as temperatures warm, Sáenz-Romero hoped.

Three years post planting, the team found that young fir trees were smaller and shorter the higher they sat on Nevado de Toluca. Still, many made it past their first year, which can indicate long-term survival. On average, 80 percent of the seedlings that got moved to locations 2.3 degrees Celsius colder than their home regions, survived at least three years.

Turning the experiment into reality likely would face many hurdles, including getting community and government support. And even if the trees can survive longer term, another question remains: Will the monarch butterflies find them?