Such concerns motivated Sáenz Romero, ecological sciences professor Arnulfo Blanco García, and a crew of University of Michoacán students to establish an experimental forest plot on the Ejido La Mesa en Sierra Campanario near San Jose del Rincon in the state of Mexico.
While the area officially serves as a Monarch sanctuary and is part of the Monarch Butterfly Biosphere Reserve, few butterflies were present upon our visit there earlier this month. Signs of high temperatures, drought and the March 2016 storm that decimated more than 100 acres of forest and millions of butterflies were evident, however.
Sáenz Romero pointed out trees with skinny tops and a lack of foliage, which suggests a lack of water. A wet season and dry season typify the usual weather pattern here, he explained. But when the wet
Drought and high winds make the trees where the Monarchs roost vulnerable. Photo by Nicolas Rivard
season offers less rain than average and the dry season is warmer than usual, the trees can’t absorb enough water from the soil to reach the tallest limbs. Leaf and branch shedding result, creating weakened, scrawny treetops. This unhealthy state also makes the forest more susceptible to wind damage and insect attacks, said Sáenz Romero.
It wasn’t always this way, said Blanco García, taking in the vast expanse of oaks, pines and Oyamel, preferred by overwintering Monarchs. This area of Mexico has long relied on mining, which has posed different threats to the forest in the past, such as water pollution and deforestation.
Three-year-old Oyamel, sacred fir, planted in full sun. Photo by Nicolas Rivard
Three-year-old Oyamel, sacred fir, in mixed plant community that provides partial shade. Photo by Nicolas Rivard
“Sixty years ago, there was no forest here,” he said. “But when mining stopped in the area, the forest regenerated itself.” That was before climate change became the dominant factor it is today.
Saáenz Romero and Blanco García believe that within 70 years, the sacred firs hosting the Monarchs each winter will not be able to survive the increased temperatures and volatile weather predicted to rule the forest. The tree has a narrow window of temperature and altitude in which it can thrive, said Sáenz Romero.
With funding from Monarch Butterfly Fund in Minnesota, the Mexican Council of Science and TEchnology (CONACyT in Spanish), the Mexican Fund for the Nature Conservancy and the University of Michoacán, an experimental plot of Oyamel seedlings was placed 1,000 feet higher up the mountain than the existing sanctuaries–at 3,440 meters/11,286 feet. The approach, called assisted migration, has been successfully deployed in Canada. It aims to grow a replacement forest that in this case can be occupied by overwintering Monarchs when the roosting sites further down the mountain expire.
During a tour of the plot, now three years old, the scientists pointed out how Oyamel seedlings planted in combination with sage bushes and other tall perennials fared better than those placed in full sun. Because of the more severe dry season and higher temperatures, the Oyamels do better in a diverse plant community that offers shade at least part of the day.
“Weather proof” temperature monitor at the experimental forest in La Mesa. Photo by Nicolas Rivard
Also evident: the team’s unique resourcefulness. As students measured temperatures and moisture levels of the soil, an upside-down styrofoam cup wired to a stick raised questions. What is that?
“It’s our weather proof temperature monitor,” said Blanco García.
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