Scientists create new overwintering sites for monarch butterflies on a warming planet
The migration of the monarch butterfly is one of the wonders of the natural world. Each autumn, a new generation of monarch butterflies is born in the northern United States and southern Canada. Hundreds of millions of these ...
But under global warming, these forests are predicted to slowly move up the slopes. By approximately 2090 they will run out of mountain. It will thus be necessary to create new forests outside their current geographic range: for example on mountains further east, which are higher.
"Here we show the feasibility of planting new sacred fir forests on a nearby volcano, Nevado de Toluca, at altitudes between 3,400 and 4,000 meters," said Dr. Cuauhtémoc Sáenz-Romero, a professor at the Universidad Michoacana de San Nicolás de Hidalgo in Mexico, and the lead author of a study published in Frontiers in Forests and Global Change.
"We call this 'assisted migration': planting seedlings grown from seeds from existing sacred fir populations to new sites whose climate by 2060 is predicted to become similar to that at today's overwintering sites due to global warming."
Making a stand
In 2017, Sáenz-Romero and colleagues gathered seeds from cones from eight stands of sacred fir in the Monarch Butterfly Biosphere Reserve (MBBR) in Mexico, at altitudes between 3,100 and 3,500 meters. They grew seedlings from these, at first for two years in a shade-house at 1,900 meters altitude, and then for another year in a nursery at 3,000 meters.
Planting Abies religiosa (Sacred fir) seedlings under the shade of pre-existing shrubs (Senecio cinerarioides, narrow green-grayish foliage) as protective "nurse plants". Large trees on background are adult Pinus hartwegii, the pine that reaches the timberline. Abies religiosa is completely absent in this site at 3800 m of elevation, northeaster slope of Nevado de Toluca volcano, central Mexico, because it is too high in elevation. Planters personnel are locals of Native Indian origin. Credit: Cuauhtémoc Sáenz-Romero, UMSNH
Local foresters, graduate students and faculties from the state University of Michoacán, México, who established the experiments at Nevado de Toluca. This is a site at 3,600 m of elevation, shortly above the maximum natural limit distribution of Abies religiosa (about 3,550 m). Credit: Cuauhtémoc Sáenz-Romero, UMSNH
Planting Abies religiosa (Sacred fir) seedlings at the timberline (4,000 m of elevation) of Nevado de Toluca volcano, under the shade of preexisting Lupinus elegans as protective "nurse plants". This site is about 450 higher in elevation than the maximum natural distribution of Abies religiosa. Credit: Cuauhtémoc Sáenz-Romero, UMSNH
Abies religiosa (Sacred fir) seedlings produced in a communal nursery of Ejido La Mesa, at 3,000 m of elevation (to induce hardening of the seedlings), at the border of the MBBR. Seeds originated from the MBBR, and seedlings were planted later at Nevado de Toluca. On the photo, Francisco "Don Pancho" Ramirez-Cruz, former chief of Ejido La Mesa, was in charge of the seedling production. Credit: Cuauhtémoc Sáenz-Romero, UMSNH
Abies religiosa (Sacred fir) seedlings (foreground) were planted in groups of eight seedlings under the shade of pre-existing shrubs as "nurse plants" (Senecio cinerarioides), to have the benefit of a protective shade against extreme temperatures (either warm or cold extremes), something critical under the ongoing climatic change. Each seedling planted was originated from seed collected at the MBBR, from lower elevations than the planting site. Credit: Cuauhtémoc Sáenz-Romero, UMSNH
Abies religiosa (Sacred fir) covered by Monarch butterflies at Ejido La Mesa, 3,340 m of elevation, core zone of MBBR. Seeds of Abies religiosa were collected at this site, to produce seedlings in a nursery that later were planted at Nevado de Toluca, at elevations of 3,400 m, 3,600 m, 3,800 m and 4,000 m. Credit: Cuauhtémoc Sáenz-Romero, UMSNH