Every November, 33 million monarch butterflies migrate up to 2,800 miles to Mexico for their winter hibernation, escaping the freezing winter temperatures in the United States. For several months, they’ll take shelter in oyamel fir trees, returning to the very same tree every year.
However, in recent years, scientists have noticed the monarch population to be declining at a rapid rate. Identified relative to the number of acres they inhabit during their seasonal hibernation, monarchs have decreased from 44.5 acres in 1996 to an alarming 1.65 acres in 2013. According to research conducted in December 2012 and 2013 by the World Wildlife Fund, the monarch population has dropped by an alarming 44 percent in the last year alone.
Why are the monarchs vanishing? As their forests are cut down for illegal logging, the monarchs get wet in the tropic conditions and lose their resistance to the below freezing temperatures, according to Lincoln Brower, professor of Biology and a monarch expert at Sweet Briar College. In recent years, scientists including Brower credit an even bigger problem caused by deforestation: the loss of the monarch’s breeding habitats.
According to World Wildlife Fund, the monarchs migrate back to the United States in March and enter their spring and summer breeding areas, only to find that the milkweed plants on which they lay their eggs have been cleared by development, agriculture expansion, and the use of poisonous herbicides.
According to Peter Lehner, Executive Director of the Natural Resources Defense Council, 60 percent of milkweed has been eliminated from the ecosystem, a vast reduction in the number of host plants available for the caterpillars to develop on. Milkweed is the only food monarch caterpillars will eat.
Habitat restoration efforts are in full swing, and the ENC has joined in the effort to restore monarch populations by planting locally appropriate native milkweed. Not only are monarchs well adapted to the plant, but locally native milkweeds – Asclepias californica, Asclepias eriocarpa, and Asclepias fascicularis – become dormant and grow back at the right time — when monarchs have returned to the area. It is important to note that planting non-native milkweed is unwise, as it can disrupt migratory cycles and make monarchs more susceptible to parasites. – Allison Garrett, ENC Intern
READ this great article explaining why planting non-native tropical milkweed can be harmful to monarchs.
HERE is an article describing in more detail why the ENC promotes the use of locally native plants.