The monarch butterfly population dropped by 27 percent in the last 12 months, probably because of late-winter storms last year year.
A study released today by government and independent experts wintering in Mexico cited the loss of more than 100 acres of forests where migrating butterflies spend winter in central Mexico.
This is a reversal of last year’s recovery from what were historically low numbers.
Millions of monarchs make the 3,400-mile migration from the United States and Canada each year.
“The reduction in the area of forest they occupied this year is most probably due to the high mortality caused by storms and cold weather last year,” Omar Vidal, the head of the Mexico office of the World Wildlife Fund, told the Associated Press. “It is a clear reminder for the three countries that they must step up actions to protect breeding, feeding and migratory habitat.”
7.4 percent killed
Storms in March 2016 killed an estimated 6.2 million butterflies, almost 7.4 percent of the estimated 84 million that wintered in Mexico, said Alejandro Del Mazo, Mexico’s commissioner for protected areas. The monarchs were preparing to fly back to the U.S. and Canada when the storm hit.
The monarchs depend on finding relatively well-preserved forests, where millions hang in clumps from the boughs. The natural disaster is all the more ironic considering the progress made in Illegal logging in the monarch reserve, which dropped from almost 49.4 acres in 2015 to about 29.6 acres in 2016.
The loss of milkweed in the U.S. and Canada is another factor. The plants, which constitute nutritious food for the butterflies, have been decimated by herbicides and development.