Eastern monarch butterflies covered 35 percent more ground in the mountain forests of central Mexico this past winter than they did the year before, according to a survey from the World Wildlife Fund.
Every spring, monarchs leave their winter home in Mexico to migrate to the U.S. and Canada to breed. Four generations will be born and die before they return the following winter to huddle together in the Monarch Butterfly Biosphere Reserve northwest of Mexico City. The butterflies covered 7 acres at their wintering grounds in December 2021, up from 5 acres in 2020, and well above their all-time low of 1.6 acres in 2013.
https://e360.yale.edu/digest/after-long-decline-eastern-monarchs-show-signs-of-recovery-survey-finds