Answer;
-illegal logging.
Explanation;
-Monarch butterfly migration is the phenomenon where the subspecies Danaus plexippus plexippus migrates each summer and autumn to and from overwintering sites on the West Coast of California or mountainous sites in Central Mexico.
-The monarch butterflies will spend their winter hibernation in Mexico and some parts of Southern California where it is warm all year long. If the monarch lives in the Eastern states it will migrate to Mexico and hibernate in oyamel fir trees.
-Illegal logging does not only bring threat to the Monarch butterflies but as well as to other animals living in that forest.