Monarch butterfly (Danaus plexippus plexippus) populations across the continent have dropped precipitously over the last 30 years, especially those found west of the Rocky Mountains. In 2018 and 2019, it was estimated that less than 30,000 individuals make up the western population of monarchs, representing the lowest estimates on record and less than one percent of 1980s-1990s population levels. An analysis of annual and seasonal data from 1980-2017 showed monarch butterflies overwintering in coastal California have declined more quickly than monarch overwintering in Mexico, and declines were most strongly associated with losses and degradation of overwintering habitat. To inform restoration of the overwintering sites, managers need [...]
