One of nature’s epic events is underway: Monarch butterflies’ fall migration. Departing from all across the United States and Canada, the butterflies travel up to 2,500 miles to cluster at the same locations in Mexico or along the Pacific Coast where their great-grandparents spent the previous winter.
Human activities have an outsized impact on monarchs’ ability to migrate yearly to these specific sites. Development, agriculture and logging have reduced monarch habitat. Climate change, drought and pesticide use also reduce the number of butterflies that complete the journey.
Since 1993, the area of forest covered by monarchs at their overwintering sites in Mexico has fallen from a peak of 45 acres in 1996-1997 to as low as 1.66 acres in the winter of 2013-2014. A 2016 study warned that monarchs were dangerously close to a predicted “point of no return.” The 2019 count of monarchs in California was the lowest ever recorded for that group. MORE
Header image: A monarch butterfly in a Toronto park on common milkweed, an important plant for its survival. Credit: Colin McConnell/Toronto Star via Getty Images.