Monarch Butterflies Wintering in Mexico Drop to Second-Lowest Level Ever Recorded

The estimated number of monarch butterflies migrating to Mexico for winter has reached its second-lowest level ever for the 2023 to 2024 overwintering season. The estimate, based on the size of the butterflies’ hibernating forest area, has dropped by about 59% from the previous year, according to officials.

Experts are pointing to extensive heat and drought as well as climate change for the major decline.

Recent years have seen some hope for the migrating monarch butterflies, with a 35% increase in the number of butterflies observed overwintering in Mexico during the 2021 to 2022 season compared to the previous year.

But monarch butterflies face three primary threats, including habitat loss for their breeding and overwintering; the use of pesticides, which can be toxic to the butterflies or can kill their food source, milkweed; and climate change, which can shift their migratory patterns. By the 2022 to 2023 overwintering season, World Wildlife Fund reported a 22% drop in the amount of overwintering monarch butterflies in Mexico.