Eastern migratory monarch butterfly population estimates and associated early warning signals (2006-2022)

The long decline of the eastern migratory population of monarch butterflies (Danaus plexippus) appears to have abated in recent years and the population now persists at a much-reduced abundance. Stochastic variation in abundance typical of monarch butterflies, and other insects, places this population at heightened risk of quasi-extinction, a level of abundance below which recovery of the migratory behavior is uncertain. These data and results provide insight into the near-term status and trajectory of the eastern migratory population of monarch butterflies. Within the stationarymonarchdata.csv, overwinter[ha] are annual monarch butterfly overwinter area occupied estimates as provided by World Wildlife Fund-Mexico and breedingcounts are annual indices of Illinois Butterfly Monitoring Network counts of monarch butterflies in summer.