The size of the overwintering population of Eastern monarch butterflies was just released on Feb 25, and the number shows yet another decline (to a total of 2.1 hectares/ 5.2 acres; details are shown in the figure below). What does this mean for the Adirondacks this coming summer? Monarchs were abundant in the Adirondack region in 2018, just as they had been decades ago, but 2021 will be a year of many fewer, just as it was in 2020 and most recent years.
Monarchs are in decline because of multiple threats throughout their life cycle: the loss of milkweed because of industrialized agriculture in their main midwestern breeding area; logging of the overwintering forests in Mexico; drought and loss of nectar sources due to climate change; and increasing severity of killing storms.
Recently the US Fish & Wildlife service declared monarchs to be “warranted but precluded” for listing under the Endangered Species Act. That decision is well explained at: https://monarchjointventure.org/blog/faqs-endangered-species-act-listing-decision-for-monarch-butterflies. It means that the federal government will take no actions for the time being to reverse this decline even though the current figure of 2.1 hectares is much below the estimated number of 6 hectares required to sustain monarch migration.