The U.S. Fish and Wildlife Service has agreed to decide by June 30, 2019, whether to list the monarch butterfly under the Endangered Species Act. The agreement is part of a settlement of a lawsuit by the Center for Biological Diversity and Center for Food Safety that sought to obtain a legally binding deadline for the listing decision. Under the settlement agreement, the agency must propose protection for the monarch, deny protection or assign it to the “candidate” waiting list for protection by the June 2019 deadline.
Long-term declines in the overwintering Eastern population of monarch butterflies are significantly increasing the probability that they may become extinct over the next twenty years according to U.S. Geological Survey and Scripps Institution of Oceanography research published earlier this year. The USGS Study, published in the journal Scientific Reports, found that the Eastern migratory monarch population declined by 84 percent between 1997 and 2015. Based on this information, the study indicated there is a substantial probability – between 11 and 57 percent – of “quasi-extinction” of the species over the next two decades. A quasi-extinct population is one with so few remaining individuals that recovery is effectively impossible — while the remaining numbers may survive for a short time, the population as a whole will inevitably become extinct.
The monarch’s long, multi-generational journey between central Mexico and the summer breeding grounds in the U.S. and southern Canada is celebrated in all three countries, but gives rise to shared management responsibilities. Previously published research indicates that the most effective way to increase monarch butterfly numbers is to focus on the restoration of their breeding habitat in the northern U.S. and southern Canada. The recent population declines have been primarily attributed to the loss of breeding habitat, particularly in the United States. Monarchs depend on several species of milkweed to provide food for developing larvae. Milkweed abundance has declined significantly as a result of a combination of herbicide use, climate change, insecticides (including neonicotinoids) and other factors.