Monarch Population Data
Community scientists began monitoring the abundance of monarch butterflies at overwintering sites in California in the 1980s, but the concerted effort of the Thanksgiving Count didn't begin until 1997. As can be seen in graphs 2 and 3, both the western and eastern monarch butterfly populations have been significantly declining. As populations become smaller, “ordinary” environmental variation can cause a population to drop below a point from which extinction is inevitable, unless extraordinary measures are taken. We call this point the quasi-extinction threshold. “In 2016, a group of experts proposed 30,000 butterflies as the quasi-extinction threshold for western monarchs. Current trends indicate an extinction risk of 72% in 20 years and 86% in 50 years (Schultz et al., 2017)”. By the mid-2010s the population has declined by about 97%. Then in the winter of 2018-2019 the population declined to only 30,000, which was an 86% drop from the prior year. These numbers are very alarming because they indicate a greater than 99% decrease in the monarch population from the 1980s and the monarch population has reached the quasi-extinction threshold. The monarch is up for reevaluation to be put on the endangered species list in 2024. Drastic action needs to be taken soon to prevent the western monarch from going extinct.
Schultz, C. B., Brown, L. M., Pelton, E., and Crone, E. E. (2017). Citizen science monitoring demonstrates dramatic declines of monarch butterflies in western North America. Biol. Conserv. 214, 343–346. doi: 10.1016/j.biocon.2017.08.019
Schultz, C. B., Brown, L. M., Pelton, E., and Crone, E. E. (2017). Citizen science monitoring demonstrates dramatic declines of monarch butterflies in western North America. Biol. Conserv. 214, 343–346. doi: 10.1016/j.biocon.2017.08.019