With its striking orange and black coloring and transcontinental range, the monarch butterfly is probably the most recognizable insect in North America. All pollinators are important to maintaining our food supply, but monarchs also have a key role in education; for decades schoolchildren across North America have been raising and releasing monarchs as part of their science lessons. Unfortunately, while monarchs were once one of the most commonly seen pollinators in gardens and fields, in the past decade there has been a precipitous drop in the monarch population. Just last week the World Wildlife Fund, in conjunction with the Monarch Butterfly Biosphere Reserve in Mexico, released the latest monarch population estimate– a number that was the second lowest on record for the population.
The annual estimates of the monarch population are taken at the monarch’s overwintering site in central Mexico. Most of the monarchs in North America live east of the Rocky Mountains, and each fall they migrate thousands of miles south to their overwintering location in Mexico, where they cluster together on oyamel fir trees. In the spring those same monarchs fly north, where they produce new generations that spread throughout the United States and Canada. Their vast summer range can make it difficult to get precise estimates of the population size, but in winter the monarchs are bunched tightly together, making population estimates more feasible. Instead of counting individual monarchs, scientists record the amount of land that the overwintering monarch population covers.
This year, the monarchs covered 1.13 hectares; that’s a little more than two football fields’ worth of land. That might sound like a staggeringly small size, but it’s actually a 69 percent increase over last year’s population, which was the smallest on record (see graph). This increase offers some hope to counterbalance the fact that the current population size is the second smallest on record, but there is still much concern about the monarch. In fact, the US Fish & Wildlife Service is currently evaluating the monarch for listing as Threatened under the Endangered Species Act.
A listing would provide the monarch with legal protections, but a decision is not expected for at least a year, and in the meantime, there are many things that the public can do right now to help monarchs!