TAMPA, Fla. (WFLA) — While monarch butterflies have been one of the go-to examples of insect species in danger of dying out due to changes in the environment, new data shows that may not be the case. A recent study by the University of Georgia showed that even with the warnings, the population of the monarchs has stayed fairly stable for 25 years.
Specifically, the research by UGA focused on the summer populations of monarch butterfly colonies. According to the university, “the study suggests that population growth during the summer compensates for butterfly losses due to migration, winter weather and changing environmental factors.”
The head of the study, Dr. Andy Davis of the Odum School of Ecology, said that despite a “perception” that monarch butterfly populations were in “dire trouble,” that may not always be true. He said monarchs were among the largest butterfly populations on the North American continent.
Still, the study warned that the species still faces some challenges and threats.
“Best documented is habitat loss and changing climate at concentrated overwintering sites, which has apparently led to an ongoing, multi-decadal decline of those colonies,” the study said. “A second widely-touted threat is removal of milkweed from agricultural fields within the monarch’s core breeding range in the American Midwest, following widespread adoption of glyphosate-tolerant corn and soybean. Thirdly, since migration in the human-dominated world is risky, their particularly long-distance movements could expose monarchs to multiple threats along the two month journey.”
Study authors also said agricultural and residential pesticides posed a risk to the butterflies, as well as changes in temperature and rain as climate changes continue.
The U.S. Fish and Wildlife Service declared the species to be under federal protection in 2020, though the federal agency said protection was “precluded by work on higher-priority listing actions.” Adding the monarch butterfly to this status of protection was also a step toward its candidacy as a species protected under the Endangered Species Act, though the monarch butterfly has not yet received that designation.
USFWS, in 2020, noted that there were reported declines in monarch population, which is typically measured by density of occupied space.
“Over the past 20 years, scientists have noted declines in North American monarchs overwintering in Mexico and California where these butterflies cluster,” USFWS said in 2020. “Numbers in the larger eastern population are measured by the size of the area they occupy.”
Similarly, the UGA study noted that the method for recording population may have mixed results.
Butterfly populations were measured through a partnership with the North American Butterfly Association‘s summer citizen science counts. The datasets are created by surveying breeding locations across North America, where “spatiotemporal patterns and drivers of relative abundance of breeding, adult monarchs” are assessed across the United States and southern Canada. The NABA data is notably “broad in scope” but leave evidence of population increase and decline “ambiguous” due to different reporting of losses dependent on summer and winter seasons.
The UGA research team found that monarch abundance increased about 1.36% per year, suggesting the species was not in decline.
The “researchers compiled more than 135,000 monarch observations from the North American Butterfly Association between 1993 and 2018 to examine population patterns and possible drivers of population changes, such as precipitation and widespread use of agricultural herbicides,” UGA reported.
Davis said breeding patterns in the spring and summer may help compensate for winter declines.
“A single female can lay 500 eggs, so they’re capable of rebounding tremendously, given the right resources. What that means is that the winter colony declines are almost like a red herring,” Davis said. “They’re not really representative of the entire species’ population, and they’re kind of misleading. Even the recent increase in winter colony sizes in Mexico isn’t as important as some would like to think.”
While the monarch population appears to be in better shape, Dr. William Snyder, a study co-author, said that other species might be facing trouble instead.
“So much attention is being paid to monarchs instead, and they seem to be in pretty good shape overall. It seems like a missed opportunity,” Snyder said. “We don’t want to give the idea that insect conservation isn’t important because it is. It’s just that maybe this one particular insect isn’t in nearly as much trouble as we thought.”