It’s hard out there for butterflies, especially in certain parts of the U.S.
An analysis of three decades worth of data released this week in the Proceedings of the National Academy of Sciences journal revealed that not one of 136 butterfly species tracked had a population increase in the Midwest during that time. Researchers were sure that at least one of the species would have increased over the past 32 years, said Wendy Leuenberger, a Michigan State University PhD candidate.
Leuenberger of the MSU Zipkin Quantitative Ecology Lab in the department of integrative biology and her colleagues went through more than 4 million observations in the Midwest from 1992 through 2023. They found that declines were observed for 59 of those 136 species. Numbers of both common and rare butterflies waned over the timeframe.
That means that a walk to look at butterflies would have looked very different in 1992 than it does today, Leuenberger explained.
“While most of the common species like monarchs and cabbage whites are still present, you wouldn’t see nearly as many of them as in 1992,” she said. “You’re less likely to spot rare species as well. These are all changes that have occurred during my lifetime, which is humbling.”
Elise Zipkin, Red Cedar Distinguished Professor, director of MSU’s Ecology, Evolution, and Behavior Program and senior author of the study, said the Midwest has the highest density of butterfly surveys in North America. There are more than 2,000 species of butterflies and moths in Illinois alone, according to the Illinois Department of Natural Resources.
“Volunteer scientists use the same protocols week after week and year after year,” Zipkin said of the Midwest surveys. “Without their invaluable efforts, we would not know how butterflies are faring and what we can do to reverse declines.”
According to Michigan State University, butterflies are the most commonly counted insects. Therefore, they can often help us understand what sort of population trends other insects might be experiencing.
“As caterpillars, butterflies are the primary food for many fledgling birds,” MSU said. “Butterflies and other insects are also important pollinators for plants and crops.”
Beyond the analysis published this week, the university noted that another data analysis published in March in the Science journal documented a national butterfly decline across the U.S. from 2000 to 2020. With this more recent study, we can see declines going back even further.
“Although the team did not evaluate the drivers of decline, the time frame is parallel to the widespread use of the insecticide class of neonicotinoids, which were introduced in 1994 and rapidly increased in use after 2003,” MSU added. “The last several decades have also seen changes in key weather variables because of global climate change.”
Per MSU, detailed analysis regarding different species is important to develop conservation plans. For example, some butterflies migrate long distances, while others tend to stay put.
“Traits affect how resilient butterflies are to change,” Leuenberger said. “For instance, ones that only have a single generation a year don’t do as well as multi-generational butterflies.”
Last month, Audacy also covered research into a history-making recent honey bee die-off. A study released by the U.S. Department of Agriculture found that mites, viruses and insecticide resistance all played a role in the loss of 62% of commercial honey bees in the U.S. from last June through this January, and until a new insecticide or something to attack the viruses is created, honey bees are still at risk.
“Humans rely on insects more than we realize,” said Leuenberger. “We need to figure out how we can protect them before it’s too late.”