A story published by the Florida Museum of Natural History about a 37-year survey of monarch populations in North Central Florida shows that caterpillars and butterflies have been declining since 1985 and have dropped by 80 percent since 2005. The article was included on the Associated Press wire service, reaching an estimated 173.6 million people, and the United Nations Secretariat of the Convention on Biodiversity tweeted about the story.
William R. Kenan Professor of Biology Emeritus and Lecturer in Biology Ernest Williams, a co-author of the original research article on which this story was based, was quoted about the findings. The research was published online in the Journal of Natural History in September.
The story pointed to shrinking native milkweed populations and increased use of the herbicide glyphosate in the Midwest as key factors in the monarch’s decline. Glyphosate is used in agriculture to eliminate weeds, including milkweed, the monarch’s host plant.
Williams commented on the widespread use of glyphosate-resistant corn and soybean products in the U.S. “What’s really needed are patches of native vegetation and nectar sources without pesticides. It’s not just for monarchs but all pollinators,” he said.
He also noted the importance of long-term studies – such as this one, which spanned more than 140 generations of monarchs – in identifying trends. “Before 2005, there was more fluctuation in the data. Since 2005, the rate of decline has been steady,” Williams said.