The International Union for the Conservation of Nature added the migrating monarch butterfly for the first time to its “red list” of threatened species on Thursday and categorized it as “endangered.” University of Michigan experts are available to comment.

Mark Hunter is the Earl E. Werner Distinguished University Professor of Ecology and Evolutionary Biology. He is a leader in understanding how insect and plant populations respond to environmental change, and has studied monarch butterflies and their milkweed host plants for over two decades.

“The decision by IUCN to add migrating monarch butterflies to their ‘red list’ of endangered species is an important step forward in protecting this iconic butterfly species,” he said. “At the University of Michigan Biological Station, we have measured precipitous declines in monarch populations over the past couple of decades. Like many migratory species, monarchs are exposed to multiple environmental threats as they make their journey between the United States and Mexico. Habitat loss, climate change and disease transmission all impact migrating monarchs as they make their spectacular journey.

“Because monarchs are so well studied, they can serve as a ‘canary in the coal mine’ for other endangered species. For example, fully 50% of the other insect species that eat milkweeds have also declined in northern Michigan. We need sustained conservation efforts if we are to protect monarch butterflies and the other insects with which they live.”

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Delbert A. Green II, assistant professor of ecology and evolutionary biology, studies the environmental and genetic basis of monarch butterfly migration and how migration has evolved. 

“The ‘endangered’ designation by the IUCN actually moves a few steps beyond the 2020 U.S. Fish and Wildlife Service determination that listing monarchs as a ‘threatened’ species is warranted, but not of highest priority,” he said. “The IUCN listing will further elevate the profile of monarchs as one of our most important vehicles for promoting conservation awareness among the public. It may do so, however, at the risk of oversimplifying a complex, growing body of research that seeks to explain how monarchs make their migration and why their populations have been changing.

“We need to better understand how different factors—such as habitat loss, climate change, and disease-–threaten their spectacular journey and the ability to study monarchs and interact with them in their natural habitats will help us do this. Indeed, what is most critical for effective preservation of this iconic phenomenon are strong partnerships between conservation practitioners, academic researchers, and the public to learn more about how monarch migration works, to nurture a new generation of environmental stewards, and to push forward timely conservation initiatives.”

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