Scientists forecast the future of monarch butterflies

The American Midwest is an important summer breeding ground for eastern monarch butterflies, which – over the course of one year and four generations – migrate between central Mexico and parts of the United States and southern Canada. However, between 1996 and 2014, the eastern monarch population has declined by over 80 percent – with climate change considered the main culprit – leading the International Union for the Conservation of Nature (IUCN) to place these fascinating insects on its list of endangered species. 

Now, by using extensive data sets and established climate models, a team of researchers from Michigan State University (MSU) has forecasted which counties in the midwestern U.S. and Ontario, Canada, are most likely to offer the best breeding grounds for monarchs.

“These projections let us look at how monarch populations will change across the Midwest and say, ‘Here’s where they’ll likely do a little better, here’s where they might do a little worse,’” said study lead author Erin Zylstra, a former postdoctoral fellow in Quantitative Ecology at MSU. 

“Climate change is a huge global problem that requires nations working together to solve. When we talk about conservation, though, we tend to want to know what we can do in our local communities. If we can find the places where the impacts of climate change aren’t expected to be so bad, those could become the areas where we invest our resources.”

In their analysis, Dr. Zylstra and her colleagues took into consideration four climate change scenarios in order to forecast monarch population changes in counties throughout the summer breeding grounds, as well as on the overwintering grounds in Mexico. In each of the scenarios, the eastern monarch population is expected to decline, which is not surprising considering their current trajectory. However, identifying the local areas where populations are growing or at least remaining constant offers new hope that their decline could be slowed or even reversed.

“We’re answering scientific questions that we think are important, but we are also working with on-the-ground individuals and agencies that can use our work to implement strategic conservation,” said study senior author Elise Zipkin, an associate professor of Quantitative Ecology at MSU. “The Midwest Climate Adaptation Science Center helps us get our research directly into the hands of those people who are thinking about next steps.”

“Monarchs are special. They’re beautiful, easy to identify, widely distributed and they get people to care about conservation in general. Absolutely, with action, we can protect our planet, we can protect other migratory species, we can protect pollinators and we can protect monarchs,” she concluded.

The study is published in the journal Global Change Biology.    

By Andrei Ionescu, Earth.com Staff Writer  

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