Why is the Eastern Monarch Butterfly disappearing?

Ecologists at Michigan State University led an international collaborative study of professional and volunteer scientists to reveal new reasons for the decline in the number of eastern monarch butterflies

From 2004 to 2018, the climate change in the breeding grounds of monarch butterflies in spring and summer had the most significant impact on their population decline

The lead author of the study, Erin Zylstra, said: “What we did was build a model to understand why the number of monarch butterflies is decreasing, and what is happening to biodiversity in general

"A lot of it is not good news

Understanding the declining number of monarch butterflies and doing everything we can to reverse this trend is not only important for protecting biodiversity, but also because insects are prolific pollinators

From the mid-1990s to the mid-2000s, the use of glyphosate herbicides fell the most.

The prevailing theory during that period was that the decline of milkweed in agricultural areas was responsible for this severe decline

However, about ten years ago, Leslie Ries of Georgetown University and Elise Zipkin, associate professor of integrated biology at Michigan State University (MSU) realized this.

"People have different assumptions," said Zipkin, senior author of the new study and director of the Ecology, Evolution and Behavior Program

The complicated life cycle of the Eastern Emperors makes it difficult for us to understand the decline in their numbers

Once there, adult penguins reproduce, lay eggs, and then die

With the support of the National Science Foundation, the team analyzed data from more than 18,000 surveys conducted in various locations in the Midwestern United States, central Mexico, and southern Canada between 1994 and 2018

"Almost all of this data is not collected by professional scientists, which is really cool," Zipkin said

Zylstra said: "The professionalism of the volunteers is really incredible

Zylstra led the development of a model based on these observations and reached meaningful conclusions

"I think everyone is partly right

Zylstra explained that each of these assumptions could cause butterflies to disappear on smaller scales
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But looking at this issue as a whole — spanning many years and across multiple countries — it is clear that since 2004, climate change has been the dominant destructive force
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Unfortunately, there are insufficient data in agricultural areas to determine what happened during the most significant period of decline from the mid-1990s to the mid-2000s
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In order to fully understand the population decline, the research team needs to understand the dynamics of many generations in many places
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So thousands of investigations are needed
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The huge effort to collect and understand this data has also paid off in two major ways
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First, by proving that the model is possible to sort out the population dynamics of complex species like the Eastern Emperor, the team is optimistic that the model can also be used to understand what drives the population changes of other species
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Secondly, this understanding should help inform that protection measures can provide the greatest benefit to the number of eastern emperors
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Zylstra said: "This study provides us with information and tells us where we should spend our limited money
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"

She said that although we can't simply eliminate climate change, we can focus on restoring milkweeds in areas that are most conducive to monarch butterfly reproduction despite warming temperatures and changing precipitation patterns, she said
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She added that even so, everything we can do to curb climate change will improve the prospects of monarch butterflies and humanity
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Although curbing climate change is a huge improvement, Zipkin pointed out that this study reminds us of the power of partnerships in addressing major challenges
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"We are talking about the three affected countries: the United States, Canada, and Mexico
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This is not something we have to do alone
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" "Partnerships are important
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Studying the reasons behind the population decline proves this point
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Among professional scientists and volunteer data collectors, residents of these three countries made this research possible
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"You need this kind of partnership
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You need people with different expertise
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We proved that this is how we know what's going on
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Now, what can we do about environmental protection?" Zipkin asked
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"We can work together
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"

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