Last of two parts
The previous part is at https://thevoice.us/research-seeks-to-stop-disappearance-of-monarchs
“Erin Zylstra, a Michigan State University (MSU) postdoctoral research associate asks:
“Why is the eastern monarch butterfly disappearing?
“A Spartan-led research team has uncovered an answer, at least for the most recent population decline, with a huge assist from volunteers.
“Michigan State University ecologists led an international research partnership of professional and volunteer scientists to reveal new insights into what’s driving the already-dwindling population of eastern monarch butterflies even lower. “The level of expertise among the volunteers is really incredible,” said Zylstra.
“An animation shows the migration and life cycle of the eastern monarch, which begins in Mexico in Winter. Then, in Spring, the butterflies migrate north into Texas to breed. The next generation of monarchs continues the migration northward over Summer. The monarchs that develop in late summer then return to Mexico over the Fall.
“Zylstra led the effort to develop a model based on these observations and draw meaningful conclusions. In particular, the team was interested in what the data said about the three leading theories behind the eastern monarch’s population decline: Milkweed habitat loss, mortality during the autumn migration and resettlement on the over-wintering grounds, and climate change’s detrimental impact on monarch breeding success.
“I think that everyone is partially right. All of these things do play some role. With monarchs, everything is nuanced, and everything is tricky,” said Zylstra. “But in recent years, as glyphosate applications have remained more stable, although still very high, there is strong evidence that population changes are driven by climate on the Spring and summer breeding grounds.”
‘Each of these hypotheses can contribute to lost butterflies at smaller scales, Zylstra explained. But looking at the problem holistically, across many years and multiple countries, makes it clear that climate change has been the dominant disruptive, force since 2004. Unfortunately, there isn’t enough data in agricultural regions to definitively determine what happened between the mid-1990s and the mid-2000s, the period of the most pronounced decline.
“Some experts estimate that the eastern monarch population size has been reduced by more than 80% since the 1990s. Credit: Liz West
To get the full picture of the population decline, the team needed to understand the dynamics of many generations in many locations. Hence the need for thousands upon thousands of surveys. The herculean effort of collecting and making sense of this data has reaped two large rewards.
“First, by proving the model’s potential to tease out population dynamics for something as complicated as the eastern monarch, the team is optimistic it can adapt the model to understand what’s driving population changes in other species, too.
“Secondly, this understanding should help inform where conservation efforts can provide the greatest benefit for the eastern monarch’s numbers.
‘“This study gives us information on where to spend our limited dollars on restoration,” Zylstra said.
“Although we can’t simply turn off climate change, we can, for example, focus on restoring milkweed in the regions that remain most conducive to monarch reproduction, despite warming temperatures and shifting precipitation patterns’, she said. That said, anything we can do to curb climate change will improve the outlook for both monarchs and humanity, she added.
“And although curbing climate change is a huge lift, Zipkin pointed out that this study reminds us of the power of partnerships to confront large challenges.
‘“We’re talking about three countries that this is directly affecting: the U.S., Canada and Mexico. It’s not something that we have to do alone,’ Zipkin said. ‘Partnerships do matter.’
“Working out what’s behind the population decline proved that. Between the professional scientists and volunteer data collectors, residents of all three countries made this study possible.
“You need those kinds of partnerships. You need people with different expertise. We showed that’s how we can figure out what’s going on with monarchs. Now, what can we do with conservation?’ Zipkin asked. ‘We can work together.”’