Monarchs migrating through Michigan amid conservation efforts

Alexander Sinn • Sep 10, 2018 at 1:00 PM

Monarch butterflies are flying through Michigan this month on their way to Mexico, but their decades-long decline remains a cause for concern.

Monarchs have been spotted across the Great Lakes coastlines in healthy numbers this season, according to MSU Extension educator Erwin Elsner. They have been found in thick clusters in the St. Ignace area, he said, but can be found just about anywhere.

Over the past 20 years, the eastern population has declined by more than 80 percent.

The Michigan Department of Natural Resources has hatched a plan to bring them back, by restoring milkweed and other nectar-producing plants to the region.

In the early 1990s, populations of overwintering monarchs in Mexico covered 18 or more hectares of forest. This population declined to less than 1 hectare at its lowest point, rebounding slightly this year. Deforestation and winter storms have also caused a decline in wintering habitat in Mexico, Elsner explained. 

The DNR aims to establish 1.3 billion new milkweed stems over the next 20 years to grow the wintering population to about 6 hectares, or 15 acres.

Milkweed is considered a nuisance on farmlands, Elsner explained.

“Agriculture has gotten very good at reducing milkweed,” he said. “It is a significant pest and distasteful to grazing animals.”

Another threat to the species, the invasive swallow-wort plant, was recently discovered in northern Michigan. It attracts monarchs to lay their larvae on stems on which they can’t survive.

While monarchs are not unique from other pollinators, their decline is a warning sign for the loss of habitat, according to Elsner.

“It’s hard to say what their real benefit to us is, other than they’re part of the natural world,” he said. “They’re not a major pollinator. They can’t do anything that some other insects couldn’t do.”

Of the 165 species of butterfly in Michigan, Elsner said, over half get their nectar from milkweed.

Doug Landis, an ecologist with the Michigan State University department of entomology, is part of a team of scientists researching monarchs and other pollinators. On Labor Day weekend in the Grand Traverse Bay area, he spotted a monarch fly by every 10 seconds, and other signs point to a good year for the butterflies. But the downward trend of monarchs extends decades, he explained, and one good year can’t tell researchers much about the population’s outlook. 

Honey bees and the hundreds of native species of bees in the Midwest are also dependant on milkweed and nectar-producing plants, Landis said. 

The conservation of the species also impacts humans, he added.

“All biodiversity has some value,” Landis said. “It might be cultural value, of people appreciating the beauty of monarchs. Many of the things we would like to do for monarchs are also good for other pollinators.”

Landis and other scientists are taking a closer look at the management of milkweed — the only plant on which monarch larvae can survive. Monarchs are attracted to the plant during its flowering period in June, but are otherwise not interested.

Researchers are experimenting with strategically timed mowing of milkweed, finding that milkweed chopped at a certain time of summer can expose fresh stems and draw more monarchs.

“We think, in addition to planting milkweed, in the future we’ll be asking for milkweed to be managed to make them even more productive,” Landis said.

Ottawa County Parks has in recent years begun the Lake Michigan Monarch Highway, a series of safe havens to provide food and shelter for the species. Local businesses have helped the county improve habitat at these waystations, including pulling and treating spotted knapweed, an invasive plant that threatens the dune ecosystem. 

County officials say it has been a good year for caterpillars at the waystations. 

Other efforts are ongoing across the upper Midwest to improve habitat, but individuals and land owners must also do their part, Landis said.

“It’s going to take the efforts of many stakeholders to stabilize monarch populations,” he said. “It requires conditions to be right across this migration channel.”

The peak time to see monarchs in West Michigan is late September through October. The eastern population migrates from Canada to Mexico, across 16 U.S. states from Michigan to Texas.

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