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Butterfly effect: Monarchs are making a huge comeback

Scientists have noticed a resurgence of the majestic species after population numbers sank to worrying lows in recent years, and now they think they have an idea to explain why the butterflies are thriving again.
By Allison Finch, AccuWeather staff writer
Published Jun. 2, 2022 6:31 AM EDT | Updated Jun. 2, 2022 6:31 AM EDT

According to a report from Journey North, a science program organized by the University of Wisconsin-Arboretum, much of the habitat these butterflies rely on was lost early in the 21st century. These great migrators arrive in Mexico's oyamel fir forest, which is just west of Mexico City, in late October to early November to spend the winter.

During the winter months, the trees in this forest provide the monarchs with a "blanket and umbrella," protecting them from extremely cold temperatures and precipitation, according to the Monarch Joint Venture, a nonprofit organization working to conserve monarch butterflies and other pollinators. Since the temperature in the forest doesn't drop too low or get too high, the butterflies are able to conserve their lipid reserves, slowing down their metabolism, thus making them burn less energy.

In February of 2021, the butterflies began heading north about a month early, fortuitously escaping an April heat wave, which brought triple digits to parts of Southern California and mid-summerlike temperatures to much of the southwestern U.S.

Experts think the increased amount of wintering butterflies that were measured in Mexico this past December was a direct result of their early migration in 2021.

This year, the butterflies' pattern was different. They left almost a whole month later than normal.

"They left very late. We still had butterflies in April," Gloria Tavera, the regional director of Mexico's Commission for National Protected Areas, told The Associated Press.

Tavera and other experts are curious to see next year's numbers to see whether this late start in their migration was a good strategy or not.

Saw some in my yard this spring much earlier than in previous years.

There is also a coalition here in Iowa where the Monarchs summer that has been extremely active in planting milkweed and enhancing habitat. They have provided milkweed seed balls that are handed out to bicycle riders to toss along the roadways where the RAGBRAI (an annual bike ride across this state) crosses the state. Butterfly counts in these areas have increased considerably. The Monarchs from here winter in Mexico.

About 6 years ago, while wintering in San Miguel, we drove down to the Mexican state of Michoacan to witness the winter range of the Monarchs. They migrate up to 2,800 miles from Canada and the Northern US. We climbed to 11,000 feet to witness millions of butterflies covering the pine trees. Pictures do not show the concentration of orange wings.