Newswise — The anecdote Creighton University biology professor Ted Burk, Ph.D., relates about the migrating monarch butterfly of the Midwestern and Eastern United States, is the tale of the passenger pigeon, and it is an apt one.
“In America in 1850,” Burk begins, “nobody could have fathomed the extinction of the passenger pigeon.”
But by the turn of the 20th century, the massive flocks with birds totaling in the billions had vanished. Commercial harvesting of passenger pigeon meat and a loss of habitat had reduced the species to a few hundred birds. By the time the first guns of World War I were sounding in Europe, the last passenger pigeon died.
Burk doesn’t tell this story to be alarmist. It’s a fascinating tale, if a staggering one, and an exquisite illustration of an almost scientific constant: the hubris of human progress.
Since the winter of 1996-97, the monarch population that migrates to the mountains of southwestern Mexico from east of the Rocky Mountains and north of the Gulf of Mexico has experienced a 97 percent drop.
Burk chalks much of the decline up to the dawn, in the 1990s, of agricultural technologies, especially herbicide-resistant crops. Genetic modifications to corn and soybeans are able to protect crops from weed-killing chemicals, but the consequence has been a ravaging of monarch food supplies, namely milkweed, upon which monarch eggs are laid and the leaves of which are the staple of the monarch caterpillar’s diet.
“It’s been great for crop yields and everyone can understand why you’d be doing this in farm fields,” Burk said. “But nobody anticipated the collateral damage.”
Every year at this time, mid-September to early October, in what is already a tenuous prospect at best — the journey of millions of creatures, weighing less than a gram, fighting strong southern winds, rains, crossing highways and rivers on the thinnest of wings — the great-great-grandchildren of the monarchs who migrated last year begin their southern excursion. The monarchs fly solo, too, so strength in numbers on the journey, right up until they get to the forest, is a luxury they don’t have.
“I often wonder how they’re able to make it to Mexico at all,” Burk said. “You think about the odds, going alone as they do. And in our part of the world, where there are really only two kinds of weather this time of year, windy days and rainy days, it’s amazing they get there. There are usually two days when the sun’s out and the wind is less than five miles an hour, and that’s when they have to make their move. This is the fun time, though, watching as they make their way through.”
Blizzards in the mountains have had significant impacts on at least two migrations in the last 15 years, Burk said, but in the winter of 2013-14, even with decent weather, the population (estimated to be about 20 million butterflies per acre) occupied its lowest recorded area, just 0.67 hectare, or about 33 million monarchs. Last winter, there was a slight rebound, to 1.13 hectares or 56 million butterflies. Researchers said they still expect rebounds to be slighter and drops to be more dramatic.
But as more has come to light about the effect the widespread loss of milkweed and other plants mature monarchs depend upon for food, initiatives have sprung up across the country to plant milkweed and to let other plants proliferate, including tall thistle, goldenrod, ironweed, New England aster, zinnia and wild bergamot, the flowers of which supply nectar that’s a favorite food of mature monarchs.
Burk said he doesn’t think the monarchs are in danger of a collapse as dramatic as the passenger pigeon experienced. Monarch populations in Florida and on the West Coast, migrating shorter distances, are still going strong. But he said the bellwether for the U.S.-Mexico monarch migrants has been closely watched. A bad winter this year could be catastrophic.
“It’s a unique phenomenon,” Burk said of the migration. “It’s not paralleled anywhere else in nature. Monarchs don’t provide any major economic boost in our lives, they’re not the most important pollinators, though they do have a function there. More than anything, they just provide such a pleasant natural background to our lives. It would be a shame to lose that.”
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