From Milkweed to Mexico: Protecting the Endangered Monarch

By Sadie Holmes

Monarchs are a ubiquitous sign of midsummer in Vermont, as they return in the thousands from their overwintering Northern Mexico. Their spectacular migration is the longest of any butterfly species – 3,000 miles on fragile wings – to fulfill a natural cycle of which we still have relatively little understanding. However, in recent years, the number of butterflies to make this journey

According to the International Union for Conservation of Nature (IUCN), eastern monarch populations have declined by as much as 72% over the last decade. They face threats including logging in Mexico and California, herbicide and pesticide use, climate change, and loss of the species they depend on: milkweed. In July 2022, monarch butterflies were officially added to the IUCN Red List of Endangered Species.

“It’s sort of a desperate situation out there in the world,” reflects Donna Bister, a lifelong Vermonter. Every summer since 2016, Donna and her husband, Marc Estrin, have made it a tradition to raise and release several “classes” of eastern monarchs from their milkweed-filled backyard in the Old North End of Burlington.

“We just started doing it because we noticed that there was a little milkweed growing beside our house. I thought…‘there should be some monarchs.’”

Donna and Marc buy butterfly eggs from a commercial butterfly farm in Pennsylvania and watch as dozens of hungry caterpillars emerge from their chrysalises and spread their damp wings.

Nationally, monarchs have been declining for decades. In an article for PBS, Scott Hoffman Black, executive director of the Xerces Society for Invertebrate Conservation, reported that there have been losses in the hundreds of millions—from over 370 million monarchs in the 1980s to an estimated 45 million in 2020. According to Black, the declines can mainly be attributed to human land use changes: the growth of industrial agriculture, increasing rates of pesticide and herbicide usage, and the sprawl of human development that continues to replace open meadows with concrete and neatly trimmed and treated lawns. The problem is of particular importance in the Corn Belt of the

Midwest, where 50% of migratory monarchs originate.

“The question among scientists is: What’s the extinction threshold for this migration?” says Elizabeth Howard, Vermont’s resident monarch migration reporter, in an article for the Burlington Free Press. “How small can that population get in Mexico where it just can’t recover?”

Although we may not have the answers to Howard’s question, the science behind the monarchs’ journey may give us hints towards how to protect them. Monarchs cycle through four or five generations each year, the last of which is equipped with key genetic differences that make them physically suited for migration. While the summer generations live for two to six weeks, the migratory generation of monarchs can live for up to nine months, and these butterflies have larger wingspans built for long-distance flight.

As the goldenrods bloom and Vermont’s maples take on the first hint of red, the migratory generation launches into a unique spiraling “flight dance.” We’re still not entirely sure how monarchs know where to go, but research points toward the use of biophysical cues, such as the sun, wind, and variation within the Earth’s magnetic field, to calibrate an ingrained magnetic compass located in the antennae. In a University of Kansas study, monarchs released in open, ambient field conditions oriented themselves with a repeated looping flight to high altitudes, where they could then establish a final migratory flight direction to the south or southwest.

Once their internal compass is on track, the continental nomads journey about 30 miles per day and have been spotted flying at altitudes higher than the Empire State Building. But a loss of nectar-supplying habitat, coupled with other threats including changes in temperature and precipitation, throws off the delicate cycle of the monarch. Humans simply aren’t factored into their biological rhythms.

The loss of monarchs, aside from a cultural and sentimental significance, has a far-reaching ripple effect. They are an important food source for avian predators such as black-headed orioles and grosbeaks, which can tolerate the levels of toxins present in adult monarchs. They are also key pollinators. Losing one pollinator is often an indicator of a larger problem as other, similar species tend to be affected by the same environmental fluctuations.

The loss of pollinators such as butterflies and bees spells out major problems for global food systems, as almost 80% of crop plants require insect pollination. As stated succinctly by the USDA Forest Service, “Without pollinators, the human race and all of earth’s terrestrial ecosystems would not survive.”

Working to protect monarchs not only serves the butterflies themselves, but indirectly protects the many other organisms that make up our planet’s ecological communities. Monarchs’ characteristic beauty and vibrant colors are widely adored, making them the perfect representative figure for butterfly advocacy. “Because people really love it, people are willing to take action to protect it,” explains Black for PBS. “And by protecting it, they’re protecting bees and other butterflies as well. So this iconic species can really help way beyond just itself.”

Despite the heavy impacts humans have on monarch populations, some actions are being taken to better support these seasonal visitors as well as other pollinating insects. A March 2022 Stateline article describes an unprecedented monarch conservation agreement across 23 state lines, from Vermont to Texas.

The Monarch Candidate Conservation Agreement with Assurances, or CCAA, asks businesses and landowners to commit to actions that will protect monarchs and their habitat, such as pest and vegetation management. The goal of the group is to preserve 2.1 million acres of pollinator habitat across the continental United States. In the two years since the agreement began, three dozen organizations have agreed to conserve a total 815,000 acres of highway and energy corridors.

In places like Burlington, Vermont, the idea of planting pollinator habitat is relatively new and spreading quickly.

“I would say fifteen years ago the city was on everybody’s case to make sure their green belts were always mowed down,” reflects Donna Bitser. “Well, our neighborhood had a big fight with them about it. And now, anything goes. We can plant anything as long as it doesn’t obstruct.”

In addition to “rewilding” lawns and green spaces, land management practices can also be altered and timed to meet both human and monarchs’ needs at different stages of the life cycle. For example, delaying agricultural mowing until September allows the migrating butterflies to safely emerge from their chrysalis and gather enough late-summer nectar to fuel the first part of their flight.

This summer, Donna and Marc released over one hundred butterflies in four generational cycles. The fourth will wing their way south this fall, following a cold front that will allow them to join millions of others in the highland forests of Michoacan, Mexico, just as their ancestors have for the last 10,000 years.

Perhaps monarch conservation is about preserving not just the butterfly, but the wonder that comes with their very existence.

“You know, every time I see one actually come out of the chrysalis, it’s kind of a magic moment,” says Donna. To her, and many others, the journey of the monarch–from tiny egg to caterpillar to world-traveling butterfly–is one well worth protecting.

Donna was also profiled by Seven Days in a great episode of Stuck In Vermont.

To be a part of monarch conservation, check out Journey North (journeynorth.org/monarchs) for an opportunity to record monarch sightings and help tell the story of migration. H