The playful charm that butterflies radiate as they flit about from colorful asters to goldenrods to milkweed is undeniable. Of the 750 butterfly species in the United States, the monarch (Danaus plexippus)—with its brilliant orange-red wings with black veins and white spots along the edges—may be the most iconic and easily recognizable.
But more than just a pretty creature to observe, the monarch butterfly is one of our most important pollinators. Because of this, the monarch butterfly migration provides an invaluable service and is absolutely essential for ecosystems to thrive. It is thanks to the monarchs (as well as other butterflies and bees), that we have many of the flowers and dietary staples that we enjoy, such as squash and blueberries.
Eastern Monarch Butterflies: Species in Decline
While we have seen the monarch populations rise and fall slightly year after year, the Eastern population of the North American monarch butterfly (those that breed east of the Rocky Mountains) has unfortunately been in a steady decline, on average, over the last two decades.
Butterfly populations can be estimated where they winter, and in the case of the monarch, they always return to a specific part of Mexico’s Central Highlands. Every year for the past 17 years, World Wildlife Fund-Mexico, in coordination with local communities and partners, assesses the population of monarchs in the Monarch Butterfly Biosphere Reserve. Since it would be impossible to count every individual butterfly to determine the population, the team instead measures the amount of forest area that the monarchs inhabit during their time there, providing an indicator of their population status.
Approximately 45 acres of dense fir forest in the monarch’s region in Mexico were covered with the lovely creatures in the winter of 1995–96, but during the 2003–04 season, scientists recorded only 27.5 acres of forest coverage. Since then, scientists have documented a continued downward average trend. According to the latest information, the monarch’s forest presence in the winter of 2020 occupied just over 5 acres—a massive 26% decrease from the previous year.
The disappearance of large areas of native plant habitats is a major contributor to the decline of pollinator populations worldwide, as is climate change. For monarchs, if temperatures get too warm during spring, they migrate farther north than before. Then when winter comes, they end up with an unexpectedly longer trip back to Mexico. This overburdens them and can greatly decrease their reproduction. The increased use of herbicides and pesticides and a reduction of milkweed— Asclepias, the only plant in which the monarchs lay their eggs—also adds to the perfect storm for these hard-working creatures.
Could the Monarch Migration Aid Conservation?
The monarchs’ migration has more to offer us than pollination. Their unique migration inspires interest in the natural world across the entire continent. These tiny insects weigh no more than a paper clip, yet play their role in a mind-boggling two-way migration that their great-great-grandchildren will have to finish for them. The last generation of monarchs born in the U.S. and Canada is the migratory generation known as “Methuselah.” These monarchs delay their sexual maturity in order to be able to undertake the long journey of fall migration down to their overwintering grounds in Mexico—a place these individuals have never seen. In fact, this final Methuselah generation of Monarchs often lives up to seven or eight months out of necessity (most generations live only four to five weeks on average). These monarchs know the correct path to migrate even though they themselves have never migrated before. They are guided by an internal GPS, and this mysterious navigation method is one of the many characteristics that makes monarchs such a compelling species.
The adventure from the U.S. and Canada to Central Mexico completes the monarchs’ annual life cycle. Once migration north begins, monarchs sexually mature, mate and lay eggs on their exclusive caterpillar host plant, milkweed. After laying eggs as their last hurrah, the adults die, and their offspring continue the migration north at a rate of about 100 miles per day. It usually takes three to five generations of monarch butterflies to finish the annual migration and repopulate the eastern United States and southern Canada.
Monarch butterflies hold important cultural meaning within Mexican culture. To the indigenous Purépecha communities living in the Central Highlands, the annual return of these butterflies signaled it was time to harvest their corn crops. Monarchs were referred to as Parákata, or “harvester butterfly.” The Purépecha also believed that the monarchs arriving each year were the souls of their ancestors returning, and this belief still influences modern Mexican celebrations like Día de los Muertos. The monarchs return to Mexico consistently around November 1 each year, their arrival announced in the forests by an audible beating of millions of butterfly wings. On November 1, many Mexican families celebrate Día de los Inocentes, a day to honor children who have passed, and on November 2, families celebrate Día de los Muertos to welcome the souls of their deceased family members and support their transition to the afterlife. Many indigenous groups believe that after passing on, souls live through nature and the environment—which says a lot about how much they appreciate nature. Imagine the deep cultural and psychological impact if the butterflies just didn’t appear one year.
Mexican butterfly conservationist Carlos Gottfried famously said, “When you stand in a monarch sanctuary, your soul is shaken and your life is changed.” If you’ve ever seen a monarch caterpillar pupate or an adult emerge from its chrysalis, you know how exciting that can be. But the chance to see those bright orange wings resting on every inch of every branch of every tree in a densely packed forest is to be a privileged, reverent witness to one of the world’s most astounding wildlife events. The trunks and branches start to look like they are quivering, then as the sun comes out to warm them, hundreds of thousands of monarch butterflies take to the contrasting bright blue sky, often landing on the hats and shoulders of wondrous visitors. The air actually hums with their movement. No matter how serious the traveler or scientist, it is difficult not to be instantly transported to a childlike state of joy, pledging to protect these magical creatures at all costs.
During our Nat Hab expedition to the Central Highlands of Mexico, we not only experience this magical event for ourselves, but we also learn about efforts to preserve this fragile forest ecosystem that is the key to the monarchs’ survival. We learn about what WWF-Mexico is doing in conjunction with local communities to protect the butterflies’ habitat. Planning a visit to the Monarch Butterfly Biosphere Reserve is one way to help, as this is a clear and direct example for the local people that ecotourism can be a viable and sustainable source of economic sustenance—even more so than logging.
There are other ways to support the monarchs as well. Even if you only have a tiny yard, planting zinnias, cosmos, lilacs, butterfly bush, goldenrod and of course milkweed can greatly support tired migrating monarchs. But most of these plants don’t flower until summer, and the baby butterflies that start to make their way north in the spring need all the help they can get. Spider milkweed is an early milkweed variety and can be of much assistance to the new voyagers. Common chives, Siberian wallflower and May Night salvia are also early-blooming plants that butterfly lovers should consider planting. Together, we can help support these magnificent, mysterious creatures.