October wind crosses the world. The last tattered Monarch butterflies of the season sip nectar from ragged vermilion Tithonia flowers at the base of the farm. Practice period began a few weeks ago, the harvest gathered, the fields almost empty. At nightfall, exhausted Monarchs ride the updraft to shelter at the crown of the dark cypress windbreak nearest to the ocean, in trees that mark the edge of raw and cultivated ground.
These Monarch butterflies, overwintering near Green Gulch and in 400 other distinct sites spread along the salty spine of the West Coast of North America, comprise one of the largest animal migrations on earth. This ancient butterfly passage flows in what the author, lepidopterist, and conservationist Robert Michael Pyle calls a “sky river” of migratory insects. The river courses in two distinct tributaries, one moving west from the Rocky Mountains to the continent’s coastal rim, the other surging east from the Rockies as far north as Canada and fanning wide to encompass the central, eastern, and southern United States. Over this vast landscape, innumerable Monarch butterflies flow southward in an annual autumnal pilgrimage that ends in the steep Transverse Neovolcanic Range of Central Mexico. There, in the remote mountains of Michoacán, a place discovered by modern scientists only in 1976, millions upon millions of Monarch butterflies overwinter.
My fascination with Monarch butterflies began more than twelve years ago, a few months before my parents died. In collaboration with Mia, a close dharma sister who works three miles north of Green Gulch as a park ranger at Muir Woods National Monument, I began to garden for Monarchs. Mia had been protecting this butterfly, her longtime animal totem, for years. She helped me notice the battered and hungry butterflies arriving on the coast each autumn. Although she is a wildland woman, we began to hunt and gather together for the benefit of the Monarchs, Mia collecting native milkweed and even protecting the weedy invasive teasel plants that colonized our lower farm, serving as a choice nectar plant for hungry butterflies. I worked next to her with a SWAT team of Zen students, clearing 100-foot-long friendship rows between purple cabbage and Swiss chard, planting nectar and pollen-rich lines of Michelmas asters and Mexican sunflowers. Engaging with the dark orange and black–patterned Monarchs, we interspersed production lines of Zen vegetables with lush islands of milkweed plants, the primary larval food source of Monarch caterpillars. All members of the Asclepias milkweed tribe contain cardiac glycosides, a latex-rich sap that renders the Monarch butterfly family toxic to predators.
Protected by their noxious milkweed host plants, Eastern Monarch butterflies migrate close to 3,000 miles a year to reach their overwintering site hidden in the oyamel fir forests of Michoacán. Navigating with an internal, timecompensated solar compass, the Monarchs migrate south at a speed of about twelve miles per hour, pausing to rest at night before continuing. The sky river flows with individual migrants, although the butterflies arrive in a floodtide cresting in Central Mexico around November 1st and 2nd, coinciding with the annual celebration of the Day of the Dead. The return of the Monarchs to central Mexico is greeted with reverence by local citizens, who believe the butterflies to be the souls of the departed, especially the souls of children returning briefly to the world of the living. Paper Monarch butterflies festoon altars at the overwintering site alongside sugar skulls and thick ropes of bright orange marigolds. The migrating generation of Monarchs settles in the forest, draping the oyamel trees with a heavy rust-colored cloak of insects held in suspended animation. These butterflies remain on the trees for four months until they stir to life with the rising warmth of spring. The return migration north is marked by a reproductive frenzy and the desperate search of northbound female Monarchs for milkweed plants where they can lay their eggs. The life of these returning insects is short. The next year’s migration will be the task of their offspring. When the ancient sky river rolls south in seven months, it will flow with the fifth generation of fresh Monarch progeny.
Some years ago Mia made a pilgrimage to the Mexican overwintering site at El Rosario in the highlands of Michoacán. She sat still as a Zen stone at the roots of the oyamel fir trees, shivering in the cool mountain fastness at 9,000 feet while the tired Monarchs came to roost in their primitive trees. She reported a network of butterfly colonies that covered more than 20 acres, a silent refuge for 120 million migrant Monarchs in 2001. Yet just a year later, in January of 2002, a violent winter snowstorm ravaged this mountain forest, decimating more than 70 percent of the Monarch butterflies in the El Rosario region.
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