The monarch butterfly (Danaus plexippus) population on the Mexican Monarch Reserve where they overwinter is the lowest since annual surveys began back in 1993. The oyamel fir forests provide a warm winter home for the monarchs, known for their great migration across North America. The population is down 59% from two years ago. In 1996, monarchs occupied 45 acres (18.2 ha) of forest. They now occupy 2.94 acres (1.2 ha).

Monarch butterfly wing
Photo: Rare Giants

The entire migration process takes five butterfly generations to complete one full cycle, and over the past twenty years, fewer monarchs have been surviving the cycle to have their progeny return to the reserve.

The demise of the milkweed plant, mainly due to the use of glyphosate herbicides, means the butterflies are unable to find enough of their main food source. But extreme weather, deforestation and forest degradation, and regulatory rollbacks for protected areas also contribute to the dangers facing the species’ survival.

In Barbara Kingsolver’s novel Flight Behavoior, monarch butterflies disappear from Mexico almost entirely and find a new forest home in a completely unexpected location, alighting for a season before moving on. There’s always the hope that intensified efforts to replant milkweed and to strengthen protected migratory paths will help. And maybe, prior to the annual surveys, the monarch population experienced massive contractions that went unnoticed, only to recover again.

Mexican billionaire Carlos Slim has just announced a $100 million contribution to a variety of monarch programs. If there’s message here, it’s this: If you live in North America, go out and plant some milkweed. In your garden, on your balcony, on roadsides and byways. Sign a petition. Send a letter to your congressperson.

For now, the circle of monarchs retracts, a narrowing lens by which to observe these amazing creatures of long journeys on small wings.

Close-up, monarch butterfly wing
Photo: Raul Gonzales