Fall has arrived and with anticipation we are waiting for the arrival of the western monarch butterfly to their overwintering grounds along the Pacific Coast, typically beginning in September and lasting through February.

In Marin, monarchs historically have overwintered at locations in Bolinas, Muir Beach, Stinson Beach to name a few. During these overwintering months, the butterflies will cluster together in groves and feed on nectar plants that bloom late fall through winter to build up fat storage to survive. In February, the butterflies will leave overwintering grounds and return inland to find milkweed, which they depend on for mating, to continue the next generation of butterflies.

Unfortunately, the butterflies are in crisis. In the 1980s, it is estimated that there were 4.5 million butterflies counted at overwintering locations along the Pacific Coast. Last year, volunteers counted only 2,000 butterflies along the Pacific Coast. This is a drop of more than 99 percent in the population.

There are many factors contributing to the dramatic decline in monarch butterflies including habitat loss, use of pesticides and toxic chemicals, disease and parasites, and changing conditions related to the climate crisis.

Additionally, well-intentioned individuals can harm monarch butterflies by planting non-native milkweed, like tropical milkweed, that continues to bloom all year and confuses monarchs’ reproductive cycle. Monarchs and milkweed have an important relationship, however, one cannot rely only on planting milkweed to save monarchs. Depending on where you live, milkweed may not be the answer.

EAC’s Marin’s Monarch Report highlights key actions individuals can take to help the monarch butterfly:

If you live along the coast (within 5 miles of the ocean): Do not plant milkweed. Instead, plant native pollinator plants so that your garden will nurture the monarchs during the winter months building their fat stores and increasing their chance of survival. Work to protect rich and dynamic overwintering tree covers in your neighborhood.
If you live in inland areas of Marin: Plant native narrow-leaf milkweed or showy milkweed. If you have tropical milkweed in your garden, now is the time to cut it back for the fall or take it out and find a trade-in-program to get native milkweed. Before you take any action to cut back or remove milkweed, check for eggs and caterpillars first and wait.
Do not use herbicides or pesticides in your garden! These have negative impacts on the health of the butterfly and other important pollinator species.
Report Monarch Sightings on iNaturalist or Monarch & Milkweed Mapper.

The monarch butterfly is a sentinel of the biodiversity crisis we face due to the profound impacts people have on species through habitat depletion and pollution. We must act and mobilize to help the monarch . In the coming months we will begin to receive the reports of butterfly sightings in coastal Marin!

Learn More:
EAC’s Website
Download Marin’s Monarch Movement Report
Access our Online Library of Resources