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Western Monarch Population Remains Critically Low

Jan 23, 2020


  • Population Trends

Article based on an original press release and blog by the Xerces Society.

The 2019 Western Monarch Thanksgiving Count revealed a critically low California overwintering population (released today by the Xerces Society), almost identical to last year’s population which fell to the lowest level ever recorded. Thanksgiving Count volunteers documented only 29,418 butterflies, less than 1% of the population observed in the 1980s. Xerces writes, “While it is encouraging that the population did not shrink any further, the number of overwintering monarchs in California continues to hover just below 30,000 monarchs—the minimum threshold estimate below which the population may collapse.” Several factors continue to impact the decline of the western population, in both the breeding and overwintering areas of the West.

We Need Your Help

Now, more than ever, we need immediate action to avoid collapse of the western monarch migration. In addition to creating and protecting native milkweed and nectar plant habitats, it is essential that we protect California overwintering sites, which currently lack legal protection. Learn more about how you can help by reading the Western Monarch Call to Action, an action plan developed by Xerces and monarch scientists to rescue the western population of the monarch butterfly.

The Top 5 Immediate Actions to Save Western Monarchs

  1. 1. Protect and manage California overwintering sites to ensure that monarchs have shelter and a place to return to next fall. Xerces reports that “in the last four years alone, at least 21 overwintering sites—including both publicly and privately owned sites—have been destroyed or severely damaged by activities including inappropriate tree cutting, utility cutting, and development. At least four more sites are currently threatened by development and a large number of sites are in desperate need of restoration attention.”
  2. 2. Restore breeding and migratory habitat in California. Monarchs need nectar to fuel their flight and early-season milkweeds on which to lay their eggs when they leave overwintering sites. Plant early blooming native flowers and milkweed to restore breeding and migration habitat. Replace tropical milkweed with native species to prevent disease transmission and winter breeding. Lastly, talk to your local nurseries and seed companies about increasing the production and availability of native milkweed and nectar plant seeds.
  3. 3. Protect monarchs and their habitat from pesticides so that monarchs have clean spaces to feed and breed. Use chemical-free methods when maintaining your garden or landscaping. When purchasing plants or seeds, make sure they are not treated with neonicotinoids, and ask local growers to suspend use.
  4. 4. Protect and restore breeding and migration habitat outside of California, especially in areas that are suitable for monarchs or those that have are lacking habitat. Keep in mind the native range of milkweeds when restoring habitat. Xerces reports that the Columbia Plateau, Snake River Plain, and riparian areas are of highest restoration priority outside of California.
  5. 5. Help answer key research questions about how to best aid western monarch recovery by sharing observations of monarchs and milkweeds. Californians and Arizonans can help us learn about monarchs during this critical time by contributing data in February-April when they are leaving overwintering sites. People in other states can help look for monarchs and report sightings to the Western Monarch Milkweed Mapper.

Every single person has a role to play in monarch conservation. The five actions outlined above not only help monarchs; they help us conserve insect diversity, pollinators, birds, and wildlife that rely on the same habitat. No matter how much land you own or manage, you can contribute by adding native plants to gardens, roadsides, or agricultural margins and continuing to manage those habitats with monarchs in mind. Encourage and advocate for these practices and ask local governments to protect overwintering sites.

The Monarch Joint Venture is a national partnership of federal and state agencies, non-governmental organizations, businesses and academic programs working together to conserve the monarch butterfly migration. The content in this article does not necessarily reflect the positions of all Monarch Joint Venture partners. Header photo by Wendy Caldwell.