by Dan Sealy
In the 1980’s over 4.5 million monarch butterflies (Danaus plexippus plexippus) migrated from the California mountain foothills and the Central Valley to overwinter along the coast from southern Mendocino County to Baja, Mexico.
In some coastal towns monarchs hang in large clusters on pines and eucalyptus trees. Monarchs are considered occasional migratory visitors to Humboldt and much of the North Coast, visiting vegetation for nectar to fuel their pilgrimage. In 2018 and again in 2019, California surveys revealed less than 30,000 individuals or less than 1% of historic populations. Studies suggest the butterflies are at critically low levels in the western United States due to the destruction of their milkweed habitat along their migratory route as housing expands into their territory and use of pesticides and herbicides increases. Similarly, the separate population of North American monarchs east of the Rockies is crashing. In 2017 the eastern population had fallen by 27% and the following year an additional 53%. The migration of the eastern population may range over 2,000 miles from Canada to Mexico where it overwinters in forests. Those monarchs face increased loss of host plants for eggs as crops are sprayed with herbicides, increasing large winter storms caused by climate change wipe out trees and, of course, due to the expanding sprawl of development.
In 2014 The Center for Biological Diversity, the Xerces Society and Dr. Lincoln Brower petitioned for listing the monarch butterfly as Endangered. The US Fish and Wildlife Service (USFWS) is conducting the assessment and a decision is due in December of this year. In preparation for this possible listing, and to limit impacts, in March the USFWS identified owners and administrators of transportation and energy transmission corridors to partner with federal scientists and government agencies to manage those corridors better for the survival of monarchs. Better management will, in turn, help other butterflies, moths, bees and pollinators. The managers of those corridors on federal lands and on non-federal lands will change how and when they mow and treat those corridors. In the meantime, scientists, local, state and federal agencies and conservationists wait for the results of the petition to list the monarch butterfly.
There are things everyone can do to share in the protection of monarchs and other important plant pollinators.
What you Can do to Help:
- Avoid buying fruits, vegetables and grains that are transgenically modified (popularly referred to as GMO.) These plants are frequently created to withstand application of herbicide to eradicate weeds, which also eradicate milkweed and other critical pollinator host plants.
- In your garden and yard:
- When appropriate, plant milkweeds to provide food for monarch caterpillars. (Note: well-intentioned, planting of inappropriate milkweed can harm butterflies by confusing the egg-laying cycle. Check out websites below for proper milkweeds.)
- Plant flowers, ideally a diversity of native species with overlapping flowering phenologies, to provide nectar for adults.
- Eliminate or reduce use of pesticides and herbicides.
- Include other features such as trees, shrubs, and structures for shade, perching, or roosting.
- Provide shallow water sources.
- Engage in citizen science like the “Western Monarch Milkweed Mapper” https://www.monarchmilkweedmapper.org/
For a full list of suggestions, refer to the Xerces Society’s “Managing for Monarchs in the West”:
https://xerces.org/publications/guidelines/managing-for-monarchs-in-west
Elsewhere on the Xerces website, you can learn more about the incredible lifecycle of the Monarch Butterfly and other species of moths and butterflies, and how to conserve them including their “Western Monarch Call to Action”: https://xerces.org/
For an excellent reference of what plants are good hosts for butterflies and other information on California native plants, check out CalScape website:
https://calscape.org/loc-/cat-Lep/ord-popular?srchcr=sc5eab6a0303d5f
The best source of information on native plants and pollinator hosts is our own North Coast Chapter of the California Native Plant Society’s “Gardening with Natives” online brochure which includes “Common butterflies of Humboldt Bay and their host plants”: https://northcoastcnps.org/index.php/gardening/gardening-with-natives-w-brochure
The California Department of Fish and Wildlife also has a conservation plan which you can check out on its website: https://wildlife.ca.gov/Conservation/Invertebrates/Monarch-Butterfly