Today is a sad day. Across 261 overwintering sites, volunteers counted only 1,914 monarch butterflies for the Western monarch population of California.
How does this year compare to previous years? When the Western Monarch Thanksgiving Count was started in 1997, over 1.2 million monarchs were counted at over 101 sites. In 2018 and 2019, the population of Western monarchs was around 30,000 monarchs, which researchers posited as the extinction threshold.
Was climate change responsible? The warming planet expedited the butterfly declines across the West making food shortages much more extreme.
The warming planet is responsible for dry vegetation, which is the catalyst for this year’s wildfires. The devastating wildfires consumed butterfly habitat across the West. According to University of California-Davis ecologist Arthur Shapiro, who has researched the largest butterfly database in North America, Solano County habitat is completely gone. It will take at least three to five years for the habitat to recover. In the High North Coast Range, a million acres have burned, mainly in the Mendocino National Forest, home to numerous rare plants that host butterflies.
Why is tropical milkweed discouraged? One of the drawbacks in the West, is the introduction of tropical milkweed. It usually does not die back in the winter like most native milkweeds. The milkweed can disrupt migration and encourage breeding during months when monarchs should be in reproductive diapause at their overwintering grounds. Reproductive diapause allows migrating monarchs to delay their reproduction, which extends their life for a number of months until they return to their northward migration.
The persistence of year-round milkweed allows the protozoan parasite known as Ophryocystis elektroscirrha (OE) to build up on the plants and increase the spread to monarch offspring that eat those plants. In contrast, native milkweeds that die back are able to “cleanse themselves” of the OE spores that build up on their leaves.
Why don’t monarchs have state and federal legal protection? Recently, the U.S. Fish and Wildlife Service announced that monarch butterflies are “warranted but precluded” from listing under the federal Endangered Species Act. That means that monarchs are to be re-evaluated for listing once a year for federal protection. The state has not offered protection under the California Endangered Species Act for terrestrial invertebrates (including insect pollinators such as the monarch and bumblebee).
Who is to blame? The main problem is loss of overwintering, breeding, and migratory habitat in California. Climate change and the wildfires remain. For the time being, the pesticide use will remain. Farmers and ranchers need to learn to restore and manage pollinator habitat on working landscapes and work with managers of roadsides, energy infrastructure, forests, and grasslands to enhance current habitat and create new habitat.
What can you do to help? Share knowledge to create habitat and educate the community about monarchs and pollinators. Help researchers better understand these trends. Report findings of citizen science to community science projects like Western Monarch Milkweed Mapper or Journey North. If you are able to document this behavior of monarch larva at the same site(s) on a weekly basis, we strongly encourage getting involved in the Monarch Larva Monitoring Project to keep a more detailed account of your observations.
The e-mail photo is by Candy Sarikonda