Monarch habitat to be restored on public lands

03/17/2021

Saving the last monarch butterflies, which fell to historically low numbers in California this winter, is the focus of a new initiative launched by Marin public land managers. The project, which received near half a million dollars from the state’s Wildlife Conservation Board last month, will restore overwintering and breeding habitat.

The species is in crisis. Declines for the eastern population—which fly east of the Rocky Mountains and spend the winter in Mexico—are 70 percent below normal, while the western population—which stays on California’s coast in the winter—is all but lost. Statewide, 2,000 monarchs were counted over Thanksgiving, and just half survived. In Marin, the citizen science project that dates back 1997 found 200 butterflies this winter, compared to a record 38,700 in 2015. Most were seen in Bolinas. 

The decimation of the species is attributed to climate change, pesticide use and habitat degradation. Late last year, the United States Fish and Wildlife Service considered listing monarchs as endangered but instead chose to prioritize other species on the brink. Agencies in Marin are taking action. 

“The monarchs are a species that boom and then bust, with years when they are common and years where their numbers are smaller—so figuring out that what we are looking at is in fact a collapse would not be possible without our long-term dataset and monitoring effort,” said Janet Klein, the director of conservation and community science for the Golden Gate National Parks Conservancy. “Those decades of work really matter: You never know it’s going to matter until a collapse is upon you.”

The new project, dubbed the Marin Monarch Overwintering and Breeding Habitat Assessment and Restoration Project, falls to the OneTam Collaborative, which includes the conservancy, the National Park Service, California State Parks, Marin County Parks and the Marin Municipal Water District. With a three-year timeline and an overall estimated cost of $768,000, the effort will mainly take place on lands managed by these agencies as well as some private properties that have historically served as key habitat. 

Beginning this year, an ecologist will conduct site assessments, visiting the known overwintering areas on the coast and breeding habitats further inland and selecting those most in need of restoration. Next year, conservation work on park service lands where the monarchs overwinter will include the removal or trimming of trees, the removal of understory brush and invasive species, sowing nectar plants, and establishing native trees. 

On county lands that serve as breeding habitat, the project will center around milkweed, which is the only plant monarchs lay their eggs on and which monarch caterpillars eat. Milkweed declined nationwide beginning in the mid-1990s with the increase in the use of the herbicide Roundup.

The new project intends to take out the invasive species that compete with the native variety of milkweed—narrow leaf—and to plant nectar plants that provide sustenance. A new map informed by LiDAR technology that shows flora throughout Marin in great detail that was initially developed to assist firefighting will go live soon, providing guidance for this aspect of the initiative. 

Mia Monroe, a National Park Service ranger who started the counts more than 20 years ago and coordinates efforts in Marin as a volunteer, likened monarchs to canaries in the coal mine. “Due to the climate crisis and pesticides and the loss of habitat, everything is suffering—from salmon to dragonflies to bees. This is a biodiversity crisis. It is easy to understand that by looking at this iconic insect: the monarchs. It gets people to start to pay attention, to value the small things,” she said.

While OneTam pursues the conservation project, the Environmental Action Committee of West Marin has also zeroed in on monarchs. As a result of a report the group produced last year, the E.A.C. and numerous local partners launched an education campaign in West Marin. According to executive director Morgan Patton, the groups are also collaborating with local nurseries to stock the right seeds and plants, and with farmers and other land managers to improve butterfly habitat.