The Land Trust of Napa County today announced the discovery of a kaleidoscope of monarch caterpillars and butterflies at Sutro Preserve, a major milestone for local nature recovery after the devastating 2017 Atlas fire and a crucial indicator of the success or ongoing conservation efforts in the North San Francisco Bay Area.
The Land Trust team found the 20 monarch caterpillars and multiple adult butterflies eating early emerging heartleaf milkweed plants during a routine seed check at the 1,350-acre preserve off Atlas Peak Road in the eastern Napa Valley. The plants are part of a habitat restoration project paid for by the Western Monarch Habitat Improvement Project, with co-funding from the U.S. Fish and Wildlife Service and a local donor.
“Finding these caterpillars and butterflies gives us a huge boost of hope for this vulnerable species,” said Melanie Parker, Land Trust chief executive officer. “It shows our restoration work is achieving results and proves how vital these protected corridors are for wildlife.”
Scientists estimate that western monarch populations have plummeted by more than 95% since the 1980s, driving urgent, collaborative conservation initiatives like the Western Monarch Habitat Improvement Project to stave off extinction. Federal officials have proposed listing the monarch as threatened under the Endangered Species Act.
The Sutro Preserve discovery comes as monarchs begin their annual fall migration, which takes place in August and September. The site plays a vital role as a refueling station for butterflies that can travel up to 1,000 miles. Without these protected, food-rich corridors, the migrating generation cannot survive the long journey.
“Sutro Preserve is a crucial steppingstone in the western monarch’s migratory landscape, providing native milkweed for caterpillars to feed on, as well as sturdy, protected vegetation where they can form chrysalises,” said Erin Arnsteen, community conservation specialist with Monarch Joint Venture and co-founder of Western Monarch Society of Napa County. “The preserve also provides diverse native nectar-producing plants for adult monarchs to feed on, along with trees and other sheltered habitat where they can rest and roost as they fly through Napa County.”
Volunteers and American Conservation Experience crews provided labor for the project. The Laguna de Santa Rosa Foundation Nursery propagates collected seeds which are then returned to the preserve as seedlings.
“Our parentship with the Laguna de Santa Rosa Foundation is critical to ensuring that we are able to support this landscape by reestablishing patches of native wildflowers, benefitting local biodiversity and this species as a whole,” said Clarisa Rosas, Land Trust assistant stewardship coordinator.
Originally known as Sutro Ranch, the preserve was donated to the Land Trust in 2014 by the estate of Elizabeth “Betty” Sutro. At the time, it marked the single largest land gift in the Land Trust’s history. The Atlas fire scorched large swaths of the preserve, up to its 2,663-foot peak. The Land Trust has since transformed Sutro Preserve into an ecological corridor focused on wildfire recovery, proactive forest management and habitat restoration.
Get a glimpse of the monarch restoration project Oct. 15 when the Land Trust staff will lead a milkweed planting day and one-mile hike to Sutro Preserve. Details at https://napalandtrust.org/explore-the-land/land-trust-hikes/ .
