Ventura County
Monarch & Pollinator Habitat Restoration
Habitat Assessment and Restoration for Monarchs - Overstory Nectar Enhancement and Expansion (HARMONEE) & Oak Park Unified School District Project (OPUSD)
Almost everyone is familiar with the large orange and black butterfly known as a monarch that visits gardens and parks in the summer. Every fall additional monarchs butterflies migrate to the coast of California from across western North America to escape inland winter weather. The western population of monarch butterflies (Danaus plexippus plexippus) suffered steep decline in recent years, researchers and community scientists estimate that only a fraction of the population remain —– a decline of more than 80% has been seen in central Mexico and a decline of more than 95% has been seen in California (The Xerces Society for Invertebrate Conservation 2024). Reasons for the declines are not completely understood but contributing factors included the degradation of overwintering sites, disappearance of summer breeding sites, pesticide use, and climate change.
Overwintering Site Restorations
During winter, monarch butterflies inhabit groves of trees along the coast of California starting October 1st through March 15th, a period known as the monarch overwintering season. Migrating monarch butterflies begin arriving at roosting sites in early October and often start forming small scattered clusters throughout the grove. Continuing through the months of October and November, monarchs will search for well-protected groves of trees and actively move between roosting sites. In December and January, monarchs form dense clusters as winter storms hit the coast. In February and March, they mate and disperse from their roosting sites and females begin searching for emerging milkweed to start the next generation of monarchs.
Where monarchs roost for the first one or two months of the season and abandon the site by mid to late December, is known as an autumnal roost. Where monarchs roost in a location for the duration of the season, the site is called an overwintering roost. Monarchs are highly mobile during the overwintering season and use roosting habitat as a network across landscapes. They arrive and depart sites based on available suitable habitat and microclimate conditions.
Ventura and Santa Barbara county have an exceptional number of well-known, historically used overwintering monarch sites. Many of which classify in the top 50 important California sites according to the Xerces Society for Invertebrate Conservation ( westernmonarchcount.org/map-of- overwintering-sites/). The habitat value of many of these sites has decreased over time due to stressors such as drought, wildfires, development, and mismanagement. In addition, wide-spread habitat protection from development and other disturbances at these sites is essentially non-existent.
Breeding & Migratory Site Restorations
During the spring and summer months, migratory monarchs and other native pollinators like bees and other insects rely on nectar producing plants to feed, reproduce, and rest. These sites are typically an appropriate distance from any known coastal aggregations and monarch butterfly overwintering sites. Sites should not be near heavy pedestrian traffic and human activity and excess winds or heat, to give monarch butterflies a safe place to lay their eggs and caterpillars some space and more favorable conditions to develop. Breeding and migratory sites are known for their flash, flowering plants like bush sunflower, California fuchsia, golden yarrow, and native milkweed. These sites should include plenty of native milkweed to support adults and caterpillars.
Adding blooming, native plant species for monarch breeding and migratory habitats (BMH) is a multi-beneficial effort that not only contributes to overall monarch population recovery, but also enhances resources used by other local and regional pollinator populations such as hummingbirds, other butterflies and insects. Other wildlife species, such as songbirds, will also benefit from additional native food, cover, and breeding resources provided by restoration of a variety of shrubs and perennials
What is the VCRCD
Doing to Help Monarchs and Native Pollinators?
In 2022, the Ventura County Resource Conservation District (VCRCD) began the Habitat Assessment and Restoration for Monarchs – Overstory Nectar Enhancement and Expansion (HARMONEE) and Oak Park Unified School District (OPUSD) projects in Ventura County to enhance and protect monarch butterfly overwintering and breeding and migratory habitats. These sites are located throughout the Ventura County except for one located just on the boarder of Santa Barbara County.
These projects have two equally crucial objectives:
1) to restore, maintain and improve habitat quality for monarch adults and larvae, as well other native pollinators, and
2) restore, maintain, and improve the quality of monarch overwintering habitats, which includes supporting the health of existing vegetation, adding vegetation that will improve microclimate conditions preferred by roosting monarchs, and increasing nectar sources for monarch and other pollinators.
This story map illustrates VCRCD’S efforts, in partnership with organizations like the Wildlife Conservation Board, the U.S. Fish and Wildlife Service, California State Parks, the Santa Monica Mountains Conservancy, local park and school districts, to restore, enhance and expand breeding, feeding and overwintering habitat for this iconic species.
Currently, there are 11 sites restored and monitored in the HARMONEE project and 3 sites restored and monitored in the OPUSD project for monarch butterflies and other native pollinators. The VCRCD is still implementing and executing 3 overwintering sites for the HARMONEE project which will be restored this year.
More information or questions please email jia.wiebe@vcrcd.org or rachel.ray@vcrcd.org
