Cheadle Center for Biodiversity and Ecological Restoration

Ventura marsh milk-vetch (Astragalus pycnostachyus var. lanosissimus) is a California state and federally endangered species in the legume family (Fabaceae) which historically grew in alluvial coastal systems in Los Angeles and Ventura counties (USFWS, 2020). The species was declared extinct in the 1960s after several decades without record in surveys, but was rediscovered in 1997 in Oxnard at a planned development site; development was halted and the site was preserved in the following decades. Since then, the species has been reintroduced at McGrath State Beach in 2004 and Carpinteria Salt Marsh Reserve in 2002.

The establishment of Ventura marsh milk-vetch at North Campus Open Space and Coal Oil Point Reserve (COPR) in Santa Barbara County represent novel introductions outside of the historic range. These two locations comprise the upper and lower arms of the Devereux Slough, and intermittently tidal estuarine system. Ventura marsh milk-vetch prefers shallow or perched water tables in a dynamic system with somewhat regular disturbances to reduce competitive pressure. There was an earlier introduction to COPR in 1999 that was extirpated in 2019. The Cheadle Center reintroduced the species to COPR in 2022 in experimental seeding plots throughout the reserve, as well as establishing two experimental plots at the UCSB Campus Lagoon. Since these introductions, the Ventura marsh milk-vetch has flourished at North Campus Open Space in the original “main population” along the sandy edge of the slough and in several smaller occurrences throughout the open space. At Coal Oil Point Reserve, two of the nine seeding plots have established small, but consistent occurrences of milk-vetch over the last three years. The Campus Lagoon proved unsuitable habitat for the milk-vetch, with a lower water table than expected and significantly higher competitive pressure.

The populations at North Campus Open Space and Coal Oil Point Reserve both require active management and monitoring for continued survival of the species. Competition from both native and invasive species has been compounded by Nitrogen fixation by the milk-vetch and invasive Melilotus sp. These sites are vital to the conservation of a critically endangered species with only a handful of occurrences in the world. We hope the data and observations collected in this report will help inform future conservation efforts throughout the species range.