Drew Kerr of the Invasive Spartina Project discussed how managing invasive plants as tidal marshes develop and mature provides a critical foundation for successfully establishing diverse Restoration Project marsh plant communities. With nearly 20 years working with Bay marsh invasives and a passion for wetland and aquatic ecologies, Drew shared his knowledge and experiences with three invasive species: Hybrid Spartina alterniflora, the focus of a multi-year Bay regional removal effort; Paspalum vaginatum, an escaped turfgrass only recently detected but already presenting a threat within Restoration Project boundaries; and Limonium ramosissimum, Algerian sea lavender, often a problem on levees and higher ground.
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Speaker Bio: Drew Kerr is the Treatment Program Manager for the State Coastal Conservancy’s Invasive Spartina Project (ISP). Before joining the ISP in 2005, he was the Aquatic Noxious Weed Specialist for the King County Department of Natural Resources in Seattle. At King County, Drew also worked extensively with native Pacific Northwest amphibians and on land use policy that established protected wildlife corridors and wetland complexes. He has a BS in Environmental Policy & Behavior and a BA in Economics from the University of Michigan and a professional certificate in Wetland Science and Management from the University of Washington. He helped initiate and manages two smaller invasive tidal marsh plant projects in the Estuary, for invasive sea lavender (Limonium spp.) and seashore paspalum (Paspalum vaginatum). Drew has served on the Board of Directors for the California Invasive Plant Council since 2014, as Vice President since 2019.
Scientific Question
This research will help the Restoration Project answer a central scientific question in its Adaptive Management Plan under the topic of Invasive Species:
Can invasive and nuisance species be controlled, and if not, how can the impacts of these species be reduced in future project phases?
Brown Bag Science Speaker Series
This presentation is one in a series put forth by the South Bay Salt Pond Restoration Project. The series will address science and adaptive management done in support of or in collaboration with our Restoration Project as well as relevant outside work. Speakers will discuss research, modeling, and monitoring efforts and how Restoration Project managers are using science to inform decisions about restoration, flood risk management, and public access.
Further Info on Topic: Tidal marsh restoration in the San Francisco Estuary, led by the Restoration Project, is exciting wetland habitat creation in action. A recently breached pond is like a new canvas poised for nature to paint a tidal marsh community on the open mud. The new landscape develops in slow motion for years, unfolding piece by piece until suddenly the plant community reaches critical mass and reveals itself to be an established marsh. Wildlife such as the endangered Ridgway’s rail discover this new habitat and begin to call it home, increasing their population.
However, these San Francisco Estuary restoration marshes are developing within a matrix of stressors that have been generated or exacerbated by humans. In addition to climate change and sea level rise, invasive plants are powerful agents of change that can permanently alter the trajectory of the best of our collective restoration intentions. As a young native plant community begins to thrive in these reclaimed marshes, it doesn’t have the resilience of a mature marsh, and aggressive invasive plants can spread rapidly and effectively exclude our desired residents. Wetland invasive plants are free to disperse and spread on the tides to potentially wreak havoc on neighboring marshes. Managing invasive plants within this urbanized tidal ecosystem is essential to allowing young restoration marshes to thrive, and to protect our remnant historical marsh resources as well.
In this presentation Drew will examine three invasive tidal marsh plants impacting the Restoration Project. Hybrid Spartina alterniflora, a powerful ecosystem engineer normally living in the low marsh and mudflats, once infested thousands of acres in the Estuary and has been the focus of a coordinated baywide project of the U.S. Fish and Wildlife Service and the State Coastal Conservancy for nearly 20 years. In contrast Paspalum vaginatum, an escaped salt-tolerant turfgrass, was only recently detected within Restoration Project boundaries but has already clearly demonstrated its ability to thrive at mid-marsh elevation in this harsh environment, dominating where it establishes. Limonium ramosissimum (Algerian sea lavender) invades the high marsh and upland transition zone. These higher tidal elevation zones normally have greater plant diversity, providing a broad range of habitat values and ecosystem services, yet they have been disproportionately impacted by human development due to their proximity to the upland edge. The many levees around restoring marshes provide high marsh edges that can harbor invasive Limonium, creating points of dispersal to the existing marshes of the Estuary.
These three invasive plants demonstrate how essential long-term stewardship is to the success of tidal marsh restoration around the Estuary. Both to manage existing threats and to detect new introductions early enough to prevent widespread establishment. Allowing for a rapid response to be mobilized while the costs and management impacts are much lower.
