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San Francisco Estuary Invasive Spartina Project
Control Program
Control Schedule (PDF) |  Control Sites | Field Operations Group

Implementation Strategy

Prioritization Strategy. With the complex non-native Spartina infestation currently (2005) covering over 1,200 acres, it is important to set priorities and proceed in a systematic manner. Consistent with the Integrated Vegetation Management (IVM) approach, the first priority of the Control Program is to prevent the establishment of new cordgrass populations in areas that are currently not infested. This is particularly important in areas where Spartina would then be able to spread rapidly to other locations - such as near the Golden Gate, where it may spread to west Marin estuaries or the outer coast   - or near a proposed tidal marsh restoration site where it would quickly infest the newly restored habitat. Maps of non-native cordgrass locations developed by the Invasive Spartina Project provide an accurate picture of the “edges” of the current infestation, and help to identify the sites or regions that should be targeted first in a containment strategy. In addition, the Control Program receives reports from landowners and naturalists on a regular basis when a new stand of invasive cordgrass is discovered.

As mentioned previously, the international panel of experts gathered at the Third International Conference on Invasive Spartina indicated that anything less than a rapidly implemented, full-scale eradication program would likely fail. Therefore, starting in 2005, the Control Program has essentially targeted for eradication all known infestations of non-native Spartina in the San Francisco Estuary.   However, there are a handful of areas that were not fully treated in the initial year, and a strategy of containment of outliers and/or prioritizing based on prolificity (e.g. level of fertility) was utilized.

A primary consideration for site prioritization is the presence of California clapper rail at many of the non-native cordgrass-infested sites. The Programmatic EIS/R includes several proposed mitigations and a stringent set of best management practices to reduce the Control Program’s short-term impacts on the clapper rail. In addition, in 2005, the ISP, working with USFWS biologists, performed a Bay wide assessment of the potential impacts to California clapper rail due to the Control Program. The Spartina Control Impact Evaluation Matrix (SCIE-M, PDF) quantifies temporary impacts to marshland habitat that will occur as a result of non-native Spartina control through four years of anticipated treatment activities (2005-2008), and assesses the effects of this control work on clapper rail carrying capacity. Using the mitigations identified in the PEIS/R, and the lessons learned from the development of the SCIE-M and from Bay wide clapper rail surveys in the winter of 2004-2005, the ISP developed 2005-2007 Site-Specific Control Plans for all 132 invasive Spartina sites around the Estuary (www.spartina.org/control/sites.php). In September 2005, the U.S. FWS issued a Biological Opinion under a Section 7 consultation that approved these plans with certain mitigations. Several sites with the highest clapper rail densities that are predominantly invasive Spartina with few native marsh plants will be treated with a phased approach. This will result in treatment of a portion of the infestation, allowing for some native plant regeneration before the remaining cordgrass is eliminated.

Site-specific selection of control methods. A number of factors have been considered to determine what control methods will be implemented at each site. Control of noxious weeds from the perspective of IVM focuses on the harmonious use of several management methods to reduce the damage caused by the infestation. No single treatment technique is expected to be completely effective on its own; most frequently the methods are combined according to site-specific needs to achieve the desired control objective with minimized adverse impacts. Potential aquatic herbicide treatment sites have been selected based on site conditions, the severity of infestation, an evaluation of short- and long-term environmental impacts compared to other treatment methods, efficiency, cost, and proximity of the treatment site to sensitive receptors.

A Site-Specific Control Plan has been developed for each treatment site based on specific site conditions, adjacent land uses, feasible treatment methods, costs, and budget. The plans identify the suite of methods to be used, time schedules, and necessary phasing and coordination. Depending on the methods selected, the plan identifies and addresses such issues as endangered species, adjacent land uses, sensitive receptors, site safety and access, spill prevention, sediment contamination and so on.

Post-treatment monitoring and management. In the initial years of the Control Program, monitoring will ascertain the efficacy of the previous year’s treatment and determine the area that needs to be controlled in the current year. The size of the remaining infestation often determines the most appropriate control methods to be implemented. As treated cordgrass sites approach eradication, they will be monitored to verify that (a) no surviving remnants of treated clones have regenerated; and (b) the site is not reinvaded by dispersal from seed or rhizome fragment sources.

Ultimately, eradication objectives must be integrated with local marsh management or restoration objectives. These may include: (a) restoration to pre-invasion mudflat or unvegetated channel conditions; (b) natural or accelerated succession to tidal marsh plain and creeks, such as in tidal marsh restoration sites; or (c) restoration of pre-invasion native cordgrass-pickleweed dominated vegetation composition and structure. Each of these target conditions entails different approaches for monitoring and management following treatment, and different levels of effort and efficiency.

In relatively high-energy environments at low elevation where establishment of any native vegetation is rare, such as open and exposed bay mudflats, post-treatment monitoring would be relatively straightforward. No revegetation would be appropriate where the target condition is restoration of mudflat or unvegetated channel. Once the Spartina is eradicated from the site, the dynamic natural tidal processes of the Estuary should restructure these sites and return them to their natural condition.

Where invasive cordgrass has caused sufficient sediment accretion to raise the marsh elevation and cause a shift from mudflat to mid or high marsh that will be dominated by pickleweed in the future, monitoring in treated areas would require a regular annual effort. Post-treatment re-invasion would be easy to detect and reverse by low-level maintenance (manual removal, spot-spraying or cut-stump herbicide paste application). This may also include the control of other invasive, non-native weeds such as Lepidium latifolium (pepperweed) that can colonize these higher elevation zones accreted by the hybrid Spartina. No other vegetation management would be required in areas where the dominant native salt marsh plants will rapidly colonize and resist re-invasion. The restoration of other sites may be enhanced or accelerated through native planting, such as young restoration sites or other marshes that were large Spartina monocultures, which receive little input of native seed to begin restoration through natural processes alone.

More challenging would be eradication in tidal restoration sites or tidal channels with predominantly low marsh, or substrate elevations in the tidal range of low marsh. Most problematic would be these low elevation systems surrounded by seed or rhizome fragment dispersal sources of invasive cordgrass, particularly Atlantic smooth cordgrass. Planting treatment sites with native Pacific cordgrass would compound this problem rather than mitigate it, because plantings would interfere with detection of re-invading non-native cordgrass, and would probably generate significant proportions of hybrid invasive seed due to “pollen swamping” if surrounding infestations (smooth cordgrass pollen sources) are substantial. For large treatment sites that will be restored to native Pacific cordgrass while surrounding infestations persist, post-treatment monitoring and management should be coordinated with targeted reduction/eradication of key seed source populations, sub-regional suppression of invasive seed production, and scheduling of re-establishment of tidal marsh vegetation.

Program Approach Treatment


Preserving Native Wetlands
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