The Humboldt Bay Spartina densiflora Control Symposium was held in Eureka, CA, on June 29 and 30, 2010. The Symposium was sponsored by the California Coastal Conservancy, the US Fish and Wildlife Service, the Humboldt Bay Harbor, Recreation and Conservation District, the Friends of the Dunes, and the City of Eureka. Approximately 50 scientists, land managers, environmental professionals, and community members gathered to share information about the status of invasive Spartina and control programs in the region, up and down the West Coast, and as far afield as Spain.
The first day of the symposium was spent in the field, visiting Spartina control and research sites around Humboldt Bay. Participants visited the City of Arcata’s McDaniel Slough Restoration site in the morning, where Craig Benson of the Redwood Community Action Agency described the mechanical and manual techniques used to remove Spartina from the future salt marsh. The next stop was the Mad River Slough Wildlife Area, where Luc Lagarde, Humboldt State University graduate student and master Spartina mower, described the mechanical control techniques developed at the Humboldt Bay National Wildlife Refuge (HBNWR). Luc discussed ongoing research to optimize mowing techniques. Mechanical control involves using a metal bladed brush cutter to cut into the shallow rhizomes of Spartina in the top four inches of the marsh. Current research is comparing the efficiency and efficacy of using a vertical grinding method to destroy these rhizomes vs. a slicing method. The final stop of the day was at the Ma-le’l unit of the HBNWR, where control has been completed on approximately 25 acres of salt marsh. Participants were impressed by the healthy appearance of the restored native salt marsh, although everyone noted the presence of Spartina seedlings, evidence of the need for ongoing follow-up and regional control.
The second day of the symposium consisted of a series of presentations given at the Wharfinger Building. The presentations discussed Spartina densiflora ecology and control in Humboldt County, San Francisco Bay, the Oregon Coast, Washington, Spain, and Argentina. Many of these presentations are available below . Many thanks go out to the Symposium’s sponsors. The City of Eureka generously provided the meeting space, Friends of the Dunes provided refreshments and staff time to make the symposium run smoothly, HBNWR, and the Harbor District provided logistical support and staff assistance, and the Coastal Conservancy provided funding for travel expenses and logistical support. Thanks especially to the Lost Coast Brewery for providing beer and Coast Seafoods for a delicious oyster BBQ!
Brief highlights of the presentations are provided below:
Joel Gerwein, State Coastal Conservancy project manager, began by providing an overview of Spartina densiflora impacts on the bay. Joel introduced the audience to the West Coast Governors’ Agreement Spartina Action Plan, explaining that it places a high priority on eradicating Spartina in the Humboldt Bay area.
Zack Grazul of the HBNWR described the regional Spartina mapping project, whose goal is to map invasive Spartina in the approximately 1,500 acres of salt and brackish marsh in Humboldt Bay, the Eel River Delta, and the Mad River Estuary. The mapping project is field-based and also involves aerial photo interpretation. Mappers collect information for each Spartina occurrence on substrate type, percent cover, and plant size. This information will be useful in determining the time and resources that will be required for control.
Andrea Pickart, Refuge Ecologist at HBNWR, reviewed the development of Spartina control methods at the refuge, beginning with corded weedeaters and evolving to the grinding method with metal bladed brushcutters used today. She discussed methods for dealing with Spartina wrack generated by mowing, as well as for ongoing control of seedlings. Andrea also described the process of restoring former Spartina-dominated areas to native salt marsh. Active revegetation was employed in several areas, but monitoring results indicate that the native plants recolonize control areas without active planting in most areas.
Eric Nelson, HBNWR Manager, reported on the effort to control Spartina throughout the Refuge. HBNWR received a $1 Million US Fish and Wildlife Service grant to fund this effort, which will address 300 acres of salt marsh contained within the Refuge. The project involves use of handheld brushcutters for low density areas and high density areas that are inaccessible to large equipment. HBNWR plans to experiment with large equipment, in the hopes of using it on accessible high density areas. Eric discussed the mapping and monitoring components of this project and acknowledged the contributions of the many partners providing labor, outreach, and administrative coordination for the project.
Craig Benson of the Redwood Community Action Agency (RCAA) spoke about the Spartina control component of the City of Arcata’s McDaniel Slough Restoration Project. Craig provided an overview of marsh restoration projects in Humboldt Bay, as well as a focused discussion of the Spartina mapping and control efforts at McDaniel Slough. RCAA used its own staff as well as CalFire crews to carry out the work, which included the use of metal bladed brush cutters, as well as manual removal with shovels and Pulaskis. Bulldozers will be used to remove Spartina along the new levees to be located in the project area. Craig also discussed the planned use of active and passive revegetation in different portions of the project area.
Drew Kerr of the San Francisco Estuary Invasive Spartina Project (ISP) shared his experiences with control of S. densiflora, primarily in the Corte Madera Creek watershed in San Francisco Bay. Drew described the combination of methods used by ISP and its partners, including treatment with imazapyr herbicide, manual removal with shovels, and mowing. The ISP was constrained in the type and timing of its control efforts until recently because of regulations to protect clapper rail breeding, but has successfully controlled S. densiflora in Corte Madera and 15 other locations in San Francisco Bay. Ongoing efforts continue to remove seedlings and to complete the removal of some infestations.
Nels Mikkelsen of the Washington State Department of Agriculture told the story of Spartina densiflora control in Grays Harbor. Both Spartinaalterniflora and S. densiflora are present in Grays Harbor. A mix of imazapyr and glyphosate herbicides was used for control, and the infestation area was surveyed with a fine-resolution transect system to reduce the chance that any Spartina would be missed. The overall Spartina infestation in Grays Harbor has been reduced from approximately 10 acres in 2005 to less than half an acre in 2010. Nels emphasized the importance of continuing surveys to ensure that Spartina eradication was completed.
Mark Sytsma, Director of the Center for Lakes and Reservoirs (CLR) at Portland State University, spoke about Spartina control in Oregon. Early detection and rapid response is an important component of the control program there, with annual surveys, either by air or by ground and boat. Potential habitat throughout the state has been categorized as high- or low-risk for infestation by Spartina, although recently mapped occurrences in British Columbia suggest that S. densiflora can grow in a broader range of habitats than has been recognized . Mark shared several case studies of early detection, ranging from a sizable clump of S. alterniflora initially misidentified as Phragmites by local resource managers to a single Spartina individual detected and immediately removed by CLR staff during annual surveys.
Jenny Ericson, National Invasive Species Program Coordinator for USFWS, provided the big picture regarding invasive species management nationally. 2.5 million acres in the National Wildlife Refuge system are currently infested with invasive plants, and invasive animals are also widespread on refuge lands. Invasive species management is the fastest growing area of expenditure for refuges. Jenny emphasized the importance of preventing the spread and establishment of invasive species, and gave examples of prevention strategies, such as a truck wash system for refuge visitors and a community education program. USFWS has recently established invasive species strike teams that assist in eradication of new infestations. Restoration is the ultimate goal of USFWS invasive species control efforts.
Alejandro Bortolus, professor of ecology at Argentia’s National Patagonian Center, described the ecology of S.densiflora in its native region on the eastern coast of South America. Seed viability and density appear to increase when the plant is subject to certain types of disturbance, such as clipping or herbivory. S.densiflora shows a great deal of variability in its growth form and can grow in both muddy and rocky intertidal areas. It is a good invader, combining the ability for rapid colonization of new areas with gradual rhizomatous spread within an area after establishment. It is a bioengineer with the ability to drive changes in the benthic community. However, S.densiflora does have its limitations. It can grow at a limited range of tidal elevations, and is a weaker competitor at the edges of its tidal range.
Jesús Castillo, Professor of Ecology at the University of Seville, discussed the S. densiflora invasion of the Iberian Peninsula. Jesús described the recent discovery of hybrids between S.densiflora and native cordgrass in both San Francisco Bay and in Spain. These hybrids are currently sterile, but could become fertile in the future. S.densiflora grows across a wide range of elevation and inundation regime in the Iberian peninsula, and can even alter its perennial life history to grow as a biennial in low-elevation, frequently inundated areas. Seedlings can establish under a closed canopy of native vegetation, It is a serious threat to plant diversity in mid-elevation marshes there. S.densiflora appears to increase its growth rate with increased atmospheric CO 2 concentration, indicating that it may respond well to climate change. Manual control and active revegetation have been used on a small scale in Spain to restore infested marshes.
Local researchers provided updates on S.densiflora studies.
Luc Lagarde, HSU graduate student, described his recently funded study to estimate the contribution of S. densiflora to the Net Primary Productivity of Humboldt Bay’s salt marshes. Luc described a study conducted in the 1970s that concluded that S.densiflora, which was thought to be native at the time, was much more productive than pickleweed or saltgrass. Luc’s study will reexamine this question, and address other sources of productivity not measured in the 1970s study, including algae. This study will help indicate whether Spartina eradication could reduce the productivity of the Bay.
Desiree Davenport of the USFWS presented the results of an ongoing S.densiflora seed bank study. Preliminary study results indicate that there is a persistent seed bank, with up to 4 million seeds per acre! The longevity of the seed bank is the subject of ongoing research.
Annie Eicher of USFWS discussed the effects of Spartina control on two rare salt marsh plants, Humboldt Bay owl’s clover and Point Reyes bird’s beak. These two species require space and light and may be competitively excluded by Spartina. They have greatly increased in extent in the Ma-le’l Unit of HBNWR six years after Spartina removal. Results are not yet available on short-term impacts of Spartina removal.
For more information contact Andrea Pickart
More information on invasive Spartina
The Humboldt County Spartina Summit was held in Eureka, CA, on February 13, 2008. Approximately 50 scientists, land managers, environmental professionals, and community members gathered to share information about the status of invasive Spartina and control programs in the region and up and down the West Coast, and to explore regional Spartina management scenarios.
The morning and early afternoon consisted of a series of presentations regarding Spartina in Humboldt County, San Francisco Bay, the Oregon Coast, and Willapa Bay in Washington. Many of these presentations are available below.
Brief highlights of the presentations are provided below:
Andrea Pickart, the Humboldt Bay National Wildlife Refuge ecologist, presented information regarding the natural history and distribution of invasive Spartina, and described the remarkable success of local control efforts, as well as the daunting challenges that lie ahead. She noted that mechanical control of Spartina has been successful at eliminating mature Spartina individuals on a relatively small scale, but has been challenged by the influx of new Spartina seedlings into certain areas.
Heinz Falenski, Associate Faculty member at the College of the Redwoods, described his mathematical model relating environmental parameters to the presence of Spartina in Humboldt Bay marshes. Mr. Falenski explained that his model indicates that Spartina is especially likely to occur in sites that are very saturated (i.e. poorly drained), have high available phosphorus levels in the soil, and are at low elevation, and he discussed strategies for preventing Spartina invasion in restoration sites based on this information about its optimal habitat.
Dr. Milton Boyd, intertidal ecologist at Humboldt State University, described the mixed non-indigenous and indigenous invertebrate fauna found in Humboldt Bay’s salt marshes. Dr. Boyd raised the important question of whether eradicating Spartina might have negative impacts on the Humboldt Bay ecosystem by replacing a very productive plant that is a major source of carbon with less productive native plant species.
Dr. Mark Sytsma, Director of the Center for Lakes and Reservoirs at Portland State University, described Oregon’s efforts to protect its coastal marshes from invasive species. Dr. Sytsma spoke about the threat of seeds from Humboldt Bay Spartina colonizing marshes up the west coast, as demonstrated by a drift card study that showed numerous cards released in Humboldt Bay quickly reaching the Oregon and Washington coasts.
Peggy Olofson, Director of the Invasive Spartina Project in San Francisco Bay, described the efforts of her organization to control invasive Spartina. She described the challenges of controlling invasive Spartina in marshes where native Spartina and invasive-native hybrids are found. She also described efforts to control Spartina densiflora in Corte Madera, where herbicide and digging out of Spartina plants have been used. Dr.
Kim Patten, of Washington State University’s Cooperative Extension, described efforts to control invasive Spartina in Willapa Bay. These efforts have been underway for about 10 years. Dr. Patten described a variety of techniques that were attempted early on, and initially resulted in very limited success. Recent efforts have focused on herbicide use, and have been very successful. Dr. Patten discussed potential effects from herbicide applications, and potential long term changes to Willapa Bay marshes from the Spartina invasion.
Dr. Frank Shaughnessy, Professor of Botany at Humboldt State University, gave the last presentation of the day, focusing on primary productivity in the Humboldt Bay ecosystem and the role of Spartina in contributing to primary productivity. Dr. Shaughnessy stressed the importance of considering all the species that contribute to primary productivity, including algae and diatoms, rather than focusing only on large vascular plants such as Spartina. He also emphasized that it was important to understand the rate at which different species fix carbon in order to calculate net primary productivity, explaining that a large plant may fix high amounts of carbon, but may do so over a long period.
Following the presentations, summit participants split into small groups to discuss the following topics:
Joel Gerwein, project manager at the State Coastal Conservancy, concluded the summit by asking participants to remain involved over the coming months as planning for Spartina densiflora control in Humboldt Bay gets underway. A small group ended the day by visiting Vance Marsh to see Spartina and other salt marsh plants in person.