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Eco-warriors battle bad grass

A vigorous and invasive English weed has residents in its path talking about its impact on local estuary habitats. Known as Spartina anglica, or Spartina, this cordgrass has found its way to various areas around Point Roberts, Delta and Vancouver Island and currently represents a serious threat to local species.

Ducks Unlimited, with the help of local volunteers, has been attempting to curtail the propagation of Spartina in the bay and has determined that, if left alone, Spartina will elbow out the native grasses and could build enough momentum to take over entire estuary habitats.

Originally embraced as a grass species to assist in shoreline stabilization, Spartina was introduced to estuaries susceptible to marine erosion worldwide. Unfortunately, the qualities that make it ideal for land claiming and flood defense purposes have also enabled it to out-compete the local grasses of the Pacific Northwest.

Here in Washington, the cordgrass has colonized over 3300 hectares of marine inter-tidal habitat in at least 73 sites. These sites, concentrated in Puget Sound, have recently spread northward, and Spartina is now too close for comfort.

Spartina’s exceptional abilities are not only in its skill in competitively excluding native species, but also in its tendency to turn estuaries into unrecognizable and unsuitable habitats that has become a great concern to conservationists. The grass establishes itself either by seed germination or root fragments that are carried by the tides to new habitats.

Kim Houghton, a biologist with Ducks Unlimited, often finds Spartina “as a lonely plant or clone on the mud flat one to two kilometers off shore.”

However, if it’s not found and removed at this point in its life-cycle, it can reproduce to construct a dense monoculture of Spartina within the area. The weed then modifies its habitat by accreting sediment in its large root system, slowing water flow and eventually elevating the intertidal habitat.

Dr. Gary Bradfield, of the University of British Columbia, notes that “species with a large biomass like Spartina increase the amount of detritus (dead organic matter) in the habitat when they die, thus affecting the food chain at a very basic level.” This can have reverberating impacts across numerous levels, especially on invertebrates, shellfish, fish, and waterfowl.

Concerns for loss of species diversity have been exacerbated by economic concerns from the loss of commercial shellfish habitats and food sources for many fish, as well as the redistribution of sediment into shipping channels. The economic impacts of invasive species, including large expenses of removal, cost the US more than $100 billion every year, thus motivating the community to act sooner rather than later to mitigate the problem before Spartina is able to establish itself.

While the introduction of Spartina to our local waters has only occurred in the last few years, the worldwide invasion has been decades in the making. The concern is that the more established the weed becomes in its environment, the more drastic the measures to remove it become.
For instance, management teams in Puget Sound have applied numerous techniques, such as manual cutting, rotoburying, smothering with sand or plastic sheets, herbicides, burning, and experiments with biological control. As these nonselective treatments generally disturb the other native inhabitants of salt marsh communities, it is generally agreed that Spartina should be spotted and removed before it takes over habitats and these techniques are necessitated.

Unfortunately, this remarkably versatile and resilient cordgrass is proving to be quite a challenge to control due to the widely varying environments it’s able to inhabit. Houghton says support is finally increasing for the removal and management of Spartina. She is involved with teams that are employing selective hand removal with the help of a large amphibious excavator.

“We will continue to remove and manage Spartina until we don’t see a need anymore or when support halts,” says Houghton. But will the need ever stop? Dr. Sally Hacker, an Oregon State University researcher, reports that ten years of Washington management of Spartina have only resulted in a 13 percent decline in the grass. So as long as the rest of Washington is unable to eradicate the cordgrass, there will be a continuous influx of the weed locally.

So where does this leave our efforts to limit the invasive success of Spartina within local ecosystems?

Control efforts are urgently recommended despite the continued influx, as the effectiveness in Washington’s management strategies has improved, and current research has been encouraging as to the future success of removal techniques.

Thorough eradication of Spartina from our shores can only be accomplished by community interest and support, and volunteers in the selective hand removal of the weed are crucial.

The community is in a unique position, as we are able to prevent establishment, and thwart the economic impacts and the negative impacts on local biodiversity, if actions are quickly taken.