Spartina alterniflora: Treasured on the East Coast, reviled on the West Coast

Spartina alterniflora (Smooth Cordgrass) is a species of marsh grass native to the Atlantic and Gulf coasts of the United States, where it is considered a valuable plant making important contributions to the coastal ecology:

•  Its dense growth provides protection against storm surge and “erosion control along shorelines, canal banks, levees, and other areas of soil-water interface.”(1)
• It filters nutrients, sediments and toxins from the water that flows off the land before reaching the ocean, acting as a natural water treatment facility.
• It provides cover and food for birds, mammals and marine animals that live in the coastal marsh.  Many other marsh plants occupy the same marshlands.

  

Where Smooth Cordgrass has died back in its native range, the dieback has been considered a serious environmental threat:

• In 2001 the Governor of Louisiana declared a “state of emergency” when Smooth Cordgrass declined and the state obtained $3 million of federal funding to study and hopefully reverse the decline.  This study resulted in the development of a method of aerial seeding of Smooth Cordgrass to restore declining areas of marshland.(2)
• A similar, but smaller dieback of Smooth Cordgrass in Georgia led to a collaborative research and on-going monitoring effort by 6 research institutions in Georgia.(3)
• Similar dieback of Smooth Cordgrass has been reported as far north as the coast of Maine.  A researcher at the Connecticut Agricultural Experiment Station is quoted in that report as saying, “In New Orleans, if their marshes were intact, the storm surge of Katrina would not have reached the levees.”(4)

The war on Smooth Cordgrass in the West Coast 

Smooth Cordgrass is not native on the Pacific Coast of the United States.  Therefore it is treated as an alien invader to be eradicated with herbicides:

• $24 million was spent to eradicate Smooth Cordgrass in San Francisco and Willapa Bay from 2000 to 2010 (5)
• $16.3 million is projected to be spent on eradication efforts on the entire West Coast from 2011 to 2020 (6)

In 2006, 2,000 acres were treated with herbicides to eradicate Smooth Cordgrass in the San Francisco Estuary.    Most were retreated 3 to 5 times after initial treatment.  In 2010, twenty five sites were slated for retreatment, usually with herbicides.  The San Francisco Estuary Invasive Spartina Project (ISP) “defines a need for a zero tolerance threshold on invasive Spartina in the San Francisco Bay.”(7)

The ISP reports that imazapyr (Habitat) will be used in most sites, although it will sometimes be mixed with glyphosate (Roundup). (See SaveSutro for more information about imazapyr and its use in San Francisco.)  The ISP acknowledges that:

•  “little is known about the interactive effects” of combining these herbicides or any of the surfactants used with these herbicides.
• These herbicides will be applied using a variety of methods, including aerial spraying by helicopter.
• Although the ISP considers imazapyr a relatively non-toxic herbicide, it also acknowledges that imazapyr has only been used since 2005.  Therefore, “Only few toxicity studies exist for birds…no data exist for the potential toxicity of imazapyr to shorebirds.”(8) Given that one of the stated purposes of eradicating Smooth Cordgrass is to benefit the endangered Clapper Rail, it seems surprising that nothing is known about the effects of imazapyr on any shorebird, including the Clapper Rail.

Why is Smooth Cordgrass treasured on the East Coast and reviled on the West Coast?  That question was asked and answered by Professor James Morris at an Environmental Law Conference in Eugene, Oregon on March 5, 2011.  Professor Morris studies Smooth Cordgrass at the Baruch Institute for Marine & Coastal Sciences at the University of South Carolina.  We urge our readers to watch a video of his presentation to the conference in Oregon.  We will draw upon that video in addressing the claims (9) made by those who are attempting to eradicate Smooth Cordgrass on the West Coast:

Indictment:  Smooth Cordgrass will invade mud flats, eliminating valuable habitat for plants and animals that inhabit that segment of marshland.

Defense:  According to Professor Morris, Smooth Cordgrass was introduced to the West Coast in shipments of Eastern oysters over 100 years ago without eliminating mudflats.  Europe has had similar experience with Smooth Cordgrass which was introduced there to reduce sediment in harbors.  Professor Morris showed pictures of Danish and Dutch estuaries in which Smooth Cordgrass has existed since the 1930s without radically altering the composition of the marshland.

Indictment:  Smooth Cordgrass will invade waterways, making them impassable.

Defense:  Again, since this has not happened in 100 years, there is no reason to assume it will happen in the future.  Furthermore, the USDA describes the narrow range of Smooth Cordgrass:  “the width and thickness of vegetative colonies are controlled by a number of site specific conditions such as elevation, shoreline slope, and frequency, depth and duration of flooding” as well as salinity and acidity.  In other words, the range of Smooth Cordgrass is limited.

Indictment:  Smooth Cordgrass does not provide habitat value equal to the native species of cordgrass with which Smooth Cordgrass competes, particularly for the endangered Clapper Rail.

Defense:  Mike Casazza at the Dixon Field Station of the USGS is presently studying the effect of eradicating Smooth Cordgrass on the reproductive success of the Clapper Rail:  “Removal of invasive Spartina accomplishes the goal of Spartina eradication, but if rails fail to survive and reproduce, then the goal of species protection is unfulfilled…the potential for impact from invasive Spartina removal and the potential for mitigation by rail ecology and behavior remain poorly understood.”(10)  Clapper Rails live in Smooth Cordgrass on the East Coast:  “numerous” Clapper Rail families were observed nesting in Smooth Cordgrass on Dewees Island, South Carolina.(11)

Indictment:  Smooth Cordgrass is outcompeting the native Pacific Cordgrass (Spartina foliosa) by displacement and hybridization.

Defense:  This is probably true because of the characteristics of the Pacific Cordgrass:  “S. foliosa occupies a very limited range in the intertidal zone, and the leaves and stems wither in fall and shed in the winter, leaving sparse standing matter that is ineffective at trapping sediment.  Seedlings of S. foliosa are seldom found in established marshes and appear only intermittently in sheltered upper mudflats.”(12)  In other words, the range of the native cordgrass is narrower, it does not grow as densely, and it is not foliated year around, thereby creating opportunities for the non-native cordgrass to occupy bare ground.  Since marsh grasses are beneficial to the environment and its inhabitants, the ability of Smooth Cordgrass to occupy this vacuum seems a benefit, particularly since native cordgrass is less capable of removing sediments from water, reducing its effectiveness as a filter of pollutants from water flowing into the bay.(13)

Smooth Cordgrass is treasured on the East and Gulf Coasts because it performs valuable ecology services.  Although it performs the same ecological functions on the West Coast, it is being eradicated.  The evidence available to us suggests that we are spending a lot of money and effort, as well as using a lot of herbicides, to eradicate Smooth Cordgrass only because it is not native to the West Coast.   

• Smooth Cordgrass provides superior storm surge protection particularly during winter months when native cordgrass is dormant.
• Smooth Cordgrass is more capable of filtering pollutants from water flowing into the bay.
• Smooth Cordgrass provides at least equal habitat quality to the endangered Clapper Rail and probably other marsh plants and animals as well.
• Smooth Cordgrass has not blocked waterways or eliminated mud flats in comparable situations over long periods of time

We invite our readers to supply us with evidence that there are legitimate reasons for the campaign against Smooth Cordgrass.