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Spartina Shakedown
"The November gales blew through - things bent down, folded in place. The dead spartina broke, blew off, wrapped onto the next stalks, and sank under the rains down to the live roots, mixing into the blackness. It was useful death."
Useful death - but of a more intentional kind than that described above in John Casey's award-winning novel Spartina - is the goal of scientists and government officials championing an all-out eradication program for an alien species of the marsh plant spartina that is wreaking havoc on restored wetlands.
"This is worse than a weed problem," says Debra Ayres of the U.C. Davis Bodega Marine Lab. "For our native cordgrass, it's on the scale of rape, pillage and impending ecological doom. This invader appropriates the seed resources of the native, and basically genetically absorbs the natives right out of existence," (by doing the plant equivalent of one creature fertilizing another's eggs).
The culprit is an Atlantic species of cordgrass known as Spartina alterniflora - the most alarming among a dozen exotic wetland and riparian grasses now making inroads into the marshes, mudflats, creeks and channels of the San Francisco Estuary. It is one of the ironies of environmental restoration that as one attempts to reach a natural state, one frequently reaps unintended consequences that require even more human interference. "Restoration projects create a blank template for plants to move into," says hydrologist and wetland designer Philip Williams. "If you have an uncolonized mudflat with the right conditions, sometimes it's a case of who gets there first."
Spartina alterniflora has increasingly been first on site at restoration projects on the southeast bayshore, largely due to the outpouring of seeds from huge established populations of this smooth eastern cordgrass at New Alameda Creek and on the San Bruno coast - populations that got a roothold here two decades ago.
The first strains of smooth cordgrass, which is native to the coastline from Maine to Texas, were introduced in the 1970s by pioneers in ecological restoration who imported seeds and conducted planting trials on the East Bay shore. The action had unforeseen results. New and soon-to-be published research by Ayres and Don Strong, also of U.C. Davis, shows that in wetlands where smooth cordgrass was deliberately introduced, there's no native cordgrass left. Ayres examined 25 marshes throughout California, using genetic markers to identify the spread of Spartina alterniflora and the degree of hybridization with the natives. In addition to the influx around New Alameda Creek, she found extensive hybridization at salt ponds opened to the tides.
And it's not just the plant's phenomenal hybridization skills that make it so unpopular with those in the know. Smooth cordgrass grows to nearly twice the size of the native species, chokes off tidal channels and creeks, diminishes the holding capacity of flood control districts, and turns mudflats into salt marshes. It faces fewer habitat limitations than the native species, growing not only in mudflats but also in deep or shallow water.
In eastern and Gulf Coast areas, different conditions exert controls on this plant aggressor, says Strong. Hurricanes and storms regularly knock it out, as described by Casey, and open up space for other plants. And there's a lot more room for it - 70% of the Atlantic coast, but less than 1% of the Pacific coast, is estuarine, says Strong. "The West coast is a young coastline full of cliffs rising out of the sea, where the land marching upward vastly exceeds the rate of erosion," he says. "The Atlantic coast is the opposite, an old low-lying coastline full of estuaries." Strong adds that none of the Pacific coast cordgrass species have evolved to be as aggressive as their Atlantic cousin (more pushy New Yorkers?).
The good news is it's not too late to do something, say scientists. Not widespread yet, the smooth cordgrass invasion is densest on the southeast bayshore - and spreading to such newly restored wetlands as Ora Loma and Whale's Tail marshes - with small outposts in the lower North Bay.
The scale of the problem - the fact that the Spartina alterniflora invasion is still small enough to manage - is key to any eradication strategy for all plant invaders. Indeed, a recently completed year-long CALFED-funded study by the S.F. Estuary Institute of introduced tidal marsh plants offers the first prioritized list of 15 species worthy of further research, monitoring and/or control. The study, conducted by Andy Cohen and Robin Grossinger with input from 33 other scientists, identified Spartina alterniflora, Spartina densiflora and Lepidium latifolium, or pepperweed, as the species of most concern. Species of secondary concern included Spartina anglica, Spartina patens, Salsola soda and Arundo donax, a giant reed that grows in backyards and on the edges of the Bay and is troublesome in creeks, but remains more prevalent in Southern California. Eight other plants are on the report's "Watch List."
Spartina patens or salt meadow grass, another invader from the East Coast, is found in San Bruno and in Southhampton Marsh in Benicia. Humboldt Bay is already saturated with Spartina densiflora, a Chilean species of cordgrass, which grows near the upper margins of marshes, displacing pickleweed. Here at home, densiflora has already made the jump from Corde Madera Creek in Marin County to Point Pinole in the East Bay.
"The political discussion is what needs to happen next; the debate over which is the best approach, and for which plants," says report co-author Grossinger.
According to U.S. Fish & Wildlife's Peter Baye, some of the debate already occurred during development of the sweeping Draft San Francisco Estuary Baylands Ecosystem Goals Project report, released in June in an attempt to provide scientifically sound guidance for future restoration (see June Estuary). The Goals Project favored control of Spartina alterniflora, as well as an effort to eradicate other, less well-established invasive marsh grasses.
The S.F. Estuary Institute's Andy Cohen believes that efforts should focus on getting rid of wetland grasses that have not yet taken hold. "Our greatest priority ought to be to eradicate those exotic plants that are not widespread, while we can do so easily, at low cost and with few harmful environmental side effects, rather than waiting until they become a bigger - and much more difficult - problem."
To this end, the Estuary Institute report recommends, among other things, that immediate efforts be undertaken to eradicate Spartina patens and densiflora while they are still restricted to a few sites; to check if Spartina anglica has yet arrived in the Estuary and, if it has, get rid of it; to consider an eradication program for Salsola soda (a threat to various endangered plants in the Estuary's more northerly brackish marshes); to coordinate control of Arundo donax (with an eye to source populations in the upper watersheds); and to eliminate new and outlying populations of Spartina alterniflora.
Cohen is concerned that committing to a regular program of control for Spartina alterniflora will result in repeatedly disturbing habitat with applications of herbicide or mechanical mowing. Although Rodeo - the aquatic counterpart to RoundUp - appears to be reasonably safe (some questions remain regarding the surfactants that are added prior to application), Cohen says he would not like to see it used "year-in, year-out, forever" in the Bay and Delta. He also fears that funding simply doesn't permit too broad-based an approach.
"When you try to do everything all at once, chances are you'll accomplish little of value," says Cohen. "With that in mind, I look at the situation in the Bay and see that eradicating the uncommon and rare species of exotic cordgrasses will take a tiny fraction of the resources and effort that will be needed to eradicate Spartina alterniflora."
In the meantime, Bay Area agency officials have been in contact with their counterparts in Willapa Bay, Washington, where a debate over herbicide use to control invasive Spartina alterniflora has cost hundreds of thousands of dollars in legal fees and remains largely unresolved (see "Tough Choices." So far, no similar political conflagration over herbicide use has occurred in San Francisco. But concerns over the endangered clapper rail have stalled efforts to spray the herbicide Rodeo during the summer, before the grass spreads its seeds. That delay is frustrating officials like Joy Albertson of the Newark National Wildlife Refuge and East Bay Regional Parks District biologist Debra Smith, who is coordinating her district's Spartina control program.
"It's impossible to control the plant if we're only able to get out there between September 1 and January 31 to avoid clapper rail breeding season," says Smith. "It's been our biggest stumbling block."
Negotiations are underway with U.S. Fish & Wildlife over a memorandum of understanding that would allow spraying during the summer after surveys for clapper rails. But Fish & Wildlife slowed negotiations down this summer pending further study, which meant that Smith and Albertson weren't able to spray.
"We believe our population of Spartina alterniflora doubled last year," says Smith. "My jaw dropped when I saw the aerial photos. I don't think it's death to the clapper rail if we spray. But if we don't, it's death to the marsh."
Clearly, smooth cordgrass' propensity for choking out creeks makes it detrimental to the clapper rail. But the tough, ubiquitous grass also provides cover for the endangered bird. The relationship between clapper rails and Spartina - whether native or introduced - is complex. The equation is not simply that the more native Spartina foliosa you have, the more clapper rails you will have, but a question of where and how Spartina is growing and what else is in the immediate vicinity. For example, slump blocks of Spartina, whether native or introduced, seem to provide good habitat for rails in the middle of stream channels. Eventually, however, Spartina alterniflora behaves differently than Spartina foliosa in streams, effectively choking them and reducing drainage densities.
One place smooth cordgrass doesn't seem to be growing is in the "seed-safe sites" long colonized by Pacific cordgrass, where tall canopies and established native populations are successfully resisting invaders, according to Ayres. This situation could soon change, however. Last winter's El Nino rains and freshwater influx not only created new mudflat areas, but also promoted Spartina seed germination, which may fuel hybridization.
"For now, native marsh may be the best protection we have," she says. "We shouldn't trade native marshes for restored salt ponds in the name of mitigation until we have Spartina alterniflora and the hybrids under control."
There's little else restoration proponents can do. There's no way to design a new wetland to keep out invaders, and no fish-screen equivalent for plants that only lets in the natives. "The good stuff hybridizes with the bad stuff, so you can't tell your enemies from your friends," says East Bay Parks' Joe Didinato. "Unless everyone works together regionally, we'll just be putting out fires in one place and starting them up again elsewhere." "All this dike breaching and ribbon cutting and picture taking with politicians is getting us into a big Spartina mess," says U.C. Davis' Strong. Indeed he, Baye and a newly formed group of scientists and resource managers are considering calling for a moratorium on levee breaching and restoration south of the Bay Bridge until a regionally coordinated attack on smooth cordgrass can be mounted.
"Until then the solution is geographic," says Baye. "We should focus restoration on areas where invasion pressure is low." At the moment, this means the North Bay and the extreme South Bay, according to Baye.
In the meantime, scientists are trying to come up with a more integrated set of tools and plans for ridding the region of this plant pest. According to Strong, all the tools of traditional weed control can be used except competition and biological control (which would impact the natives too). Strong's excited about three different versions of a macerating machine he's seen around the world - basically a big tractor with a beet flailer on the end that chops the offending Spartina to bits. He'd like to rent such a machine and integrate its use with chemicals.
"It's time to stop the organic gardening mode, the backpack sprayer, and stop the Vietnam mode, with helicopters dumping chemicals on everything, and get an industrial-duty macerator on the job to be followed by a light-duty, low-volume herbicide," he says. "We can use these techniques to scorch the earth, so to speak, on a local scale." The scorch approach is necessary given the inability to separate the good grass from the bad and ugly.
Other techniques, according to Baye, may be to reflood or dewater restored areas or to apply vinegar, which may weaken the plant in preparation for other treatments. To pave the way for an integrated regional control plan, concerned scientists plan to hold a workshop on smooth cordgrass on November 18.
The technical and chemical options, not to mention who will champion and pay for any regionwide control effort, are not the only questions on the invasion table. There are greater intangibles lurking in the mud. Protection of native species is almost a religious tenet to biologists, but the pervasiveness and rapid pace of alien introductions may eventually create a number of situations around the country where one is forced to choose one's battles, as Andy Cohen is advising officials to do in the Estuary.
Philip Williams believes that San Francisco could be riven by the same debate now polarizing Washington state, where oyster farmers want to carry out an industrial-strength herbicide-based eradication program of Spartina alterniflora, but, in Williams' words, "There's another group that says, 'hey, relax, this is part of the evolution of the ecosystem.'"
As an Englishman, Williams is acutely aware of another grass super-race, Spartina anglica. This hybrid was born in the 1870s, when steamships carried Spartina alterniflora across the Atlantic to England, where it crossed with an English Spartina species to create a sterile hybrid - and then became fertile through internal genetic change, creating Spartina anglica. Now anglica has moved across the Channel to France and "it's basically a new species, and it's creating a new habitat," says Williams. Whether or not eradication becomes a political issue, it's a fairly safe bet that the next decade will decide the question of whether Spartina alterniflora and most of the other alien invaders become permanent fixtures in the Estuary's marshes, mudflats and creeks. "There's a grim admiration you get for these kinds of species," says Baye. "It's evolution at work." Don Strong disagrees. "Invasive species homogenize the world, so it's not really evolution, it's extinction."\
Contact: Debra Ayres; Peter Baye (707)562-3003; Andy Cohen (510)231-9539; Debra Smith (510)635-0138; or Don Strong (707)875-2022
Special thanks to U.S. Fish & Wildlife's Coastal Ecosystem/San Francisco Bay programs for providing supporting funds to ESTUARY for research on this story.
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