The Battle for Native Cordgrass

Invasions Further Selections



Treatment near Bair Island with airboat. Photo: Drew Kerr, ISP
21
Mar

The Battle for Native Cordgrass

Now in its 17th year of monitoring and treatment, the San Francisco Estuary Invasive Spartina Project remains a uniquely ambitious invasive plant removal effort: from its timeline (indefinite) and size (covering 70,000 acres with more than 150 landowners and managers) to its budget (about $50 million to date) and use of technology (genetic testing, GIS, airboats, helicopters). It’s been an effective one, too, reducing stands of invasive cordgrass in the region to a tiny fraction of what they once were. “We are excited at the continual progress over two decades, even with all the permitting and pandemic challenges,” says project manager Marilyn Latta of the California State Coastal Conservancy, which manages the Invasive Spartina Project (ISP) in partnership with the...
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08
Aug

Invasive clams and freshwater exports from the Delta have created dramatic and unsustainable changes in the San Francisco Estuary’s foodweb over the past 50 years.

 A study by UC Davis researchers found a 97% decline in phytoplankton, the microscopic foundation of the food chain. “Understanding the causes for the decline in the pelagic [water column] community is essential so that efficient solutions can be implemented,” says Bruce Hammock, a research scientist at the UC Davis School of Veterinary Medicine’s Aquatic Health Program. The invasive clams (Potamocorbula amurensis), originally from Asia, have been over-consuming phytoplankton and zooplankton for more than 30 years, and have long been understood to account for part of the fish population’s decline; the new study investigated the additional effects of exports. Beginning in the 1940s, fresh water from the Delta has been pumped by the federal Central Valley Project and the State...
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02
May

Nutria — giant South American rodents—are breeding in the San Joaquin Valley and are on the brink of invading the Delta, where they could wreak havoc, as they have done in Louisiana, Chesapeake Bay and the Pacific Northwest.

According to the California Department of Fish and Wildlife, nutria have extremely destructive feeding habits that often lead to severe soil erosion, in some cases converting marsh to open water. Nutria also burrow into banks and levees, creating complex dens that extend as much as 6 meters deep and 50 meters into the bank, often causing severe streambank erosion, increased sedimentation, levee failures, and roadbed collapses. The rodents, which can weigh more than 20 pounds and are often mistaken for beavers or muskrats, were introduced to California for the fur trade in the early 20th century, but were eradicated by the 1970s. In 2017 a reproducing population was discovered in the San Joaquin Valley and nutria have now been confirmed...
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13
Dec

Table Set for Snails

Several months ago, Mike Moran of the Delta’s Big Break Regional Park got a call about a cluster of unusual looking eggs. “We thought we might be looking at this channeled apple snail thing,” he says.
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13
Dec

Searching for a Few Good Weevils

“They’re pretty charismatic,” says Julie Hopper of the tiny herbivorous weevil N. bruchi. Native to Argentina, these weevils were first brought to North America to combat the spread of the invasive weed water hyacinth.
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21
Sep

Teachable Moments

The Ocean 102 lab at Diablo Valley College in Pleasant Hill is a proper marine biological laboratory. It smells faintly of seaweed and formaldehyde, while fearsome, plastic versions of marine predators hang from the ceiling. The Peterson benthic grab, a heavy jaw-like affair attached to a long rope sits in the supply room.
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28
Oct

Fish Down, Invasions Up, Flooding Soon

Whether you’re a fat salmon or a skinny smelt, life in the watershed of the San Francisco Estuary remains far from “natural.” Dams and levees block Estuary fish, alien clams compete for fish food, invasive weeds clog habitats, and exotic predators threaten life and fin. A few native species are holding their own, but others, like Delta smelt, have declined to such a degree that there are too few to count. Clearly, we have failed to stem the decline and ensure the recovery of native fish as we set out to do twenty years ago.
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invasions collage
01
Jan

Editor’s Pick Invasions Stories 1993-2013

Walk back through time with this selection of early stories from Estuary's first two decades of publication. Stories explore the impacts of overbite clams, water hyacinth and mitten crabs, and later follow legislative efforts to control ballast water discharges and eradicate Atlantic cordgrass and hybrids, among other initiatives.
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