Estuary News

October 2021

Invasive Species Breakdown

The invasion of the Delta continues, with new plants and animals threatening to upend ecosystems alongside established non-native species like largemouth bass and spartina. Preventative measures, early detection, and rapid response to novel threats are all key in protecting the Delta from further disruption.

But the concepts of community involvement and reconciliation ecology also encourage land managers to consider non-natives with nuance. This means accounting for the cultural and ecological values of invasive species and, in some cases, learning to accept their presence on the landscape while still prioritizing natives.

These were among the takeaways of the Estuary Summit’s lunchtime breakout discussion of invasive species in the Delta (one of seven breakout sessions, on topics ranging from water quality to eelgrass restoration, held during breaks in the conference).

Moderator Rachel Wigginton, senior environmental scientist with the Sacramento-San Joaquin Delta Conservancy, opened the session with a survey of attendees, most of whom represented state and federal agencies. Which currently invasive species are of most concern? Their names may roll off the tongue, but they are not welcome: nutria, spartina, phragmites. And which potential invaders are of most concern? Participants cited hydrilla, zebra mussel, and the newly infamous lanternfly. (“Lanternflies must have a good press agent; I feel like we’ve all been hearing about them lately,” said Wiggington.)

Vigilance is key, but invasion ecology is not a black-and-white field. “Some communities may value some of the impacts that invasive species may have,” noted attendee Louise Conrad, deputy executive director of the Delta Stewardship Council’s Delta Science Program.

Largemouth bass constitute an important recreational fishery, and even invasive submerged plants are valued for providing them with refuge and rearing habitat. The aggressive wetland grass phragmites (common reed) supports critical soil accretion that can help marshes keep pace with sea-level rise.

While some invasives can be blocked or eradicated, others, like them or not, aren’t going away. “We have many species that are really here with us to stay,” Conrad said. “We’re not going to be able to eradicate them, and we have to make choices about where we spend our resources.”

This, she noted later in an interview, gets back to the notion of reconciliation. Some invasive species we can never get rid of — but others, like the aforementioned South American rodent, we should stop before they get that far. “We should still be proactively positioning ourselves to fight against new invaders that may be coming into the system,” Conrad says. “In some cases, for example nutria, we should be ready to move into eradication, and not resign ourselves to them coming in.” NS

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About the author

Nate Seltenrich is a freelance science and environmental journalist who covers infrastructure, restoration, and related topics for Estuary. He also contributes to the San Francisco Chronicle, Sonoma and Marin magazines, the journal Environmental Health Perspectives, and other local and national publications, on subjects ranging from public lands and renewable energy to the human health impacts of climate change. He lives in Petaluma with his wife, two boys, and four ducks.

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