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Scientists face endangered species conundrum

Bay Area marsh bird at nexus of endangered and invasive species

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A clapper rain along the shore of San Francisco Bay. Photo via USFWS.

Staff Report

FRISCO — Conservation biologists in the San Francisco bay area say they’re facing a conundrum, as they try to remove an invasive salt marsh grass while recovering an endangered bird that has come to rely on the non-native plant.

In a study published last month in the journal Science, researchers at the University of California, Davis said that an all-out push to eradicate the marsh cordgrass could hamper efforts to recover the clapper rail, a bird on the brink because of urban development and loss of wetlands.

Their results showed that, rather than moving as fast as possible with eradication and restoration, the best approach is to slow down the eradication of the invasive species until restoration or natural recovery of the system provides appropriate habitat for the endangered species.

Scientists in the southwestern U.S. have faced similar issues as they try to remove invasive tamarisk, which has come to provide habitat for rare southwestern willow flycatchers.

“Just thinking from a single-species standpoint doesn’t work,” said co-author and UC Davis environmental science and policy professor Alan Hastings. “The whole management system needs to take longer, and you need to have much more flexibility in the timing of budgetary expenditures over a longer time frame.”

The scientists combined biological and economic data for Spartina and the Clapper Rail to develop a modeling framework to balance conflicting management goals, including endangered species recovery and invasive species removal, given budgetary constraints.

“As eradication programs increase in number, we expect this will be a more common conflict in the future,” said co-author and UC Davis professor Ted Grosholz.

The hybrid non-native cordgrass was introduced to the San Francisco Bay in the mid-1970s by the Army Corps of Engineers as a way to reclaim marshland. It hybridized with native Spartina and invaded roughly 800 acres.

Eradication of hybrid Spartina began in 2005, and about 92 percent of it has been removed from the Bay. The cordgrass has also invaded areas of Willapa Bay in Washington State, where efforts to eradicate it are nearly complete, and invasive Spartina has been spotted and removed from Tomales Bay, Point Reyes and Bolinas Lagoon in California.

The study, led by UC Davis postdoctoral fellow Adam Lampert, was funded by the National Science Foundation Dynamics of Coupled Natural and Human Systems Program.

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