Here’s the dilemma. The California clapper rail, a bird found only in the San Francisco Bay Area, has lost most of its native habitat and has become dependent on the very species of plant that has played a part in eliminating the bird’s natural nesting ground.
Now, getting rid of the invasive plant, a salt marsh cordgrass known as Spartina, could further endanger the clapper rail. What’s a resource manager to do?
That’s the question researchers at UC Davis explored. Their written conclusions will be published Friday, May 30, in the journal Science.
The conclusion is that instead of moving swiftly with eradication and restoration, the best approach is to slow down the removal of the invasive species and allow a natural recovery system to take root and grow.
“Just thinking from a single-species standpoint doesn’t work,” says Alan Hastings, co-author of the study and a UC Davis environmental science and policy professor. “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 that balances conflicting management goals, including endangered species recovery and invasive species removal, given budgetary constraints.
While more threatened and endangered species are becoming dependent on invasive species for habitat and food, conflicts have been rare. However, researchers believe they will increase. The only other known case where the eradication of an invasive species threatened to compromise the recovery of an endangered one is in the Southwest, where a program to remove an invasive tree, tamarisk, was halted in areas where the endangered southwestern willow fly-catcher was nesting.
“As eradication programs increase in number, we expect this will be a more common conflict in the future,” says Ted Grosholz,co-author and UC Davis professor.
The scientists used data from Grosholz’s lab as well as from the Invasive Spartina Project of the California Coastal Conservancy in their analysis.
Spartina alterniflora was introduced to the San Francisco Bay in the mid-1970s by the Army Corps of Engineers in an attempt to reclaim and preserve marshlands. Things went amiss when the Spartina hybridized with native Spartina and spread, taking over the marshes and pushing out native plants. Eradication of hybrid Spartina began in 2005, and about 92 percent of it was removed from the Bay. Invasive Spartina also has been spotted and removed from Tomales Bay, Point Reyes and Bolinas Lagoon. The cordgrass also has invaded areas of Willapa Bay in Washington state, where efforts to eradicate it are nearly complete.
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.
Co-authors include UC Davis environmental science and policy professor James Sanchirico and Sunny Jardine, a Ph.D. student at UC Davis during the study and currently assistant professor at University of Delaware.
Alan Tessier, program director in the National Science Foundation Division of Environmental Biology, praised the study as being “significant in advancing a general, analytical framework for cost-effective management solutions to the common conflict between removing invasive species and conserving biodiversity.”
You can watch a video about the study here.