Marsh Matters

Large swaths of salty water, expansive patches of olive green brush, and bending trails of sloughs buzzing with life make up Suisun Marsh in the northeast corner of the San Francisco Bay. Part of the Pacific Flyway, thousands of birds flock here annually, and over 200 birds call it home year-round. Years upon years of accumulated silt and tides have formed this tidal marsh—the largest on the West Coast.

But since the 1970s, an invasive species has encroached on the marsh’s delicate balance of water, flora, and fauna. Sky-high green reeds called Phragmites australis have increased by 200% over the past 20 years in spite of attempts to control and remove the plant.

The pervasive nature of this plant and its threat to the future of Suisun Marsh has led to a joint effort between researchers and faculty from Santa Clara University, Utah State, Purdue, and Chapman universities, and Suisun Resource Conservation District to combat the issue. The organizations were awarded $968,826 by the Delta Stewardship Council to fund the study. The chair of Santa Clara’s Department of Environmental Studies and Sciences, Virginia Matzek, is leading the project at SCU.

“We have a lot of salt marshes on the Pacific coast, but this one, because of all the fresh water flowing down from the Sacramento and San Joaquin rivers, is more brackish and much more freshwater-influenced than the other salt marshes,” Matzek says. “So it has a really unique kind of species composition and role in the ecosystem in terms of being a nursery for important fisheries.”

Suisun Marsh supports diverse wildlife ranging from fish and reptiles to mammals as large as a 550-pound tule elk and as small as a seven-centimeter endangered salt-marsh harvest mouse. Phragmites threatens the animals by pushing out key native plants that sit at the center of much of their food chains. The reeds also take away necessary materials for some birds’ habitats.

Phragmites has also spread across the region’s coastlands, clogging up waterways and drastically altering the landscape. Further complicating matters: Control of the marsh is split between the California Fish and Wildlife department and several hunting clubs. This creates a lack of cohesion in efforts to contain invasive species, which obviously stalls progress. Some local land owners have taken it upon themselves to remove the reeds, but their efforts—though well intended—are drops in the bucket. 

The project is also searching for ways to streamline the fight against phragmites and, hopefully, come up with new containment solutions. With Purdue and Chapman universities working on the social side of the phragmites issue by interviewing stakeholders on what motivates or prevents them from taking action against the reeds. “We’re not just looking at the ecology of it, but we’re also looking at the social side of things,” Matzek says. “The reason this is really important with invasive species issues is that whether people participate or don’t participate in a program to control invaders matters a lot as to whether you can be effective with control.” 

Postdoctoral fellow Adrienne Ernst at Utah State University says phragmites is really good at taking up nutrients, which can leave the marsh waters denatured for other plants. “There’s a lot of efforts to control phragmites, but there’s not a lot of efforts to restore habitat,” Ernst says. So even if the spread of invasive species is stymied, no other species are being introduced to the marsh. “Nature abhors a vacuum and it kind of perpetuates more invasive species coming in,” she says of what can happen if good plants aren’t brought back in the bad ones’ wake.

In order to combat this, revegetation and the effectiveness of control methods like herbicides are being put to the test. Specifically, the team is considering planting native seeds favored by ducks as well as native plants that are more resistant to increased salinity and drought. 

“It’s a really tough environment to work in,” Ernst says. “The Santa Clara students that we’ve worked with have just been fantastic. It’s a lot of rough conditions, it’s tough carrying a lot of heavy stuff across the marsh. … It’s been harder than I thought to get the native plants established. I think I just have a lot more respect for the land managers out there and everything that they’re doing to take care of the landscape.”

Santa Clara seniors Michael Weatherford ’23 and Gabe Rodkey ’23 are studying herbicide resistance in phragmites. They’ve begun examining seed samples in order to discern whether the level of herbicide control has affected seed production as well as how much of the species is spreading through seeds since phragmites can reproduce through roots in addition to seeds. 

“I think [this study’s] important because it’s just something that we don’t know,” Weatherford says. “We didn’t know when [the plant] was even going to produce seeds, because no one had looked at that yet and so that was something that we had to find out.”

Even though Weatherford will graduate before the study ends, as a scientist he knows how paramount it is to accumulate as much information as possible. He’s glad to be contributing even a little to a new understanding of phragmites and a new approach to its containment.

“The important thing is just trying to learn as much as possible and I also hope that it will help control the species,” Weatherford says. “We don’t really know what [our study is] going to do. But what this research will be able to do, what I hope it’ll do, [is] help someone at least in some measurable way.”