Waterline is an ongoing series that explores the solutions making rivers, waterways and ocean food chains healthier. It is funded by a grant from the Walton Family Foundation.
Water may be life, but without salt, the human body cannot retain its benefits. And for thousands of years, a stretch of coastline south of San Francisco has been a vital source of salt.
The South Bay Salt Ponds, as they’re now known, were once thousands of acres of thriving tidal marsh, which formed a natural barrier against regional flooding and provided an important stopover site for migratory birds and habitat for estuary-dwelling flora and fauna. The Ohlone peoples historically harvested salt from the area’s natural deposits, a resource later exploited first by German immigrant John Johnson in the mid-1800s and then by salt-harvesting companies including Cargill, which still operates in the area.
Today, saltwater evaporation ponds sprawl across the area, forming a man-made waterscape that resembles an artist’s palette — courtesy of saline-loving microorganisms that give each pond its richly saturated hue.
But their initial goals — creating and maintaining essential habitats, reestablishing buffers against climate-change induced sea-level rise and regional flooding, and creating more spaces for public recreation — are all well underway. After a century and a half of use as a privatized corporate resource, turning this terrain back into a natural ecosystem benefits all its inhabitants, human and non-.
What with their 50-year timeframe, the leaders of the restoration project are taking a holistic, long-term approach, recognizing that there are no one-size-fits-all solutions to a project of such scale and magnitude. Theirs is a strategy of “adaptive management,” which the project website defines as “treating our actions as scientific experiments, and changing what we do based on the lessons that we have learned.”
“It’s just learning, and applying what you learn,” Dave Halsing, the executive project manager, puts it. “People used to think that we could just create the exact system we wanted in nature,” but “these are complex systems with a lot of uncertainty and a lot of variability, and humans have short memories so we don’t always get things right.” So the idea, he explains, is to “do things in a risk-averse, fairly conservative way … track it, and make adjustments as we go.”
Adding further complexity, the project’s scope covers three discrete areas: Eden Landing located near Hayward and Union City, Alviso in Santa Clara County, and Ravenswood in Menlo Park. After acquisition of the land in 2003 and a prolonged planning process — during which a 140-plus page Adaptive Management Plan was created to guide the restoration efforts — construction officially began in 2009 to 2010. These initial actions included creating “nesting islands” in certain of the Alviso and Eden Landing ponds, breaching and lowering levees in other areas of Alviso to kickstart revegetation and regrowth of tidal marsh, and joining previously unconnected parts of the San Francisco Bay Trail between Sunnyvale and Mountain View.
For example, because of the region’s long history of salt production, the buildup of gypsum in the ponds was in some places up to 18 inches thick. According to the project’s lead scientist, Donna Ball, this raised concerns regarding revegetating the area. But happily, Ball emphasizes, “it turned out that once we let the water in and sediment in that it wasn’t a concern at all… the plants established [themselves], and we have marshes that are doing great that were 12 inches deep of gypsum.”
Similarly, Halsing recalls, legacy mercury deposits from gold mining endeavors were found to be much less harmful to the emergent salt marshes than anticipated. By trialing a series of tide gates that could be opened slowly and partially while the surrounding waters were monitored, the project’s researchers discovered that although there was an initial spike in mercury levels, it quickly dissipated. This resulted in many happy side benefits, including natural sequestration of the mercury beneath the accreting sediments and a path forward to fast-track reclamation of other mercury-contaminated ponds in the area without facing a mass die-off or other dire consequence.
Of special consideration is balancing the needs of migratory and native bird populations that call on the area for feeding and breeding. This includes restoring certain areas to wetlands and keeping some of the man-made salt ponds as such in order to continue supporting birds that rely specifically on them. Laura Cholodenko, a project manager with the California Coastal Conservancy, describes this as a “juggling act,” explaining that “when we convert from managed pond to tidal marsh, we’re taking away this habitat that these shorebirds and ducks have come to really count on.”
Among those shorebirds are nesting snowy plovers. Though they typically prefer sandy shores, they’ve adapted to favor the South Bay salt pans, which offer them protection from predators and human interference. The birds are federally listed as threatened, but there’s hope that they will find the stability they need in the South Bay to make a comeback. One particularly interactive method of supporting these fragile shorebirds is a “mud stomp,” a volunteer effort Cholodenko recently took part in at Eden Landing Ecological Reserve. This involved a group of participants “stomping” depressions into the mud and scattering oyster shells to further camouflage soon-to-be-nesting snowy plovers, who tend to lay their eggs not in elaborate nests but in shallow depressions of mud, salt or sand.
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Our smart, bright, weekly newsletter is the uplift you’ve been looking for.Other species being prioritized by the project are the endemic salt marsh harvest mouse, and the long-legged, long-billed Ridgway’s rail – both officially listed as endangered. This is an area where that careful juggling act becomes evident, as federally endangered species come with their own set of protection parameters that cannot be disregarded by even the most well-meaning project. For example, Cholodenko points out, the need to reserve certain areas for these species pushes the public access trails “to the perimeter” to minimize disruption. These protective measures appear to be effective. In 2014, Ridgway’s rails were found inhabiting newly created tidal marsh in the Alviso restoration zone, joined in 2015 by the first sighting of salt marsh harvest mice in the same area.
But wetlands provide more than a refuge for cute rodentia and rails. As Halsing notes, tidal marshes are hugely productive sources of nutrients for a host of micro- and macro-organisms that themselves become food all the way up the chain. They’re also excellent at sequestering carbon and toxic materials such as mercury. Furthermore, salt marshes form a natural barrier against higher water levels — an especially important consideration in the low-lying Bay Area, where sea levels are projected to rise four to eight inches by 2050. In a prime example of a nature-based solution to a human-engineered climate crisis, wetlands act like giant sponges, soaking up and slowing down floodwaters, urban runoff and storm surge.
The built-in flexibility of the project means that its goals can shift over time. While the project’s Adaptive Management Plan calls for up to 90 percent restoration of the 15,000 acres to tidal marsh, it allows for this target to shift lower based on other factors. Halsing estimates — with the caveat that this decision is many years from being definitively made — that the project will likely restore around two-thirds of the total project area to wetland, while keeping other areas as managed salt ponds of varying depths, areas for public access and other possible uses. This ability to adapt is key to a plan that relies on trial phases, regular monitoring and occasional serendipity.
As one of the authors of this original plan, Donna Ball is now working collaboratively with Halsing to “adapt the adaptive management plan” to reflect the current science and data gathered over the past 20 years of restoration work. One positive development that she’s witnessed over the past 10 years is the emergence of a general understanding among a broad spectrum of organizations and scientists that working together on regionally specific environmental issues, including the impacts of sea-level rise, is the best way to achieve their individual goals going forward.
The idea of a project that takes 50 years to implement feels a little daunting from the outside — not all of us reading (and writing) about the project today will be around to mark its completion. But for Ball, who’s spent a large part of the last 20 years engaging with this project, this sense of long-term legacy is one of the reasons she’s motivated to continue with it.
“One saving grace of [the] salt production ponds being in place … is that that land was preserved in some form even if it was for salt production,” she says. “And now we have a chance to restore it.” And beyond the ecological benefits of wetlands, she adds, “I also think it’s gonna be awesome for people and they don’t realize it. I’ve brought people out to the edge of the Bay and they’re like, ‘Oh my god, I didn’t know this was here … this is wonderful.’ And that’s really inspiring to me.”
Scrolling image credits: First set by Cris Benton. Second set by Charles Anderson. In the third set, the first image is by Dave Halsing, and the other two are by Ivan Parr.
