Editor’s Note: Call to Earth is a CNN editorial series committed to reporting on the environmental challenges facing our planet, together with the solutions. Rolex’s Perpetual Planet initiative has partnered with CNN to drive awareness and education around key sustainability issues and to inspire positive action.

CNN
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Barbara Boissevain’s photographs have been compared to the work of American painter Mark Rothko, for their blocks of deep reds, oranges, pinks and greens. But these shades are not mixed on a palette, they are unfiltered snapshots of San Francisco Bay’s salt ponds.

Taken over more than a decade, the images document the restoration of the area, from a center for commercial salt extraction back to its natural state of tidal marsh, mudflats and other wetland habitats. The ongoing South Bay Salt Pond Restoration Project, which launched in 2003 after acquiring land from global food corporation Cargill, aims to restore more than 15,000 acres of salt ponds – an area roughly the size of Manhattan.

The rich, unnatural colors in Boissevain’s early photos are a result of the water’s salinity. She explains that Dunaliella salina, an alga that produces beta-carotene, a red-orange pigment present in carrots and pumpkins, thrives in salty environments. So do rosy-colored halobacteria, and then there are the brine shrimp that eat the algae and amplify the vibrant tones.

During restoration, the man-made levees built to trap water for harvesting salt are gradually removed, allowing the tidal systems to infiltrate once more. With this the colors fade, as shown in the photos. “Those dramatic oranges, reds, purples, slowly evolve into greens, deep blues, and brown,” she tells CNN, adding that “green ribbons of life” seep back into the ponds.

Although perhaps less photogenic, the shift is a positive sign, says Dave Halsing, executive project manager of the South Bay Salt Ponds Restoration Project. “Our goal is to get rid of those bright colors, as they are remnants of the hypersaline waters left from the salt making days,” he says.

By doing so, the hope is that wildlife will come flooding back to the area, from endangered salt marsh harvest mice to migratory shorebirds and waterfowl, or fish such as leopard sharks and steelhead.

Salt and silicon

The Bay Area’s history of salt making dates back to the Ohlone, Native American people who collected salt from naturally occurring tidal pools. After the arrival of European colonizers in the 1800s, the process was industrialized, starting with a number of small-scale operations and then giants such as Cargill taking over. At its peak, salt ponds covered around 36,000 acres throughout the Bay. Today, Cargill still operates 12,000 acres of salt ponds, capable of crystallizing half a million tons of sea salt each year.

Boissevain grew up in the area, and still lives there today with her two daughters. She remembers visiting the salt ponds for the first time during a science class in third grade. It was only years later, in 2010, when she was flying over them in a helicopter on the way to another photo project that she saw how they looked from above.

“It was visually spectacular,” she says, and at that moment she decided to track the bay’s restoration over a long period. She started by going up in the air once a year to photograph the salt ponds. Then Covid-19 hit, and unable to take a flight, she began to experiment with shooting from ground level and even underwater.

Her recent book, “Salt of the Earth: A Visual Odyssey of a Transforming Landscape,” compiles all these different perspectives, allowing the viewer to see the extent of the damage to the landscape, and the beginnings of its transformation.

The restoration of the area is particularly poignant when juxtaposed with the mass development of Silicon Valley that surrounds it. In Boissevain’s photos of Ravenswood salt ponds, on the edge of Menlo Park, the headquarters of Meta (the parent company of Facebook and Instagram) loom large on the horizon. It looks almost dystopian, she says, and reflects the dissonance between man and nature.

However, today wildlife is reclaiming the space. The restored ponds and man-made nesting islands provide shallow water habitat that attracts hundreds of foraging shorebirds and ducks.

The number of birds is astonishing, says Boissevain: “They’re screeching and partying out there. I chose to dedicate the book to shorebirds, because they’re so fabulous and seem really happy to have this habitat back.”

Situated along a migratory route known as the Pacific Flyway, the Bay Area provides a critical stopover for birds as they travel between breeding and wintering grounds, as well as year-round habitat for shorebirds. Halsing notes that Ridgway’s rail, a species classified as a “near-threatened,” has moved in and is nesting in the area. Populations of native estuarine fish have also increased, he says.

Aside from wildlife bouncing back, the conversion of former salt ponds to tidal marsh will bring other benefits, such as flood defense as sea levels rise. “Marshes absorb and disperse water and energy from high tides, storm surges, wind waves,” he says. “They also absorb large amounts of carbon dioxide and help reduce greenhouse gas concentrations in the atmosphere.”

Another upside is for those living in the surrounding area, like Boissevain. “Since I was a small child, the population (of the area) has increased dramatically. It’s so much denser,” she says. “Giving people places to enjoy natural spaces is extremely important for mental and physical health.”

The public can access the area via a network of trails and viewing platforms. By bringing people in contact with nature they are more likely to realize its value. However, Halsing urges visitors to respect wildlife and not trespass into sensitive habitats for endangered species. The restoration project’s website notes that some areas have become popular selfie spots, causing people to invade nesting areas for Western snowy plovers, while others fly drones that disturb wildlife.

Raising awareness of the need to preserve our natural spaces was a key motivation for Boissevain. She recalls her photography professor David Maisel at San Jose State University, who spoke about the “apocalyptic sublime” and the goal of drawing people into a photograph with beauty and then shocking them with the reality of what they’re looking at.

With the striking images of the salt ponds, this is what she is trying to do. “As a photographer, visually we’re competing with a lot of saturation of images. The average viewer is inundated with images on their social media, on the sides of buses, everywhere around them. And so you’re always looking for ways to startle people and bring their attention to something important,” she says.

“This was why this was an opportunity. Because they were so visually striking, it did cause people to notice.”