Large blooms of algae in the water
ELKHORN SLOUGH: Agricultural runoff can cause bright green algal blooms in areas of restricted tidal flow. © Kiliii Yuyan

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Between Land and Sea

The tidal wetlands of California’s Elkhorn Slough are flanked by development but remain rich habitat for marine life.

August/September 2016

No observer would confuse this tidal backwater with untrammeled wilderness. But Elkhorn Slough (pronounced “slew”), a serpentine 7-mile-long estuary that cuts inland between Santa Cruz and Monterey, offers some of the richest wildlife habitat in North America, an extraordinary confluence of land and sea. It’s one of the few places in the world where a visitor can spot the dorsal fins of leopard sharks while standing in the shade of a live oak.

Bobcats and coyotes prowl the slough’s uplands, and young halibut and sole thrive in its shallows. The harbor seals now lounging on these sun-drenched mud flats spend their evenings feasting on squid in the Monterey Canyon, an offshore submarine trench that rivals the Grand Canyon in size. A half-dozen sea otters backstroke across the glassy surface, apparently unbothered by a fleet of kayakers.

Mark Silberstein, executive director of a local conservation group called the Elkhorn Slough Foundation, wanders down to the water’s edge, his boots squelching in the mud. “You look around at all this infrastructure: power plants, rail lines, residences, farms,” says Silberstein, who joined The Nature Conservancy as its Elkhorn Slough volunteer coordinator in 1983 before moving to the foundation a year later. “But you also get these incredible concentrations of wildlife. How do you balance the human element with those natural values?”

That balance is most tenuous where the slough’s ecosystem intersects with Monterey County’s agricultural industry, worth more than $4 billion per year. Fertilizers from farm fields in Elkhorn’s 45,000-acre watershed—as well as from the nearby Salinas Valley, where most of the nation’s salad greens are grown—often end up in the slough, where the excess nutrients create low-oxygen conditions that can kill or slow the reproduction of fish and invertebrates. “Some of the fertilizer concentrations on these mud flats are as high as you’d have on a farm field,” says Kerstin Wasson, research coordinator for the 1,700-acre Elkhorn Slough National Estuarine esearch Reserve (ESNERR).

To reduce runoff, conservationists have spent decades restoring the steep-sloped farmland that surrounds the upper estuary. Since 1971, the Conservancy and its partners, which include the Elkhorn Slough Foundation, ESNERR and the California Department of Fish and Wildlife, have protected more than 6,500 acres, nearly 15 percent of the slough’s watershed. Their efforts have paid off. Water quality in some marsh pockets has improved by 70 percent, and the uplands are now patrolled by gray foxes and mountain lions. Today the slough harbors the California coast’s densest concentration of southern sea otters, furry engineers that are restoring salt marshes and teaching scientists new lessons about how coastal ecosystems function.

In a landscape that sees as many uses as this slough, lockit-up-and-leave-it conservation isn’t always the best option. As the estuary’s advocates have learned, agriculture can often be part of the problem—but under the right circumstances, it can also be part of the solution.

“One of the great challenges of this century is the need to practice conservation on working landscapes,” Silberstein says. “In some ways, this place is a giant experiment.”

Man with binoculars sits on boat and looks toward horizon
Otter Spotter Ron Eby, a retired naval officer-turned-citizen scientist, has spent thousands of hours observing sea otters at Elkhorn Slough. © (c) Kiliii Fish Photography

People have been thriving around Elkhorn Slough since the Ohlone Indians began hunting geese and gathering shellfish there as long as 10,000 years ago. The landscape changed significantly in the 19th and early 20th centuries, as Mexican ranching families came to graze cows and sheep, whalers built plants to process cetacean carcasses, and oyster farmers cultivated non-native bivalves by the bushel. The biggest transformation of all came in 1947, when the U.S. Army Corps of Engineers carved a new channel at the slough’s mouth to create Moss Landing Harbor, inadvertently exposing the estuary to dramatic tides that eroded marshland.

Over the decades, the slough proved fertile ground for scientific discovery. Ed Ricketts, the biologist who inspired “Doc” in John Steinbeck’s novel Cannery Row, browsed its marshes for specimens. Elkhorn’s denizens include oddities like the fat innkeeper worm, a juicy pink invertebrate whose burrows also shelter fish and crabs.

“This is a place of discovery, of marvels and mysteries,” says Diane Porter Cooley, who grew up on the Porter Ranch near the slough’s upper end. Cooley—Elkhorn Slough’s “fairy godmother,” according to Silberstein—is a marvel herself, an indomitable community leader whose white hair spills out from beneath a rakish cowboy hat. Her connection to the region runs deep: Cooley’s great-grandfather, a customs officer named John T. Porter, bought Porter Ranch in 1864, and she grew up riding horses on its grasslands and rafting in the slough when floodwaters lapped at the property.

Cooley may be a California cowgirl, but it was her move to New England that changed Elkhorn Slough forever. In 1960, Cooley and her husband, Don, temporarily relocated to Connecticut. Searching for nearby hiking spots, the couple discovered the Mianus River Gorge, site of the Conservancy’s first-ever land purchase in 1955. Diane Cooley had never heard of the Conservancy, but when she talked to the gorge’s caretaker, the idea of purchasing land for conservation struck a chord. “I thought, ‘This outfit might be just the thing—they need to open a California branch!’” says Cooley.

Though her father initially dismissed the Conservancy as a bunch of “butterfly catchers,” her mother was enthusiastic from the get-go. Starting in the 1970s, the family began donating land and granting conservation easements to the Conservancy, ultimately totaling more than 300 acres of their ranch, from low-lying marsh to oak-dominated woodlands. Much to Cooley’s delight, the Porter Ranch’s protected acres still support livestock. Grazing by a local rancher’s herd helps suppress weeds and encourage native grasses in what Kim Hayes, the Elkhorn Slough Foundation’s stewardship director, calls “one of the highest-quality coastal grasslands in the area.”

Over the decades, the Conservancy’s holdings in the Elkhorn Slough watershed grew, eventually encompassing more than 850 acres. But it soon became clear that “these lands needed a strong local presence,” says Laura Smith, the Conservancy’s former Monterey project manager. In 1992, the Conservancy began paying the Elkhorn Slough Foundation to manage these properties, with the goal of eventually handing over the acres to its partner altogether.
After years of negotiation, the Conservancy transferred all its local holdings, with the exception of a small pocket of Porter Ranch woodlands, to the foundation in September 2012. Fittingly, the ceremony was held on the  front lawn of Cooley’s childhood home, a 19th-century ranch house that the foundation hopes to eventually turn into an educational center. For Silberstein, the transfer represented the culmination of three decades of building relationships with both people and land; it was hard not to get emotional. “The Conservancy created a culture of large-scale land protection and restoration in Elkhorn Slough, and we’re caring for its legacy,” he says. “The seeds they planted have sprouted.”

sea otter floats on its back in the water
Small But Mighty Data collected by volunteers have helped biologists better understand how the southern sea otter, a threatened species, uses the slough and plays a key role in its ecosystem. © Kiliii Fish

On a hazy afternoon, Silberstein drives up a rutted dirt road to the Sand Hill Farm, a 107-acre property with a 60-acre strawberry patch whose slopes run toward a tidal marsh stalked by sandpipers. Though the foundation bought and restored an adjoining 100-acre parcel of the farm’s upper reaches more than a decade ago, this part stayed in production until the foundation was able to negotiate its purchase last year. Heavy rains have torn through the fallowed terraces, washing out gullies and piling up shoulder-high dunes. Shreds of black plastic, a lining that farmers use to retain water and suppress weeds, sprout from the sand like a strange crop.

Turning the whole property over to nature would surely be the simplest approach. Yet Silberstein’s team intends to keep the flattest part in production. The foundation, as it often does, will lease land to an organic grower whose practices won’t harm the estuary. “Retaining some portion of these lands for agriculture is important—it brings in some revenue, and it ensures there’s someone keeping an eye on the land,” Silberstein says as he plucks a luminous strawberry off a sand-spattered plant. “But most important is that it links us to the agricultural community.”

The foundation’s belief that agriculture can coexist with a healthy estuary is already bearing fruit at the Blohm Ranch, the “after” to Sand Hill’s “before.” At Blohm, the road jounces through undulating bunchgrass meadows and low-lying coyote brush, a textbook swatch of California coastal prairie. Silberstein navigates past a willow-lined stream, a site that hosts threatened California red-legged frogs and the most diverse collection of passerine (perching) birds in the watershed. Without his narration, it would be impossible to tell that this 337-acre property had been terraced with strawberries before the Conservancy purchased it in 1990.

But the Blohm Ranch isn’t just grasses and shrubs. Atop the hill, a curtain of gnarled live oaks gives way to a sweeping expanse of furrowed earth—a strawberry and bushberry field rented out to an organic farmer. In the distance, an expanse of pickleweed, the marsh’s ubiquitous plant, blushes an autumnal red. Below the farm, Silberstein says, a chain of landscaped basins captures runoff, preventing sediment from reaching the estuary. “It used to be literally a funnel, running straight into the slough,” he says with a touch of pride. “Now thick vegetation holds everything in place. This is a good example of the trajectory we’re trying to achieve.”

The Conservancy is also working with farmers in the Salinas Valley to reduce nutrient runoff into the slough by re-creating wetland buffers that act as filters. “We’ve realized that protection alone won’t save the slough in the long run,” says Jennifer Biringer, director of the Conservancy’s working lands program in California. “We also need to address water quality, which drives broader environmental changes.”

For all their hard work, humans aren’t the only ones healing the estuary. They’ve had ample help—from an unlikely and adorable source.

young seal rests with eyes closed in the sun with water behind it
Sun Catcher A sleepy seal pup is one of several hundred Pacific harbor seals who “haul out” to sunbathe on the slough’s banks each day before nightly feeding forays into Monterey Bay. © Kiliii Fish

On a foggy morning at the estuary’s boat-strewn mouth, biologist Brent Hughes leans against a wooden railing, watching one of the slough’s architects at work. A halo of bubbles rises from the depths, soon followed by a sea otter clutching a softball-sized clam. The otter rolls onto its back, balancing the bivalve on its plush belly. As though solving a Rubik’s Cube, the mustelid twists and pries, finally popping open the shell and tearing into the pale flesh with gusto. “All his hard work paid off,” Hughes, a visiting biologist at University of California Santa Cruz, says admiringly.

Hughes didn’t set out to study marine mammals. When he began his doctoral research in 2010, he was actually trying to solve a vegetative mystery: How were the slough’s sea grass beds—underwater meadows that shelter young fish—flourishing despite the nutrient pollution streaming into the estuary?

By examining historical records, Hughes deduced the beds had begun recovering around 1984—the same year that sea otters, once hunted nearly to extinction for their pelts, began returning to Elkhorn. Through a series of field experiments, he discovered that otters had catalyzed the sea grass comeback via a trophic cascade, a chain reaction that rippled through the slough’s ecosystem. In the otters’ decades-long absence, crab populations had exploded. The booming crustaceans devoured sea slugs and shrimplike isopods, grazers that protect sea grass by munching algae off its blades. Without their cleaners, the sea grass had been smothered.

As the otters returned, however, they feasted on the crabs, allowing slugs and isopods to rebound and the algaefree sea grass to thrive. These days, says Hughes, more than 100 otters live in the slough, where females can raise pups safe from strong waves and great white sharks. Underwater meadows are healthier than they’ve been in nearly a century.

And sea grass beds aren’t the otters’ only beneficiaries. At the nearby Moss Landing Wildlife Area, Hughes points out the crustacean holes that riddle the muddy banks, “crab condos” that can destabilize the marsh. Just as hungry otters promote sea grass growth, they also protect pickleweed from root-munching crabs, slowing erosion and defending the marsh against rising seas. Think of it as a virtuous circle: Terrestrial conservation has improved slough water quality for marine creatures like otters, which in exchange help rebuild salt marshes.

“From the perspective of protecting the whole ecosystem, I can’t think of a better tool than a sea otter,” Hughes says.

Soon after Hughes departs, three cars roll into the Moss Landing parking lot, and three women wearing orange vests and bearing trash bags emerge. This is the self-named Pickleweed Posse, a squad of vigilante custodians who clean the slough of the litter—cans and cigarette butts discarded by visitors, even pallets lost by trucks on nearby Highway 1—that constantly washes ashore. “You’d be amazed by what shows up after high tide,” says Margie Kay, who has lived alongside Elkhorn Slough for four decades. Once she found an unopened home safe, perhaps discarded by frustrated burglars.

Elkhorn Slough is a hotbed of so-called ecosystem services, benefits that nature provides to humans: The estuary nourishes fish, traps carbon, and buffers farms and homes against climate change. But for Kay and many other people, there’s more to it—something that transcends utilitarian value. “This is about pride and ownership,” Kay says as she stoops to grab a plastic bottle. “It’s about feeling a deep connection to a special place.”

Five people pose with pitchfork on yellow grassland hills with blue sky
Ranch Hands Working with the Conservancy and Elkhorn Slough Foundation, Diane Porter Cooley (seated) and her family conserved more than 300 acres of their Porter Ranch, which drains into the slough—and ultimately, Monterey Bay. © Kiliii Fish