At midday, the surface of the Cosumnes River mirrors a bluebird sky. The oak forest hoods the water on either side. Though it’s quiet, life is in motion: a belted kingfisher flashes past in search of fish. A white-tailed kite surveys for prey from a lofty perch. On the river, the current is so gentle you can forget how far this water has come: all the way from the western Sierra foothills to here, the Cosumnes River Preserve, a hour and a half’s drive from Berkeley. From here, it meets the Mokelumne River, which flows into the Bay and then the Pacific Ocean.
This current is like no other feeding the Bay, and unlike every other river in the Central Valley—not a single dam hems the Cosumnes’s passage. And because it straddles the border between estuary and upstream river systems, it becomes home to the diversity and abundance of both worlds. So the Cosumnes River Preserve holds an unusual position within the larger Bay-Delta, as an oasis for critically endangered and endemic animals, a stronghold of healthy riparian forest, and a critical example of natural floodplain processes at work.
But dams aren’t the only thing that can damn a river. The water table has been sinking for decades, as farmers have pumped more groundwater toward thirsty crops faster than it is replenished—a situation that worsened through recent droughts. Invasive plants and degraded habitat threaten the river’s native species communities, and restoration must become increasingly ambitious to protect them. Thus in 2023, the U.S. Bureau of Land Management allocated $7.6 million of Inflation Reduction Act money for a variety of projects aimed at helping tackle these landscape-level challenges and building new communities of stewardship across the watershed.
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“These 53,000 acres are vital,” Amy Fesnock, the preserve manager for the Cosumnes River Preserve, says. “The work [we’re] doing here has an immediate effect.”
Ann Willis, California regional director for the nonprofit environmental advocacy group American Rivers, cautions that money like this doesn’t address the biggest threat to the Cosumnes—groundwater overdraft. “The money is really kind of picking off some of the pieces on the edge of a big problem,” says Willis, who has worked in the region for decades and was not involved in the project. But she says this work is nonetheless “really important”—and will lay the foundation for bigger thinking to come.
‘Legendary’ restoration work
For several thousand years, Plains Miwok and Nisenan people stewarded this river and its forests—conducting annual burns, sowing seeds, harvesting native plants—until Europeans arrived, carved the Valley up into farmland, and decimated Indigenous tribes across the region. The most recent chapter in the restoration of the Cosumnes began a few decades ago, as government and nonprofits including The Nature Conservancy (TNC) and Ducks Unlimited began to tackle that colonial legacy.
Ecologist Derek Hitchcock first visited the preserve in the 1990s, and says these nonprofits’ work in that era transformed the area. “As a career large-scale restoration practitioner, I consider it kind of legendary,” says Hitchcock, who joined the Cosumnes restoration as a TNC staffer less than two years ago.
The two nonprofits and their partners used cutting-edge approaches for the time—collaborating with farmers, encouraging grazing, intentionally breaching levees, using chainsaws to thin unwanted trees—to protect what makes the Cosumnes special. Today, the dense oak forest that lines the Cosumnes, where tree swallows and wood ducks nest, is the largest surviving valley oak riparian forest in California as a result of these decades of work.
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Farmers working with TNC have also planted rice in flooded fields that help thousands of sandhill cranes, which now flock here on their long migrations, staying from October to March. As part of the IRA grant, TNC is restoring seasonal wetlands for giant garter snakes, an endangered species that depends on areas flooded year-round to survive. The idea driving their work, Rodd Kelsey, another scientist with TNC, says, is to “[let] nature restore itself.”
Many projects afoot
The Cosumnes’s quiet waters don’t hint at how much work it takes to protect these ecosystems while keeping the humans that also live here happy. Biologists might like to let levees break and areas flood according to the river’s meandering whims. But the river winds through agricultural areas and towns, where people have gotten used to the river staying put. Protecting the Cosumnes’s health and biodiversity in these narrow bounds, therefore, requires both land managers and conservationists to make compromises and organize a lot of heavy lifting.
Wetlands are manually filled and drained seasonally to create waterfowl habitat. Machines shift tons of dirt to improve other wetland areas. Meanwhile, with the IRA funds, Fesnock and her team have been beating back invasive plants through judicious herbicide applications and massive mechanical scoopers. Their main target is the yellow water primrose, which forms dense mats by the river’s edge that choke out natives around it. “It’s definitely my nemesis,” Fesnock says.
They are prepared to adapt their plans as needed: for example, the Wilton Rancheria has urged BLM to change its more herbicide-forward approach to invasives, and instead use techniques grounded in traditional ecological knowledge on this critical landscape. (BLM hopes to do this by deploying wading hungry goats, though the ungulates’ effectiveness has yet to be tested at scale.)
The IRA restoration funds were competitive within BLM, and Fesnock says that part of what made the Cosumnes stand out were the preserve’s existing partnerships across the watershed, making federal dollars go further. Restoration money like this typically all goes towards construction-heavy projects, says Willis. And it is indeed supporting such work: for example, the removal of a fish passage barrier and the creation of floodplains, thinning forests to reduce wildfire risk, supporting bees and butterflies with native plantings, as well as the endless fight against invasives.
But alongside the excavators scooping tons of weeds out of the water, money is also boosting partnerships with the Galt Elementary School District, Latino Outdoors, and other groups. Some 2,500 students, from kindergarteners to high schoolers, have visited the preserve over the past year alone. In this predominantly low-income area with underfunded teachers, it has been most students’ first chance to visit the water. Out on the water and in the woods, they’ve gathered acorns, identified birds, and gone paddling.
The outreach program has been going for so many years now that parents accompanying their children on trips often point out seeds they planted as a student. This funding aims to bring the numbers visiting the preserve into the tens of thousands—in the process seeding tens of thousands of memories of the watersheds, and trees, to sprout for years to come.
Dreaming for 100 years
The Cosumnes team has spent the money as fast as they can: by now, all of the money has been allocated to projects. Fesnock is mindful that congresspeople like to see results on the order of an election cycle—even though ecological restorations may take decades to bring to fruition. As an ecologist, she keeps a 100-year vision of the arc of the landscape in her mind, and tries to head in that direction using funding that trickles out a few years at a time.
Some of the results are easy to see. Many an oak tree along the Cosumnes has a wooden box attached to it: a newly installed, IRA-supported nesting box for native tree swallows and wood ducks. The preserve staff’s efforts to beat back the primrose have already begun to yield results after a year of work.
Other outcomes will take much longer to manifest. Native seeds need to be gathered; plants take time to grow. “A lot of the native plants we want to do here have never been propagated before,” Fesnock says.
Ultimately, the hope is that protecting the river and its ecosystems will help people across the region. The river’s health, says Kelsey of TNC, is “fundamental to people having clean water in the Bay Area.”
Willis, of American Rivers, remembers coming to the Cosumnes in 2016 at the end of the drought, after the first rain in half a decade. The flooded fields were jeweled with bubbles. “It was like wading through a lake of soda pop,” she says. The bubbles were air that had been displaced from the ground, as rainwater sank into aquifers bled dry by the long drought and years of groundwater pumping. “It was like watching a thirsty giant get its first drink of water in years,” she recalls. The memory reminds her, as both an ecologist and just a human in the world: a river is a living being. “It needs the same things we need.”
If you go
Cosumnes River Preserve
The draw: Explore wetlands, oak forest, and river on four and a half miles of easy trails. Paddle through lush riparian forest, alive with the sounds of birds like xyz. In the winter, see sandhill cranes and their young by driving along Staten Island (not the New York borough) between November and March.
Boating: A small boat launch is 200 yards from the parking lot, so a canoe or kayak cart is recommended. Boats are not available for rental. Check tide and flow charts before entering the water.
Hours and entrance: 9am to 5pm daily. Hours may vary with staff and volunteer capacity; check updated hours at cosumnes.org.
Address: 13501 Franklin Blvd, Walnut Grove, CA 95690 (20 miles south of Sacramento)
Facilities: Bathrooms are available. Bring your own water. The visitor’s center, with both indoor and outdoor exhibits, provides information on the wildlife and history of the Cosumnes area. The Wetlands Walk Trail and Boardwalk Loop are ADA-compliant. Pets, camping, hunting, or fishing are not allowed anywhere from land on the Cosumnes River Preserve property; permitted hunting and fishing is possible during the appropriate season from a non-motorized boat in the river.
