Places We Protect

Cosumnes River


Howard Ranch at the Cosumnes River Preserve.
Cosumnes River Preserve Howard Ranch at the Cosumnes River Preserve. © Mike Eaton/The Nature Conservancy

The last remaining undammed river on the western slope of the Sierra Nevada.



On a single winter day, observers tracked 58,000 birds at the Cosumnes River Preserve. Among those in flight and on the ground were many threatened greater sandhill cranes, which unfurled their enormous gray wings and added to the chorus of native and migratory birds with their ancient and distinctive bassoon-like cry.

Listen to the trumpeting call of sandhill cranes. (Audio credit: Conservation Metrics, Inc.)

Meanwhile, several species of bats have begun a resurgence in both the riparian or riverside forest and in a bat-friendly bridge built over the Cosumnes River. Elusive reptiles and mammals, such as the endangered giant garter snake and the playful river otter, have also found safe haven in the preserve.

This flourishing of wildlife has been made possible through a number of land purchases and a suite of pioneering conservation efforts that have increased the area for and improved the quality of wildlife habitat. As part of this effort, the Cosumnes River project helps local farmers and ranchers continue to pursue their livelihood in ecologically responsible ways.

The preserve has partnered with local ranchers to protect more than 20,000 acres of vernal pool and blue oak habitats that also serve as important rangelands. TNC’s partnerships not only preserve its biological targets but also help maintain the area’s unique ranching culture.

Finally, the preserve invites visitors to enjoy an array of recreation activities, including photography; paddling; birding; and hiking, whether through its lush forests along the scenic Cosumnes River, on a boardwalk in its seasonal marshes or amongst vernal pools in a blue oak savanna.

A Preserve Is Born

In 1984, The Nature Conservancy purchased 85 acres of old-growth riparian forest approximately 20 miles south of Sacramento, establishing the Cosumnes River Preserve. While building a partnership of what is now a consortium of nine private and public entities, TNC acquired lands and conservation easements that now protect 50,000 acres, encompassing blue and valley oak woodlands, freshwater wetlands, vernal pool grasslands and important farmlands.

Going with the Flow

Early on, The Nature Conservancy recognized the importance of the Cosumnes as one of the last free-flowing rivers west of the Sierra Nevada. Without extensive dam control, the river overtops its banks annually, nourishing the riparian habitat.

Fish, such as the threatened Chinook salmon, forage for food in this floodplain and seek cover from predators. These floodplain areas are critical in the life cycle of native fish, as fingerlings grow quickly in these protected backwater areas and therefore have an increased chance of survival when they return to the river channel.

Natural flooding also recharges the aquifer that supplies water to farmers and nearby municipalities.

The “Accidental Forest”

The Cosumnes River has been the inspiration for and epicenter of many innovative conservation discoveries. For example, Conservancy scientists observed that a natural levee breach caused trees to spring up beside the river. Witnessing the natural restoration process prompted us to add this effective tool—purposeful levee-breaching—to the strategies we use to restore the forest.

Natural and Human Communities in Harmony

Another key finding proved mutually beneficial to wildlife and local ranchers. Despite prevailing wisdom, we determined that cattle grazing can actually benefit habitat-rich vernal pools—a rare and somewhat fragile feature of the Cosumnes landscape. Like the deer and tule elk that once grazed this area, cows curb the growth of invasive, non-native weeds.

The Nature Conservancy’s ongoing research, combined with our support for wildlife-friendly agricultural practices, assists farmers and ranchers in their stewardship of the land, helping them to remain economically viable while protecting the natural community.

In short, the Cosumnes River project demonstrates that conservation, agriculture and recreation can harmoniously coexist.



Explore our work in this region

View of riparian habitat along the Cosumnes River north of Rancho Murrietta, CA.
Cosumnes River View of riparian habitat along the Cosumnes River north of Rancho Murrietta, CA. © Jeff Hart

Hike, paddle, bird-watch, picnic, enjoy the Visitor’s Center

What to see

Valley and blue oak forests, river otters, bats, endangered greater sandhill cranes, lesser sandhill cranes, endangered Swainson’s hawks, tundra swans, great blue herons, egrets, pintails, white-tailed kites, and red-shouldered hawks

Visit the Cosumnes River Preserve.

You Can Help

Ensure that the cranes continue to return to the preserve, supporting responsible agriculture and ranching, and keeping the wilderness open for thousands to enjoy.