The Sacramento, California’s largest river, supports a rich and ancient mosaic of aquatic habitats. Its oxbow lakes, sloughs, seasonal wetlands, riparian forests, valley oak woodlands and grasslands harbor important habitat for birds, fish and other species. The river also supplies 35 percent of the state’s total water supply. However, 150 years of human activity have taken their toll on this diverse ecosystem.

The Nature Conservancy’s goal is to reconnect the river to its historical floodplain and restore the abundant forests that once lined the stretch of more than 100 river miles between Red Bluff and Colusa, establishing 33,000 acres of healthy streamside habitat. This ambitious undertaking constitutes the largest riparian planting project in the West. “Our challenge is to protect and restore an incredible natural environment while reducing floods and ensuring that the river’s resources remain available to local people who depend on them,” says Sacramento River project director Dawit Zeleke.

To achieve the Conservancy’s goals, Zeleke and his team follow three strategies: acquiring flood-prone lands, replanting them with native trees and shrubs and restoring natural river processes. For nearly two decades they’ve collaborated with local organizations and hundreds of local residents, including farmers, and have helped raise the millions of dollars required to finance the project. To date, the Conservancy and its partners have protected 13,400 acres along the river—more than 40 percent of the goal. Over 3,600 acres have already been replanted, with an additional 3,000 acres to be restored in the coming years.

During nearly two decades of work on the Sacramento, the Conservancy has had the unparalleled opportunity to apply a concept much discussed among resource managers, conservationists and scientists: adaptive management. Adaptive management is a method of managing natural resources that constantly tests assumptions over time and enables conservationists to learn from experience. “It ensures that our strategies evolve to bring us ever closer to our goals—even as our work restores a project area,” Zeleke says.

The approach consists of several steps, executed in partnership by scientists and conservation managers. First, partners assess assumptions and set management goals for the conservation area. Based on this assessment, the team takes action, then monitors the environment to see how it responds. After measuring results, partners refine their assumptions, goals and monitoring regimen to reflect what they’ve learned from past experiences. Then, with refinements in place, the entire process begins again.

“Adaptive management enables us to navigate the inherent uncertainty in ecological systems by constantly monitoring, measuring and adapting to change,” says Zeleke. “It helps us answer the question the Conservancy must pose about each of its conservation efforts: ‘Is it working?’”

One example of successful adaptive management is a project to monitor songbird populations along the Sacramento River in partnership with PRBO Conservation Science (formerly the Point Reyes Bird Observatory), the U.S. Fish and Wildlife Service and others. Scientists count birds and their offspring to assess habitat needs and reproductive success, then capture, mark and release representatives of important populations to determine their survival rates.

“Birds are extremely valuable indicators of an ecosystem’s health,” says Zeleke. “They are sensitive to environmental change and may respond quickly and consistently to environmental degradation or improvements.”

Over time, PRBO’s studies have shown that birds are responding favorably to the Conservancy’s restoration of vegetation along the river. Within the first few years after native vegetation was planted, critical bird populations recolonized the river’s banks, and as restored sites have matured, the diversity of native birds has increased. However, although birds that nest in tree cavities showed healthy populations, birds that build open cup nests were not producing enough offspring to maintain their populations. In fact, less than 20 percent of their offspring were surviving to fledge.

Why? Without the protection of underbrush, open-cup nesters such as the lazuli bunting are more susceptible to predators and parasitic birds, including brown-headed cowbirds, which prey on nestlings and take over other birds’ nests. Although Conservancy plantings were improving the habitat for birds in general, they lacked a critical layer of protection for more vulnerable cup-nesting species, whose populations are important indicators of the habitat’s overall health.

With support from PRBO scientists, Conservancy managers adapted their revegetation program to include more lower-level plantings of “understory” shrubs and other plants. The Conservancy now routinely incorporates native grasses and mugwort, a native sage species typical of a riparian understory, into its restoration plantings.

Improving planting designs is just one way adaptive management helps the Conservancy increase its impact on the Sacramento River. “Working with many other scientists, we’re looking at several ecological indicators of restoration success, such as how the river meanders, river flow patterns and the reconnection of historical floodplain to important river processes,” says Mike Roberts, director of hydrology for the Conservancy’s Sacramento River Project.

Scientists are using computer models to evaluate and test various conservation scenarios—for example, setting levees back from the river channel at Hamilton City (see California Update, Spring/Summer 2004), where residents live in the shadow of an ancient, deteriorating levee. This scenario reconnects the river to the floodplain while improving flood protection for Hamilton City residents. The Conservancy is also exploring various flow strategies that would enhance the overall health of the river.

The long-term partnerships that support these science-based conservation efforts enhance the Conservancy’s ability to apply adaptive management. “Our science colleagues help us manage these studies from a variety of angles and adapt results for lasting success,” says Roberts. These relationships, combined with years of work in places like the Sacramento River, set the Conservancy apart as an organization whose impact grows from both science and experience.

Says Zeleke, “With adaptive management, we can address human and environmental needs, bringing both into balance on a healthy river that remains a vital resource and a source of inspiration to future generations.”