North America's seasonal wetlands—natural areas that are under water during all or part of the year—provide habitat for more than 600 species of birds, many mammals and countless thousands of invertebrates.

Less than ten percent of California's historic wetlands still exist today. Yet these dwindling resources are the breadbasket for millions of waterfowl and other birds. More than 60 percent of the birds migrating along the Pacific flyway spend the winter in the rich wetland habitats of California's great Central Valley.

Nature Reacts to Adverse Human Impact

Today most natural ecosystems must react to influences not present in earlier times. Pollution, changes in hydrology, increased urban runoff and other factors often decrease habitat productivity and biodiversity. Understanding these negative impacts is essential to preserving and restoring seasonal wetlands.

California's Unique Weather Patterns

Most of the Central Valley's annual rainfall occurs during the winter months from November through April. This is followed by a lengthy dry spell that can result in zero rainfall for six or more months at a stretch. Detailed knowledge of local weather patterns is also critical to wetlands management.

Wetlands Change With the Seasons

At key times during the year, our wetlands managers deploy an elaborate water control system to manage a series of carefully planned wetting and drying cycles. In late fall, wetlands are filled with water to provide a home for waterfowl and other animals. This water remains shallow most of the winter, allowing waterfowl to feed on wetland plants and invertebrates.

However, during peak winter water flows, much of the Upper Beach Lake basin becomes too deep to allow foraging by “dabbling” ducks, such as Mallards, Teal and Pintail. During these times, diving ducks, like Canvasbacks and Ring-Billed ducks, move into the area from places like Suisan Bay. In winter of 1998, over 15,000 Canvasbacks along with 5,000 Ring-Necked ducks filled the small Upper Beach Lake wetlands.

In the spring, most waterfowl migrate out of the Sacramento Valley to their northern nesting grounds. Seasonal wetlands are then drained, providing the ideal conditions for moist soil plant communities to begin springtime growth. These plants serve double duty, providing cover for non-migratory bird species to nest and raise their young, and producing the many tons of seeds that will sustain returning waterfowl the following winter.

Wetlands Benefit From Sound Management Practices

What would happen if SRCSD's wetlands were left to fend for themselves?

• Without management, seasonal wetlands typically produce about 200 pounds of wetland plant seed per acre.

• With sound management, wetlands can produce more than 1,000 pounds of seed per acre--more than a five-fold increase.

Given the huge amount of wetlands that have already been destroyed in California, it's essential that wildlife managers work to maximize the productivity of our remaining wetlands. Bufferlands staff monitor the vegetation composition of over 300 acres of seasonal wetlands each year and compare the results to prescribed performance goals. These surveys ensure that the wetlands are dominated by highly productive species, such as watergrass, swamp timothy, Mexican sprangletop, and annual smartweeds. If wetland productivity falls below the goals set for the wetland, our wetland managers develop corrective measures to encourage desirable species and eliminate weeds.

Click here (70K pdf*) to read a summary of the 2006 wetland surveys.

*Requires Adobe Acrobat's free reader, available here: If you have problems with PDF files on this site, please read this.

For more information about wetlands and waterfowl management on SRCSD's Bufferlands, please contact: