Delta

Delta marsh © Harold E. Malde

Not far southwest of the state capitol, California's two largest rivers, the Sacramento and the San Joaquin, meet to form the Delta, the largest estuary on the west coast of North and South America. Although it has been heavily impacted by levee construction and water diversions, the 940-square-mile Delta region remains an important area for wildlife, supporting more than 750 species of plants and animals. The Nature Conservancy has identified the Delta as a biologically rich and viable area crucial to sustaining unique and precious natural diversity.

Size
The Delta is over 600,000 acres (940 square miles) in extent. The Nature Conservancy has purchased easements or fee interests in approximately 11,000 acres of land within the Delta. These properties are managed as a part of the Cosumnes River Preserve.

Location
The Delta lies south and southwest of Sacramento, approximately 50 miles east of San Francisco. The Nature Conservancy's Delta activities are focused in the corridor of the Mokelumme River, east and south of the town of Walnut Grove. Map

Plants and Wildlife
The historic Delta was home to more than 500,000 acres of tidal marsh and wetland, and hundreds of linear miles of riparian habitat. These habitats provided critical staging areas for some of the most threatened native resident and anadromous (migratory) fishes in California, as well as migratory fowl. Today, Delta tidal wetland has been reduced to a few thousand acres, generally in small isolated patches. Delta waterways, constricted by levees, provide only limited habitat value, and most of the Delta's aquatic systems are dominated by invasive exotic species. Many species of birds, including waterfowl and sandhill cranes, rely on the Delta's rich farmland, much of which is shallowly flooded after crops are harvested, for winter habitat.

Native fishes include Delta smelt, Sacramento splittail, longfin smelt, Chinook salmon, Central Valley steelhead, and green sturgeon. Marshes, sloughs, and floodplains also provide habitat for other declining species, including zooplankton and aquatic invertebrates.

Why the Conservancy Selected This Site
Before the Gold Rush, the Delta was an extensive, intertidal wetland, a complex and variable mosaic of marshes, ponds, mudflats and seasonally inundated islands of dense forest. Historical land use changes and water demands of over 15 million people have drastically altered the natural Delta ecosystem, destroying nearly all of its tidal wetlands. While the Delta cannot be restored to its historical ecological state, we can accomplish large-scale restoration in some areas, and in others we can manage waterways and farmland to meet the needs of target native species.

What the Conservancy Has Done/Is Doing
The Nature Conservancy is pursuing large-scale restoration of native Delta habitats: wildlife-friendly seasonal wetlands, riparian forests, native grasslands, and tidal marshlands. Since the Conservancy began its work in the Delta:

• The Nature Conservancy has won local support and begun detailed planning for the restoration of a 1,600-acre freshwater tidal marsh.
   
• In the Delta, The Nature Conservancy has protected 11,000 acres of farmland, enabling year-round practices that provide habitat for sandhill cranes, waterfowl, and raptors. This enables conservation and agriculture to enhance each other's efforts while maintaining the long-term contribution of agriculture to the local economy.