The ICP has also called for enhancement of 444,000 acres of agricultural habitat that was divided as follows; 1) enhancement of 332,000 acres of grain fields to help meet the food energy needs of migrating and wintering waterfowl, and 2) enhancement of 112,000 acres of upland habitat to ensure adequate nest success for breeding waterfowl. Although habitat programs for breeding waterfowl are just now gaining momentum in the Valley, over 353,000 acres of rice habitat is now flooded annually to provide food resources for wintering and migrating waterfowl. Finally, the ICP recommended securing reliable water supplies for all National Wildlife Refuges and State Wildlife Areas in the Central Valley, as well as for private wetlands in the Grasslands Resource Conservation District. This equals 506,000 acre-feet of annual water supplies. To date, over 70% of this objective has been achieved (363,000 acre-feet) as a result of passage of the Central Valley Project Improvement Act.
Ducks Unlimited has recently updated habitat objectives for the Central Valley in cooperation with its Central Valley Joint Venture partners. The purpose of this update was to clearly link waterfowl objectives for the Valley to the NAWMP, and to identify the landscape conditions needed to sustain waterfowl populations at NAWMP goals. A critical assumption of this update is that wetlands must provide a minimum of 50% of waterfowl food energy needs in each of the Valley's nine drainage basins, which serve as planning units. In some basins, agriculture accounts for over 70% of available waterfowl foods. Agricultural habitats will continue to be important in meeting the needs of waterfowl in the Central Valley. However, changing agricultural markets and increases in harvest efficiency are largely beyond the control of DU and its partners. Increasing the amount of wetland habitat for waterfowl can offset some of these unforeseen changes. Finally, the approach to establishing wetland enhancement objectives has been changed for this version of the ICP. Wetland enhancement typically involves periodic maintenance or improvement of water control structure, levees, and ditch networks used to manage wetlands. Interviews with resource professionals suggest that wetlands in the Valley should undergo some level of enhancement every ten to fifteen years. The ICP assumes that managed wetlands in the Central Valley need some form of enhancement an average of every twelve years. As a result, enhancement objectives are expressed on an annual basis and are perpetual. The annual enhancement objective in this version of the ICP assumes that wetland restoration objectives for the Valley are met.
Although most of DU's work in the Central Valley has focused on migrating and wintering waterfowl, there is a growing emphasis on meeting the needs of breeding waterfowl as well. For example mallard harvest in the Central Valley now exceeds that of pintails, and up to 75% of mallards shot in the Valley are produced there. As a result, DU and its partners have developed a plan to guide habitat efforts for breeding mallards. This includes identifying the types of habitat programs to be delivered, where these programs should be focused, and ongoing research to better understand what limits the size and success of breeding mallard populations in the Central Valley.
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