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The Sacramento National Wildlife Refuge Complex is part of the United States system of National Wildlife Refuges (NWR).〔U.S. Fish and Wildlife Service. 2009〕 It is located in northern California, in the valley of the Sacramento River. The Sacramento NWR Complex was created in an attempt to resolve the conflict between the needs of migrating birds using the Pacific Flyway, and those of agriculture. ==History and components== Before the arrival of European settlers in the 19th century, much of the Sacramento valley was taken up by seasonal wetlands and grasslands. By the beginning of the 20th century, much of this had been replaced by farmland, particularly for the growing of rice, and the rivers no longer create new wetlands because their flow is controlled by levees and irrigation schemes. Less than 10% of the original wetland area remains. Migrating birds have continued to use the area, and resting in the rice fields, consumed considerable quantities of the crop. In 1937, the United States Fish and Wildlife Service, with the aid of the Civilian Conservation Corps, began the process of creating a refuge within dry, alkaline lands between the towns of Willows and Maxwell. This was the original Sacramento NWR. From the 1940s onward, additional refuges were created, so that the Sacramento NWR Complex now includes the following refuges, located between north of the city of Sacramento: * Sacramento National Wildlife Refuge (southeastern Glenn and northeastern Colusa counties, south of Willows) * Delevan National Wildlife Refuge (east of Maxwell) * Butte Sink National Wildlife Refuge (northeast of the town of Colusa) * Colusa National Wildlife Refuge (between the towns of Colusa and Williams) * Sutter National Wildlife Refuge (southwest of Yuba City) * Sacramento River National Wildlife Refuge (several non-contiguous sites along the Sacramento River between Red Bluff and Princeton) The total area of the refuges is about s). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sacramento National Wildlife Refuge Complex」の詳細全文を読む スポンサード リンク
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