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The Conservation Reserve Program (CRP), initiated by the Conservation Title of the Food Security Act of 1985, is the primary federal program to control nonpointsource pollution in agricultural watersheds of the United States. However, the program is designed primarily to reduce soil erosion rather than to retire croplands in a manner optimal for controlling runoff of sediment and associated pollutants. This study estimates potential enrollment of streamside and floodplain croplands in this ten-year retirement program in order to gauge the potential of the CRP as a water-quality improvement policy. A contingent choice survey design was employed in Fayette County, Illinois, to demonstrate that there is substantial potential for retirement of streamside and floodplain croplands in the CRP. Enrollments in each program climb from less than 6% to over 83% of eligible croplands as the annual rental rate is increased from $20 to $200/acre. Potential retirement of streamside and floodplain croplands declines, however, if tree planting, drainage removal, or a 20-year contract are required. The potential of a CRP-based water-quality program to improve water quality and aquatic ecosystems in agricultural watersheds is thus substantial but constrained by the economic trade-offs that farmers make between crop production and conservation incentives in determining the use of their riparian lands.  相似文献   
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This paper engages the existing literature on Urban Political Ecology (UPE) from the perspective of regulating urban expansion through greenbelts. The paper makes a contribution to a better understanding of suburbanisation and postsuburbanisation which have so far not been at the centre of the concerns of UPE. In an era of global suburbanisation greenbelts differ from similar boundary setting exercises in the past and are as varied as the suburbanisation processes and their governance themselves. While conscious of those varieties, we focus here on the Greater Golden Horseshoe (GGH) greenbelt in Ontario that was created by provincial legislation in 2005. With the 2005 legislation, the Ontario government declared 720,000 hectares off limits for conventional urban development. The Greenbelt Act created an expansive area under protection from the Niagara Peninsula in the south to the Bruce Peninsula in the north, the Niagara Escarpment in the west to a series of moraines in the east. We will argue that the GGH greenbelt has become a prime negotiation space for the overall re-regulation of urban political ecologies in Southern Ontario. Largely surrounding the booming Toronto region, the GGH greenbelt is expansion space and projection screen of a suburbanizing region in search of redefinition.  相似文献   
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