摘要：Changes in the use of land in the United States produce significant economic and environmental effects with important implications for a wide variety of policy issues, including protection of wildlife habitat, management of urban growth, and mitigation of global climate change. In contrast to previous descriptive and qualitative analyses of the trends in national land use, this paper uses an econometric approach to isolate the importance of historical changes in land-use profits and key government policies in determining national land-use changes from 1982 to 1997. The policies we examine are the Conservation Reserve Program (CRP) and total government payments to crop producers. We estimate a national-level discrete choice model of changes among the major land-use categories (crops, pasture, forest, urban, range, and CRP) with parcel-level observations of land use and land quality from the U.S.D.A. National Resources Inventory (NRI) and measures of county-level land-use net returns from a variety of sources. We then use fitted values from the econometric model to simulate land-use change from 1982 to 1997 under a series of factual and counterfactual scenarios that isolate the effects of different economic and policy factors. The simulations suggest how changes in economic returns and government policies have driven land-use changes in the past and will continue to affect nationwide land-use changes in the future. For example, we find that the introduction of the CRP and the decline in crop profits were the most significant explanatory factors driving the decline in cropland. Our results highlight some "unintended consequences" of government policies and the importance of net returns to a range of alternative land uses as determinants of land area change for each particular use.
关键词：land use;econometric model;counterfactual simulation;Conservation Reserve Program (CRP)
