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An integrated framework that combines spatial and biophysical attributes of land with a hydrological model and an economic model is developed to identify cropland for enrollment in the Conservation Reserve Enhancement Program. Sediment deposition coefficients are determined endogenously depending on the land-use decisions on other land parcels. Application of this framework to a watershed in Illinois demonstrates that highly sloping land adjacent to water bodies should be selected for retirement. A marginal value rental payment scheme can achieve program goals of 20% sediment abatement at 39% lower cost than a productivity-based rental scheme. Copyright 2003, Oxford University Press.

Considering the spatial location of sites that are to be selected for inclusion in a protected reserve network may be necessary to facilitate dispersal and long-term persistence of species in the selected sites. This paper presents an integer programming (IP) approach to the reserve network selection problem where spatial considerations based on intersite distances are taken into account when selecting reserve sites. The objective is to reduce the fragmentation of preserved sites and design a compact reserve network. Two IP formulations are developed which minimize the sum of pairwise distances and the maximum intersite distance between all sites in the reserve network, respectively, while representing all species under consideration. This approach is applied to a pond invertebrate dataset consisting of 131 sites containing 256 species in Oxfordshire, UK. The results show that significant reductions in reserve fragmentation can be achieved, compared with spatially unrestricted optimum reserve selection, at the expense of a small loss in reserve efficiency.

Biofuel production is being promoted through various policies such as mandates and tax credits. This paper uses a dynamic, spatial, multi-market equilibrium model, Biofuel and Environmental Policy Analysis Model (BEPAM), to estimate the effects of these policies on cropland allocation, food and fuel prices, and the mix of biofuels from corn and cellulosic feedstocks over the 2007-2022 period. We find that the biofuel mandate will increase corn price by 24%, reduce the price of gasoline by 8% in 2022, and increase social welfare by $122 B (0.7%) relative to Business As Usual scenario. The provision of volumetric tax credits that accompany the mandate significantly changes the mix of biofuels produced in favor of cellulosic biofuels and reduces the share of corn ethanol in the cumulative volume of biofuels produced from 50% to 10%. The tax credits reduce the adverse impact of the mandate alone on crop prices and decrease the price of biofuels. However, they impose a welfare cost of $79 B compared to the mandate alone. These results are found to be sensitive to the rate of growth of crop productivity, the costs of production of bioenergy crops, and the availability of marginal land for producing bioenergy crops.