Department of Agribusiness Economics, Southern Illinois University, Carbondale, Illinois 62901, USA.
Ecol Appl. 2011 Jun;21(4):1068-84. doi: 10.1890/09-0619.1.
While biofuels may yield renewable fuel benefits, there could be downsides in terms of water quality and other environmental stressors, particularly if corn is relied upon exclusively as the feedstock. The consequences of increased corn production will depend importantly on where (and how) the additional corn is grown, which, in turn, depends on the characteristics of land and its associated profitability. Previous work has relied on rules of thumb for allocating land to increased acreage based on historical land use or other heuristics. Here, we advance our understanding of these phenomena by describing a modeling system that links an economics-driven land use model with a watershed-based water quality model for the Upper Mississippi River Basin (UMRB). This modeling system is used to assess the water quality changes due to increased corn acreage, which is associated with higher relative corn prices. We focus on six scenarios based on six realistic pairs of corn and soybean prices which correspond to a scale of decreasing soybean to corn price ratio. These price-driven land use changes provide estimates of the water quality effects that current biofuel policies may have in the UMRB. Our analysis can help evaluate the costs and environmental consequences associated with implementation strategies for the biofuel mandates of the new energy bill. The amounts of total N and P delivered to the outlet of the UMRB (located at Grafton, Illinois, USA) rise as corn production becomes more intensive in the region. Our results indicate that a 14.4% in corn acreage in the watershed due to corn intensification in the most economically profitable locations would result in a 5.4% increase in total nitrogen loads and in a 4.1% increase in total phosphorus loads at Grafton. Our most aggressive scenario, driven by high but not out of reach crop prices, results in about a 57% increase in corn acreage with a corresponding 18.5% increase in N and 12% increase in P. These are somewhat conservative increases in nutrients, compared to those of previous studies, likely due to our focus on cultivated cropland which is already heavily fertilized.
虽然生物燃料可能具有可再生燃料的优势，但从水质和其他环境压力因素方面来看，也可能存在一些弊端，尤其是如果完全依赖玉米作为原料。增加玉米产量的后果在很大程度上取决于额外玉米种植的地点（以及如何种植），而这又取决于土地的特性及其相关的盈利能力。之前的工作依赖于基于历史土地利用或其他启发式方法将土地分配给新增面积的经验法则。在这里，我们通过描述一个将经济驱动的土地利用模型与密西西比河流域上游（UMRB）基于流域的水质模型联系起来的建模系统，来深入了解这些现象。该建模系统用于评估因玉米种植面积增加而导致的水质变化，这与相对较高的玉米价格有关。我们专注于六个基于六个现实的玉米和大豆价格对的情景，这些价格对对应于大豆与玉米价格比率递减的规模。这些由价格驱动的土地利用变化提供了当前生物燃料政策可能对 UMRB 产生的水质影响的估计。我们的分析可以帮助评估新能源法案中的生物燃料授权的实施策略所带来的成本和环境后果。随着该地区玉米种植的集约化，进入 UMRB 出水口（位于美国伊利诺伊州的格夫顿）的总氮和总磷量增加。我们的研究结果表明，在经济效益最高的地区，由于玉米集约化导致流域内玉米种植面积增加 14.4％，将导致格夫顿的总氮负荷增加 5.4％，总磷负荷增加 4.1％。我们最激进的情景是由高但并非遥不可及的作物价格驱动的，结果是玉米种植面积增加了约 57％，相应的氮增加了 18.5％，磷增加了 12％。与之前的研究相比，这些营养物的增加幅度有些保守，这可能是由于我们专注于已经大量施肥的耕地。
