Greenhalgh S, Faeth P
World Resources Institute, Washington, DC, USA.
ScientificWorldJournal. 2001 Nov 22;1 Suppl 2:976-83. doi: 10.1100/tsw.2001.354.
Nutrient pollution, now the leading cause of water quality impairment in the U.S., has had significant impact on the nation"s waterways. Excessive nutrient pollution has been linked to habitat loss, fish kills, blooms of toxic algae, and hypoxia (oxygen-depleted water). The hypoxic "dead zone" in the Gulf of Mexico is one of the most striking illustrations of what can happen when too many nutrients from inland watersheds reach coastal areas. Despite programs to improve municipal wastewater treatment facilities, more stringent industrial wastewater requirements, and agricultural programs designed to reduce sediment loads in waterways, water quality and nutrient pollution continues to be a problem, and in many cases has worsened. We undertook a policy analysis to assess how the agricultural community could better reduce its contribution to the dead zone and also to evaluate the synergistic impacts of these policies on other environmental concerns such as climate change. Using a sectorial model of U.S. agriculture, we compared policies including untargeted conservation subsidies, nutrient trading, Conservation Reserve Program extension, agricultural sales of carbon and greenhouse gas credits, and fertilizer reduction. This economic and environmental analysis is watershed-based, primarily focusing on nitrogen in the Mississippi River basin, which allowed us to assess the distribution of nitrogen reduction in streams, environmental co-benefits, and impact on agricultural cash flows within the Mississippi River basin from various options. The model incorporates a number of environmental factors, making it possible to get a more a complete picture of the costs and co-benefits of nutrient reduction. These elements also help to identify the policy options that minimize the costs to farmers and maximize benefits to society.
营养物污染如今是美国水质受损的首要原因，已对美国的水道造成了重大影响。过量的营养物污染与栖息地丧失、鱼类死亡、有毒藻类大量繁殖以及缺氧（水体缺氧）有关。墨西哥湾的缺氧“死亡区”是内陆流域过多营养物抵达沿海地区时可能发生情况的最显著例证之一。尽管实施了改善城市污水处理设施的项目、更严格的工业废水要求以及旨在减少水道泥沙负荷的农业项目，但水质和营养物污染仍然是个问题，而且在许多情况下还恶化了。我们进行了一项政策分析，以评估农业界如何能够更好地减少其对“死亡区”的影响，同时也评估这些政策对气候变化等其他环境问题的协同影响。我们使用美国农业的部门模型，比较了包括无针对性的保护补贴、营养物交易、扩大保护储备计划、农业碳和温室气体信用额度销售以及减少化肥使用等政策。这项经济和环境分析以流域为基础，主要关注密西西比河流域的氮，这使我们能够评估各种方案在密西西比河流域内溪流中氮减少的分布情况、环境协同效益以及对农业现金流的影响。该模型纳入了许多环境因素，从而有可能更全面地了解营养物减少的成本和协同效益。这些因素还有助于确定将农民成本降至最低并使社会利益最大化的政策选择。
