Centre for Tropical Water and Aquatic Ecosystem Research, College of Science and Engineering, James Cook University, Queensland 4811, Australia.
Centre for Tropical Water and Aquatic Ecosystem Research, College of Science and Engineering, James Cook University, Queensland 4811, Australia; Department of Agriculture and Fisheries, PO Box 1085, Townsville, Queensland 4810, Australia.
Mar Pollut Bull. 2021 Jun;167:112373. doi: 10.1016/j.marpolbul.2021.112373. Epub 2021 Apr 22.
Eutrophication of coastal and nearshore receiving environments downstream of intensive agricultural production areas is a global issue. The Reef 2050 Water Quality Improvement Plan (2017-2022) sets ambitious targets for reducing pollutant loads entering the Great Barrier Reef from contributing agricultural catchments. At a regional scale, the Wet Tropics end-of-catchment target load reduction for dissolved inorganic nitrogen (DIN) is 60% from the 2012-2013 anthropogenic load level. However, not even with the combined efforts of the Reef Regulations (December 2019) mandate and adoption of best practice nutrient management on farm, is it likely that these DIN targets will be reached. Thus, there is a need for innovative and cost-effective approaches to deliver further water quality improvement. Transitioning low-lying, marginal sugarcane land to alternative land uses that require lower or no nitrogen inputs, but still provide farmers with income streams, is a potentially attractive solution. In this study, a multi-criteria analysis was conducted to identify sites suitable for such alternative land uses. The cost-effectiveness of DIN reductions from these land use changes were calculated, accounting for reductions in annuity gross margins and land conversion cost. In certain locations (where conversion costs are low and DIN reductions are high) treatment wetlands and no-input cattle grazing offer cost-effective DIN reduction in the range of 20-26$/kg DIN. This compares favourably with existing agricultural extension-based approaches (c. $50/kg DIN reduction). Ecosystem service wetlands (i.e., wetland restoration for fish production) - again when appropriately situated - offer the prospect of even more cost-effective performance (11-14 $/kg DIN reduction). These results, in conjunction with best management practices, support the premise that alternative land uses are cost-effective options for improving water quality in certain areas of low-lying, low productivity sugarcane land. On-going investments by government in addition to private market funding mechanisms could be appropriate for supporting such land use transitions. These approaches need to be tested and refined via targeted pilot projects, as part of a whole-of-landscape approach to achieve broader reef water quality targets.
沿海和近岸接收环境的富营养化是一个全球性问题，尤其是在集约化农业生产区的下游地区。《大堡礁 2050 年水质改善计划》（2017-2022 年）为减少进入大堡礁的污染物负荷设定了雄心勃勃的目标，这些污染物负荷来自于相关农业集水区。在区域尺度上，湿热带末端集水区目标是将溶解无机氮（DIN）的负荷减少 60%，这是 2012-2013 年人为负荷水平的目标。然而，即使有《大堡礁法规》（2019 年 12 月）的授权和在农场采用最佳养分管理实践的共同努力，这些 DIN 目标也不太可能实现。因此，需要创新和具有成本效益的方法来进一步改善水质。将低洼、边际甘蔗地转变为替代土地用途，这些替代土地用途需要较低或无需投入氮，但仍能为农民提供收入来源，这是一个潜在的有吸引力的解决方案。在本研究中，进行了多准则分析，以确定适合这些替代土地用途的地点。计算了这些土地利用变化对 DIN 减少的成本效益，同时考虑了年金毛利润和土地转换成本的减少。在某些地点（转换成本低且 DIN 减少量高），处理湿地和无氮放牧牛提供了具有成本效益的 DIN 减少，范围在 20-26 美元/公斤 DIN。这与现有的农业推广方法（约 50 美元/公斤 DIN 减少）相比具有优势。生态系统服务湿地（即，为鱼类生产而进行的湿地恢复）-再次在适当的情况下-提供了更具成本效益的前景（11-14 美元/公斤 DIN 减少）。这些结果，结合最佳管理实践，支持了替代土地利用是改善低地、低生产力甘蔗地某些地区水质的具有成本效益的选择的前提。政府的持续投资以及私人市场融资机制可以为支持这种土地利用转变提供适当的资金。这些方法需要通过有针对性的试点项目进行测试和完善，作为实现更广泛的大堡礁水质目标的全景观方法的一部分。
