Department of Agroecology, Aarhus University, AU-Foulum, Blichers Allé 20, P.O. Box 50, 8830, Tjele, Denmark.
Ambio. 2021 Oct;50(10):1882-1893. doi: 10.1007/s13280-021-01536-8. Epub 2021 Mar 18.
The EU Water Framework Directive (WFD) aims to protect the ecological status of coastal waters. To establish acceptable boundaries between good and moderate ecological status, the WFD calls for reference conditions practically undisturbed by human impact. For Denmark, the nitrogen (N) concentrations present around year 1900 have been suggested to represent reference conditions. As the N load of coastal waters relates closely to runoff from land, any reduction in load links to agricultural activity. We challenge the current use of historical N balances to establish WFD reference conditions and initiate an alternative approach based on parish-level land-use statistics collected 1896/1900 and N concentrations in root zone percolates from experiments with year 1900-relevant management. This approach may be more widely applicable for landscapes with detailed historic information on agricultural activity. Using this approach, we find an average N concentration in root zone percolates that is close to that of current agriculture. Thus, considering Danish coastal waters to be practically unaffected by human activity around year 1900 remains futile as 75% of the land area was subject to agricultural activity with a substantial potential for N loss to the environment. It appears unlikely that the ecological state of coastal waters around year 1900 may serve as WFD reference condition.
欧盟水框架指令（WFD）旨在保护沿海海域的生态状况。为了在良好和中等生态状况之间建立可接受的界限，WFD 呼吁参考受人类影响较小的条件。对于丹麦来说，建议将 1900 年左右的氮（N）浓度作为参考条件。由于沿海海域的氮负荷与陆地径流密切相关，任何减少负荷都与农业活动有关。我们质疑当前使用历史氮平衡来建立 WFD 参考条件，并提出一种基于 1896/1900 年收集的教区土地利用统计数据和与 1900 年相关管理的根区渗滤物中氮浓度的替代方法。这种方法可能更适用于具有详细农业活动历史信息的景观。使用这种方法，我们发现根区渗滤物中的平均氮浓度接近当前农业的氮浓度。因此，认为丹麦沿海海域在 1900 年左右基本不受人类活动的影响仍然是徒劳的，因为 75%的土地面积都有大量氮向环境中流失的农业活动。看来，1900 年左右的沿海海域的生态状况不太可能作为 WFD 的参考条件。
