Blicher-Mathiesen, G. & Sørensen, P. (red). 2020. Baseline 2027 for udvalgte elementer. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 120 s. - Teknisk rapport nr. 184.
http://dce2.au.dk/pub/TR184.pdf
In the beginning of 2019, the Danish Environmental Protection Agency (EPA) requested a baseline projection for 2027, predicting the effects of selected elements on the development of nitrate leaching from the root zone and the load of phosphorus to streams and lakes in Denmark. In this context, the term “baseline” covers the effect of measures already adopted (instruments etc.) and other developments in agriculture that may affect the loss of nitrogen (N) and phosphorous (P) from cultivated areas. (See appendices 1a and 1b for details).
The effect of the selected baseline elements as assessed by Aarhus University will together with the effect of other measures assessed by the Danish Ministry of Environment and Food form an overall basis for the expected change in nitrate leaching and phosphorus load from agriculture up to 2027. These estimates are important when assessing the need for action and a programme to ensure a reduction in nutrient loads, which is necessary in order to comply with the EU Water Framework Directive’s objective of good ecological status. The Danish Environmental Protection Agency has also requested an assessment of the effects on nitrogen loss using the measures “afforestation” and ”stop of cultivation of agricultural areas located on soil having high organic matter“ for a climate mitigation purpose.
In this baseline report, the effects are generally allocated based on the same catchment delineation as in vandområdeplaner 2015-2021, which was also used in baseline 2021. In connection with the preparation of the new water area plans, the delineation of the 23 main water catchments was adjusted for the following six catchment areas: 1.10 The Vadehavet, 2.3 Øresund, 2.5 Smålandshavet, 2.6 Baltic Sea and 4.1 Vidå-Kruså (see figure F.1). In order to illustrate the importance of the adjusted delineation for the six catchment areas, estimations of the reference leaching and the effect of the reduction of the cultivated area were made relative to the adjusted catchment delineation (see also sections 3.1 and 3.11).
In this report, a prognosis for three alternative scenarios for the projection of agricultural production and the derived effect on crop distribution and the production of animal manure has been used as basis. With the scenario “average development of animal production”, nitrogen in animal manure will increase by 8 million kg N, while for the two other scenarios there will be a decrease of 20 million kg N and an increase of 35 million kg N to a total of 258 million kg N in excreted manure. These numbers describe excretion of N from animals, and therefore loss in stables and storage must be deducted in order to obtain the change for fields. Albrektsen et al. (2017) estimates a loss in stables and storage from cattle and pigs corresponding to 10% of N excreted from livestock. In the calculation it is assumed that the number of catch crops, presently used for counteracting increased nitrate leaching losses by use of animal manure, are adjusted to the future change in production of animal manure N.
The following baseline elements have been assessed: decrease in the cultivated area, afforestation, increased organic production, use of anaerobic digestion (biogas) and recycled wastes, decline in atmospheric deposition, harvesting of grass silage rather than grazing, development in crop yields and economically optimal nitrogen norms. The different scenarios for forecasted animal production have been incorporated into the projection of cutting of grass silage rather than grazing and in the development of yields and the economically optimal fertiliser norm. Two scenarios are assessed for afforestation, one with an expected increase in afforestation of 17,100 ha, which is equivalent to the growth rate in afforestation since 2000 until 2017 and a second scenario with an increase of 28.800 ha, which is the political target for increase in forests.
The two scenarios for afforestation affects the element decrease in cultivated area, thus this element is also calculated with two scenarios.
The assessment of the effect on nitrate leaching for the individual baseline elements is summarised in table 1. Expected changes in nitrate leaching are, where possible, indicated as an interval on the basis of an uncertainty assessment, where minimum indicates “the least possible reduction of leaching” and maximum indicates “the highest possible reduction of leaching”.
The development of crop yields is calculated together with the development of the economically optimal nitrogen norms as there is a link between increased yields and increased norms. It is also assumed that the leaching is best estimated on the basis of the difference between the development of nitrogen norms and nitrogen yields (change in surface field nitrogen balance).
This assessment of baseline elements (table 1) shows an expected decrease in nitrate leaching up to 2027 as a result of a reduction in the atmospheric deposition of nitrogen, which depends on the prognosis for the development of nitrogen emissions and on the EU countries’ complying with the emission ceilings adopted by the NEC directive for 2027/2030. In addition, it is expected, in particular, that development in the organic farming area and the decline in the cultivated area and afforestation will contribute to lower nitrate leaching towards 2027. There is considerable uncertainty about the effects of the development of nitrogen norms and nitrogen yields on nitrate leaching, especially in relation to the development of the crop composition. However, increased nitrate leaching is expected due to increased climate-related nitrogen load. Expected decrease in nitrate leaching for further use of biogassing and of waste product as well as increase in cut of silage instead of grazing was evaluated to be below 100 t N and is therefore below an unsecure minimum target. The numbers for those baseline elements are not include in table 1 and the effect is neither distributed to the 23 main catchments.
A significant part of the expected baseline effect will not have full impact in 2027 as the expected impact on nitrate leaching is assessed as the effect appearing within a time frame of 5-10 years. It should also be added that there will be a certain time delay from the implementation of the measure until an actual effect can be observed on the leaching from the root zone and the load to coastal waters, and the actual leaching is also affected by year-to-year variations in weather conditions, cf. section 2.6 on time frame and time delay.
In relation to phosphorus, a decline of the load is expected for both of the baseline elements “cultivated area” and “afforestation” (table 2). Also here, the extent of the decrease depends on the political objective forming the basis for the calculation.
The baseline effect has been assessed as a future projection, and there is therefore a certain degree of uncertainty as to whether the actual development will deviate from the projected development. Therefore, AU recommends follow-up assessments to be made of whether the development follows the expectations. It is also important to look at whether new measures will be introduced to reduce the nitrate leaching and phosphorus load, including new measures to meet Denmark’s objective of lover CO2 emissions. In this baseline 2027, an overall description is included of the potential for nitrogen and phosphorous removal by wetting and removing carbon-rich lowland areas from agricultural production, two expectedly significant measures for achieving the objective of reducing the agricultural climate impact.
In this baseline, it has also been shown that increased runoff and large year-to-year variations in e.g. precipitation and temperature can counteract and overshadow the effect of measures and baseline elements and that delays in nitrogen turnover and in the water's transport routes from field to coastal waters may have an impact as well. Regional calculations of flow-weighted total N and nitrate concentrations in the discharged water to coastal waters for catchments with gauging stations show that the year-to-year variation is large in the two regions of Funen and Zealand and that changes in the flow-weighted concentrations therefore should be seen over a number of years to evaluate the effect of measures on the nitrogen load into coastal waters.
