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EU Water Framework Directive and Danish agriculture in 1900

The work with the establishment of reference conditions in Danish coastal waters has so far been based on the distribution of eelgrass around 1900, and current measurements of nitrogen concentration in watercourses with virtually no agricultural activity, as well as estimated historical national nitrogen balances. In a new publication in the international journal Ambio, researchers from Aarhus University review the problems surrounding the assumptions about low nitrogen emissions from agriculture around 1900. In addition, they propose an alternative method, which is based on land use at parish level, collected around 1900, combined with measurements from contemporary field trials with the year 1900-relevant cultivation, as a starting point for calculating nitrogen emissions.

2021.04.14 | Camilla Brodam

Photo: Janne Hansen

The Danish authorities' goals for the biological quality of coastal waters are based on the EU Water Framework Directive, and this forms the basis for calculating what it takes to re-establish a good ecological condition. The directive presupposes that a reference state can be established for a given body of water, which corresponds to a state virtually unaffected by human activity.

In Denmark, the ecological condition in 1900 has previously been highlighted as suitable for this reference state, but a recognition that farming in 1900 probably did not, as previously assumed, have a very low nitrogen leaching is in 2020 referenced in an advisory note from DCE – National Centre for Environment and Energy. It is this realisation that is now published in a scientific article. It is based on the historical distribution of eelgrass and measurements of visibility depth in the sea. This visibility depth can be converted to the concentration of chlorophyll and nitrogen in the water.

The reference state in Danish coastal waters in 1900 has been based on measurements in contemporary natural watercourses from catchments with virtually no agricultural activity and with the inclusion of estimates for the national N balance in 1900.

“However, this starting point is criticisable, as in the year 1900 there was agricultural activity on 75% of the land area. In the article, we review the issues surrounding the use of the proposed basis for determining the reference state. In addition, we present an alternative method for determining nitrogen emissions from agriculture, which is based on land use at parish level collected around 1900 combined with measurements from current field trials with 1900-relevant cultivation," says Professor Jørgen Eriksen, section leader at the Department of Agroecology at Aarhus University .

Parish data

From the middle of the 19th century, at 5-10 year intervals for each parish, a detailed inventory was made of how the land was cultivated, or in other words, how the area of ​​the parish was used. For the year 1896, the use was divided into 34 categories. For the part of Southern Jutland which at that time was under German administration, the inventory is from the year 1900 and has 51 categories for use.

"Although it is not new that a large part of Denmark was agricultural land at that time, it is incredibly fascinating that there are such detailed statistics," says Jørgen Eriksen.

The inventory shows a collected agriculture with large amounts of livestock, corresponding to 2.6 million cattle, and 75% of the landarea was cultivated. However, agriculture was very different from modern agriculture. The yields were low, the fields had more weeds, the was virtually no use of commercial fertilisers, and the cultivation practice resulted in low nitrogen utilisation, including regular use of black fallow. In return, there were more legumes. However, lack of capacity for collection and storage of livestock manure and inappropriate use of the same paved the way for low nitrogen utilisation.

“When you combine parish data for land use with measurements in current experiments with 1900-relevant cultivation, it provides a basis for a realistic estimate of the nitrogen loss from the root zone in 1900. And with this method we find an average N concentration in the discharge from the root zone, which is close to the equivalent for contemporary agriculture," says Professor Jørgen E. Olesen, Head of Department of Agroecology, and continues:" Combined with hydrological models that take into account the retention of the landscape, we expect that we can find a credible estimate for the leaching to coastal waters in 1900 ”. 

In other words, according to the researchers, it is unlikely that there was a very low or almost no nitrate leaching in the year 1900, when cultivation practices and land use are included in the calculations.

“Agricultural operations in 1900 do not provide evidence that nitrate leaching should have been low in 1900. Thus, Danish coastal waters can hardly have been almost unaffected by human activity. We must therefore conclude that it is not probable that the year 1900 can be used as a reference state for the Water Framework Directive,” concludes Jørgen E. Olesen.

Additional information

We strive to ensure that all our articles live up to the Danish universities' principles for good research communication(scroll down to find the English version on the web-site). Because of this the article will be supplemented with the following information:

FundingThe Danish Environmental Protection Agency and the Department of Agroecology

In connection with this work, the team came to the realization that farming in 1900 probably did not, as previously assumed, have a very low nitrogen leaching. This has previously been referenced in an advisory note from DCE, Reference inputs of nitrogen for use in Water Plan 3, Note from DCE - National Center for Environment and Energy, 6 January 2020, 3pp. It is this realization that is now published in a scientific article. It appears from the DCE advisory note:

SS2: Preliminary results from an ongoing project regarding. estimation of the nutrient inputs to the sea in the year 1900, however, indicates nutrient inputs of a size which is significantly elevated in relation to the levels seen in contemporary watercourses with weak human impact. The reason for this is that the volume of agricultural activities, the loss of nutrients from these activities and the supply of urban wastewater were already very significant at that time, and the supplies of nutrients to the sea can therefore not reasonably be assumed to have been unaffected or only weakly affected. of human activity. The inputs in the year 1900 can therefore not be considered as a reference input sensu VRD and as a result can not be used to calculate the reference state for e.g. the chlorophyll indicator in coastal waters for use in Water Plan 3.

Read moreYou can read the article ”Land-use and agriculture in Denmark around year 1900 and the quest for EU Water Framework Directive reference conditions in coastal waters”. It is published in the scientific journal Ambio, and is written by Bent T. Christensen, Birger F. Pedersen, Jørgen E. Olesen and Jørgen Eriksen. 

Professor Jørgen Eriksen, Department of Agroecology, Aarhus University. Tel .: 51680554. E-mail: jorgen.eriksen@agro.au.dk 

Professor Jørgen E. Olesen, Department of Agroecology, Aarhus University. Tel .: 40821659. E-mail: jeo@agro.au.dk 

Research, Agro, DCA, Nature, environment and climate