Aarhus Universitets segl

No. 453: Aquatic Environment and Nature 2019. NOVANA.

Jung-Madsen, S., Boutrup, S., Nielsen, V.V., Hansen, A.S., Svendsen, L.M.,, Fredshavn, J., Blicher-Mathiesen, G., Thodsen, H. Kallestup, H., Hansen, J.W., Høgslund, S., Johansson, Nygaard, B., Kjær, C., Nielsen, R.D., L.S., Ellermann, T., Thorling, L. & Nielsen, L. 2021. Vandmiljø ogNatur 2019. NOVANA. Tilstand og udvikling - faglig sammenfatning. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 78 s. - Videnskabelig rapport nr. 453  http://dce2.au.dk/pub/SR453.pdf


For the sake of clarity, the summary is very brief. This means that the underlying data basis and reservations, e.g. in relation to uncertainties of results or specific conditions in a single year, are not included, but can be found in the scientific background reports. It is therefore necessary to consult these scientific reports if, for example, the results are to be used in a decision-making process.

The reporting of data is affected by the laboratory error analyses of total N and total P that were made for surface water in 2016 and the first quarter of of 2017. It has been possible to restore data on total N and total P in streams for use in the calculation of nutrient transport and nutrient inputs to the sea from all of 2016 and part of 2017, when the analysis errors occurred.

The analyses of total N and P total have the same type of error from the period 2009-14 as well as a corrective requirement in the first half of 2015. In connection with the present reporting, data has been restored in streams for the period 2009-2015, where total N in streams in the period 2009-2014 has been corrected by approx. 6% for ordinary streams and approx. 20% for streams that are lake drains. The corresponding figures for 2015 are 3.8% and 4.3%, respectively. Currently, total P has not been corrected. The corrected data form the basis for the calculation of the nutrient transport of N and P in this report. With this correction, DCE can discard the academic reservations related to total N-concentrations in streams from this period due to analysis errors.

For total N concentration in lake samples, analysis errors were found in the period 2007 through the first quarter of 2017. DCE has therefore recommended that total N concentrations be corrected for this period (Larsen et al. 2020). However, such a correction has not yet been made, and the development in the overall N concentration in this period must therefore be interpreted with reservation. In the reporting of data from the monitoring of lakes, the analysis results of total N and total P from 2016 and the first quarter of 2017 have so far been omitted.

For the sea, total N and total P have not been reported, as the samples have not been definitively restored. On the other hand, there are no errors in the analyses of nitrates and phosphate, which is why they have been included in this year's report where relevant. 


Since 1990, there has been a significant reduction in the content of nitrogen in the surface water environment in general. This generally correlates well with a reduction of sources, listed here as the development in fertiliser use and in emissions from wastewater treatment plants. In 2019, the nitrogen surplus (nitrogen added to the field minus nitrogen removed by harvesting) was the lowest since 2013 and 2014 due to the high yields in 2019. A possible effect of changes in the nitrogen surplus on the leaching of nitrogen depends on a number of factors, including catch crops.

In 2019, the total nitrogen input from soil to sea was approximately 74,000 tons N – against 50,000 tons N in 2018. If the year-to-year variations in the runoff (normalised) are taken into account, the inflow in 2019 was approx. 67,000 tons N and was, thus, still higher than in 2018, where it was 55,000 tons. Among other things, this reflects that the normalisation does not take into account the effect e.g. of the drought-affected harvest in 2018 with a subsequent abnormally large nitrogen pool in the soil. In addition, the dry autumn in 2018 meant that part of the nitrogen that would normally have been leached in 2018 was not leached until the beginning of 2019.

Overall, nitrogen inputs from land to sea have been at the same level for the past approx. 10 years, but with a relatively low input in 2018 followed by a high input in 2019, a pattern which is assessed to be particularly attributable to the specific weather conditions in these two years and the derived effects on the agricultural sector.

It is still too early to assess the overall effect of the increased consumption of nitrogen and the compensatory catch crops, which were made possible by the Food and Agriculture Package in 2015.

Since 1989, there has been a significant reduction in the phosphorus content in fresh and coastal surface water, which is mainly driven by improved wastewater treatment – primarily at the large purification plants and separate industrial emitters – up to approx. year 2000. For streams, the concentration of total phosphorus has decreased by almost 40% during the period, while the reduction in phosphorus input to the sea has been reduced by about 70%. In the coastal surface water, a reduction was found in the concentration of inorganic phosphorus of almost 80%.

Metals and organic environmentally hazardous substances

Through precipitation, surface water and soil receive much more zinc than any other metals. There was a significant decrease in the input from 1989 till about the turn of the millennium. In the past approx. 10 years, the input has only declined slightly compared to previous years, and for zinc there has been a slight increase.

Pesticides are among the organic environmentally hazardous substances included in the monitoring. As in previous years, the pesticide prosulphocarb, which is used on winter cereals in the autumn months, was found in the largest quantity among the substances that were measured inprecipitation. The wet deposition of prosulfocarb in 2019 was significantly higher than in 2018 due to greater rainfall in the autumn of 2019.


In 2019, threshold values for nitrogen dioxide and particulate matter were not exceeded. The threshold requiring informing the public of high ozone levels (180 μg/m3 as an hourly mean) was exceeded once on Sealand and Funen in the summer of 2019.

For all air pollutants, there has been a marked decrease in concentrations in the measurement period. Limit and target values were not exceeded for pollutant components covered by the EU’s air quality directives. For the vast majority, air concentrations decreased, which is generally consistent with the development in emissions. However, for a few of the air pollution components no decrease has been found, e.g. for ozone and copper.

Calculations on the health effects of the total air pollution in Denmark show about 4,600 premature deaths as an annual average for the period 2019. The number of premature deaths is approximately 10% higher than stated in the last annual report for 2018. The increase from last year is not due to increased air pollution, but rather to major changes in the model calculations, including the use of updated records of emissions, changes in the meteorological data used and an improved calibration method. The total external costs related to air pollution in Denmark are estimated to about DKK 85 billion in 2019.


The aquatic environment action plans have impacted the nitrate content in groundwater. This is reflected in a clear correlation between the nitrate content of the oxygen-containing groundwater as a function of the age of the groundwater and the surplus of nitrogen from agricultural production in a given year. For the past six years, the nitrate content of the oxygen-containing groundwater has, on average, been below the threshold value.

In 2019, one or more pesticides or degradation products from pesticides were found in 58% of the surveyed input in groundwater monitoring. The threshold value of 0.1 µg/l was exceeded in 22.6% of the intakes. The threshold value for the sum of measured substances of 0.5 μg/l was exceeded in 9.2% of the intakes. The proportion of the studied intakes, where pesticides were found, was greater in 2018 and 2019 than in the previous years. This is attributed to the fact that the groundwater monitoring in 2018 and 2019 included some pesticide degradation products that had not previously been studied or had only been studied in a few intakes. These substances were found with greater frequency than previously studied substances. Since 2017, several of these degradation products have been studied in the waterworks' production wells. This has meant that contents above the requirement value have been found in a greater number of boreholes than in previous years.


This year's report on streams includes the results of the biological studies from the control-monitoring’s condition stations, examined during the period 2017-2019. Data from this type of station has not previously been reported. The results show that the organic state is generally low in the condition stations, as 3-57% of the stations meet the target in relation to the Water Framework directive's objectives for small animals (57%), aquatic plants (29%) and fish (3-44%).

As only a subset of the 3,800 condition stations have been studied in the period 2017-2021, it is not possible, on the basis of these analyses, to say anything about the general condition at this type of station. For fish in particular, the data base is very sparse.


The lakes that are part of the control monitoring of the status show general improvement in the water chemistry parameters since 1989. However, the improvement was primarily seen at the beginning of the period. When comparing the trend between the last two six-year periods (2008-2013 and 2014-2019) a general deterioration is seen, as there is a significant increase in the lakes’ content of total N, total P and chlorophyll. The most significant changes are seen for the nutrients; there is no significant change in Secchi depth. However, reservations must be made in as far that the results for nutrients may be affected by the probable analytical errors in the period 2007-2017.

Marine areas

The prevalence of oxygen depletion in September 2019 was at par with 2017 and slightly less than in 2018, and almost half of the oxygen depletion area was affected by heavy oxygen depletion. The prevalence of oxygen depletion in September has fluctuated somewhat over the past approx. 10 years with relatively widespread oxygen depletion in 2009, decreased prevalence in the years 2010-12 and medium prevalence in the years 2013-2017, interrupted by relatively widespread oxygen depletion in 2016. A significant part of the variation in the prevalence of oxygen depletion is due to weather conditions (primarily wind and temperature). However, the nutrient supply is a fundamental factor in the development of widespread oxygen depletion.

The amount of planktonic algae in coastal waters, measured as chlorophyll a, was nearly at the same level as in 2016- 2018 (a little above 2016, but below 2016) and was, thus, above the amount in previous years. The level corresponds to the levels in the 1990s and 2000s. The abundance of marine flora i (eelgrass and seaweed) has generally increased in the years 2009-2013, but the positive development has stagnated in several areas in recent years. The bottom fauna of the open inland waters has shown progress in the number of species since a low point in 2008, but in 2019 there were still indications of poor conditions for the bottom fauna in the North Sea and the Skagerrak and in some coastal areas. Thus, there are mixed signals in relation to the developments in the marine parameters over the past 10 years.


This year, the nature monitoring includes the results of the mapping of 43 terrestrial habitat types in the period 2016-2019. A total of 119,410 hectares have been mapped within the old delimitation of the habitat areas (applicable to November 2018), corresponding to 38% of the land area of the habitats. The adjustments to the Natura 2000 areas' borders have resulted in an increase in the total mapped area of 14,259 hectares. The report analyses the area's changes and state of nature for both the old and the new habitat delimitations.

The monitoring of species in 2019 consisted of a total of eight species of animals, plants and a moss in the Habitats Directive appendices II and IV. They were dormouse, marsh fritillary and Green hawker as well as the vascular plants fen orchid, yellow marsh saxifrage, least moonwort, lady’s slipper orchid and slender green feather-moss.

Bird monitoring includes breeding birds and migratory birds. The report provides the status for 44 breeding birds in Appendix I of the Bird’s Directive, all of which are included in the basis for the selection of the Danish bird protection areas. DCE, Aarhus University, has monitored the status of the cormorant as a breeding bird, and in 2018-2019 the Danish Environmental Agency supervised the remaining bird species. DCE's monitoring of migratory birds includes 49 species, of which two are examined at subspecies level (Taiga Bean goose and Brant goose). After a reorganisation of the programme in 2017, the cadence is now every two years on all counts, except mid-winter and trap bird counts. Since the 1980s, nationwide trap bird counts have been carried out every six years (most recently in 2018). NOVANA-counts of waterfowl are coordinated with the international census and are used in the assessment of the international flyway stocks.