Indicator 15.2 Eutrophication of ecosystems

Text from the Indicator Report 2022 

Nitrogen, which escapes into the atmosphere bonded in ammonia and nitrogen oxides, can be introduced into ecosystems in gaseous form, dissolved in rain, or as a component of particulate matter. Emissions of ammonia and nitrogen oxides are depicted as part of indicator 3.2.a on emissions of air pollutants, and developments in that area directly affect the eutrophication of ecosystems. The sensitive ecosystems covered in the calculations for this indicator are forests, natural grassland, wetlands, marshes and heathland.

Excessive inputs of nitrogen compounds from the air into land ecosystems can result in nutrient imbalances. The alterations in nutrient availability can lead, for example, to changes in the species composition of an ecosystem, with organisms which prefer nitrogen-poor locations being displaced by nitrogen-loving species. Meanwhile, many plants can be rendered vulnerable to frost, drought and pests by changes in nutrient availability. The effects of excessive nitrogen inputs often take several years to manifest themselves. Likewise, the positive effects of reduced inputs will become apparent only after an extended period.

For the purposes of evaluating nitrogen inputs, ecosystem-specific critical loads are determined which represent the saturation points below which, based on the latest knowledge available, the structures, functions and biological communities of an ecosystem remain protected. In total, around 11 million hectares, almost one third of the entire area of Germany, are assessed in this way.

In 2019, the critical loads for harmful nitrogen inputs were exceeded on 69 % of the area of all the sensitive ecosystems assessed in Germany. Excesses were particularly high in parts of northern Germany, where agricultural activity releases large quantities of reactive nitrogen compounds.

Between 2000 and 2015, the proportion of areas in which critical loads for nitrogen were exceeded was reduced by 15 percentage points. The indicator rose again slightly in the subsequent year before returning to the 2011 level by 2019. The share of land where nitrogen was in excess of the critical load has thus not fallen any further since 2015.

The calculations for this indicator are produced by the German Environment Agency and derived from two data sets. The first of these is the critical-load data set, which the German Environment Agency provides for the purposes of international reporting under the aegis of the Geneva Convention on Long-Range Transboundary Air Pollution (CLRTAP). The tools used to determine that data set include the soil overview map of Germany, the map showing average annual rates of percolation into the soil, the map of land-use distribution and climatological data for Germany. The second data set comprises a time series of nitrogen inputs in Germany and was compiled as part of the PINETI IV (Pollutant INput and EcosysTem Impact) project.

The synoptic table provides information about the evaluation of the indicator in previous years. It shows if the weather symbol assigned to an indicator was rather stable or volatile in the past years. (Evaluation of the Indicator Report 2022 )

Indicator	15.2 Eutrophication of ecosystems
Target	Reduction by 35 % by 2030 compared to 2005
Year	2016	2017	2018	2019
Evaluation	No assess­ment possible