Executive summary

Nature of the problem

• Nitrogen (N) budgets of agricultural systems give important information for assessing the impact of N inputs on the environment, and identify levers for action.

Approaches

• N budgets of agro-ecosystems in the 27 EU countries are established for the year 2000, considering N inputs by fertiliser application, manure excretion, atmospheric deposition and crop fixation, and N outputs by plant uptake, gaseous emissions, mineralisation, leaching and runoff.

• Country N budgets for agro-ecosystems are based on the models INTEGRATOR, IDEAg, MITERRA and IMAGE. Fine geographic distribution is depicted with the former two models, which have higher spatial resolution. INTEGRATOR is the only available model for calculating non-agricultural terrestrial N budgets systems.

Key findings/state of knowledge

• For EU-27, the models estimate a comparable total N input in European agriculture, i.e. 23.3–25.7 Mton N yr−1, but N uptake varies largely from 11.3–15.4 Mton N yr−1, leading to total N surpluses varying from 10.4–13.2 Mton N yr−1. Despite this variation, the overall difference at EU-27 is small for the emissions of NH3 (2.8–3.1 Mton N yr−1) and N2O (0.33–0.43 Mton N yr−1) but estimates vary largely at a regional scale. The estimated sum of N leaching and runoff at EU-27 is roughly equal to the sum of NH3, N2O and NOx emissions to the atmosphere, but estimates vary by a factor two, from 2.7 to 6.3 Mton N yr−1.

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Executive summary

Nature of the problem

• Most regional watersheds in Europe constitute managed human territories importing large amounts of new reactive nitrogen.

• As a consequence, groundwater, surface freshwater and coastal seawater are undergoing severe nitrogen contamination and/or eutrophication problems.

Approaches

• A comprehensive evaluation of net anthropogenic inputs of reactive nitrogen (NANI) through atmospheric deposition, crop N fixation, fertiliser use and import of food and feed has been carried out for all European watersheds. A database on N, P and Si fluxes delivered at the basin outlets has been assembled.

• A number of modelling approaches based on either statistical regression analysis or mechanistic description of the processes involved in nitrogen transfer and transformations have been developed for relating N inputs to watersheds to outputs into coastal marine ecosystems.

Key findings/state of knowledge

• Throughout Europe, NANI represents 3700 kgN/km²/yr (range, 0–8400 depending on the watershed), i.e. five times the background rate of natural N2 fixation.

• A mean of approximately 78% of NANI does not reach the basin outlet, but instead is stored (in soils, sediments or ground water) or eliminated to the atmosphere as reactive N forms or as N2.

• N delivery to the European marine coastal zone totals 810 kgN/km²/yr (range, 200–4000 depending on the watershed), about four times the natural background. In areas of limited availability of silica, these inputs cause harmful algal blooms.

Executive summary

Nature of the problem

• Reactive nitrogen has both positive and negative effects on ecosystems and human health. Reactive nitrogen is formed through the use of fossil fuels releasing large amounts of nitrogen oxides into the atmosphere and through the production of ammonia by the Haber–Bosch process and using it in agriculture to increase our food, feed and fuel production. While the use of nitrogen as a fertilizer and chemical product has brought enormous benefits, losses of fertilizer nitrogen and combustion nitrogen to the environment lead to many side effects on human health, ecosystem health, biodiversity and climate.

Approaches

• The European nitrogen problem is placed in a global perspective, showing the European nitrogen fixation, transport and environmental impacts compared with different regions of the globe.

Key findings/state of knowledge

• Humans, largely through agriculture, but also through burning of fossil fuels, have had a huge impact on the nitrogen budget of the Earth. Europe is one of the leading producers of reactive nitrogen, but it is also the first region in the world where the issue was recognized and in some parts of Europe the reactive nitrogen losses to the environment started to decrease. Europe is a nitrogen hotspot in the world with high nitrogen export through rivers to the coast, NOx and particulate matter concentrations and 10% of the global N2O emissions.

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Executive summary

Nature of the problem

• Anthropogenic increase of nitrogen in water poses direct threats to human and aquatic ecosystems. High nitrate concentrations in drinking water are dangerous for human health. In aquatic ecosystems the nitrogen enrichment produces eutrophication, which is responsible for toxic algal blooms, water anoxia, fish kills and habitat and biodiversity loss.

• The continuous nitrogen export to waters reduces the capacity of aquatic ecosystems to absorb, reorganise and adapt to external stress, increasing their vulnerability to future unexpected natural or climate events.

Key findings/state of knowledge

• Nitrogen concentrations in European rivers, lakes, aquifers and coastal waters are high in many regions. In addition nitrate concentrations are increasing in groundwaters, threatening the long term quality of the resource.

• In Europe, nitrogen pressures occur over large areas, implying elevated costs for meeting the long-term good chemical and ecological water quality requirements. A significant part of the European population could be potentially exposed to high nitrate values in drinking water if adequate treatments were not in place. Furthermore many of European aquatic ecosystems are eutrophic or at risk of eutrophication.

• Nitrogen pressures have reduced biodiversity and damaged the resilience of aquatic ecosystems and continue to pose a threat to the aquatic environment and to the provision of goods and services from the aquatic ecosystems.

• Even under favourable land use scenarios the nitrogen export to European waters and seas is likely to remain significant in the near future. The effects of climate change on nitrogen export to water are still uncertain.