Executive summary

Nature of the problem

• Europe, and especially the European Union (EU), has many governmental policy measures aimed at decreasing unwanted reactive nitrogen (Nr) emissions from combustion, agriculture and urban wastes. Many of these policy measures have an ‘effects-based approach’, and focus on single Nr compounds, single sectors and either on air or waters.

• This chapter addresses the origin, objectives and targets of EU policy measures related to Nr emissions, considers which instruments are being used to implement the policies and briefly discusses the effects of the policy measures.

Approaches

• The chapter starts with a brief description of the basic elements of governmental policy measures.

• A review of the main international conventions and EU policies related to emissions of Nr to air and water is then provided.

• Finally the chapter provides a semi-quantitative assessment of the effectiveness and efficiency of European policy measures.

Key findings/state of knowledge

• International conventions and other treaties have played a key role in raising awareness and establishing policy measures for Nr emissions abatement in EU through so-called Directives and Regulations.

• There are many different EU Directives, often addressing individual Nr compounds from individual sectors (e.g. NOx emissions from combustion; NH3 emissions from agriculture, pollution of groundwater and surface water by nitrates from agriculture, discharge of total nitrogen from urban sewage to surface waters).

• […]

Executive summary

Nature of the problem

• Biodiversity is the variability among living organisms, from genes to the biosphere. The value of biodiversity is multifold, from preserving the integrity of the biosphere as a whole, to providing food and medicines, to spiritual and aesthetic well-being.

• One of the major drivers of biodiversity loss in Europe is atmospheric deposition of reactive nitrogen (Nr).

Approaches

• This chapter focuses on Nr impacts on European plant species diversity; in particular, the number and abundance of different species in a given area, and the presence of characteristic species of sensitive ecosystems.

• We summarise both the scientific and the policy aspects of Nr impacts on diversity and identify, using a range of evidence, the most vulnerable ecosystems and regions in Europe.

Key findings/state of knowledge

• Reactive nitrogen impacts vegetation diversity through direct foliar damage, eutrophication, acidification, and susceptibility to secondary stress.

• Species and communities most sensitive to chronically elevated Nr deposition are those that are adapted to low nutrient levels, or are poorly buffered against acidification. Grassland, heathland, peatland, forest, and arctic/montane ecosystems are recognised as vulnerable habitats in Europe; other habitats may be vulnerable but are still poorly studied.

• It is not yet clear if different wet-deposited forms of Nr (e.g. nitrate, NO3− versus ammonium, NH4+) have different effects on biodiversity. However, gaseous ammonia (NH3) can be particularly harmful to vegetation, especially lower plants, through direct foliar damage.

• […]

Main messages

Too much nitrogen harms the environment and the economy

• Over the past century humans have caused unprecedented changes to the global nitrogen cycle, converting atmospheric di-nitrogen (N2) into many reactive nitrogen (Nr) forms, doubling the total fixation of Nr globally and more than tripling it in Europe.

• The increased use of Nr as fertilizer allows a growing world population, but has considerable adverse effects on the environment and human health. Five key societal threats of Nr can be identified: to water quality, air quality, greenhouse balance, ecosystems and biodiversity, and soil quality.

• Cost–benefit analysis highlights how the overall environmental costs of all Nr losses in Europe (estimated at €70–€320 billion per year at current rates) outweigh the direct economic benefits of Nr in agriculture. The highest societal costs are associated with loss of air quality and water quality, linked to impacts on ecosystems and especially on human health.

Nitrogen cascade and budgets

• The different forms of Nr inter-convert through the environment, so that one atom of Nr may take part in many environmental effects, until it is immobilized or eventually denitrified back to N2. The fate of anthropogenic Nr can therefore be seen as a cascade of Nr forms and effects. The cascade highlights how policy responses to different Nr forms and issues are inter-related, and that a holistic approach is needed, maximizing the abatement synergies and minimizing the trade-offs.

• […]

Executive summary

Nature of the problem

• Environmental problems related to nitrogen concern all economic sectors and impact all media: atmosphere, pedosphere, hydrosphere and anthroposphere.

• Therefore, the integration of fluxes allows an overall coverage of problems related to reactive nitrogen (Nr) in the environment, which is not accessible from sectoral approaches or by focusing on specific media.

Approaches

• This chapter presents a set of high resolution maps showing key elements of the N flux budget across Europe, including N2 and Nr fluxes.

• Comparative nitrogen budgets are also presented for a range of European countries, highlighting the most efficient strategies for mitigating Nr problems at a national scale. A new European Nitrogen Budget (EU-27) is presented on the basis of state-of-the-art Europe-wide models and databases focusing on different segments of Europe's society.

Key findings

• From c. 18 Tg Nr yr−1 input to agriculture in the EU-27, only about 7 Tg Nr yr−1 find their way to the consumer or are further processed by industry.

• Some 3.7 Tg Nr yr−1 is released by the burning of fossil fuels in the EU-27, whereby the contribution of the industry and energy sectors is equal to that of the transport sector. More than 8 Tg Nr yr−1 are disposed of to the hydrosphere, while the EU-27 is a net exporter of reactive nitrogen through atmospheric transport of c. 2.3 Tg Nr yr−1.

• The largest single sink for Nr appears to be denitrification to N2 in European coastal shelf regions (potentially as large as the input of mineral fertilizer, about 11 Tg N yr–1 for the EU-27); however, this sink is also the most uncertain, because of the uncertainty of Nr import from the open ocean.

Executive summary

Nature of the problem

• Reactive nitrogen (Nr) occurs in different forms, arises from a wide range of activities and sources, and leads to environmental impacts over different spatial and temporal scales.

• Integrated approaches to N management are anticipated to provide more effective (larger decreases in unwanted emissions) and /or more efficient (less side effects, less costs) policy measures than policy measures based on single sources and pollutant species.

• There are many notions of integrated approaches, but as yet little consensus about the best integrated approaches. There is also little quantitative empirical evidence of the performance of these approaches in practice.

• The pitfall of integrated approaches is that they may be more complex to agree, leading to a delayed implementation.

Approaches

• Based on recent literature and a discussion among experts, the present chapter provides a conceptual framework for developing integrated approaches to N management.

• Whilst discussing the framework, various examples of existing partially integrated N management approaches have been considered.

• A package of key actions in different sectors is envisaged that, together, should contribute to further developing integrated approaches to N management in the future

Executive summary

Nature of the problem

• Atmospheric emissions of nitrogen oxides and ammonia are contributing to a number of negative effects to human health and ecosystems. These effects include both effects of the primary emissions but more importantly through actions of secondary pollutants such as ground level ozone (O3) and secondary particulate matter (PM).

• The main air pollution effects include effects of nitrogen dioxide to human health, effects from ground level ozone to human health and vegetation and effects from particulate ammonium and nitrate to human health. There is a difficulty of ascribing health effects to NO2 per se at ambient levels rather than considering NO2 as a surrogate for a traffic-derived air pollution mixture.

Approaches

• The chapter gives a brief review of our current understanding of the mechanisms and processes regarding N-containing air pollutants and their effects on human health, vegetation (effects of reactive nitrogen on ecosystems through eutrophication and acidification is treated in Dise et al., 2011; Velthof et al., 2011, Chapters 20 and 21, this volume) and materials. It presents historical development, current situation and outlines future perspectives of reactive nitrogen related air pollution and its effects in Europe in relation to national and EU legislation on emission limitation and air quality control.

Key findings/state of knowledge

• In the EU-27 countries, 60% of the population lives in areas where the annual EU limit value of NO2 is exceeded. Air quality standards for nitrogen dioxide are exceeded mainly in urban areas. Concentrations have decreased since 1990, although the downward trends have been smaller or even disappeared after 2000.

• […]

Executive summary

Nature of the problem

• The future effects of nitrogen in the environment will depend on the extent of nitrogen use and the practical application techniques of nitrogen in a similar way as in the past. Projections and scenarios are appropriate tools for extrapolating current knowledge into the future. However, these tools will not allow future system turnovers to be predicted.

Approaches

• In principle, scenarios of nitrogen use follow the approaches currently used for air pollution, climate, or ecosystem projections. Short-term projections (to 2030) are developed using a ‘baseline’ path of development, which considers abatement options that are consistent with European policy. For medium-term projections (to 2050) and long-term projections, the European Nitrogen Assessment (ENA) applies a ‘storyline’ approach similar to that used in the IPCC SRES scenarios. Beyond 2050 in particular, such storylines also take into account technological and behavioral shifts.

Key findings/state of knowledge

• The ENA distinguishes between driver-oriented and effect-oriented factors determining nitrogen use. Parameters that cause changes in nitrogen fixation or application are called drivers. In a driver-based approach, it is assumed that any variation of these parameters will also trigger a change in nitrogen pollution. In an effect-based approach, as the adverse effects of nitrogen become evident in the environment, introduction of nitrogen abatement legislation requiring the application of more efficient abatement measures is expected. This approach needs to rely on a target that is likely to be maintained in the future (e.g. human health). Nitrogen abatement legislation based on such targets will aim to counter any growth in adverse environmental effects that occur as a result of increased nitrogen application.

• […]