Nitrogen in Europe: activities addressing the European Nitrogen Cycle ENVIRONMENT

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1 Página 1 de 8 Year 28 Nº 111 third quarter 2008 Nitrogen in Europe: activities addressing the European Nitrogen Cycle ENVIRONMENT Nitrogen is an important crosscutting theme over most of the important societal sectors and their direct and indirect influence on environmental problems for Europe: climate change, biodiversity, ecosystem health, human health, ground water pollution, etc. Different efforts have started over the last years addressing nitrogen in an integrated way. Examples of these efforts are: NinE (Nitrogen in Europe), COST Action 729, NitroEurope-IP and the recently established Task Force on Reactive Nitrogen (TFRN). Through these programs scientists and policy makers are challenged to get together and discuss the current state of the complex nitrogen problem and its future solution. By A. BLEEKER 1 *, S. REIS 2, C. BRITTON 2, J.W. ERISMAN 1 & M.A. SUTTON 2. (1) Energy Research Centre of the Netherland - Unit Biomass, Coal and Environmental Research, Petten, The Netherlands (2) Centre for Ecology and Hydrology, Penicuik, United Kingdom * corresponding author: P.O. Box 1, 1755 ZG Petten, The Netherlands tel: , a.bleeker@ecn.nl European ecosystems are under threat from many pressures, including changes in landuse, atmospheric composition and climate. These anthropogenic disturbances lead to major changes in water and nutrient cycles. Globally, one of the most perturbed nutrient cycles is the atmospheric nitrogen cycle: it has been estimated that the present nitrogen cycle is perturbed to more than 80%, whereas the carbon cycle is by comparison perturbed by less than 10%. Intensified agriculture and combustion of fossil fuels increase the amounts of reactive nitrogen, and these compounds will, when released to the environment, have a cascade of effects to human health and ecosystems. Agricultural activities release ammonia (NH 3 ), nitrous oxide (N 2 O) and nitric oxide (NO) to the atmosphere, while nitrate (NO 3 - ) and ammonium (NH + 4 ) are released to aquatic systems. Fossil fuel combustion from stationary and mobile sources is well known to emit nitrogen monoxide (NO) and nitrogen dioxide (NO 2 ) (collectively termed NO x ). Equipment installed in order to reduce emissions of nitrogen oxides e.g. catalytic converters in cars cause emissions of small but significant amounts of NH 3 and N 2 O. Nitrogen in Europe: activities addressing the European Nitrogen Cycle NO and NO 2 react with volatile organic compounds (VOCs) to produce enhanced ground level ozone (O 3 ) concentrations The main drivers of change in the European nitrogen budget are the anthropogenic fixation of nitrogen by agriculture, leading to releases of NH 3, N 2 O, NO and NO - 3, the import of nutrients from other parts in the world through concentrates, food, and high temperature combustion processes, which oxidize a fraction of the atmospheric N 2 to NO x. The presence of excess N in these reactive forms leads to an extremely wide range of environmental The nitrogen cascade may be illustrated by the fate of nitrogen excreted by

2 Página 2 de 8 problems: NO and NO 2 react with volatile organic compounds (VOCs) to produce enhanced ground level ozone (O 3 ) concentrations, with impacts on crops, natural vegetation and human health. Increased tropospheric formation of ozone is also giving a substantial contribution to the greenhouse effect. NH 3 reacts with atmospheric acids, including HNO 3 from NO x emissions, to produce fine aerosol, such as ammonium nitrate (NH 4 NO 3 ) and ammonium sulphates (e.g. NH 4 HSO 4, (NH 4 ) 2 SO 4 ). These undergo long-range transport in the atmosphere, depositing reactive N many thousands of kilometers from the sources. N containing aerosols enhance light scattering, which reduces visibility and has a direct negative effect on global radiative balance. In addition, N-containing aerosols act as cloud condensation nuclei, providing an indirect global cooling effect. N containing aerosols are respirable, and may be associated with both coronary and respiratory diseases. Deposition of oxidized-n (NO y ) and reduced-n (NH x ) leads to eutrophication of nutrient-poor aquatic and terrestrial ecosystems decreasing biodiversity. In particular, the local inputs of NH x may be very large, leading to biodiversity loss in vulnerable habitats. Deposition of NO y and NH x to terrestrial ecosystems can result in soil acidification, with consequent changes in species composition and water quality. At a European level, the potential acidifying contribution from N is now larger than that from sulphur. Run-off and leaching of agricultural N lead to enhanced - NO 3 concentrations in ground and surface waters, with potential human health risks from drinking-water and changes in aquatic ecosystems. Excess N-flow in rivers and atmospheric deposition to coastal waters lead to euthrophication of marine areas, leading to increased risks of algae blooms and hypoxia. Atmospheric deposition is also an important source of nitrogen in marine ecosystems. N 2 O is a powerful greenhouse gas, which contributes ~12% of the anthropogenic global warming potential, while it also plays a role in stratospheric atmospheric chemistry leading to destruction of high-altitude O 3. The additional N supply from atmospheric deposition also affects CO 2 and CH 4 fluxes between ecosystems and the atmosphere in a positive (sink) and negative (source) way, leading to knock-on effects on the global radiative balance. Nitrogen deposition is of importance for the sequestration of carbon in terrestrial ecosystems, a highly considered method to counteract the increasing concentrations of carbon dioxide. Present fertilization of forests through balanced deposition of N leads both to increased growth and to an increased capacity for carbon sequestration. livestock Excess N-flow in rivers and atmospheric deposition to coastal waters lead to euthrophication of marine areas, leading to increased risks of algae blooms and hypoxia The NinE Logo Present fertilization of forests through balanced deposition of N leads both to increased growth and to an increased capacity for carbon sequestration. Once released into the environment nitrogen compounds may contribute to a cascade of effects before getting into a final sink as N 2 molecules or immobilized in soils or sediments. The nitrogen cascade may be illustrated by the fate of nitrogen excreted by livestock: a significant fraction is emitted as NH 3, with additional losses as N 2 O, NO and NO 3 -. Subsequent Emissions of small but significant amounts of NH 3 and N 2 O.

3 Página 3 de 8 atmospheric deposition of the NH3 leads to further N 2 O and NO emissions and NO 3 - leaching. The atmosphere provides a means to disperse the N widely, resulting in perturbation of the nitrogen cycle in areas remote from direct human intervention. Figure 1. The Nitrogen Cascade (source: Galloway et al - From all the issues described above, it is clear that nitrogen is an important crosscutting theme over most of the important societal sectors and their direct and indirect influence on environmental problems for Europe: climate change, biodiversity, ecosystem health, human health, ground water pollution, etc. This is also addressed in a recent review in the journal Science by Galloway et al (2008), discussing the nitrogen issue in a global perspective. It is clearly stated there that optimizing the need for a key human resource while minimizing its negative consequences, requires an integrated interdisciplinary approach and the development of strategies to decrease nitrogencontaining waste. Nitrogen in European (NinE): Current problems and future solutions A program trying to address the current state of knowledge on the issues related to nitrogen is Nitrogen in Europe (or in short NinE). NinE addresses the issues that will be relevant for solutions for the future, while looking at the European nitrogen cycle as a whole. NinE is a European Science Foundation (ESF) Research Networking Programme that runs for five years from March 2006 and aims to integrate European research and researchers, eventually delivering an assessment report of the state of European nitrogen knowledge, sources, transformations and impacts, as well as establishing a basis to recommend future solutions (see also the section on the European Nitrogen Assessment - ENA - below). Until now, there has never been an assessment of all the interacting problems resulting from excess nitrogen. Previous scientific efforts have focused primarily on the processes of nitrogen turnover and fluxes relevant to individual chemical forms of nitrogen in different environmental compartments or particular environmental problems (see also above). Significant efforts have been made in models that begin to join up the nitrogen cycle and relate it to the carbon cycle, but even these have addressed just a few of the nitrogen problems together. Hence assessments of transboundary air pollution have coupled the issues of acidification, terrestrial eutrophication and ground level ozone

4 Página 4 de 8 from nitrogen oxides and ammonia (e.g. UN-ECE Convention on Long Range Transport of Air Pollution). Current work is now integrating these issues with atmospheric particles and greenhouse gases, but we are still far from a fully integrated assessment for nitrogen. NinE will encourage these linkages to be made, extending the analysis for the first time to cover all nine nitrogen problems. The NinE programme is building the European scientific network necessary to quantify these interactions and underpin the development of future solutions. The NinE Objectives In short NinE has the following objectives (more detailed information is available via To develop the underpinning science that links different forms of nitrogen. Hence detailed studies on a single nitrogen pollutant are not the first priority. Instead, the priority is for studies examining the interchange and relationships between different nitrogen pollutants as nitrogen cascades through the environment. To develop the science linking nitrogen interactions between environmental compartments. Coupled to the above is the need for studies that link nitrogen emissions, transformations and impacts between soils, plants, air and water, and between different contexts, urban-rural, aquatic-marine, biosphere-troposhere-stratosphere etc. To establish approaches at a range of scales, from physiological scale, patch scale, landscapes (e.g. 25 km 2 ), regional watersheds (e.g km 2 ) to regions of Europe and the whole continent. Each of the scales is relevant, but the larger scales that allow explicit assessment of the nitrogen cascade are particularly relevant (landscapes to continental). To refine methodologies for relating information between different spatial and temporal scales. It is a major scientific challenge to carry information developed at finer scales to larger scale models, while also posing a challenge for the different science communities to interact successfully. To apply the analyses of NinE in selected case studies across Europe. These may include contrasting case-study landscapes, major watersheds and larger contrasting regions of Europe, including the comparison between source and sink areas for nitrogen. To establish a meta-database of nitrogen research activities and assessments that integrate different nitrogen forms, interactions and scales. Such a metadatabase would take the widest possible scope, including process analyses and case studies, providing access to both datasets and reports. To prepare a major assessment report of covering the state of knowledge on interlinked problems of Nitrogen in Europe. The assessment report would be informed by the results of the scientific activity of NinE and draw extensively on the NinE meta-database. The NinE Logo The NinE logo reflects the challenge to interlink 9 major environmental problems. The 9 problems being addressed are: Aquatic Eutrophication Coastal & Marine Eutrophication Terrestrial Eutrophication & Biodiversity Acidification of soils & waters Stratospheric chemistry & ozone

5 Página 5 de 8 Greenhouse gas & global warming Ozone - vegetation & health Urban air quality & health Particles - health, visibility & global dimming The logo places NinE at the centre of the transdisciplinary network, and also provides a mnemonic for the 9 problems: "ACT AS GROUP". This emphasizes the need to join our efforts in delivering a fully integrated assessment of European nitrogen problems and their future solutions. European Nitrogen Assessment (ENA) As the major outcome of NinE, the European Nitrogen Assessment (ENA in short) will address current nitrogen issues, the cascade effects and the interactions and feedbacks. The ENA provides valuable insight for governments and other stakeholders in the balance between the benefits of fixed nitrogen to society, against the different adverse effects of excess nitrogen in the environment. Much is already known about nitrogen and its transformations in the environment. However, the complexity and extent of the interactions mean that current scientific understanding and policy making has become separated into several parallel streams. By focusing on these separate streams, there is the danger that developing adaptation and mitigation strategies will be far from optimal. The potential for trade-offs or pollution swapping between the mitigation of different nitrogen forms is well established. But, a more comprehensive understanding of the nitrogen cycle is needed to maximize synergies in future strategies. A key challenge from European nitrogen activities is to synthesise science in a form that is useful to governments and society. An assessment is needed that asks the question: How can our scientific understanding of multiple nitrogen effects help Europe develop a more integrated approach to managing nitrogen in the environment? There is a low public understanding of the importance of excess nitrogen as a threat affecting many environmental issues. The complexity of multi-pollutant multi-effect interactions is a major hurdle to improving public awareness. How can the scientific community better communicate the nitrogen challenge facing society? NinE develops the necessary synthesis between nitrogen issues, with the central task of preparing the ENA. The ENA represents a three year effort over 2008 to 2010 bringing together scientists, policy makers and other stakeholders with interests across the full range of nitrogen issues. The ENA represents a process of scientific and policy synthesis that will provide a major review of the role of excess nitrogen on environmental problems. Based on analysis of the problems and interactions, the review will explore the potential to establish integrated solutions and better communicate the implications to society. The ENA report will have 5 major Sections, with 23 chapters. Each chapter will be written by leading international experts, comprising of Lead and Contributing Authors. Under the editorship of the Coordination Team, each chapter will be submitted to international peer review. The early chapters of the ENA report will be developed first, gradually building the understanding of integration, which will feed into development of the later chapters. The ENA process will contribute to bringing the different research and policy communities together, so that later chapters can be more synthetic across scales and issues. The general approach is using workshops funded through NinE to develop groups of chapters. Leading international experts are invited by the Coordination Team to prepare background

6 Página 6 de 8 documents, which will be presented to these workshops. The workshops will be openly advertised through the ENA web portal (hosted by the NinE project - Similarly, the workshop reports will be disseminated through the ENA web portal, being open for interested parties to send comments to Lead Authors and/or the Coordination Team. Other European initiatives Besides NinE other nitrogen activities in Europe are running, addressing the nitrogen cycle in a more or less integrated way. The most important activities are the Task Force on Reactive Nitrogen, NitroEurope and COST Action 729. The following paragraphs will address these activities in more detail. NitroEurope The NitroEurope EU-Integrated Project (or NEU for short) was developed specifically for addressing the prime issues of European N budgets in relation to C cycling and greenhouse gas exchange, while at the same time being aware of the interactions with other environmental issues (Sutton et al., 2007). NEU started in February 2006, runs for 5 years and coordinates the activities of 65 European partner institutes. A key point of integration is the recognition that climate change policy requires integrated assessment of Net Greenhouse gas Exchange (NGE) rather than just CO 2. This is vital for future strategy development, since approaches that maximise CO 2 uptake may not optimize NGE. Apart from the obvious links between N and C cycles, there is a requirement to assess overall ecosystem N budgets, since other Nr losses, e.g. NH 3 emissions and leaching of nitrate (NO - 3 ), are considered as indirect sources of N 2 O emissions under the IPCC methodology. NEU thus recognizes the need to integrate the analysis Nr and GHG at linked field-, farmand landscape-scales, including consideration of the spatial interactions with NH3 emissions and NO3- leaching. Furthermore, Nr gases can form aerosols which affect the radiation balance of the earth. The contribution of aerosol biosphere-atmosphere exchange to N deposition and aerosol production/loss within canopies is needed to calculate Nr budgets and NGE. Similarly, interactions with ecosystem functioning and biodiversity must be considered in order to understand the observed responses of NGE to global change drivers. NitroEurope IP addresses the major question: What is the effect of reactive nitrogen supply on the direction and magnitude of net greenhouse gas budgets for Europe? Key component questions related to this include: What are the quantitative components of ecosystem N budgets and how do these respond to global change? How much does the form of N r (oxidized vs. reduced, wet vs. dry, agric. vs. atmos.) affect ecosystem response, N and C budgets and NGE? What is the effect of changes in atmospheric N deposition and agricultural N inputs over recent decades on the net CO 2 uptake by European ecosystems? Can we simulate the effects of land-management change on NGE at plot, landscape, regional and European scales? Will independent measurement and modelling verify the GHG emissions officially submitted to the UNFCCC? How can the accuracy of these inventories be improved? To what extent would a more-integrated management of the N-cycle and its interactions with the C-cycle have

7 Página 7 de 8 potential to reduce GHG and N r emissions simultaneously? COST Action 729 The COST Action 729 ("Assessing and Managing Nitrogen Fluxes in the Atmosphere-Biosphere System in Europe") started in 2005 and aims at combining the knowledge from various research areas (e.g. NitroEurope and NinE) throughout Europe in order to provide a scientific base for an integrated approach to nitrogen management with a focus on the atmosphere-biosphere interactions. The main objective of the Action is to advance the knowledge in relation to the main economic sectors, interactions with the natural environment and current policies, in order to establish a sound scientific basis for strategies to reduce the environmental impacts of nitrogen. Even though there is increasing knowledge on the causal chain and interactions with other cycles, the tools to assess the whole picture taking all the interactions into account is still lacking. Integrated Assessment Models (IAM) are currently addressing only part of the problems and interactions. Much more development of IAMs is necessary to be able to do a complete assessment and full policy support. This Action, therefore conducts scientific and technical investigations that will allow the computerized calculation by (upgraded) IAMs capable of assessing and managing nitrogen fluxes in the atmospherebiosphere system in Europe on the relevant scales, including both terrestrial and marine contexts, under conditions of changing emissions, policy and climate/meteorology. The Action,focuses on reviewing and synthesis that is needed to develop the IAM modelling approaches. evaluation of existing model components according to recent scientific results. comparing different model systems with regard to developing consensus to better tools. developing better understanding the scientific flux interactions to allow scenario development, and interpretation of resulting scenarios to further inform the science policy dialogue. Task Force on Reactive Nitrogen Coming out of activities of e.g. NinE, NEU and COST Action 729 the Executive Body for the Convention on Long-range Transboundary Air Pollution (UNECE CLTAP) decided in 2007 to establish a Task Force on Reactive Nitrogen (TFRN). In its Decision, the Executive Body defined the long-term goal of the TFRN as developing technical and scientific information, and options which can be used for strategy development across the UNECE to encourage coordination of air pollution policies on nitrogen in the context of the nitrogen cycle and which may be used by other bodies outside the Convention in consideration of other control measures ; The main functions of the Task Force are: To plan and conduct the technical work necessary to develop a better understanding of the integrated, multipollutant nature of reactive nitrogen, particularly in relation to air pollution in context of the nitrogen cycle; To plan and conduct the technical work necessary to assess emissions, transport, budgets, fluxes and effects of nitrogen; To consider how the work of the Task Force would

8 Página 8 de 8 complement the work of other bodies of the Convention, in particular the Task Force on Integrated Assessment Modelling, the Task Force on Emission Inventories and Projections and the Task Force on Modelling and Mapping, as well as that of other international bodies. Conclusions From the paragraphs above, it is clear that 'nitrogen' is addressed in different scientific and policy arenas with an attempt to make linkages between possible nitrogen issues (in terms of sources, receptors, effects, policies). Although there is still a long way to go to understand 'nitrogen' to its full extend, the first activities in the context of NinE, NEU, COST Action 729 and TFRN are very promising. Bringing together scientist and policy makers from different fields and have them discuss a common problem is challenging, but rewarding at the same time - especially when a mutual understanding of the different problems arises from these discussions. References 1. Galloway, J.N., Townsend, A.R., Erisman, J.W., Bekunda, M., Cai, Z., Freney, J.R., Martinelli, L.A., Seitzinger, S.P., Sutton, M.A. (2008) Transformation of the Nitrogen Cycle: Recent Trends, Questions, and Potential Solutions. Science 320, pp Sutton M.A., E. Nemitz, J.W. Erisman, C. Beier, K. Butterbach Bahl, P. Cellier, W. de Vries, F. Cotrufo, U. Skiba, C. Di Marco, S. Jones, P. Laville, J.F. Soussana, B. Loubet, M. Twigg, D. Famulari, J. Whitehead, M.W. Gallagher, A. Neftel, C.R. Flechard, B. Herrmann, P.L. Calanca, J.K. Schjoerring, U. Daemmgen, L. Horvath, Y.S. Tang, B.A. Emmett, A. Tietema, J. Peñuelas, M. Kesik, N. Brueggemann, K. Pilegaard, T. Vesala, C.L. Campbell, J.E. Olesen, U. Dragosits, M.R. Theobald, P. Levy, D.C.Mobbs, R. Milne, N. Viovy, N. Vuichard, J.U. Smith, P. Smith, P. Bergamaschi, D. Fowler and Reis S. (2007) Challenges in quantifying biosphere-atmosphere exchange of nitrogen species. Environmental Pollution 150,