Nitrogen cycle is essential for the sustainability of the human society. We should promote a consolidated research and development (R&D) initiative which aims at understanding its status and its mechanism as well as at establishing technological capability to make it sustainable.
Modification of the environment due to human activities is a serious issue that threatens sustainability of the human society. Modification of the global biogeochemical cycle is one of its most important aspects, along with climate change and biodiversity loss which have already been recognized as major issues internationally. In particular, modification of the nitrogen cycle by synthesis of chemical fertilizers as well as by air pollution has already reached a magnitude comparable to that of the natural biogeochemical cycle. Water pollution due to nitrates and ecological impacts of acidification and eutrophication of water bodies have occurred in various places. Also, movements of matter beyond national boundaries have been discerned. The modification of nitrogen cycle is deemed to have exceeded the limit of sustainability.
Nitrogen fertilizer is indispensable for food production. We should develop and disseminate such technologies that fulfill the needs for food production as well as those for reduction of environmental burden due to nitrogen together, including those in agriculture and livestock business, in treatment of waste water and solid waste, and in monitoring and control of the nitrogen cycle in various scales.
East Asia, which includes Japan as well, has a large population, and accordingly its environmental burden of nitrogen is large. It is ever more increasing particularly in such emerging economies as China and Southeast Asia, because of their rapid industrial development and changes in food choices, although environmental regulation is also being strengthened. It is crucial to act proactively to reduce environmental burden before any large-scale damage appears evident.
To do this, both national and international policy measures are needed. In order to provide scientific knowledge to them, we need to develop capability to simulate the nitrogen cycle over the East Asia as well as the effects of technological options on it. Also, each district in the East Asia should have a continuous monitoring system of the nitrogen cycle, and dispatch warning if significant increase in any part of local environmental load of nitrogen is detected, so that people can apply measures to reduce the environmental burden. In order to achieve this, we should promote R&D on cost-effective monitoring and abatement technologies.
International scientific programs that deal with global environmental issues under the auspices of the International Council of Science (ICSU) are being reorganized as "Future Earth". International funding schemes of R&D are also being developed. Thus, the time has come to work on solving the problem of the nitrogen cycle in the East Asia by taking advantage of the above-mentioned frameworks.
In this context, Japan, as suggested by the follow-up of the Third Basic Plan of Science and Technology, should promote R&D aiming at sustainable nitrogen cycle by overcoming administrative boundaries. We call it "Research Initiative for Sustainable Nitrogen Cycle". It principally consists of R&D projects that focus on three spatial scales: East Asia, watershed, and farm. Each of them should include a common scientific basis and a scheme for integration of entire research outcomes.
(1) East Asia. Integrated process-based models of the nitrogen cycle applicable to East Asia are to be developed. Making use of them, the complete nitrogen balance is evaluated. Spatio-temporal data of the nitrogen cycle as well as of the natural and social factors causing possible changes to it, both at present and in the past, will be collected and organized. Model experiments to represent the actual states will be carried out. Also, sensitivity studies will be done in order to clarify effects of technologies and policies. The models are also applied to multiple future scenarios in order to evaluate technological options.
(2) Watershed. A river catchment, which has a length scale of tens of kilometers, and which is heavily affected by human activities, is to be studied as a system of biogeochemical cycle. Focusing on the nitrogen cycle as well as the factors that can change them, enhanced observations and surveys will be made, and a consistent data set of the nitrogen balance would be available. Also, field experiments should be made in the watershed with implementation of enhanced measurements, in order to evaluate impacts of technological options.
(3) Farm. Intensive studies will be made in an experimental farm of a length scale of hundreds of meters, which is precisely maintained and measured. Detailed observations and modeling of basic processes of the nitrogen cycle in the soil-plant complex in the cropland will be made. Abatement technologies in agriculture will be developed and tested in experiments with detailed observations, and their intended and unintended effects will be evaluated. Also, appraisal of measurement technologies should be made in the field.
(4) Basic R&D. R&D projects that contribute to (1), (2) and (3), including those to fully understand mechanisms of nitrogen cycle and those to develop technological options, will be planned in a collaborative way.
The R&D initiative should include the following subjects and need inter-disciplinary collaboration.
Observational and experimental studies to understand processes and mechanisms of nitrogen cycle.
Understanding of processes (biological, soil, hydrological, geochemical etc.) that comprise the nitrogen cycle.
Understanding of the overall nitrogen cycle and its degree of modification.
Development of measurement technologies. They will facilitate observational studies and will also be incorporated in the abatement technologies.
Development of simulation technologies.
Model development, calibration and validation based on the data of nitrogen cycle in the past.
Evaluation of intended and unintended effects of abatement technologies by prognostic experiments with scenarios of technological options.
Development of abatement technologies, and experiments to assess them. These experiments involve comprehensive observations, which will comprise feedbacks to improvements of the technologies.
Agricultural technologies: breeding of such crop varieties that can utilize nitrogen fertilizer effectively; development of fertilizer products; techniques of applying fertilizer, controlling water, and tillage.
Technologies to recycle (as fertilizer) or treat (denitrify) animal manures and human wastes.
Social technologies to make incentives for reduction of nitrogen burden, such as tax reforms.
Implementation of this R&D initiative needs collaboration cutting across administrative boundaries. Also, for its success, it is mandatory to cultivate a research community, which shares the recognition of the existing issue of sustainable nitrogen cycle and moves forward beyond disciplinary boundaries. The community should include, besides researchers in the conventional sense, those who are willing to participate in demonstration experiments both in Japan and in foreign countries.
With this R&D initiative promoted, it will be possible to comprehend nitrogen cycle and also to plan and to implement policy/technology measures to reduce its environmental burden, at such multiple scales as farms, watersheds, and East Asia. Also, from the viewpoint of science-technology diplomacy, it is necessary to work ceaselessly to form science-based advice to international policy-making, partly by way of international assessments on nitrogen cycle. The knowledge gained in this R&D initiative, particularly, observational data, standard models, results of simulations, indices for evaluation, should be publicized, shared internationally, and be maintained for the years ahead. That can be Japan's leading international contribution.