Japan Geoscience Union Meeting 2015

Presentation information


Symbol A (Atmospheric and Hydrospheric Sciences) » A-HW Hydrology & Water Environment

[A-HW27] Water and material transport and cycle in watersheds: from headwater to coastal area

Sun. May 24, 2015 11:00 AM - 12:45 PM 301B (3F)

Convener:*Shinji Nakaya(Department of Civil Engineering, Faculty of Engineering, Shinshu University), Mitsuyo Saito(Graduate School of Environmental and Life Science, Okayama University), Shin-ichi Onodera(Graduate School of Integrated and Arts Sciences, Hiroshima University), Kazuhisa Chikita(Department of Natural History Sciences, Faculty of Science, Hokkaido University), Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Masahiro Kobayashi(Forestry and Forest Products Research Institute), Seiko Yoshikawa(Narional Institute for Agro-Environmental Sciences), Noboru Okuda(Research Institute for Humanity and Nature), Chair:Noboru Okuda(Research Institute for Humanity and Nature)

11:15 AM - 11:30 AM

[AHW27-09] Nitrogen issues induced by human activities: A big issue in Earth system beyond watersheds

*Kentaro HAYASHI1, Sadao EGUCHI1, Kei ASADA1, Seiko YOSHIKAWA1, Kaoru ABE1 (1.National Institute for Agro-Environmental Sciences)

Keywords:Nitrogen, Water quality, Air quality, Eutrophication, Global environment, International Nitrogen Management System

Nitrogen (N) is indispensable for agriculture. Crop production has increased drastically since the Harber?Bosch process which provides chemical N fertilizers. Nitrogen fertilizers support the global population and increase meat production in many countries. Nowadays, approximately a half of the global population depend on the Harber?Bosch process. In contrast, it is estimated that crops uptake only approximately 25% of applied N to croplands as a global average (approximately 40% in Japan). Although a part of the remaining N can be stored in soils as organic matter, most of which turns into environmental N loads to soil, water, and air. Livestock waste also results in N loads to the environment. Nitrogen in the environment changes its chemical forms in its cycling (so-called nitrogen cascade). We see various environmental consequences due to the human-induced N loads, e.g., water pollution, air pollution, effects on global radiative forcing, stratospheric ozone depletion, eutrophication, and acidification. We collectively call it N issues.
A typical N issue in Japan is water pollution of groundwater, lake water, and enclosed coastal water due to excess N fertilizers in croplands, livestock farming, and miscellaneous drainage. However, N in water bodies is also connected to other environmental media through the N cascade. For example, atmospheric N deposition inputs N to watersheds. Nitrous oxide produced by nitrification and denitrification in soils, sediments, and water bodies is a potent greenhouse gas and simultaneously a strong ozone depleting substance when emitted to the atmosphere. Japan is a small and densely populated country, and highly depends on imports for food and feed (self-sufficiency ratios: food, 39%; feed, 26%). Recently in Japan, a huge amount of food is discarded without being consumed. Such the food waste is estimated to 5?8 Tg yr?1, which is larger than the food for aid in the world (4 Tg yr?1). A large proportion of N is eventually loaded to the environment without being recycled. Japan is one of the world's biggest countries in terms of N loads per unit area of land.
Maximizing N use efficiency and minimizing environmental N loads are dilemma important for the sustainability of food production, energy consumption, and Earth system. Therefore, N issues are receiving increasing attention in the world. The International Nitrogen Initiative (INI) organizes Nitrogen Conferences every three years and implements N assessments for major regions in the world. OECD is developing indicators to assess N issues in collaboration with INI. UNEP and INI are preparing an international project of the Global Environmental Facility, the International Nitrogen Management System to establish a system connecting science and policy to address N issues. The Future Earth starting in full from 2015, a huge international project involving all stake holders, situates the sustainable food production as a major theme, in which resolution of the N dilemma is an important research component.
Relevant efforts of Japan seem delayed in comparison with the world situation. A variety of respective studies of water quality, air quality, and global environmental issues have been progressed, whereas efforts to comprehensively understand the N dynamics in the N cascade and to share and discuss study results with other sectors like policy makers are still insufficient. We will present the current situation of N issues in Japan and the world efforts against N issues. And then, we aim to suggest the establishment of Japanese Nitrogen Expert Group to tackle with N issues. It is supposed that the N expert group will consist of several subgroups (e.g., agriculture, freshwater, marine, atmosphere, land, and industry) because of a variety of sectors involved in the N issues. We hope that relevant experts are interested in and join in the group.