Katsuo Okamoto

A model-based estimation of nitrogen flow in the food production-supply system and its environmental effects in East Asia

Abstract We created a numerical model to evaluate the anthropogenic nitrogen load on the environment and the nitrogen concentration in river water on a 0.5° × 0.5° scale. We estimated the nitrogen load of each country in East Asia from FAO statistics on fertilizer consumption, food balance sheet data, and grid data of NOx emissions due to fossil fuel combustion. For China, province statistic data were also adopted. Nitrogen loads of each country were distributed among grid cells on the basis of farmland and population distributions. The concentration in river water and riverine export of nitrogen were calculated by assuming a first-order reaction model in which denitrification and organic matter accumulation was a function of temperature and resident time. More than 90% of the nitrogen load originated from food production and supply. The contribution of NOx emissions was important only in Japan and South Korea. The estimated loads of nitrogen on the catchments of the major rivers were 10–30 times larger than the measured riverine export of nitrate in the literature. Estimated nitrogen concentrations in river water that also agreed well with measurements, showed that rivers close to the east coast of Northern and Central China were highly polluted with nitrogen.

Nitrogen flow associated with food production and consumption and its effect on water quality in Japan from 1961 to 2005

Abstract Using statistical data, we evaluated food supply and consumption in terms of nitrogen flow to clarify its effects on water quality from 1961 to 2005 in Japan. We revised a nitrogen flow model to incorporate food production, trade and consumption as well as nitrogen mineralization of crop residues and livestock manure and denitrification. Food consumption increased steadily from 1961 to the mid 1980s and has been almost stable since then. There was a notable increase in the consumption of livestock products. By 1996, consumption had risen to fivefold the 1961 level of consumption, but it has been stable since then. We concluded that the demand for food reached a maximum in the 1990s. The increasing demand for animal feed was filled by an increase in the imports of coarse cereals until the 1980s and of oil cakes until now. As the consumption of food and animal feed increased until the mid 1980s, the nitrogen load to the environment also gradually increased during this period, after which it tended to decrease. We estimated the nitrogen concentration in river water for 8 km × 8 km grid cells from 1961 to 2005 and compared these estimated values with measurements taken at more than 4000 points from public bodies of water in 1998. The spatial distribution and prefectural average of the estimated nitrogen concentration roughly corresponded with the measured values, and both indicate that food supply and consumption have had considerable effects on water quality in Japan.

Estimating total area of paddy fields in Heilongjiang, China, around 2000 using Landsat Thematic Mapper/Enhanced Thematic Mapper Plus data

ABSTRACT Agricultural statistics are a fundamental reference for evaluating damage caused by natural disasters, estimating food supply and demand, and framing policies. A statistical table is usually prepared by an administrative district. Unfortunately, the Heilongjiang Statistical Yearbook of China was not completely prepared by such a district. Therefore, remote sensing technology is necessary for estimating the total area of agricultural lands in each administrative district. The test area is the Heilongjiang Province in China. The Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) data acquired during and immediately after the rice-planting season around 2000 (1999–2002) were used for the land-use/land-cover classification. All possible data during or immediately after the rice-planting season (from the beginning of June to the beginning of July) were selected so that paddy fields could be detected accurately. Borders of prefecture-level cities were generated using borders of cities and prefectures derived from the Digital Map Database of China 1:1,000,000 International Version. The TM/ETM+ data with bands 3, 4 and 5 (red, near infrared and middle infrared, respectively) were prepared for the land-use/land-cover classification. These data were classified by the unsupervised method Iterative Self-Organizing Data Analysis Technique. Land-cover classes were identified and reclassified into 12 classes, i.e., submerged paddy fields, overgrown paddy fields, bare dry cropland, overgrown dry cropland, bare ground, grassland, woodland, wetland, water, built-up, shade and shadow, and clouds. Some scenes including clearly misclassified paddy fields were image-processed or reclassified to reduce misclassification. The accuracy of detecting paddy fields was estimated to be in the range of 86.2–94.6%. The area of paddy fields in Heilongjiang Province was estimated to be 19.4 × 103 km2 and overestimated by 17.7% for the Heilongjiang Statistical Yearbook.

Pluses and minuses of climate change on major cereal cultivation in Asia

This paper describes the impacts of climate change on major cereal crops, i.e., rice, wheat and maize, in Asia using results from simulation studies using the CCSR (Center for Climate System Research, the University of Tokyo) GCM (Global Climate Model). Climate change could cause the air temperature and precipitation to become unsuitable for major cereal cultivation in Asia. To predict the impacts of climate change on sustainable cropping and agricultural development, we evaluated changes in climatic conditions in Asia in major cereal cropping seasons. We used the monthly average temperature and precipitation data from the 1961-90 mean climatology and CCSR GCM. We analyzed changes in the mean temperature and precipitation of major cereal-producing regions at different cropping seasons from the present through the 2090s. Climate change will generally increase both the air temperature and precipitation in Asia. The impacts of climate change have two sides: plus and minus. The increase in the air temperature and precipitation will be disadvantageous to wheat cropping in Asia. In contrast, some regions in subtropical Asia will have excess water resources during the rainy season. Precautionary measures against flooding will be needed in these areas.

Sustainable Rice Cropping And Water Resources In Asia

One-half of the population in the world lives in Asia. The population of Asia is predicted to grow in the first half of the 21st century. An increase in unit yield and expansion of irrigated fields are solutions to feed the growing population of Asia. At present, it is suggested that agricultural activities sustain an ecosystem. Is such sustainable development possible? Here focused on major river basins with rice-cropping zones from East to South Asia. The amount of available water for cultivating rice and the potential irrigation land area under the present climatic conditions were estimated. Then possible changes in water quality in the future were discussed. The data include those on the course of a river, land-uselland-cover classification, population, climate, nitrous oxide (NOX) emission, and country boundary. Statistical data on rice yield, harvested area, fertilizer consumption, food production, food consumption and food trade were also used. The present water resources almost balance the water demand for the present rice cultivation. The water resources are seasonally in excess. To increase rice production, it is necessary to extend a paddy field or an irrigated area in the dry season. Nitrogen load maps were constructed. The nitrogen load changes seasonally depending on the cropping systems used and precipitation. Denitrification is similar to the nitrogen load and the water quality which is satisfactory at present. In the future, the nitrogen concentration in river water will increase probably because nitrogen discharge from humans and fertilization will increase according to an increase in the population and cultivation intensity, and because fertilization and deposition of NOX will increase according to economic growth. Excessive irrigation and fertilization in the dry season will aggravate the water quality. They will result in a nonsustainable ecosystem in river basins. Transactions on Ecology and the Environment vol 64,

Evaluation of change in rice cropping in the marginal zone

We detected a change in the area of rice-planted fields using multitemporal satellite images, and investigated the cause from a geographical point of view. Rice is the staple food of Asian people. Rice is cultivated in warm places. In marginal zones, external causes, such as socioeconomic and natural causes strongly affect the decision of a farmer to cultivate rice or not. We selected the northern part of Japan as a test site. The air temperature of this site in a rice-growing season is at the lower limit for rice cropping in a normal year. We first classified the Landsat TM data acquired on 22 May 1999 and estimated the area of rice-planted fields. Then, we determined rice-planted fields using the RADARSAT SAR data acquired on 22 May and 11 June 2001, and detected a change in the area of rice-planted fields between 1999 and 2001. The result shows that the decrease in the area of rice-planted fields in the coastal zone is greater than that in the inland zone. According to climatic data, the air temperature in the coastal zone is lower than that in the inland zone. The lower temperature in the coastal zone is disadvantageous to rice cropping.

Role Of Satellite Remote Sensing In Monitoring System For Environmental Disasters Related To Water Resources

Remote sensing technologies have enabled rapid collection of data on environmental disasters where contemporaneous field observations are unavailable or incomplete. We focus on satellite-remote-sensing-based approaches to monitor environmental disasters caused by surplus or deficient water resources, and outline methods to detect events and evaluate the damage caused by them. These disasters include flood and drought. Flood can be detected easily from the remote sensing image based on the salient characteristics of spectral reflectance or the backscattering coefficient. The occurrence of a drought can be predicted from a combination of some indices based on the satellite remote sensing data and meteorological data, However, many problems remain as to how to effectively predict a disaster and avert its damage before the disaster actually occurs, using a combination of remote sensing techniques, geographical information system (GIS) and administrative frames.

Evaluation of changes in climatic indices using combined analysis of remote sensing and GIS

We predicted the future conditions of places in which major cereals are cultivated using satellite remote sensing data in combination with spatial analysis as provided by geographical information systems (GIS). The open policy and economic reform have significantly accelerated economic growth of mainly in the coastal regions of China. Economic growth in China will change the diet and will increase cereal demand. As a case study, we predicted the trend of major cereal production in China in the 21st century. We also predicted the agricultural productivity of existing fields cropped with major cereals based on climatic indices, i.e., the net primary productivity (NPP) and the balance between precipitation and potential evapotranspiration (P-PET), from the present to 2090s. The agricultural productivity in central, northern and northeastern China will increase as a result of an increase in the NPP, while that in southern China will not. The agricultural productivity in western China will decline as a result of a decrease in P-PET. Desertification will be a problem in these regions. The result of this study suggests that combined analysis of satellite remote sensing and GIS data is effective for use in a comparative study of the present and the future conditions.