予想される気候の揺らぎのもとでの日本・韓国地域の水稲生産量変動の予測

Abstract

Agricultural activities and crop production will be affected if and when climate deviates from the normal. In the eastern part of Asia, i.e. the region including Japan and Korea, effects of climate variations on the yield of paddy rice were demonstrated dramatically by a climatic regime known as a Blocking High. In 1993 the Tohoku district of Japan and Korea were affected by a severely low temperature anomaly ranging from -2.8°C to -3.7°C in monthly averages. This caused reductions of rice yield of -45% and -9% in the Tohoku district and Korea respectively. The spatial distribution of the yield anomaly indicated that a cold current derived from the Okhotsk High simultaneously attacked the east part of both countries. This event showed that a similar depression in rice production should appear in both countries when cool summers occur. Fortunately, these negative anomalies were balanced by high production in the hot summer of 1994.To project the influence of the temperature anomaly on the production of paddy rice, correlation analyses were carried out. A curve, ΔY=-0.89×exp (-0.34×ΔT)+1, was obtained with r=0.698. Here, ΔY is the anomaly of rice yield, ΔT is that of averaged temperature through July to September. Using this relationship, changes of rice production were projected against temperature anomaly and ranged from +13% with ΔT=+3°C to -39% with ΔT=-3°C.Variations of paddy rice production, over the regions of Tohoku district and Kore, coincided with a penetration of cold-NE-current into their eastern zones along the coast. This event will trigger a food problem in East Asia under possible fluctuations of summer temperature. In addition, arable lands have been devastated and population will grow up to 1.5 times the present population by the middle of the next century. Evaluation of the vulnerability of agriculture in East Asia, where paddy rice is a main crop, will be an important subject for scientists and for policy makers.