Geographical Review of Japan Vol. 66 (Ser. B), No. 1, 70-88,1993

Climatic Change and Rice Yield and Production in Japan during the Last 100 Years

Masatoshi YOSHINO*

Abstract

First, general trends of rice yield and production and changes of air temperature , precipita tion and sunshine hours in Japan during the last 100 years are described. In yield , three periods can generally be recognized: Period 1, from the end of the 19th century to about 1915 , Period 2, from about 1915 to about 1945, the end or just few years after the 2nd World War , and Period 3, after the end of the 2nd World War. Secondly, fluctuation of climatic conditions and its effects on the paddy rice yield during the last 104 years were studied statistically in order to evaluate the different impacts according to period . By applying the principal component analysis method, their distributions, periodicities and relations to monthly mean air tempera ture, monthly total precipitation, and monthly total sunshine hours were studied . The first component has a significant correlation to all three climatic elements in July , and air tempera ture and sunshine hours in August and precipitation and sunshine hours in September . In the second part of this study, we classify the 104 years into three periods according to interannual changes of paddy rice yield. For these three periods , the general trends and fluctuations are described and the relationship between the yield and climatic elements are analyzed for five regions respectively.

Key words: Climate change, Climate fluctuation, Climatic impact , Agroclimate, Paddy rice yield.

tamed much data related to the present theme . I. INTRODUCTION Along with an international project on an as sessment of climatic impact on agricultural pro Climate changes and fluctuates over various duction in the case of global warming in the 21 time scales. In order to analyze the relationship st century, Japanese cases have been studied between climatic change/fluctuation and agri (YOSHINOet al., 1987). On the other hand, gener cultural yield/production during the last 100 al trends and fluctuations of the rice yield in years, the present paper first describes the gen Japan in the last 100 years have been analyzed eral trend of Japanese agriculture and second by UCHIJIMA,Z. (1981). the climatic conditions, particularly change/ Besides those written in English, numerous fluctuation, cycles, and abnormal weather oc comprehensive studies have been published in currences in Japan. In the next part of the Japanese. Due to considerations of space, the study, the impact of such climatic conditions on history of research on the present theme has paddy rice production are dealt with. not been discussed here, but its beginnings Just 20 years ago, research status and prob were as early as the last decades of the 19th lems in agricultural climatology (YosHINo, century. In the 1930's and 1940's, there already 1974), crop-weather relationship (HANYU, 1974) existed many books and monographs as well as and meteorological hazards (UEMURA et al., articles on this subject. Among others, the most 1974) in Japan were summarized. An interna comprehensive studies were made by DAIGO tional symposium on "Climatic change and food (1943, 1944, 1945). production" was held in Tsukuba in 1977 and Based on the review of previous studies, we its proceedings (TAKAHASHIet al., 1978) con now turn to the analysis of regional differences

* Aichi University , Toyohashi 441, Japan Climatic Change and Rice Yield in Japan 71 in tendencies for long year series. In order to paddy rice cultivation had already spread up to contribute to these problems, an attempt was the southwestern part of Hokkaido, north made to analyze them by division into three Japan, in the Yayoi period, 2,500 years B. P. stages of development of rice cultivation. However, the irrigation system including drain age and flood control ("Water-control stage") II. GENERAL TRENDS OF PADDY RICE had been established in about AD 645 as shown YIELD IN THE LAST 100 YEARS in Fig. 1 (TAKASEet al., 1969). From the end of the last century, Japanese agriculture entered Modern archeology has made it clear that the "Inputs stage", by actively introducing fer

Fig. 1. Historical development of irrigation and rice production in Japan compared with other rice-cultivat ing countries (TAKASEand KANo,1969). Lines in the lowerpart show the year-by-yearchanges of paddy yield in Japan (LineA) and in other countries,Australia, china and Thailand. II, III and IV indicatethe "Water-controlstage", "Inputs stage", and "cultivation-methodstage" in the respectivecountries. The upper part of figure,Line B shows the changeof farm land in Japanand Line Cnumber of irrigationdams in Japan. 72 M. YOSHINO

Fig. 2. Geographical distribution of rice yield by country in relation to latitude (TAKASEand KANO,1969). ADB:Asian DeveiopmentBank.

tilizer, new varieties, pesticides etc., and from shown in Table 1 (YAMADAet al., 1969). The 1950, it entered the "Cultivation-method stage". total yield in this country was about one third Rice yield in Japan is among the highest in that of India. the world. In Fig. 2, rice yield is shown in ac The trends in rice and other field crops pro cordance with latitudes (TAKASE et al., 1969). duction during the last 100 years show contin Rice yield is scattered widely in relatively uous increase in general, but with drastic higher latitudes, 31•‹ or more, but the average change in sericulture and livestock production values are increasing strikingly from 11-20•‹ to as shown in Fig. 3 (HAYAMI,1975). The total 31•‹ or more. Among the highest group, Japan is production, output and gross value added in the third or fourth counted from Spain as the agriculture have also increased continuously as top. The paddy production of Japan ranked shown in Fig. 4 (HAYAMI,1975), even though second or third in Asia about 30 years ago as the effect of the 2nd World War is striking. Climatic Change and Rice Yield in Japan 73

Table 1. Paddy Production in Asiaa (YAMADAet al., 1969)

a) All statistics were provided by the respective governments, except those marked with an asterisk, which were taken from FAO Document No. CCP: RI 67/7.

Table 2 shows the distribution of farms by size of cultivated land area, from 1908 to 1990. As is clearly shown, small scale family farms are predominant, which is still true in the 1980's (KAT5UKI,1993). That is to say, the struc ture of rural organization has been fairly con sistent during the years of the statistics. HAYAMI (1975) mentioned that, because of the heavy burden of taxes and rent, coupled with a lag in productivity growth in agriculture rela tive to the nonfarm sector, the level of income and consumption of farm households lagged behind urban households. This situation might be reflected in the consistent technical improve ments in agriculture in Japan, but the farm sizes remained in a similar percentage distribu Fig. 3. Trends in agricultural production by com tion. Because the small size farms are generally modities. considered to be more sensitive, due to the Adjusted to 1934-1936constant pricesshown by 5-year economically weak background of farmers, to averages(HAYAMI,1975). such unfavorable conditions as anomalous weather, these farm size characteristics should wider year-to-year fluctuation over recent be taken into consideration. Increase of part years. This is because production has already time farmers during recent years should also be reached the higher stages and the area of fields considered quantitatively, but related problems and yield cannot be drastically increased. In need to be considered in further studies. contradistinction to this, the United States and YOKOYAMA(1990) described Japanese rice Australia put large machinery into rice cultiva production as similar to that of European coun tion and produced for export at lower cost, tries, with a slowly increasing tendency to particularly since the 1970's. For example, the 74 M. YOSHINO

Fig. 4. Trends in total production, total output, and gross value added in agriculture. Adjusted to 1934-1936 constant prices shown by 5-year-averages (HAYAMI,1975).

Table 2. Distribution of Farms by Size of Cultivated Land Area

a) Percentage distribution is shown in parentheses. Source: Institute of Developing Economies, One Hundred Years of Agricultural Statistics in Japan (Tokyo, 1969), p. 116; and Ministry of Agriculture, Forestry and Fishery, Statistical Research Division: World census of Agriculture Report on Farmhouseholds and Population, and Agriculture census and Agricultural Investigation. Data from 1908 to 1970 is also available from YAMADAet al. (1969).

percentage of total farmers in the U. S.A. accord ing to harvested area for below 40ha is 27.5%, III. CLIMATIC CHANGE, FLUCTUATION for 40-100ha 33.9%, for 100-200ha 24.2%, for AND ABNORMAL WEATHER DURING 200-400ha 10.9%, and above 400 ha 3.5%. THE LAST 100 YEARS These figures are quite different from the values shown in Table 2. It is particularly strik Annual mean air temperature increased 0.4 ing that farms smaller than 1ha are still domi 0.5•Ž/100 years as the average for the whole nant, 67-68%, in Japan (JINNOUCHI,1992). country as shown in Fig. 5. If we look at it regionally, the trends vary. The maximum Climatic Change and Rice Yield in Japan 75

Fig. 5. Year-by-year changes of air temperature, precipitation and sunshine hours in Japan 1900-1980, annual mean or total. (Data sources: Japan Met. Agency, 1984). around 1960 is striking in the respective parts Islands, however, show a remarkable increase of Japan, though the trends in the 1970's are not with certain periodicity of about 24-25 years. the same. Precipitation shows very complicated fluctu Precipitation shows more complicated fea ations. The only thing which can be said is that tures. There were two maximums around the the fluctuation range is wider in the south than 1920's and 1950-55, but, generally speaking, the north. Fluctuation of precipitation is clear the curves show decreasing tendencies. Fluctu ly reflected in the fluctuation of sunshine hours. ations are larger in South Japan and smaller in The maximum period appeared in the 1940's. North Japan. Detailed figures are omitted due to In winter, an air temperature rise is more space, but anomalously drier months occurred evident in North and East Japan than in West 2times more than anomalously wetter months Japan and the Nansei Island, though the de in the 1970' s. This tendency has continued creasing tendency of precipitation is clearer in during recent years. The cycle of heavy rainfall the south than in the north as shown in Fig. 7. occurrence coincides with the 35 years, so Sunshine hours show opposite fluctuations to called "Bruckner Cycles". precipitation similar to summer. Sunshine hours are relatively simple as com pared with air temperature and precipitation, IV. IMPACTS OF CLIMATIC CHANGE, though the maximums around 1940 and during CLIMATIC FLUCTUATION AND the 1940's are striking. Over the last 30years, ABNORMAL WEATHER the fluctuations of sunshine hours are clearly opposite to those of precipitation in the respec 1. General View tive parts of Japan. In summer, which is the important season for Paddy rice yields since the year 1883 have agriculture, increasing tendencies of air temper been organized by IWAKIRI(1982) as shown in ature are not clear for the whole of Japan as Fig. 8. He classified year-by-year changes of shown in Fig. 6. Since the 1920's, it seems that yield into three periods: Period 1 is from the they have been fluctuating at the same level or early Meiji era to 1920 with a slow but steady increasing at quite a slow rate. The Nansei increasing tendency, Period 2 from 1921 to 76 M. YOSHINO

Fig. 6. Same as Fig. 5, but for summer in July.

Fig. 7. Same as Fig. 5, but for winter in January.

1954 with almost the same level of yield, and age, indicating striking negative yield devia Period 3 after 1955 with a sharp increase. Sim tions. Cool summer damage occurred 23times ilar, but slightly different division of the rice during 97years, which is roughly once in four yield in Japan was given: Period 1 from 1880 to years. Regionally speaking, North Japan suffers 1910, Period 2 from 1910 to 1950, and Period 3 more from cool summer damage: fluctuation after 1950 (Soc. Agr. Met. Japan, 1992). In Fig. 8, index of the yield index is about 30% in Hokkai the dot denotes the year of cool summer dam do, North Japan, the Tohoku District is about Climatic Change and Rice Yield in Japan 77

14%, the Kanto District is 11%, and the Kyushu District, South Japan, is 10%. Here, fluctuation index is expressed by Y'/Y•~100%, and Y' and Y are described in an equation (1). It is interest ing to note, however, that the critical tempera ture is different from region to region. In Hok kaido, cool summer damage occurs at 20•Ž of the average monthly mean air temperature of

July and August, but in the northern part of Honshu, it is 21•Ž. Year-by-year change of soy bean yield during the last 100 years is shown in Fig. 9 (IWAKIRI, 1982). It shows also three periods: Period 1 showing a steady increase from 1880 to 1920, Period 2 showing a decreasing tendency from 1921 to 1945, and Period 3 showing an increas ing tendency after 1946. However, it should be Fig. 8. Year-by-year change of paddy rice yields in noted that, even in Period 3, cool summer Japan since 1883 and cool summer damage (IWAKIRI,1982). damage was very serious. CRAWCOUR (1969) pointed out that the struc ture of Japanese agriculture changed during the period 1910-1915. For example, the average annual growth rate of primary industry became low in contrast to the fact that the rate of growth of farm value (gross agricultural pro duction) became higher. Agricultural exports decreased in 1916-1920. Therefore, Japanese agricultural development can be divided before and after these years. An example of the effect of cool, wet summer of 1980 is presented in Table 3. The Bai-u fron tal zone, a part of the Pacific Polar Frontal Zone, located along the southern coast of Honshu, from mid June to mid July, is active in most cases in cool summers. In 1978, an anomalous Fig. 9. Year-by-year change of soy bean yield in drought year, the frontal zone was inactive, and Japan since 1883 and in U. S. A, since 1930 in 1980, a normal year, it developed at the (IWAKIRI,1982).

Table 3. Comparison of paddy yields in Japan in the years between active and in-active Bai-u front

* "Active" means that the Bai-u frontal zone locates in normal position appearing in the normal period. ** "In-active" means that the Bai-u frontal zone was observed anomalously both in position and time. The less cloudy weather implies hot and dry conditions. 78 M. YOSHINO

Table 4. Variance and cumulative variance of the the yield index IY is first five components IY=-0.04961Į2+2.186Į-22.8882, (5)

where Į is monthly mean air temperature in

July and August in Hokkaido. If we consider that the low temperature corresponded to return period 5 years, (it is 19.4•Ž), IY is 0.85, which implies 8.96t/ha.

2. Component Analysis of Rice Yield in normal position. The damage to agricultural Japan during the Last 100 Years production was quite different. North of the The data used were obtained from the Nosho frontal zone, air temperature is lower than mu Tokeihyo (Agriculture-Commerce, Statisti normal, paddy rice yield is reduced, and dam cal Book) from 1883 to 1924, from the Norinsho aged area and quantity noticeably increases. Tokeihyo (Ministry of Agriculture and Forestry

UCHIJIMA,Z. (1981) studied the variability of Statistical Book) from 1925 to 1976 and from crop yield by expressing the Norinsuisansho Tokeihyo (Ministry of Agri Y=YT+Y', (1) culture, Forestry and Fishery Statistical Book) from 1977 to 1986. where Y is the observed actual crop yield (t/ha), From these books, yield of paddy rice (non

YT is the non-linear trend of crop yield (t/ha), glutinous rice and glutinous rice) was obtained and Y' is the deviation of crop yield from the for the 46 prefectures except Okinawa. First, non-linear trend (t/ha). In his study, the whole the unit was adjusted to kg/ha and calculated series of the period from the 1880's to the anomalies from the eleven year running means 1970's were not divided by sub-periods. He also for each prefecture for each year. calculated yield index, IY, as Using the anomalies as calculated by the method mentioned above, the Principal Compo IY= Y/YT (2) nent Analysis, PCA, was applied for the 46•~ 104 data matrix (KOGA, 1989). The results ob and further coefficient of variance, CVIY, for the tained are given in Table 4. It is noteworthy time series of the yield index by that the 1st component explains more than 50% of the total variance and the cumulative CVIY=QIV/IY•~100(%), (3) variance from the 1st to 3rd components ex

plain 70% of the total variance. In Figs. 10 to where IY is the mean of time series of the yield 12, the spatial eigenvector patterns of the 1st to index and a is the standard deviation of time 3rd principal components are given respective series of the yield index. CVIY was 9% for rice, ly. 12% for barley, 14% for wheat, maize or millet Roughly speaking, the 1st principal compo and 16% for rye. The reason that the coefficient nents are high in the middle parts of the Japa of variance of paddy rice is the smallest in nese Islands; in other words, relatively lower in Japan can be attributed to the developed irriga the southwestern part of Japan and in Hok tion systems, which soften the adverse effects kaido, North Japan. The distribution of the 2nd of unfavorable weather conditions. principal component shows a clear difference UCHIJIMA,T. (1987) revealed the trend of rice between Southwest and North Japan. This yield in Japan over the last 100 years by the means that the tendencies between Southwest following equation: and North Japan are opposite. The distribution of the 3rd principal component also shows an Y=0.00000162X4+0.000718X2-0.06389X2 interesting pattern: the southwestern and +2.200X+155.5, (4) northern parts are the same, but not Central where X is the number of year from 1883. Then, Japan, even though its contribution rate is only Climatic Change and Rice Yield in Japan 79

Fig. 10. Distribution of eigenvector for the 1st com Fig. 12. Same as Fig. 10, but for the 3rd compo ponent (YOSHINOand KOGA,1990). nent (YOSHINOand KOGA,1990).

Fig. 13. Year-by-year changes of score of the 1st, 2nd and 3rd components (KOGA,1989).

Fig. 11. Same as Fig. 10, but for the 2nd compo distribution of the principal components and nent (YOSHINOand KOGA,1990). climatic elements is studied (YOSHINOand KOGA, 1990). 7.7%. Year-by-year changes of the score of the In order to calculate the correlation between 1st, 2nd and 3rd components are shown in Fig. the distributions of the 1st to 3rd components 13. and climatic elements, monthly mean air tem In the next step, the relationship between the perature, monthly total precipitation and 80 M. YOSHINO

Fig. 14. Distribution of meteorological stations used in this study.

"little dry season in summer" in Japan monthly total sunshine hour data at the 47 . In other stations, shown in Fig. 14, were collected for words, precipitation in the last stage of the 1900-1984. Anomalies from the 11-year run Bai-u season, an early summer rainy season, in ning mean for every year were calculated in the July and in the typhoon and shurin season (au same way as the statistical analysis of paddy tumnal rainy season) in September are more rice yield. effective for rice yields. It is reasonable that The results indicate that the 1st component sunshine hours have a significant correlation in has significant correlation coefficients to air all three months, because they have generally a temperature in July and August, precipitation close relation to the number of fine days, the in July and September, and sunshine hours for amount of cloud cover, the amount of solar all three months. Some examples of distribu radiation and heat available for rice not only in tions are shown in Figs. 15, 16 and 17. the main growing season but also in the har This might be attributable to the fact that air vesting season. temperature plays an important role in the Results of spectral analysis for the 1st, 2nd main growing season, which is July and and 3rd component scores are shown in Figs. August. The reason why precipitation is impor 18, 19 and 20. The prevailing periods (year) for tant in July and September is thought to be the 1st component are 6.3, 4.1 and 3.2, for the reflected by the fact that August is the so-called 2nd component, 8.3, 5.7 and 2.9; and for the 3rd Climatic Change and Rice Yield in Japan 81

Fig. 15. Distribution of correlation coefficient be Fig. 17. Distribution of correlation coefficient be tween the first component score and sun tween the first component score and sun shine hours in July (KOGA,1989). shine hours in September (KOGA, 1989).

Fig. 18. Power spectral density of the first compo nent score (KOGA, 1989).

component, 7.7 and 3.7, respectively. Summariz Fig. 16. Distribution of correlation coefficient be ing these figures, it is important to note that the tween the first component score and pre prevailing periods are roughly eight, six, four cipitation in September (KOGA,1989). and three years. Among them, about six, four 82 M, YOSHINO

Fig. 19. Same as Fig. 18, but the second component score (KOGA, 1989). Fig. 21. The division of Regions I, II, III, IV and V of Japan.

by the 11-year running mean in each prefecture can be divided roughly into three periods ac cording to the previous studies mentioned above: i) Period I from the end of the last centu ry to about 1915, in which a slow, but steady increase is observed, ii) Period II from about 1915 to about 1945, showing almost no increase or even a decrease, and iii) Period III after about 1945, in which the increasing tendency is re markable. Paying attention to the trend of these three periods, each prefecture is classified into five types. As a result, the five types are grouped regionally as shown in Fig. 21: Region I, Hokka ido and the northern part of the Tohoku Dis Fig. 20. Same as Fig. 18, but the third component trict; Region II, Niigata, Fukushima Prefectures score (KOGA, 1989). and the northern half of the Kanto District; Region III, Hokuriku and Nagano Prefectures; and three years are predominant in the 1st Region IV, the southern part of the Kanto Dis component, which occupies more than half for trict, the Pacific side of Central Japan, the Kinki the total variance. District and the eastern part of Southwest Japan; and Region V, Southwest Japan. Mean 3. Regional Division and Regionality trends of each Region were calculated as shown In the next part of the study, the relation in Fig. 22. Their characteristics are as follows: ships between climatic fluctuation and paddy Region I: Low yield, mostly lower than 2 rice yield in the three periods are studied region ton/ha, with relatively greater interannual vari to region in Japan. The general trends revealed ation is seen in Period I, but there was an ex Climatic Change and Rice Yield in Japan 83

Fig. 22. Year-by-year changes of paddy rice yields in Regions I to V from 1883 to 1986. Smoothed lines show 11-year running mean. traordinarily sharp increase in Period III, more trict has the largest area (623,000 ha in 1990) of than 5ton/ha after 1970. There were still ob paddy field, amounting to 75.7% of the total servable negative anomalies, poor harvests, in cultivation area. These conditions could exag Periods II and III. But it should be noted that the gerate the fluctuation caused by the anomalous variations became greater in the second half of weather. each Period. In Region I, rice cultivation has Region II: Low yield, about 2ton/ha, was also been suffering more from cool summer damage observed in Period I, but it increased gradually. because of the marginal condition for rice as a It is interesting to note that there also occurred tropical plant. The damage was particularly se greater interannual variations in the second rious in the years 1953, 1954, 1964, 1965, 1966, half of each Period respectively. This is the 1971, 1976 and 1980 in Hokkaido. In Period III, same tendency as Region I, but the ranges of the numbers of part time farmers increased in variations were smaller in Region II than in accordance with the development of industry, Region I. It is suggested that these facts may be which corresponds to the excess population in related to conditions of lower temperature and the agricultural regions. Besides, Tohoku Dis less sunshine, which should be further studied. 84 M. YOSHINO

In Region II, Hokuriku District has the second changed to urban/industrial use and the rate of largest area (291,000 ha in 1990) of paddy field. number of part time farmers has been increas This is the largest paddy field ratio (90.4%) of ing sharply. the total cultivation area among the Districts in Region V: In Period I, the yield was the lowest Japan. Such a situation emphasizes the inter in the southwestern half of Japan, that is, lower annual fluctuation of yield/production caused in Region V than in Regions III and IV. It is by the abnormal conditions of weather. interesting to note that rice originated from the Region III: The general trends differ between tropics, but this does not appear to be a key Periods. Gradual increase and the highest value factor on local examination. In Period II, the among the Regions I-V is observable in Period trend is horizontal in Region V as a whole, even I, relatively stable trend in Period II, and a sharp decreasing in some prefectures in Region V, increase but lower absolute values in Region III while in Period III, it increased. The pattern of than in Region I, particularly since 1970. Tend interannual fluctuation has no striking trend. encies of anomalies in Region III are similar to This means that the causes of the fluctuations those in Region II. are not same as those caused in Regions I, II and Region IV: The general trends were the most III. The anomalies in Region V are caused steady among the five regions. This means that mainly by anomalous rainfall during the Bai-u the absolute values were greater in Period I, but and typhoon seasons, or drought in August. not in Period III. Notably, they are the lowest For each Region, correlation coefficients be since 1970. This Region includes the big cities tween paddy rice yields and climatic elements of Tokyo, Nagoya, Osaka, and the surrounding (air temperature, precipitation and sunshine industrial regions. Analysis of the relationship hours) are calculated separately for each Period. between such tendencies and urbanization/in The results are shown in Table 5. In this case, dustrialization is still to be made, because there climatic elements are averages of mean or total is a possibility that better rice fields have been values in June, July and August, respectively,

Table 5. Correlation matrix for paddy yield and climatic factors for three Periods1) Paddy yield vs temperature (June, July and August)

Paddy yield vs sunshine hours (June, July and August)

Paddy yield vs precipitation (June, July and August)

1) Period division is slightly different from those in other parts of the present study, because of availability of homogeneous climatic data for the respective Regions. It is considered, however, that such slightly different division does not invalidate any conclusions drawn. * Significance level: 0.1 ** Significance level: 0.05*** Significance level: 0.01**** Significance level: 0.001 Climatic Change and Rice, Yield in Japan 85

Table 6. Fluctuation (defined by standard devia tion) of paddy rice yield in each period in Region I, North Japan

* Root-mean-square of deviation of each year from the 11-year running mean. Fig. 23. Relationship between the deviation of pad dy rice yield and air temperature in Region As clearly shown, the most significant coeffi I in Periods I, II and III (YOSHINO,1990b). cients are obtained in Region I for air tempera ture and sunshine hours and then in Region II. It is interesting to note that Region III shows negative high levels of significant correlation to precipitation. Region V has no significant rela tion to climatic conditions except for Periods I and III precipitation and Period II sunshine. As a whole, precipitation is occurring at more highly significant levels in Period III than before. As has been reported by GARNETTet al. (1992), Indian rice yields have a significant (at 1% level) positive correlation to the monsoon rainfall. Therefore, it can be generally said that rainfall is more important for rice yields in the lower latitudes, but not in the higher latitudes, where temperature and sunshine are more im portant for rice. This can be attributable to the original character of rice as a tropical plant. It is noteworthy that the larger fluctuations Fig. 24. Relationship between the deviation of pad occurred in the 2nd half rather than in the 1st dy rice yield and sunshine hours in Region half of each period (YOSHINO,1990a,b; 1991b). I in Periods I, II and III (YOSHINO,1990b). The standard deviation in each Period, as given in Table 6, becomes one order smaller in Period be related not only to the year-by-year change III than in Periods I and II. This may be attribut of climatological fluctuations, but also to tech able to the technical developments in rice culti nological developments in agriculture. The rela vation, including the introduction of new varie tionships between the deviation of paddy rice ties. These facts have been pointed out qual yields and air temperature are not linear and itatively (Soc. Agr. Met. Japan, 1992): Cool differ by Period (YOSHINO,1990b). As shown in summer damage was concentrated in the three Fig. 23, the relationships are shown by similar periods, 1900-1910, 1930-1950 and after 1970. curves, but the deviation is greater in Period I TAKAHASHI (1990) found that there are some than Periods II and III. In Fig. 24, the deviation significant differences between 40 and 50 years' is presented in relation to sunshine hours. It is lag-correlation in rice production and social slightly greater in Period III than Period II, fluctuation in Japan. Such a trend is thought to though the reason is not known at present. 86 M. YOSHINO

SWAMINATHAN,1992), the problems in studies V. CONCLUSION AND FINAL REMARKS on rice yields/production and issues are summa rized in the following eleven points from the Agriculture in Japan is characterized by standpoint of agricultural climatology. small sized farms, and the high yields are ob (1) Establishment of assessment technique tained by developed techniques such as fertiliz and sustainable land use method in circum er, suitable varieties and pesticides. Rice yield/ stances of environment fluctuation, in particu production in Japan has been suffering from lar, climatic change and fluctuation. anomalous weather during the last 100 years. (2) Basic research on climatic fluctuation in Taking into consideration the level and tenden relation to disease and insect development re cy of long year trend and fluctuation, year-by lated to crop cultivation. year changes are divided into three periods. (3) Acid rain effect on crops, vegetation, Analysis of the paddy rice yield data made clear water and soil. Emission of trace gases such as the following facts. methane from the paddy fields. (1) Based on the principal component analy (4) Long-range forecasting for establish sis method, the first component (50.7%) has a ment of cultivation calendar, field management significant correlation to monthly mean air etc. temperature in July and August, monthly rain (5) Climatic impact on hydrologic cycle and fall in July and September and sunshine hours water management systems. Possible effects of in July to September. climate change in the design and management (2) Over the 104 years analyzed, there were of water resource systems considered especially observed three periods: (i) Period I from the end for paddy rice cultivation. of last century to the years 1910-1915, (ii) (6) Direct influence of increasing CO2 on Period II from 1915 to 1945, and (iii) Period III crops. after 1945. (7) Research on land use, urban planning, (3) According to the general trends of these population growth, food supply, energy produc three periods, each prefecture was classified by tion and water resources. type of trend. They are grouped into five re (8) Adaptation of the human body, humann gions. society and agricultural activities to the chang (4) In the northern regions, Regions I and II, ing climatic environment in Japan in relation to sharp increase is striking in Period III. Relative global change. ly large fluctuations occurred in the second half (9) Collection of data and information and of each Period. This is thought to be due to monitoring of the local climatological condi technological development in cultivation coun tions introducing newly developed techniques. tering meteorological hazards between the Construction of data base on these data. former and latter stages during each Period. (10) Estimation of crop-weather relation (5) In Region IV, the increasing tendency is ships under the influence of global warming, not sharp. In Period I, the fluctuation was gener taking into consideration the human dimen ally higher than in the other Regions, but lower sions of global environmental change (HDP). in Period III. This might be related to the urban (11) Cooperation study with international ization/industrialization of this Region. programmes or projects such as the Interna (6) In the southern regions, Regions IV and tional Geosphere-Biosphere Project (IGBP). V, the year-by-year changes of fluctuations are different from those in the northern regions. Acknowledgements This might be caused mainly by rainfall or drought conditions in the southern regions, in The principal component analysis was made by Mr. contrast to the low temperature and sunshine K. KOGAand the statistical analysis in relation to climatic elements by Dr. R. Suppiah. The present hours in the northern regions. writer wishes to express his thanks to them. This Based on the results mentioned above and paper is part of the result of a project study supported other recent reviews (PARRY, 1990; PARRY and by a Grant-in-aid from the Ministry of Education, Climatic Change and Rice Yield in Japan 87

Science and Culture (No. 05203108, Leader: M. Y Crop Science 20, Elsevier, Amsterdam, 288 p. OSHINO). Society of Agricultural Meteorology of Japan (1992): (Received Apr. 28, 1993) Short history of our Society. The Society of Agricul (Accepted June 5, 1993) tural Met. Japan, Tokyo, 16p. TAKAHASHI,K. (1990): Climatic change and society. Note Jour. Geogr., 99(3), 209-216. (J) TAKAHASHI,K., and YOSHINO,M. (eds.) (1978): Climatic This is the revised, full text of an invited paper pre change and food production. Univ. Tokyo Press, sented at the International Symposium on "Disturbed Tokyo, 433 p. Climate, Vegetation and Foods" for the 50th Anniver TAKASE,K., and KANO,T. (1969): Development strate sary of the Society of Agricultural Meteorology of gy of irrigation and drainage. In The Asian Devel Japan on 14-17 October, 1992 opment Bank, Bangkok (ed.): Asian Agricultural Survey. 513-551, Univ. Tokyo Press, Tokyo. References UCHIJIMA,T. 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the view point of East Asia. In TAKEUCHI,K. and variations on agriculture in Japan. In PARRY, M. L., YosHINo, M. (eds.): Global Environment. 16-41, Sprin CATER,T. K. and KONIJN,N. T. (eds.): The impact of ger-Verl, Berlin. climatic variations on agriculture. Vol. 1: Assess YOSHINO,M. (1992): Reconstruction of Baiu and Meiyu ments in cool temperate and cold regions. 723-868, and estimated circulation of the lower troposphere Reidel, Dordrecht. over East Asia during the little ice age. Proc. Intern. YOSHINO,M., and KOGA, K. (1990): Climate and rice Symp. on the Little Ice Age Climate, held in Hachioji, yield in Japan during the last 100 years. In Brazdil, 25-27 Sept., 1991, 152-169. R. (ed.): Climatic Change in the Historical and the YOSHINO,M., HORIE, T., SEINO, H., TSUJII, H., UCHIJIMA, Instrumental Periods. 341-343 and Supl. Vol. 93-94, T., and UCHIJIMA,Z. (1987): The effect of climatic Masaryk Univ., Brno.

過去100年 間の 日本における気候変化と米の収量 と生産量

吉 野 正 敏*

まず 最 近100年 間 の 日本 に お け る米 の 収 量 と気 温 ・ 関 係 を示 し, 8月 に つ い て は気 温 と 日照 時 間, 9月 につ 降 水 量 ・日照 時 間 の変 遷 を記 述 した。 米 の収 量 変 化 に は い て は降 水 量 と 日照 時 間 と有意 な 関係 を 示 す こ とが認 め 一 般 的 に3期 間 が 認 め られ る 。 す な わ ち,第1の 期 間 は1 られ た。 19世 紀 末 か らほ ぼ1920年 ま で,第2期 間 は そ の 後 か こ の 論 文 の 第2部 で は 上 述 の3期 間 の 米 の 収 量 の ら1945～47年 ころ ま で,第3の 期 間 は そ の後 の い わ ゆ 年 々変 動 につ いて 調 べ た 。一 般 的 な変 化 傾 間 は,第1の る第2次 大 戦 後 の 時 代 で あ る。 期 間 は ゆ るや か な 上 昇 傾 向,第2の 期 間 は ほぼ横 ば い状 次 に,気 候 条 件 の変 動 とそ れ が水 稲 生 産 に及 ぼす 影 響 況,第3の 期 間 は急 激 な上 昇 を示 め す 。 しか し,い ず れ に つ い て104年 間 の 資 料 か ら上 述 の3期 間 別 に 統 計 的 の期 間 で も,そ の 前 半 は年 々 変 動 は小 さ く,後 半 に な る 分 析 を 行 っ た。 す な わ ち,主 成 分分 析 に よ って,分 布 や と大 き い。 これ は気 候 変 動 の 周 期 性 が 原 因 で な く,農 業 周 期 性,月 平 均 気 温 ・月降水 量 ・月 日照時 間 と の関 係 を ・生産 機 構 の各 期 間 の 変 化 に 起 因 す る と考 え られ る。 調 べ た。第1主 成 分 は7月 の 上 記 の3要 素 全 部 と有 意 な

* 〒441愛 知大学文学部地理学研究室,豊 橋市町畑町1-1