Institute of Geography, Asahikawa Campus Hokkaido University of Education Asahikawa, 070-8621, Japan 1. Introduction Urban expansion is one of the most important features of land use/cover changes in the world, and it is particularly so in such a country as Japan where population density has been high and urbanization rapid. A difficult problem encountered in the study of urban expansion is identification or delineation of settlement or urban areas. Himiyama (1985) applied a unique computer-based method to delineate urban areas on the 1:25,000 land use maps of Japan, and compared land use structures of fourteen urban areas belonging to small to large cities. Himiyama (1995) used 1:50,000 topographic maps of Japan to identify the distribution of settlement as well as other types of land use in the whole country at ca. 1900, 1955 and 1985, and
showed its changes and driving forces in a long time range. 1:50,000 topographic maps offer detailed and accurate spatial information of settlement distribution, but the printed maps not only need to be digitized before being processed on a computer, but also lack frequent up-dating. Otomo (1997) stresses the usefulness of the statistics of Densely Inhabited District (DID) in order to fill these gaps and to enhance understanding in urbanization in the post-war Japan. DID statistics has been issued by the government every five years since 1960 (Statistics Bureau of Japan, every five years). Okinawa, the southernmost prefecture in Japan which was occupied by the US till 1972, started to appear in the DID statistics from the 1970 census. The interval of up-dating DID statistics is much shorter than that of 1:50,000 topographic maps, and it is a clear advantage for the study of urban expansion. Another advantage of DID Statistics is that it is available in digital form, while topographic maps are not. Although the DID is basically delineated according to population density rather than land use and may differ from the actual urban area to certain extent, it is considered to be an invaluable information source for LUCC in general and for the study of urbanization in particular. Figure 1 shows the 1:50,000 topographic maps of Asahikawa and Utsunomiya, together with their DIDs and sets of 1km grid cells shaded where settlement in a broad sense is larger than other land use types in order to check the fitness of the urban areas defined in different ways. The settlement grids and the DID fit fairly well in the former, but in the latter the difference is larger, reflecting the more complex mixture of urban and rural land uses in Utsunomiya. Figure 1 DID and settlement -dominated 1km grid cells (shaded) in Asahikawa (top) and Utsunomiya (bottom)
2. Changes in DID Population 2.1 DID population in Japan Reflecting the rapid urbanization in Japan, the population in DID increased from 40,830 thousand in 1960 (excluding Okinawa, which was then occupied by the US) to 82,810 thousand (81,957 thousand excluding Okinawa) in 2000, i.e. doubled in 40 years excluding Okinawa (Figure 2). The DID population in 2000 occupied 65.2% of the total population of Japan, while that in 1960 occupied 43.7%, i.e. the share of population in DID increased for more than 20% in 40 years. The increase rate per 5 years was the highest during 1965-1970 at 18.4%, then it gradually slowed down, and during 1995-2000 the increase rate was as low as 1.9%. The decline of the increase rate reflects the decline of both natural and social increases of urban population. 2.2 DID population by prefecture Figure 3 shows the trend of the DID population in each of the 47 prefectures in Japan. The dominance of Tokyo is evident, but its high growth rate lasted only till 1975, and the increase since then, i.e. after the oil shock, was quite small, reflecting the decreased demand for urban expansion towards the remaining hilly, less favourable sites. The slightly higher increase in Tokyo during 1995-2000 is considered to be mainly due to the in-migration of people to the city centre, as evidenced by the increase of population in the central part of Tokyo during 1995-2000 (Figure 4). Osaka, which has the second largest DID area, shows a similar trend, i.e. sharp increase till 1975 and very small increase since then. Kanagawa, which is adjacent to Tokyo and has the third largest DID population, keeps its high rate of increase, and may surpass Osaka by 2010. Saitama and Chiba, which are also adjacent to Tokyo, show similar trends to Kanagawa.
The increase rate during 1960-2000 in Kanagawa, Saitama and Chiba is 230%, 505% and 534%, respectively (Figure 5). Nara (+412%) and Shiga (+241), which are both located close to Osaka and Kyoto, also show high increase rates of over 200% during 1960-2000. The increase rates of most prefectures during this period range within 30-150%. The concentration of prefectural population within the DID in 2000 is the highest in Tokyo (98.0%), and then Osaka (95.7%), Kanagawa (93.6%), Kyoto (81.5%), Saitama (78.2%), Aichi (74.8%), Hyogo (74.3%) and Hokkaido (72.7%) follow. Hokkaido is far from metropolitan areas, where the other seven prefectures belong, but it has more distinctive urban and rural areas than in other parts of the country and the concentration of population in the cities is high. 3. Changes in the Area of DID 3.1 Area of DID in Japan DID represents urban area. The area of DID in Japan was 12,457 km 2 in 2000, i.e. more than three times that of the 1960 figure of 3,865 km 2, and occupied 3.3% of the country s land area (Figure 6). This increase rate is about 50% higher than that of DID population, indicating the decline of population density within DID. The area of DID increased moderately at 19.1% during 1960-1965, and sharply at 40.0% (39.0% excluding Okinawa) during 1965-1970, then the increase gradually slowed down, and during 1995-2000 the increase rate was as low as 1.6%. This trend, which generally follows a logistic curve (Fujii, 2001), together with ceasing of the country s population growth and growing economic hardship, suggests that the increase rate of the DID area during 2000-2005 would be close to nil, if not minus.
a) The high economic growth in the 1960s, particularly that in the latter half of the decade, attracted rural population to urban areas, stimulated urban development, and promoted motorization, which further
accelerated urban expansion, i.e. expansion of the DID. b) The oil shock of 1973 marked the end of the high economic growth started in 1955, and together with the oil shock of 1978 had a strong negative effect on the country s economy, and consequently on the urban development, in the latter half of the 1970s. c) The effect of the two oil shocks continued into the first half of the 1980s, but the effect of the new government s policies led by the San-zen-so, or the Third Ten-year Comprehensive National Development Plan (1975-1985), which put emphases on calming the development fever that prevailed during the period of the high economic growth and reducing the population concentration in metropolitan areas, was no less greater than that. d) The reduced increase of DID area in the first half of the 1980s was recovered in the second half of the 1980s, when what was called the bubble economy prevailed throughout the country. Tokyo s DID area is the largest throughout the whole period, but its dominance is not as much as that of the DID population, and its increase during 1990-2000 is mere 2%. Unlike the DID population, the DID area in Tokyo did not increase much during 1995-2000, indicating that most of the increased population was absorbed in the existing urban area. Osaka, which has the second largest DID population through the whole period, shows smaller DID area than Kanagawa since 1985, and its increase rate during 1995-2000 was only 0.47%, suggesting the scarcity of suitable site for new DID. 4. Changes in DID Population Density
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In Toyama prefecture, which is on the Japan Sea coast and is remote from the country s core region, the decline of DID population density had been particularly fast, and it reached 4,051 km 2 in 2000, which was the second lowest only after Yamaguchi. It was probably caused by out-migration from DID to nearby rural areas (Hamamatsu, 2002). It results in a mixture of urban and rural land uses, which is generally considered as unfavourable from land-management point of view ō
Figure 13 shows the trend of the rate of change in population, area and population density within DID. The increase rate of the area of DID surpassed that of the population of DID in all the periods except 1995-2000, and it resulted in the minus change rate of the population density in DID till 1995. The change rates in the period 1965-1970 were the largest for all the three variables, reflecting the rapid economic development which accelerated urbanization, which in turn contributed to the easing of population pressure within urban areas. The easing of the population density within DID continued, but at a slower speed, and it reached zero in the period 1995-2000. This suggests that urbanization in Japan in the coming decades will not involve much urban expansion, and internal and qualitative changes of urban areas will become more important. The analysis of the DID statistics at national and prefectural levels has proved its use for the LUCC study in general and for the study of urbanization in particular. The findings of the study include the following: a) DID population in Japan has been increasing in a logistic curve, and the increase is now small, indicating its smaller increase in coming decade. Chiba and Saitama next to Tokyo, and Nara next to Osaka show very high increase rates of DID population. The trends show a strong influence of the rapid economic growth till 1973, bubble economy, and government s policy in the 1980s. b) DID area in Japan has also been increasing in a logistic curve, and the increase is now small, indicating its smaller increase in the coming decade. The increase rate of DID area has been higher than that of DID population, resulting in the decline of DID population density in most prefectures. Chiba, Nara, Saitama, Okayama and Shiga show very high increase rates of DID area. The trends show a strong influence of the rapid economic growth, bubble economy, and government s policy. c) DID population density in Japan has been declining since 1960, and it has reached a stable stage at
6,647 km 2. Kanagawa and Saitama next to Tokyo are exceptional in that they show increase of DID population density since 1980. The findings in this paper are very useful in understanding and modelling urban expansion. It is desired that the DID statistics is more widely used in Japan and elsewhere, and that it stimulates the production and analyses of a similar statistics in other countries.