Spatiotemporal Patterns Of Urbanization And Arable Land Protection Analysis In Zhejiang Province

Since the implementation of the reform and openning-up policy, Zhejiang Province, as the economically developed eastern coastal regions of China, as been experiencing unprecedented urbanization and industrialization. Despite of numerous benefits brought about by rapid urbanization, dramatic encroachment upon cultivated lands has severely threaten the future development, for Zhejiang is a province lacking of plain resources. It is urgent to identify the spatiotemporal pattern of urbanization, providing scientific basis for promoting future urbanization. A framework integrating remote sensing, geographic information systems and landscape ecology is presented on the perspectives of sustainable urban development to explore the dynamics, pattern and driving forces of urbanization among cities of different size and geographic zones from 1990 to 2010. What’s more, potential impacts of threat to soil resources, arable land protection policies are also discussed. Finally, as a case study of Linan city, one of the land shortage hilly regions experiencing rapid urbanization in northwestern Zhejiang Province, this study also explores measures for coordinating economic growth and arable land protection. The main content and results of this research are as following:First of all, this study analyzed the intensity, spatial pattern and driving forces of built-up sprawl from 1990 to 2010 of Zhejiang Province. Results showed that the percentage of built-up of Zhejiang Province increased from 4.4%　in 1990 to 6.6%　in 2000 and to 10.6%　in 2010. The newly expanded built-up area mainly distributed on the regions below 50 meters and within 5 degree’s slope. Distance to roads, city center and existed built-up area, population, GDP, investment in fixed assets and government policy had great effects on the spatial distribution of newly expanded built-up area. The expansion of built-up exhibits auto-correlationship among cities of Zhejiang Province. Rapid expansion was observed in the Northeastern Zhejiang Province, while low expansion was observed in the Southwest. Meanwhile, landscape analysis showed that built-up area became more fragmented, irregular and aggregated.Through monitoring the spatiotemporal characteristics of urban built-up areas (UBAs) expansion, urban land use efficiency and urban development strategies, urbanization discrepancy among cities of different size and geographic zones for 69 cities/counties of Zhejiang Province, this study also discussed the implementation of "smart growth" for achieving sustainable urban development. Results showed that urban built-up areas of Zhejiang Province increased from 1329.2 km2 in 1990 to 1999.7 km2 in 2000, and 4166.4 km2 in 2010, revealing the fact of rampant urban expansion. The population-based urbanization rate lagged behind the land-based urbanization rate. Especially in the 2000s, the elasticity of settlement expansion to urban population growth during this period up to 2.85. Meanwhile, there’s apparent intraprovincial distinction existed in urbanization among cities of different size and geographic zones. The UBAs in the central basin Zone had sprawled more than five times during the last two decades, where the urban area per person reached 360 m2, 1.6 times that in the eastern hilly Zone. The rampant urban sprawl contributed to the more irregular in UBAs shape, especially for the period of 2000-2010. During this period, the area of UBAs for the Zhejiang Province had been doubled, gradually blurring the boundaries between urban and rural. The regional urban development model of metropolitan circle had appeared. However, the urban land use efficiency continued to decline at the provincial scale, which can be contributed to the governmental encouragement of developing large cities and the increasing desires of urban population to enjoy capacious living space with more public recreation areas.Rapid urbanization and industrialization happened in Zhejiang Province also imposed great challenge to soil resources characterized by dramatic soil sealing and soil landscape heterogenization during the past two decades. It is a severe threat for Zhejiang Province, for it is a province lacking of plain resources. More seriously, the built-up area expansion occupied preferentially high-quality soils that are distributed in plain regions, especially paddy soils. Paddy soils and the excellent soils (Level I) contributed almost 60%　and 70%　respectively in the occupied soils. The invasion to high-quality soils is severest in large-sized cities, for the two large-sized cities of Zhejiang Province are both located on plain region. Although cities of all the levels had made great efforts to expand the built-up and preserve high-quality arable lands, for instance, reclamation from sea in large cities and construction in mild slope region in small cities, the sealing of high-quality soils in large scale still continues. Furthermore, the constant built-up expansion resulted in soil landscape fragmentation and irregularly shaped. The dominance of soil landscape gradually reduced by accelerated built-up sprawl. The spatial regression revealed that there were significant correlations between urban intensity index (UII) and soil patch density, area-weight mean shape index and aggregation index.By integrating land use survey data, remote sensing images, we evaluated the arable land occupied for built-ups expansion and supplemented arable land for Hangzhou region from 2004 to 2010. It aimed to explore and compare the spatial pattern, soil quality, zone location and land management between occupied/supplemented arable lands. Results showed that the occupied arable lands mainly consist of fertilized soils that distributed on flat plain, while majority of the newly supplemented arable lands were reclaimed from sea or mild slope lands, which had no tillage history with poor soils. Landscape pattern analysis revealed that the supplemented arable land patches were less connected to the existed arable patch. Moreover, a large portion of them were located in rural-urban fringe regions, and had high risk of being occupied again by urban expansion in the future. Remote sensing images of 2010 and 2013 were used to monitor the cultivation management of the supplemented arable lands between 2004 and 2010. The calculated index of vegetation coverage indicated that the vegetation coverage in most cities had significantly improved. However, vegetation coverage of individual cities showed declined trend, several blocks were even abandoned by no vegetation coverage.Finally, taking Linan, a hilly city in western Hangzhou, as a case study to explore and evaluate how it overcome the terrain restriction to coordinate the conflicting of accelerating urbanization and protecting limited arable lands. Results showed that an area of 7465 ha of mild slope lands had already been explored for built-ups expansion till the end of 2012, accounting for about 60%　of the total built-up area of Linan city. During the first half period of the overall land use planning (2005-2012),68%　of the incremental construction land quota had been allocated on mild slope lands in the city proper. Compared to the developed mild slope lands for built-up expansion before 2005, the developed mild slope land patches during 2006-2012 were larger and more aggregated in spatial distribution. Meanwhile, the land use type of the explored mild slope lands during 2006-2012 was more diversified, mainly industrial/technology lands, followed by residential lands and tourism lands. Furthermore, taking the mid-term revision of overall land use planning as an opportunity, the government department of Linan city further improve the exploration intensity of mild slope lands for built-up expansion for the next half planning period (2013-2020). Through revising the spatial distribution of the newly expanded built-up area, it was requested to avoid the occupation on arable lands as far as possible, and effectively reduced the index of occupation on arable lands by built-up expansion to 40.2%　during 2013-2020,compared to that 73.5%　in 2006-2012.The urbanization rate of Zhejiang Province is relatively low compared with national average. Thus, improving the urban population rate and optimizing urban spaces are proved to be an urgent task in the future. The development strategy of metropolis circle would absulutely stimulate the development of medium-　and small-sized cities, which increacing the difficulty of eco-environmental construction and arable lands protection in these regions. Therefore, cities of different size had better take advantage of locational resources, for instance, reclamation from sea and construction in mild slope region, to reduce the occupation on high-quality soils, especially limited arable lands, and finally to promote the sustainable development of urbanization and social economy.