Spatial Pattern And Driving Factors Of Urbanization In The Xi'an-Xianyang Region, Northwest China

Urbanization has significant effects in densely populated China. The increasing extant of urban built-up areas and the associated land use and land cover change (LUCC) are among major factors in considerations for resource and environmental management, in particular in ecologically fragile regions such as the western China. To better understand the urbanization process of the Xi'an-Xianyang region, we documented land cover changes between 1988, 1995, and 2006 using Landsat remote sensing data, identified the socioeconomic factors driving the changes, and revealed the spatial pattern of change between the two cities.The overall accuracy and the user's and producer's accuracies report the contribution of classification errors from each land cover type for each time period. The classification of urban and water areas achieved lower accuracies than that of agriculture and forest categories. The classification of 1995 TM data achieved the highest overall accuracy of 95.70%, followed by 1988 of 94.92% and then the 2006 of 92.19%.The land cover of the Xi'an-Xianyang region experienced a significant change in the last two decades. Overall, this region showed a large increase in urban area and decrease in agricultural area between 1988,1995 and 2006. Agricultural area was the most abundant land cover type in all three time periods with about 1,141 km2 in 1988,1,011 km2 in 1995 and 819 km2 in 2006. Meanwhile, the urban land cover of the Xi'an-Xianyang region increased 208% between 1988 and 2006. During this period the region lost about 322 km2 (28%) of agricultural and 5.5 km2 (39%) of forest lands to urban land use. respectively. The post-classification comparison change-detection identified other land cover types converted to urban land use. Quantitative analyses of the data revealed that about 147 km2 of agricultural land were converted into urban land use between 1988 and 1995 resulting in about 94% increase in urban areas. Analyses of land cover changes between 1995 and 2006 indicates that about 232 km2 of agricultural area were lost to urban land use. These significant changes resulted in an increase of about 90% in urban land cover.The buffer analysis showed an increase of urban areas between the 1988 to 2006 within the defined 1-km buffer zones and a decrease in agricultural areas. Major changes occurred in the areas further away from the city centers and close to the outer boundary of the two cities. The areas in Zone 1 to Zone 5 all experienced over 400% increase in urban land. The Zone 6 to Zone 10, on the other hand, experienced less change resulted from preexisting urban features.Several broad patterns emerged from the analyses of changes in land cover in the Xi'an-Xianyang region. Changes from 1988 to 2006 involved major transitions of land from agriculture to urban class. Results derived from the land cover data show the rates and trends of changing varied between Xi'an and Xianyang. The greater amounts of land converted to urban use occurred in the Xi'an city. The results show that agricultural land was decreased from 1988 to 2006 in Xi'an and Xianyang, however, the rate of decline of agricultural land in Xi'an was significantly higher than that in Xianyang, especially between 1995 and 2006. Meanwhile, the urban areas were increased from 1988 to 2006 in both cities. Urban area of Xianyang increased modestly from 1995 to 2006. The urban area of Xi'an has a significant change from 1995 to 2006. From the land cover map we also concluded that the immediate adjacent areas of the two cities have a relatively less change.The data reveal that the urban land has a significant change from 1988 to 2006 in the areas close to the administration boundaries. The percentage of change indicates that the areas close to urban centers experienced less change than the areas further away from urban centers where new developments occurred. For example, in the Zone 1 (1 km buffer), the change of urban area is about 489% from 1988 to 2006, whereas in the Zone 10 (the 9-10 km buffer) the change of urban areas is about 273%. This development pattern indicates that the two cities have merged into a broader metropolitan area with combined complimentary functions.Population growth, policy incentives and economic development all contribute to urban sprawl. The variability in the demographic change, especially the growth of nonagricultural employees, the socioeconomic development, and the geophysical conditions, has also had effects in urban expansion. China is under going the transition from a planned to a market economy. The policy changes in land protection and urban development have effects on patterns of urban land expansions. Economic reforms have led to massive rural to urban migrations, and generated a bi-level labor market with disparate wages between urban and rural workers. The influx of population from rural areas has lead to housing demand in the cities.The change of household size is one of the main factors that drive housing demands. In Xi'an. for example, the annual rate of growth in the number of households at 3.52% rate was substantially higher than the population growth rate of 1.83% between 1978 and 2006. The growth in population accompanied with increasing in number of houses and the decreasing in average household size. The number of families was about 1.043 million in 1978 with about 4.78 people per household. In 2006, the number of families was about 2.07 million with about 3.64 people per household. The average household size in 2006 was about 1.14 persons less than that in 1978 in this region. The decreasing average household size is among important factors that caused increase in number of houses and drove the demands on housing and urban land cover change.Urbanization is the physical growth of urban areas and the movement of people from rural areas to urban. It creates negative impacts on environments. Xi'an-Xianyang region has a long history of land use planning. Compared with other regions in Southeastern China, the urbanization process in this region is still relatively slow. Monitoring and understanding the patterns of urban development and effects on the environment in such a major metropolitan areas should be a continued effort in order to balance its economic development and environmental conservation for a sustainable development in the ecological fragile western section of China.