城市边缘区耕地面积变化时空特征及其驱动机制--以北京市顺义区为例

Spatio-temporal Characteristics and Driving Factors of Farmland Change on Urban Fringe:A Case Study of Shunyi District,Beijing Municipality

城市边缘区的土地资源紧缺而利用方式多样,土地利用变化既与城市发展有关又和粮食安全密切联系,因此加强城市边缘区的土地利用研究既必要又迫切。利用1990年和2000年TM影像获取的土地利用数据、1991-2002年社会经济统计数据,借助GIS空间分析方法以及数理统计方法,系统探讨了北京市顺义区耕地流失的时空格局特征及其驱动机制。结果显示,1990-2000年顺义区流失耕地的57%转为建设用地,43%转为生态用地。农用地中粮食作物的种植面积大幅减少,菜地和果园面积快速增加。工业发展是耕地流失的第一驱动力;人口城市化、房地产发展等加速耕地流失。

With the rapid economic development, land demands of different stakeholders are increasing the pressure on the limited land resources on the urban fringe, resulting in fast farmland loss. Based on the TM data in the years 1990 and 2000, combined with social-economical statistic data from 1978 to 2002, this paper explored the spatial and temporal characteristics of farmland change and its driving forces in Shunyi District, Beijing Municipality, by means of spatial analysis, GIS-based buffer analysis and mathematical statistics method. It was found that fast loss of farmland take place after the 1978. From 1978 to 2002, 38% of the farmland area in Shunyi was lost, which were mainly converted to built-up land （57%） and ecological land （43%）, and driven by land demands for urbanization and better environment. Meanwhile, agricultural land use structure changed substantially due to the expansion of urban land and economic force/market change. For example, in 2002, the sowing area of food grain crops decreased by 35.12%, while the area of vegetable and orchard increased by 3 times compared to that in 1991. This change increased income of farmers, but led to a problem of food insecurity. Three major factors contributed to these land use changes. The first is the great gap of benefits among industrial and agricultural land use in Shunyi District. The second the investment of fixed asset, e.g., the investment to real estate increased 5 times from 1998 to 2003, while that to agriculture decreased to 1/29 at corresponding time. The third is development of transportation infrastructure to meet the need of its industrialization and urbanization. The quick development of villa and other residential land use with low plot ratio caused loss of fertile farmland and other ecological land. Additionally, this paper proved that the combination of Principal Component Analysis and Stepwise Regression was an effective means to discover driving factors of farmland loss. The former was used to distinguish main factors in each category, and the latter was used to give a rational explanation of land use change.