Spatiotemporal Changes in Cultivated Land Area in China from 1998 to 2006

We used provincial data on current land use and conversion between different land types during 1998～2006 to analyze the spatiotemporal changes in cultivated land in China.The results showed distinct changes in the spatial structure of cultivated land,with declining conditions in the Huang-Huai-Hai Plain,the Yangtze River Plain,and the southeastern coastal region of China.There were 20 provinces which experienced a reduction in irrigated cultivated land,and six of these lost more than 7% of total irrigated area.Cultivated land area decreased linearly from 1998 in all provinces except Xinjiang and Heilongjiang,with the most area lost in Inner Mongolia.The most notable changes were in regions that experienced rapid economic growth,including the Beijing-Tianjin-Tangshan region,the Yangtze River Delta and the Pearl River Delta.The mixed agro-pastoral zone on the Inner Mongolian plateau and areas along the Great Wall also exhibited strong changes.There was significant regional variation in the increase and decrease of cultivated land area.Cultivated land was reduced mainly in the Loess Plateau,Inner Mongolian plateau,along the Great Wall,and in the eastern regions.Increases in cultivated land occurred mainly in western China,causing environmental degradation.The reasons for changes in cultivated land area also varied.In the Loess Plateau,Inner Mongolia plateau,and the area along the Great Wall,reduction was due to government programs to reduce environmental degradation.In the developed eastern coastal regions,the reduction of cropland was mainly due to adjustment of agricultural structure and use of cultivated land for construction.In the western regions,the reason for increased cultivation was land exploitation,while in the eastern regions,the reasons for the increase were land exploitation and land consolidation.Building on previous farmland occurred mainly due to independent mining and expansion of villages,which occurred in the important national grain production regions.All of these factors led to an overall reduction in the quality of cultivated land and environmental degradation, which threatens China's food security.Therefore,it is necessary to strengthen the intensive use of land resources and achieve a dynamic balance of cultivated land quantity and quality using protective measures such as limits on the use of cropland for construction,as well as strict controls on the unchecked expansion of large and medium-sized cities,strengthened rural planning,and protection of fertile cultivated land.