Special Column:Celebration of the 70th Anniversary of IGSNRR, CAS
TIAN Guang-jin, ZHOU Quan-bin, ZHAO Xiao-li, ZHANG Zeng-xiang, TAN Wen-bin
After the implementation of Reform and Open policy,the double-pressure of rapid economic development and population growth has imposed an unprecedented profound impact on Chinese dynamic change of land-use patterns.One of the most important problems is the urba-nization encroachment on cultivated land.China's per capita arable land is0.106ha,only making up44.9%of the world average.In the coastal area,a great amount of cultivated land was en-croached by urban expansion.Two-time TM images in1988and2000are used to monitor urban encroachment on cultivated land.The dynamic results revealed that of the land occupied due to urban expansion,80.2%is cultivated land and19.8%is forest land,grass land,rural area and other land.Index RI (Urban encroachment on cultivated land taken total land percent in the city and county)is built to study the regional difference.The cultivated land loss from grade3～6in coastal and plain area is about 88.68%while North China Plain is31.27%,Yangtze River delta17.8%and Pearl River delta is6.02%.The three parts witnessed the fastest urban expansion and cultivated land loss in China.The urban encroachment on cultivated land in Jiangsu,Shandong,Henan,Hebei and Guangdong takes about 50.99%and Beijing,Zhejiang,Sichuan,Guangxi,Shanghai takes22.85%.Except for Henan(located in North China Plain)and Sichuan(in Sichuan Basin),the others are coastal provinces.The cultivated land loss rate in Beijing and Shanghai is the fastest while that in Jiangsu,Guangdong,Zhejiang,Tianjin,Shandong,Hebei and Hainan comes second.With the rapid economic development and urbanization,the paradox between urban expansion and cultivated land will be more serious.Only more positive measures are taken to slow down the rate of cultivated land loss can the grain security be guaranteed.Firstly,the high-productive land should be protected.Secondly,high technology and machines should be applied to increase per unit area grain production.Thirdly,the rural residential land should be reclaimed with the local residents' immigration into cities and towns.
