The Spatio-temporal Pattern Change And Driving Forces Of Cropland Loss In Rapidly Urbanized Areas

Cropland is the foundation of socio-economic development.National food security and ecological civilization construction are closely related to cropland protection.In the context of rapid urbanization,it is found that all countries in the world are facing the problem of rapid loss of cropland,which can be seen the imbalance between economy and cropland protection.Scholars at home and abroad have conducted a lot of researches from the natural,geographical,social,economic and other perspectives,but the research on the evolution of the spatio-temporal pattern of cropland loss and its comprehensive driving forces,especially the quantitative research on the implementation effect of relevant policies on cropland,is still insufficient.Currently,there is still controversy over the role of policies in the loss of cropland.Therefore,this study took the Su-Xi-Chang region(Suzhou,Wuxi,Changzhou,Jiangsu Province)as the research area.Based on remote sensing data,socio-economic statistical data,and policy documents,this study quantitatively evaluated the implementation effectiveness of national,provincial,and municipal policies related to cropland protection.Linear regression and panel regression models were used to explore the evolution of cropland loss in the study area from 1990 to 2018,and the impact mechanism of cropland loss was quantitatively evaluated from spatial,socio-economic,and policy perspectives.The results showed that:(1)There is a phenomenon of cropland loss in all districts and counties in the Su-Xi-Chang region,with Suzhou,Wuxi,and Changzhou city centers experiencing the most significant loss of cropland.From 1990 to 2018,the amount of cropland transferred out reached 3816.95 km~2,of which over 88%was converted into urban land.The amount of cropland loss and the loss rate(cropland loss amount/total cropland in the initial stage of the study)fluctuated continuously.At the municipal level,the amount of cropland loss was Suzhou(2532 km~2)>Wuxi(1500 km~2)>Changzhou(1216 km~2),and the cropland loss rate was Wuxi(0.29)>Suzhou(0.27)>Changzhou(0.25).At the district/county level,Yixing City in Wuxi had the highest amount of cropland loss(633 km~2),Liangxi District in Wuxi had the lowest amount of cropland loss(25 km~2),Gusu District in Suzhou had the highest rate of cropland loss(0.51),and Wuzhong District in Suzhou had the lowest rate of cropland loss(0.15).(2)In terms of spatial driving force,the expansion of urban land was the most significant factor leading to the loss of cropland in the Su-Xi-Chang region.For every 1%increase in urban land,the loss rate of cropland increased by 0.39%.The elevation(0.12),the distance from cropland patches to the city center(-0.04),the center of districts and counties(-0.07),main roads(-0.13),and railways(-0.16),as well as the cropland aggregation index(-0.08),had significant impacts on cropland loss.The higher the elevation of cropland patches,the greater the loss rate of cropland.The distance and the rate of cropland loss was negatively correlated,and so was the aggregation index.In terms of socio-economic driving forces,effective irrigation area,non-agricultural population and fixed assets investment were the top three main factors affecting cropland loss rate.For every 1%increase in effective irrigation area,the loss rate of cropland decreased by 0.3%.For every 1%increase in the number of non-agricultural population,the loss rate of cropland increased by 0.21%.For every 1%increase in fixed assets investment,the loss rate of cropland would increase by 0.09%.(3)In terms of policy driving force,from 1990 to 2018,the score of macro policies(China,Jiangsu Province)increased almost 9-fold from 89 to 858.The score of local policies(Suzhou,Wuxi,Changzhou)increased from 0 to 218.From the perspective of policy effectiveness,local policies could effectively curb the loss of cropland.For every 1%increase in local policy scores,the loss rate of cropland decreased by 0.14%.The impact of macro cropland protection policies at the national or provincial level was not statistically significant,indicating that the protection effect of macro policies on cropland was lower than that of local policies.Combined with policy factors and socio-economic driving forces,the degree of impact on cropland land loss rate was:effective irrigation area(-0.33)>non-agricultural population(0.2)>local policy(-0.14)>total social fixed assets investment(0.13)>macro policy,that is,local policy played a stronger role in protecting cropland than total social fixed assets investment.Through the case study of the Suzhou,Wuxi,Changzhou,it is possible to have a comprehensive understanding of the long-term evolution patterns and spatial pattern characteristics of typical rapid urbanization areas with cropland loss.In addition,through the comprehensive driving force analysis framework of geographical space,socio-economic,and policy constructed in this study,not only can the implementation effect of policies related to cropland protection be quantitatively evaluated,but also the driving force behind cropland loss can be systematically understood,which provides decision-making reference for identifying the key influencing factors of cropland loss and formulating effective policies for the balance between cropland protection and socio-economic development.