A Study On The Monitoring Of Utilization Dynamic Of Permanent Basic Farmland In Hangzhou Based On Google Earth Engine

Permanent basic farmland(Yongnong)is the essence of farmland resources.To implement strict protection of farmland and guarantee food security,China has introduced a permanent basic farmland protection system and a series of related policies.However,there are still many problems with the protection of permanent basic agricultural land: abandoned farmland,seriously fragmented landscape,inadequate protection,and lax control.Effective monitoring and control of permanent basic farmland will enable the timely detection of existing problems,adjust and optimize the layout,which is of great significance for the implementation of permanent protection of high-quality farmland and the sustainable development of human.In 2010,Google launched the Google Earth Engine(GEE)platform,which can quickly process a large number of remote sensing data.It has been widely used to monitor long-term timeseries dynamic changes in natural resources such as farmland,forests,and water due to its rich geospatial data sets and powerful cloud computing capabilities.Therefore,this paper uses the GEE platform to effectively monitor the dynamics of permanent basic farmland,to grasp the changes in land use and the dynamics of cultivated land in the region,to detect the problems of permanent basic farmland protection in time,and to truly implement the protection of it.In this paper,Hangzhou,a rapidly urbanizing city,was selected as the study area.1114 scenes Landsat 5 TM,Landsat 7 ETM+,and Landsat 8 OLI images were used to create the band stacks of the target years 2000,2010,and 2018 respectively based on the GEE.And the land use classification products of Hangzhou were generated using the Random Forest algorithm.Analysis of the spatio-temporal dynamics of permanent basic farmland was done supported by GIS and land use/cover(LUCC)research theory.Based on its land-use conversion analysis,it analyzed the "increase or decrease" of permanent basic farmland with the help of Google Earth,and evaluate the effectiveness of its permanent basic farmland protection,to provide a reference for improving the permanent basic farmland monitoring system and achieving effective control over permanent basic farmland.The findings of this study are as follows.(1)With the support of GEE's massive database and strong data processing capability,this paper uses Landsat series data with a period of up to 20 years,taking into account the climatic factors in the classification process,to create a mega file data cube after cloud processing,and uses random forest algorithm to extract the land use information of Hangzhou in 2000,2010 and 2018 with overall accuracies of about 90%.And the relative error of the cultivated land area in the permanent basic farmland in 2018 and the cultivated land area in the delineation results of Yongnong in 2017 is about 13%.(2)Through the analysis of the land use of permanent basic agricultural land and the dynamic changes of cultivated land in Hangzhou from 2000 to 2018,it can be seen that the structure of land use type is relatively stable,in which the proportion of cultivated land remains above 70%.Cultivated land,construction land,and unused land are increasing,water bodies and forest land are decreasing,while cultivated land is flowing out to forest land and water bodies,a large number of water bodies are flowing into cultivated land,mainly in Xiaoshan Dajiangdong,Yuhang District,Fuchun River,and other areas.However,the overall stability of cultivated land is high,with the area of cultivated land remaining unchanged in all three phases accounting for more than 80% of the total area of Yongnong cultivated land.The decreasing amount of cultivated land is distributed close to the north-eastern plains,while the small increase is mainly close to the mountains,where continuity is worse,potentially reflecting the imbalance of cultivated land occupation.Due to the high contiguity of cultivated land in the northeastern plains such as Xiaoshan and Yuhang districts,the center of gravity of cultivated land is eastward,and the overall spatial distribution pattern is "southwest ? northeast".Although the overall flatness of Yongnong has increased over the last two decades,fragmentation has also increased.For Xiaoshan District,Yuhang District,and other plain areas of high quality contiguous,cultivated land should focus on improving the spatial form and regularity,using cultivated land readjustment,quality improvement and other means to improve the cultivated land fragmentation.But Hangzhou peripheral districts have the greater potential to improve the degree of cultivated land rules through projects.(3)With the support of GEE and Google Earth,the dynamic monitoring of the use of permanent basic farmland has been realized,effectively discovering the realistic problems of Yongnong protection in Hangzhou: 1)the existence of agricultural structure adjustment occupying cultivated land,including pond farming and planting;2)the land non-agriculture--in addition to construction occupation,the cultivated land with good production conditions,high quality of soil and great geographical location was abandoned,resulting in the waste of cultivated land resources;3)construction withdrawal in a late manner,affecting subsequent land reclamation.In response to the monitoring results,to strengthen the rigid control of permanent basic farmland and the implementation of permanent farmland space protection and effective use,this paper makes three suggestions: 1)strengthen occupation control to achieve permanent basic farmland protection;2)carry out cultivated land abandonment tracking survey,establish targeted incentive policies;3)integrate technological innovation,explore the establishment of permanent basic farmland protection and monitoring system.