The Delimitation Of Urban Growth Boundary Considering Cropland Protection And Ecological Protection

China is in the stage of rapid urbanization,which will cause a series of problems,such as loss of arable land and ecological land,environmental pollution,traffic congestion,etc.And it has become the consensus of many scholars to control the rapid expansion of cities.UGBs(urban growth boundaries),as a dominant strategy for urban expansion control,have been widely practiced all over the world and become very popular among scholars and planners.The existing studies on demarcation of UGBs have not reached the balance between farmland conservation and ecological land protection or reached the coordination between urban expansion,farmland conservation and ecological land protection.To solve these problems,this thesis puts forward a UGBs delineation method by balancing farmland conservation and ecological land protection.The UGBs delineated by this method was supposed to occupy less cultivated land and ecological land.And the quality of occupied cultivated land and ecological land was also supposed to be lower.Furthermore,the spatial form of UGBs was supposed to be relatively superior.We want provide some certain theoretical references and technical support for UGBs delimitation research and practice through this method.In this thesis,Wuhan city is taken as the research object.Firstly,the land system simulation and optimization model(LANDSCAPE)based on cellular automata is applied to realize the balance in land use simulation of Wuhan in 2035.Then we use expansion and erosion algorithm,which uses the principle of expansion and erosion,to delineate the UGBs of Wuhan in 2035 based on the result of land use simulation.Finally,we makes a comparative analysis between the UGBs demarcated by balancing farmland conservation,ecological land protection and the UGBs demarcated by existing methods.The main conclusions of this thesis are as follow:(1)This thesis realizes the weigh among all farmland and ecological land in the process of UGBs delineation.In this thesis,first we evaluate land production potential and ecological importance of Wuhan city.Then we make the cropland with higher land production potential and ecological land with higher ecological importance more difficult to be occupied by urban land.As a result,we can weigh all farmland and ecological land in the process of UGBs delineation.(2)The method of UGBs delineation,which weigh both cropland protection and ecological protection,has some advantages.From the results,we can see that the UGBs delineation method proposed in this paper is better than the existing constrained or unconstrained method in terms of the quantity and quality of occupied cultivated land and ecological land,as well as the compactness of urban space form.(3)This thesis realizes the balance among urban expansion farmland protection and ecological protection.The compactness of the UGBs delineated in this thesis is better than the UGBs delineated by the existing constrained or unconstrained method.This indicates that the UGBs delineated in this thesis is relatively good in space and realizes the coordination between urban expansion,farmland protection and ecological protection.(4)The existing independent demarcation of "three lines"(permanent basic farmland boundary,red line of ecological protection and urban growth boundary)is not conducive to the coordination between urban expansion,conservation and ecological land.No matter the boundaries of permanent basic farmland,ecological protection red line or urban growth boundary are first drawn,the delineated line will be the constraint condition.However the line delineated by constrained method will cause the loss of land production potential and some important ecological land.It also fails to achieve the coordination among urban expansion,farmland conservation and ecological land protection.On the basis of the research conclusions,this thesis puts forward the following policy Suggestions:(1)When demarcating the urban growth boundary,the farmland conservation and ecological land protection should be fully balanced.(2)The "three line" shall be demarcated in coordination at the same time.We should first balance urban expansion,farmland conservation and ecological land protection,before drawing permanent basic farmland,the red lines for ecological protection and urban growth boundaries on the basis of balance.(3)Relevant planning departments should introduce some relatively mature land use simulation and UGBs demarcation methods and tools to improve the efficiency of demarcation of the "three line".