Constructing The Ecological Security Patterns Of Yangtze River Delta Based On Land Use Changes

Urbanization has made great contributions on economic development and changed the way of land use.Environmental problems caused by land use change would threaten human beings' lives and ecological security.As an effective approach to support ecosystem and maintain ecological security,it is significant to construct ecological security patterns.Traditional studies on ecological planning and ecological security pattern only used one-year data,but land use change as time passed influenced not only the structure and function of landscape,but environment and ecological security.Thus,it is necessary to introduce land use change into the construction of ecological security patterns.In this study,we chose the Yangtze River Delta,one of the most developed region in China,as the study area,and improve the efficiency of land resources of Yangtze River Delta.It can help to prevent the space which is important for protecting ecological security from eroding unceasingly and to provide a model in ecological planning for other key city groups in China.Based on remote sensing image of Yangtze River Delta land use in 1990,2000 and 2010,the changes of land use types in area and transformation situation were analyzed.Then we explored the response of ecosystem service value to land use change and summarized the land conflicts of Yangtze River Delta.Taking land use types in 2010 as an example,this study assessed the ecological importance by using ecosystem service value and the ecological sensitivity by using Analytic Hierarchy Process.In the end,blue,green and compound source scenarios were set by using all the useful research result above,and ecological resistance surfaces were constructed based on probability of land use change.Corridors and strategy points in different scenarios were also established by minimum Cumulative Resistance Model.After comparing characteristics among various scenarios,this study selected the proper one and made management suggestions.The conclusions of this study were as follows:(1)The results of land use change from 1990 to 2010 demonstrated that area of construction land and water land in 2010 was 95.43%and 12.40%higher than that in 1990 respectively;the areas of arable land,grass land and wet land in 2010 were 11.75%,26.03%and 7.99%,lower than those in 1990;as to wood land,the area augmented 4.15%slightly,with an increase during 1990 to 2000 and a decline during 2000 to 2010.The results of land use transformation showed that transfer rate of arable land was the highest among all the type.The transfer rate of water land was relatively high either.In contrast,the areas transferred from wood land,grass land or water land to wet land were quite small.(2)The ecosystem service value increased 0.23%from 1990 to 2010,which presented the trend of increasing at first and then decreasing.Wood land was the main provider of ecosystem service.Water conservation,waste treatment and soil formation and erosion control were the main service type in Yangtze River Delta.The value of first two type rose 5.24%and 0.97%,while the value of soil formation decreased 3.95%totally.(3)The result of ecological sensitivity assessment showed that the area of sensitive district was 65314 km2,accounting for 31.58%of study area.Especially,the area of both sensitive in soil erosion and flood was 10369 km2,all locating in the south of Anqing city to Taizhou city.Arable land and wood land were the main land type of sensitive area.The area of wood land was 31228.62 km2,accounting for 47.91%of sensitive district.(4)The results of comparing blue,green and compound scenario demonstrated that:in compound scenario,the area of wood land and water(wet)land occupied 47.35%and 17.29%of source area respectively,highly coincident with green and blue scenario.For dominant resistance surface,value in the center was higher than surrounding value.While the value of recessive resistance was lower from north to south.For ecological resistance surface,the average value of blue scenario was the biggest,i.e.47.18,but its standard deviation was the smallest,i.e.23.66.There are 237 ecological corridors in blue scenario,355 ecological corridors in green scenario and 1219 ecological corridors in compound scenario.Owing to the vast number and minimum average length of corridors,the corridors in compound scenario can connect different source effectively and not be easily broken by human activities.Based on the contrast result of three scenarios,compound scenario was the most proper one to come up with a land management scheme.The area of low resistance district was 52118.99 km2,covering 25.20%of the whole area of Yangtze River Delta.Low resistance district and compound source composed the baseline to protect the ecological security of study area.This study proposed to restore damaged area and limit the expand speed of urban area at the same time.Medium resistance district area was 46745.27 km2,distributing in the north of Anhui Province,the west of Jiangsu Province and district around Hangzhou Harbor.In this district,under the condition that arable land minimum and capital farmland be protected,the urbanization could be processed appropriately.Besides,some economic forests and shrubwood can be brought in and the corridors should be broadened in order to increase the connectivity between landscape patches.High resistance district occupied 10.83%of the whole area.Since the effectiveness of protecting ecological security was relatively low in this area,construction could be done here in priority.