Study On The Optimization Of Ecological Network In China Based On The Identification Of Priority Areas And Ecological Corridors

Rising urban expanding and increasing human activities in China have caused a strong change in land use,so that a series of ecological processes including species migration,material and energy flow will be under serious threat in the short and long term.Developing a highly interconnected ecological network at the national level is one of the effective means of protecting biodiversity and maintaining ecosystem stability.Currently,China still lacks a large-scale ecological protection plan to ensure the smooth running of various ecological processes in the ecosystem at the macro level,and the existing nature reserve system also needs to be further improved.Therefore,this study integrated the protection of priority areas and the identification of potential ecological corridors,regarded as nodes and links,to build a large-scale ecological network,and then evaluated the connectivity and effectiveness of this network through the landscape connectivity index analysis method.A representative,connected and effective macroscopical ecological network framework was proposed.Firstly,a spatial prioritization software,ZONATION,was used to identify protection priority areas.Land cover types were included in this model and cities were regarded as pollution sources.The least meaningful part of contributions to species protection and habitat maintenance was gradually removed from the landscape by ZONATION.At the same time,the marginal loss of the protection value of the entire research area is guaranteed to be minimized.After operation,a hierarchical mask representing the priority of protection value was obtained.The top 20% was selected as priority areas,and overlapped with the existing nature reserve for GAP analysis.The results showed that priority areas cover 12.9% of the region,mainly distributed in mountainous and plateau areas.There is an obvious spatial mismatch.between priority areas and China's existing nature reserves.Secondly,ecological corridors were identified based on the least-cost pathway method.According to the resistance of different land use types to material and energy flow in the ecosystem,the whole landscape was considered as a cost surface.The minimum cumulative resistance between the source and the destination to all points on this surface were calculated and summed.The grid less than a certain threshold value was then extracted to obtain the potential corridors.The result indicated that ecological corridors were distributed to avoid the optimal development areas in China such as Beijing-Tianjin-Hebei Economic Circle,Yangtze River Delta,and the Pearl River Delta.It is important to note that development of cities leads to deviation from the shortest straight line between two patches.Thus,these corridors have no choice but to keep away from high-density buildings in residential areas and distributed along the urban boundaries.Finally,the macro ecological network was established on the basis of connectivity analysis.The equivalent connected area(ECA)index was used to compare the landscape connectivity level differences of ecological network under different thresholds,and the integral index of connectivity(IIC)and the probability of Connectivity(PC)was used to measure the contribution to the maintenance of connectivity of each patch.Priority areas of high importance were then identified as key nodes in the ecological network and an ecological protection network framework of "one core,two wings,four cores and four belts" was ultimately proposed.The results showed that the connectivity level of the network is greatly affected by the characteristics of patches themselves.Priority areas with large area,strip type and relatively complex boundaries were of high importance,making a great contribution to maintaining the landscape connectivity.From the perspective of ecological protection,it is necessary to redefine the scope of nature reserves,especially in the Changbai Mountain,Nanling,Min-Zhe-Gan Mountainous Area and the group of the middle and lower reaches of the Yangtze River.There is a need to create new protected areas or to expand the boundaries of existing protected areas,and to consider the internal connectivity.This study would provide a scientific method for the identification of important ecological patches.It can be also used as the theoretical support for the formulation of long-term ecological protection planning and and the theoretical basis for the development of relevant research on ecological network.