Habitat Network Optimization Based On Cost-benefit Analysis And Network Efficiency Analysis

The rapid socio-economic development and the urbanization leads to a large-scale urban expansion.At the same time,the intensive land use,land-use conversion,and narrow-mindedness and other human factors,result in rapid urbanization areas of species suitable habitats and exacerbate the fragmentation phenomenon of habitat patches,which greatly hindered the proliferation or migration of species and brought the destruction of biodiversity and the ecological balance of the entire region.According to researches,it helps to strengthen the protection of individual species habitat,establish ecological linkages between habitat patches,and promote the exchange of genes and species migration to establish habitat network.Habitat network can provide ecological services to humanity,create social benefits,improve the quality of human’s life,make great effect on sustainable development and maintenance of ecosystem effects.However,the traditional approaches to evaluation and optimization of habitat network has some problems,such as the fitness to the integrated regional development objectives,low degree of coordination habitat network protection and land resources management,and the low degree of combination between land use planning and network optimization.Those factors reduce the feasibility and effects of network optimization program.Therefore,it is significant and necessary to explore some approaches/methods to make habitat network evaluation and optimization which is suitable for rapid urbanization area.As a case study,we focused on the Su-Xi-Chang area of the Yangtze River Delta Region,with the little egret(Egretta garzetta)as a regional representative species.This study uses two cross-disciplinary approaches between methodologies in economics,topology and ecology,to examine the impacts of the approach and ecological processes on network optimization methodology.Furthermore,it establishes two kind of analysis approaches,cost-benefit and network efficiency analysis,to achieve the habitat network evaluation and optimization.In the part of habitat network optimization based on cost-benefit analysis,we hypothesized that adding new habitat patches would improve network connectivity,and help with network optimization.The study assessed the size and the land use type of 35 habitat patches,which were identified using ArcGIS software and prior research results.The cost of avoiding the transfer from the current habitat into other land use types,especially construction land,was treated as the protect-cost,which was derived from local prices for land acquisition.From the perspective of network structure,the benefit of habitat network connectivity improvement was represented as a comprehensive indicator generated from three different indexes.These indexes included the number of newly added corridors,the betweenness,and the node degree.The protect-cost of each habitat patch could be matched to its corresponding benefit value for different purposes.The study design considered five different conditions and six scenarios.Scenario 1 was formed from the perspective of minimum cost accumulation,whereas scenarios 2 to 5 focused on maximum benefit accumulation,best effectiveness accumulation,and two limited effectiveness accumulations,respectively.Scenario 6 was the ideal condition meaning with all 35 habitat patches being added as the ideal result of habitat network optimization.The results indicate that(1)scenario 2 of maximum benefit accumulation resulted in network optimization with a lower total cost compared to scenario 6.Scenario 3 of best effectiveness accumulation resulted in network optimization with the least protected area,and associated cost.(2)The effects of the scenarios of best effectiveness accumulation,as well as the one of minimum cost accumulation(i.e.,scenario 3 and scenario 1,respectively)were similar.However,the total cost of scenario 3 was only 74 percent of that of scenario 1.This indicates that scenario 3 of best effectiveness accumulation maximized effectiveness with the least cost,and was suitable for rapidly urbanizing areas with scarce land resources.(3)The effects of the two scenarios of limited effectiveness accumulation,(i.e.,scenario 4 and scenario 5)were in between the effects of scenario 1 of minimum cost accumulation and scenario 2 of maximum benefit accumulation.This indicates that all scenarios of limited effectiveness accumulation would realize the aim of better effectiveness with lower cost.Furthermore,it indicated that scenario 3 of best effectiveness accumulation was gained under special circumstances.In economics,this phenomenon is referred to as the marginal benefit.In the part of habitat network optimization based on network efficiency analysis,as the case study,the Su-Xi-Chang area of the size of 1.751<105 km2 was selected as a small-scale study area,other 12 neighbor cities together with the Su-Xi-Chang area of the size of 11.91×105 km2 as a large-scale study area.The approach was designed three steps:(1)A conceptual framework of network efficiency analysis was built for optimizing habitat network,in which the concepts of the small-world network and the scale-free network were introduced,as well as their network structural characteristics including average path length,cluster coefficient,probability distribution of node degree.These structural characteristics were applied in step 3 as the assessment indicators.(2)The little egret’s habitat patches and its small-and large-scale habitat networks were identified and simulated respectively.The present status small-scale habitat network was the prior research result.In the large-scale area,the observation sites obtained from a data-set(2003-2015)of the China Bird Report’s website were regarded as the habitats,and those sites where over 20 little egrets were observed simultaneously were picked out and transferred to habitat patches.Then the large-scale habitat network was simulated using the same method of the prior research.(3)Based on the large-scale habitat network,the present status small-scale habitat network was optimized to the network A.Through adjusting the network A’s structure and transferring its network structural characteristics the network B was generated.The network connectivity indexes α,β and γ of the present status small-scale habitat network,the network A and B were calculated and compared.The results show that:(1)The network A and B are the optimized results of the present status small-scale habitat network.(2)That the increased average path length value,decreased cluster coefficient value and increased goodness-of-fit of probability distribution of node degree of the network B,compared with those of the network A,reflects that the network B’s small-world network characteristics has been decreased,but its scale-free network characteristics increased.This states that the network B is superior to the network A when fitting with the large-scale habitat network.(3)The amounts of newly-added habitat node and migration corridor of the network B are less,but its corresponding values of the network connectivity indexes α,β and γ are more than those of the network A.This reflects that the network B is superior to the network A and is the recommended optimizing result.The study indicates that optimizing habitat network using network efficiency analysis method realizes the aim of better effectiveness,highlights on the methodology of network structure optimization,and provides the theoretical base of a better goodness-of-fit for spatial planning among upper-and lower-levels.Overall,the combined method detailed here,along with ecological,economic,topological and social factors,contributes to habitat network optimization,and highlights the methodology of network optimization.But for the aim of conceptual framework improvement,further discussion are needed including the aspects of network hierarchical analysis,scaling and network quality assessment indicators,and the combined method of both analysis approaches.