Research On Ecological Risk Assessment Of Beijing From The Perspective Of Adaptive Cycle And Spatial 0ptimization Strategies

At present,the global climate changes rapidly and extreme climate occurs frequently.Beijing is experiencing a period of rapid development and expansion,during which the ecological space is constantly occupied.Nature and social disturbance make the social-ecological system of Beijing faces severe environmental risk.Urban green space is the key element to resist ecological risks and enhance urban ecological resilience.According to the research of current situation,the landscape fragmentation of green space in Beijing is high,so that the ability to resist ecological risks is low.Therefore,it is urgent to comprehensively evaluate and predict the characteristics of urban ecological risk,and put forward more effective optimization strategies to resist ecological risk.By summarizing the current research,it is found that the framework of urban ecological risk is mostly a static assessment of "exposure" and "interference" effects of risk sources,which ignores the dynamic interference on the ecological environment and resilience response of city.Therefore,the traditional risk assessment framework cannot fully represent the complexity of urban ecological risk.The adaptive cycle model points out that the urban system goes through four stages of reorganization(α),exploitation(R),conservation(k)and release(Ω)cyclically driven by "potential-connectivity-resilience".At present,the model is mostly used to describe the interaction between system and ecological risk,which can help to conceive the complex characteristics of urban ecological risk and guide urban resilience planning strategies.At present,the construction of ecological security pattern is mostly based on land use types and terrain conditions,which is lack of pertinence for ecological risk.It is necessary to put forward more effective spatial optimization strategies to resist ecological risks and delay the risk process.This study takes Beijing social-ecological system as the research object,and introduces adaptive cycle model to optimize the urban ecological risk assessment framework.Based on this framework,this study comprehensively analyzes the spatial distribution,temporal and spatial evolution and risk cycle stages of ecological risk in Beijing from the overall and dynamic perspective.It also provides scientific guidance for the formulation of optimization strategy.The followings are the analysis conclusions of the evaluation results.(1)The spatial patterns of "potential" risk indicators are different due to risk categories,climate conditions and urban development characteristics.The spatial pattern of "connectivity" risk index is related to the landscape spatial pattern and urban expansion pattern of Beijing.The spatial distribution of "resilience" risk indicators shows consistency,which shows a change from high to the highest,and then to low from the central urban area to the mountainous area.(2)The risk of "potential" and "connectivity" decreased from central urban area to ecological area.The "resilience" risk is relatively low in the inner part of the central city,and the high-risk areas are concentrated in the suburban area.It shows that the central urban area begins to pay attention to the ecological environment protection.However,the high-intensity construction of the suburbs leads to the obvious increase of risk.The high-risk areas of "exposure" are concentrated in the central urban area.However,the high-risk areas of "interference" are concentrated in the west and north of the plain area,and the distribution range is larger and more dispersed.This result shows that human activities and climate change have a greater impact on urban system health than other factors.(3)The overall distribution of adaptive ecological risk in Beijing increases first and then decreases from the central urban area to the outside,and the distribution is relatively scattered.By 2035,the highrisk center is moving to the southeast,and the spatial distribution has obvious agglomeration phenomenon.(4)The results of cycle stage are shown below.Yanqing,Huairou,Mentougou,Miyun and Fangshan are in the reorganization stage(α),with the lowest ecological risk.Changping,Daxing,Shunyi and Pinggu are in the exploitation stage(R),and the risk values are increasing.Tongzhou,Chaoyang,Fengtai,Dongcheng,Xicheng,Shijingshan and Haidian are in the Conservation stage(k),and the risk value of "potential" and "connectivity" is the highest,while the risk value of "resilience" shows a downward trend.Based on the results of risk assessment,the research divides the coping strategies into two aspects:improving ecological security to resist risk interference and improving ecological resilience to delay the risk cycle stage.The urban green space is classified into promotion type and protection type based on the risk characteristics assessment.And the hierarchical ecological corridor network is constructed to improve the urban ecological security and enhance the ability of urban green space to resist risks.Based on the identification of risk adaptability cycle stage,this paper puts forward classified resilience promotion strategies according to the stage of district,which can slow down the process of each district development to high-risk stage,enhance urban ecological resilience,and promote the green and sustainable development of Beijing.