| Ecological risk assessment is an important way to protect and monitor the ecological environment.Under the background of ecological civilization construction,where "green water and mountains are golden and silver mountains",regional ecological risk assessment is a necessary measure to balance the contradiction between ecological environment and socioeconomic development,and also a scientific basis for formulating sustainable development policies.As the core area of ecological civilization construction and the responsibility area for carbon peaking and carbon neutrality,the contradiction between economic development and ecological protection is more prominent in urban agglomerations.This paper takes the "XiangShi-Sui-Shen" urban agglomeration as the study area,based on the classical "risk = probability× loss degree"(PI)evaluation model,fully considering the external multi-source stress and internal system loss degree of the "Xiang-Shi-Sui-Shen" urban agglomeration from the three dimensions of nature,humanity,and landscape,and constructs a comprehensive ecological risk assessment system.The temporal and spatial differentiation of ecological risk probability,ecosystem loss,and comprehensive ecological risk in the study area from 2000 to 2020 is studied at the grid scale of 6km × 6km.Finally,the dominant factor method is used to divide the ecological risk control zones and propose corresponding differentiated risk reduction measures to prevent and control the further increase of ecological risks,in order to achieve regional sustainable development.The main research conclusions of this paper are as follows:(1)The ecological risk probabilities of the "Xiang-Shi-Sui-Shen" urban agglomeration in2000,2010,and 2020 were 0.3409,0.3532,and 0.3857,respectively,indicating an overall increase of 8.65%.From a temporal perspective,the ecological risk probabilities within the "Xiang-Shi-Sui-Shen" urban agglomeration between 2000 and 2020 were mainly of low-level ecological risk probabilities of Class I and II,with the proportion of high-level Class V ecological risk probabilities being the smallest.The ecological risk probabilities showed a low level.From a spatial perspective,the spatial distribution of ecological risk probabilities during the study period of the "Xiang-Shi-Sui-Shen" urban agglomeration showed a changing trend of high in the central and northern regions and low in the southwestern region.The proportion of Class II to Class V ecological risk probabilities continued to rise over the 20-year period,and the high-level ecological risk probability zone continued to expand from the central and northern regions to the surrounding areas,while the Class I ecological risk probability was mainly located in the southwestern region,but the proportion of the area decreased to 35.93%in 2020,and the ecological risk probability level tended to increase.As the economic level of the urban agglomeration continues to improve,human activities and development and construction activities continue to encroach on ecological space,and both anthropogenic and natural threats are further increasing,leading to a shift towards higher-level ecological risk probabilities.In the future,appropriate "greening" should be added to the urban land space planning,and the capacity of the city’s ecological environment should be continuously increased to enhance the stability of the ecosystem.(2)The "Xiang-Shi-Sui-Shen" urban agglomeration had ecological system losses of0.5034,0.5261,and 0.5364 in the years 2000,2010,and 2020,respectively,with an overall growth rate of 6.66%.In terms of time,the proportion of level I ecological system losses has consistently been ranked first in terms of area,with losses 3.2-3.8 times higher than those of level V ecological systems,mainly concentrated in the lower-level ecological system loss areas.In terms of space,during the study period of the urban agglomeration,the distribution pattern of ecological system losses showed a high distribution in the north-central and southeastern parts and a low distribution in the southwestern part.During the study period,the proportion of level I-III ecological system losses in the southwestern and northwestern edge mountainous and hilly areas showed a fluctuating decline,with a wide distribution range but a shrinking trend,while the proportion of level IV-V ecological system losses in the central and eastern regions continued to rise,with an increasing distribution area,and the ecological system loss level continued to increase.The disorderly distribution of population and industry in these regions has resulted in poor landscape continuity,and the disturbance of landscape patterns has led to unstable changes in ecological systems,causing various ecological environmental problems,ultimately reducing the value of ecological system services.Moreover,with a higher economic density,the system loss resulting from ecological risks is even higher.In the future,under the premise of economic development,reasonable land use planning should be formulated,fully considering the requirements of ecological environment protection,and arranging land use methods and spatial layout in a reasonable manner.(3)According to the results of the comprehensive ecological risk assessment model,the comprehensive ecological risks of the "Xiang-Shi-Sui-Shen" urban agglomeration in different years were 0.1716,0.1858 and 0.1996 respectively,showing a slight increasing trend overall.In terms of temporal changes,the proportion of low ecological risk has been the highest from2000 to 2020,but it has decreased by 1.90% in the past 20 years,showing a clear corresponding relationship with the continuous increase of high ecological risk.In terms of spatial distribution,the comprehensive ecological risk in the study area is similar to the risk probability and system loss,showing high risk in the central areas such as Fancheng District,Xiangzhou District,and Xiangcheng District,and southeastern areas such as Zengdu District and Guangshui City,and low risk in southwestern areas such as Shennongjia Forestry District,Zhuxi County,and Baokang County.In terms of comprehensive temporal and spatial evolution,the "Xiang-ShiSui-Shen" urban agglomeration has shown a certain degree of degradation trend in the past 20 years,and the ecological risk tends to increase.This is manifested by the increasing frequency of transformation of comprehensive ecological risk levels,with a total area of level changes reaching 10006.36 km2,mainly from low-level ecological risk to high-level ecological risk.The change of comprehensive ecological risk level presents a spatial pattern of "mainly unchanged area,core urban areas rising,and edge mountain areas decreasing".The area of risk level increase continues to expand,and in 2020,its proportion is three times that of the risk level decrease area.(4)According to the high and low combination characteristics of leading factors,"XiangShi-Sui-Shen" urban agglomeration was divided into four risk combination types,namely,early warning and restoration area,ecological restoration area,risk early warning area and natural regulation area,which accounted for 8.87%,15.19%,26.68% and 49.25% of the total area of the study area,respectively.For the risk warning area,it is necessary to recognize the possible damage caused by natural stress and man-made stress risk sources,focus on the implementation of land use policy management,and make land use planning in advance.For ecological restoration areas,it is necessary to recognize the damage degree of comprehensive ecological risk in the region and the main factors of risk increase,and carry out targeted restoration according to the analysis of the main factors.The above two risk prevention strategies should be taken into account in the early warning recovery area.Natural regulation area belongs to the cold spot of risk prevention.It focuses on realizing natural regulation of risk with the help of ecosystem’s own resilience. |
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