Spatio-temporal Dynamic Evolution Analysis Of Social-Ecological System Coupling And Ecological Risk Assessment—take Tibetan Plateau As An Example

Since the end of the 18th century,when human activities had a global impact on climate and ecosystems,surface ecological processes have gradually been dominated by human behavior,and the Earth has entered a new era of the Anthropocene.As urbanization continues to advance,the development of economy and industry,the exploitation of natural resources and ecological environment also intensifies,and human interference and destruction make the selfregulation and recovery ability of ecosystems continue to decline.How to achieve harmonious coexistence of human and land and sustainable development of human society is a key issue to be solved.Social-Ecological System(SES)coupling mechanism and its interactive stress effect are the frontier of sustainable science research,providing new theoretical basis to better respond to the challenges of the Anthropocene;ecological risk assessment can effectively measure the negative impact of anthropogenic stress or natural disasters on ecosystems,which is an important basis for ecological construction,resource management and decision making at this stage.The results are as follows.(1)The comprehensive evaluation index of social system shows an increasing trend,with a growth rate of 16.46%,and a spatial distribution pattern of "high in the northeast and low in the southwest",with a cumulative decrease of 10.61%in the low level area during the study period,and an increase of 5.09%,2.57%,and 2.96%in the medium,high,and very high levels,respectively,indicating that the social system is in continuous development;the comprehensive evaluation index of the ecosystem shows a distribution pattern of "low in the northwest and high in the southeast",and the low level area is expanding under the influence of industrialization and urbanization and reached the maximum in 2018,accounting for about 64.67%of the total area of the plateau.(2)The time-series change of social-ecological system coupling coordination is relatively stable,but the degree of coordination varies among different scales:the Qinghai-Tibet Plateau as a whole is mildly disordered;at the provincial scale,Tibet has the lowest level of coupling coordination,which is mildly disordered,followed by Sichuan and Qinghai,which are primary coordination,and Gansu,Yunnan and Xinjiang have the highest level,which is moderate coordination;at the county scale,the proportion of severe disordered,moderate disordered and primary coordination decreases by 7.03%,2.63%and 7.20%respectively,while mild disorder and moderate coordination increased by 11.28%and 5.59%respectively,indicating that the degree of coordination kept evolving to higher levels.(3)The scissor difference fluctuates and the difference between the evolutionary trends of the two systems increases.Although the dynamic coupling degree fluctuates,it is distributed in the interval[45°,90°],which corresponds to the common development stage of the dynamic coupling degree model zone Ⅱ,indicating that the development of the social system on the Qinghai-Tibet Plateau is accelerating and the stress on the ecosystem is gradually increasing,and similarly,the constraints and restrictions on the social system after the destruction of the ecosystem are also increasing,and the conflicts between the two are beginning to appear,but not yet prominent.(4)PROB shows an overall distribution pattern of "high in the northwest and low in the southeast",with a high probability of 55.94%,mainly in the high desert areas in the northwest of the plateau,and a low probability of 14.02%,mainly in the forest and grass areas in the southeast of the plateau.LOSS shows a distribution pattern of "low in the north and high in the south",with 30.54%of the loss increasing,mainly in the middle and lower reaches of Yarlung Tsangpo River,and 26.38%of the loss decreasing,concentrated in the northern desertification control area.(5)The ecological risk level is mainly medium-high and high-risk,both of which account for 55.44%of the total plateau area and are mainly distributed in central and northern Tibet,which are facing the problems of land sanding and grassland degradation under the combined effect of strong wind and climate drought,low,medium-low risk areas account for the smallest proportion,about 10.47%,and are mainly distributed in southern Qinghai and northern Sichuan,where the three ecological function areas of Sanjiangyuan wetland,Ruoerge wetland and Sichuan-Yunnan forest are gathered,and the structure and function of the ecological system are more stable.According to the fifth level of ecological risk in the proportion of each urban area to divide the risk control priority area:Naqu,Ali,Rikaze.(6)The results of factor detection show that vfc,ndvi,and et are the top three driving factors,and the explanatory power of vfc on ecological risk is the largest,reaching 0.387;the results of interaction detection show that the explanatory power of both factors interacting with each other increases significantly compared with the single factor effect.The interaction between vfc and slope is the strongest,the explanatory power of vfc alone is 0.387,the explanatory power of slope alone is 0.088,while the explanatory power of the two together reaches 0.658.Geographically weighted regression results show that vfc is the most significant influence on ecological risk among the remaining nine factors after passing the covariance test,and its regression coefficient ranges from-6.191 to 2.654,and the overall effect is mainly negative,the lower the vfc,the higher the probability of occurrence of ecological risk.