| The Karst area in Southwest China is a typical fragile ecological environment area.It is not only the key to maintaining food security,abating land degradation,and building an ecological security barrier in the south of China,but also an important part of China’s national policy of promoting economic development and maintaining ecological stability,exhibiting an irreplaceable ecological and economic status.In the context of decadal developments,the Karst area in Southwest China has been providing human beings with ecosystem services,such as numerous material supply and environmental regulation that are indispensable for survival and development through ecosystems.These services are an important resource source and environmental foundation for improving human well-being,as well as an important cornerstone for achieving regional socio-economic-ecological sustainable development goals.Most of the existing researches on macro-ecosystem services start from the spatiotemporal characteristics of driving factors to analyze the formation mechanism and action mechanism of ecosystem services,but they ignore the direct and indirect effects of supply and demand of ecosystem services and their driving factors,which may affect the integrity and reliability of ecosystem services studies.However,there is currently few research system that quantitatively evaluates the spatial effect of the supply and demand balance of ecosystem services in the context of ecological governance from the perspective of spatial spillovers.Moreover,the current ecological governance projects only discuss the visible positive benefits,but less focus on the potential negative impacts.At the same time,will the supply and demand balance of the ecosystem change with the deepening of ecological engineering?How does the change of the balance between supply and demand of ecosystem services manifest spatial effects?There are no clear answers to these questions.This thesis analyzes the process of land use change in Yunnan Province,Guizhou Province,and Guangxi Autonomous Region in the Karst area in Southwest China under the background of ecological governance from 1980 to 2015,evaluates the quality characteristics of ecosystem services,dynamic changes in supply and demand,and influencing factors before and after the implementation of ecological governance projects,studies the driving mechanism and spatial effect of the evolution of ecosystem services,thus puts forward the optimal regulation strategy of ecosystem.The main findings of this research are as followings:（1）The spatiotemporal pattern of land use from 1980 to 2015 remained stable as a whole,and NDVI gradually improved under the background of ecological governance.The land use in the research area is mainly forest land,grassland and cultivated land,of which forest land accounts for the largest proportion,accounting for more than 50%of the total area.From 1980 to 2015,the area of cultivated land remained stable as a whole,while the area of forest land fluctuated and increased.After 2000,317101.7 hm2 of land was converted into forest land,and the average annual conversion rate was significantly higher than that before 2000.The change in the type of land use is not drastic,and it is mainly the adjustment of space configuration.However,land transfers are frequent,construction land has increased the most,and human activities have a greater impact on the landscape of the research area,and the surrounding urban landscape is gradually becoming fragmented.From 1980 to 2015,NDVI showed a trend of decrease first and then increase either before or after 2000,and the increase rate of NDVI after 2000 was higher than the decrease rate before 2000.The average watershed soil erosion modulus was 19.58 t ha-1 in 1990,22.57 t ha-1 in2000 and 13.96 t ha-1 in 2015,with the same trend as NDVI.The forest resources in traditional forest areas have obvious advantages,but the encroachment of cultivated land by urban expansion should not be ignored.At the same time,the frequent transfer of land,especially in mountainous areas and geologically fragmented areas,will cause potential soil erosion and ecological risks,and form new threats to ecological security.（2）The spatiotemporal pattern of ecosystem services from 1980 to 2015 remained stable as a whole,and ecosystem services gradually improved under the background of ecological governance.After 2000,the NPP growth rate was the largest in eastern Qianzhong,eastern Qiandong and Guizhong Area,with an average annual increase between 0-0.5g C m-2 yr-1.The average value of the ecosystem supply index of the main streams of Beipan River,Yuanjiang River,Hongshui River and Liujiang River increased from 49 to 54,and the southern Yunnan and western Guizhou stabilized above 50.Under the influence of natural environment and social factors,the trade-off relationship between ecosystem service functions at the scale of the study area and county is concentrated between carbon storage and water conservation,and the trade-off conflict is more prominent in areas with better vegetation.Both in 2000 and 2015,the natural environment and socioeconomics were the main drivers of ecosystem services,and population density and economic growth would put enormous pressure on the supply of ecosystem services.Driving factors not only affect the ecosystem services in the observation area,but also affect the spatial effects of ecosystem services in adjacent areas;at the same time,the driving factors in adjacent areas will also react to the observation area in the same way.Due to the hysteresis effect,when the adjacent regional ecosystem services and their driving factors are negative spillovers,it will cause the aggregation effect of ecosystem services,and finally form the impact boundary of ecosystem services.This phenomenon is most obvious in carbon storage,soil conservation and habitat quality.It shows that every 1%increase in population will change the neighborhood carbon storage services,soil conservation services and habitat protection services by 0.805%,-1.205%and 0.00003%respectively.Land use,landscape metrics and socioeconomic factors are the most important influencing factors of these three ecosystem services.（3）The balance of supply and demand of ecosystem services in the research area and the spatial effect of influencing factors have a significant impact,indicating that the past governance measures and development plans are not integrated and systematic enough,which is not conducive to the stable and long-term service function of the ecosystem.Population density,patch number,shape index,connectivity,separation,and dispersion index increased by 1%,causing the ecological supply balance of the neighborhood to decrease by 0.0005%,4.021%,12.030%,2.575%,23.121%,and0.044%,respectively.Highly active social and economic activities and changes in land use patterns have a significant impact on the balance of supply and demand,and at the same time indicate that administrative and geographic boundaries are not sufficient to limit the expansion of the predicament of the imbalance between supply and demand of ecosystem services in a certain region.Urbanization has improved regional economic benefits,but it has also caused a certain range of ecological degradation and an imbalance between supply and demand of ecosystems.The various ecosystem services of cultivated land and construction land with a high degree of land use are lower than those of forest land with a low degree of land use,but this does not mean that there is no limit to increase the area of forest land in order to improve ecological benefits.Overemphasizing ecological benefits and ignoring food security will worsen the potential of regional economic development and fall into a“protection trap”.Although ecological governance projects improve the quality of ecosystem services by interfering with influencing factors,and it needs to be coordinated resources from adjacent regions to promote the overall restoration of the ecosystem in the entire region.（4）Based on the analysis results of the spatial effect of ecosystem services,the future land use simulation model is used to predict the future land use and the spatial distribution of ecosystem service value in the study area under different scenarios.The predicted results show that the past governance measures and development plans are not integrated and systematic enough,which is not conducive to the stable and long-term service function of the ecosystem,indicating that due to the existence of spatial effects,existing governance policies would not be able to maintain a steady increase in the value of ecosystem services over many years.Radical environmental protection scenarios are more conducive to enhancing the value of ecosystem services,but the growth rate of the economy and agricultural products is too slow,falling into a“protection trap”.Therefore,in the future an optimization strategy to improve the service value of the ecosystem is required wherein the expansion of construction land should be restricted in strengthening the overall implementation of ecological protection,and the ecological red line should be delineated in the governance area to carry out regional and step-by-step governance.In the implementation of ecological governance projects and policies,emphasis is placed on the overall governance and system restoration of different zones.Policy makers and executors at all levels need to focus on coordinating the dynamic balance between ecological protection and regional economic development,introduce ecological monitoring mechanisms,and dynamically adjust policy implementation.This study originally incorporated spatial econometrics analysis into the study of ecosystem services,to assess the spatial effect of the supply and demand balance of ecosystem services in the context of ecological governance from the perspective of spatial spillovers,improving the integrity and reliability of investigation of ecosystem services and assessment of ecosystem-governing benefits.Meanwhile,this study at the first time pointed out and described the negative effects of ecological governance,and suggested that the effects on ecosystem services that induced by the spatial effects would cross the restrictions of administrative and geographic boundaries,resulted in ecological overprotection and imbalance between supply and demand that threaten food security and form“protection trap”.Therefore,a strategic early warning that maintaining the balance between ecological governance and socio-economic development and avoiding overprotection was made.The results of this study would be beneficial for enricheing the existing ecosystem service theory,also developing strategies of sustainable ecological governance and achieving regional socio-economic-ecological sustainable development goals. |
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