Study On The Relationship Of Watershed Ecosystem Services From The Perspective Of Supply And Demand

Ecosystem services(ESs)refer to the resources and utilities provided by the ecosystem to humans.ESs supply and demand link natural ecosystem with human social system together.With the rapid development of society and the increasing of human demands,the conflicts between the supply and demand of ESs have become increasingly prominent,which impacts apparently on regional human well-being and regional sustainable development.The essence is the spatial mismatch or imbalance between the supply and demand of regional ESs.Currently,ESs supply assessment is relatively mature,the study on the demand and the supply-demand of ESs are developing rapidly.Research on the supply and demand pattern and spatial matching of ESs has gradually become the core and highlight for the coordination of sustainable development and ecological protection.In this study,the Bailongjiang watershed in Gansu is selected as a case to show the characteristics of the supply and demand of ESs and build a comprehensive framework for ecological protection and management.Bailongjiang watershed in Gansu(BLJW)is an important ecological function area of water and soil conservation in the upper reaches of Jialingjiang.Recently,due to the strong impact of human activities,frequent natural disasters,ecological sensitivity and vulnerability,the conflict between human and land is deepening,which seriously threaten the ecological security and human well-being of the watershed.Taking the Bailongjiang watershed in Gansu as a case,based on remote sensing images,meteorological and socio-economic statistics data,this study quantitatively evaluates the supply and demand of typical ESs(water yield,soil conservation and food supply)by model simulation,spatial analysis and questionnaire survey.From the comprehensive perspective of supply and demand,we analyzed the trade-offs/synergies between supply and demand sides and the spatial matching between supply and demand of ESs.Then,the management and control countermeasures of watershed based on the supply and demand division of typical ESs were discussed.The main conclusions are as follows:(1)There are obvious spatiotemporal characteristics on supply and demand characteristics of typical ESs in the BLJW.From 2002 to 2018,the total supply and the total demand of water yield increased by 33.72% and 262.17% respectively;the total supply and the total demand of soil conservation increased by 26.10% and 18.70%respectively;the total supply and the total demand of food supply increased by 166.89%and 38.42% respectively.In general,the supply capacity of various ESs in the watershed are mainly affected by factors such as precipitation,vegetation distribution,topographic factors and soil texture form obvious spatial differences.From the perspective of demand,the leading factors of various ESs are different.The demand for soil conservation is affected by rainfall erosion and surface characteristics.There is a high demand in the northwest and southeast,and low demand in the middle parts of the BLJW.The spatial distribution of the demand of water yield and food supply is closely related to the population density,showing the law of high demand in the areas with population aggregation,and low demand in the areas with rare human traces farther away from the central urban area or residential areas.(2)The trade-offs/synergies relationship between supply and demand of typical ESs in the BLJW is as follows: On the supply side,there is a synergistic relationship between the supply pair of water yield-soil conservation;food supply-water yield supply pair,food supply-soil conservation supply pair are trade-offs.From 2002 to2018,the trade-offs intensity of the pair of food supply-soil conservation decreased,while the trade-off intensity of the other two supply pairs increased.On the demand side,there is a trade-off relationship between water yield-soil conservation;there is a significant synergy between water yield-food supply;and there is a trade-off relationship between food supply-soil conservation.From 2002 to 2018,the trade-offs intensity of demand for water yield-soil conservation increased,while that of the other two pairs decreased.(3)From 2002 to 2018,the total amount of water yield,soil conservation and food supply showed a surplus situation.The spatial distribution of the deficit areas(the supply-demand ratio is less than zero)of water yield and food supply are similar.They are mainly distributed in the Zhouqu-Wudu section of the middle reaches of the Bailongjiang and the densely populated area around the administrative center of Diebu;The deficit areas of soil conservation are mainly located in the rocky mountainous areas in northern Diebu.In terms of spatial matching type of supply and demand,the dominant spatial matching type of water yield is high supply with low demand;the dominant spatial matching types of soil conservation were high supply with high demand and low supply with low demand;the dominant spatial matching type of food supply service is low supply with low demand.(4)Based on the clustering analysis of the supply-demand ratio of ESs,the BLJW is divided into sub-regions of urban life development clusters,agricultural production function sub-regions,soil conservation ecological sub-regions,and water conservation ecological sub-regions.Based on this zoning,combined with the characteristics of local ecological environment,population density,the supply-demand relationship and supply-demand risks of ESs in each sub-area,some management suggestions for ecological civilization construction and economic progress were put forward to enhance ESs and the watershed sustainable development in BLJW.